WO2007016713A2

WO2007016713A2 - Method for increasing the exhaust gas temperature for an internal combustion engine

Info

Publication number: WO2007016713A2
Application number: PCT/AT2006/000333
Authority: WO
Inventors: Dietrich Meyerdierks; Friedrich Köskemeier; Alois Fürhapter; Dirk Denger; Aleksander Pinter
Original assignee: Avl List Gmbh
Priority date: 2005-08-11
Filing date: 2006-08-07
Publication date: 2007-02-15
Also published as: DE112006002008B4; WO2007016713A3; DE112006002008A5

Abstract

The invention relates to a method for increasing the exhaust gas temperature for an internal combustion engine with several differently operated cylinders, at least one first cylinder, preferably a first group of cylinders being operated with a rich fuel/air mixture. According to the invention, the fuel/air ratio and/or the load of each individually operated cylinder is adjusted separately from the other cylinders, whereby the idle smoothness may be improved and the combustion in each cylinder is preferably individually adapted to the adjusted fuel/air ratio or the set load.

Description

55416

Method for raising the exhaust gas temperature in an internal combustion engine

The invention relates to a method for raising the exhaust gas temperature in an internal combustion engine having a plurality of differently operated cylinders, wherein at least a first cylinder, preferably a first group of cylinders is operated with rich fuel / air ratio. Furthermore, the invention relates to a method for determining the loading state of a particulate filter of an internal combustion engine with at least one particle sensor whose measuring principle is based on the occurring voltage drop between two electrodes resulting in accumulating on a sensor surface soot particles. Furthermore, the invention relates to a device for determining the loading state of a particulate filter of an internal combustion engine with at least one upstream of the particulate filter in the exhaust line arranged first particle sensor.

It is known to run one part of the cylinder rich and another part of the cylinder lean to produce an exothermic reaction in the catalyst, for example from the publications JP 05086848 A, WO 01/21950 A1, US 6,467,259 B1, JP 56113009 A or JP 2001-152844 A. This makes it possible to provide a combustible mixture on the catalyst. By means of cylinders operated with rich mixture, the availability of hydrocarbons and carbon monoxide in the catalyst is ensured. On the other hand, with the lean-burned cylinders, oxygen is provided to the catalyst. This results in an exothermic reaction of hydrocarbon and oxygen in the catalyst, whereby the Katalysatoranspringzeit significantly reduced and thus fuel consumption and emissions are minimized. The disadvantage, however, that the smoothness is degraded by the unequal distribution.

From DD 219 587 Al a particle sensor is known, which serves to determine the loading of combustion exhaust gases with unburned particles. In this case, two metal electrodes are used as a probe, between which the flowing exhaust gas forms a precipitate, the amount and quality to be determined by measuring the resistance. Subsequently, the electrodes are annealed so that the precipitate evaporates and the probe is ready for a new measurement.

Furthermore, from DE 41 42 959 Al a probe for a particle sensor is known whose surface consists of electrically conductive non-metal, such as fullerene. During the loading of a particle sensor, a voltage drop occurs between the electrodes. However, the voltage drop is proportional to the loading of the particulate filter only within a certain range of the measurement duration.

It is the object of the invention to avoid these disadvantages and to improve the smoothness, or to enhance the effect of the exhaust gas temperature increase. Another object of the invention is to develop a method with which the loading of the particulate filter can be determined as simply as possible.

According to the invention this is achieved in that the fuel / air ratio and / or the load of each actively operated cylinder is set independently of the other cylinders, preferably wherein the combustion in each cylinder individually to the set fuel / air ratio, or the set load adjusted, preferably individually for the set fuel / air ratio, or the set load is optimized.

In a preferred embodiment of the invention it is provided that at least one second cylinder, preferably a second group of cylinders, is operated with a lean fuel / air ratio. By adjusting the charge cylinder selectively, cylinders can be operated at the same load (indicated mean pressure) despite the fact that some of the cylinders are rich and the rest of the cylinders are lean. This significantly increases the smoothness. The filling state of each cylinder can be selected independently of the other cylinders.

The setting of the burning rate takes place for example via the turbulence in the combustion chamber. This can be done by varying the timing of the internal combustion engine, for example by the variation of the closing edge of at least one inlet valve and / or the valve lift at least one inlet valve. With variable valve control, the relevant parameters can be changed in a wide range. By adjusting the burning rate, preferably increasing it, the combustion can be shifted late, resulting in an increased exhaust gas temperature. The cylinders can be operated with the same load (indicated mean pressure) but different fillings. The air ratio of the exhaust gas of the entire engine can be stoichiometric, slightly lean, or even slightly rich after merging the individual cylinder exhaust gases.

It is also possible that the fuel / air ratio in all cylinders is adjusted stoichiometrically, but the cylinders are operated with significantly different indexed mean pressures. In a further embodiment of the invention can be provided that at least a second cylinder, preferably a second group of cylinders, the injection of the fuel is completely switched off and a predefined secondary air quantity is set via pumped fresh air over the timing of the intake and / or exhaust valves of this cylinder , In the case of cycle-good cylinder deactivation, the internal torque of the fired cylinders is approximately doubled in a cycle-faithful manner, which significantly improves the combustion stability in the fired cylinders and substantially reduces the raw emissions.

The increase in combustion stability can be used to a significant shift of combustion late, thereby increasing the exhaust gas temperature and thus the catalyst are heated with minimal raw emissions.

This effect can be intensified if the deactivated cylinders pump fresh air to the catalytic converter. The secondary air quantity, or the amount of fresh air pumped through, is set via the control times of this cylinder. The non-deactivated cylinders can be operated with a rich fuel / air mixture. The measures for raising the exhaust gas temperature are preferably used during the warm-up phase until reaching the light-off temperature of the catalyst and / or in phases of low engine load to increase the temperature in the catalyst.

In order to keep the cylinder load as low as possible, it is advantageous if the unequal distribution of the fuel / air ratio and / or load during engine operation is reversed at least once, preferably periodically, between the first group and the second group of cylinders. As a result, the cylinder load can be thermally uniformed and the cooling of a cylinder running on low or zero load can be prevented.

In the context of the invention, it is provided that above and / or below a predefined total engine load and / or speed, the unequal distribution of the load and / or the filling between the cylinders is deactivated.

The measures for raising the exhaust gas temperature are preferably carried out as a function of the temperature of the internal combustion engine and / or the temperature of the environment.

The loading of the particle filter can be determined in a simple manner by carrying out several measurements with the particle sensor one after the other and interrupting each measurement when a defined voltage drop is reached and the individual measurement periods are recorded and, after interrupting the measurement of the particle filters in an electrical output. transition state is added, and that the individual measurement periods are added to a total duration and from the total duration a size proportional to the loading condition of the particulate filter is formed. Preferably, it is provided that the particle filter is set by a burning process of the particles in the electrical output state.

The duration of the measurement is - regardless of the operating parameters of the internal combustion engine - directly proportional to the loading of the filter in this period. To detect the cumulative loading of the particulate filter, when the defined voltage drop is reached, the particle sensor is electrically heated in such a way that the adsorbed particles are burned off at short notice and the electrical state of the starting point of the measurement is restored. The monitoring of the burning time is controlled by measuring the voltage drop. The burn-off time is to be designed so that it is as small as possible compared to the measuring time. Optionally, the sensor surface can be catalytically coated to keep the burn-off time and the burn-off temperature small.

By continuously adding the times of the collecting cycles of particles to the particle sensor during operation of the internal combustion engine, a variable proportional to the loading state of the filter can be formed with suitable algorithms in the engine control unit. The initiation of the burning process of the particulate filter can thus be triggered at an appropriate time.

In a further embodiment of the invention can be provided that a first particle sensor upstream of the particulate filter and a second particle sensor downstream of the particulate filter - for on-board Diagnosis monitoring (OBD monitoring) - is arranged and that the time duration of the second particle sensor until reaching a defined voltage drop is set at the time of the first particle sensor until reaching the defined voltage drop and that is concluded in deviation of this ratio of a defined fluctuation range on a malfunction of the particulate filter. In the normal function of the particle filter, the ratio of the two time constants is approximately constant in a first approximation. In case of malfunctions, the ratio shifts depending on the type of disturbance to smaller or larger proportions.

For carrying out the method, a measuring device is suitable which has a first particle sensor upstream of the particle filter and a second particle sensor downstream of the particle filter.

The invention will be explained in more detail below with reference to FIGS. Show it: Figure 1 shows a 4-cylinder in-line engine with single-flow catalyst in parallel operation.

2 shows a 4-cylinder in-line engine with a single-flow catalyst in cycle operation.

3 shows a 6-cylinder V-engine with double-flow catalyst for parallel operation.

4 shows a six-cylinder V-engine with double-flow catalytic converter during cycle operation.

5 shows a 6-cylinder V-engine with single-flow catalyst in parallel operation.

6 shows a 6-cylinder V-engine with single-flow catalyst in cyclic operation.

7 shows a six-cylinder in-line engine with twin-flow catalyst in parallel operation.

8 shows a six-cylinder in-line engine with double-flow catalyst during cycle operation.

9 shows a 6-cylinder in-line engine with a single-flow catalyst;

10 shows a 4-cylinder in-line engine with single-cylinder catalyst with cylinder deactivation.

11 shows a 6-cylinder V-engine with a single-flow catalyst and cylinder deactivation;

FIG. 12 shows a part of an exhaust line; FIG.

FIG. 13 shows a particle sensor; FIG.

FIG. 14 plots the voltage drop during a particle measurement over time; FIG.

FIG. 15 shows a heating device for the sensor; FIG.

FIG. 16 shows the voltage drop during a burn-off period; FIG.

17 shows a measuring arrangement according to the invention; and FIG. 18 shows the voltage drop for the particle sensors shown in FIG. 17. FIG.

Figures 1 to 11 show various internal combustion engines for use of the method according to the invention.

Cycle operation refers to an operation in which the charge and / or load between the first and second groups of cylinders is reversed from one to the other engine cycle for a predefined number of cycles. Parallel operation is understood to mean an operation with unequal distribution of charge and / or load between the first and second group of cylinders, in which no change of charge or load between the groups of cylinders is made.

In the figures, the individual cylinders are designated by reference numerals 1, 2, 3, 4, 5, 6. Of the individual cylinders lead two groups of exhaust pipes Ll, L2 to single or double-flow or separate catalysts K.

F denotes fat-operated cylinders, M lean-operated cylinders.

The arrangements illustrated in FIGS. 1 to 9 have in common that one group of cylinders is operated fat and another group of cylinders is operated lean. The rich operation ensures the delivery of hydrocarbon and carbon monoxide to the catalyst K. On the other hand, lean operation ensures the provision of oxygen (O ₂ , O) in the catalytic converter.

This results in an exothermic reaction of hydrocarbon and oxygen in the catalyst, resulting in a significant reduction in Katalysatoranspringzeit while minimizing fuel consumption and emissions, or which prevents the catalyst cools down too far in operation with the lowest load.

In the internal combustion engine shown in FIG. 1, the first and the third cylinder 1, 3 are operated fat and the second, and the fourth cylinder 2, 4 lean. As a result, an overall air ratio λ _κ > 0.9 is established in the region of the catalyst K. The typical firing order is 1-3-4-2. The variant shown in FIG. 2 differs from the parallel operation indicated in FIG. 1 in that the groups of lean-operated cylinders and rich-operated cylinders change cyclically. In a first cycle I, for example, the cylinder 1 and the cylinder 3 are operated fat and the cylinders 2 and 4 are operated lean. In the second cycle II, the cylinders 1 and 3 are lean, but the cylinders 2 and 4 are operated rich. Here, too, a total of air in the range of the catalyst K λ _κ > 0.9 at each cycle. The delivered cylinder torque is adapted to appropriate measures (control times) and is the same for all cylinders.

FIG. 3 and FIG. 4 show internal combustion engines with six cylinders and double-flow catalysts K. FIG. 3 shows the situation for a six-cylinder internal combustion engine with two exhaust gas lines L1 and L2 and two catalysts K for parallel operation. The cylinders 1, 4 are operated fat, the cylinders 3, 6 lean. The air ratio λ _κ for the cylinders 2, 5 is composed of the average value of the air numbers λ _{κ of} the cylinders 1, 3, or 4, 5. The dashed arrows indicate the typical ignition sequence 1-4-3-6-2-5. The inner load is the same for all cylinders. In the area of the catalysts K, a total air ratio λ _κ > 0.9 results.

Fig. 4 shows a similar 6-cylinder V-type internal combustion engine as in Fig. 3, wherein the air ratios of the cylinders 1, 3 on the one hand, and 4, 6 on the other cyclically changed. This means that in a first cycle I, the cylinders 1, 4 are operated in a rich manner and the cylinders 3, 6 are operated lean. In a second cycle II, the fillings between the cylinders 1, 4 and 3, 6 are reversed, so that the cylinders 1, 4 lean and the cylinders 3, 6 are operated fat. In the next cycle, the unequal distribution again corresponds to the situation of the first cycle I. The fuel / air ratio of the cylinders 2, 5 is again set together as the mean value of the fuel / air ratios of the cylinders 1, 3, and 4, 6. Again, in the region of the double-flow catalyst K, a total air ratio λ _κ > 0.9 results.

FIGS. 5 and 6 show 6-cylinder V-type internal combustion engines, wherein the two exhaust gas lines L1, L2 open into a single-flow catalyst. Fig. 5 shows the situation for parallel operation. The cylinders 1, 2 and 3 are rich, the cylinders 4, 5 and 6 are operated lean. Dashed lines indicate the typical firing order 1-4- 3-6-2-5. In the area of the catalyst, the sum of the air numbers λ "> 0.9 is again obtained.

Fig. 6 shows the internal combustion engine shown in Fig. 5 with cyclic operation. In a first cycle I, the cylinders 1, 2 and 3 are operated in a rich and cylinders 4, 5 and 6 are operated lean. In a second cycle II, the cylinders 1, 2 and 3 are lean and the cylinders 4, 5 and 6 are operated fat. Again, in the region of the catalyst K, a total air coefficient λ _κ of at least 0.9 results.

7 and 8 show six-cylinder series internal combustion engines with two exhaust gas lines L1 and L2 and twin-flow catalysts K. In the parallel operation shown in FIG. 7, the cylinders 1, 4 are operated in a rich, cylinders 2, 6 lean. The fuel / air ratios for the cylinder 3, 5 arise as Average values of the fuel / air ratios of the cylinders 2, 4, and 4, 6, respectively. The firing order may be, for example, 1-4-2-6-3-5. In the region of the catalyst K, a total air coefficient λ _κ of at least 0.9 results.

Fig. 8 shows the situation for cyclic operation. In a first cycle I, the cylinders 1, 4 are operated fat, the cylinders 2, 6 lean. In the second cycle II, the cylinders 1, 4 lean, the cylinders 2, 6 are operated fat. The fuel / air ratios for the cylinders 3, 6 result as average values of the fuel / air ratios of the cylinders 2, 4, and 4 and 6. In the area of the catalysts K, a total air ratio λ results for each cycle I, II _κ of at least 0.9.

Fig. 9 shows the situation for a six-cylinder in-line engine with single-flow catalyst K. In parallel operation, half of the cylinders, for example the cylinder 1, 3 are operated rich, the other half of the cylinders, for example 4, 5 and 6, run lean. If the internal combustion engine is operated cyclically, three cylinders are alternately operated rich and lean. For example, the cylinders 1, 2 and 3 are operated in a first cycle I rich, the cylinders 4, 5 and 6 lean. In a second cycle II, however, the cylinders 1 to 3 lean and the cylinders 4 to 6 are operated fat.

Following the same pattern, an 8-cylinder engine can also be operated in parallel or cyclically. The basic condition is that alternately lean and rich mixture is supplied for the respective catalyst K in firing order. The resulting mixture on the catalyst then sets the desired average.

FIGS. 10 and 11 show internal combustion engines in which one group of the cylinders is operated in rich mode and another group of the cylinders is switched off. The deactivated cylinders are designated by reference symbol A.

With fully variable, highly flexible valve train systems, it is possible to perform cylinder-consistent cylinder shutdown operations at engine startup. By the cylinder deactivation, the internal moment of the fired cylinder is approximately doubled with the same alternating torque, whereby the combustion stability improved significantly and the raw emissions fall significantly. The increase in combustion stability can be used to significantly shift the combustion late and thus heat the catalyst K with minimal raw emissions.

This effect can be intensified when the deactivated cylinders pump fresh air to the catalyst K, while the fired cylinders transport the fuel in the form of HC and CO emissions to the catalyst K by rich engine operation. Fig. 10 shows an arrangement with a single-flow catalyst K. The cylinders 1 to 4 open into a single exhaust line Ll, which leads to the catalyst K. Here is a group of cylinders, namely the cylinders 1, 3, operated in bold and the cylinders 2, 4 is turned off, which is indicated by reference numeral A.

Fig. 11 shows a 6-cylinder V-type internal combustion engine with a single-flow catalyst K. One possible strategy is to operate the cylinders 1, 2 and 3 rich and shut off the cylinders 4, 5 and 6.

FIG. 12 schematically shows an exhaust gas line 101 with a particle filter 102, wherein upstream of the particle filter 102 a first particle sensor 103 is arranged.

13 shows the sensor principle of the first particle sensor 103. The sensor principle is based on the property of the electrical conductivity of soot particles. In principle, a non-conductive surface 104 in the exhaust pipe 105 in front of the particle filter 102 is exposed to the soot particles interspersed exhaust gas flow so that the surface 104 by means of position and shape accumulates particles. This collection arrangement is supplied with direct current U _Mess . The voltage drop .DELTA.U across the surface 104 shown in FIG. 14 is used as a measurement signal for evaluating the loading state of the surface 104 of the first sensor 103. Unloaded is the voltage drop .DELTA.U zero, with increasing load the voltage drop ΔU asymptotically strives for a limit value. The period between T ₀ and Ti is - regardless of the operating parameters of the internal combustion engine - directly proportional to the loading of the particulate filter 102 in this period .DELTA.T. For detecting the cumulative loading of the particulate filter 102 of the voltage drop ΔUi T is _1, the surface 104 of the first sensor 103 is electrically heated, the deposited particulates are burned off in the short term and the electrical state of T ₀ is produced again when reaching. The monitoring of the burn time .DELTA.T ¹ is carried out via the measurement of the voltage drop .DELTA.U, as shown in Fig. 16. The burn-off time must be designed so that it is small compared to the measuring time ΔT. Optionally, the sensor surface 104 may be catalytically coated to keep the burn-off time ΔT ¹ and burn-off temperature small.

FIG. 15 schematically shows the heating of the sensor 103, for example by a PTC heating element 106 and / or by an electrical heating element 107. In addition, heat Q ₃ is added by the exhaust gas. During burn-off, the _measurement voltage U _{MeSs is applied} to the surface 104 of the sensor 103 to monitor the burn-off process. The sum of all loading periods ΔT of the first sensor 103 is proportional to the loading of the particulate filter 102: loading ~ ΣAT], where n is the number

the individual measurements is. Through a continuous addition of the times .DELTA.T of the collection cycles of particles at the sensor 103 during operation of the internal combustion engine, a variable proportional to the loading state of the particle filter 102 can thus be formed with suitable algorithms in the engine control unit. The initiation of the burning off process of the particulate filter 102 can thus be triggered at an appropriate time.

To determine the degree of separation, a second particle sensor 103a can be used downstream of the particle filter 102. The determination of the

ΔΓ degrades ~ - - is determined by the ratio of the two time constants ΔT ₂

.DELTA.T; after the particulate filter 102 to ΔTi before the particulate filter 102 determined. In the normal function of the particulate filter 102, the ratio of the two time constants is constant in a first approximation. In the case of malfunctions, the ratio shifts to smaller or larger proportions depending on the nature of the malfunction.

In Fig. 18, the voltage drop ΔUi and the corresponding time constant ΔTi is the first particle sensor 103 and the voltage drop .DELTA.U _2, as well as the corresponding time constant .DELTA.T ₂ of the second particle sensor 103a shown schematically.

Claims

1. A method for raising the exhaust gas temperature in an internal combustion engine having a plurality of differently operated cylinders, wherein at least a first cylinder, preferably a first group of cylinders with rich fuel / air ratio is operated, characterized in that the fuel / air ratio and / or the load of each individual actively operated cylinder is set independently of the other cylinders, wherein preferably the combustion in each cylinder is adapted individually to the set fuel / air ratio or the set load, preferably for the set fuel / air ratio. Ratio, or the set load is optimized.

2. The method according to claim 1, characterized in that the adjustment of the combustion over the burning rate by varying the timing of at least one inlet valve.

3. The method according to claim 1 or 2, characterized in that the adaptation of the burning rate by cylinder-specific variation of the closing edge of at least one inlet valve.

4. The method according to any one of claims 1 to 3, characterized in that the adjustment of the burning rate by cylinder-individual variation of the valve lift is at least one inlet valve.

5. The method according to any one of claims 1 to 4, characterized in that the adaptation of the burning rate is carried out by cylinder individual metering of internal residual gas.

6. The method according to any one of claims 1 to 5, characterized in that the adaptation of the combustion via the combustion position, preferably by adjusting the cylinder timing of the ignition takes place.

7. The method according to any one of claims 1 to 6, characterized in that the adaptation of the combustion takes place by cylinder-individual variation of the injection timing and / or the injection duration.

8. The method according to any one of claims 1 to 7, characterized in that the indicated mean pressure during the measures for raising the exhaust gas temperature is kept the same in all cylinders.

9. The method according to any one of claims 1 to 8, characterized in that the air ratio of the exhaust gas in the range of a catalyst according to Zu- merging of the exhaust gases of the individual cylinders is between 0.9 and 1.1.

10. The method according to any one of claims 1 to 9, characterized in that the fuel / air ratio is set stoichiometrically in all cylinders, but the cylinders have different indexed mean pressures.

11. The method according to any one of claims 1 to 10, characterized in that at least one second cylinder, preferably a second group of cylinders is operated with a lean fuel / air ratio.

12. The method according to any one of claims 1 to 11, characterized in that at least one second cylinder, preferably in a second group of cylinders, the injection of the fuel is completely switched off and over the timing of the intake and / or exhaust valves of this cylinder a predefined Secondary air quantity and / or pumped through fresh air quantity is set.

13. The method according to claim 10, characterized in that the remaining fired cylinders are operated with a rich fuel / air ratio.

14. The method according to claim 12 or 13, characterized in that the exhaust valves of at least one deactivated cylinder are kept closed.

15. The method according to any one of claims 12 to 14, characterized in that the inlet valves of at least one deactivated cylinder are kept closed.

16. The method according to any one of claims 1 to 15, characterized in that the fuel / air ratio and / or the load during engine operation at least once, preferably periodically, between the first group and the second group of cylinders is reversed.

17. The method according to any one of claims 1 to 16, characterized in that the combustion position is shifted thermodynamically unfavorable direction late to increase the exhaust gas temperature.

18. The method according to any one of claims 1 to 17, characterized in that the measures for raising the exhaust gas temperature during the warm-up phase are carried out until reaching the light-off temperature of the catalyst.

19. The method according to any one of claims 1 to 18, characterized in that the measures for raising the exhaust gas temperature in phase-lower engine load for temperature increase in the catalyst are applied.

20. The method according to any one of claims 1 to 19, characterized in that the measures for raising the exhaust gas temperature in dependence on the temperature of the internal combustion engine and / or the ambient temperature takes place.

21. The method according to any one of claims 1 to 20, characterized in that above and / or below a predefined total engine load and / or speed, the unequal distribution of the load and / or the air / fuel ratio between the groups of cylinders is deactivated.

22. A method for determining the loading state of a particulate filter of an internal combustion engine having at least one particle sensor whose measuring principle is based on the occurring voltage drop between two electrodes resulting on a sensor surface accumulating soot particles, characterized in that with the particle sensor in temporal succession several measurements are performed and that each measurement is interrupted upon reaching a defined voltage drop and the individual measurement periods are detected and after interrupting the measurement of the particulate filter is set in an electrical initial state, and that the individual measurement periods are added to a total duration and formed from the total duration a size proportional to the loading condition of the particulate filter becomes.

23. The method according to claim 22, characterized in that the particle filter is set by a burning process of the particles in the electrical initial state.

24. The method according to claim 22 or 23, characterized in that a first particle sensor upstream of the particulate filter and a second particle sensor downstream of the particulate filter is arranged and that the time duration of the second particulate sensor is set to reach a defined voltage drop ratio to the duration of the first particulate sensor until the defined voltage drop is reached and if a deviation of this ratio from a defined fluctuation range results in a malfunction of the particulate filter.

25. Device for determining the loading state of a particulate filter (102) of an internal combustion engine with at least one upstream of the Particle filter (102) arranged in the exhaust line first particle sensor (103), characterized in that downstream of the particle filter, a second particle sensor (103a) is arranged.