JP2006515910A - Exhaust gas purification equipment for internal combustion engines - Google Patents

Abstract

A first exhaust pipe (3) having a first catalytic purification device (4) and a second exhaust pipe (3 ') having a second catalytic purification device (4'); And the second exhaust pipe are guided to one common exhaust pipe (6) downstream of the first and second catalytic purification devices (4, 4 '), and each catalytic purification device (4, 4' ), One first sensor (7, 7 ') is provided, and this first sensor is provided in each exhaust pipe (3, 3') upstream of each catalytic purifier. In the exhaust gas purification equipment (1) for an internal combustion engine (2) equipped with the NOx absorber, the catalytic purification device (4, 4 ') is a NOx absorber, and at least the regeneration of the catalytic purification device (4, 4'). A common third sensor (8) is provided in the common exhaust pipe (6). The proposed exhaust purification facility requires only three sensors to regenerate the NOx absorber in conjunction with the proposed method for regenerating the NOx absorber.

Description

  The invention relates to an exhaust gas purification facility for an internal combustion engine according to the features of the premise part of claim 1 and a method for regenerating the first and second catalysts of the exhaust gas purification equipment according to the feature of the premise part of claims 6 and 8. About.

  The present invention starts from Patent Document 1. This patent document describes a double-flow exhaust system for a multi-cylinder internal combustion engine for automobiles having two exhaust lines. Each exhaust line is connected to one or more cylinders. Each exhaust line is provided with a catalyst provided with one sensor upstream and downstream. Downstream of the sensor, the two exhaust lines are guided by a common exhaust pipe. A NOx absorber is incorporated in the common exhaust pipe. Behind the NOx absorber, other sensors are integrated into a common exhaust pipe. Furthermore, a method for controlling the regenerated fuel is described. This regenerated fuel is supplied to an internal combustion engine operating with a lean fuel-air-air mixture. The purpose of this method is to achieve optimal emission control with minimal fuel consumption. In order to detect when the fuel-air-air mixture for an internal combustion engine is in an excessively lean or rich range, the method monitors the exhaust gas exiting from the NOx absorber during regeneration. If the detected exhaust contains an excessively lean fuel-air-air mixture, the amount of fuel for the internal combustion engine is increased. If the detected exhaust contains an excessively rich fuel-air-air mixture, the amount of fuel is reduced. By adjusting the regeneration time or the fuel-air ratio, the amount of fuel is increased or decreased.

  In the case of the above-described structure of the exhaust purification equipment, there is a drawback that all the cylinders of the internal combustion engine must be operated with a rich air-fuel mixture when the NOx absorber is regenerated.

German Patent Application Publication No. 10012839

  It is an object of the present invention to provide an exhaust purification facility that can be selected for each cylinder group to regenerate a NOx absorber and at the same time minimize the number of required sensors.

This problem is solved by the features of claim 1.
With the structure of the exhaust purification system according to the present invention, it is possible to regenerate the NOx absorber selectively for each cylinder group. Furthermore, the required number of sensors required for regeneration of the NOx absorber is minimal. Furthermore, placing the NOx absorber close to the engine will start up quickly and thus store toxic substances quickly after a cold start of the internal combustion engine.

  In claims 2 and 3, a low-cost identical component principle for the sensor is used. In this case, depending on the formation of the sensor, i.e. NOx sensor or O2 sensor, i.e. linear or step response formation, an optimal desulfation scheme, i.e. regeneration of the NOx absorber, is possible.

  According to claim 4, it is advantageous to include desulfation of the NOx absorber together with the control strategy of the control equipment, since control by the control equipment is common for modern internal combustion engines. This integration saves separate control equipment or components, thus reducing manufacturing costs.

  According to claim 5, it is advantageous to incorporate another catalytic purification device into the exhaust purification device, since the NOx absorber cannot remove all harmful substances from the exhaust. In this case, the other catalytic purification device is a three-way catalyst.

  The regeneration method of the NOx absorber according to claim 6 is particularly advantageous in that the control method is simple. As in the case of Patent Document 1, the entire internal combustion engine is operated uniformly with the same fuel-air-air mixture, but only three sensors are required to control regeneration. The same regeneration start applies for all cylinder groups. In this case, the reproduction time is detected by a linear sensor via a sensor signal. The regeneration cycle is terminated when the measured exhaust component, e.g. O2 or NOx, approaches the limit value or when the exhaust component matches for all three sensors within acceptable limits.

  In the case of the regeneration method of the NOx absorber according to claims 8 and 9, control is performed by selecting for each cylinder group, thereby detecting the load state of each NOx absorber and selecting and controlling for each catalyst. It can be carried out. When this method is used, the amount of residual harmful substances is further reduced compared to the methods of claims 6 and 7. This is because fuel-air-air mixture control is more accurate at the end of the regeneration cycle. Also in this method, regeneration start of two NOx absorbers is performed simultaneously. In this case, the regeneration time is determined via a sensor signal, and the sensor is a linear sensor. An estimated regeneration time shorter than the actual regeneration time of the NOx absorber is calculated from the raw emissions of the internal combustion engine or read from a characteristic map in the control device. Thus, the estimated playback time divides the actual playback time into at least two individual phases. Thereby, the load of each NOx absorber can be confirmed separately and can be selected for each cylinder group to determine the regeneration cycle time.

  The regeneration method of the NOx absorber according to claims 10 and 11 has an advantage that the control strategy is very simple. A step response sensor is used for this method. The step response sensor supplies a digital signal to the control device. In this method, regeneration starts at different times for each cylinder group. The start of the regeneration cycle for the first cylinder group is delayed in time from the start signal for the regeneration cycle of the second cylinder group. Basically the same method steps as in the methods of claims 6 and 7, but different for each cylinder group. Therefore, the simple control strategy of claims 6 and 7 is maintained. In this case, however, each cylinder group performs its regeneration cycle in turn. The start of the regeneration cycle for the second cylinder group is started before the end of the regeneration cycle for the first cylinder group. However, it starts at the end of the first regeneration cycle at the latest.

  The method of regenerating the NOx absorber according to claim 12 is sufficiently consistent with the method according to claims 10 and 11. Unlike the method according to claims 10 and 11, a linear sensor is used. The tolerance can be well defined and maintained by this sensor.

  The estimated regeneration time according to claim 13 is within a time range in which the regeneration cycle can be carried out in a suitable manner. At that time, there is no need to influence the operation of the internal combustion engine or the driver need to receive feedback via the internal combustion engine.

First and second playback time t1 , T2 is set to the value of claim 14 as well, and is an effective time for an actual driving operation that enables a regeneration cycle without affecting the operating characteristics of the internal combustion engine.
By determining the estimated regeneration time t according to claims 15 and 16, changes in the internal combustion engine during operation of the internal combustion engine with respect to emission formation can be determined and corrected over the life of the internal combustion engine.

  The determination of the estimated regeneration time tno according to claims 15 and 17 is a simple and low-cost method for performing a simple exhaust purification that is kept within narrow tolerance limits for exhaust emissions during the entire life of the internal combustion engine. .

  Next, a preferred embodiment of the exhaust purification equipment according to the present invention will be described in detail with reference to one drawing.

  An intake manifold 10 composed of a first intake pipe group 10 'and a second intake pipe group 10 "is fixed to the internal combustion engine 2. One intake pipe group 10', 10" is representative of one intake manifold group 10 '. The intake pipe is shown. The first intake pipe group 10 ′ is connected to the first combustion chamber group 5, and the second intake pipe group 10 ″ is connected to the second combustion chamber group 5 ′. Similarly, each combustion chamber group The first combustion chamber group 5 is connected to the first exhaust pipe 3 to guide the gas, and the second combustion chamber group 5 'is connected to the first exhaust chamber 3 to guide the exhaust gas. The first exhaust pipe 3 incorporates a first catalytic purification device 4, that is, a NOx absorber, and the second exhaust pipe 3 'has a second catalyst. A NOx absorber is also incorporated, which is likewise a NOx absorber, which is preferably a NOx storage catalyst, two exhaust pipes downstream of the two catalytic cleaners 4, 4 '. 3 and 3 'are connected to a common exhaust pipe 6. In this exhaust pipe 6, Is incorporated with a third catalytic purification device 9, here a three-way catalyst, upstream of the first catalytic purification device 4, a first sensor 7 is arranged in the exhaust pipe 3, and the second A second sensor 7 'is disposed in the exhaust pipe 3' upstream of the catalytic purification device 4'.A third sensor 8 is disposed in the common exhaust pipe 6 upstream of the third catalytic purification device 9. The working elements of the sensors 7, 7 ', 8 are in contact with the exhaust gas, all three sensors 7, 7', 8 are oxygen sensors, but they can also be NOx sensors. In the example, it is a linear sensor, but it may be a step response sensor for other regeneration methods of the NOx absorber, all three sensors 7, 7 ', 8 being electrically connected to the control device 2'. This control device is also an internal combustion engine control device. Separate control devices may be provided for the control equipment 1 and the internal combustion engine 2. In other embodiments, downstream of the first and second sensors 7, 7 'and / or downstream of the third sensor 8. In addition, at least one catalytic purification device can be provided.

  Next, four advantageous methods for regenerating the first and second catalytic purification devices 4 and 4 'in the exhaust purification equipment 1 will be described in detail.

  For all four methods, the internal combustion engine 1 comprises at least two combustion chamber groups 5, 5 ', each combustion chamber group 5, 5' being connected to the exhaust pipes 3, 3 'so as to guide the exhaust. The point is common. Furthermore, separate mixing ratio control is possible, i.e. a different excess air ratio [lambda] for each combustion chamber group 5, 5 '. The excess air ratio λ for the mixture in the first combustion chamber group 5 is denoted by λZ1, and the excess air ratio λ for the mixture in the second combustion chamber group 5 ′ is denoted by λZ2. It is understood that λNK is a common excess air ratio in the exhaust pipe. A theoretical mixture means λ = 1, a rich mixture (excess fuel) is 0.5 <λ <1, and a lean mixture (excess air) is 30> λ> 1. Depending on the sensor 7, 7 ', 8, ie the NOx sensor or O2 sensor used, different exhaust components such as NOx or O2 or HC are measured from the exhaust. The start of the regeneration cycle is the start of the rich mixture operation of at least one combustion chamber group 5, 5 '. A regeneration cycle is necessary when the NOx absorption capacity of the catalytic purification device 4, 4 ', i.e. the NOx absorber, falls below an acceptable limit. A regeneration cycle is understood to be the time to regenerate all NOx absorbers. The regeneration time is related to the NOx absorber.

In the case of the first method, each sensor 7, 7 ', 8 is a linear sensor. In this method, the same mixture is supplied to both combustion chamber groups 5, 5 '. The next method step takes place after the start of the regeneration cycle.
The operation of the internal combustion engine with the same rich mixture λ = (λZ1 = λZ2), preferably 0.7 <λ <95, ie the operation of the first and second cylinder groups 5, 5 ′ together and the first Continuous detection of λZ1 by the sensor 7, λZ2 by the second sensor 7 ′ and λNK by the third sensor 8.
-The end of the regeneration cycle when the limit value is reached within the predetermined tolerance of λNK.

  Instead, the detected excess air ratios λZ1, λZ2, and λNK can be compared by the control device 2 ′ until λZ1 = λZ2 = λNK. As soon as the three measurement points have the same value, the regeneration cycle is terminated. That is, the internal combustion engine is newly operated with a lean air-fuel mixture.

  In the case of the second method, each sensor 7, 7 ', 8 is a linear sensor, and the start of the regeneration cycle of each combustion chamber group 5, 5' is the same in time. The next method step takes place after the start of the regeneration cycle.
-Operation of the first and second cylinder groups 5, 5 'with a rich mixture λZ1 = λF1 and λZ2 = λF1 (in this case after the start of the regeneration cycle, λF1 = λF2 is preferably 0.5 <λ <0.95. The control device 2 by continuous detection of λZ1 by the first sensor 7, λZ2 by the second sensor 7 ′ and λNK by the third sensor 8 and calculation or reading from the characteristic map. Determination of the estimated playback time t using ′.
-Before the end of the estimated regeneration time t, the first cylinder group 5 is operated with an excess air ratio λZ1 = (λF1 + x) <1, and the second cylinder group 5 ′ is operated with an excess air ratio λZ2 = (λF2-x). <Operated at λZ1.
-First condition λNK = ((λF1 + x) × m1 + Λreg × m2)) / (m1 + m2) or the second condition λNK = ((λF2−x) × m2 + Λz1 × m1)) / (m1 + m2) is continuously checked by the control device 2 '.
If the first condition is satisfied, the first combustion chamber group 5 is operated with the theoretical mixture λz1 = 1, and the mixture λF2 of the second combustion chamber group 5 ′ is controlled by the control device 2 for the next regeneration cycle. Therefore, λF2neu <λF2.
-If the second condition is satisfied, the second combustion chamber group 5 'is operated with the theoretical mixture λz2 = 1 and the mixture λF1 of the first combustion chamber group 5 is controlled for the next regeneration cycle. 2 'results in λF1neu <λF1. continue
-It is continuously checked by the control device 2 'whether (λz1 + λZ2) / 2 = λNK.
When the condition λNK = (λz1 + λZ2) / 2 is satisfied, the regeneration cycle is terminated.

In the case of the third method, each sensor (7, 7 ', 8) is a step response sensor, and the start of the regeneration cycle of the combustion chamber groups 5, 5' is shifted in time. After the start of the regeneration cycle, the following method steps are performed.
-Operation of the first cylinder group 5 with a rich mixture (λZ1 = λF1) <1, preferably 0.7 <λ <0.95, and the excess air ratio of the stoichiometric mixture or the excess air of the lean mixture Operation of the second cylinder group 5 'at the rate λZ2 ≧ 1 and the elapsed first regeneration time t1 Start of time measurement to determine the total playback time t by the control device 2 '.
The operation of the second cylinder group 5 'with a rich mixture (λZ2 = λF2) <1, preferably 0.7 <λ <0.95, before the determined total regeneration time t has elapsed.
-Then, continuous measurement of λNK until λNK exceeds the threshold, first reproduction time t1 Stop measuring time. And-the operation of the first cylinder group 5 with the theoretical mixture λZ1 = 1 and the further operation of the second cylinder group 5 'with the rich mixture λZ2 = λF2 and the second regeneration time t2. 2. Time measurement start.
-Continuous measurement of λNK until the threshold is exceeded.
If the threshold is exceeded, the regeneration cycle is terminated and the second regeneration time t2 is detected. Measured first and second regeneration times t1 for the next regeneration cycle , T2, the rich mixture λF1, λF2 can be adapted. In this case, t2> t1 Is true, λF2 is changed by the control device 2 ′ to λF2neu <λF2 and λF1 is changed by the control device 2 ′ to λF1neu <λF1 for the next regeneration cycle.

In the case of the fourth method, each sensor 7, 7 ', 8 is a linear sensor, and the start of the regeneration cycle of the combustion chamber groups 5, 5' is staggered in time. After the start of playback, the following method steps are performed.
The operation of the first cylinder group 5 with a rich mixture λZ1 <1, preferably 0.7 <λ <0.95, and the operation of the second cylinder group 5 ′ with a second mixture λZ2 ≧ 1. .
-ΛNK = (λZ2 × m2 Continuous measurement of λNK up to + λz1 × m1) / (m1 + m2).
The operation of the first cylinder group with a lean mixture λZ1 ≧ 1 and the operation of the second cylinder group 5 ′ with a rich mixture λZ2 <1, preferably 0.7 <λ <0.95.
-ΛNK = (λZ1 × m1 Continuous measurement of λNK up to + λz2 × m2) / (m1 + m2).
-ΛNK = (λZ1 × m1 The playback cycle ends when + λz2 × m2) / (m1 + m2).

For all methods, the total playback time t is at least 0.2 seconds. The entire regeneration time is detected by the control device, by calculating the NOx untreated emission of the internal combustion engine, or by reading the characteristic map stored in the control device 2 '. First and second playback time t1 , T2 is 0.5 to 0.99 times the total reproduction time t.

1 is a diagram schematically showing an exhaust purification equipment 1 of an internal combustion engine 2 schematically shown.

Explanation of symbols

DESCRIPTION OF SYMBOLS 1 Exhaust purification equipment 2 Internal combustion engine 2 'Control apparatus 3 1st exhaust pipe 3' 2nd exhaust pipe 4 1st catalytic purification apparatus 4 '2nd catalytic purification apparatus 5 1st combustion chamber group 5' Second combustion chamber group 6 Common exhaust pipe 7 First sensor 7 'Second sensor 8 Third sensor 9 Third catalytic purification device 10 Intake device 10' First intake pipe group 10 "Second Intake pipe group

Claims (17)

  A first exhaust pipe (3) having a first catalytic purification device (4) and a second exhaust pipe (3 ') having a second catalytic purification device (4'); And the second exhaust pipe are guided to one common exhaust pipe (6) downstream of the first and second catalytic purification devices (4, 4 '), and each catalytic purification device (4, 4' ), One first sensor (7, 7 ') is provided, and this first sensor is provided in each exhaust pipe (3, 3') upstream of each catalytic purifier. In the exhaust gas purification equipment (1) for an internal combustion engine (2) equipped with the NOx absorber, the catalytic purification device (4, 4 ') is a NOx absorber, and at least the regeneration of the catalytic purification device (4, 4'). Exhaust purification equipment, characterized in that a common third sensor (8) is provided in a common exhaust pipe (6).   2. An exhaust purification system according to claim 1, characterized in that each of the three sensors (7, 7 ', 8) is a NOx sensor and / or an O2 sensor.   3. An exhaust purification system according to claim 1 or 2, characterized in that each of the three sensors (7, 7 ', 8) is a linear sensor and / or a step response sensor.   4. An exhaust purification system according to claim 1, wherein each sensor emits an electrical signal, wherein the signal can be evaluated by a control device (2 ').   At least one other catalytic purification device (9) is arranged downstream of the first and second sensors (7, 7 ') and / or downstream of the third sensor (8). The exhaust gas purification equipment according to any one of claims 1 to 4. 6. A method for regenerating first and second catalytic purification devices (4, 4 ') of an exhaust purification system (1) according to at least one of claims 1 to 5, after the start of the regeneration cycle. Next method step-operating the internal combustion engine (2) with excess fuel,
-Continuously measuring the proportion of exhaust components in the common exhaust pipe (6);
A method characterized in that the regeneration cycle is terminated when the proportion of exhaust components approaches a limit value. Next method step-continuously measure the proportion of exhaust components in the first, second and common exhaust pipes (3, 3 ', 6),
-The regeneration cycle is terminated when the same proportion of exhaust components within tolerance limits is measured in the first, second and common exhaust pipes (3, 3 ', 6). 6. The method according to 6. The internal combustion engine comprises at least two combustion chamber groups (5, 5 '), each exhaust pipe (3, 3') being connected to the combustion chamber groups (5, 5 ') to guide the exhaust, each combustion First and second catalytic purification devices (1) of exhaust purification equipment (1) according to at least one of claims 1 to 5, wherein the mixing ratio control for the chamber group (5, 5 ') is performed separately. 4, 4 ') in the method for regenerating, after the start of the regeneration cycle, the next method step-operating the internal combustion engine (2) with a first excess fuel,
-Continuously measure the proportion of exhaust components in the first, second and common exhaust pipes (3, 3 ', 6);
-Before the estimated regeneration time t has elapsed, the first combustion chamber group (5) is operated with the second excess fuel and the second combustion chamber group (5 ') is operated with the third excess fuel. And
-Determining the load conditions for each catalytic purifier (4, 4 ') and adapting excess fuel for each combustion chamber group (5, 5');
A method characterized in that the regeneration cycle is terminated when the proportion of the exhaust components in the common exhaust pipe (6) approaches a limit value.   Ending the regeneration cycle when the proportion of exhaust components within the tolerance limits, which is the same as the average of the first and second exhaust pipes (3, 3 '), is measured in the common exhaust pipe (6) The method of claim 8, wherein: The internal combustion engine comprises at least two combustion chamber groups (5, 5 '), each exhaust pipe (3, 3') being connected to the combustion chamber groups (5, 5 ') to guide the exhaust, each combustion First and second catalytic purification devices (1) of exhaust purification equipment (1) according to at least one of claims 1 to 5, wherein the mixing ratio control for the chamber group (5, 5 ') is performed separately. 4, 4 ') in the next process step after the start of the regeneration cycle-the first combustion chamber group (5) is operated with excess fuel and the second combustion chamber group is theoretically mixed Driving with care, the first regeneration time t1 Start measuring for
-Continuously measure the proportion of exhaust components in the first, second and common exhaust pipes (3, 3 ', 6);
-Before the estimated regeneration time t has elapsed, the second combustion chamber group (5 ') is operated with excess fuel and measurement for the second regeneration time t2 is started,
The first regeneration time t1 when the first combustion chamber group (5) is operated with a stoichiometric mixture and the proportion of exhaust components in the common exhaust pipe (6) approaches the limit value. Decide
A method for determining a second regeneration time t2 and terminating the regeneration cycle when the proportion of exhaust components in the common exhaust pipe (6) approaches a limit value; Next method step-the second playback time t2 is the first playback time t1 Longer, change the mixture for the second combustion chamber group (5 ') for the next regeneration cycle to have more excess fuel,
The second playback time t2 is the first playback time t1 11. The air-fuel mixture for the first combustion chamber group (5) for the next regeneration cycle is changed to have more excess fuel when shorter than Method. The internal combustion engine comprises at least two combustion chamber groups (5, 5 '), each exhaust pipe (3, 3') being connected to the combustion chamber groups (5, 5 ') to guide the exhaust, each combustion First and second catalytic purification devices (1) of exhaust purification equipment (1) according to at least one of claims 1 to 5, wherein the mixing ratio control for the chamber group (5, 5 ') is performed separately. 4, 4 ') in the next method step after the start of the regeneration cycle-operating the first combustion chamber group (5) with excess fuel and the second combustion chamber group (5' ) With theoretical air / fuel-air mixture or excess air,
-Continuously measure the proportion of exhaust components in the first, second and common exhaust pipes (3, 3 ', 6);
-When the proportion of exhaust components in the common exhaust pipe (6) reaches an average proportion of exhaust components from the first and second exhaust pipes (3, 3 ') within an acceptable range; Operate the combustion chamber group (5) with theoretical air / fuel-fuel mixture or excess air, operate the second combustion chamber group (5 ') with excess fuel,
-When the proportion of exhaust components in the common exhaust pipe (6) reaches the average proportion of exhaust components from the first and second exhaust pipes (3, 3 ') within the allowable range, A method characterized by terminating.   12. A method according to any one of claims 8 to 11, characterized in that the estimated playback time is at least 0.2 seconds. First playback time t1 12. A method according to claim 10 or 11, characterized in that the second reproduction time t2 is 0.5 to 0.99 times the total reproduction time.   12. Method according to any one of claims 8 to 11, characterized in that the estimated playback time t is determined by the control device (2 ').   16. Method according to claim 15, characterized in that the estimated playback time t is calculated by the control device (2 '). 16. Method according to claim 15, characterized in that the estimated playback time t is read from the characteristic map by the control device (2 ').

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