EP0707144B1 - Device for the detection of ignition signals - Google Patents

Description

State of the art

The invention is based on a device for detecting of ignition signals according to the type of the main claim.

A generic device is for example from the DE-A 24 60 046 known. One designed as trigger pliers inductive current clamps detects one through a spark plug an internal current flowing. The previously known Trigger pliers have a low inductance that is sufficiently dimensioned to be reliable on the one hand To provide trigger pulses and on the other hand a high Ensure suppression of interference signals. One with the Trigger clamp connected signal evaluation circuit contains a capacitor on the input side, which is the quality of a Resonant circuit containing trigger pliers improved in such a way that the first positive and the first negative half wave of the Trigger signal have almost the same amplitudes. The Known trigger pliers react to steep changes in current of the current flowing through the spark plug. The Sensitivity cannot be easily increased because with an increase in the capacitive coupling of disturbances is to be expected. Signals after the electrical Breakdown of the spark plug may occur, for example those that may occur during spark ignition duration difficult to grasp the known trigger pliers.

From DE-A 34 00 787 is also a trigger pliers trained inductive current clamp known, the opposite the aforementioned prior art the difference exhibits that on the one hand the sensitivity is increased and that on the other hand due to a low natural resonance frequency of a resonant circuit containing the trigger pliers slow Operations such as spark ignition duration are detectable. The known trigger pliers contain one Winding with a high number of turns leading to a leads to a correspondingly high inductance. On the one hand the to achieve predetermined high inductance and around on the other hand the highest possible suppression of To ensure interference signals, the winding is on two Legs of the trigger gun applied symmetrically.

DE-A 39 02 254 discloses two methods of assignment of ignition signals to a reference cylinder Multi-spark ignition systems of spark ignition internal combustion engines. A first method is based on a comparison of Signal levels of successively detected ignition pulses. Of the main sparks that occurred for the actual ignition process has a higher level than an unnecessary one Support spark on. A second procedure evaluates you temporal offset between the main spark and the Support spark from the higher ignition voltage requirement of the main spark versus that of the supporting spark. For Detection of the ignition signals is equally one Trigger pliers and a capacitive encoder for detecting the Ignition voltages can be used. Only those are to be evaluated Currents or the voltages that occur during electrical Breakdown occurs on a spark plug.

The invention has for its object a device to detect ignition signals that specify a Reliable ignition diagnosis with a trigger gun enables.

The task is defined by the main claim Features resolved.

Advantages of the invention

The device according to the invention has the advantage that with the inductive one designed as trigger pliers Current clamp signal issued a diagnosis of events is possible, both during the spark start and also occur during the spark duration.

According to the invention it is provided that the inductance of the Trigger pliers are added to a resonant circuit, being a first resonant circuit is provided, the resonance frequency is matched to rapid ignition current changes during of the start of the spark, and that a second The resonant circuit is provided, the resonance of which is slow Ignition current changes is turned off during the Ignition spark duration is available.

The device according to the invention is suitable for diagnosing multi-spark ignition systems, in particular two-spark ignition systems, which contain a number of ignition coils corresponding to half the number of cylinders. It is equally possible to diagnose single-spark ignition systems which also make ignitions in the exhaust cycle to save a camshaft sensor.
A major advantage is the cost-effective implementation, since only a few electrical components are required.

Further advantageous developments and refinements of Device according to the invention result from dependent Claims.

The measure from the first is particularly advantageous Vibration circuit provided signal with the higher frequency to provide an amplitude evaluation that the signal with compares at least one threshold, for example, to Distinction between a main spark and one Support sparks. The distinction makes it possible to recognize the Work cycle of the internal combustion engine.

Another advantageous measure provides that the second resonant circuit provided signal with the lower frequency is fed to a time evaluation, which determines the speed of the internal combustion engine.

The consideration of the of the amplitude evaluation and the Time evaluation given signals enables a reliable determination of the speed of the internal combustion engine and at the same time reliable detection of the Work cycle. Operating states of the internal combustion engine, at for which the amplitude of the support spark is briefly higher than the amplitude of the main spark, for example at an interruption of the fuel supply while the engine is running Internal combustion engine occur, do not cause the Speed is determined incorrectly. Furthermore, the Speed signals as internal trigger signals for the Maintaining the assignment of the ignition signals to Work cycle are used, so that the assignment of Main sparks and supporting sparks during the short-term Amplitude reversal is not lost.

An advantageous embodiment provides that the two Oscillating circuits are combined to form a bandpass filter. A separation of the signal component with the lower frequency of the signal component with the higher frequency is by means of a simple low-pass filter possible.

Another advantageous embodiment provides that an im second resonant circuit containing inductive element as Transformer is formed. The transmitter provides one Electrical isolation safely and made possible by the definition the transmission ratio is free within wide limits Choice of the decouplable signal amplitude. An arrangement the secondary winding of the transformer with a Center connection is particularly suitable for a subsequent signal rectification.

A further embodiment provides that the second Resonant circuit has a loss resistance that for one defined decay process of an excited oscillation worries. The loss resistance is preferably called ohmic Realized resistance that as a series resistance or as Parallel resistor is used.

An amplifier circuit that the signal with the lower Frequency boosted, allows easy level adjustment to a subsequent evaluation circuit, for example the time evaluation.

The amplifier circuit is preferably a Amplitude control, which complements the output amplitude of the Amplifier circuit regulates to a predetermined value. With this measure is an independent adjustment to Ignition currents possible depending on the particular Ignition system can be significantly different.

In individual radio systems, the ignition coils in each Cylinder head are installed directly on the spark plugs the secondary side of the ignition coils is no longer accessible. It is common for these single spark ignition systems Trigger pliers to the primary line of the first cylinder to clamp assigned ignition coil. The trigger pliers detects the primary current change when opening the Power stage of an ignition switchgear. With this use the Trigger gun is the trigger signal amplitude by one Much higher than with secondary adaptation. Through the Regulation to at least approximately constant amplitude there is an automatic signal adjustment and thus a big gain in the ratio of signal amplitude to Interference amplitude. One upstream of the amplifier Low pass filter also suppresses the primary current superimposed higher-frequency signal components, which by the Arcing can occur on the spark plug.

Further advantageous developments and refinements of Device according to the invention result from further dependent claims and from the following description.

drawing

Figure 1 shows a circuit diagram of an inventive Device, Figures 2 and 3 show waveforms in Dependence on the time shown in that in Figure 1 Circuit occur, Figure 4 shows an alternative Circuit to the circuit shown in Figure 1, Figure 5 shows an alternative circuit to that shown in Figure 1 Circuit using an inductive element as a transformer is configured, and FIGS. 6 and 7 each show alternative configurations of those shown in FIG. 4 Circuit, which also each have an inductive Element is designed as a transformer.

FIG. 1 shows a trigger tongs 10 inductive current clamp, which is placed around an ignition cable 11, that from a high voltage connection 12 to a spark plug 13 leads.

The trigger gun 10 contains two mutually movable magnetizable legs 14, 15, of which at least one Leg 15 carries a winding 16, which is a known Inductance 17, which as a replacement parameter in Figure 1 is entered.

The trigger gun 10 provides an output signal between one Trigger clamp connector 18 and a device mass 19 ready. At the Trigger clamp connector 18 is a first capacitor 20 connected, which is connected to ground 19. At first A first output signal 21 can be tapped off capacitor 20, which is fed to an amplitude evaluation 22, the one outputs the first switching signal 23.

There is also a coil on the first capacitor 20 connected, of which the inductance 24 as Substitute parameter is entered. The coil with the Inductance 24 is connected via a second capacitor 25 Mass 19 connected. Between the inductor coil 24 and the second capacitor 25 is an amplifier 26 connected with a second output signal 27 provides that is supplied to a time evaluation 28, the provides a second switching signal 29.

Figure 2 shows the first output signal 21 in dependence from time t. Two high-frequency are shown Vibration packets 30, 31. The amplitude of the first Vibration package 30 is denoted by the reference numeral 32 and Amplitude of the second vibration packet 31 with the Reference number 33 is entered, the amplitude 32 being higher lies as the amplitude 33.

Figure 3 shows the second output signal 27 in dependence from time t. A first low frequency is entered Vibration package 34 and a second low frequency Vibration package 35. The two low-frequency Vibration packets 34, 35 point at least approximately the same amplitude 36. Between the vibration packets 34, 35 is a time T.

Figure 4 shows an alternative to that shown in Figure 1 Circuit. Those parts of Figure 4 that with the in Figure 1 parts match, wear each the same reference numerals. The amplifier shown in Figure 1 26 is in Figure 4 via a low-pass arrangement 37 with the Trigger gun connector 18 connected to the first Capacitor 20 and the coil with inductance 24 are connected.

Figure 5 shows an alternative to that shown in Figure 1 Circuit. Those parts of Figure 4 that with the in Figure 1 parts match, wear each the same reference numerals. The coil with inductance 24 of Figure 1 is replaced by a transformer 40, the one Has primary winding 41 and a secondary winding 42. The secondary winding 42 has a center tap 43. In Series with the transformer 40 is a damping resistor 44 switched. The amplifier 26 shown in FIG. 1 is shown in FIG 5 additionally with an amplitude control 45 equipped which the amplitude of the second Output signal 27 at least approximately to one regulates the specified value.

Figure 6 is apparent from Figure 4 in that the coil with the inductor 24 is replaced by the transformer 40.

Figure 7 shows an alternative embodiment of the device according to the invention according to FIG Low pass arrangement 37 with the downstream amplifier 26 is compared to Figure 6 on the secondary winding 42 of the Transmitter 40 connected.

The inventive device for detecting Ignition signals according to Figure 1 works as follows:

The spark plug 13 is used to ignite a fuel-air mixture provided in the cylinder of an internal combustion engine. The trigger gun 10 detects one in the ignition line 11 flowing electrical current during the Spark start and then during Spark duration in the spark plug 13 between the High-voltage connection 12 and the mass 19 flows. The Trigger pliers 10 contain two mutually movable Legs 14, 15, an adaptation on the ignition cable 11th enable that by the of the two legs 14, 15th formed opening must be performed. The one in the ignition cable 11 flowing electric current has the ignition cable 11 circular magnetic field resulting from the Trigger pliers 10 is detected. That in the legs 14, 15 existing magnetic field induced in the winding 16, which in The embodiment shown is arranged on the leg 15 is an electrical voltage between the Trigger clamp connector 18 and the mass 19 can be tapped. The winding 16 has the inductance 17, which in the essentially by the number of turns of the winding 16 and the magnetic properties of the legs 14, 15 is set.

The circuit connectable to the trigger clamp connector 18 first contains the first capacitor 20, which Inductance 17 of the trigger gun 10 to a first Vibration circuit added. At the first resonant circuit 17, 20 that is first output signal 21 can be tapped, which the Amplitude weighting 22 is supplied, which is the first Outputs switching signal 23. The resonance frequency of the first The resonant circuit 17, 20 is to be tuned such that fast Ignition current changes excite the resonant circuit 17, 20. Rapid ignition current changes occur during the Spark start. The resonance frequency of the first The resonant circuit 17, 20 is, for example, at 300 kilohertz matched, the inductance 17 of the trigger gun 10 to 120 microhenry and the capacitance of the first capacitor 20 at 2.2 nanofarads were assumed. With a sufficiently high one Voltage corresponding to the ignition voltage of the spark plug 13, finds an electrical breakdown on the spark plug 13 instead, the current flow during the first nanoseconds by discharging the electrical capacity of the spark plug 13 and then by discharging the ignition cable and Ignition coil capacity is maintained.

The fast, of capacitive displacement currents maintained current peak stimulates the first resonant circuit 17, 20 to corresponding vibrations, which are shown in FIG are shown in more detail. The peak value of the current is dependent from the ignition voltage. The first shown in Figure 2 Vibration package 30 with the higher amplitude 32 lies therefore based on a higher ignition voltage than the second Vibration packet 31 with the lower amplitude 33. Different ignition voltages arise in particular Multi-spark ignition systems, in particular in that once in the working stroke and the other time in the exhaust stroke of the Internal combustion engine is ignited. The resulting Sparks are used as main sparks and as supporting sparks designated. The higher compression in the cylinder as well existing fuel-air mixture in the work cycle of Internal combustion engine lead to a higher ignition voltage than in the exhaust stroke. The first vibration package 30 is accordingly a main spark and the second vibration packet 31 a Assign support sparks. The rating is from the Amplitude assessment 22 made the first Output signal 21 is supplied.

The amplitude evaluation 22 preferably contains at least an amplitude threshold value, for example in the Middle between the amplitudes 32, 33 shown in FIG. 2 lies. The first switching signal 23 is such, for example determined that when it occurs it is indicated that the first oscillation packet 30 with the higher amplitude 32 occured. A subsequent further diagnostic circuit receives the information with the first switching signal 23, that a major spark has occurred.

The coil connected to the trigger clamp connector 18 with the Inductance 24 forms with the second capacitor 25 and in particular with the inductance 17 of the trigger tongs 10 a second resonant circuit. It is believed that the second resonant circuit 17, 24, 25 is decoupled from the first Oscillating circuit 17, 20. This decoupling is in practice not completely given, since the series connection from the Coil with the inductance 24 and the second capacitor 25 is connected in parallel to the first resonant circuit 17, 20. It is essential to determine the resonance frequency of the second resonant circuit 17, 24, 25, which is significantly lower lies as the resonance frequency of the first resonant circuit 17, 20. In a realized embodiment, the Resonance frequency of the second resonant circuit 17, 24, 25 7 kilohertz, with 24 for the inductance Value of 100 microhenry and as the capacity of the second Capacitor 25 is based on a value of 2.2 microfarads were. The inductance 17 of the trigger gun 10 is unchanged 120 microhenries. The resonance frequency of the second Resonant circuit 17, 24, 25 is designed such that short Current peaks cause no excitation if possible. The second Oscillating circuit 17, 24, 25 should, if possible, only by slow Signals with a larger pulse width are excited for example, during the spark duration at Spark plug 13 occur. The during this phase of Ignition process current flowing through the spark plug 13 at least approximately independent of the ignition voltage. To reinforce the second resonant circuit 17, 24, 25 tapped signal, which may be required amplifier 26 may be provided at its output the second output signal 27 occurs, which is shown in more detail in FIG is shown. The vibration packets 34, 35 have at least approximately the same amplitude 36. A Distinction between a main spark and one Support spark can therefore be generated with the second output signal 27 become difficult. The second output signal 27 enables reliably providing for example one Speed signal that determines the time evaluation 28 and as outputs second switching signal 29.

The time evaluation 28 preferably determines the between the vibration packets 34, 35 lying time T, which is a measure for the period and thus the speed of the Internal combustion engine is. The second switching signal 29 is for example a square wave whose frequency is a measure for the speed of the internal combustion engine. Based known data of both the internal combustion engine, for example the number of cylinders and the ignition system, which are each fed to the time evaluation 28, the actual speed output as second switching signal 29 become.

By providing the first separately and the second output signal 21, 27 with the help of different resonance frequencies matched Resonant circuits 17, 20; 17, 24, 25 will be reliable Diagnosis of the internal combustion engine or the ignition system possible. In an operating state of the internal combustion engine, the especially when the fuel supply is blocked higher rotating engine can occur is not exclude that the amplitude ratios in change first output signal 21. So it can the case occur that the amplitude 33 of the second Vibration packet 31, which corresponds to a support spark can be higher than the normally higher amplitude 32 of the first vibration packet 30, which is the main spark corresponds. In this operating case, the The presence of the second output signal 27 continues to be one proper diagnosis possible. The assignment of the Vibration packets 30, 31 for main spark and supporting spark can be maintained.

Furthermore, the case may arise that the support spark is on the spark plug 13 only very small amplitudes 33 of the second Vibration packet 31 results, although it cannot be ruled out that coupled interference pulses of comparable amplitudes available. In this case too, this enables simultaneous Presence of the second output signal 27 that Maintain a proper continuous Diagnosis.

An alternative to the circuit shown in Figure 1 is indicated in Figure 4. Instead of decoupling the signal at the Connection between the coil with the inductance 24 and the amplifier 26 is the second capacitor 25 in FIG with the interposition of the low-pass arrangement 37 immediately connected to the trigger clamp connector 18. The in Figure 4 occurring signal level ratios can be cheaper than that in Figure 1. Figure 4 can be used as a bandpass arrangement considered with two different resonance frequencies be, the common signal at the trigger gun connector 18 occurs. To separate the lower frequency ones The low-pass arrangement 37 is provided for signal components Cutoff frequency preferably to the resonance frequency of the second resonant circuit 17, 24, 25 is matched.

Another alternative to that shown in Figure 1 Circuit is shown in Figure 5. Instead of the one in FIG coil with inductance 24 shown is the transformer 40 provided. The first output signal 21 of FIG. 1 occurs as the first output signal 21a, 21b on the secondary winding 42 of the transformer 40. The main advantage of The transformer 40 is in the electrical isolation. Another The advantage arises from the possibility of a Signal amplitude adjustment by setting the Transmission ratio of the transmitter 40 Secondary winding 42 of the transformer preferably has the Center tap 43, compared to a simple Secondary winding a simplified signal rectification of the first output signal 21a, 21b. The second The resonant circuit contains the transformer as an inductive element 40, the inductance by the primary Main inductance is given. The main inductor lies in an implemented exemplary embodiment at 1600 Microhenry. The second resonant circuit 17, 40, 25 contains preferably the damping resistor 44, which is a defined one Decay of the on the second resonant circuit 17, 40, 25 tapped signal enables.

The amplitude control 45 entered in FIG. 5 enables regulating the amplitude of the second output signal 27 to a predetermined value. The control time constant is to be determined such that the damping resistor 44 caused attenuation of the second signal 27 can occur and is not yet settled. Benefits from the Amplitude control results in particular when the Trigger pliers 10 not on the ignition line 11, but on a primary line not shown in the figures Ignition coil is connected. The one on the primary side of the Ignition coil occurring current changes, which the Trigger clamp 10 would be detected without the amplitude control 45 result in a significantly higher second output signal 27, as a corresponding secondary signal.

The circuit shown in Figure 6 goes directly from the shown in Figure 4, the coil with the inductance 24 replaced by the transformer 40 is. The first output signal 21a, 21b occurs again at the Secondary winding 42 of the transformer 40. At this point it is pointed out that the first output signal 21a, 21b on one component, the transmitter 40, the second Resonant circuit 17, 40, 25 and not on the first resonant circuit 17, 20 is tapped. This is possible because of the second capacitor 25 of the second resonant circuit for the significantly higher frequency signal of the first resonant circuit 17, 20 largely represents a short circuit, so that the corresponding higher frequency signal component unimpeded can flow through the primary winding 41 of the transformer 40. In a realized embodiment with the Transformer 40, the second capacitor 25 had a capacitance from 330 nanofarads.

FIG. 7 shows an alternative embodiment to that in FIG 6 circuit shown, in which both the first Output signal 21a, 21b as well as the second output signal 27 derived from the secondary winding 42 of the transformer 40 are. The lower-frequency signal components are again from the low-pass arrangement 37 separated and in the amplifier 26 for second output signal 27 raised. If applicable, the Amplitude control 45 is provided. The main advantage the circuit shown in Figure 7 is complete Isolation by the transformer 40.

Claims (9)

1. Appliance for recording ignition signals, having an inductive clip-on ammeter configured as a trigger-type clip-on instrument (10) for recording a current flowing in a spark plug (13) of an internal combustion engine, the inductivity (17) of said ammeter being complemented to form a resonant circuit, characterized in that a first resonant circuit (17, 20) is provided whose resonant frequency is matched to rapid changes in ignition current which occur during the beginning of the ignition spark, and in that a second resonant circuit (17, 24, 25, 40) is provided whose resonant frequency is matched to slow ignition current changes which occur during the existence of the ignition spark.
2. Appliance according to Claim 1, characterized in that a first output signal (21, 21a, 21b) of the first resonant circuit (17, 20) is supplied to an amplitude evaluation unit (22) which compares the first output signal (21) with at least one threshold value in order to distinguish between a main spark and an auxiliary spark.
3. Appliance according to Claim 1, characterized in that a second output signal (27) from the second resonant circuit (17, 24, 25, 40) is fed to a time evaluation unit (28) which outputs a measure for the engine speed of the internal combustion engine from a time interval (T) between pulse groups (34, 35).
4. Appliance according to Claim 1 or 3, characterized in that the second output signal (27) is separated from the first output signal (21, 21a, 21b) by a low-pass arrangement (37).
5. Appliance according to Claim 1, characterized in that the level of the second output signal (27) is increased by an amplifier (26).
6. Appliance according to Claim 1, characterized in that an inductive element of the second resonant circuit is configured as a repeating coil (40) and the first output signal (21, 21a, 21b) can be taken from its secondary winding (42).
7. Appliance according to Claims 1, 4 and 6, characterized in that both the first output signal (21, 21a, 21b) and the second output signal (27) are made available at the secondary winding (42) of the repeating coil (40).
8. Appliance according to Claim 1, characterized in that the second resonant circuit (17, 24, 25, 40) contains a damping resistance (44).
9. Appliance according to Claims 1, 2 and 3, characterized in that the second output signal (27) maintains the differentiation carried out in the amplitude evaluation unit between a main spark and an auxiliary spark.

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