EP0736688A2 - Engine phase detection device for an engine with simultaneous ignition in cylinder pairs, especially for automobiles - Google Patents

Abstract

The operational phase detector is for an engine having pairs of cylinders, the mixture in each pair of cylinders being ignited by means of sparking plugs (B1,B4) connected to the respective ends of the centre-tapped secondary winding (1) of an ignition coil (2). The primary winding (3) is connected to a power supply controlled by an engine operation calculator incorporating e.g. a bipolar transistor (4). The alternately positive and negative voltage (Vpm) at the centre tap is applied to a signal detector and shaper comprising a current-limiting resistor (5) and a Zener diode (6). The voltage (Vz) across the Zener represents a pulse for each spark generated in the cylinder concerned.

Description

The present invention relates to a device for detecting the operating phase of an engine with simultaneous ignition by pairs of cylinders, in particular for a motor vehicle.

Are already known in the prior art, devices of this type in which spark plugs associated with the cylinders of each pair, are connected to the ends of a secondary winding of an ignition coil whose primary winding is connected to a computer controlling the operation of the engine through a power stage.

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

It is then necessary to know not only the angular position of the crankshaft, but also the working phase of the engine and more particularly of each of the cylinders thereof.

For this purpose, in the prior art, a sensor is used which detects the angular position of the camshaft.

This device requires, in addition to the sensor, a target associated with this tree and comprising one or more indentations.

It is also possible to carry out this detection by analyzing the ignition signals of the spark plugs associated with the cylinders.

The general principle of this analysis consists in causing the simultaneous ignition of two mechanically synchronized cylinders, that is to say for example cylinders n ° 1 and 4 and n ° 2 and 3 in the case of a four-cylinder engine, and observe the electrical characteristics resulting from the pressure difference in the two combustion chambers corresponding to the instant of the spark.

This second possibility of phase detection and more economical than the first, because it eliminates a specific sensor and its associated target.

However, the analysis of the ignition signals requires means for measuring the voltage across the plugs, as well as a device for filtering and comparing these voltages.

In the case of ignition systems with one ignition coil per pair of cylinders, the useful information is not present at the level of the primary winding of this coil and it is then necessary to carry out a measurement at the level of the winding. secondary of it.

The documents EP-A-272 225, 404 763 and 602 803 propose solutions which consist in placing one or more capacitive sensors on the high voltage wire or wires ensuring the connection to the spark plugs.

However, in the devices described in these documents, it is necessary to carry out an analog comparison of the measured voltages.

• 1) la difficulté de mise au point des moyens de comparaison et des seuils de détection associés;
• 2) le surcoût lié aux étages électroniques de traitement et d'acquisition des signaux; et
• 3) la difficulté d'assurer une bonne protection du calculateur vis à vis de la haute tension.

This has three drawbacks, namely:

• 1) the difficulty of developing the comparison means and the associated detection thresholds;
• 2) the additional cost linked to the electronic signal processing and acquisition stages; and
• 3) the difficulty of ensuring good protection of the computer against high voltage.

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

To this end, the subject of the invention is a device for detecting the operating phase of an engine with simultaneous ignition by pairs of cylinders, in particular for a motor vehicle, in which spark plugs associated with the cylinders of each pair are connected to the ends of a secondary winding of an ignition coil, the primary winding of which is connected to a computer controlling the operation of the engine through a power stage, characterized in that one of the windings associated with the one of the pairs of cylinders is a mid-point winding, and in that it comprises means for detecting and shaping the voltage signal present at this mid-point of the winding, in order to deliver to the computer a signal representative of the phase engine operation.

• la Fig.1 représente un schéma synoptique illustrant un circuit de raccordement de bougies de cylindres associés dans une paire de cylindres d'un moteur à combustion interne et à allumage simultané notamment de véhicule automobile;
• la Fig.2 représente un exemple de signaux de tension en différents points du circuit représenté sur la figure 1 dans le cas où le cylindre n°1 est en phase de compression;
• la Fig.3 représente un premier mode de réalisation d'un dispositif de détection selon l'invention;
• la Fig.4 représente un exemple d'un signal représentatif de la phase de fonctionnement d'un moteur, issu du dispositif de détection représenté sur la figure 3;
• la Fig.5 représente un second exemple de réalisation d'un dispositif de détection selon l'invention;
• la Fig.6 représente des signaux obtenus en différents points du dispositif représenté sur la figure 5; et
• la Fig.7 représente un schéma synoptique illustrant la structure d'un système de contrôle du fonctionnement d'un moteur, comportant un dispositif de détection selon l'invention.

The invention will be better understood on reading 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 illustrating a circuit for connecting spark plugs of cylinders associated in a pair of cylinders of an internal combustion engine and simultaneous ignition in particular of a motor vehicle;
• Fig.2 shows an example of voltage signals at different points of the circuit shown in Figure 1 in the case where the cylinder n ° 1 is in compression phase;
• Fig.3 shows a first embodiment of a detection device according to the invention;
• Fig.4 shows an example of a signal representative of the operating phase of an engine, from the detection device shown in Figure 3;
• Fig.5 shows a second embodiment of a detection device according to the invention;
• Fig.6 shows signals obtained at different points of the device shown in Figure 5; and
• Fig.7 shows a block diagram illustrating the structure of a system for controlling the operation of an engine, comprising a detection device according to the invention.

As can be seen in these figures, a detection device according to the invention is suitable for detecting the operating phase of a simultaneous ignition engine by pairs of cylinders, in particular for a motor vehicle.

In such an engine, spark plugs associated with the corresponding cylinders of each pair, are connected to the ends of a secondary winding of an ignition coil, the primary winding of which is connected to a computer for controlling the operation of the engine. , through a power stage.

In FIG. 1, the spark plugs are designated by the references B1 and B4 for example and correspond to the spark plugs associated with cylinders 1 and 4, for example in the case of a four-cylinder engine.

One of the electrodes of these spark plugs is connected to ground while the other electrodes of these are connected to the corresponding ends of a secondary winding 1, of an ignition coil 2, whose primary winding 3 is associated to supply means controlled by the engine operating control computer, and comprising for example an NPN transistor 4.

In the embodiment shown, the secondary winding 1 is a mid-point winding PM and the detection device according to the invention takes advantage of the fact that the voltage Vpm measured at the mid-point of the secondary winding of the coil, is alternately positive then negative depending on the engine operating phase.

This device is particularly suitable for ignition systems comprising ignition coils, the primary and secondary windings of which are distributed over two separate magnetic cores.

It can be seen, as can be seen in FIG. 2, that during the sparking phase, the voltage Vpm is linked to the voltages V1 and V4 at the terminals of the spark plugs B1 and B4 respectively, by the relation: $$\text{Vpm = V1-V4 / 2}$$

The voltages V1 and V4 are respectively proportional to the pressures P1 and P4 in the combustion chambers of cylinders 1 and 4 of the pair considered.

If cylinder n ° 1 corresponding to spark plug B1 is in the compression phase, then: $$\text{P1 >> P4 =>}\left|\text{V1}\right|\text{>>}\left|\text{V4}\right|\text{=>V1-V4> 0 =>Vpm> 0}$$

On the other hand, if the cylinder n ° 4 corresponding to the spark plug B4 is in the compression phase, then: $$\text{P1 << P4 =>}\left|\text{V1}\right|\text{<<}\left|\text{V4}\right|\text{=> V1-V4 <0 => Vpm <0}$$

It is therefore conceivable that by detecting and shaping the voltage signal present at the midpoint PM of the secondary winding 1 of the ignition coil, it is possible to establish a signal representative of the operating phase of the engine which, once set in shape is directly usable by the engine operation control computer.

This detection and this shaping can for example be carried out by means of a semiconductor member with unidirectional conduction.

An exemplary embodiment of such a device is shown in FIG. 3, in which identical reference numbers designate identical elements already described with reference to FIG. 1.

We recognize in this figure 3, the transistor 4, the ignition coil 2, the primary winding 3 and the secondary winding 1 thereof, and the spark plugs B1 and B4.

In this exemplary embodiment, the detection device comprises a series circuit connected between the midpoint PM of the secondary winding 1 of the coil 2 and the ground and comprising for example a resistor 5 and a Zener diode 6 which clips the voltage signal Vz when Vpm is positive and limits the negative voltage of Vz when Vpm is negative.

Resistor 5 limits the current in the Zener diode.

It can therefore be seen that the signal Vz at the terminals of this Zener diode 6 is a shaped signal which has a voltage pulse for each ignition of the corresponding cylinder as can be seen in FIG. 4.

FIG. 5 shows another embodiment of such a device, in which identical reference numbers also designate elements already described with reference to FIGS. 1 and 3.

We recognize in this figure 5, the transistor 4, the ignition coil 2, the primary winding 3 and the secondary winding 1 thereof, the spark plug B1 and the spark plug B4.

In the embodiment shown in this figure, the midpoint PM of this secondary winding 1 of the ignition coil is connected to a series circuit comprising a resistor 7 and to an opto-electronic coupler designated by the general reference 8.

The opto-electronic coupler comprises for example in a conventional manner a light-emitting diode 9 associated with a photo-transistor 10, while a protective diode 11 is connected to the terminals of this coupler to limit the reverse voltage at the terminals of the latter.

Resistor 7 limits the current in this coupler and fixes the detection sensitivity of the latter.

It will be appreciated that this structure makes it possible to obtain galvanic isolation and therefore greater security in the event of failure of the ignition device.

Is illustrated in Figure 6, the voltage Vi obtained on the collector of the photo-transistor 10 of the opto-electronic coupler when the voltage Vpm is positive. This signal Vi has a negative pulse when the cylinder No. 1 is in the compression phase.

It is therefore conceivable that, thanks to the detection device according to the invention, which delivers, from the voltage signal present at the midpoint of the winding, for example secondary winding of the ignition coil, a signal representative of the operating phase of the engine, this signal can be directly used by the engine operating control computer and more particularly by a micro-controller thereof.

An exemplary embodiment of a system for controlling the operation of an engine is illustrated in FIG. 7, in which there is shown a computer 12 for monitoring the operation of the engine, receiving as input the output of a position sensor of the crankshaft, designated by the general reference 13, this sensor being associated with a target 14, itself associated with the crankshaft and comprising indentations.

More particularly, this sensor 13 is connected to a microcontroller 15 of the computer, this microcontroller having outputs connected to a power stage 16 for controlling the ignition coils as described above.

In fact, this power stage can be connected to one of the terminals of the primary winding 3 of the ignition coil 2, the secondary winding 1 of which is connected to spark plugs for example B1 and B4 of a pair of associated engine cylinders.

The midpoint of the secondary winding 1 of the ignition coil 2 is connected to a circuit similar to that shown in FIG. 5, that is to say comprising a resistor 7, an opto-electronic coupler 8 and a protection diode.

The output of this opto-electronic coupler 8 is connected to the microcontroller 15 of the computer 12 through an input stage designated by the general reference 17 in this figure.

In order to mask the arc establishment phase, which is generally disturbed, the acquisition of the motor operating phase by the microcontroller, from the signal delivered by the opto-electronic coupler, is done after a time delay determined from the instant of ignition.

This time delay can be programmable and is implemented in the microcontroller.

In this case, the value of this time delay can be contained in its memory and calibrated according to the different characteristics of the ignition system.

It can therefore be understood that at each acquisition instant, the signal Vi delivered by the opto-electronic coupler must alternately be in logic state 1 then in logic state 0.

When the operating sequence is recognized by detection of a defined series of alternations, each engine time can be assigned to the corresponding cylinder of the engine according to the ignition order.

The engine is started with group injection.

The microcontroller 15 then detects the angular position of the crankshaft by means of the sensor 13 and determines thus which coil should be ordered and when ignition should be caused.

When the coil is ordered, ignition is caused on a determined pair of cylinders, but the active cylinder remains undetermined.

Once the sequence recognized by detection of the defined sequence of alternations, each engine time being assigned to the corresponding cylinder, the engine control can then pass from the grouped injection mode to the sequential injection mode.

It goes without saying of course that different embodiments of the means for detecting and shaping the voltage signal present at the midpoint of the secondary winding can be envisaged.

It goes without saying also that such a structure can be envisaged with a primary winding at mid point.

Claims (5)

Device for detecting the operating phase of an engine with simultaneous ignition by pairs of cylinders, in particular for a motor vehicle, in which spark plugs (B1, B4) associated with the cylinders of each pair, are connected to the ends of a secondary winding (1) of an ignition coil (2) whose primary winding (3) is connected to a computer (12) for controlling the operation of the engine through a power stage (16), characterized in that the one of the windings associated with one of the pairs of cylinders is a mid-point winding, and in that it comprises means (5,6; 7,8,9,10,11) for detection and shaping of the voltage signal present at this midpoint (PM) of the winding, to deliver to the computer (12) a signal representative of the engine operating phase. Device according to claim 1, characterized in that the detection and shaping means comprise a series circuit connected between the midpoint and the ground and provided with a resistor (5) and a Zener diode (6) to terminals from which the signal representative of the engine operating phase is generated. Device according to claim 1, characterized in that the detection and shaping means comprise a series circuit provided with a resistor (7) and an opto-electronic sensor (8) at the output of which the signal is delivered representative of the engine operating phase. Device according to any one of the preceding claims, characterized in that the primary (3) and secondary (1) windings of the ignition coil (2) are arranged on separate magnetic cores. Device according to any one of the preceding claims, characterized in that the computer (12) is adapted to acquire the phase information on the signal representative of the engine operating phase, with a time delay determined from the instant of ignition of the corresponding spark plugs.

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