JP4505330B2 - Method for regenerating first and second catalysts of exhaust purification equipment - Google Patents

Description

The invention relates to a method for regenerating first and second catalysts of an exhaust purification facility for an internal combustion engine according to the features of the premise of claims 1, 3 and 5 .

  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 claims 1 , 3 and 5 .
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.

Depending on the formation of the sensor, i.e. NOx sensor or O2 sensor, i.e. linear or step response formation, the optimum desulfation scheme is used when the low cost identical component principle for the sensor is used That is, the NOx absorber can be regenerated.

Since the control of the control equipment for modern internal combustion engine is common, it is advantageous to include together the desulfurization oxidation of the NOx absorber to the control strategy of the control equipment. This integration saves separate control equipment or components, thus reducing manufacturing costs.

Since NOx absorber is unable to remove all hazardous materials from the exhaust, it is advantageous to incorporate other catalytic purifier in an exhaust purification device. In this case, the other catalytic purification device is a three-way catalyst.

In the case of the regeneration method of the NOx absorber according to claim 1 and 2, 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 performed. In using this method, the amount of residual harmful substances is further reduced because the 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 3 and 4 has the 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 . Each cylinder group executes 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 regeneration method of the NOx absorber according to the fifth aspect is sufficiently consistent with the method according to the third and fourth aspects. Unlike the method according to claims 3 and 4 , a linear sensor is used. The tolerance can be well defined and maintained by this sensor.

The estimated regeneration time according to claim 6 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.

Setting the first and second regeneration times t1 and t2 to the values described in claim 7 also allows for a regeneration cycle without affecting the operating characteristics of the internal combustion engine. It is a valid time.
By determining the estimated regeneration time t according to claims 8 and 9, 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 estimated regeneration time tno according to claims 8 and 10 is determined in a simple and low-cost way in order to perform a simple exhaust purification that is kept within narrow tolerance limits for exhaust emissions during the entire life of the internal combustion engine. is there.

  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, three 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 three 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. The theoretical mixture means λ = 1, the rich mixture (excess fuel) is 0.5 <λ <1, and the lean mixture (excess air) is 30>λ> 1. Depending on the sensor 7, 7 ', 8, i.e. 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, 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.
The operation of the first and second cylinder groups 5, 5 ′ with a rich mixture λZ1 = λF1, 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 'is detected 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 used.
-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.
Whether the first condition λNK = ((λF1 + x) × m1 + λreg × m2)) / (m1 + m2) or the second condition λNK = ((λF2−x) × m2 + λz1 × m1)) / (m1 + m2) Inspected continuously 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. By ′, 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 by the control device 2 for the next regeneration cycle. Therefore, λF1neu <λF1. Subsequently, whether or not − (λz1 + λZ2) / 2 = λNK is continuously checked by the control device 2 ′.
When the condition λNK = (λz1 + λZ2) / 2 is satisfied, the regeneration cycle is terminated.

In the case of the second 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.
The 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 or lean mixture Operation of the second cylinder group 5 ′ with λZ2 ≧ 1, start of time measurement for determining the elapsed first regeneration time t1, and determination of the overall regeneration 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 overall regeneration time t has elapsed.
-Then, the continuous measurement of λNK until λNK exceeds the threshold, the time measurement of the first reproduction time t1 is stopped. And-operation of the first cylinder group 5 with the theoretical mixture λZ1 = 1 and further operation of the second cylinder group 5 'with the rich mixture λZ2 = λF2 and the second for the second regeneration time t2. 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. Depending on the measured first and second regeneration times t1, t2, the rich mixture λF1, λF2 can be adapted for the next regeneration cycle. In this case, when t2> t1 is true, for the next reproduction cycle, λF2 is changed to λF2neu <λF2 by the control device 2 ′, and λF1 is changed to λF1neu <λF1 by the control device 2 ′.

In the case of the third 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. .
-Continuous measurement of λNK up to λNK = (λZ2 × m2 + 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.
-Continuous measurement of λNK up to λNK = (λZ1 × m1 + λz2 × m2) / (m1 + m2).
The end of the regeneration cycle when λNK = (λZ1 × m1 + 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 '. The first and second reproduction times t1, t2 are 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.

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 (10)

NOx absorber having 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 first and second exhaust pipes are guided to one common exhaust pipe (6) downstream of the first and second catalytic purification devices (4, 4 '), and each of the catalytic purifications described above. A unique first or unique second sensor (7, 7 ') is assigned to each device (4, 4') upstream in each exhaust pipe (3, 3 '), and the catalyst The purification device (4, 4 ') is a NOx absorber, and at least a common third sensor (8) for regeneration of the catalytic purification device (4, 4') is a common exhaust pipe (6 ) Is a method for regenerating the first and second catalytic purification devices (4, 4 ') of the exhaust gas purification equipment (1) for the internal combustion engine (2). Te,
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 In a method for regenerating first and second catalytic purification devices (4, 4 ') of an exhaust purification facility (1) , wherein the mixture ratio control for the chamber group (5, 5') is performed separately. ,
After the start of the regeneration cycle, the next method step-operating the internal combustion engine (2) with the first excess fuel,
-Continuously measuring the proportion of exhaust components in the first, second and common exhaust pipes (3, 3 ', 6);
-Operating the first combustion chamber group (5) with the second excess fuel and operating the second combustion chamber group (5 ') with the third excess fuel before the estimated regeneration time t has elapsed. 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 1 , wherein: NOx absorber having 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 first and second exhaust pipes are guided to one common exhaust pipe (6) downstream of the first and second catalytic purification devices (4, 4 '), and each of the catalytic purifications described above. A unique first or unique second sensor (7, 7 ') is assigned to each device (4, 4') upstream in each exhaust pipe (3, 3 '), and the catalyst The purification device (4, 4 ') is a NOx absorber, and at least a common third sensor (8) for regeneration of the catalytic purification device (4, 4') is a common exhaust pipe (6 ) Is a method for regenerating the first and second catalytic purification devices (4, 4 ') of the exhaust gas purification equipment (1) for the internal combustion engine (2). Te,
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 In a method for regenerating first and second catalytic purification devices (4, 4 ') of an exhaust purification facility (1) , wherein the mixture ratio control for the chamber group (5, 5') is performed separately. ,
After the start of the regeneration cycle, the next method step-operating the first combustion chamber group (5) with excess fuel and operating the second combustion chamber group with the stoichiometric mixture for the first regeneration time t1 Start measuring
-Continuously measuring 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 the measurement for the second regeneration time t2 is started,
When the first combustion chamber group (5) is operated with a stoichiometric mixture and the proportion of the exhaust components in the common exhaust pipe (6) approaches the limit value, the first regeneration time t1 is determined;
A method for determining the second regeneration time t2 and terminating the regeneration cycle when the proportion of the exhaust components in the common exhaust pipe (6) approaches a limit value; Next method step-When the second regeneration time t2 is longer than the first regeneration time t1, the mixture for the second combustion chamber group (5 ') for the next regeneration cycle Change to have fuel,
The mixture for the first combustion chamber group (5) for the next regeneration cycle has more fuel when the second regeneration time t2 is shorter than the first regeneration time t1. The method according to claim 3 , wherein the method is changed. NOx absorber having 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 first and second exhaust pipes are guided to one common exhaust pipe (6) downstream of the first and second catalytic purification devices (4, 4 '), and each of the catalytic purifications described above. A unique first or unique second sensor (7, 7 ') is assigned to each device (4, 4') upstream in each exhaust pipe (3, 3 '), and the catalyst The purification device (4, 4 ') is a NOx absorber, and at least a common third sensor (8) for regeneration of the catalytic purification device (4, 4') is a common exhaust pipe (6 ) Is a method for regenerating the first and second catalytic purification devices (4, 4 ') of the exhaust gas purification equipment (1) for the internal combustion engine (2). Te,
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 In a method for regenerating first and second catalytic purification devices (4, 4 ') of an exhaust purification facility (1) , wherein the mixture ratio control for the chamber group (5, 5') is performed separately . ,
After the start of the regeneration cycle, the next method step-operating the first combustion chamber group (5) with excess fuel and the second combustion chamber group (5 ') with theoretical air / fuel-mixture or excess air. Drive,
-Continuously measuring 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; Operating the combustion chamber group (5) with theoretical air / fuel-mixture or excess air, operating the second combustion chamber group (5 ') with excess fuel,
-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 the allowable range; A method characterized by terminating. The method according to any one of claims 1 to 4 , characterized in that the estimated playback time t is at least 0.2 seconds. Wherein the first reproduction time t1 and the second reproduction time t2 is 0.5 to 0.99 times the total playback time, according to claim 3 or 4 The method according. Estimated playback time t is characterized in that it is determined by the control device (2 ') The method according to any one of claims 1-4. 9. Method according to claim 8 , characterized in that the estimated playback time t is calculated by the control device (2 '). 9. Method according to claim 8 , characterized in that the estimated playback time t is read from the characteristic map by the control device (2 ').

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