EP1046814B1 - Ignition system for the engine of a motor vehicle - Google Patents

Abstract

Ignition reel has two distinct reels (6, 7) with no magnetic coupling, with secondary windings (8, 9) coupled to spark plug with diodes (10, 11); and with primary windings (12, 13) are attached to controls (14, 15). During first working phase for build up arc between electrodes of spark plug, controls allow simultaneous supply to reels to reach peak arc voltage between electrode During second working phase, controls supply electrodes alternatively for maintaining arc.

Description

The present invention relates to an ignition system for an engine of motor vehicle.

More particularly, the invention relates to a system comprising ignition coil means comprising winding means primary connected to a vehicle power source through means for controlling their supply and winding means secondary connected to at least one ignition coil of the engine.

Ignition systems conventionally used for engines gasoline vehicles indeed have an ignition coil which ensures the energy storage and increasing the voltage applied to the spark plug and more particularly between the electrodes thereof, in order to create therebetween, an arc or spark.

The characteristics of this spark, i.e. its duration and its intensity, depend on one hand, on the surrounding conditions in the room corresponding combustion (aerodynamic pressure, richness, temperature, etc.) and on the other hand, the performance of the ignition system (stored energy, secondary inductance, etc.).

In currently known systems, the generation of the spark is done in two sequential operations, namely a first charging operation during which the coil accumulates a certain amount of energy by feeding its primary winding and a second discharge operation during which the abrupt interruption of the primary current of the coil causes an increase in secondary voltage thereof until generation of the arc between the spark plug electrodes, the energy in the magnetic circuit of the coil dissipating in the arc until its extinction.

The duration of the arc is therefore mainly a function of the energy that can store the coil.

The arc current, representative of the intensity of the spark, is to him function of the impedance of the secondary winding.

These two parameters are paramount for the quality of the inflammation of the mixture in the combustion chamber.

Due to current coil technology, current and arc duration are linked and it is not possible to obtain a significant spark time without also increase the arc current.

The search for high performance in depollution and consumption engines, get manufacturers to run those engines with poor or inhomogeneous mixtures generally combined with a strong aerodynamics in the combustion chamber.

These operating conditions require special performance for the spark, i.e. a long arc duration so that the spark is present for approximately 10 ° of the crankshaft, i.e. a longer duration 2.5ms at engine idle speed and sufficient arc current high so that it resists aerodynamics, but is limited so not to prematurely wear out the spark plug electrodes.

Furthermore, depending on the orientation of the injection jet, in particular in the In the case of direct injection engines, the spark plug is likely to get dirty and it it is therefore preferable to have a low impedance ignition system secondary and whose high voltage rise time is short.

To meet these new needs, ignition systems classics are not suitable.

Indeed, a long arc duration implies using coils bulky, massive and expensive ignition systems that have a magnetic circuit high performance (oriented grain sheets, introduction of magnets permanent, etc.).

In addition, if the arc duration is long, the arc current is generally too large (greater than 100 mA).

Finally, the high inductance of these coils implies times of fairly long high voltage rise (roughly equal to 40µs).

To try to solve these problems, we have already proposed in the state of technique, different solutions.

For example, it has been proposed to use two sources one to create the arc and the other to maintain it.

. It has also been proposed to associate an inductive circuit and a capacitive circuit operating alternately.

Alternative or multi-spark ignitions have also been proposed.

However, the systems for implementing the three first solutions mentioned above result in circuits generally considered too complex.

The fourth solution of multi-spark ignition consists in it to cause a sequence of several short sparks spaced one time required to recharge the coil. The advantage of this solution is that the coil can be compact and has a reduced rise time high voltage.

The overall duration of the spark train can be adjusted according to engine operating conditions.

1) la probabilité d'avoir simultanément l'arc et les conditions gazeuses pour l'initialisation de la combustion, qui est proportionnelle au rapport cyclique des étincelles, et

2) l'usure de la bobine qui est plus rapide, car l'érosion des électrodes est majoritairement due à la phase de création des arcs.

However, the arc is discontinuous which has two drawbacks, concerning:

1) the probability of simultaneously having the arc and the gaseous conditions for the initialization of combustion, which is proportional to the duty cycle of the sparks, and

2) the wear of the coil which is faster, because the erosion of the electrodes is mainly due to the phase of creation of the arcs.

The object of the invention is therefore to solve the problems mentioned previously.

To this end, the invention relates to an ignition system for an engine of a motor vehicle, of the type comprising means forming an ignition coil comprising primary winding means, connected to a vehicle power source through means for controlling their supply and secondary winding means, connected to the minus one engine spark plug. The means forming ignition coil include at least two coils with windings secondary are coupled to at least one candle through means with non-return diode and whose primary windings are associated with control means (compare with 2244 Research Disclosure, 1993, April, No 348, Ensworth, GB). These means allow during a first phase of operation striking an arc between the spark plug electrodes, feeding the coils simultaneously to reach the arc voltage between the electrodes of this spark plug, then during a second maintenance operation phase of this arc, to supply these alternately to supply the arc without interruption.

• la Fig.1 représente un schéma synoptique illustrant la structure d'un premier mode de réalisation d'un système d'allumage selon l'invention;
• la Fig.2 représente différentes formes de signaux illustrant le fonctionnement de ce dispositif; et
• la Fig.3 représente un schéma synoptique illustrant la structure d'un second mode de réalisation d'un système d'allumage 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 the structure of a first embodiment of an ignition system according to the invention;
• Fig.2 shows different forms of signals illustrating the operation of this device; and
• Fig.3 shows a block diagram illustrating the structure of a second embodiment of an ignition system according to the invention.

We recognize in fact in Figure 1, an ignition system for engine of a motor vehicle which comprises means forming an ignition coil, designated by the general reference 1 in this figure, comprising primary winding means, designated by the general reference 2, connected to a power supply source of the vehicle through control means, designated by the general reference 3 in this figure and secondary winding means, designated by the general reference 4, connected to at least one engine spark plug, designated by general reference 5.

In the embodiment shown in this figure 1, the system is associated with a single spark plug 5.

According to the invention, the means forming an ignition coil comprise at least two separate coils, without magnetic coupling, designated by general references 6 and 7, including the secondary windings, respectively 8 and 9 are coupled to the spark plug 5 through non-return diode means 10 and 11 respectively and whose primary windings 12 and 12 respectively 13, are associated with control means 14 and 15 respectively, allowing during a first phase of operation of striking an arc between the spark plug electrodes, to power the coils simultaneously to achieve the arc voltage between the electrodes of this spark plug, then during a second phase of operation, maintenance of this arc, supplying them alternately to feed the arc without interruption.

In the embodiment shown in this figure 1, the control means 14 and 15 each consist of a switching member semiconductor, such as for example by an NPN transistor, associated with the primary winding of each coil while being connected between a terminal this primary winding and the ground, the other terminal of this primary winding being connected to the vehicle's power supply source (+ AC).

In this exemplary embodiment, one of the electrodes of the spark plug 5, like for example the electrode 16, is connected to ground, while the other electrode 17 thereof, is connected to the first terminals of the secondary windings 8 and 9 of the coils 6 and 7, through the non-return diode means 10 and 11, while the second terminals of these windings 8 and 9 are connected to ground.

It can therefore be seen that the secondary windings 8.9 of the two coils separate 6,7 are coupled using two non-return diodes 10,11, to the spark plug 5, and that the control means 14, 15 of the primary windings 12,13 of these coils, are adapted to trigger the operation of these in opposition to a slight overlap.

The sequencing of these commands as well as the voltages and currents which result at different points of the circuit, are illustrated in FIG. 2.

In this figure, Vc1 and Vc2 illustrate the commands applied to the semiconductor switching elements 14 and 15, Ip1 and Ip2 illustrate the current flowing in the primary windings of the coils, Vs1 and Vs2 illustrate the voltages across the secondary windings of these coils and Vs and Is respectively illustrate the voltage and the current at the terminals and in the candle 5.

. It can be seen in the light of this figure 2, that the two coils are first supplied simultaneously.

Thus, the voltages at the terminals of the secondary windings thereof, grow simultaneously, so that the voltage applied to the terminals diodes remains below the breakdown limit thereof.

When the arc voltage is established, the coil 7 is then recharged that the coil 6 supplies the arc.

Before the arc current is canceled, the charge of coil 7 is interrupted and the secondary voltage Vs2 is established at the arc voltage.

The coil 7 therefore takes over to supply the spark plug, while the coil 6 is recharged in turn.

The delay between the order of a coil and the start of recharging of the other coil, ensures the continuity of the arc and avoids applying a voltage too high across the diodes.

The alternating operation of the two coils can continue at will and we can thus create sparks of modular duration.

The current Is circulating in the candle evolves in a sawtooth pattern and a correct adjustment of the coil parameters and excitation times allows to maintain this current between two adjustable limits.

The charging and discharging times of these coils can be adjusted according to their characteristics and it is not necessary to have high energy coils. On the contrary, it is interesting to use low secondary impedance coils including voltage rise time secondary is reduced.

It goes without saying of course that still other embodiments of such a system can be envisaged.

So, for example, such an ignition system can be associated with two spark plugs (twin-static ignition), such as for example 5a spark plugs and 5b illustrated in FIG. 3, in which the other elements are designated by reference numbers identical to those used in Figure 1.

We recognize in fact in this figure 3, the two separate coils 6 and 7, the secondary windings 8 and 9 thereof, the primary windings 12 and 13 thereof, the semiconductor switching members 14 and 15 and the non-return diode means 10 and 11.

In this exemplary embodiment, two candles 5a and 5b are therefore associated, first electrodes thereof being connected together to the mass.

The other electrode of one of the candles, such as for example the candle 5a, is connected to the first terminals of the secondary windings 8 and 9 coils through the non-return diode means 10 and 11, while the other electrode of the other spark plug 5b, is connected to second terminals of the windings 8 and 9 and ground.

The operation of such an embodiment is analogous to that which has been described previously.

It is therefore conceivable that with such a system, it is possible to obtain a continuous spark of adjustable duration without duration limit with an arc current varying in sawtooth between two limits, thus reducing electrode wear of this candle.

Furthermore, such a structure also makes it possible to have a low secondary impedance allowing rapid establishment of high voltage, while implementing low energy coils and suitable for one or more several candles.

Claims (5)

1. Ignition system for an engine of a motor vehicle, of the type comprising means (1) forming an ignition coil comprising means (2) forming a primary winding, connected to a power supply source for the vehicle via means (3) for controlling the supply, and means forming a secondary winding (4) connected to at least one ignition spark plug (5; 5a, 5b) of the engine, the means forming an ignition coil comprising at least two coils (6, 7), the secondary windings (8, 9) of which are coupled to at Least one spark plug via non-return diode means (10, 11) and the primary windings of which are associated with control means (14, 15), characterised in that, during a first operating phase of initiating an arc between the electrodes of the spark plug, these control means allow the coils to be supplied simultaneously in order to achieve the arc voltage between the electrodes of this spark plug, then, during a second operating phase of maintaining this arc, allow the latter to be supplied alternately in order to provide an uninterrupted power supply to the arc.
2. System according to claim 1, characterised in that the control means comprise a semi-conductor switching member (14, 15) associated with the primary winding of each coil (6, 7).
3. System according to claim 1 or 2, characterised in that the two coils (6, 7) are associated with a spark plug (5), one electrode (16) of which is connected to earth while another electrode (17) thereof is connected to first terminals of the secondary windings ( 8 , 9) of the coils (6, 7) via non-return diode means (10, 11), second terminals of these secondary windings (8, 9) being connected to earth.
4. System according to one of claims 1 and 2, characterised in that the two coils (6, 7) are associated with two spark plugs (5a, 5b) the first electrodes of which are together connected to earth, the second electrode of one of the spark plugs (5a) being connected to first terminals of the secondary windings (8, 9) of the coils (6, 7) via non-return diode means (10, 11), and the second electrode of the other spark plug (5b) being connected to second terminals of the secondary windings (8, 9) of the coils (6, 7) and to earth.
5. System according to any one of claims 2 to 4, characterised in that the semi-conductor switching members (14, 15) comprise NPN transistors.

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