KR100590936B1 - The regeneration strategy of catalyzed particulate filter - Google Patents

Abstract

The present invention relates to a method for regenerating a catalyst-coated soot filter, and to apply a different regeneration map (logic) according to different engine regions, that is, logic that can regenerate the catalyst-coated filter most efficiently. It is intended to provide the regeneration logic to obtain the same optimum regeneration result even when operating in different engine zones.It is divided into low speed low load, medium speed medium low load, high speed low load, medium speed medium load, low speed high load area by engine operation area. The present invention provides a method for regenerating a catalyst-coated soot filter that maintains an exhaust gas temperature of 600 ° C. and an oxygen concentration of 5 to 8%, which is optimal for each region, and obtains an optimum regeneration result.

Catalyst Coated Soot Filter, Regeneration, Engine Area

Description

The regeneration strategy of catalyzed particulate filter             

1 is a flowchart illustrating a regeneration method of a soot filter coated with a catalyst according to the present invention;

2 is a schematic diagram showing the basic structure of an ECU used for diesel soot and filter regeneration.

The present invention relates to a method for regenerating a catalyst-coated soot filter, and more particularly, to a diesel engine exhaust system system using a diesel particulate filter (DPF) system. The present invention relates to a method of regenerating a catalyst-coated soot filter, by applying a different regeneration map (logic) according to a region, so as to optimally regenerate the catalyst-coated soot filter.

In general, exhaust gas emitted from a vehicle refers to a gas in which a mixer combusted from an engine is released into the atmosphere through an exhaust pipe, and such exhaust gas mainly includes carbon monoxide (CO), nitrogen oxides (NOx), and unburned hydrocarbons (HC). Contains hazardous substances.

Such exhaust gas regulation is inevitably tightened. Accordingly, an exhaust gas control device including an exhaust gas recirculation device, a three-way catalyst, an MPI device, and an evaporative gas control device including a canister and a purge control solenoid valve The back is applied to a vehicle.

Unlike gasoline engines, diesel engine vehicles have a high amount of nitrogen oxides (NOx, NOx) and particulate matter (PM) in spite of their excellent fuel economy and output.

In diesel vehicles, CO and HC are emitted much less than gasoline vehicles because air is sufficiently burned in most operating conditions, but the above-mentioned NOx and particulate matter (soot) are emitted.

Diesel Particulate Filter (DPF) technology has been adopted as a method of reducing the particulate matter (PM), which has recently emerged. This diesel particulate filter is installed in an exhaust line and discharged from the engine. The diesel particulate matter is collected using a trap, and the function of burning (regenerating) the particulate matter is repeatedly performed by raising the temperature above the ignition temperature of the particulate matter.

The emission reduction technology of diesel vehicles focuses on the reduction of particulate matter including NOx and soot.In particular, in response to tightening emission standards of diesel vehicles, particulate matter such as smoke, CO, HC, etc. are reduced by post-treatment technology. The DPF has already been put into practical use. In addition, a diesel oxidation catalyst (DOC) has been developed, and a De-NOx catalyst and SCR have been developed to selectively reduce only NOx.

At this time, the temperature at which the particulate matter trapped in the diesel particulate filter is combusted is 550 ~ 600 ℃ or more, but the temperature of the exhaust gas discharged due to the characteristics of the diesel engine is generally low to 200 ~ 300 ℃ is collected in the filter Particulate matter can not be burned.

Therefore, in order to increase the temperature of the exhaust gas discharged from the diesel engine, various techniques such as post injection, exhaust gas raising method using an oxidation catalyst, fuel additive injection, and the like have been developed.

Regulations on current and future emissions are being tightened to significantly reduce these emissions, but NOx and PM are inversely related to each other, so reducing NOx increases PM and, on the contrary, NOx increases.

In particular, as a method of reducing PM in recent years, DPF is one of the most popular technologies. DPF is a system that physically collects PM discharged from diesel engines in the filter and then removes the PM by raising the temperature above a certain temperature.

However, the temperature at which the PM trapped in the filter is combusted is higher than 550 to 600 ° C. However, due to the characteristics of diesel engines, the temperature of the exhaust gas discharged is generally low at 200 to 300 ° C. Temperature too low to be.

Therefore, many technologies are being developed to increase the temperature of the exhaust gas discharged from the diesel engine, and in particular, many technologies are being developed such as post injection, rise of exhaust gas using an oxidation catalyst, and fuel additive injection.

The system currently being developed simply measures the pressure difference between the front and rear of the filter, and regenerates the filter using only the temperature rise of the exhaust gas when the pressure exceeds the predetermined pressure.

Thus, the present invention was developed in view of the above, by applying the logic to the most efficient regeneration of the catalyst-coated filter, that is, different reproduction maps (logic) according to different engine regions, It is intended to provide the regeneration logic to obtain the same optimum regeneration result even when operating in different engine zones.It is divided into low speed low load, medium speed medium low load, high speed low load, medium speed medium load, low speed high load area by engine operation area. The present invention provides a method for regenerating a catalyst-coated soot filter that maintains an exhaust gas temperature of 600 ° C and an oxygen concentration of 5 to 8%, which are optimal regeneration conditions, and achieves optimum regeneration results. have.

The present invention for achieving the above object comprises the steps of sensing the RPM and the accelerator opening of the engine; Calculating RPM and BMEP values by the ECU; Determining an engine operating region according to the RPM and BMEP values at the time of regeneration of the catalyst-coated soot filter; Turning off the EGR for the entire engine operation area; Depending on the engine low load, high speed low load, low speed high load, medium speed low heavy load, medium speed high load, fuel injection delay or post-injection is performed to regenerate the catalyst filter soot filter appropriately for the area. Steps; It provides a method for regenerating the catalyst-coated soot filter characterized in that the step consisting of turning on the EGR after the regeneration.

As a first preferred embodiment, after the injection of the fuel injection is delayed by about 10 to 12 degrees in the low speed low load region (2000 rpm, BMEP 3 bar or less) of the engine, the after-fuel injection consists of 10 to 12 mg / str. It is done.

At this time, after the post-injection of the fuel in the low speed low load region of the engine, the step of increasing the temperature of the exhaust gas while reducing the amount of air by adjusting the intake throttle valve is further characterized.

As a second preferred embodiment, after the injection of fuel injection is delayed by about 10 to 12 degrees in the high speed low load region (3500 rpm, BMEP 3 bar or less), the after-fuel injection is 8 to 10 mg / str. It is done.

At this time, after the post-injection of the fuel in the high speed low load region of the engine, the boost pressure is reduced to maintain the oxygen concentration of 10% or less, preferably 5 to 8%, and the boost pressure is reduced, thereby reducing the temperature of the exhaust gas. It is characterized in that the step of increasing further proceeds.

As a third preferred embodiment, after the injection of the fuel in the low speed high load region (2000rpm, BMEP 12bar or less region) of 2 ~ 4mg / str, the step of increasing the amount of air by increasing the boost pressure is characterized in that the progress It is done.

As a fourth preferred embodiment, the fuel injection is delayed by about 6 to 8 degrees in the medium-speed low-load region (1000 to 3,500 rpm, BMEP 6 bar or less), and then 6 to 8 mg / str. Characterized in that made.

As a fifth preferred embodiment, after the fuel injection injection is delayed by about 2 to 4 degrees in the medium speed high load region (1000 to 4000 rpm, BMEP 6 bar or more), the after-fuel injection consists of 2 to 4 mg / str. It is characterized by.

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

1 is a basic structure of an ECU currently used for regeneration of a diesel particulate filter.

The ECU accepts the vehicle's RPM and Axel opening, and outputs the vehicle's torque according to the RPM and Axel opening according to the already created driving map, and the output from this is calculated as fuel amount in the torque converter.

That is, the torque converter (FMTC) prepares a relationship between the engine RPM and the fuel amount according to the torque, and the measured fuel amount is used for the engine mapping, and all maps used for the engine mapping are based on the engine RPM and the fuel amount. do.

Accordingly, the ECU controls fuel such as main injection timing, after-injection, rail pressure, and air volume control such as boost pressure, EGR, and variable swirl according to engine RPM and fuel amount.

The present invention uses the ECU's logic map to use the main injection retard and the post-injection injection together for each engine region, and in some regions, it is possible to adjust the boost pressure to achieve optimum regeneration conditions. It is to achieve.

Here, the regeneration method of the soot filter coated with the catalyst of the present invention will be described.

2 is a flowchart illustrating a regeneration logic according to the present invention.

First, in the regeneration method of the present invention, the RPM and the accelerator opening degree of the engine are detected, and the RPM and BMEP values are calculated by the ECU.

While the vehicle is running, the ECU continuously receives the RPM and the accelerator opening value of the vehicle. The RPM and the accelerator opening transmitted to the ECU are converted into torque by the driving map, and the torque is converted into fuel by the torque converter (FMTC). All maps are freely controlled, and BMEP (Brake Mean Effective Pressure) value is calculated in this process.

Next, at the time of regenerating the catalyst-coated soot filter, determining the engine operating region according to the RPM and the BMEP value, and turning off the EGR for the entire engine operating region.

As the vehicle continues to run, it is determined whether it is regeneration time, and when the regeneration time is determined, the area in which the engine is driven is determined according to RPM and BMEP.

In particular, since the driving conditions in the vehicle change from time to time, it is very important to determine the driving region. When the driving region according to the RPM and the BMEP is determined, the EGR is first turned off for the entire driving region.

In the case of the EGR, it is very effective to raise the temperature of the exhaust gas, but on the other hand, it is very important to turn off the EGR in order to secure an appropriate oxygen concentration since the oxygen concentration is rapidly lowered.

Next, the injection of fuel injection delay (= main injection timing delay) or the post-fuel injection is performed according to the conditions of low speed low load, high speed low load, low speed high load, medium speed low heavy load, and medium speed high load of the engine. One step is performed to regenerate the coated soot filter.

That is, it is determined whether it is included in five driving regions according to the engine driving region, and reproduction is performed according to the reproduction map included in the driving region.

First, when the engine is operated in the low speed low load area (2000 rpm, BMEP 3 bar or less), it enters the first regeneration map, and the main injection timing retard is about 10-12 degrees. The post-fuel injection is 10-12 mg / str.

At this time, by adjusting the intake throttle (Intake throttle) to reduce the amount of air slightly to help increase the exhaust gas temperature.

Secondly, when the engine operation zone enters the high speed low load region (3500rpm or more, BMEP 3bar or less), the fuel injection delay is delayed by about 10 to 12 degrees. Done.

In particular, the oxygen concentration is very rich in more than 13% in the above conditions, rather, the excessive combustion in the regeneration excessive oxygen concentration may cause the filter to break, reducing the boost pressure to maintain the oxygen concentration below 10%, In addition, the temperature of the exhaust gas is increased by reducing the boost pressure.

Thirdly, it is a low-speed, high load region (2000 rpm, BMEP 12 bar or less), and under this condition, the exhaust gas temperature is high, and the after-fuel injection amount may be injected as small as 2 to 4 mg / str. In this condition, the oxygen concentration is very low, so the boost pressure By increasing the amount of air to increase the oxygen concentration is secured.

Fourthly, as a medium speed low heavy load region (1000 to 3500 rpm, a BMEP 6 bar or less region), in this condition, fuel injection injection is delayed by about 6 to 8 degrees, resulting in a fuel injection of 6 to 8 mg / str.

Finally, in the medium speed high load region (1000 to 4000 rpm, BMEP 6 bar or more), in this condition, fuel injection delay is delayed by about 2 to 4 degrees, thereby resulting in 2 to 4 mg / str fuel injection.

At this time, there is an overlapping part among the above five areas, and it is preferable to set the priority. The low speed low load area is 1, the high speed low load area is 2, the low speed high load area is 3, and the medium speed low is When the load area is set at 4 and the medium speed high load area is set at 5, the overlapping portion occurs, so that the reproduction map is determined according to the area corresponding to the priority.

After the regeneration is completed, the ECU determines whether the regeneration is completed, and when the regeneration is completed, switches back to the original map, and turns on the EGR again.

 As described above, according to the regeneration method of the catalyst-coated soot filter according to the present invention, different regeneration mapping is operated and regenerated according to each engine operating region, thereby enabling accurate control and precise regeneration of the soot filter. Can be.

In addition, there is an advantage that can maintain the optimum fuel economy while maintaining the same output of the vehicle and preventing damage to the filter through maintaining the appropriate exhaust gas temperature and oxygen concentration.

Claims (8)

Detecting RPM and axel opening of the engine; Calculating RPM and BMEP values by the ECU; Determining an engine operating area according to the RPM and BMEP values at the time of regeneration of the catalyst-coated soot filter; Turning off the EGR for the entire engine operation area; Depending on the engine low load, high speed low load, low speed high load, medium speed low heavy load, medium speed high load, fuel injection delay or post-injection is performed to regenerate the catalyst filter soot filter appropriately for the area. Steps; Regeneration method of the catalyst-coated soot filter characterized in that it comprises the step of turning on the EGR after the regeneration. The catalyst according to claim 1, wherein after the fuel injection injection is delayed by 10 to 12 degrees in the low speed low load region (2000 rpm, BMEP 3 bar or less) of the engine, the catalyst is composed of 10 to 12 mg / str. Regeneration method of coated soot filter. The catalyst according to claim 1 or 2, wherein after the fuel injection is performed in the low speed low load region of the engine, the step of increasing the temperature of the exhaust gas while reducing the amount of air by adjusting the intake throttle valve is further performed. Regeneration method of the coated soot filter. The catalyst according to claim 1, wherein after the fuel injection injection is delayed by 10 to 12 degrees in the high speed low load region (3500 rpm, BMEP 3 bar or less) of the engine, the fuel post injection is 8 to 10 mg / str. Regeneration method of coated soot filter. The fuel gas temperature of claim 1 or 3, wherein after the fuel injection is performed in the high speed low load region of the engine, the temperature of the exhaust gas is increased by reducing the boost pressure to maintain the oxygen concentration at 5 to 8% and reducing the boost pressure. Regeneration method of the catalyst-coated soot filter characterized in that the further step of making. The method of claim 1, wherein after the fuel injection is 2 to 4 mg / str in the low speed and high load region (2000 rpm, BMEP 12 bar or less) of the engine, the step of increasing the air volume by increasing the boost pressure is characterized in that it is carried out. Regeneration method of a soot filter coated with a catalyst. The method of claim 1, wherein after the fuel injection delay is made 6 to 8 degrees in the medium speed low-load region (1000 to 3500 rpm, BMEP 6 bar or less), the after-fuel injection is 6 to 8 mg / str. Regeneration method of a soot filter coated with a catalyst. The method of claim 1, wherein after the fuel injection injection is delayed by 2 to 4 degrees in the medium speed high load region (1000 to 4000 rpm, BMEP 6 bar or more region), the after-fuel injection is 2 to 4 mg / str. Regeneration method of catalyst coated soot filter.

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