DE102008016858A1 - Emission control system for internal combustion engine - Google Patents

Abstract

Provided is an exhaust gas purification system for an internal combustion engine, which reduces the estimation frequency of an accumulated amount of particulates and thus the energy consumption, which includes the estimation of the amount. Based on a difference (DeltaP1) between the exhaust pressures before and after a DPF (12) and based on a second accumulated particulate amount (QMP2) estimated based on a temperature rise in temporarily heating the particulates by heating the exhaust gas first map data for estimating a first accumulated particulate amount (QMP1) is corrected based on the difference (DeltaP1) between the pressures before and after the DPF (12) so that an accumulated particulate amount when obtaining the difference (ΔPP1) between the exhaust pressures equals the second accumulated particulate matter (QMP2). This further improves the accuracy of the first accumulated particulate amount (QMP1) estimated by the "first accumulated particulate amount estimation process" which is subsequently performed. As a result, it can be more accurately determined whether the "second accumulated particulate matter estimation process" is to be performed.

Description

The revelation of JP-A-2007-096085 , filed on Apr. 2, 2007, is incorporated herein by reference in its entirety by the specification, drawings and abstract.

The The invention relates to exhaust gas purification systems for internal combustion engines and relates in particular to exhaust gas purification systems that exclude particles Capture exhaust from a diesel engine and capture the particles by burning remove.

conventional appreciates this type of emission control system for an internal combustion engine captured by a particle trapping unit accumulated amount of particles and performs a combustion process by, when the estimated amount is a predetermined value reached.

Examples of such a method include one in which the accumulated particulate amount is estimated based on the difference between exhaust pressures upstream and downstream of the particulate trapping unit (see, for example, US Pat JP-A-2004-340023 ), and one in which it is estimated on the basis of a temperature rise as a result of the temporary heating of accumulated particles (see, for example, US Pat JP-A-2005-226547 ).

Indeed suffer the conventional emission control systems for Internal combustion engines under the problems described below. In the former method, accumulated particles may become burnt or not burned, indicating the temperature or flow rate depends on exhaust gas that has undergone the combustion process becomes. After repeated repetition of the combustion process can the pressure difference will vary, even if the accumulated amount of particles is equal to. This makes it difficult to accumulate the accumulated amount of particles to estimate exactly on the basis of the pressure difference.

Also if in the latter method the accumulated amount of particles be estimated with reasonable accuracy can, an exhaust gas temperature rise is controlled by post-injection (i.e., injection after the main injection for each Combustion; in addition to the regular fuel injection is carried out. This energy is always consumed, when an accumulated amount of particles is estimated. Consequently increased a frequent estimate of the accumulated amount of particulates the energy consumption.

The Invention came in the face of the previously discussed problems of the known ones Technology. It is therefore an object of the invention to an emission control system for an internal combustion engine be provided, wherein the cleaning system is designed so that they the estimated frequency of accumulated particulate matter reduces, which reduces the energy consumption, the Estimation includes. This task comes with the features the claims solved.

Becomes According to the invention, the second accumulated amount of particles based on a temperature increase during temporary heating of the particles are estimated, the first map data for Estimate the accumulated amount of particulates based on the difference between the exhaust pressures before and after Particle trapping unit according to the difference between the exhaust pressures upstream and downstream from the particle trapping unit and according to the estimated second accumulated amount of particles corrected. In other words, guaranteed the use of the first map data and the difference between the exhaust pressures upstream and downstream from the particle capture unit, a more accurate estimate the first accumulated amount of particles in the subsequent estimation. Consequently, a comparison between the first accumulated allows Particle amount estimated using the first map data is determined, and a predetermined threshold, to determine correctly whether the second accumulated particulate amount based on the increase the temperature during the temporary heating of the accumulated particles is appreciated. This reduces the estimation frequency the second accumulated amount of particulates and thus the energy consumption, which includes the estimation of the second set.

Becomes in the emission control system according to the invention a second accumulated amount of particles to be heated temporarily estimated, first map data becomes estimating a first accumulated. Particle quantity based on the difference between the exhaust pressures before and after the particle capture unit corrected to eliminate any estimation error. A comparison between the first accumulated amount of particles with Help the corrected first map data is estimated and a threshold allows to correctly determine whether the second accumulated amount of particulates based on a Rise in temperature during temporary heating of the To estimate the accumulation of particles. This reduces the estimated frequency of a second accumulated Particle quantity and thus the energy consumption, this estimate the second set includes.

Based The attached drawings will become a preferred embodiment an emission control system according to the invention described for an internal combustion engine.

1 shows the configuration of an exhaust gas purification system for an internal combustion engine, in which the invention is applied;

2 FIG. 10 is a flowchart of a method of estimating the accumulated particulate amount performed in an ECU; FIG.

3 shows first map data representing the correlation between a pressure difference ΔP and the accumulated particulate amount;

4 Fig. 12 is a diagram of the correlation between a rise in the temperature of the DPF and the accumulated amount of particulates; and

5 FIG. 12 shows second map data representing the correlation between an increase in the temperature of the DPF and the accumulated particulate amount.

1 shows the configuration of an exhaust gas purification system for an internal combustion engine, in which the invention is applied.

Based on 1 First, the configuration of the exhaust gas purification system for an internal combustion engine will be described.

An emission control system 10 for an internal combustion engine indicates: a diesel engine 11 for use as an internal combustion engine; a diesel particulate filter 12 ; a first exhaust pressure sensor 13 and a second exhaust pressure sensor 14 ; an exhaust gas temperature sensor 15 ; a heater; and an ESG (electronic control unit) 16 that serves as a controller.

In particular, the diesel engine 11 a motor, under the control of the ESG 16 Fuel is injected into compressed air in the engine combustion chamber and then ignited and burned, generating power. A microprocessor (MPU) in the ESG 16 calculates an appropriate amount of fuel to be injected by comparing the degree of depression of the accelerator pedal, the engine speed, and many additional correction coefficients with characteristic map data stored in a memory. The gas burned in the combustion chamber is discharged from the engine as exhaust gas.

The diesel particulate filter (hereinafter referred to as "DPF") 12 traps soot particles (hereinafter called "particles") in the exhaust of the diesel engine 11 with the help of a filter, the z. B. is made of ceramic fibers (Siliciumcarbidmonolith); Then, if the accumulated particulate reaches a predetermined amount, it raises the exhaust gas temperature by means of a heating unit under control of the ECU 16 and burns and removes the particles by the reaction of a catalyst held by the filter; and regenerate the filter. The amount of particulates accumulated in the filter is through the ESG 16 appreciated, which will be described later.

The first exhaust pressure sensor 13 detects the exhaust pressure before the exhaust gas reaches the DPF 12 passes through (ie the exhaust pressure upstream of the DPF 12 ). Similarly, the sensor detects 14 the exhaust pressure after the exhaust gas the DPF 12 passes through (ie the exhaust pressure downstream of the DPF 12 ). The through the first and second exhaust pressure sensor 13 and 14 detected values are in the ESG 16 entered and used to estimate the accumulated amount of particles. What is needed is such a detection, as with the increase by the DPF 12 the amount of particulate matter trapped before and after passing through the DPF 12 increases.

Instead of the first and second exhaust pressure sensor 13 and 14 For example, an exhaust pressure differential sensor may be used that measures any difference in exhaust pressure before and after passing through the DPF 12 detected.

The exhaust gas temperature sensor 15 is downstream of the DPF 12 arranged and detects the temperature TAFT of exhaust gas, which is the DPF 12 has gone through. The through the exhaust gas temperature sensor 15 detected value is in the ESG 16 entered and used to estimate the accumulated particulate matter to the temperature for regeneration of the DPF 12 to control (thus an excessive temperature rise of the DPF 12 is prevented, which leads to impairment of the catalyst), as well as for other such purposes.

Under the control of the ESG 16 the heating unit increases the temperature of exhaust gas in the DPF 12 flows, by heating the exhaust gas. Specifically, a fuel injection control is performed so that a post-injection takes place in addition to a regular fuel injection (ie, an injection after the main injection has been made for each combustion). The heating unit is not limited to one designed specifically for fuel injection control, but may be any electric heater that is in close contact with the filter of the DPF 12 is arranged.

The ESG 16 is formed from a circuit comprising a microprocessor operated by a computer program used for fuel injection control, accumulated particulate matter estimation and particulate combustion. In particular, the ESG compares 16 the degree of depression of the accelerator pedal, the engine speed and many additional correction coefficients with characteristic map data stored in a Spei are stored (not shown), then calculates an appropriate amount for injection and performs the injection.

Based on a plurality of map data (ie, a numeric value table) stored in memory, values provided by the first and second exhaust pressure sensors 13 and 14 be detected, as well as by the exhaust gas temperature sensor 15 be detected, the ESG estimates 16 also the accumulated amount of particles.

Furthermore, the ESG exercises 16 a temperature control such that when the accumulated particulate amount (hereinafter referred to as second accumulated particulate amount QPM2) reaches a predetermined value (threshold), the temperature of exhaust gas containing the DPF 12 passes through, with the help of the heating unit is heated, in the DPF 12 accumulated particles are burned and the DPF 12 thus regenerated.

Based on 2 to 5 Next, a method of estimating the accumulated amount of particulates contained in the ECU is described 16 is carried out.

2 FIG. 13 is a flowchart of a method of estimating the accumulated particulate amount. FIG. 3 FIG. 12 shows first map data representing the correlation between a pressure difference ΔP and the accumulated particulate amount. 4 Figure 11 is a graph of the correlation between a rise in the temperature of the DPF and the accumulated amount of particulates. 5 FIG. 12 shows second map data representing the correlation between an increase in the temperature of the DPF and the accumulated particulate amount.

First, the ESG begins 16 in step S1 with the reading of the exhaust gas pressure P1 upstream of the DPF 12 by the first exhaust pressure sensor 13 is detected, and the exhaust gas pressure P2 downstream of the DPF 12 passing through the second exhaust gas sensor 14 is detected.

In step S2, the ESG calculates 16 on the basis of the thus read in exhaust pressures P1 and P2, the difference ΔP1 between the exhaust pressure upstream of the DPF 12 and downstream of the DPF 12 based on ΔP = | P2 - P1 |.

In step S3, the ESG initiates 16 the "estimation process of a first accumulated particulate matter" based on that in step 2 calculated pressure difference .DELTA.P1 and the first map data stored in the memory, a first accumulated particulate amount QPM1 is estimated. The "first particulate accumulated amount estimating operation" is performed at predetermined intervals.

According to 3 The first map data on a line L1 (ALT) represents the correlation between the accumulated particulate amount in the DPF12 and the difference ΔP between the exhaust pressures upstream and downstream of the DPF 12 , The first accumulated particle quantity QPM1 in the DPF 12 is calculated by calculating the difference ΔP1 between the exhaust pressures upstream and downstream of the DPF 12 estimated.

The accumulated particulate amount QPM1 represents an accumulated particulate amount (g) per geometric surface area of 1 m ² , assuming that the surface of the cell dividing wall of the filter is smooth (ie, a geometric surface).

in the Step S4, the ECU compares a preset threshold with the first accumulated particle quantity QPM1, which with the help of first map data is estimated, and then determines whether the "estimation of a second accumulated particulate matter" to initiate at which a second accumulated amount of particulates QPM2 based on the increase in temperature at temporary Heating the accumulated particles is estimated becomes.

Becomes determines that the first accumulated particulate amount QPM1 has not reached the threshold value (i.e. that the amount of particles is not so large, so that the Combustion process is unnecessary), the process returns to Step S1 back.

Becomes on the other hand determines that the first accumulated amount of particles QPM1 has reached the threshold (i.e., a determination that the accumulated particles must be burned), that drives Proceeding to the step S5, the "estimation process the second accumulated particulate matter ", wherein the accumulated particulate amount QPM2 is based on a temperature rise during temporary heating of the accumulated particles becomes.

When Next, the "estimation process of a second accumulated amount of particulate "described in which the accumulated Particle quantity based on the temperature increase during the temporary Heating the particles is estimated.

Upon initiation of the post-injection control, a predetermined unburned amount of fuel is supplied to the exhaust gas. As the on the DPF 12 held catalyst reaction heat generated, the temperature of the exhaust gas increases. As a result, the exhaust temperature TAFT decreases downstream of the DPF 12 also to. Is in this case the accumulated Teilchenmen Small, so is the heat capacity of the DPF 12 small, which is why the exhaust temperature TAFT rises relatively steeply, which is the line L3 in 4 shows. If the accumulated amount of particulates is large, the heat capacity also increases, which is why the exhaust gas temperature TAFT moderately increases, which the line L4 in 4 shows. The reference numerals α1 and α2 respectively correspond to the temperature rise degree for each fixed time unit, in other words, the speed at which the temperature increases.

Consequently can be a substantially accurate estimate obtained by taking the accumulated amount of particles on the basis map data (i.e., the second map data described above) is estimated which are experimentally created and stored in memory. The map data represents the correlation between the accumulated particulate amount and the temperature increase of the exhaust gas temperature TAFT after the lapse of a fixed time t from the initiation of the post-injection control.

More specifically, in step S6, the temperature rise of the exhaust gas temperature TAFT after elapse of the fixed time t from the initiation of the post injection control is calculated on the basis of the value obtained by the exhaust gas temperature sensor 15 is detected; and in step S7, the second accumulated particulate amount QPM2 is calculated on the basis of the calculated value (ie, the temperature rise of the exhaust gas temperature TAFT) and based on the second map data 5 estimated.

In step S8, the ESG corrects 16 on the basis of the pressure difference ΔP1 and the second accumulated particulate amount QPM2, the gradient of the line L1 (ALT) of the first map data according to FIG 3 and stores it in memory as a new line L1 (NEW). Thereafter, the process returns to step S1.

different the first accumulated particulate amount QPM1 accumulated from the second Particle quantity QPM2, performs an estimation of the accumulated Particle quantity using the line L1 (ALT) of the first map data to an error in the calculation of a value (i.e., the first accumulated particulate amount QPM1). To eliminate this error, the gradient of the line L1 (ALT) must be in accordance with the Pressure difference ΔP1 and the second accumulated particulate amount QPM2 be corrected. In particular, the gradient of the line L1 (ALT) corrected so that the accumulated amount of particles in the calculation of the pressure difference ΔP1 equal to the second accumulated particulate amount is QPM2. The new line L1 (NEW) serving corrected line is stored in memory (updated or overwritten).

If the gradient of the new line L1 (NEW) exceeds the threshold, the ESG determines 16 in that malfunctions in the first and second exhaust pressure sensor 13 and 14 or in the exhaust gas temperature sensor 15 occurred, and the previous line L1 (ALT) is stored unchanged in memory.

In the above-described exhaust gas purifying apparatus for an internal combustion engine according to the present invention, the line L1 (ALT) of the first map data for the "first accumulated particulate amount estimation process" is performed after performing the "second particulate matter accumulated estimation process" according to the difference ΔP1 between the exhaust pressures upstream and downstream DPF 12 and corrected according to the second accumulated particulate amount QPM2 calculated by the "second accumulated particulate accumulation estimation process". This further improves the accuracy of the first accumulated particulate amount QPM1 estimated by the "accumulated first particulate amount estimation process" which is subsequently performed. Therefore, comparison of the first accumulated particulate amount estimated using the first map data (NEW version) with the predetermined threshold value makes it possible to more accurately determine whether to estimate the second accumulated particulate amount based on a temperature rise in temporarily heating the accumulated particulate matter is. This reduces the frequency of estimation (energy consumed) of the second accumulated particulate matter. Thus, an internal combustion engine can be provided with an exhaust gas purification system that consumes less energy.

QUOTES INCLUDE IN THE DESCRIPTION

This list The documents listed by the applicant have been automated generated and is solely for better information recorded by the reader. The list is not part of the German Patent or utility model application. The DPMA takes over no liability for any errors or omissions.

Cited patent literature

• - JP 2007-096085 A [0001]
• - JP 2004-340023 A [0004]
• JP 2005-226547 A [0004]

Claims (1)

Emission control system for an internal combustion engine, the cleaning system comprising: a particle capture unit, captures the particulates from exhaust gas from the internal combustion engine; a Exhaust pressure difference detection unit, which is the exhaust pressure difference detected between a location before and after the particle trapping unit; a Exhaust gas temperature detection unit, which the exhaust gas temperature downstream detected by the particle capture unit; a heating unit, the temperature of the particle trapping unit passing through Exhaust gas increased by its warming; and a Control unit that estimates the accumulated amount of particles captured by the particle trapping unit and the heating unit controls wherein the control unit is a first accumulated amount of particulates based on the difference between the exhaust pressures before and after the Partikeleinfangeinheit estimates, wherein the difference using values provided by the exhaust pressure detection unit are detected and calculated based on first map data which are stored in advance in a memory, wherein the map data the correlation between the accumulated amount of particles in the Partikeleinfangeinheit and the difference between the exhaust pressures before and after the particulate trapping unit; if the first one accumulated amount of particles has reached a threshold, the control unit the heating unit causes the particle trapping unit continuous exhaust gas with a predetermined heat capacity to heat temporarily, and also a second accumulated Particle amount based on a by the exhaust gas temperature detection unit detected temperature rise and based on second map data which are stored in memory in advance, wherein the map data the correlation between the temperature rise upon heating of the exhaust gas with the predetermined heat capacity and the accumulated amount of particulates in the particulate trapping unit group; and based on the second accumulated particulate amount and on the basis of the exhaust pressure difference detection unit Detected difference between the exhaust pressures, the control unit the first map data corrects the correlation between the accumulated particulate matter and the difference between the exhaust pressures represent.