EP3069009A1

EP3069009A1 - Ignition system and method for operating an ignition system

Info

Publication number: EP3069009A1
Application number: EP14786493.8A
Authority: EP
Inventors: Tim Skowronek; Thomas Pawlak; Wolfgang Sinz
Original assignee: Robert Bosch GmbH
Current assignee: Robert Bosch GmbH
Priority date: 2013-11-14
Filing date: 2014-10-16
Publication date: 2016-09-21
Also published as: WO2015071047A1; DE102014216040A1; US20160281673A1; CN105705776A

Abstract

Disclosed is a method for operating an ignition system (1) for an internal combustion engine, said ignition system comprising a primary voltage generator (2) and a step-up converter (7) for maintaining an ignition spark generated by the primary voltage generator (2). According to the invention, once it has been determined (100) that a change in energy is required in order for an ignition spark to be maintained by the step-up converter (7), a switch-on time of the step-up converter (7) in relation to a switch-off time of the primary voltage generator (2) is modified (300).

Description

description

title

Zündsvstem and method for operating a Zündsvstems prior art

The present invention relates to a method for operating a

Ignition system for an internal combustion engine, comprising a first

Voltage generator (also called "primary voltage generator") and a

Up converter. In particular, the present invention relates to avoiding unwanted sparking during operation.

Ignition systems are used in the prior art to ignite an ignitable mixture in a combustion chamber of a spark-ignition internal combustion engine. For this purpose, a spark gap with electrical energy or electrical voltage is applied, in response to what the forming spark ignited the combustible mixture in the combustion chamber. The

The main requirements of modern ignition systems result indirectly from necessary emission and fuel reductions. From appropriate engineered approaches, such as supercharging and lean / shift operation

(spray-guided direct injection) in combination with increased

Exhaust gas recirculation (EGR) rates are derived from requirements for the ignition systems. The representation of increased ignition voltage and energy requirements at elevated temperature requirements are necessary. In conventional inductive ignition systems, the total energy required for ignition must be in the

Ignition coil are cached. The high requirements regarding the spark energy results in a large design of the ignition coil. This is consistent with the requirements for small space today

Engine designs ("downsizing") in conflict In an earlier application by the Applicant, two major functions of the ignition system have been implemented

adopted different modules. A high voltage generator generates the voltage required for the high voltage breakdown at the spark plug High voltage. A bypass, eg in the form of a boost converter, provides energy to maintain the spark for continued mixture ignition. In this way, high spark energies can be optimized

Funkenstromverlauf be provided despite a reduced design of the ignition system.

Although high spark currents are more robust compared to turbulent flow in the combustion chamber, but known to cause strong erosion of the

Spark plug electrodes. In contrast, small spark currents can lead to a spark break in turbulent flow in the combustion chamber, if the

Spark energy or the spark current falls below a defined limit. The previously known systems do not exploit the potential for spark stabilization in ignition systems satisfactorily. Disclosure of the invention

The aforementioned need is satisfied according to the invention by a method for operating an ignition system. The method is characterized by a need-based provision of spark energy, so that the

Spark current can be set to a desired value. To this

In this way, a compromise between electrode erosion and spark break tendency can be suitably realized. The inventive method for operating an ignition system is particularly suitable for a gasoline-fueled internal combustion engine, with particular advantages in spray-guided direct injection and turbocharged high-load EGR

Engines can be achieved. The ignition system with which the method according to the invention is carried out comprises a primary voltage generator and a boost converter, wherein the boost converter is set up to maintain a spark generated by means of the primary voltage generator. About the boost converter on-board power can be brought to a suitable voltage level and the spark gap supplied. The method according to the invention is characterized by determining a changed energy requirement for a spark to be kept upright by means of the boost converter. In other words, depending on a current operating state, the energy requirement for the spark can vary and such a variation can be determined according to the invention. In response, the

Switch-on time of the boost converter, ie the time at which the Up converter is turned on, changed to meter the spark energy or Zündfunkenstrom- and voltage as needed. In this way, the spark plug wear is reduced by avoiding high spark currents. A particularly strong electrode wear on commercially available spark plugs arises, for example, with spark currents greater than 100 mA.

On the other hand, a spark break is avoided by an increase in the output of the boost converter by the turn-on of the boost converter is preferred and the transient of the boost converter in the direction "earlier", in particular before the ignition is moved below a lower spark current threshold If the voltage increases after switching on over several operating cycles of the boost converter, the boost converter can thus provide a higher electrical energy when the mixture ignites, and the reduction of heat loss in the boost converter by a demand-based selection of its switch-on time is an advantage

present invention. The load on the electrical components (e.g., a high voltage capacitor for caching electrical energy) is reduced. Therefore, the electrical components can be chosen cheaper in the design of the ignition system according to the invention. Also in the electrical (control) circuit of the boost converter is in the

Adapting the operation of the boost converter to a changed

Energy requirement generates less heat loss. Overall, the present invention allows a lower energy consumption and the reliable ignition of the mixture in demanding combustion of the

Ignition system from the electrical system (such as a motor vehicle (KFZ) or a

Car), which smaller cable cross-sections dimensioned and consumption advantages can be achieved. In addition, lower currents mean within the

Ignition system, a reduction in electromagnetic emissions. In other words, the electromagnetic compatibility (EMC) is improved.

The dependent claims show preferred developments of the invention.

Determining the changed energy requirement preferably comprises measuring a spark current or a spark voltage. This can be done for example by a shunt, over which a current through the

Spark gap of the ignition system is determined. The voltage detection can, for example, by means of an electrical circuit, an analog Circuit or a microcontroller, or carried out by an ASIC within the ignition system. In this way, a low or no additional hardware effort for implementing the method according to the invention is required.

More preferably, determining the changed energy requirement comprises comparing a measured electrical characteristic of a spark or a signal received from an electronic controller with an associated reference. The reference can for example be taken from a storage means. This marks, for example, thresholds when

Exceeding which the spark energy should be lowered to avoid erosion and below which the spark energy should be increased to avoid an unwanted spark break. For example, threshold values in the form of spark currents and / or ignition spark voltages can be stored as electrical parameters and compared with determined parameters. As the electronic control unit, for example, an engine control unit or an ignition control device can be used, the transmitter determines signals for the control of the operation of the internal combustion engine and provides. The comparison of measured values or control signals with individual references or threshold values represents a simple mathematical operation which is cost-effective and space-saving to implement in terms of circuitry.

More preferably, the method comprises the step of classifying the electrical characteristic by providing a measurement of the electrical characteristic to a predefined characteristic interval, e.g. is assigned within a storage means of the ignition system. In addition, the switch-on can be specified by the control unit by the requirements of

Combustion considered. For example, you can

Engine operating conditions are determined and taken into account. An example of such is an exhaust gas recirculation in part-load operation, which leads to a relatively homogeneous mixture state within the combustion chamber. In such a case, it is not necessary that the boost converter before the

Off time of the primary voltage generator (ignition) is. In an operating point with exhaust gas recirculation in high load operation is a

Overlap between the operation of the boost converter and the

Off time (ignition timing) of the primary voltage generator recommended. In an operating state in which the catalyst is to be heated, in turn, an overlap between the operation of the boost converter and the switch-off (ignition) of the

Primary voltage generator is not required. In a shift operation, in turn, there is an inhomogeneous mixture composition within the

Combustion chamber in which an overlap between the operation of the boost converter and the switch-off of the primary voltage generator is advantageous. In this case, the ignition system can be set up, respectively

Characteristic classes allocate suitable switch-on times for the step-up converter. The switch-on times, for example, within a

Be assigned to the storage means of the ignition system of the respective characteristic class and in response to a classification in a determination of the

Switching time of the boost converter can be applied. This operation is also a little expensive and circuit-wise easy and quickly feasible way to implement the present

Invention.

Further preferably, the determination of the parameter takes place within an FPGA and / or an ASIC of the ignition system. The aforementioned electronic components are e.g. within the ignition system, in particular in the region of each spark plug for controlling the ignition arranged, wherein the contact with the spark plug, the control of the ignition and

Ignition process can take place. Therefore, an implementation of the present invention is possible in this way without additional hardware.

More preferably, the change of the switch-on takes place in response to a reduced power requirement of the ignition system for a successful ignition. If the on-time of the boost converter is delayed from the time of turning off the primary voltage generator (eg, coincident with the time of turning off the primary voltage generator), the output current and / or the output voltage and / or the output power of the boost converter is reduced at the turn-off time of the primary voltage generator leads to a reduction of the corresponding electrical variable at the spark gap. In the reverse

Case leads in response to an increased demand for energy over the time of switching off the primary voltage generator is preferred Switching the boost converter to an increase of the output current and / or the output voltage and / or the output power of

Up converter. In this way, both spark erosion and tearing of the spark can be effectively avoided or reduced.

It is very advantageous if the switch-on depends on the

Operating state and / or changed depending on the determined energy consumption. According to one embodiment, the switch-on time is predetermined in a first ignition process as a function of the operating state and determined for the subsequent ignition processes as a function of the determined energy requirement.

In this way, sparks energy is provided as needed.

It is also advantageous if the determination of the changed energy requirement in a first step, the determination of an electrical characteristic and / or a change in this characteristic and / or a rate of change of these

Characteristic includes, wherein the electrical characteristic in particular a current of the spark and / or a voltage of the spark

can be characterizing stress. In a second step, it is checked whether an exceeding condition and / or an underflow condition is satisfied by determining whether a comparison quantity is a predetermined upper one

Threshold exceeds and / or falls below a predetermined lower threshold. The comparison variable is, for example, the determined parameter or the change of this determined characteristic or the

Rate of change of this determined parameter. The changing of the switch-on time takes place by shifting the switch-on time to a later point in time relative to the switch-off time of the primary voltage generator, if the exceeding condition is satisfied, or by switching the switch-on time to a relative to the switch-off time of the

Primary voltage generator earlier time is shifted when the underrun condition is met. In this way, the spark current is regulated to a value so that neither sparking threatens nor a strong erosion of the spark plug electrode occurs.

The ignition system designed for an internal combustion engine, by means of which the method according to the invention is carried out, has a step-up converter for maintaining a spark generated by means of a primary voltage generator. The ignition system is characterized by means for determining a change in energy demand for an upright to be maintained by means of the boost converter spark. In other words, the means may determine an operating state change of the ignition system or the internal combustion engine, in response to which the spark plug is to be supplied with a changed electrical energy or a changed electrical power, on the one hand a spark break and on the other hand excessive wear of the ignition system avoid. In addition, the manipulated variable can be specified via the control unit as a function of the combustion process. In addition, the ignition system according to the invention comprises means for changing a switch-on time of the boost converter in response to a determined energy demand change. These means are set up, according to the changed energy requirement, the switch-on time of the boost converter, for example, with respect to the crank angle of the internal combustion engine of a speed-dependent variable or the switch-off time of the engine

Primary voltage generator to adjust the spark gap a modified

Supply power. The features, combinations of features and the resulting advantages correspond substantially to those carried out in connection with the first-mentioned aspect of the invention, so that reference is made to the above statements to avoid repetition.

For example, the ignition system comprises a shunt, by means of which it is set up to carry out a spark current measurement in order to determine a changed energy requirement. Alternatively, via a

Voltage measurement a conclusion on the height of the spark current done. By the operation of the boost converter, a defined power is delivered.

Thus, current and voltage are in a fixed relationship to each other. The voltage measurement over the shunt can take place, for example, via an FPGA and / or an ASIC of the ignition system. In addition, also determined without the use of a shunt spark voltage through the

the aforementioned integrated circuits for determining an amended

Energy requirements of the spark gap can be used. As electrical characteristic to be determined, currents, voltages and / or powers are also suitable here. Since current ignition systems sometimes include an ASIC on each combustion chamber or on each spark plug, the implementation of the ignition system can be carried out with minimal or no additional hardware.

Effort to be realized. The ignition system additionally has, for example, storage means by means of which it is set up to classify the current energy requirement. In other words, the measured in the current operating state

Energy requirements are compared with energy demand classes within the storage means. The storage means can also hold predefined switch-on times for the boost converter, which have proven to be suitable for the respective energy demand classes. In this way, a simple and circuitry cost-effective implementation of the ignition system is possible.

Brief description of the drawings

Hereinafter, embodiments of the invention will be described in detail with reference to the accompanying drawings. In the drawings:

Figure 1 is a circuit diagram of an embodiment of an ignition system in which the inventive method can be used;

Figure 2 timing diagrams to electrical characteristics as in the

Operation of the ignition system shown in Figure 1 can occur;

Figures 3a, 3b are timing diagrams of electrical characteristics as in the

inventive operation of the ignition system shown in Figure 1 can occur; and

Figure 4 is a flow chart illustrating steps of a

Embodiment of the method according to the invention.

Embodiments of the invention

FIG. 1 shows a circuit of an ignition system 1, which has a

Step-up transformer 2 comprises as a high voltage generator whose

Primary side 3 can be supplied from an electrical energy source 5 via a first switch 30 with electrical energy. The step-up transformer 2 consisting of a primary coil 8 and a secondary coil 9 may also be referred to as the first voltage generator or primary voltage generator. At the entrance of the circuit, in other words at the connection to the electrical energy source 5, a fuse 26 is provided. to

Stabilization of the input voltage, moreover, a capacitance 17 is provided parallel to the input of the circuit or parallel to the electrical energy source 5. The secondary side 4 of the step-up transformer 2 is powered by an inductive coupling of the primary coil 8 and the secondary coil 9 with electrical energy and has a known from the prior art diode 23 for Einschaltfunkenunterdrückung, which diode may alternatively be replaced by the diode 21. In a mesh with the secondary coil 9 and the diode 23, a spark gap 6 is provided against an electrical ground 14, via which the ignition current i ₂ should ignite the combustible gas mixture. A boost converter 7 is provided between the electric power source 5 and the secondary side 4 of the step-up transformer 2. The boost converter 7 comprises an inductor 1 5, a switch 27, a capacitor 10 and a diode 16. In the boost converter 7, the inductance 1 5 in the form of a

Transformer provided with a primary side 15 1 and a secondary side 1 5_2. The inductor 1 5 serves as an energy storage to a

Maintain current flow. Two first terminals of the primary side 1 5 1 and the secondary side 1 5_2 of the transformer are respectively connected to the electric power source 5 and the fuse 26. There is a second

Connection of the primary side 15 1 via the switch 27 with the electrical ground

14 connected. A second connection of the secondary side 15_2 of

Transformer is connected without switch directly to the diode 1 6, which in turn is connected via a node to a terminal of a capacitor 10. This connection of the capacity 1 0 is for example via a

Shunt 1 9 with the secondary coil 9 and another terminal of the capacitor 10 is connected to the electrical ground 14. The output power of the

Step-up converter is fed via the node on the diode 16 in the ignition system and the spark gap 6 is provided.

The diode 1 6 is oriented in the direction of the capacitance 10 conductive. Due to the transmission ratio, a switching operation by the switch 27 in the branch of the primary side 1 5_1 also acts on the secondary side 1 5_2. However, since current and voltage according to the gear ratio on one side are higher or lower than on the other side of the transformer, can be for

Switching operations find cheaper dimensions for the switch 27.

For example, lower switching voltages can be realized, whereby the dimensioning of the switch 27 is easier and less expensive possible. The switch 27 is controlled via a drive 24, which is connected via a driver 25 to the switch 27. Between the capacitor 10 and the secondary coil 9 is a shunt 19 as current measuring means or

Voltage measuring means provided, the measuring signal is supplied to the switch 27. In this way, the switch 27 is configured to respond to a defined range of the current i ₂ through the secondary coil 9. To protect the capacitor 10, a Zener diode 21 is connected in the reverse direction parallel to the capacitor 10. Moreover, the control 24 receives a control signal S _H ss- About this, the supply of energy via the boost converter 7 in the secondary side and are turned off. In this case, the power of the electrical variable introduced by the step-up converter or into the spark gap, for example via the frequency and / or the pulse-pause ratio, can also be controlled via a suitable control signal S _H ss. In addition, according to the invention, a switch-on time can be shifted via the control signal S _H ss when the energy requirement of the spark gap changes. Furthermore, a switching signal 32 is indicated, by means of which the switch 27 can be controlled via the driver 25. When the switch 27 is closed, the inductance 15 is supplied via the electrical energy source 5 with a current which flows directly into the electrical ground 14 when the switch 27 is closed. With open switch 27, the current is conducted through the inductance 15 via the diode 16 to the capacitor 10. The voltage in response to the current in the capacitor 10 adjusting voltage adds to the voltage across the secondary coil 9 of the step-up transformer 2 voltage, whereby the arc is supported at the spark gap 6. In this case, however, the capacitor 10 discharges, so that energy 27 can be brought into the magnetic field of the inductor 15 by closing the switch 27 to recharge this energy to the capacitor 10 at a reopening of the switch 27. Recognizable is the control 31 of the primary side in the third

provided switch 30 is kept significantly shorter than this by the

Switching signal 32 for the switch 27 is the case. Optionally, a non-linear two-pole, by a high voltage diode 33 shown in dashed lines

symbolizes the secondary-side coil 9 of the boost converter 7 are connected in parallel. This high voltage diode 33 bridges the

High voltage generator 2 on the secondary side, causing by the

Upverter 7 supplied energy is passed directly to the spark gap 6, without being guided by the secondary coil 9 of the high voltage generator 2 become. Thus, no losses on the secondary coil 9 and the efficiency increases. A determination according to the invention of a changed energy requirement for the spark is possible through an information technology connection of the engine control unit (MSG) 40, which receives a first signal S ₄₀ for setting an operating point of an internal combustion engine and outputs a corresponding second signal S ₄₀ 'to an ASIC 42. The ASIC 42 is further connected to a memory 41, from which references in the form of limits for classes of energy for the current or future required electrical energy to maintain the spark can be read. The ASIC 42 is to influence the

Switch-on of the boost converter 7 arranged to provide the driver 24 with a modified according to need or time-shifted control signal S _H ss, the switch provided in response to which the driver 25 with a modified 27 or time-shifted switching signal 32nd

For example, the boost converter 7 may be turned on sooner or later in response to receiving the changed switching signal 32, so that the voltage across the diode 10 at the turn-off time of the

Switch 30 is lower or higher. FIG. 2 shows timing diagrams for a) the ignition coil current i _zs , b) the associated one

Boost converter current i _H ss, c) the output voltage across the

Spark gap 6, d) the secondary coil current \ ₂ for the ignition system shown in Figure 1 without (501) and with (502) using the boost converter 7, e) the switching signal 31 of the switch 30 and f) the switching signal 32 of the switch 27. In detail : Diagram a) shows a short and steep rise in the

Primary coil current i _Z s, which occurs during the time in which the switch 30 is in the on state ("ON", see diagram 3e). With the switch 30 switched off, the primary coil current i _zs drops to 0 A. Diagram b ) also illustrates the current consumption of the boost converter 7, which is achieved by pulsed or clocked driving of the switch 27. In practice, clock rates in the range of several tens of kHz have proven to be suitable for realizing appropriate voltages on the one hand and acceptable efficiencies on the other hand.

By way of example, the integer multiples of 10,000 Hz in the range between 10 and 100 kHz may be mentioned as possible range limits. In order to control the power delivered to the spark gap during an existing spark, a, in particular stepless, control of the Pulse-to-break ratio of the signal 32 to produce a corresponding output signal. Diagram c) shows the course 34 at the

operation according to the invention at the spark gap 6 adjusting voltage. Diagram d) shows the characteristics of the secondary coil current i ₂ . As soon as the primary coil current i _zs results due to an opening of the switch 30 to 0 A and thus discharges the magnetic energy stored in the step-up transformer in the form of an arc over the spark gap 6, it turns

Secondary coil current i ₂ , which rapidly drops to 0 without boost converter (501). In contrast, by a pulse-shaped control (see diagram f, switching signal 32) of the switch 27 is a substantially constant

Secondary coil current i ₂ (502) driven over the spark gap 6, wherein the secondary current i ₂ depends on the burning voltage at the spark gap 6 and is assumed here for the sake of simplicity of a constant burning voltage. Only after interruption of the boost converter 7 by opening the

Switch 27 is now also the secondary coil current i ₂ against 0 A from. Out

Diagram d) it can be seen that the falling edge is delayed by the use of the boost converter 7. The total time period during which the boost converter is used is indicated as t _H ss and the time duration during which power is given to the upstream side of the step-up transformer 2 is t. The starting time of t _H ss opposite t, can be chosen variable. In addition, it is also possible to increase the voltage supplied by the electrical energy source by means of an additional DC-DC converter (not shown) before it is further processed in boost converter 7. It should be noted that concrete interpretations depend on many circuit-inherent and external constraints. It does not present the skilled person with any unreasonable problems suitable for his purpose and the constraints he has to consider

Dimensioning yourself. FIG. 3 a shows highly simplified timing diagrams for illustrating electrical quantities from which the influence of an altered one can be seen

Turning time t _{e of} the boost converter 7 on the energy at the

Spark gap 6 in the form of a secondary-side current \ _{2 can} be seen. The upper partial diagram a) shows the case that the switch-off time t _{a of} the primary voltage generator 2 is identical to the switch-on time t _{e of} the

Hochsetzstellers 7 is. At the switch-off time t _a , the current intensity of the current I ₂ drops sharply and falls below the minimum value I _min , which increases to Ensuring a stable spark is required. In other words, the current I ₂ falls below a threshold which is minimal

Spark current l _min can be described and the voltage at the

Spark gap depends. The voltage at the spark gap 6 depends in particular on the processes within the combustion chamber of

Internal combustion engine. Since the boost converter 7 at the time of his

Turning t _e has not yet reached its maximum efficiency, he catches the falling current I ₂ from late that lingers in this way about 0.75 ms below the limit value l _min. Only about one millisecond after switching off the primary voltage generator 2, the current l _{2 is} stable and extends substantially horizontally until the drive signal 32 switches off the boost converter 7.

Figure 3b shows the influence of an inventively preferred control 32 7. for the boost converter to switch-off time t _a of

Primary voltage generator 2, the boost converter 7 has now reached a significantly increased performance, so that the current l ₂ after the turn-off time t _a increases significantly until it reaches due to declining energy reserves within the primary voltage generator 2, the horizontal level seen in Figure 3a. Due to the increased efficiency of the boost converter 7, the current l ₂ does not fall below the threshold value required for a corresponding minimum power, so that a sufficiently long-lasting

Energy input into the spark gap 6 takes place. Only after switching off the

Ansteuersignais 32 for the boost converter 7, the current l ₂ drops sharply and the spark goes out. Thus, according to the invention by variation of

Switching time t _{e of} the boost converter 7 significant influence on the spark gap 6 made available energy are taken. In this way, an undesirable spark ignition as well as unnecessary spark erosion at the electrodes of the spark gap 6 can be effectively avoided.

FIG. 4 shows a flowchart illustrating steps of a

Embodiment of a method according to the invention. In this case, an altered energy requirement for a spark to be maintained by means of the boost converter is determined in step 100. In the course of this one will

Measurement of an electrical operating variable of the ignition system (in particular the spark gap) performed and the determined value in step 200 with a stored reference compared. An associated operating parameter is read out for the reference, which can be stored, for example, as an operating parameter class assigned to the measured values, and the starting time of the boost converter is changed accordingly in step 300. For example, the switch-on time may be earlier or later than before and with respect to a crankshaft angle of the internal combustion engine or with respect to

Off time of the primary voltage generator can be defined. Due to the changed switch-on time, a high voltage adapted by the step-up converter is supplied to the spark gap, so that tearing off of the spark or unnecessarily high electrode erosion can be avoided.

According to one embodiment, the switch-on time t _{e is changed} in step 300 as a function of the determined operating state and / or depending on the determined energy requirement. In particular, the switch-on time t _e can be predetermined in a first ignition process as a function of the operating state and dependent on the determined ignition processes for the subsequent ignition processes

Energy requirement to be determined.

According to one exemplary embodiment, the determination of the changed energy requirement comprises three steps, wherein in step 100 the determination of an electrical parameter and / or a change of this parameter and / or a rate of change of this characteristic takes place. The electrical parameter may, in particular, be a current of the spark and / or a voltage characterizing a voltage of the spark. In step 200, it is checked whether an overflow condition and / or a

Underride condition is satisfied by determining whether a

Comparison size exceeds a predetermined upper threshold and / or falls below a predetermined lower threshold. The

Exceeding condition is met if the comparison quantity is the

exceeds the predetermined upper threshold. The

Underrun condition is met if the comparison quantity is the

falls below predetermined lower threshold. The comparison variable is, for example, the determined parameter or the change of this determined parameter or the rate of change of this determined parameter. The switching on of the switch-on time t _e in step 300 takes place, for example, by shifting the switch-on time t _e to a later point in time relative to the switch-off time t _{a of} the primary voltage generator 2, if the Exceeding condition is met, or by the on-time t _{e is} shifted to a relative to the turn-off time t _{a of} the primary voltage generator 2 earlier time when the underrun condition is met. In this way, the spark current is regulated to a value so that neither sparking threatens nor a strong erosion of the spark plug electrode occurs. The shifting of the switch-on time t _e according to the invention in step 300 can take place in predefinable stages or continuously.

A computer program may be provided which is set up to carry out all described steps of the method according to the invention. The computer program is stored on a storage medium. As an alternative to the computer program, the method according to the invention can be provided by an electrical circuit provided in the ignition system, an analogous one

Circuit, an ASIC or a microcontroller are controlled, which is configured to perform all the steps described in the inventive method.

Even if the aspects of the invention and advantageous

Embodiments with reference to the attached

Drawings illustrated embodiments have been described in detail, modifications and combinations of features of the illustrated embodiments are possible for the skilled person without departing from the scope of the present invention, the scope of which is defined by the appended claims.

Claims

Method for operating an ignition system (1) for a

Internal combustion engine comprising a primary voltage generator (2) and a boost converter (7) for maintaining a means of the

Primary voltage generator (2) generated spark, characterized by

Determining (100) a changed energy demand for a spark to be maintained by the boost converter (7), and in response thereto

Changing (300) a switch - on time (t _e ) of the

Hochsetzstellers (7) relative to a switch-off (t _a ) of the primary voltage generator (2) or relative to a

Crankshaft angle of an internal combustion engine provided with the ignition system (1).

The method of claim 1, wherein determining (100) the changed energy demand comprises measuring a spark current (i2) and / or a spark voltage and / or one of the spark voltage

corresponding measurement voltage includes.

Method according to one of the preceding claims, wherein determining (100) of the changed energy requirement comprises determining a

Operating state includes, in particular by receiving a signal from an electronic control unit (40), in particular a

Engine control unit.

The method of claim 3, wherein

wherein the changing of the switch-on time comprises a read-out of a switch-on time assigned to the determined operating state, and / or

- wherein changing the turn-on time comprises classifying the operating state and applying a turn-on time associated with the determined class.

The method of claim 1 or 2, wherein determining (100) the changed energy demand comprises comparing (200) a measured electrical characteristic of a spark or a signal (S '40) generated by an electronic controller ( ₄₀ ) with an associated reference ,

6. The method of claim 3, further comprising

Classifying (200) the result of the comparing (200), and

- Changing (300) a switch-on of the boost converter (7) in dependence of a parameter associated with the class.

The method of claim 4, wherein changing (300) the

Turning time in response to a reduced power requirement leads to a switching on of the boost converter (7) at a later time, and / or in response to an increased energy requirement leads to an earlier switching on the boost converter (7).

8. The method of claim 5, wherein

- The determination (100) of a change in energy demand takes place in the course of a first ignition, and

changing (300) the switch-on time in the course of a

second, subsequent ignition occurs.

9. The method according to any one of the preceding claims, wherein the

Switching time (t _e ) is changed depending on the determined operating condition and / or depending on the determined energy demand.

10. The method according to any one of the preceding claims, wherein the

Switch-on (t _e ) is given in a first ignition depending on the operating condition and determined for the subsequent ignition depending on the determined energy demand.

1 1. The method of any one of the preceding claims, wherein determining (100) the changed energy demand comprises the steps of:

- Determining an electrical parameter and / or a change in the characteristic and / or a rate of change of the characteristic, wherein the electrical characteristic in particular a Current of the spark and / or a voltage characterizing the voltage of the spark is

Determine whether an overrun condition and / or

Is satisfied by determining whether a comparison variable exceeds a predetermined upper threshold and / or falls below a predetermined lower threshold, wherein the comparison variable is the determined characteristic or the change of the determined characteristic or the rate of change of the determined characteristic,

12. The method of claim 1 1, wherein changing (300) of the

Switch-on time (t _e ) comprises the following step:

Changing (300) the switch-on time to a time later relative to the switch-off time point (t _a ) of the primary voltage generator (2) when the exceeding condition is satisfied, or

- changing (300) the turn-on time to an earlier time relative to the turn-off time (t _a ) of the primary voltage generator (2) when the underflow condition is met. 13. The method of claim 12, wherein modifying (300) the

Switch-on (t _e ) in predetermined levels or continuously.

14. The method according to any one of the preceding claims, wherein the

Step-up converter (7) by means of a switch (27) is turned on.

A computer program configured to perform all the steps of the method of any of claims 1 to 14.

16. A machine-readable storage medium on which the computer program according to claim 15 is stored.

17. An ignition system configured to carry out all steps of the method according to one of claims 1 to 14.