EP0615582A1

EP0615582A1 - Ignition system for an internal combustion engine.

Info

Publication number: EP0615582A1
Application number: EP92923383A
Authority: EP
Inventors: Ulrich Mayer; Peter Kaltenbrunn; Wolfgang Hoeptner; Karsten Mischker
Original assignee: Robert Bosch GmbH
Current assignee: Robert Bosch GmbH
Priority date: 1991-12-05
Filing date: 1992-11-12
Publication date: 1994-09-21
Anticipated expiration: 2012-11-12
Also published as: EP0615582B1; ES2085654T3; WO1993011356A1; DE59205878D1; US5490489A; JPH07501594A; JP3231324B2; DE4140147A1

Abstract

Système d'allumage pour moteurs à combustion interne comportant un circuit de contrôle (9) servant à déclencher les mesures d'urgence nécessaires en cas de ratés d'allumage, pour protéger le catalyseur. A cet effet, le système d'allumage comprend un disposif d'évaluation (10) qui soumet le signal de diagnostic de l'allumage (ZÜNDOK) à une pondération statistique et déclenche les mesures d'urgence nécessaires en cas de dépassement d'un seuil prédéféni de la valeur de diagnostic de l'allumage pondérée (ZÜNTAB). L'évaluation se poursuit de sorte qu'après sous-dépassement ultérieur du seuil de raté (AFSDZU) un rétablissement soit reconnu et que les mesures d'urgence soient levées.Ignition system for internal combustion engines comprising a control circuit (9) for initiating the necessary emergency measures in the event of misfiring, to protect the catalyst. For this purpose, the ignition system comprises an evaluation device (10) which subjects the ignition diagnostic signal (ZÜNDOK) to a statistical weighting and initiates the necessary emergency measures in the event of a violation of a Preset threshold of the weighted ignition diagnostic value (ZÜNTAB). The assessment is continuing so that after the subsequent failure of the failure threshold (AFSDZU) a recovery is recognized and emergency measures are lifted.

Description

Ignition system for internal combustion engines

State of the art

The invention relates to an ignition system for internal combustion engines according to the preamble of the main claim. An ignition circuit monitoring system is already known for ignition systems, in which an ignition current sensor generates a sensor signal with each ignition, which is stored in a memory and read out after each ignition. The contents of the memory in turn are reset before each next ignition, so that an ignition failure is detected if there is no sensor signal. However, this ignition circuit monitoring offers no possibility of detecting the frequency of misfires or the load on the ignition system due to the misfires. For example, a single misfire that is followed by a very large number of correct ignitions is negligible, but the same number of misfires as correct ignitions is disadvantageous.

Advantages of the invention

In contrast, the ignition system according to the invention with the characterizing features of the main claim has the advantage that an ignition diagnosis signal is detected and evaluated cylinder-selectively. In this case, the ignition diagnostic signal is statistically weighted in an evaluation device for each cylinder after an ignition, so that the threshold for initiating emergency measures to protect the catalytic converter is not exceeded until a certain number of misfires occurs in a predeterminable time. Another advantage is that the ignition in the cylinder does not have to be interrupted, so that this cylinder has the possibility of healing.

Advantageous further developments and improvements of the ignition system specified in the main claim are possible through the measures listed in the patent claims. It is particularly advantageous that, in order to form the weighted ignition diagnosis value in the event of a faulty ignition, an amount which is greater than 1 is added to the previous diagnosis value and the value 1 is subtracted in the case of a correct ignition. The value which is added in the event of a faulty ignition is determined in the application for each engine type. The threshold from which emergency measures are initiated is also specified in the application. Ultimately, it should also be mentioned as an advantage that the weighted ignition diagnosis value (ZÜNTAB) is limited to this when an applicable maximum value (AFXDZU) is reached and the number of correct ignitions via the distance between the error threshold (AFSDZU) and the maximum value (AFXDZU) until a healing detection of a previously defective cylinder is established.

drawing

Embodiments of the invention are shown in the drawing and explained in more detail in the following description. 1 shows the basic structure of an ignition system for detecting the ignition diagnosis signal, FIG. 2 shows an ignition diagnosis signal, FIG. 3 shows the program sequence for weighting the ignition diagnosis signal and Figure 4 is a graph of the weighted ignition diagnostic value for a cylinder.

Description of the embodiments

FIG. 1 shows a distributorless ignition device consisting of a microprocessor 1, ignition coils 2 and 3, although more ignition coils can also be connected, which is indicated by the dashed lines, spark plugs 4 and 5, ignition transistors 6 and 7, an ignition current sensor 8, a monitoring circuit 9 and an evaluation device 10 arranged in the microprocessor.

The mode of operation of this circuit arrangement will be described below. The primary windings of the ignition coils 2 and 3 are connected to the battery voltage U, so that when the ignition transistors 6 and 7 are activated by the microprocessor 1, a charging current flows in the corresponding primary winding of the ignition coils 2 and 3. The closing times of the ignition transistors are determined by an ignition computer contained in the microprocessor 1. To trigger the ignition, the ignition transistor is brought into the blocking state, so that a high voltage is generated in the secondary windings of the ignition coils, which then causes an ignition spark at the spark plugs. In the secondary circuit of each ignition coil, an ignition current sensor 8 is arranged between the output of the secondary winding and the ground in such a way that all the secondary windings are previously combined in a point 11. The ignition current sensor 8 thus detects the signals of all ignition coils. To detect an ignition signal, it is also possible, for example, to detect the operating voltage transformed on the primary side. The ignition signal detected by the ignition current sensor 8 is passed on to a monitoring circuit 9. The output of the monitoring circuit is set to high level by the microprocessor 1 before each ignition. With each ignition that has run properly, the ignition current sensor 8 carried ignition signal of the output 12 of the monitoring circuit switched from high to low. If no ignition has been triggered or the ignition has not proceeded properly, the output 12 of the monitoring circuit 9 remains at a high level. An ignition diagnosis signal is thus present at the output 12 of the monitoring circuit 9, which is fed to the evaluation device 10 of the microprocessor 1. The evaluation circuit 10 can assign the ignition diagnosis signal to the corresponding cylinder in each case by means of a comparison with the ignition sequence. A circuit is also conceivable in which the output 12 of the monitoring circuit 9 remains high after a correct ignition and a faulty ignition causes a switch to low. Ultimately, it is also possible to set output 12 to low before each ignition and to switch to high if the ignition is correct or to remain low.

FIG. 2 shows how the ignition diagnosis signal (ignition OK) is formed. The diagram shows the crankshaft angle (KW) of the internal combustion engine. The microprocessor 1 sets the ignition diagnosis signal (Zünd OK) to 1 (high) before each ignition (Z), so that this ignition diagnosis signal has a predetermined level at the time of ignition (Z). If an ignition now takes place in cylinder 1 (ZI), the ignition diagnosis signal (ignition OK) is set to zero by the signal of the ignition current sensor 8. If no ignition signal was transmitted by the ignition current sensor 8, as in the present case with cylinder 3 (Z3), the ignition diagnosis signal remains at the predetermined level (high). This creates the typical digital ignition diagnosis signal sequence (Zünd OK). The ignition diagnosis signal can be assigned to a cylinder at each measuring point (MP) via the signal sequence. The malfunctioning cylinder can thus be diagnosed.

FIG. 3 shows the program flow chart in the microprocessor 1 for the statistical evaluation of the ignition diagnosis signal (Zünd OK) and is to be explained below together with FIG. 4. Figure 4 shows the statistical weighting of the cylinder-selective

Ignition diagnostic signals (Zünd OK) for a cylinder, as it runs in the program shown in Figure 3. At the beginning of the method in FIG. 3, a query 20 checks whether an evaluation of the signals is possible. It is checked, for example, whether the battery voltage U has the required level, since it is direct

B after start U is too small and so no signals are detected. B

If the answer to this question is yes, that is to say an evaluation is possible, the cylinder is selected in a work step 21, the ignition diagnosis signal (ignition OK) of which is to be weighted. In the following work step 22, the ignition diagnosis signal (ignition OK) of this cylinder (Z) is now used for evaluation after the ignition point (Z). A query 23 checks whether the ignition diagnosis signal (ignition OK) is zero. If this is the case, ie the ignition in the cylinder was OK, the value 1 is subtracted from the weighted ignition diagnosis value (ZÜNTAB) in a work step 24. A query 25 is then used to check whether ZÜNTAB <0. If this is the case, the weighted ignition diagnosis value (ZÜNTAB) for this cylinder is reset to zero in step 26. The no output of query 25 and work step 26 lead to query 27. If query 23 was answered with no, ie the ignition diagnosis signal was not correct for this cylinder, the weighted ignition diagnosis value ( ZÜNTAB) increased by an amount (DAFDZU). This amount (DAFDZU) is specified in the application for each engine type. After this step 28, query 29 checks whether the weighted ignition diagnosis value (ZÜNTAB) has exceeded a maximum permissible limit value (AFXDZU). If this is the case, the weighted ignition diagnosis value is limited to this maximum permissible value (AFXDZU) in step 30. The no output of query 29 and work step 30 also lead to query 27. In query 27 it is now checked whether the weighted ignition diagnosis value (ZÜNTAB) is greater than one Threshold (AFSDZU) is above which emergency measures to protect the catalytic converter should be initiated. This threshold (AFSDZU) is defined in the application for each engine type and can also be changed depending on the operating conditions of the engine. The threshold (AFSDZU) is generally chosen to be greater than zero and less than or equal to the maximum permissible value. If this threshold (AFSDZU) was exceeded by the weighted ignition diagnosis value (ZÜNTAB), cylinder-selective emergency measures, such as switching off the injection in this cylinder, are initiated in work step 31. Then, in step 32, global measures for protecting the catalytic converter, such as switching off the lambda control, are carried out. The no output of query 27 leads to work step 33, by which no cylinder-selective emergency measures are initiated or emergency measures previously activated in this cylinder are withdrawn. In the subsequent query 34, it is checked whether all cylinders (Z-Z) are working properly. If this is the case (yes output), the global emergency measures are also withdrawn in step 35. However, if a cylinder should still work incorrectly, the global emergency measures remain activated or are activated. In step 36, the ignition diagnosis signal is then reset and, for example, stored in a memory. In a work step 37, the cylinder number is increased by one and the ignition diagnosis signal is weighted for this cylinder. By storing the ignition diagnosis signal in a memory, it is possible to retrospectively check the function of the ignition system when visiting a workshop and to carry out any necessary repairs.

The ignition diagnosis signal (ignition OK) is shown in FIG. It can be clearly seen that in the case of a faulty ignition (IGNIT OK = 1), the weighted ignition diagnosis value (IGNTAB) is increased by the amount (DAFDZU) in the example by 4 and decremented by 1 if the ignition is correct. The limitation of the weighted ignition diagnosis value (ZÜNTAB) to a permissible maximum value (AFXDZU) and to the minimum value 0 can also be seen. This diagram also shows very well that during the time the permissible value was exceeded Threshold (AFSDZU) an error is detected in this cylinder, so that corresponding cylinder-selective and global emergency measures are initiated and at the same time an error message is given to the driver.

The distance between the maximum value (AFXDZU) and the permissible threshold (AFSDZU) determines the number of correct ignitions that must occur in succession on the cylinder concerned until the ignition defect is recognized as healing.

Claims

Expectations

1. Ignition system for internal combustion engines with a monitoring circuit for generating a digital ignition diagnosis signal in such a way that a central control unit of the ignition system sets the ignition diagnosis signal to a first predetermined level before each ignition and the ignition Diagnostic signal either after every proper or after every improper ignition, the ignition being monitored by a sensor arranged in the ignition circuit, switching to a second level depending on the sensor signal, characterized in that an evaluation device detects the respective level of each ignition diagnostic Signals (Zünd OK) cylinder selectively recorded and for each cylinder carries out a statistical weighting with previous ignition diagnosis signals and that such a weighted ignition diagnosis value (ZÜNTAB) when a predetermined error threshold (AFSDZU) is exceeded, emergency measures for protection initiates a catalyst.

2. Ignition system according to claim 1, characterized in that the evaluation device increases the weighted ignition diagnosis value (ZÜNTAB) for each faulty ignition by an amount (DAFDZU) and decrements it by 1 in the event of a proper ignition.

3. Ignition system according to claim 2, characterized in that the amount (DAFDZU) is greater than 1 in the event of faulty ignition.

4. Ignition system according to one of the preceding claims, characterized gekenn¬ characterized in that the error threshold (AFSDZU) for each engine type in the application can be set to values> 1.

5. Ignition system according to one of the preceding claims, characterized gekenn¬ characterized in that the ignition diagnosis value (ZÜNTAB) is limited to an applicable maximum value (AFXDZU).

6. Ignition system according to one of the preceding claims, characterized gekenn¬ characterized in that the distance of the maximum value (AFXDZU) to the Fehler¬ threshold (AFSDZU) determines the number of correct ignitions until detection of an error healing.

7. Ignition system according to one of the preceding claims, characterized gekenn¬ characterized in that the fault diagnosis, the ignition diagnosis value (ZÜNTAB) leads to the resetting of all emergency measures when falling below the fault threshold (AFSDZU).

8. Ignition system according to one of the preceding claims, characterized gekenn¬ characterized in that when the error threshold (AFSDZU) a storage of the error in the vehicle and an error display is provided for the driver.

9. Ignition system according to one of the preceding claims, characterized gekenn¬ characterized in that the injection of the cylinder in question is interrupted and the lambda control is switched off in the event of a fault.