ELECTRONIC IGNITION FOR INTERNAL-COMBUSTION ENGINES

Abstract: An ignition system with capacitive knocking ignition for internal-combustion engines, associable to an electric energy generating flywheel, that utilizes a capacitor (C1) discharge means (thyristor SCR) to generate a spark in one correspondent ignition plug (Ca), characterized by the fact that the secondary coil (Ls) has an end electrically connected to the feed coil (Ba) of said generator and an end connected to the ignition plug (Ca) in order to: first of all have a spark on the ignition plug (Ca) deriving from the discharge of said capacitor means (C1) on the primary winding (Lp), inducing tensions with high potential on said secondary winding (Ls) and then that such feed coil (Ba) of said electric energy generator sets provide furthermore and directly current to said secondary coil (Ls) to prolong the duration of the spark.

Description: DESCRIPTION ELECTRONIC IGNITION FOR INTERNAL- COMBUSTION ENGINES The object of the present invention is an electronic ignition for internal-combustion engines. The invention is particularly, even if not exclusively, applied as an ignition system for olio cycle small size two-stroke internal- combustion engines, particularly for motorcycles and mopeds, not excluding its application on small internal-combustion engines destined to other uses, like chain saws, bush mower, mowers, portable generators, etc. The electronic ignitions of the internal-combustion engines in these sectors are divided substantially in two great families: Capacitive knocking ignitions and inductive knocking ignitions depending on the use of the stored energy coming from a capacitor or from an inductance. Such groups also get marked out for the very different characteristics and performances they have one from the other. The capacitive knocking ignitions, having the possibility of utilizing higher spark currents and high tensions with higher uprisings, are particularly utilized in engines where a good starting is garanteed, even if there is the problem of fouling the spark plugs (originated for example, by the presence of oil in the fuel mixture of the two stroke engines). The inductive knocking engines, with the possibility of using longer life sparks, arc particularly utilized in the motors in which antipollution norms should be respected, such norms imposing the use of particularly lean air-gasoline mixes, limiting the output of unburnt hydrocarbons. The ideal electronic ignition therefore is the one that, even when disposing of high peak powers and of high tensions with fast uprisings, also keeps high long lasting of sparks. We got these results as claimed by a circuital solution consisting in a capacitive knocking ignition system for internal-combustion engines, associablc to an electric energy flywheel generator, that uses a capacitor discharge device ( for example a thyristor "SCR") or other equivalent ones to generate a spark in a correspondent ignition plug, characterized by the fact that the secondary winding has an end electrically connected to the feeding coil/s of such generator and an end connected to the ignition plug so that: - first of all there be a spark on the ignition plug due to the discharge of such capacitive means on the primary winding inducing high power tensions on said secondary winding, and then - that the said feeding coil/s of the electric power generating sets be charged to supply more power and to do this directly to the said secondary winding in order to extend the duration of the spark. These and other advantages will be outlined on the following detailed description of preferential solutions of realization with the help of the enclosed drawings to which details are not to be considered as limitative but only exemplificative. 1 Figure 1 represents a schematic view of a general circuital system 2 with P.U. in which the connection system of the ignition coil is 3 applied according to the invention. 4 Figure 2 represents the behavior diagrams of the exhaust of the 5 ignition spark, respectively feeding tension, maintenance tension 6 and discharging current. 7 Figures 3 and 4 represent iwo schemes of possible applications and 8 existing solutions without P.U., the latter with the system utilizing 9 capacitive inductance (system type WO-89/05035 corresponding to I 0 the IT-A-83490/87 and IT-A-83491/87). I I In the schemes with Ba the feeding coil is indicated (obviously in 1 2 the generators the feeding coils can be more than one and they 1 3 make part of a stator group around which a flywheel with North- 1 4 South magnetic sectors turns around, as for example illustrated in 1 5 the EP-A-88110152.1 corresponding to the IT-A-83445/87, or even in 1 6 the version described in IT-A-83393/90 in the name of the applicant 7 and of other possible innumerable applicants). 8 The ignition control is supplied by means of a Pick-Up for example 9 according to the solution proposed by the applicant by means of the 0 PCT WO-89/05035, or by means of an electronic elaboration system 1 directly from the feeding coil/s of the applicant IT-A-83417/90 with 2 the advantageous solution that presents however the inconvenient 3 of a quite short ignition (with all the capacitive knocking 4 ignitions). 5 With reference to a solution with Pick-Up and use of a capacitor 6 discharged by thyristor as for example indicated in Figure 1, we can 7 note that during the positive half-wave of the tension of the feed 8 coil Ba, the diode Dl is polarized directly and the thyristor is not started, so the electric current flows from the feeding coil "Ba" through Dl ,Cl ,D2,to gel-closed al ground, and charges the condenser Cl up to a certain power rale. When the power of the feeding coil Ba reverses its own polarity sign, the diode Dl gets polarized inversely and in this phase having reached a certain potential "Va", the start command is given to the gate (G) of the thyristor, allowing the discharge of the capacitor Cl on the primary winding Lp. Said start command comes from a rotoric position detector that sends electric impulses (P.U.) Fig.l , or directly from the feed coil/s Ba of said electric energy generator set (Figures 3-4). The discharge current flowing from Cl , across the started thyristor (SCR), and the primary coil (Lp), transfers the energy from such condenser Cl to said primary winding Lp, exhausting itself on diode D2. The power transmitted to the primary coil Lp, is transferred to the secondary Ls, to which il is coupled where a high potential is inducted such to starl a spark on the ignition plug Ca. The spark current initially flows through Dl, polarized now directly by the positive potential induced on the secondary coil Ls, and through the thyristor getting started towards ground. When instead the induced positive potential, on the secondary coil Ls goes down, because the power rate on the primary coil Lp is going down, originated by the conduction of D2 and reaches the negative one of the feed coil Ba, the diode Dl gets polarized inversely again, in order to prevent the passage of the spark current that therefore flows through the feed coil Ba. In this instant (Sec "Va" Fig.2 ) being the negative power rate "Va" of the feed coil Ba greater than the maintenance tension "Vm" of the spark, even if the potential induced on ihe secondary winding Ls is already exhausted, wc have a prolongation of the duration of the spark until the negative potential "Va" of the feed coil Ba be greater than the maintenance tension "Vm" of the spark passing this way from a time that in the prior technique was "l", to a time much higher "T". To avoid dangerous overpowers, a tension limiter gets in, in parallel to the feed coil/s "Ba"" made for example with a series of zener Dzl, ... Dzn or with a variator or olhcr similar devices preceded by a diode D6 (See Figures..1 ,3,4) Idling this way unaltered the positive half- wave, for the charge of capacitive means (Cl) and limiting the negative one to a value not too high , but however higher than the maintenance tension of the "VM" spark in order to guarantee the deriving advantages coming from the circuital solution in object and simultaneously not damaging the electronic components . An example of a concrete application can be made with the circuit of Fig.3 or Fig.4. The second utilizing a inductor-capacitor in reference at IT-A-83393/90 of the applicant and regarding a capacitive knocking ignition system, characterized by the fact that the piloting of the thyristor is carried out on its cathode through a branch with high impedance with the gate of the thyristor electrically connected to ground. The importance and the greal originality of the invention is therefore clear: in order to achieve the abovementioned advantages, it is sufficient to change the connection of the secondary winding Ls, while one end keeps on being connected to the ignition plug Ca, the other one instead of the primary winding Lp, is connected to the feed coil Ba as to Figures..1,3,4., To be able appreciate the advantages of a solution so simple and so unthinkable it may be proper to make reference to the behavior diagrams of the discharge in time, outlined in Figure 2 where you can realize that: - the first diagram indicates the behavior of the feeding tension Va in the coils of the generator (Ba) in which there is a first charging phase of the capacitive means (Cl) and then the insertion of the thyristor in the negative half-wave and a successive conduction phase Dl-SCR and finally the development of the behavior of the feeding tension during the limited discharge at a certain value "VI" greater than the maintenance tension of the spark.. - the second diagram indicates the behavior of the maintenance tension "Vm" that after an initial starling peak of the spark remains constant around 600-700 V. - the third diagram displays the behavior of the intensity of current of the spark where we can detect that while at first the discharge was going on for an average value of t = 150 microseconds, now it has become a time sensitively greater and more than two times to T= 400 microseconds.

Claims: CLAIMS 1. An ignition system with capacitive knocking ignition for internal-combustion engines, associabie to an electric energy generating flywheel, that utilizes a capacitor (Cl) discharge means (thyristor SCR) to generate a spark in one correspondent ignition plug (Ca), characterized by the fact that the secondary coil (Ls) has an end electrically connected to the feed coil (Ba) of said generator and an end connected to the ignition plug (Ca) in order to: - first of all have a spark on the ignition plug (Ca) deriving from the discharge of said capacitor means (Cl) on the primary winding (Lp), inducing tensions with high potential on said secondary winding (Ls) and then - that such feed coil (Ba) of said electric energy generator sets provide furthermore and directly current to said secondary coil (Ls) to prolong the duration of the spark. 2. An ignition System according to claim 1, characterized by the fact that in parallel with feed coil (Ba), a tension limiter is inserted in order to not alter the positive half-wave for charging the capacitor means (Cl), and to limit the negative one to a value not excessively high but anyway higher than the maintenance tension (Vm). 3. An ignition System according to claims 1,2 characterized by the fact that said tension limitcr is made with a series of of Zener diodes (Dzl .... Dzn) preceded by another diode or equivalent in a unidirectional way to the current (D6). 4. A capacitive discharge ignition device for internal- combustion engine according to claim 1 , characterized in that the control signal of the ignition discharge of said capacitive means (Cl) is generated during the negative half- wave of the tension of the feed coil (Ba) from a rotoric position detector thai sends electric impulses (Pick- Up) associated to the Gate command system of a respective thyristor meant to consent the discharge of said capacitive means (Cl). 5. A capacitive discharge ignition device for internal-combustion engines, according to claim 1, characterized in that said capacitive means (Cl) are coaxially integrated in the respective inductance means (Lp-Cl). 6. A capacitive discharge ignition device for internal- combustion engines according to claim 1 , characterized in that the piloting of the thyristor is carried oui on its cathode directly by feed coil (BA) through a branch with high impedance with the gate (G) of the thyristor electrically connected to ground.

Inventors: REGAZZI GIANNI, VENTUROLI GIANNI, REGAZZI, GIANNI, VENTUROLI, GIANNI
Applicants: DUCATI ENERGIA SPA, DUCATI ENERGIA S.P.A.
Application year: 1991
Main classification: F02P1
IPC codes: F02B61, F02B75, F02P1, F02P3, F02P9