EP0466849A1

EP0466849A1 - Process for associating combustion defects with a cylinder in an internal combustion engine

Info

Publication number: EP0466849A1
Application number: EP19910901682
Authority: EP
Inventors: Ernst Wild
Original assignee: Robert Bosch GmbH
Current assignee: Robert Bosch GmbH
Priority date: 1990-02-08
Filing date: 1991-01-09
Publication date: 1992-01-22
Also published as: JPH04505490A; DE4003752A1; KR920701640A; WO1991012422A1

Abstract

Un procédé permet d'attribuer des défauts de combustion à un cylindre d'un moteur à combustion interne ayant au moins un tuyau d'échappement agencé entre le site collecteur d'un collecteur de gaz d'échappement et une sonde lambda. Selon le procédé, (a) le volume de gaz d'échappement, qui dépend de la charge et du régime pendant l'aspiration, est déterminé pour chaque course d'expulsion d'un cylindre; (b) lorsqu'un cylindre expulse des gaz d'échappement, on suppose que le volume calculé de gaz d'échappement pénètre dans le site collecteur du collecteur correspondant dans le tuyau d'échappement; (c) les volumes qui pénètrent dans le tuyau d'échappement par le site collecteur sont additionnés jusqu'à atteindre ou dépasser à peine le volume qui correspond au volume du tuyau d'échappement compris entre le site collecteur et la sonde; (d) on détermine, sur la base de la correspondance entre les cylindres et les volumes de gaz d'échappement qui pénètrent successivement dans le tuyau d'échappement, à quel cylindre correspond le volume ayant rempli par addition la condition ci-dessus; (e) le signal émis par la sonde lambda est évalué; (f) lorsque le signal de la sonde indique un écart, par rapport à la valeur moyenne de lambda, supérieur à une valeur seuil, le défaut à l'origine de cet écart est attribué au cylindre dont les gaz d'échappement passent par la sonde, selon le procédé de détermination de l'étape (d). Ce procédé peut être mis en oeuvre sans détecteurs spéciaux. Etant donné que l'on additionne les volumes individuels de gaz d'échappement dépendants de la charge et du régime pendant l'aspiration, le procédé donne des indications fiables même lors de transitions instationnaires.A method for assigning combustion defects to a cylinder of an internal combustion engine having at least one exhaust pipe arranged between the manifold site of an exhaust gas manifold and a lambda probe. According to the method, (a) the volume of exhaust gas, which depends on the load and the speed during suction, is determined for each expulsion stroke of a cylinder; (b) when a cylinder expels exhaust gas, it is assumed that the calculated volume of exhaust gas enters the manifold site of the corresponding manifold in the exhaust pipe; (c) the volumes which enter the exhaust pipe through the collector site are added together until they reach or barely exceed the volume which corresponds to the volume of the exhaust pipe between the collector site and the probe; (d) determining, on the basis of the correspondence between the cylinders and the volumes of exhaust gas which successively enter the exhaust pipe, to which cylinder corresponds the volume having fulfilled by addition the above condition; (e) the signal emitted by the lambda probe is evaluated; (f) when the sensor signal indicates a deviation from the average lambda value greater than a threshold value, the fault causing this deviation is attributed to the cylinder whose exhaust gases pass through the probe, according to the determination method of step (d). This method can be implemented without special detectors. Since the individual volumes of exhaust gas dependent on load and speed are added up during aspiration, the method gives reliable indications even during unsteady transitions.

Description

Method for assigning combustion errors to a cylinder of an internal combustion engine

The invention relates to a method for assigning combustion errors to a cylinder of an internal combustion engine. Such methods are of interest because they make it possible to selectively interrupt the fuel supply to a cylinder that is working incorrectly. This prevents an unburned mixture from being expelled. The unburned mixture burns in the catalyst, which today usually belongs to an internal combustion engine. Such post-combustion easily leads to the destruction of the catalyst by overheating. In individual cases, vehicle fires also occur. Combustion errors are particularly misfires. However, this also includes errors according to which poor combustion quality is caused by incorrect fuel metering, in particular by a leaky injection valve.

State of the art

Combustion errors can be detected very reliably if the combustion process in each cylinder is carried out immediately with the aid of a sensor, e.g. B. a ticht- or a Druckseπsors, is monitored. However, such sensors are very expensive, which is disadvantageous for the practical use of the associated methods. A similar disadvantage applies to methods which attempt to detect misfires. Special inductive sensors are also required for this, which determine whether an ignition current flows in a respective ignition cable. , Additionally disadvantageous is in such methods that they are unable to detect misfires due to a fault other than an ignition fault.

Processes that get by with simpler sensors are less costly, and additionally only one sensor for each exhaust pipe, in which the exhaust gas is collected by a plurality of exhaust manifolds. These are methods that determine temperature or pressure fluctuations. Even in the case of misfire detection alone, these methods do not work too reliably. Evaluation results are even more unreliable when it comes to specifically assigning misfires to a cylinder.

There has long been the problem of specifying a method for assigning combustion misfires for a cylinder of an internal combustion engine that works reliably and that does not require sensors that are specifically required for the method.

Presentation of the invention

The method according to the invention for assigning combustion errors to a cylinder can be used in internal combustion engines which have at least one exhaust pipe between an exhaust manifold collection point and a lambda probe. It is characterized in that a) the exhaust gas volume, which is dependent on the load and speed during the intake process, is determined for each exhaust cycle of a cylinder, b) when a cylinder emits exhaust gas, it is assumed that the calculated exhaust gas volume at the collection point by the associated company ¬ towards the manifold enters the exhaust pipe, c) the volumes that have entered the exhaust pipe at the collection point are added up until the volume is reached or just exceeded that corresponds to the exhaust pipe volume between the collection point and the probe, d) with the help the cylinder-assigned sequence of the exhaust gas volumes that have entered the exhaust pipe is determined Which cylinder belongs to that volume for which the above-mentioned sum condition has just been fulfilled, e) the signal emitted by the lambda probe is evaluated, f) and when the probe signal deviates from the lambda mean by more than a threshold value indicates that the error causing this deviation is assigned to the cylinder whose exhaust gas, according to the determination of step d, is just flowing past the probe.

It is pointed out that the method steps mentioned do not necessarily have to be carried out in the order selected above. In particular, steps c and d can only be carried out if the evaluation of the signal from the lambda probe shows that ^{"there is} a greater lambda deviation. In order to be able to carry out step c in this case, however, the volume values of ins Exhaust pipe quantities that have entered the exhaust pipe can be stored so that they are available for summation It is sufficient here to store the values for as many volumes as possible in the exhaust pipe volume between the collection point and the lambda sensor, for the maximum volume, namely at the lowest exhaust gas temperature Find.

The exhaust gas volume according to step a is advantageously determined using a table, since this procedure is faster than if the volume is calculated using an arithmetic relationship between the respective load and speed during the intake process.

There are a large number of engine types that have several exhaust pipes, in particular two, between a collection point and a lambda sensor. This is typically the case with six-cylinder engines with two cylinder banks. The manifolds of d-en three cylinders of a bank each lead to a collection point in an exhaust pipe (downpipe). The two exhaust pipes are then brought together to form a common main exhaust pipe. Shortly before each exhaust pipe opens into the main exhaust pipe there is a lambda probe. With such Internal combustion engines with a plurality of exhaust pipes between a respective collecting point and a lambda probe for each of the exhaust pipes, it is advantageous to carry out the method according to the invention separately for each exhaust pipe.

Because the method according to the invention works with the signal of the lambda probe, it can not only assign combustion misfires to a cylinder, but also other errors of the type described at the beginning.

drawing

Figure 1 is a schematic representation of an internal combustion engine with four exhaust manifolds and an exhaust pipe, in which exhaust gas volume are shown.

2 table to illustrate the relationships between the consecutive number of an exhaust gas volume in the exhaust pipe, the associated cylinder number, the associated volume and the associated sum of volumes; and

3 shows a schematic representation of an internal combustion engine with two exhaust pipes between an exhaust manifold collecting point and a lambda probe.

Description of exemplary embodiments

1 shows an internal combustion engine 10 merely as a rectangular block, which has four cylinders 1-4, each of which is symbolized by a circle. An exhaust manifold 11.1-11.4 leads from each cylinder to an exhaust pipe 12. The point where the exhaust manifold 11.1-11.4 opens into the exhaust pipe 12 is referred to below as a collection point 13. Downstream of the collection point 13, a lambda probe 14 projects into the exhaust pipe 12. The section of the exhaust pipe between the collection point 13 and the lambda probe 14 is important for the following.

It is assumed that the cylinder 1 in the internal combustion engine 10 is malfunctioning in such a way that it has misfire. The exhaust gas volume emitted by him then contains a higher oxygen content than those exhaust gas volumes ejected by the other cylinders. The high oxygen leads to a voltage drop at the lambda probe 14, which falls below a threshold value in relation to the average la voltage voltage. "It is desirable to be able to determine to which cylinder the exhaust gas volume that causes a voltage dip at the lambda probe 14 belongs. How this can be determined will now be explained in more detail.

With each exhaust stroke of a cylinder, a certain exhaust gas volume enters the associated exhaust manifold. If there is the same pressure in the entire exhaust system, which is assumed for the following, exactly the same volume enters the exhaust pipe 12 at the collection point 13, which is expelled from a cylinder, regardless of how long each of the Exhaust manifold 11.1 - 11.4 is. Through the exhaust pipe, successive exhaust volumes flow from the individual cylinders. The cylinder-assigned sequence of the volumes corresponds exactly to the firing sequence ^"of the cylinders. The exemplary embodiment is an engine with the firing sequence 1-3-4-2. The individual volumes flow past the lambda probe 14 in this sequence.

The volume value of each exhaust gas volume or exhaust gas packet from a cylinder depends on the intake air mass and the exhaust gas temperature. The intake air mass is known in internal combustion engines which have a lambda probe, since it is the size to which fuel must be metered in such an amount that a desired load value is established. The exhaust gas temperature, in turn, can be determined from the load and speed, likewise variables that are available in methods for lambda control. In the exemplary embodiment, the volume values for individual exhaust gas packs for stationary operating states were determined as a function of speed and load and entered in a table. Volume values, again dependent on the speed and load, were read from this table when the method described here was carried out. For the exemplary embodiment, it was found that between the collection point There is space for a maximum of 12 exhaust gas packs 13 and the exhaust gas probe 14, namely in idle mode, where each exhaust gas pack has a minimal volume. At full load there is only space for about 5 to 6 exhaust gas packets between the collection point and the probe.

2 contains data on a total of 12 exhaust gas volumes or exhaust gas packets. This is because, as just noted, there is a maximum of 12 packages between the collection point 13 and the probe 14. In the operating state illustrated by FIG. 1, on which the table according to FIG. 2 is based, however, there are only 7 packets in the exhaust pipe 12 between the collection point and the lambda sensor. An exhaust gas volume from cylinder 1 is currently flowing past the probe itself. This is the consecutive volume number 7. In the direction of the collection point 13, the other exhaust gas volumes follow the ignition sequence 1-3-4-2. A volume has just entered the exhaust pipe 12, which corresponds to the volume that the cylinder with the number 4 has just expelled. How large this volume is, is determined with the help of the above-mentioned volume table, with the help of values of load and speed, which applied to the associated intake process. In the table according to FIG. 2, this volume has the value 42. This volume is based on the total volume of the exhaust pipe 12 between the collection point 13 and the lambda sensor 14.

Q miert which volume is in turn set to the value 2 = 256. From the sums of the volumes listed in the table on the far right in FIG. 2 it can be seen that the volume sum 256 has not yet been reached for the first six volumes, but this number including the seventh volume has just been exceeded is. The sum including the seventh volume is 270. This is made up of the volumes 42, 41, 40, 39, 36, 36, 36. The engine was initially in a steady state (volumes 36), whereupon the load was increased (increasing volumes 39, 40, 41, 42).

In order to be able to assign combustion misfires specifically to a cylinder using the method described above, this must be done continuously load and engine speed determine which exhaust gas volume a respective cylinder will emit. The individual volume values must be stored permanently for at least so many cylinders that, even at low speed and load, there are so many values available that together they result in at least that volume of the exhaust pipe 12 that exists between the collection point

13 and the probe 14 is located. The summation of the volumes can

_ \ take place continuously or only when the lambda probe 14 indicates a misfire due to a high oxygen content in the exhaust gas. It then flows ge ade exhaust gas from that cylinder past the lambda probe 14, the sum of the volumes on one

Fills in the value of the volume of the exhaust pipe 12 between the

Collection point 13 and the probe 14 corresponds.

As indicated above, the exhaust gas volumes for each individual cylinder are determined from a table which was obtained on the basis of measurements during stationary operation of an internal combustion engine. Now, however, it is the case that, in the event of a sudden increase in load, the exhaust gas expelled from a cylinder in the exhaust gas pipe 12 cools somewhat more than in the stationary case with a higher load. Conversely, in the event of a sudden reduction in load, the exhaust gas that is expelled is heated up a little further, since the exhaust system is still strongly warmed up by operation previously under a higher load. However, it has been found that the consequent V ^* t} ltnπenänderungen Brenn¬ in conventional combustion engines do not bring significant errors. It should be noted in particular that in all types of methods for assigning combustion misfires, not a single measurement result is considered sufficient to make the assignment, but the measurement results are averaged in some way, e.g. B. by determining how often a misfire is detected for a particular cylinder within a predetermined number of ignitions. This means that a single measurement error does not have any effect. Fig. 3 shows schematically an internal combustion engine with two Zylin¬ derblöcken 10.1 and 10.2 and two respectively associated Abgasroh¬ ren 12.1 and 12.2, the ^'e iner to respective ones of two Sammelstel¬ start len 13.1 and 13.2 and the common gas pipe in a Hauptab¬ 15 mouth. Shortly before the mouth, a lambda probe 14.1 and 14.2 is inserted into each of the two exhaust pipes 12.1 and 12.2. A process is carried out separately for each of the two exhaust pipes 12.1 and 12.2, as was explained with reference to FIGS. 1 and 2 for the exhaust pipe 12 between the collection point 13 and the lambda sensor 14.

The method described allows a reliable assignment of misfires to a cylinder without the need for a special sensor. The fact that individual volumes are summed up, each of which is determined as a function of load and speed during the suction process, provides the method with reliable information even with transient transitions.

The exemplary embodiments relate to the allocation of misfires to a cylinder. If the combustion fault is not a misfire but an over-rich mixture due to a leaking injection valve, the lambda probe detects voltage deviations that are a threshold value above the average lambda voltage value instead of below the lambda voltage value (high voltage = low lambda value = rich). This deviation is assigned to a cylinder in the manner described above.

Claims

1. Method of assigning combustion errors to one

Cylinder of an internal combustion engine which has at least one exhaust pipe between an exhaust manifold collection point and a lambda probe, characterized in that a) for each exhaust cycle of a cylinder, the exhaust gas volume dependent on the load and speed during the intake process is determined b) when a cylinder emits exhaust gas , is assumed because the calculated exhaust gas volume at the collection point enters the exhaust pipe from the associated manifold, c) the volumes that have entered the exhaust pipe at the collection point are added up until the volume reached or just exceeded that between the exhaust pipe volume and Collection point and the probe corresponds, d) with the help of the cylinder-assigned sequence of the exhaust gas volumes that have entered the exhaust pipe, it is determined to which cylinder the volume for which the above-mentioned sum condition has just been met, e) the signal emitted by the lambda probe is evaluated, f) and then, if the probe signal shows a deviation by more than a threshold value from the lambda mean value, the error causing this deviation is assigned to the cylinder whose exhaust gas, according to the determination of step d, is just flowing past the probe.

2. The method according to claim 1, characterized in that the determination of the exhaust gas volume according to step a is carried out using a table.

3. The method according to any one of claims 1 or 2, characterized gekenn¬ characterized in that it is carried out separately for each of the exhaust pipes in an internal combustion engine with a plurality of exhaust pipes between a respective collection point and a respective lambda probe.