EP0889235B1 - Device for determining the phase cycle of an internal combustion engine - Google Patents

Description

The present invention relates to a determination device of the operating phase of a combustion engine internal.

More particularly, the invention relates to a such a device which makes it possible to determine the operating phase an internal combustion engine with simultaneous ignition per pair of cylinders, in particular for a motor vehicle.

We already know in the prior art, devices of this type, in which associated candles to the cylinders of each pair are connected at the ends a secondary winding of an ignition coil whose winding primary is connected to a control computer engine operation, through a power stage.

The secondary winding of this ignition coil is for example a mid-point winding and the winding primary of it receives an ignition control signal of the power stage.

These devices are used to optimize control fuel injection and ignition advance in internal combustion and ignition engines ordered.

For this purpose, it is necessary to know not only the angular position of the engine crankshaft, but also the work phase of it and more particularly that of each of the cylinders thereof.

Document FR-A-2 732 723 in the name of the Claimants describes such a device.

The object of the invention is to propose a device of this type which has a simple and reliable structure.

To this end, the invention relates to a device for determining the operating phase of a motor internal combustion with simultaneous ignition by pair of cylinders in particular for a motor vehicle, in which candles associated with the cylinders of each pair are connected at the ends of a secondary winding of a coil ignition whose primary winding receives a signal ignition control of control means controlled by a engine operation control computer, characterized in that it includes means for determining the arithmetic mean value of the two output voltages secondary winding to deliver a binary signal comprising representative slots of the sign of this mean, means for measuring the time elapsing between the instant of control of the coil by the control means and the instant of change of state of the binary signal for at least two successive orders of the coil and means of analysis of these times to determine the phase of engine operation.

• la Fig.1 représente un schéma synoptique d'une partie d'un dispositif de détermination de phase selon l'invention;
• les Figs.2 et 3 illustrent le fonctionnement d'un système d'allumage simultané par paire de cylindres d'un moteur de véhicule automobile;
• la Fig.4 représente un schéma synoptique d'une autre partie d'un dispositif de détermination de phase selon l'invention;
• la Fig.5 représente des chronogrammes illustrant des signaux présents dans cette partie du dispositif;
• la Fig.6 représente un organigramme illustrant le fonctionnement d'un tel dispositif de détermination de phase; et
• les Figs.7 à 11 illustrent différents exemples de détermination de phase grâce à un dispositif selon l'invention.

The invention will be better understood with the aid of the description which follows, given solely by way of example and made with reference to the appended drawings, in which:

• Fig.1 shows a block diagram of part of a phase determination device according to the invention;
• Figs.2 and 3 illustrate the operation of a simultaneous ignition system per pair of cylinders of a motor vehicle engine;
• Fig.4 shows a block diagram of another part of a phase determination device according to the invention;
• Fig.5 shows timing diagrams illustrating signals present in this part of the device;
• Fig.6 shows a flowchart illustrating the operation of such a phase determination device; and
• Figs. 7 to 11 illustrate different examples of phase determination using a device according to the invention.

We recognize in fact in Figure 1, a system simultaneous ignition in pairs of cylinders, in particular for a motor vehicle engine.

Generally speaking, in such an ignition engine simultaneous by pairs of cylinders, candles associated with cylinders of each pair, are connected at the ends a secondary winding of an ignition coil, the primary winding is connected to piloted control means by an engine operation control computer.

In this figure 1, the ignition coil is designated by the general reference 1, while the winding primary of it is designated by the general reference 2.

One of the end terminals of this primary winding 2 is connected for example to the positive terminal + bat of the battery vehicle power supply, while the other terminal end thereof is connected to control means of power designated by the general reference 3 on this figure, including for example a power transistor controlled by a computer 4 controlling the operation of the engine.

The secondary winding of the ignition coil is meanwhile designated by the general reference 5 and each of its ends is connected to a terminal of a candle, designated by general references 6 and 7, corresponding respectively to cylinder n ° 1 and to cylinder n ° 4 of the engine, associated in pair.

The other terminals of these candles 6 and 7 are connected together to ground.

It is therefore understood that the computer 4 for controlling the operation of the engine allows by piloting means of power control 3 to apply a control signal ignition Vc to the spark plugs via the coil ignition 1.

This operation is illustrated in FIGS. 2 and 3, in which the references V _HT 1 and V _HT 4 represent the voltages at the terminals of the spark plugs 6 and 7 respectively of the corresponding pair of cylinders 1 and 4 and V _PM represents the value arithmetic mean of these two tensions.

We can indeed see in the light of these Figures 2 and 3 that during the production of the ignition, one of the two cylinders is in the compression phase, while the other is in the exhaust phase.

The pressures in the combustion chambers of these cylinders are therefore different and the tension required for the generation of an arc between the electrodes of these candles is thus much higher for the cylinder in compression phase than for the exhaust phase.

The voltages V _HT 1 and V _HT 4 are therefore of opposite signs and their arithmetic mean V _PM is of the sign of the highest voltage, in absolute value.

In the examples shown in these figures 2 and 3, we consider that in figure 2, the cylinder n ° 1 is in compression phase and that cylinder n ° 4 is in phase exhaust.

From the instant to when the ignition command is caused by the computer. 4 for controlling the operation of the engine, the secondary voltages V _HT 1 and V _HT4 of the secondary winding of the ignition coil increase simultaneously and in opposite directions.

The voltage V _PM remains close to O volt until the spark plug of cylinder No. 4 goes into a conductive state.

The voltage V _HT 4 at the terminals of this spark plug then drops suddenly and the voltage V _PM then takes a non-zero value of the sign of the voltage V _HT 1.

The voltage V _PM continues to grow as rises the voltage V _HT 1 until time t ionization _ion of the corresponding spark plug.

After establishment of the electric arc between the electrodes thereof, the voltage V _PM oscillates and is damped as illustrated in FIG. 2.

On the next engine turn, cylinder No. 4 is in the compression phase and the voltage V _PM takes the sign of the voltage V _HT 4 between t _o and t _ion .

The sign of this voltage V _PM therefore provides information on the cylinder in the compression phase.

We can then see that it is possible to use this operating feature to establish a strategy to ensure the identification of the operating cycle of the engine associated with the physical position of the cylinders, so allow synchronization of the injection as soon as engine starter action. vehicle.

This location can be done by acquiring the time elapsing between ignition control and change state of a signal Vs from the ignition coil, this signal being established for example from the value arithmetic mean of the two secondary winding voltages of it, to deliver a representative binary signal of the sign of this average.

This binary signal Vs then comprises representative slots for example of a negative sign of this value average.

The signal Vs, after digital processing, indicates what is the cylinder in compression phase in the pair of cylinders connected to the controlled coil.

In order to guarantee a good robustness of the strategy, at least two successive detections can be planned to confirm the decision.

The signal used to make this determination phase, is a logic signal from the ignition coil which can also be called phase signal.

This signal is produced from the voltages of the ignition coil outputs common to cylinders 1 and 4 for example, that is to say from the voltages V _HT 1 and V _HT 4, by means of conventional type for determining the arithmetic mean value of these two voltages, these means being designated by the general reference 8 in FIG. 1.

The output of these determination means 8 is connected for example to formatting means designated by the general reference 9 integrated for example in the computer 4 for checking the operation of the engine.

These determination means are used in the time interval between t ₀ and t _ion and must then supply an output, a signal Vs with slots having a logic state 1 if the voltage V _PM is negative. Conversely, the logic state of this signal will be 0, if the voltage V _PM is positive.

This is illustrated in Figures 4 and 5.

We recognize in these figures, the signal control Vc of the ignition coil from the control means of power 3 and the output signal Vs of the means of phase detection, including means for determining of the arithmetic mean value of the output voltages of the secondary winding of the ignition coil, connected to shaping means 9.

In fact, the phase information is contained in the measurement of the time elapsing between the ignition command instant of cylinders n ° 1 and n ° 4 and the moment of change phase signal status.

For this purpose, and as can be seen in the figure 4, the output of the shaping means 9 can be connected to a counter designated by the general reference 10, receiving a clock signal CLK and itself associated with means of storage designated by the general reference 11 and to a central information processing unit designated by the general reference 12, of the computer 4, itself connected to the power control means 3 described above to control the operation of the coil ignition and to counter 10 for resetting.

The times acquired during successive ignitions n-1 and n are noted tn-1 and tn in this figure 5.

Their order of magnitude is from 10 to 40µs and in this case, the resolution of the counter 10 for the acquisition of these time must be less than 1µs (frequency of clock signal CLK ≥ 1 MHz).

This measure must not be disturbed by the occupation of the central unit 12 to be used for a priority task.

For this, it is preferable that the counter 10 is reset by the ignition control signal and the phase signal directly triggers the memorization of the state of the counter.

The purpose of signal processing is therefore to correspond to an ignition command of the corresponding coil, the number of the cylinder which is in the compression phase.

The information used is as indicated previously, the time elapsing between the order instant of ignition and the instant of change of signal state phase Vs.

This detection must be error free and the number of ignitions required must be minimal in order not to not extend the vehicle engine start time.

For this purpose, and as can be seen in the figure 6, which represents a flowchart illustrating this operation, after an initialization phase designated by the reference general 13 in this figure, we trigger at 14 and 15, the acquisition of the corresponding time, that is to say tn-1, tn, etc ...

Then, in 16, we carry out for each acquisition, a test to verify that the acquired time, i.e. tn for example, is between minimum threshold values and maximum tmin and tmax.

If the acquired time is outside these limits, the treatment is abandoned and must resume from the start, for the next acquisition.

On the other hand, if the acquired time is well between these limits, and if the acquisition is the initial acquisition, as detected in 17, after the first command ignition, the acquired time tn-1 is compared to a value calibrated ts, in 18.

According to the result of this comparison, a positive sign or negative is memorized for use during a next treatment.

Indeed, if tn-1 is less than this value ts, then a sign for example + is stored in SGN, while that if tn-1 is greater than or equal to this value ts, a sign for example - is stored in SGN.

These steps are illustrated in this figure 6 by references 19 and 20 respectively. These signs indicate the direction of the transition of the next tn.

The acquisition is then incremented during step 21.

When acquiring the time corresponding to the second ignition command, as detected during step 17, the signed difference in time acquired during two successive acquisitions tn- (tn-1) is multiplied by the SGN sign previously memorized in 19 or 20, like this is illustrated in step 22.

The result of this operation named Δtn is then compared to a calibrated threshold, for example positive ts + which represents the magnitude of the transition required to consider the valid test, as illustrated by step 23.

The product with the memorized SGN sign validates that the transition has occurred in the expected direction.

If Δtn is greater than ts +, the phase is determined and the next top dead center of the engine will be known as function of ignition order and pair of cylinders on which the measurement is made. On the other hand if Δtn is lower than ts +, the phase is indeterminate and it is repeated at from step 23, the strategy, using the last value of tn, for the next test.

In steps 24, 25 and 26, you can determine what is the engine operating phase by determining from the next top dead center of a cylinder, to from the memorized sign SGN.

These different steps are implemented by example by the central unit 12 of the control computer 4 engine operation, which can be programmed for this effect.

Different cases of operation of this system are illustrated in Figures 7,8,9,10 and 11.

Figures 7 and 8 illustrate proper operation of the system which determines that the next point dead top will be the one corresponding to cylinder # 2 on the Figure 7 and cylinder # 3 in Figure 8.

Figures 9 and 10 illustrate the case system malfunction due to improper calibration.

Finally, Figure 11 illustrates the case of a reiteration of treatment.

It is therefore conceivable that the determination device according to the invention has an extremely simple structure and reliable which allows precise determination of the operating phase of a motor vehicle engine.

Claims (4)

1. Device for determining the operating phase of an internal combustion engine with simultaneous ignition per pair of cylinders, notably for motor vehicles, wherein spark plugs (7, 6) associated with the cylinders in each pair are connected to the ends of a secondary winding (5) of an ignition coil (1) the primary winding (2) of which receives an ignition command signal (Vc) from control means (3) controlled by a computer (4) monitoring the operation of the engine, characterised in that it comprises means (8) for determining the mean arithmetical value of two output voltages of the secondary winding (5) to deliver a binary signal (Vs) having square pulses representing the sign of this mean, means (9, 10, 11, 12) for measuring the time that elapses between the moment of actuation of the coil by the control means and the moment of the change of state of the binary signal (Vs) for at least two successive actuations of the coil and means (12) for analysing these times to determine the operating phase of the engine.
2. Device according to claim 1, characterised in that the means (12) for analysing the times comprise means for checking that these are between the minimum and maximum threshold values (tmin and tmax), means for comparing the time corresponding to the first command with a predetermined threshold value (ts) for memorising a sign (SGN) as a function of the result of this comparison, means for calculating a differential value (Δtn) by subtracting the two times (tn-1, tn), acquired during successive actuations of the coil, means for multiplying the differential value (Δtn) by the memorised sign (SGN), means for comparing the result of this multiplication with a calibrated threshold value (ts+), to validate the determination of the operating phase of the motor, as a function of the memorised sign (SGN) and the differential value (Δtn).
3. Device according to claim 2, characterised in that the sign (SGN) is obtained from the following equation:
      if t < ts, then sign = +
      if t ≥ ts, then sign = -
      where t represents the corresponding time and
      ts represents the predetermined threshold value, and in that the calibrated threshold value is a positive value (ts+) .
4. Device according to any one of the preceding claims, characterised in that the means for measuring the time comprise a counter (10) associated with memorising means (11) and receiving at its input a clock signal (CLK) and the phase signal (Vs) and, at a resetting terminal, the control signal (Vc) from a central unit (12) of the computer (4).

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