EP0540878B1 - Method for evaluating ignition pulses - Google Patents

Description

The invention is based on methods for Evaluation of ignition pulses from a spark-ignited Internal combustion engine according to the genus of Claim 1. From P.'s reference book PAULSEN, "Electronic engine test equipment", 1977, Franzis-Verlag (Munich), p. 207 and picture 9.35 is a circuit of an ignition voltage oscilloscope known. which has a trigger device, which is 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 adjustable with a trim potentiometer. The Trim potentiometer is used when adjusting the Ignition voltage oscilloscope adjusted. A change the trigger threshold in later operation is not intended.

The specification of a fixed threshold is sufficient if only trigger pulses from a reference cylinder be derived, taking a temporal First, reference to pulses from other cylinders doesn't matter. A quantitative analysis of Ignition pulses, especially in ignition systems, the contain several independent ignition circuits careful setting of the trigger threshold ahead, on the one hand, unwanted interference suppressed and on the other hand all ignition pulses be recorded.

The invention is based on the object Process for evaluating ignition pulses spark-ignited internal combustion engine specify which has a high level of operational reliability.

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

Advantages of the invention

According to an embodiment of the invention The procedure provides that the Threshold is variable and that the threshold is on a value is set at which the temporal Distances of at least two successive ones Firing pulses within a predetermined ratio lie.

The method has the advantage that through an adaptive determination of the threshold, above which the ignition pulses are evaluated a high level of operational reliability in different Ignition systems is reached. The increasing Dimensions used distributorless ignition systems that some contain several independent ignition circuits, can deviations in the amplitudes the ignition pulses between the individual ignition circuits exhibit. Even with such ignition systems is a reliable evaluation of ignition pulses given by the variable threshold.

The method according to the invention enables the determination of the threshold such that the relevant Ignition pulses just detected and interference pulses, whose amplitude is lower, suppressed become. Glitches, their amplitude in height the expected ignition pulses or above are from the inventive method recognized and there may be a corresponding message be delivered.

The evaluation of the time intervals at least two successive impulses to Setting the threshold assumes that the time intervals of the expected ignition pulses are within a predetermined ratio. At constant engine speed the time intervals are the same, accordingly a ratio of 1: 1. The specification of a Range of the ratio, for example of 1: 0.7 to 1: 1.1 enables the consideration of Acceleration processes. One area boundary corresponds to the ratio of: 1: 0.7 one positive acceleration and the other Zone of 1: 1.1 negative acceleration. The information provided so far apply only to symmetrical motors where the top dead centers of the cylinders related to a crankshaft rotation are evenly distributed. At unbalanced motors must be offset top dead center, a time offset of the Firing times of successive cylinders corresponds when determining the ratio be taken into account. With a normalization of the time intervals between successive Ignition processes can also occur with asymmetrical Motors a ratio of 1: 1 at constant Speed are taken as a basis. Instead of normalization can of course do that too actual ratio at constant speed Starting point can be selected, which then from 1: 1 deviates, with the range of predefined ratio changes accordingly.

Advantageous further developments of the invention Procedures result from subclaims.

According to one Execution example is the review of the Ratio of the time intervals at least two successive pulses and then the result is through evaluation the number of ignition pulses within one Motor cycle checked. According to one A variant of an exemplary embodiment is firstly the determination of the Number of firing pulses within the Ignition pulses of the reference cylinder given interval provided, followed by the result by evaluating the time intervals successive impulses checked becomes.

In the embodiment is another Increased operational security by expanding the plausibility checks.

An advantageous embodiment of the invention The procedure provides a requirement of Threshold as discrete steps. A special one simple implementation of the invention Procedure is by default of two stages possible, only switching between two levels is required.

A further development of the invention The method provides that each encoder signal that is derived from different donors, each a separate threshold is assigned.

Another development provides that the signals detected by different sensors first be summarized and that the pulses expected one after the other in each case a separate threshold in chronological order is assigned.

An embodiment of the invention Procedure provides that to set the threshold the shortest detected distances between successive Impulses are used. With this measure it is ensured that the ignition pulses can also be fully detected if periodically recurring ignition pulses occur, their amplitude compared to the other ignition pulses is increased.

Advantageous further training and improvements of the method according to the invention arising from further subclaims with the following description.

drawing

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

An ignition system 10 is shown in FIG is connected to a measuring device 11. Ignition system 10 and meter 11 are dashed lines from each other drawn separately.

The ignition system 10 contains two ignition spikes 12, 13, the first primary connections 14, 15, second primary connections 16, 17, first secondary connections 18, 19 and second secondary connections 20, 21 have. The secondary connections 18, 19, 20, 21 of the ignition coils 12, 13 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 are arranged in an ignition switching device 29 are. The second primary connections 16, 17 of the Ignition coils 12, 13 lead to an ignition switch 30, the ignition system 10 with a Ground 22 connected battery 31 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 shown Switches 27, 28 contain further such switches can. The points in the connecting line also mean the second primary connections 16, 17 of the ignition coils 12, 13 that this line too can lead to further ignition coils.

On the connecting lines between the Switch 27 and the first primary terminal 14 of the Ignition coil 12 and switch 28 and the first Primary terminal 15 of the ignition coil 13 are in each case contacts 32, 33 are provided to the Test lines 34, 35 are connected to the Guide measuring device 11.

The measuring lines 34, 35 are with an evaluation arrangement 36 and each with comparators 37, 38 connected. The comparators 37, 38 give each output signals 39, 40 to a signal processing Arrangement 41 from. The arrangement 41 in turn outputs an output signal 42 to the evaluation arrangement 36 from. The signal processing Arrangement 41 also receives input signals from a cylinder counter 43 and a reference signal generator 44 fed. 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.

In Figure 2, a waveform is dependent shown by the time T in the ignition system 10 occurs. The voltage U is given to the Contacts 32, 33 occurs. The waveform can either make contact at first 32 or at the other contact 33 occur. It is also possible to turn on the signals summarize the contacts 32, 33, so that the waveform shown in Figure 2 from the Superposition of two or more signals arises. The signal is called the primary ignition signal designated.

With the ignition switch 30 and with switch 27, 28 also closed in the primary winding of the ignition coil 12, 13 Electricity that increases over time. During this Time is shown by the contact 32, 33 Voltage U has a potential that is down to one any existing saturation voltage the switch 27, 28 is at ground potential. This registered in Figure 2 with the reference numeral 50 The time period is the closing phase. In connection the switch 27, 28 opens at the closing phase 50, so that a swinging of the through the primary winding 12, 13 flowing current on an in Figure 1, not shown capacitor takes place. A rapid change in current has a high induced Tension resulting on the secondary side the ignition coil 12, 13 as the ignition voltage occurs. Occurs on the primary side of the ignition coil also an ignition pulse whose amplitude reaches a value that is mainly due to the Gear ratio of the ignition coil between Primary and secondary winding is given. The four successive shown in Figure 2 Ignition pulses have the reference symbols 51, 52, 53, 54. Following the ignition pulse 51, 52, 53, 54 follows the burning phase 55, during which the spark plug 23, 24, 25, 26 a gas discharge is present. One follows the burning phase 55 Opening phase 56 during which the switch 27, 28 is open. With the beginning of the Closing phase 50 is a new ignition process initiated.

In Figure 2 are a first and a second Threshold 57, 58 entered, the first Threshold 57 of the first, third and fourth firing pulses 51, 53, 54 and the second threshold 58 of all ignition pulses 51, 52, 53, 54 exceeded becomes. Furthermore, the time intervals between the individual ignition pulses 51, 52, 53, 54 registered. An interval begins where the amplitude of the ignition pulses 51, 52, 53, 54 either the first threshold 57 or the second Threshold 58 reaches and ends at the corresponding one Place of the following impulse. As Intersection points of the ignition pulses 51, 52, 53, 54 with the thresholds 57, 58 are each increasing Edge 59 of the ignition pulses 51, 52, 53, 54 is provided. A first time interval 60 is between the first and third firing pulses 53, based on the first threshold 57. A second time interval 61 lies between the third and fourth firing pulse 53, 54, also related to the first threshold 57. Third, fourth and fifth time intervals 62, 63, 64 are each between two successive firing pulses 51, 52; 52, 53; 53, 54, each based on the second threshold 58.

In Figure 3 is another block diagram of the Measuring device 11 shown. Matching parts in Figures 1 and 3 have the same reference numerals. The measurement lines 34, 35 become a signal combining arrangement 70 forwarded which output an output to a comparator 71 outputs the output signal 72 of a signal processing Arrangement 73 is supplied.

The methods according to the invention are based on the block diagrams shown in Figures 1 and 3 in conjunction with that shown in Figure 2 Signal curve explained in more detail: The ignition pulses occurring in the ignition system 10 51, 52, 53, 54 are on the contacts 32, 33 tapped. Instead of the one in FIG shown galvanic connection of the measuring lines 34, 35 with the first primary connections 14, 15 of the ignition coils 12, 13 is also a capacitive or an inductive coupling possible. The Firing pulses 51, 52, 53, 54 can also on others Place the ignition system 10, for example tapped the secondary side of the ignition coils 12, 13 become. Instead of that shown in Figure 2 primary ignition signal curve then results for example a secondary ignition signal curve, being the characteristic firing pulses 51, 52, 53, 54 are however present.

The measuring lines leading to the measuring device 11 34, 35 are usually first in a signal conditioning circuit, that in Figure 1 is not is entered for further signal processing prepared. For example, such a signal conditioning circuit a voltage divider, an impedance converter or an amplifier circuit contain. The signals are then of the evaluation arrangement 36, the a qualitative or quantitative analysis of the signals makes. Some of these evaluations hang from time to time. Such evaluations are for example the determination of ignition times of the individual cylinders in chronological order during an engine cycle. Depending on the evaluation of time is instead of that shown in Figure 2 analog signal uses a digital signal that by a defined level or a defined Edge devices for determining Times start or stop. The output signal 42 the signal processing arrangement 41 is a such a signal with which the evaluation arrangement 36 carries out the time-related evaluations. The Signal 42 contains, for example, pulses at each firing pulse 51, 52, 53, 54 to be triggered. So from the one shown in Figure 2 Signal derived reliable pulses is a careful definition of the Threshold 57, 58 required if exceeded by the ignition pulses 51, 52, 53, 54 one pulse each is triggered. According to the invention it is initially provided that the threshold 57, 58 is variable. As equivalent to this measure is considered that the threshold 57, 58 is fixed is specified and that the amplitude of the signal is changed according to the order of the State of the art mentioned at the beginning. The on the measuring lines 34, 35 are lying signals each supplied to the comparators 37, 38. The signal processing arrangement 41 sets the Threshold 57, 58 initially to a high value fixed, depending on the determined time Intervals and, if necessary, depending on the counting results is reduced.

According to the execution of the invention Vedahrens provides that the temporal Distances of at least two successive ones Firing pulses 51, 52; 52, 53; 53, 54 within of a predeterminable ratio. At an initially comparatively high threshold, the for example the first shown in Figure 2 Threshold 57 corresponds to the first one time interval 60 between the first and third firing pulse 51, 53 and then the second time interval 61 between the third and fourth firing pulse 53, 54 determined. The relationship the time intervals 60, 61 are then for example with 2: 1. By a suitable specification of a Ratio within which the time intervals 60. 61 must lie, the signal processor recognizes Arrangement 41 a faulty Operating status. When determining a suitable one Area for the relationship can be knowledge be based on the fact that an internal combustion engine a maximum acceleration between successive firing pulses can. An experimentally determined value is currently around 30%. It follows that the ratio is preferably in a range of about 1: 0.7 to 1: 1.1 can be specified. With this specification, the internal combustion engine is braked already taken into account, one maximum change between successive Ignition pulses of approximately 10% are used has been.

After the signal processing arrangement 41 has determined that the time intervals 60, 61 at least two consecutive firing pulses 51, 53; 53, 54 outside the specified Ratio, the threshold 57, 58 is lowered. Soba! D the threshold reaches a value has, for example, with that entered in Figure 2 second threshold 58 coincides the signal processing arrangement 41 the time intervals 62, 63, 64 between successive Firing pulses 51, 52; 52, 53; 53, 54. Since these distances 62, 63, 64 within the predetermined Ratio, the corresponding Pulses as output signal 42 to the Evaluation arrangement 36 issued.

A further development of this invention The procedure provides that the shortest recorded Distances 62, 63, 64 when determining the Threshold 57, 58 are used as a basis. With this Measure is an incorrect operating state excluded, for example with a signal 2 could occur if periodically occurring pulses with an amplitude occur above the amplitude of the others Impulses. In Figure 2 this would be, for example Case be given when the fourth firing pulse 54 a comparable to the second ignition pulse 52 Would have amplitude. With a determination the variable threshold to a value that the corresponds to the first threshold 57, the signal processing Arrangement 41 by evaluating the Ratio of the time interval 60 between the first and third firing pulses 51, 53 and a further distance, not shown in Figure 2 between the third firing pulse 53 and one determine the non-energized fifth ignition pulse, that the distances within the given Ratio lies, although an incorrect operating state is present. With the advantageous training this case is excluded.

An embodiment of the invention The method provides that the variable threshold in Levels can be specified. Preferably there are two stages, corresponding to the first and second threshold 57, 58 provided, a particularly simple Implementation in terms of circuitry or software is possible.

According to a development of the invention The method provides that a second Threshold 57, 58 is set to a value at the number of firing pulses 51, 52. 53, 54 within an interval defined by the Distance between two successive pulses of the Reference cylinder is given with an expected Number matches. Requirement for this The method according to the further development is the detection of ignition pulses 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 connected to the further contact 46. Instead of the galvanic shown Connection is both capacitive and one inductive coupling possible. The further measuring line 45 leads the tapped signal to the reference signal generator 44 to which an output signal outputs the signal processing arrangement 41. Of the Reference signal generator contains, for example Voltage divider, an impedance converter and / or an amplifier and a comparator. Of the Reference signal generator 44 is also intended to be pulse-shaped Output signal as the comparators 37, 38, by comparing the input signal arises with a threshold. The default one However, threshold is much easier here because the input signal can be clearly identified is. Usually the reference signal from a trigger gun that detects the in the secondary circuit flowing spark plug current or at least whose changes are recorded.

The reference signal generator 44 gives rise to everyone for example the first firing pulse 51 a signal to the signal processing arrangement 41 from. So that the arrangement 41 within a Determine the ignition cycle of the engine cycle the number of cylinders must be communicated to her become. For this purpose, the cylinder counter 43 is provided for example from an input is controlled. The variable second threshold 57, 58 becomes set during operation so that the signal processing arrangement 41, starting from first ignition pulse 51, four ignition pulses counts until again the first ignition pulse occurs, which the Ignition pulse for the reference cylinder corresponds. in the An example is a four-cylinder internal combustion engine be accepted.

Is achieved thereby a further increase in operational security, where the one method Plausibility check of the other procedure represents. So it is possible to start with the first Use method according to claim 1 and then the result to check with the second method according to the characterizing part of claim 2 and vice versa.

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 are, each with different test leads 34, 35 to separate comparators 37, 38 to lead. The threshold for each comparator 37, 38 can be specified individually. Instead of the separate Comparators 37, 38 can be a single one according to FIG Comparator 71 may be provided, the one merged signal is fed. For Signal merging of those on the test leads 34, 35 lying signals is the signal combining arrangement 70 provided an overlay who makes signals, for example be implemented as an analog OR operation can.

The signal processing arrangement 73 gives way from the arrangement 41 shown in FIG the specification of the threshold for the comparator 71 onwards. Instead of specifying a uniform The threshold is preferably the specification of a time-changing threshold is provided, whereby the threshold was expected for either individual Firing pulses or groups of firing pulses can be set. From previous ones Firing pulses can advance the threshold be given at a time after which the next ignition pulse is expected.

The methods according to the invention can both be implemented in analog circuit technology as well as run in a microprocessor system. With a digital implementation in a microprocessor system are the detected signals first undergo an analog / digital conversion and then the comparison operations and Evaluation procedure carried out in the number range.

Claims (8)

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, characterized in that the threshold (57, 58) or the amplitude of the sensed pulses is variable and in that the threshold (57, 58) or the amplitude of the sensed pulses is specified at a value at which the time intervals (62, 63, 64) between at least two successive ignition pulses (52, 51; 53, 52; 54, 53) lie within a prescribed relationship.
2. Method according to Claim 1, characterized in that a second threshold (57, 58) or the amplitude of the sensed pulses is variable, and in that the second threshold (57, 58) or the amplitude of the sensed pulses 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 a reference cylinder, with an expected number.
3. Method according to one of the preceding claims, characterized in that the threshold (57, 58) can be prescribed in increments.
4. Method according to Claim 3, characterized in that two increments (57, 58) are provided.
5. 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).
6. Method according to Claim 5, 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).
7. Method according to Claim 1 and according to one of Claims 2 to 6, characterized in that the relationship is specified in a range of 1 : 0.7 to 1 : 1.1.
8. Method according to Claim 1 and according to one of Claims 2 to 7, characterized in that the shortest sensed intervals (62, 63, 64) between successive ignition pulses (52, 51; 53, 52; 54, 53) are used as the basis during the specification of the threshold (57, 58).

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