FR2703405A1 - Device for detecting a malfunction of an electronic ignition system of an engine, in particular of a motor vehicle. - Google Patents

Abstract

This device for detecting a malfunction of an electronic ignition system of an engine, in particular of a motor vehicle, of the type comprising a control computer for controlling the supply of the primary circuits of ignition coils (1, 2, 3) of which secondary circuits are connected to spark plugs associated with the cylinders of the engine, is characterized in that it comprises means (7, 8, 9) for statistical analysis of the spark durations between the electrodes of the spark plugs, to determine a malfunction.

Description

The present invention relates to a device for detecting a

  operation of an electronic ignition system of an engine, in particular of a motor vehicle. More particularly, the detection device according to the invention applies to an ignition system

  a positive-ignition internal combustion engine of the type

  as a control computer supplying the primary circuits of the ignition coils whose secondary circuits are connected to spark plugs associated with

engine cylinders.

  In such an ignition system, a spark plug is associated with each cylinder, an ignition coil is associated with one or two spark plugs, the ignition coils have a primary circuit and a secondary circuit and are used to accumulate and transfer electrical energy to the spark plugs and the primary circuits of these coils are supplied under control

  the computer which manages the lighting time

  mage and distribution to the engine cylinders.

  It has already been proposed in the state of the art to monitor the operation of these ignition systems by controlling the amplitude and the duration of the voltage pulses present in the primary circuits of the coils and by comparing these parameters with thresholds calibrated for

  determine malfunctions.

  However, these devices have a number of disadvantages in terms of discrimination of

malfunctions.

  The object of the invention is therefore to solve these problems.

  To this end, the subject of the invention is a provision

  detection of a malfunction of an electronic ignition system of an engine, in particular of a motor vehicle, of the type comprising a

  control of the supply of primary coil circuits

  Ignition nes with secondary circuits connected

  spark plugs associated with engine cylinders,

  terized in that it includes statistical analysis means

  that sparking times between the electrodes of the

  spark plugs to determine a malfunction.

  According to one embodiment, the means of analysis

  statistical lysis include means of acquiring

  spark times from the voltages in the circuits

  primary coils, means of calculation, for each cylinder, of statistical value indicators

  mean, instantaneous quadratic deviation and quadratic deviation

  average tick, over N duration values, and means of analysis

  lysis of these indicators to determine a defect in

operation.

  The invention will be better understood using the

  description which follows, given only as

  example and made with reference to the accompanying drawings in which: Figure 1 shows a block diagram illustrating the structure of a detection device according to the invention; FIG. 2 represents a detailed electrical diagram illustrating the data acquisition part of a detection device according to the invention; Figure 3 illustrates the shapes of the signals present at different points on the circuit shown in Figure 2; Figure 4 illustrates the functioning of means of calculating statistical indicators entering into

  the constitution of a detection device according to the

  vention, and Figure 5 illustrates the functioning of means of analysis of statistical indicators entering into

  the constitution of a detection device according to the invention.

  The purpose of the detection device according to the invention

  tion is to detect and identify malfunctions of the high voltage stages of the systems

  of electronic ignition of motor vehicle engines

  bile and thus diagnose a failure of a spark plug, an ignition coil or the connection between

this candle and this coil.

  The detected faults can then be classified into two categories, namely: serious faults, such as to cause a total absence of spark between the spark plug electrodes, and

  critical faults likely to cause

  that a bad initialization of the combustion.

  It is therefore understandable that the advantage of this device lies in particular in the fact that it allows a convenience store to quickly know the state of the ignition system of an engine without having to dismantle the various elements mentioned above, which is interesting in particular when the ignition coils are arranged above the spark plugs Furthermore, the detection of the total absence of spark for a given cylinder makes it possible to act on the fuel injection in order to preserve in particular

  means for catalytic purification of exhaust gases

  integrated into the vehicle exhaust line.

  Finally, it is also desirable that such a device does not require any additional component to

  level of the high voltage stages, which presents general-

  implantation difficulties, electrical isolation

that and reliability.

  The block diagram of such a device

  fault detection is given in figure 1.

  We recognize in this figure the classic structure of an electronic ignition system of an engine

especially a motor vehicle.

  This includes a control computer (not shown) for controlling the supply of

  primary ignition coil circuits, three of which

  indicated by the references 1, 2 and 3, are represented in FIG. 1 and correspond for example to the coils

  for igniting the spark plugs of a six-cylinder engine.

  Control of the power supply to the primary circuits

  mayors of these coils is done in a conventional manner, for example by means of transistors 4, 5 and 6 whose collectors are connected to the primary circuits of

  coils and whose bases are connected to the computer.

  The secondary circuits of these coils are

  connected to candles associated with the corresponding cylinders

  of the engine and it is understood that the computer

  request the chain supply of these candles to obtain

  chain ignition of the engine cylinders.

  The detection device according to the invention comprises means for statistical analysis of the durations

  sparks between the spark plug electrodes to detect

  undermine a malfunction of the ignition system.

  These means of statistical analysis include, as can be seen in this figure 1, means 7

  acquisition of spark times from voltages

  sions in the primary circuits of the coils, the output of which is connected to means of calculation and statistical processing 8 allowing, as will be described in more detail below, to calculate, for each cylinder, statistical indicators on N values of spark times The output of these processing means is linked to analysis and discrimination means 9 making it possible to recognize from these indicators serious faults and critical operating faults

  which will also be described in more detail below.

  Thus, the means for acquiring the spark times ensure, from the voltages in the primary circuits of the ignition coils, the multiplexing of the overvoltages generated by the sparks and the filtering and then the reshaping of this multiplexed signal in order to provide the rest of the device with a binary signal

  unique with slots whose duration is represented

  successive spark times.

  This data acquisition stage is characterized

  laughed at by the fact that its operation is not disturbed by the switching of the different coils and that consequently it allows overlap between the controls of these coils, this case being able to be encountered at high speed

  operating on engines with more than five cyl-

dres.

  The statistical processing part of these spark durations is provided by a programmed microcontroller which acquires the spark duration signal via a measurement stage of

  time The spark duration values are multiple

  plexed by cylinder and stored in storage means, as will be described in more detail below. The processing carried out on the content of these storage means makes it possible to provide, for each cylinder, the following statistical indicators instantaneous quadratic deviation, mean quadratic deviation (variance), and

average value.

  The discrimination part can also be

  provided by the microcontroller to compare the indicators

  statistical factors between them and / or at calibrated thresholds in order to extract the signaling of a serious or critical fault These faults can be materialized by a code written in the memory of the microcontroller and whose value provides information on the type of fault detected and on the

cylinder concerned.

  The memorization of a fault can be filtered, i.e. it is only effective after a certain number of successive detections, this number possibly

also be chosen.

  The structure of this device and how it works

  ment are illustrated in more detail in Figures 2 and 3.

  It can indeed be seen in these figures that the acquisition means 7 comprise means for multiplexing the overvoltages generated at the primaries of the coils by the sparks, these multiplexing means

  being designated by the reference 10 in FIG. 2.

  The output of these multiplexing means is connected to filtering means 11 and to means 12 for reshaping the output signal of these multiplexing means for delivering the binary signal mentioned above. These filtering and fitness means have a classic structure based on amplifiers

operational.

  In this FIG. 2, the acquisition means are adapted to acquire data in a system

  jumostatic ignition for a six-cylinder engine.

  The multiplexing means include an amplifier

  operational ficitor 13 connected as a summator to perform

  kill the summation of the voltages in the primary circuits of the coils, designated by the references V 1, V 2 and V 3 and

  subtract from them the multi-supply voltage

  folded by the number of non-active C 1, C 2 and C 3 commands.

  In fact, this operational amplifier 13 receives on an input, the control voltages of the primary circuits of the coils and on another input, the voltages actually present in these primary circuits in order to derive the overvoltages generated by them.

  sparks between the spark plug electrodes.

  It can therefore be seen that the voltage designated by the reference V 4 at the output of this adder can be written to a factor near as follows

  V 4 = Vl + V 2 + V 3 VBAT (+ C 2 + C 3).

  This voltage signal V 4 therefore restores only the overvoltages present in the primary circuits of the coils, which are the image of the secondary voltages at

candle terminals.

  This voltage signal V 4 is then filtered in order to reduce the amplitude of the oscillations mainly due to turbulence in the combustion chamber of

each cylinder.

  The output voltage V 5 of these filtering means 11 is then reshaped by a comparator stage and the voltage signal V 6 thereof is in the form of a binary signal whose width of the status slots logic O for example is representative of the

duration of sparks.

  This binary signal is then introduced into the microcontroller constituting the means of calculation 8 of the statistical indicators and of analysis 9 of these, this microcontroller being generally designated by the

reference 14 in Fig 2.

  The operation of this microcontroller for the calculation of statistical indicators is illustrated on the

figure 4.

  It can be seen with regard to this figure that the successive values of the spark durations are sorted by cylinder and stored in primary type stacks

  in-out FIFO assigned to each cylinder.

  In the case of functional control systems

  operation of motors having no phase information

  engine, the successive values of the same pair of cylin-

  dres must be alternately stored in two separate batteries assigned to one or the other

of the two cylinders.

  Then, this microcontroller performs in time

  the following different operations on the N

  last values of sparking times of the active cylinder calculation of the mean _ 1 i = N-1 t = E t N i = O calculation of the instantaneous quadratic deviation An 2 = (tr t) 2

  calculation of the mean square deviation (varian-

ce): 1 i = P-l P i = O

  It should be noted that for high operating regimes

  engine operation it is possible to limit the milking

  ment to the calculation of An using the mean value t calculated at low speed and, in this case, only the faults

  serious operation will be monitored.

  The values of N and P are determined experimentally.

  rimentally and it has been established that the order of magnitude of N is less than 10 to obtain the mean value t accurate to within 10% in the case of very unstable sparking times P can meanwhile be less than or equal to N and the calculations made by the microcontroller are

  reduced if we choose for P and N a power of 2.

  The fault discrimination part is based on a comparison of these different indicators with each other and / or on calibrated thresholds to determine serious or critical faults of

operation.

  Serious operating faults are likely to cause an alarm which leads to an inhibition of the injection of fuel into the cylinder or cylinders for which the ignition is defective. To detect these faults, the statistical indicator of quadratic deviation is used. snapshot A 2 which is time information

  real and corresponds to the active cylinder at the same time.

  This instantaneous quadratic deviation is compared to a calibrated threshold and if it is higher than this threshold, a

  fault counter assigned to the active cylinder is incremented

lied.

  Otherwise, the counter is decremented.

you.

  The starting value of this counter is fixed at zero. An alarm is generated when the counter reaches a calibrated filtering value F Thus, we

  understands that it is necessary to detect F faults

  to trigger this alarm and the recording of the

corresponding fault code.

  Ignition faults likely to cause

  such a serious defect can for example be a short

  ignition coil secondary circuit, open spark-free secondary circuit, or spark plug

  heavily fouled, drowned or pearled.

  Figure 5 illustrates this operation of the

  microcontroller for the detection of this fault.

  In the event that an anomaly is detected from the statistical indicators without generating the alarm described above, the fault is classified as critical fault This situation corresponds to the different cases in which the ignition is present

but of poor quality.

  Thus, the early warning signals of ignition failures cause the recording of fault codes

to guide the convenience store.

  For this discrimination, the indicators of mean value t and mean square deviation (variance)

C 2 are used.

  Three comparisons are made.

  First, the variance is compared to a calibrated threshold which depends on the engine operating mode, the dispersion of the spark times depending on

  Indeed, the dispersion is strong in acceleration

  ration and under heavy load and it is more moderate when idling, engine warm, and when decelerating

cut off the injection.

  If the variance is less than the threshold, a critical fault is recorded and corresponds to the case where all or part of the spark occurs outside the combustion chamber and therefore is not

  subject to explosion disturbances.

  This occurs in the event of a bad snap-on of the spark plug cap causing an arc on the olive thereof, poor insulation causing an arc between the supply beam and metallic mass and an insulation fault between circuits primary and circuit

secondary ignition coil.

  Serious faults also induce a fault

  variance too small but with a greater delay

so much.

  The mean value t is also compared with a calibrated threshold. This comparison is only carried out in the operating modes in which the spark is

  stable and not very dependent on the environment, decelerating

  tion for example If this average value is below the threshold, a critical fault corresponding to wear of the spark plug electrodes is recorded This detection

  also intervenes in the event of an open secondary circuit.

  The average value t is also compared with the average value of the spark times of the cylinder which is in the exhaust phase, that is to say the twin cylinder,

mechanically in phase.

  This particularly interesting test in the

  case of twin ignitions, allows to detect a dissymé-

  sorts too high between the sparks fed by

the same coil.

  If the deviation is greater than a calibrated threshold depending on the engine operating conditions, a critical fault is memorized and corresponds to significant wear of the spark plugs, to a plug that is too tight that would have been damaged during assembly or to fouling.

important of these candles.

  Critical faults thus recorded accompany

  with a reference to the corresponding cylinder (s) then allow the repairman to dismantle the ignition components in an appropriate manner and above all to avoid tests which consist in opening the high-voltage circuit to check for the presence of sparks, at the risk to destroy the integrated catalytic purification devices

  in the vehicle exhaust line.

Claims (9)

  1. Device for detecting a malfunction   operation of an electronic ignition system   engine, in particular of a motor vehicle, of the type comprising   as a control computer supplying the primary circuits of the ignition coils (1, 2, 3) of which   secondary circuits are connected to associated spark plugs   ciées to the engine cylinders, characterized in that it includes means (7,8,9) for statistical analysis of the spark times between the spark plug electrodes for   determine a malfunction.   2. Detection device according to the claim   tion 1, characterized in that the statistical analysis means   tick include means (7) for acquiring durations   sparks from voltages in the primary circuits   mayors of the coils (1, 2, 3), means (8) of calculating, for each cylinder, statistical indicators of value   mean, instantaneous quadratic deviation and quadratic deviation   average tick, over N duration and average values (9)   analysis of these indicators to determine a fault.   3. Detection device according to the claim   tion 2, characterized in that the acquisition means   include means (10,13) for multiplexing the sur-   sions generated in the primary circuits of the coils by the sparks, and means (11, 12) for filtering and reshaping the output signal of these multiplexing means, for delivering to the rest of the device a binary signal comprising slots of which the duration is   representative of the sparking times.   4 Detection device according to the claim   tion 3, characterized in that the multiplexing means comprise an operational amplifier (13) receiving on one input the control voltages of the primary circuits of the coils (1,2,3) and on another input the voltages actually present in these circuits primary   to determine the overvoltages generated by the those.   5. Detection device according to any one   as claims 2 to 4, characterized in that the   means (8, 9) for calculating and analyzing the static indicators include memory means assigned to each cylinder of the engine and in which the values of the corresponding spark durations are stored, at   from which these indicators are calculated and analyzed teurs.   6. Device according to any one of   claims 2 to 5, characterized in that the means   analysis indicators are adapted to compare the statistical indicators relating to the different cylinders of the engine with each other and / or to calibrated thresholds depending on the operating conditions of the engine, for   recognize a malfunction.   7. Detection device according to the claim   tion 6, characterized in that the analysis means (9) are adapted to compare the instantaneous quadratic deviation associated with a cylinder with a calibrated threshold to increment or decrement a counter whose value is compared with a filtering value (F ) to indicate a serious fault   of the ignition system, in the event of sement.   8. Detection device according to the claim   tion 6 or 7, characterized in that the analysis means (9) are adapted to compare the mean square deviation and the mean value with calibrated thresholds to determine   a critical malfunction of the ignition system age, if exceeded.   9. Device according to claim 6,7 or 8, characterized in that the analysis means (9) are adapted to compare the average value associated with a cylinder with the average value associated with the twin cylinder in the exhaust phase to determine a deviation, this deviation being compared to a calibrated threshold to determine a critical malfunction of the ignition system, in the event of overshoot. 5 10 Device according to any one of the   Claims 2 to 9, characterized in that the means for   calculation and analysis include a microcontroller (14).