EP0181961B1 - Impulse oscillator ignition system for an internal-combustion engine - Google Patents

Description

The invention relates to an ignition system for an internal combustion engine with a capacitor and an ignition coil, which comprises a primary winding connected to an ignition current switching unit and a secondary winding connected to the primary winding in an autotransformer series circuit.

An ignition system of this type is known from "The great book of automotive electrics", 1973, pages 136 to 142. In this ignition system, the primary winding of the ignition coil, which is designed as an autotransformer, is connected in series to an interrupter contact to a battery. When the breaker contact opens, the current in the primary winding is suddenly interrupted, as a result of which a high voltage is induced in the secondary winding of the ignition coil. A capacitor is connected in parallel to the interrupter contact, which stores the opening induction voltage which arises when the contact opens until the distance between the contacts of the opening interrupter is so large that no arc arises at the interrupter contact.

To improve the ignition, it is also known (EP-A-0 018 620, FIG. 1) to connect a capacitor to ground in parallel with the spark gap and flashover path. However, this circuit has the disadvantage that the voltage rise is too slow. This is due to the impedance of the long current path on which the high-frequency current signal must be routed through the widely branched casting of the engine block. In particular, in the known ignition system, the charging and discharging process is carried out via a current path formed by a series resonant circuit.

Finally, an ignition system is known from US-A-2,981,865, whose ignition transformer comprises a plurality of primary windings in addition to a secondary winding. One of the primary windings, together with a capacitor, forms the output resonant circuit of a transistor oscillator operating as a blocking oscillator. Another primary winding forms a feedback winding for the oscillator. The blocking oscillator is controlled by an interrupter contact and oscillates as long as the interrupter contact is closed, the alternating magnetic field of its output circuit inducing high-voltage oscillations in the secondary winding.

It is an object of the invention to provide an ignition system which, despite a very simple circuit, generates a high oscillating ignition voltage.

This object is achieved in that the capacitor is connected on the high voltage side to the secondary winding to form a pulse oscillator and the series connection of primary winding and secondary winding is connected in parallel. Based on the series connection of the windings, the capacitor forms a parallel resonance circuit whose resonance oscillations increase the high voltage induced on the secondary side when the primary current is interrupted. Charging and discharging take place here via separate lines. In particular, the capacitor does not directly bridge a spark gap, but its circuit closes via a primary electrolytic capacitor of the ignition coil or via the vehicle electrical system (battery).

Previous tests and measurements have shown that even extremely lean fuel-air mixtures can be ignited perfectly. The pollutants in the exhaust gas are thus reduced to a maximum and internal combustion engines can be operated in the lean range without misfiring.

In an expedient embodiment, the primary winding of the ignition coil is charged with a negative current potential by the charging current of the capacitor lying parallel to the primary and secondary windings, which accelerates the magnetic field breakdown and thus induces a higher voltage on the secondary side. This process is repeated until a flashover occurs on the respective discharge route or routes.

In contrast to previous designs, the ignition system can include an attenuator, which allows the duration of the ignition current to be extended.

Another capacitor can be connected to the primary winding parallel to the arcing distance of the distributor, which leads to a further increase in the ignition voltage and to an almost complete reduction of the magnetic field during the ignition process.

In order to enable a high efficiency of the current transmission at the flashover section of the distributor and thereby to ensure a maximum filling of this additional capacitor, it is necessary to coat the cathode surface of the distributor finger with metal, which opposes a low work function.

So that the impedance of the pulse oscillator ignition system can be adapted to the respective requirements of the transmission parts leading to the spark plug tuning plug, a tunable voice coil is provided parallel to the primary winding. With the spark plug tuning plug, the impedance of the spark plug of the ignition system is adjusted.

It has been found that an electrolytic capacitor of a certain size against ground is necessary for the energy supply of low-resistance ignition coils or ignition transformers. As a result, a drop in the charging voltage is prevented when the maximum charging current of the ignition coil is reached, so that a higher amount of energy is magnetically stored in the ignition coil can be.

Brief description of the drawing

• Fig. 1 eine schematische Darstellung einer erfindungsgemäß als Impulsoszillator ausgebildeten Zündanlage;
• Fig. 2 eine Impulsoszillator-Zündanlage gemäß Fig. 1 unter Einbeziehung der Uberschlagstrecke eines Zündverteilers, wobei ein Kondensator 12 als Speicherelement herangezogen wird.
• Fig. 3 eine Zündanlage gemäß Fig. 1, wobei ein Widerstand 42 bestimmter Größe und Induktivität sowie Kapazität als Dämpfungsglied herangezogen wird;
• Fig. 4 eine Zündanlage gemäß Fig. 1, bei der ein Elektrolytkondensator 32 für die Bereitstellung von hoher Energie sorgt;
• Fig. 5 eine Variante der Zündanlage gemäß Fig. 1, bei der die Schalteinheit an die Plusseite (+) der Zündspule verlegt ist;
• Fig. 6 die Zündanlage gemäß Fig. 5 mit einem Elektrolytkondensator gemäß Fig. 4 für Energiebereitstellung;
• Fig. 7 eine Impulsoszillator-Zündanlage gemäß Fig. 2, jedoch mit einem Elektrolytkondensator 32 gemäß Fig. 4 und einer abstimmbaren Schwingspule 19 zur Änderung der Funkenstandzeit;
• Fig. 8 einen Verteilerfinger, dessen Katodenfläche 26 mit Selen oder anderen Halbleitern beschichtet ist, um eine möglichst hohe Stromführung im Lichtbogen zu erreichen und
• Fig. 9 einen Zündkerzenabstimmstecker, bei welchem mittels Ferritkern 48 die Induktivität einer aus Widerstandsdraht gewickelten Anpaßspule an die Impedanz der Zündkerze an die Zündanlage angepaßt werden kann.

It shows:

• Figure 1 is a schematic representation of an ignition system designed according to the invention as a pulse oscillator.
• 2 shows a pulse oscillator ignition system according to FIG. 1, taking into account the flashover distance of an ignition distributor, a capacitor 12 being used as a storage element.
• 3 shows an ignition system according to FIG. 1, a resistor 42 having a certain size and inductance and capacitance being used as an attenuator;
• FIG. 4 shows an ignition system according to FIG. 1, in which an electrolytic capacitor 32 provides high energy;
• 5 shows a variant of the ignition system according to FIG. 1, in which the switching unit is moved to the plus side (+) of the ignition coil;
• 6 shows the ignition system according to FIG. 5 with an electrolytic capacitor according to FIG. 4 for energy supply;
• FIG. 7 shows a pulse oscillator ignition system according to FIG. 2, but with an electrolytic capacitor 32 according to FIG. 4 and a tunable voice coil 19 for changing the spark life;
• 8 shows a distributor finger, the cathode surface 26 of which is coated with selenium or other semiconductors, in order to achieve the highest possible current flow in the arc and
• 9 shows a spark plug tuning plug in which the inductance of a matching coil wound from resistance wire can be adapted to the impedance of the spark plug to the ignition system by means of ferrite core 48.

1 to 6, 8 and 9 show basic circuit diagrams and details of the pulse oscillator ignition system shown in detail in FIG. 7, the same parts being designated with the same reference numbers.

The efficiency of the ignition system is determined by the ignition coil and the pulse oscillator, wherein a tunable coil 19, the inductance of which can be changed by changing the position of its core 21, allows adaptation to the respective requirement. When the ignition current is switched on, a capacitor 32 is charged from a point 29 via a line 31, a point 16 and a line 15 to the ignition lock from the battery. By applying a control signal from a control device (contacts) via a line 34 to a switching unit 35, the negative side of the capacitor 32 is connected via a line 31, a point 30, a line 33, the switching unit 35 and a line 8 with connection points 20 and 36 the coil 19 and the primary winding 5 connected. From points 18 and 4, line 3 leads the current back via points 17 and 16 of lines 15 and 2 to the positive plate of capacitor 32. A magnetic field is built up in the cores 10 and 21 by the current flow in the primary winding 5 and the coil 19. By changing the control signal in the primary winding 5 and the coil 19, the charging current is interrupted and the magnetic field begins to collapse in both cores 10, 21. The result of this is that an oppositely directed voltage builds up in the windings 5, 22 and the coil 5. A capacitor 7 is now charged from a point 23 of a line 25 and a point 24 of a line 9. The current flowing in the opposite direction via a line 6, a point 1, line 2, point 16 of line 15 at point 17 and via line 3 to points 4 and 18 accelerates the field degradation in the cores 10 and 21 the windings 5.22 increases the voltage. When the breakdown voltage is reached at a cathode 26 of a flashover path 14 of the distributor via a line 25, a high-energy arc is formed, which in turn charges a capacitor 12 via the anode 27, a point 28, and a line 13. The current flowing via line 11 and point 1, line 2, points 16 and 17 of lines 15 and 3 to points 4 and 18 causes a greatly accelerated field breakdown in coil 5 and windings 5, 22. This continues until the capacitor formed by the spark plug is charged to such an extent that the distance between the electrodes is ionized. An arc is formed from the current of the candle capacity. This has the consequence that the voltage at the candle breaks down (up to about 50 V). The current now starting from the capacitor 12 via the arc path of the distributor finger 40 and the capacitor 7 via a line 37, the connection point 44 of a candle adapter plug 50, a Winding 45 to connection point 46 ensures that the arc is maintained at the candle with the highest energy. The current flowing in the spark plug tuning plug 50 is then in turn braked by an oppositely directed voltage, which can be influenced by a core 48 in a carrier 47 in such a way that the current flows simultaneously from the deposits on the capacitors 12 and 7 and the secondary winding 22 via ground 29 , the line 31, the capacitor 32, the line 2, the point 16 of the line and 2, the points 1 and 17, the lines 3, 6 and 11 in the coil 19 and the primary winding 5 and the capacitors 7 and 12 flows back.

Claims (4)

1. Ignition system for an internal combustion engine with a capacitor (7) and an ignition coil, which comprises a primary winding (5) connected to ignition current switching unit (35) and a secondary winding (22) connected to the primary winding (5) in an auto-transformer series circuit,
characterised in that to provide an impulse oscillator the capacitor (7) is connected to the secondary winding on its high voltage side and is connected in parallel to the series circuit of the primary winding (5) and the secondary winding (22).

2. Ignition system according to claim 1, characterised in that the primary winding (5) is connected in parallel with an adjustable coil (19).

3. Ignition system according to claim 1 or 2, characterised in that for connecting the secondary winding (22) with a spark plug, a spark plug insert (50) is provided which comprises in a carrier body (47), a winding (45) with an insertible core (48).

4. Ignition system according one of claims 1 to 3 wherein a spark distributor (14) is connected to the secondary winding, characterised in that a resistor (42) is connected to the spark distributor on the load side and that a further capacitor is connected in parallel to the series circuit of the primary winding (5) and secondary winding (22) with the inclusion of the spark gap of the spark distributor (14).

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