DE102022207487A1 - Ignition device for an internal combustion engine - Google Patents

Abstract

The invention relates to an ignition device (2) for an internal combustion engine, comprising a generator (4), which generates an oscillating generator current in generator operation, a rectifier (G1) for converting the generator current into a rectified charging current (I), and an ignition capacitor (U4). Energy storage for an ignition spark (20), the ignition capacitor (U4) being chargeable by means of the charging current (I), and an ignition transformer (U5) with a primary coil (Lp) and with a secondary coil (Ls), the secondary coil (Ls ) is connected to a spark plug (8) generating the ignition spark (20), the ignition capacitor (U4) being connected in parallel to the primary coil (Lp), with a first semiconductor switch (U9) between a base point of the primary coil (Lp) and a ground potential ( GND) is connected, and the spark plug (U8) generates the ignition spark (20) by capacitor ignition, in which the first semiconductor switch (U9) is closed, so that the charged ignition capacitor (U4) discharges via the ignition transformer (U5).

Description

The invention relates to an ignition device for an internal combustion engine. The invention further relates to an internal combustion engine with such an ignition device and to the use of such an ignition device.

Hand-held or hand-carried internal combustion engines as work tools, such as chainsaws, leaf vacuums (leaf blowers) or lawn mowers, are usually powered by motors. If these implements are to be operated essentially self-sufficiently or over a comparatively long period of time, an internal combustion engine is usually used as the drive motor. The reason for this is that refilling fuel can be done in a comparatively time-saving manner and only comparatively robust tools are required. It is also possible to store implements powered in this way over longer periods of time, whereas in the case of electric motor implements powered by a battery, any discharge of the battery must be taken into account before use. The internal combustion engine is designed in particular as a small engine, with a small engine particularly including a two-stroke engine with a displacement of up to 350 cm ³ (cubic centimeters) and/or a four-stroke engine with one or two cylinders and a displacement of up to 1000 cm ³ is understood.

To supply an electrical consumer with (electrical) energy during the starting process (cranking process) of the internal combustion engine, for example, a battery or a generator is used. Disadvantageously, however, the battery can be discharged, especially after a comparatively long storage period of the implement. In addition, the capacity and/or performance of the battery decreases over the lifespan of the implement due to aging processes.

To operate such an internal combustion engine, an ignition device (ignition system) is usually provided, which ignites an air-fuel mixture in a combustion chamber. Such ignition devices generate an ignition spark or ignition pulse that triggers the combustion, which is created by a discharge of an ignition capacitor on a spark plug within the combustion chamber.

A basic structure of such an ignition device is shown in 1 shown and explained below. The ignition device 2' shown is in particular a magneto ignition system with a capacitor ignition or with a thyristor ignition.

The ignition device 2' has a (magnetic) generator 4', which comprises an electric motor (not shown) mounted on a crankshaft with a magnet wheel P' as a rotor with at least one peripherally arranged magnet M'. The rotation or direction of rotation is indicated with an arrow. At the north and south poles of the magnet M' there is a pole piece N', S'. This magnet arrangement M', N', S' is moved along an iron core K' with two legs Ka', Kb' with each revolution of the magnet wheel P'.

The leg Kb' is surrounded by an ignition transformer U5' and optionally by an ignition or trigger coil U2', while the opposite leg Ka' is surrounded by a charging coil U1'. When rotating, the magnetic field generated by the generator 4' - amplified by the iron core K' - induces a (generator) voltage or a (generator) current in the charging coil U1' and, if necessary, the trigger coil U2' or the ignition transformer U5'.

The generator 4' or the charging coil U1' generates sinusoidal current half-waves LSp', LSn', which are used to charge an ignition capacitor U4' via a rectifier G1', which is connected to the ignition transformer U5' in order to produce an ignition spark 6'. in a spark plug FU'. The ignition transformer U5' has a primary winding Lp' and a secondary winding Ls'. Here and below, “(charging) the ignition capacitor” is understood to mean in particular the (charging) of such a capacitive energy storage device with electrical energy.

A voltage supply U10' for a controller U8' is also supplied with energy with the negative current half-wave LSn' via the charging coil U1'. The power supply U10' generates a supply voltage VDD' based on the generator current LSn' and provides the supply voltage VDD' for the controller U8'.

The generator current charges the ignition capacitor U4' via the primary winding (primary coil) Lp' of the ignition transformer U5' which is connected in series with it, for example against mass or ground.

The controller U8' has a control output which is connected to a control connection of a thyristor (ignition switch) U9'. The controller U8' sends an ignition pulse that activates the thyristor U9' via the control output for activation. When the thyristor U9 is actuated, the ignition capacitor U4 'is discharged via the primary winding Lp' of the ignition transformer U5' and subsequently through the secondary winding Ls' of the ignition transformer U5' generates a high-voltage pulse. This high-voltage pulse in turn causes the ignition spark 6' on the spark plug FU' as a sparkover, which can be used in an internal combustion engine to ignite an air-fuel mixture in a combustion chamber. The ignition capacitor U4' and the ignition transformer U5' form a resonant circuit in which the primary current is heavily damped and comes to a standstill after about two to four half-waves.

After the ignition process, the thyristor U9' blocks its conductive channel because the ignition current drops and the specific holding current of the thyristor is undershot. Only after the thyristor U9' has blocked can the ignition capacitor U4' be charged again, otherwise the generator current of the charging coil U1' would be short-circuited by the thyristor U9'.

The rectifier G1' “brings” or folds the negative current components (half-waves) LSn’ into positive polarity. This means that a resulting charging current I' after the rectifier G1' only has positive current values. The disadvantage is that this rectified charging current I' never becomes completely zero due to the capacitance (ignition capacitor U4') when the thyristor U9' is switched on. In other words, some current constantly flows through the commonly used ignition thyristor U9'. This means that the holding current of the thyristor U9' is not undershot, and the thyristor U9' cannot therefore go into the blocking state. The entire charging current I' then flows through the thyristor U9', causing it to be subjected to severe thermal stress or even overloaded.

As a rule, the charging coil U1' does not continuously generate current over the 360° crank circle angle, but only at an angle of approximately 120° (charging period). In the remaining 240° crank circle angle, the charging coil U1' does not supply any current or voltage, so that the thyristor U9' typically has enough time to block and cool down during this period.

The disadvantage, however, is that once the ignition capacitor U4' has been discharged, it cannot be charged again immediately, since the charging current I' flows through the thyristor U9' to ground GND'. A renewed ignition process is therefore only possible again in a subsequent charging period and/or charging half-wave.

This means that with the ignition device described above, no second, third, fourth... ignition spark can be generated during a single charging period. However, such functionality, also known as multiple ignition sparks, is increasingly desired in ignition technology, since with this functionality the ignition duration - and thus the ignition energy - can be set variably as required. Such multiple spark systems are becoming increasingly important due to current engine development (stratified charging, supercharging, lean-burn engines, etc.).

To realize multiple ignition sparks, the thyristor U9' could be replaced by a circuit breaker, for example. If the thyristor U9' in the 1 If a capacitor ignition were to be replaced by a circuit breaker or a similar component, then a second problem would arise. As explained above, the charging current I' after the rectifier G1' is positive in the form of alternating half waves. The level of the current (peak or peak value) depends on the design and the speed of the magnet wheel P'. At the time of the ignition spark, when the circuit breaker U9' is switched on, the ignition current and the charging current I' are superimposed, which puts extreme thermal stress on the circuit breaker U9'. The magnet wheel P'"pushes" charging current I' through the circuit breaker U9' for practically the entire duration of the ignition process. This charging current I' is added to the current of the actual capacitor alternating current of the ignition spark. This means that the power semiconductor U9' would have to be designed or dimensioned extremely large in order to safely dissipate the resulting power loss.

The invention is based on the object of specifying a particularly suitable ignition device. In particular, a structurally simple and effective generation of multiple ignition sparks should be made possible. The invention is also based on the object of specifying a particularly suitable internal combustion engine and a particularly suitable use of such an ignition device.

With regard to the ignition device, the task is solved according to the invention with the features of claim 1 and with regard to the internal combustion engine with the features of claim 9 and with regard to use with the features of claim 10. Advantageous refinements and further developments are the subject of the subclaims. The advantages and refinements mentioned with regard to the ignition device can also be transferred to the internal combustion engine and/or its use and vice versa.

The ignition device according to the invention is designed, for example, as an ignition system or as an ignition module for an internal combustion engine. The internal combustion engine is in particular a hand-held or hand-held one portable internal combustion engine with an internal combustion engine designed in particular as a small engine. During operation of the internal combustion engine, a pulse-shaped ignition signal is generated when the ignition device is ignited, that is, when an ignition spark is generated to trigger the combustion of an air-fuel mixture in a combustion chamber of the internal combustion engine.

The ignition device here has a generator, which generates an oscillating generator current in generator operation. The generator can be a magnetic generator with a magnet wheel.

The ignition device also has a rectifier, i.e. a rectifier module or a rectifier circuit, for converting the generator into a rectified charging current. The generator current has positive and negative current half-waves, with the rectified charging current in particular only having positive current half-waves.

The ignition device comprises an ignition capacitor for storing energy for an ignition spark, wherein the ignition capacitor can be charged by means of the charging current. This means that the rectifier is connected between the generator and the ignition capacitor.

The ignition device also has an ignition transformer, also referred to as an ignition generator, ignition coil or ignition transformer. The ignition transformer here comprises a primary coil and a secondary coil, which preferably have the same number of turns. The secondary coil is connected to a spark plug that generates the spark.

According to the invention, the ignition capacitor is connected in parallel to the primary coil of the ignition transformer, with a first semiconductor switch being connected between a base point of the primary coil and a ground potential (ground). The spark plug generates the ignition spark through capacitor ignition, in which the first semiconductor switch is closed so that the charged ignition capacitor discharges via the ignition transformer. This discharge of the ignition capacitor corresponds to the ignition signal. This creates a particularly advantageous ignition device.

In contrast to the above in 1 According to the invention, in the ignition device described, the ignition capacitor is not connected in series with the primary coil, but rather in parallel with the primary coil. In principle, this circuit arrangement of primary-secondary coil and semiconductor switch is known from ignition devices with a transistor ignition. With a transistor ignition, the transformation ratio (number of primary turns to number of secondary turns) of the transformer is by definition different and no ignition capacitor is used as an energy storage for the ignition spark. By definition, the present structure is still a capacitor ignition, but supplemented with circuit features of a transistor ignition. The charging and ignition process also corresponds to a capacitor ignition. The energy storage device must be charged and is ignited by turning on the first semiconductor switch and not by turning it off, as would be the case with a transistor ignition.

Due to the circuit design of the ignition device according to the invention, the charging current is firstly buffered by the capacitance of the ignition capacitor, so that the high peak values of the charging current are reduced, and secondly, the coupled primary coil inductance of the ignition transformer greatly slows down the time-varying charging current. This advantageously reduces the requirements for the dimensioning of the first semiconductor switch.

A second effect is also particularly advantageous. During the ignition process, the first semiconductor switch is activated, i.e. put into the conductive state. The generator windings of the generator are also short-circuited. The corresponding short-circuit current flows through the generator, whereby the inductance of the generator is energetically charged. If the first semiconductor switch is now switched off, the current through this circuit is suddenly set to zero. The inductance of the generator now behaves like a boost converter/boost converter/step-up converter. The amount of energy stored in the inductance of the generator is released when the first semiconductor switch is switched off in the form of a generator current that continues to flow, so that the ignition capacitor can be charged with this energy within a short time. The relationship E = 1/2 LI ² applies to the amount of energy stored in the generator, where L is the (generator) inductance and I is the current flowing through the inductance.

Practical tests show that immediately (within a few nanoseconds ns) after switching off the semiconductor switch, the ignition capacitor reaches up to 80% of its nominal charge through the effect described, without the conventional charging process of the ignition capacitor taking place by the generator. This makes it possible to generate further ignition sparks as required immediately after the ignition spark has been generated. In particular, there are more more immediately successive ignition sparks during a single charging period. This means that the ignition device according to the invention is intended for generating multiple ignition sparks and is suitable and set up for this purpose.

The generator system is preferably designed in such a way that it has the highest possible short-circuit current. According to the invention, a high short-circuit current is more important than a high output voltage. The generator therefore has a high inductance. Highly magnetized magnets (rare earths, neodymium) are preferably used for the generator.

In an advantageous embodiment, the first semiconductor switch is designed as a power switch (power semiconductor switch). The advantage of using a power switch such as an ignition IGBT (transistor, Mosfet, etc.) in contrast to an ignition thyristor is that the first semiconductor switch can be actively switched off. This means that the thyristor problems described above can no longer occur when switching off and charging the ignition capacitor.

Preferably, the first semiconductor switch or the power switch is designed as an ignition IGBT (IGBT: Insulated-Gate Bipolar Transistor), which is connected on the collector side to the base of the primary coil and on the emitter side to the ground potential. The ignition IGBT is preferably designed as a normally conducting n-channel IGBT.

On the control side or gate side, the ignition IGBT is connected in particular to a controller (i.e. to a control unit). The controller is generally set up - in terms of program and/or circuitry - to carry out the capacitor ignition. The controller is therefore specifically set up to switch on the ignition IGBT, i.e. to open it or switch it non-conductive, so that the ignition capacitor is charged with the charging current, and to switch off the ignition IGBT, i.e. to close it or switch it to conduction, in order to do so Discharge the ignition capacitor via the ignition transformer and subsequently generate the ignition spark.

In a preferred embodiment, the controller is formed at least in the core by a microcontroller with a processor and a data memory, in which the functionality for carrying out the capacitor ignition is implemented programmatically in the form of operating software (firmware), so that the method - if necessary in interaction with a Device user - is carried out automatically when the operating software is executed in the microcontroller. Within the scope of the invention, the controller can alternatively also be formed by a non-programmable electronic component, such as an application-specific integrated circuit (ASIC) or by an FPGA (Field Programmable Gate Array), in which the functionality for carrying out the capacitor ignition is implemented using circuit technology.

In a conceivable development, a diode connected in series with the ignition capacitor and a second semiconductor switch connected in parallel to the ignition capacitor are connected between the rectifier and the ignition transformer. The diode is connected in series in the forward direction between the rectifier and the ignition capacitor, with the second semiconductor switch being connected between the rectifier and the diode on the one hand and the ground potential on the other hand, and is connected to the controller on the control side. The second semiconductor switch is, for example, also designed as a power switch, in particular as a normally conducting n-channel IGBT, with the collector connection between the rectifier and the diode and the emitter connection being connected to the ground potential and the gate connection being connected to the controller.

In this arrangement, the second semiconductor switch and the inductance of the generator act as a step-up converter circuit or as a step-up booster to generate the required voltage for the ignition capacitor of approximately 200 V (volts) to 300 V. Depending on the design of the generator and the speed range, the generator current half-waves are clocked (short-circuited) by the second semiconductor switch, then the second semiconductor switch is opened, whereby the released energy charges the ignition capacitor as described above.

The ignition capacitor is thus charged in several switching cycles of the second semiconductor switch, so several “energy portions” are required to charge the ignition capacitor. Especially at low speeds, when little voltage and current is induced in the generator, it is necessary to clock more (more switching cycles) compared to higher speeds.

The stored energy is defined by the inductance of the generator and the amount of current that flows through the inductance. The inductance depends on the design.

In a preferred embodiment, the controller driving the first and/or second semiconductor switch is synchronized via a coupling circuit to the speeds of the generator and the zero crossings of the generator current. In other words, synchronization occurs the timing of the generator's half-waves. It is, for example, advantageous to switch the second semiconductor switch on and off several times during a (current) half-wave, so that several, smaller “energy portions” are generated during a half-wave in order to charge the ignition capacitor. With higher generator speeds, the output power of the generator increases continuously, whereby it becomes increasingly important to dose the “energy portions” more finely in order to prevent the ignition capacitor from being overcharged. This is particularly true if the ignition capacitor is already precharged, for example if it already has half the nominal voltage.

In particular, the synchronization is implemented in such a way that the controller closes or switches on the second semiconductor switch when the generator current crosses zero. This reduces the switch-on losses of the second semiconductor switch and EMC radiation (EMC: Electromagnetic Compatibility), since at this point the generator current is equal to or almost zero. Furthermore, the synchronization is preferably implemented in such a way that the controller opens or switches off the second semiconductor switch at a maximum of the generator current. If the second semiconductor switch is turned off exactly at the maximum or at the peak value of the generator current, the stored energy of the generator coils is maximized, which subsequently improves the immediate charging of the ignition capacitor, and thus the multiple spark functionality.

In a conceivable further development, a voltage divider is connected in parallel to the ignition capacitor, with a voltage tap of the voltage divider being routed to the controller. This means that the controller is set up to monitor the charging voltage of the ignition capacitor. The controller can therefore, for example, use corresponding stored tables to calculate or derive the activation time of the second semiconductor switch, which is required to charge the ignition capacitor to the nominal voltage. This ensures reliable charging of the ignition capacitor and thus reliable generation of the ignition spark.

In an expedient embodiment, the controller operates the first and second semiconductor switches in parallel. As explained above, the generation of ignition sparks or multiple ignition sparks in the ignition device according to the invention takes place solely by activating the first semiconductor switch. The first semiconductor switch then takes over the ignition current and the generator current, which, however, can lead to a thermal overload, so that the first semiconductor switch is dimensioned correspondingly large. In order to avoid this disadvantage, the first and second semiconductor switches are preferably activated simultaneously. Then the second semiconductor switch takes over the short-circuit current of the generator and the first semiconductor switch takes over the current of the ignition circuit. This makes it possible to realize a particularly cost-effective and compact ignition device.

The internal combustion engine according to the invention has an internal combustion engine and an ignition device described above, which is coupled to the internal combustion engine. The internal combustion engine is preferably a hand-held or hand-carried internal combustion engine, such as a chainsaw, a leaf vacuum (leaf blower) or a lawn mower. The internal combustion engine is preferably a small engine, for example a two-stroke engine. Through the ignition device according to the invention, the internal combustion engine is advantageously provided for multiple ignition spark generation and is suitable and set up for this purpose.

In a preferred application, the ignition device described above is used according to the invention as a multiple ignition spark system of an internal combustion engine or an internal combustion engine.

• 1 ein Blockschaltbild einer Zündvorrichtung gemäß dem Stand der Technik,
• 2 ein Blockschaltbild einer erfindungsgemäßen Zündvorrichtung in einer ersten Ausführungsform,
• 3 in Draufsicht einen Generator der Zündvorrichtung,
• 4 ein Blockschaltbild einer erfindungsgemäßen Zündvorrichtung in einer zweiten Ausführungsform,
• 5 ein erstes Diagramm zur Ansteuerung der Zündvorrichtung, und
• 6 ein zweites Diagramm zur Ansteuerung der Zündvorrichtung.

Exemplary embodiments of the invention are explained in more detail below with reference to a drawing. Show in it:

• 1 a block diagram of an ignition device according to the prior art,
• 2 a block diagram of an ignition device according to the invention in a first embodiment,
• 3 a top view of a generator of the ignition device,
• 4 a block diagram of an ignition device according to the invention in a second embodiment,
• 5 a first diagram for controlling the ignition device, and
• 6 a second diagram for controlling the ignition device.

Corresponding parts and sizes are always provided with the same reference numbers in all figures.

In the block diagram of the 2 an ignition device (capacitor ignition device) 2 according to the invention is shown with a generator 4 and with an ignition module 6 and with a spark plug 8. The ignition device 8 is an example wise part of an internal combustion engine and is coupled to an internal combustion engine, with the spark plug 8 being arranged in a combustion chamber of the internal combustion engine.

The in 3 Generator 4 shown individually has a magnet wheel 10 as an (outer rotor) rotor. The magnet wheel 10 can be a magnet wheel with a grip heating generator. The magnet wheel 10 has a number of unspecified pole pockets into which magnets, for example neodymium magnets, are glued. The magnets are polarized alternately (NSNS, see 3 ). A stator 12 of the generator 4 is firmly connected to a crankcase of the internal combustion engine and contains a stator core 14 (stator core, stator body), which is assembled or packaged in layers, for example from stamped transformer sheets. The stator core 14 has a number of stator teeth directed radially outwards, onto which induction coils 16 (stator coils) are applied. The induction coils 16 are connected to one another in series, the number of induction coils 16 corresponding to the number of magnets. The induction coils 16 are provided with reference numbers in the figures merely as examples.

The magnet wheel 10 rotates synchronously with the internal combustion engine of the internal combustion engine. When rotating, the magnet wheel 10 induces a voltage or a current in the induction coils 16 and possibly in a further coil winding or trigger coil 18 as well as in an ignition transformer U5 of the ignition module 6.

The ignition transformer U5 has a primary coil (primary winding) Lp and a secondary coil (secondary winding) Ls. The primary winding Lp and the secondary winding Ls have, for example, the same number of turns. The positive and negative half-waves of the induced generator voltage (generator current) are converted into a rectified charging current I via a rectifier (rectifier module) G1. The charging current only has positive current half-waves. The charging current is led to an energy storage device, also referred to below as an ignition capacitor U4. The rectified charging current charges the ignition capacitor U4, which is connected to a ground potential (ground) GND.

By means of the charging current or the charging voltage, a power supply U10 for a controller U8 is supplied with energy. The power supply U10 generates a supply voltage VDD based on the charging voltage and provides the supply voltage VDD for the controller U8. The controller U8 is designed, for example, in the form of a microprocessor or microcontroller.

The ignition device 2 also has a coupling circuit U7. The coupling circuit U7 is supplied with the charging voltage and the voltage generated by the trigger coil 20, with two analog output signals A1, A2 being generated, which are supplied to an analog-digital converter ADC of the controller U8.

The ignition capacitor U4 is connected on the one hand to the ground potential GND and on the other hand to the rectifier G1 and the primary coil Lp of the ignition transformer U5. A base point of the primary coil Lp is connected to the ground potential GND via an electronic semiconductor switch (ignition switch) U9. The ignition capacitor U4 is therefore connected in parallel to the primary coil Lp.

The semiconductor switch U9 is designed as a power switch, in particular as an ignition IGBT, for example as a normally conducting n-channel IGBT. The semiconductor switch U9 is connected on the collector side (C) to the base of the primary coil Lp and on the emitter side (E) to the ground potential GND. The gate connection (G) of the semiconductor switch U9 is connected to a control output of the controller U8.

During an ignition process, i.e. when an ignition spark 20 is generated by means of the spark plug 8, the semiconductor switch U9 is actuated, i.e. switched on. As a result, the ignition capacitor U4 is discharged via the primary winding Lp of the ignition transformer U5 and a high-voltage pulse is subsequently generated by the secondary winding Ls of the ignition transformer U5, which in turn causes a spark flashover on the spark plug 8 as an ignition spark 20.

Furthermore, the generator windings or induction coils 16 are also short-circuited by actuating the semiconductor switch U9. The corresponding short-circuit current therefore flows through the generator 4. If the semiconductor switch U9 is switched off after the ignition spark has been generated, the current through this circuit suddenly becomes zero. The inductance of the generator 4, i.e. the induction coils 16, now behaves like a step-up converter/step-up converter. This charges the inductance of the generator 4 energetically. This stored amount of energy is released when the semiconductor switch U9 is switched off in the form of a generator current that continues to flow, so that this energy in turn charges the ignition capacitor U4 again within a short time. As a result, the ignition device 2 or the ignition module 6 is designed as a multiple ignition spark system.

The 4 shows a second exemplary embodiment of the ignition device 2. In this embodiment, the ignition module 6 has an additional semiconductor switch S1 and a diode 22 as well as a voltage divider T1. The diode 22 is connected in the forward direction between the rectifier G1 and the ignition capacitor U4. The semiconductor switch S1 is designed, for example, as a normally conducting n-channel IGBT. The collector connection (C) of the semiconductor switch S1 is connected to the anode side of the diode 22, with the emitter connection (E) being connected to the ground potential GND. The gate connection (G) of the semiconductor switch S1 is connected to a second control output of the controller U8. The voltage divider T1 is connected in parallel to the ignition capacitor U4 on the cathode side of the diode 22, with a voltage tap of the voltage divider T1 being led to the controller U8.

In this arrangement, the semiconductor switch S1 and the induction coils 16 of the generator 4 act as a step-up converter or step-up booster, which generates a (charging) voltage for the ignition capacitor U4 of approximately 200 V to 300 V. Depending on the design of the generator 4 and the speed range, the generator current half-waves are clocked (short-circuited) by the semiconductor switch S1. The semiconductor switch S1 is then opened, whereby the energy released charges the ignition capacitor U4 as described above.

In this version, the ignition capacitor U4 is charged in particular in several switching cycles, meaning that several “energy portions” are generated in order to charge the ignition capacitor U4.

The 5 shows a corresponding control of the semiconductor switches U9 and S1. The diagram of the 5 comprises three horizontal sections 24, 26, 28 arranged one above the other. Horizontally, that is to say on the X or abscissa axis, a rotation angle φ is plotted in degrees (°), which corresponds to the position or rotational position of the magnet wheel 16.

The section 24 shows the rectified generator or charging current I along the vertical ordinate axis (Y-axis), with a maximum current value Ipeak being displayed horizontally with dashed lines. Four consecutive half-waves of the charging current I are shown in section 24.

Section 26 shows the (gate) control of the semiconductor switch S1, with section 38 showing the corresponding (gate) control of the semiconductor switch U9. The controls are carried out in particular by pulse width modulated pulse signals from the controller U8.

The controller U8 or the controls of the controller U8 are synchronized to the speeds and the zero crossings of the generator 10 by means of the coupling circuit U7.

In order to reduce the switch-on losses of the semiconductor switch S1 and the EMC radiation as much as possible, the semiconductor switch S1 is preferably switched on at the current zero crossings of the generator 4 or the charging current I (vertical lines 30 in 5 ). In order to maximize the stored energy of the induction coils 16, it is advantageous to turn off the semiconductor switch S1 exactly at the maximum current value Ipeak of the charging current I (vertical lines 32 in 5 ).

However, it can also be advantageous to switch the semiconductor switch S1 on and off several times during a half-wave, so that several smaller “energy portions” are generated during a half-wave in order to charge the ignition capacitor U4. This is an example of the second half wave in 5 shown.

With higher generator speeds (rotations), the output power of the generator 4 increases continuously, so that it becomes increasingly important to dose the “energy portions” more finely in order to prevent the ignition capacitor U4 from being overcharged. This is particularly true if the ignition capacitor U4 is already precharged, for example if it already has half the nominal voltage. This process is exemplified in 5 shown during the third half-wave, so that the activation time of the semiconductor switch S1 is shortened according to the requirements in such a way that the semiconductor switch S1 is no longer switched off at the maximum current value Ipeak, but rather earlier. The voltage of the ignition capacitor U4 is monitored by the controller U8 via the voltage divider T1. The controller U8 can, for example, use corresponding stored tables to calculate or determine the control time for the pulse duration of the control pulses, which is required to charge the ignition capacitor U4 to the nominal voltage.

For the fourth half wave in 5 The first ignition pulse for the semiconductor switch U9 is shown. It can also be advantageous to control the semiconductor switch S1 and the semiconductor switch U9 independently of one another. For example, if the first spark is to be emitted at the beginning of a half-wave, i.e. the generator current is still very low and therefore needs to be charged a little longer in order to obtain a sufficient amount of energy. Then the semiconductor switch S1 can be controlled independently of the semiconductor switch U9 for a correspondingly longer period until the generator current (short-circuit current) reaches a certain value and charges the ignition capacitor to a correspondingly high level (for example more than 50% of the nominal voltage).

In a conceivable embodiment, the generator system is designed for maximum energization at the ignition point (ZZP). The ability to ignite multiple times (multiple sparks) depends on how high the generator current is at the time of ignition. If the generator current is currently in the zero crossing, i.e. is very low in magnitude, the generator inductance is not or only slightly charged with current, which limits the ability to fire multiple times. It may therefore be necessary to take the alignment of the generator system into account when dimensioning or orienting the stator rotor to the crankshaft. In the 6 An almost optimal, constructive alignment is shown here.

The 6 shows a control diagram according to the 5 for optimized structural alignment. The three vertical sections are analogous to the 5 labeled 24, 26 and 28.

In the example of the 6 a generator 4 with twelve induction coils 16 and twelve individual magnets is used ( 3 ). This means that each half shaft has a 30° crank angle. As a rule, small engines are ignited in the idle range of the machine (i.e. approx. 1000-4000rpm) at 10° BTDC (before top dead center) and in the working area at approx. 30° BTDC. This can vary slightly from engine to engine depending on the application.

In the 6 It can be seen that the ignition times of both important working areas of the internal combustion engine, i.e. idling and working area, occur exactly when the generator current is as close as possible to its peak level (top value) Ipeak, i.e. there is sufficient generator current available at the time of ignition to power the generator system 4 to be charged energetically in order to use this energy to charge the ignition capacitor U4 to a correspondingly high level after the ignition spark (preferably more than approx. 50% of the nominal voltage).

The claimed invention is not limited to the exemplary embodiments described above. Rather, other variants of the invention can also be derived by the person skilled in the art within the scope of the disclosed claims without departing from the subject matter of the claimed invention. In particular, all of the individual features described in connection with the various exemplary embodiments can also be combined in other ways within the scope of the disclosed claims without departing from the subject matter of the claimed invention.

Reference symbol list

2, 2'

Ignition device

4, 4'

generator

6

Ignition module

6'

Ignition spark

8th

spark plug

10

Polrad

12

stator

14

Stator core

16

induction coil

18

Trigger coil

20

Ignition spark

22

diode

24, 26, 28

Section

30, 32

line

P'

Polrad

M'

magnet

N', S'

Pole shoe

K'

Iron core

Ka', Kb'

leg

U5, U5'

Ignition transformer

U2'

Trigger coil

U1'

charging coil

LSp', LSn'

current half wave

U4, U4'

ignition capacitor

G1, G1'

rectifier

FU'

spark plug

Lp, Lp'

Primary coil

Ls, Ls'

Secondary coil

U10, U10'

Power supply

U8, U8'

Controllers

VDD, VDD'

Supply voltage

U9'

Thyristor/circuit breaker

U9

Semiconductor switch

I, I'

charging current

GND, GND'

Ground/ground potential

U7

Coupling circuit

A1, A2

Output signal

ADC

Analog-to-digital converter

Ipeak

Current value

T1

Voltage divider

Claims (10)

Ignition device (2) for an internal combustion engine, comprising - a generator (4), which generates an oscillating generator current in generator operation, - a rectifier (G1) for converting the generator current into a rectified charging current (I), - an ignition capacitor (U4) for storing energy for an ignition spark (20), the ignition capacitor (U4) being chargeable by means of the charging current (I), and - an ignition transformer (U5) with a primary coil (Lp) and with a secondary coil (Ls), the secondary coil (Ls) being connected to a spark plug (8) which generates the ignition spark (20), - whereby the ignition capacitor (U4) is connected in parallel to the primary coil (Lp), - wherein a first semiconductor switch (U9) is connected between a base of the primary coil (Lp) and a ground potential (GND), and - The spark plug (U8) generates the ignition spark (20) by capacitor ignition, in which the first semiconductor switch (U9) is closed, so that the charged ignition capacitor (U4) discharges via the ignition transformer (U5). Ignition device (2). Claim 1 , characterized in that the first semiconductor switch (U9) is designed as a power switch. Ignition device (2). Claim 1 or 2 , characterized in that the first semiconductor switch (U9) is designed as an ignition IGBT, which is connected on the collector side to the base of the primary coil (Lp) and on the emitter side to the ground potential (GND). Ignition device (2) according to one of the Claims 1 until 3 , characterized in that a diode (22) connected in series with the ignition capacitor (U4) and a second semiconductor switch (S1) connected in parallel to the ignition capacitor (U4) are connected between the rectifier (G1) and the ignition transformer (U5). Ignition device (2). Claim 4 , characterized in that a controller (U8) controlling the first and/or second semiconductor switch (U9, S1) is synchronized via a coupling circuit (U7) to the speeds of the generator (4) and the zero crossings of the generator current. Ignition device (2). Claim 5 , characterized in that - the controller (U8) closes the second semiconductor switch (S1) at a zero crossing of the generator current, and - that the controller (U8) opens the second semiconductor switch (U9) at a maximum of the generator current. Ignition device (2). Claim 5 or 6 , characterized in that the controller (U8) monitors the charging voltage of the ignition capacitor (U4) by means of a voltage divider (T1) connected in parallel to the ignition capacitor (U4). Ignition device (2) according to one of the Claims 5 until 7 , characterized in that the controller (U8) operates the first semiconductor switch (U9) and the second semiconductor switch (S1) in parallel. Internal combustion engine having an internal combustion engine and an ignition device (2) coupled thereto according to one of Claims 1 until 8th . Use of an ignition device (2) according to one of the Claims 1 until 8th as a multiple spark system.

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