EP0732499B1 - Method for evaluating ignition pulses - Google Patents

Description

State of the art

The invention is based on methods for evaluation of ignition pulses from a spark-ignited internal combustion engine according to the genus of claims 1 or 2. From P. Paulsen's textbook, "Electronic Motor test equipment ", 1977, Franzis-Verlag (Munich), p. 207 and Figure 9.35 is a circuit of an ignition voltage oscilloscope known that a trigger device has a horizontal beam deflection at Triggers a trigger pulse. The trigger pulse is from an ignition pulse of a reference cylinder derived. The trigger threshold is with a trim potentiometer adjustable. The trim potentiometer will adjusted when adjusting the ignition voltage oscilloscope. A change in the trigger threshold in later operation is not scheduled.

The specification of a fixed threshold is sufficient if only trigger pulses from a reference cylinder are derived, with a reference to impulses other cylinder does not matter at first. A quantitative analysis of ignition pulses, in particular for ignition systems that have several independent ignition circuits included, sets the trigger threshold carefully ahead, on the one hand, unwanted interference suppressed and on the other hand all ignition pulses be recorded.

The invention has for its object a method for evaluating ignition pulses of a spark-ignited Internal combustion engine specify the one has high operational reliability.

The object is achieved by the in claim 1 specified features solved.

Advantages of the invention

According to the invention The method provides that the threshold or the amplitude is variable and that the threshold or amplitude is set to a value where the number of firing pulses detected within an interval defined by the distance between two successive Given pulses of a reference cylinder matches an expected number.

The method has the advantage that adaptive definition of the threshold above which the ignition pulses be evaluated, high operational reliability achieved on different ignition systems becomes. The increasingly used distributorless Ignition systems, some of which are independent Ignition circuits can contain deviations in the amplitudes of the ignition pulses between the individual Have ignition circuits. Even with such ignition systems is a reliable evaluation of Ignition pulses given by the variable threshold.

The method according to the invention enables Determining the threshold so that the relevant Ignition pulses just detected and glitches, their Amplitude is lower, can be suppressed. Glitches, their amplitude in the amount of the expected ignition pulses or above are from that recognized method according to the invention and it can a corresponding message will be submitted.

The criterion for determining the threshold at which the number of firing pulses detected within an interval defined by the distance between two successive Given pulses of a reference cylinder is match an expected number must presuppose that an ignition pulse of a reference cylinder is recorded separately. Based on the known Number of cylinders of the internal combustion engine is one Engine cycle fully set. Starting from the expected number of firing pulses compared to the actually detected firing pulse is the threshold can be reliably determined.

Advantageous further developments of the invention Procedures result from subclaims.

An advantageous embodiment of the invention The procedure sees a specification of the threshold as discrete levels. A particularly simple implementation the method according to the invention is by default of two stages possible, only one Switching between the two stages is required.

A further development of the method according to the invention stipulates that each encoder signal from different Is derived, one each separate threshold is assigned.

Another development provides that the signals detected by different sensors first be summarized and that the temporal successively expected pulses each have a separate one Threshold is assigned in chronological order.

Advantageous further training and improvements the method according to the invention result from further subclaims in connection with the following Description.

drawing

FIG. 1 shows a block diagram of a measuring device, which is connected to an ignition system, Figure 2 shows a time course of ignition pulses in one Ignition system and Figure 3 shows a block diagram of a Measuring device.

Description of exemplary embodiments

An ignition system 10 is shown in FIG a measuring device 11 is connected. Ignition system 10 and Measuring device 11 are separated from one another by dashed lines drawn.

The ignition system 10 contains two ignition coils 12, 13, the respective first primary connections 14, 15, second primary connections 16, 17, first secondary connections 18, 19 and second secondary connections 20, 21. The secondary connections 18, 19, 20, 21 of the ignition coils 12, 13 are each connected to a ground 22 Spark plugs 23, 24, 25, 26 connected. The first Primary connections 14, 15 of the ignition coils 12, 13 are each connected to a switch 27, 28 which in an ignition switching device 29 are arranged. The second primary connections 16, 17 of the ignition coil 12, 13 lead to an ignition switch 30, he the ignition system 10 with a battery 31 connected to ground 22 connects. The two switches 27, 28 in the ignition switching device 29 are also each connected to ground 22.

The one in the border of the ignition switchgear 29 points entered mean that the ignition switch 29 next to the two switches shown 27, 28 may contain further such switches. The points in the connecting line also mean of the second primary connections 16, 17 of the ignition coils 12, 13 that this line lead to further ignition coils can.

On the connecting lines between the switch 27 and the first primary connection 14 of the Ignition coil 12 and the switch 28 and the first primary connection 15 of the ignition coil 13 are contacts 32, 33 provided to the measuring lines 34, 35 are connected, which lead to the measuring device 11.

The measuring lines 34, 35 are with an evaluation arrangement 36 and connected to comparators 37, 38, respectively. The comparators 37, 38 each give Output signals 39, 40 to a signal processing Arrangement 41 from. The arrangement 41 in turn inputs Output signal 42 to the evaluation arrangement 36. The signal processing arrangement 41 continues to receive Input signals from a cylinder counter 43 and supplied by a reference signal generator 44. The Reference signal generator 44 is via a further measuring line 45 and via a further contact 46 with a line connected, which leads to the spark plug 26.

FIG. 2 shows a signal curve as a function of shown the time T that occurs in the ignition system 10. The voltage U is given at the contacts 32, 33 occurs. The waveform can initially either occur on the one contact 33. Farther it is possible to get the signals on the contacts 32, 33 to summarize, so that the one in FIG shown waveform from the superposition of two or more signals. The signal is called designated primary ignition signal.

With ignition switch 30 closed and at also closed switch 27, 28 flows in the Primary winding of the ignition coil 12, 13 a current with time increases. During this time, the Contact 32, 33 tapped voltage U a Potential on that except for an existing one Saturation voltage of the switches 27, 28 to ground potential lies. This in Figure 2 with the The number 50 entered is the time period Closing phase. Following the closing phase 50 opens the switch 27, 28, so that a swinging process of the flowing through the primary winding 12, 13 Current to a capacitor, not shown in Figure 1 takes place. A quick current change has one high induced voltage resulting on the secondary side the ignition coil 12, 13 occurs as an ignition voltage. Also occurs on the primary side of the ignition coil Ignition pulse whose amplitude reaches a value mainly due to the gear ratio the ignition coil between the primary and secondary windings given is. The four consecutive shown in Figure 2 Ignition pulses have the reference number 51, 52, 53, 54. Following the ignition pulse 51, 52, 53, 54 follows the burning phase 55, during which on the Spark plug 23, 24, 25, 26 there is a gas discharge. An opening phase follows the burning phase 55 56 on, during which the switches 27, 28 open is. With the beginning of the closing phase 50 there is a renewed one Ignition process initiated.

In Figure 2 are a first and a second threshold 57, 58 entered, the first threshold 57 from first, third and fourth firing pulses 51, 53, 54 and the second threshold 58 of all ignition pulses 51, 52, 53, 54 is exceeded. Furthermore, the temporal Distances between the individual ignition pulses 51, 52, 53, 54 entered. An interval starts there, where the amplitude of the firing pulses 51, 52, 53, 54 either the first threshold 57 or the second threshold 58 reaches and ends at the corresponding point of the subsequent impulse. As intersections of the ignition pulses 51, 52, 53, 54 with the sleepers 57, 58 each have a rising edge 59 of the ignition pulses 51, 52, 53, 54 are provided. A first time interval 60 lies between the first and the third ignition pulse 53, based on the first threshold 57. A second time interval 61 is between the third and fourth firing pulse 53, 54, also based on the first threshold 57. third, fourth and fifth temporal Distances 62, 63, 64 each lie between two successive ones Firing pulses 51, 52; 52, 53; 53, 54, based in each case on the second threshold 58.

Another block diagram of the measuring device is shown in FIG 11 shown. Matching parts in the figures 1 and 3 have the same reference numerals. The Test leads 34, 35 become a signal combining arrangement 70 fed an output signal outputs to a comparator 71, the Output signal 72 of a signal processing arrangement, 73 is supplied.

The method according to the invention is explained in more detail on the basis of the block diagrams shown in FIGS. 1 and 3 in conjunction with the signal curve shown in FIG. 2:
The ignition pulses 51, 52, 53, 54 occurring in the ignition system 10 are tapped at the contacts 32, 33. Instead of the galvanic connection of the measuring lines 34, 35 shown in FIG. 1 to the first primary connections 14, 15 of the ignition coils 12, 13, a capacitive or an inductive coupling is also possible. The ignition pulses 51, 52, 53, 54 can also be tapped at another point in the ignition system 10, for example on the secondary side of the ignition coils 12, 13. Instead of the primary-side ignition signal curve shown in FIG. 2, there is then, for example, a secondary-side ignition signal curve, although the characteristic ignition pulses 51, 52, 53, 54 are present.

The measuring lines 34 leading to the measuring device 11, 35 are usually first in a signal conditioning circuit, which is not entered in FIG. 1, prepared for further signal processing. For example can such a signal conditioning circuit a voltage divider, one Impedance converter or an amplifier circuit included. the signals then become the evaluation arrangement 36 fed a qualitative or performs quantitative analysis of the signals. Some of these Evaluations depend on the time. Such evaluations are, for example, the determination of Firing times of the individual cylinders in time Follow during an engine cycle. When evaluating in Dependence on the time is instead of that in FIG analog signal shown uses a digital signal, that by a defined level or a defined Edge devices for determining times starts or stops. The output signal 42 of the signal processing Arrangement 42 is such a signal, with which the evaluation arrangement 36 the time-related Makes evaluations. The signal 42 contains, for example Pulses that occur with each ignition pulse that occurs 51, 52, 53, 54 can be resolved. With that the signal shown in Figure 2 reliable pulses can be derived is a careful determination the threshold 57, 58 required, if exceeded by the ignition pulses 51, 52, 53, 54 each an impulse is triggered. According to the invention initially provided that the threshold 57, 58, variable is. It is considered equivalent to this measure that the threshold 57, 58 is fixed and that the amplitude of the signal is changed accordingly the arrangement of the stand mentioned at the beginning of the technique. The lying on the measuring lines 34, 35 Signals are fed to the comparators 37, 38, respectively. The signal processing arrangement 41 sets the Threshold 57, 58 initially fixed at a high value, depending on the determined time intervals and / or depending on the counting results is reduced.

According to the invention Method is provided that the threshold 57, 58 on a value is set at which the number of detected firing pulses 51, 52, 53, 54 within one Intervals that are determined by the spacing of two consecutive Impulse of the reference cylinder is given with an expected number. requirement for this procedure is the detection of ignition pulses a reference cylinder. In Figure 1 it is assumed that the spark plug 26 for ignition of the reference cylinder is provided. The measuring line 45 is therefore on the line leading to the spark plug 26 on the other Contacting 46 connected. Instead of shown galvanic connection is both a capacitive as well as inductive coupling possible. The further measuring line 45 carries the tapped signal to the reference signal generator 44, which has an output signal outputs to the signal processing arrangement 41. The Reference signal generator contains, for example, a voltage divider, an impedance converter and / or one Amplifier and a comparator. The reference signal generator 44 is also said to be a pulse-like signal the comparators 37, 38 deliver this by comparison of the input signal with a threshold arises. The Specifying a threshold is considerably easier here possible because the input signal is clearly too identify is. Usually the reference signal captured by a trigger gun that the in the secondary circuit flowing spark plug current or at least its Changes recorded.

The reference signal generator 44 gives rise to everyone for example, the first ignition pulse 51 a signal to the signal processing arrangement 41. So that Arrangement 41 the occurring within an engine cycle Ignition pulses can determine the number the cylinder to be communicated. For this, the cylinder payer is 43 provided, for example by a Input is controlled. The variable threshold 57, 58 becomes set during operation so that the signal processing Arrangement 41, starting from the first Firing pulse 51, four firing pulses count until the first ignition pulse occurs, which is the ignition pulse for the Reference cylinder corresponds. In the example is a four-cylinder Internal combustion engine has been adopted.

In the example shown in FIG. 1, it is assumed that two or more independent ignition circuits with the ignition coils 12, 13 are present, each with different measuring lines 34, 35 to separate Comparators 37, 38 lead. The threshold for everyone Comparator 37, 38 can be specified individually. Instead of of the separate comparators 37, 38 can according to FIG 3, a single comparator 71 can be provided, the one merged signal is fed. For signal merging the lying on the measuring lines 34, 35 Signals is the signal merging arrangement 70 provided an overlay of the Undertakes signals, for example as analog OR- Link can be realized.

The signal processing arrangement 73 differs from the arrangement 41 shown in Figure 1 with respect to Specification of the threshold for the comparator 71. Instead of specifying a uniform threshold preferably the specification of a temporally changing one Threshold is provided, the threshold being either for individual expected firing pulses or groups of Ignition pulses can be set. From previous ones Ignition pulses can be made in advance Threshold to be specified at a time after which the next ignition pulse is expected.

The inventive method can both be implemented in analog circuit technology as well as in run a microprocessor system. With a digital Realization in a microprocessor system the detected signals are first an analog / digital conversion then subjected us to the comparative operations and evaluation methods in the number range performed.

Claims (5)

1. Method for evaluating ignition pulses of a spark-ignition internal combustion engine, in which method the amplitude of the sensed pulses is compared with a prescribed threshold and only those impulses which exceed the threshold are evaluated, and in which ignition pulses of a reference cylinder are sensed, characterized in that the threshold (57, 58) or the amplitude is variable and in that the threshold (57, 58) or the amplitude is specified at a value at which the number of sensed ignition pulses (51, 52, 53, 54) coincides, within an interval which is given by the distance between two successive ignition pulses (51) of the reference cylinder, with an expected number.
2. Method according to Claim 1, characterized in that the threshold (57, 58) can be prescribed in increments.
3. Method according to Claim 2, characterized in that two increments (57, 58) are provided.
4. Method according to one of the preceding claims, characterized in that the ignition pulses (51, 52, 53, 54) are sensed by separate devices (32, 34; 33, 35), and in that each of these devices (32, 34; 33, 35) is assigned a separate threshold (57, 58).
5. Method according to Claim 4, characterized in that the pulses which are output by a plurality of devices (32, 34; 33, 35) are combined, and in that the threshold (57, 58) is switched over in chronological sequence before the expected ignition pulse (51, 52, 53, 54).

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