EP3201463A1

EP3201463A1 - Ignition system and method for checking electrodes of a spark plug in an internal combustion engine

Info

Publication number: EP3201463A1
Application number: EP15753632.7A
Authority: EP
Inventors: Tim Skowronek; Thomas Pawlak; Wolfgang Sinz
Original assignee: Robert Bosch GmbH
Current assignee: Robert Bosch GmbH
Priority date: 2014-09-29
Filing date: 2015-08-03
Publication date: 2017-08-09
Also published as: US20170284358A1; WO2016050388A1; DE102014219722A1; US10156221B2; CN107076099A; BR112017006484A2

Abstract

Disclosed are an ignition system and a method for checking electrodes of a spark gap in an ignition system for a combustion chamber of a spark ignition engine. The method comprises the following steps: generating the spark at the spark gap (6) in an operating state, without igniting a combustible mixture in the combustion chamber; determining a characteristic variable or characteristic function that represents the spark current (i2) and/or the spark voltage (Ubrenn) and/or the spark duration; comparing the characteristic variable or characteristic function with a reference value; adjusting energy for voltage build-up for spark formation and/or for maintaining an ignition spark for mixture ignition, in particular for a future ignition process, depending on the difference between the characteristic variable or the characteristic function and the reference value.

Description

Description title

IGNITION SYSTEM AND METHOD FOR CHECKING ELECTRODE OF A SPARK PLUG OF AN INTERNAL COMBUSTION ENGINE

State of the art

The present invention relates to an ignition system and a method for checking electrodes of a spark gap of an ignition system for a combustion chamber of a spark-ignited internal combustion engine. In particular, the present invention relates to the inspection of the electrodes during operation of the internal combustion engine.

The present invention relates to an ignition system for a

Internal combustion engine. In particular, the present invention relates to an ignition system for internal combustion engines, to which increased

Requirements by (high) charging and diluted, flame retardant mixtures (λ »1, lean-layer concepts, high EGR rates) exist.

GB717676 shows a step-up transformer for an ignition system in which a controlled via a vibration switch circuit part is used in the manner of a boost converter to supply a spark generated by the step-up transformer with electrical energy.

WO 2009/106100 A1 shows a circuit arrangement designed in accordance with a high-voltage capacitor ignition system, in which energy stored in a capacitor is conducted on the one hand to the primary side of a transformer and on the other hand via a bypass with a diode on a spark gap.

US 2004/000878 A1 shows an ignition system in which a secondary-side accumulator comprising a plurality of capacitors is charged in order to supply a spark generated by means of a transformer with electrical energy. WO9304279 A1 shows an ignition system with two energy sources. A

Energy source transmits electrical energy through a transformer to a spark gap, while the second energy source between a

secondary side terminal of the transformer and the electrical ground is arranged.

DE 10 2013 21 8 227 A1 discloses an ignition system in which a

High voltage generator generates a spark, which then supplied by a boost converter with electrical energy and

is maintained.

Due to spark erosion, the electrodes of the spark gap are exposed to a load which leads to malfunction and finally to failure of the spark gap

Ignition system can lead. A check of the electrode spacing, for example, by removing the spark plugs and measuring the

Electrode distance can be made. During operation, however, occurring malfunctions can not be clearly assigned.

In particular, it is not possible to initiate measures during ongoing operation for troubleshooting. For example, it would be

desirable, the state of wear in the form of an on-board diagnosis

(OBD), so that needs-based provision of

Voltage supply to the voltage generator and a needs-based

Provision of suitable spark energy can be made. While in the new condition of the candle, the need for the

Voltage generation and the spark energy are low, they increase with

Reaching the wear limit of the spark plug. This would provide the advantage of reducing the energy consumption of a new spark plug, the

To reduce power loss, to prevent heating of the ignition system and a thermal and electrical aging and erosion of the spark plug. It is therefore an object of the present invention to meet the needs identified above.

Disclosure of the invention

The object identified above is achieved by a method for checking electrodes of a spark gap of an ignition system for a combustion chamber of a spark-ignition internal combustion engine. In one In the first step, a spark is generated at the spark gap in an operating condition in which ignition of an ignitable mixture in the combustion chamber occurs

Combustion chamber does not take place. In particular, the spark for this purpose can be generated in such a power stroke of the internal combustion engine, in which there is no ignitable mixture in the combustion chamber. In a second step, a parameter representing the spark current and / or the spark voltage and / or the spark duration is determined. The parameter may also be a characteristic function determined over time. In this case, the time course of the parameter over time is characterized and evaluated. Subsequently, the parameter or the characteristic is compared with a predefined reference.

The reference may, for example, designate target values for the parameter or nominal characteristics of the characteristic over time. For example, by the reference ranges for spark current, spark voltage and / or duration can be defined, in which the characteristic or characteristic may not be advised. For example, too low a spark current, too high a spark voltage or too short spark duration for a safe mixture ignition in the combustion chamber is problematic. By the present invention, a

Check the electrodes during operation and take immediate action if necessary. A possible measure, for example, adjusting an energy to build up the voltage for

Sparking and / or to maintain a spark for

Be mixture flame. This can be done in particular depending on a difference of the parameter or the characteristic and the reference. The adjustment of the energy can be made for a current or a future ignition process. This will be one for the

Mixture ignition used appropriate energy, so that a safe mixture ignition at an electrically high efficiency of

Ignition system is realized. The dependent claims show preferred developments of the invention.

The reference may be designed as a first threshold, which is determined based on the electrode spacing during the initial startup of the ignition system (eg factory) and taking into account a maximum allowable wear. Of course, several values can also be used as a reference or a continuous assignment of a reference function and corresponding measures for adapting the electrical energy provided be provided. While discrete values require less memory as a reference, a continuous reference function provides the best possible adjustment to the operation of the ignition system. The spark can be generated, for example, with a primary voltage generator and in particular with a step-up converter, preferably exclusively with the step-up converter, maintained (corresponding to an ignition system, as disclosed in DE 102013 218 227 A). Such an arrangement allows an exact control of the electric energy given to the spark gap, in the knowledge of which the determined parameter can be evaluated very accurately to determine conclusions on, for example, a distance between the electrodes of the spark gap and / or their erosion state.

For example, comparing the characteristic to the reference may include thresholding. Decreases or increases the parameter or the

Characteristic below or above a predefined threshold, may be one of the threshold undershoots or overshoots associated class for the

Electrode state detected and the class possibly assigned

Measures can be initiated. In the case of a characteristic function determined over time, in which also the reference is at least two times

one after the other has values for the identification function, a

Characteristic of the characteristic function are evaluated, classified and used as a reason for the initiation of countermeasures. A preferred time for generating the spark is such

Condition in the combustion chamber, which has a predictable or known impact on the characteristic of the spark. Such is, for example, given when there is the least possible turbulence in the combustion chamber. In this way, a current value for the characteristic and / or a value set for the characteristic function can permit direct conclusions to be drawn about the state of the electrodes. On the other hand, in the case of a spark provided according to the prior art for igniting a flammable mixture, turbulence and pressure fluctuations influence the wider scope of the invention

aforementioned parameters, so that a direct inference to the condition of the electrodes is difficult. For example, the spark may be generated in an exhaust stroke, wherein preferably the intake valves of the internal combustion engine are closed. First, there are particularly suitable conditions in the combustion chamber in this stroke, on the other hand damage to the internal combustion engine due to the closed intake valves can be effectively prevented even in the case of remaining ignitable mixture in the combustion chamber. The

Using the boost converter allows the generation of an im

Substantial stationary spark current and / or a substantially stationary electrical power. Both sizes can be suitable

States in the combustion chamber can be generated by the activation of the boost converter, in response to what the electrode state or distance as a substantially sole cause of a current value of the characteristic can be determined particularly well. If a spark-ignition voltage exceeds the reference as a parameter and / or a spark current as the characteristic falls below the reference, the ignition system can be made to have a higher spark current and / or a higher voltage supply and / or a higher output power

provide. The ignition system can thus be made to provide a higher voltage supply, since the voltage requirement for

Sparking increased due to the increased electrode spacing. In other words, the voltage generating unit must be supplied with more electrical energy, which can be done for example by a so-called. Boosf 'operation provided in the ignition system boost converter (HSS), in which from a comparatively low input voltage, a higher

In addition, the ignition system can be made to provide a higher output power (and thus a higher spark current), which can be realized, for example, via a changed operating mode of a mixture ignition boost converter provided in the ignition system

Measure in terms of the output variables of a used

Hochsetzstellers and be initiated via the primary voltage generator. By increasing the electrical power provided at the spark gap and by increasing it via the primary voltage generator

Voltage supply can be compensated for an increased distance / erosion state of the electrodes in certain areas. An exchange of the electrodes can be delayed in this way, without jeopardizing the reliability of the ignition system according to the invention.

The characteristic variable or the characteristic function can preferably be determined in a stationary state (unchanging over time). This may relate in particular to the electrical processes and / or the chemical processes in the combustion chamber or at the spark gap. Stationary operations allow an accurate determination of the characteristic or the characteristic, which in turn allows an exact determination of required measures is possible.

In the case that an electrical voltage is used as the reference, it can be determined whether an exceeding condition is satisfied by determining whether the spark gap spark exceeds the predefined reference. Alternatively or additionally, in the event that an electric current is used as a predefined reference, it can be determined whether a

Underrun condition is met by determining whether the spark current or an output current of a boost converter used to energize the spark gap is below the reference. In response to the overflow condition or the underflow condition, a voltage supply for spark generation can be increased. Alternatively or additionally, an output power of a used

Primary voltage generator or a boost converter can be increased. For this purpose, in particular a spark current and / or an output current of

Hochsetzstellers be increased. In this way, the operation of the ignition system according to the invention can be energetically optimized and yet

be made functionally reliable.

Using the reference, the detected (e.g., measured)

Characteristic or characteristic with regard to readiness for operation of the

Electrodes are classified. In response to this, an error signal can be output which, for example, leads to the display of a corresponding message in a vehicle equipped with the ignition system or to a fault memory entry which can be read out in a workshop. If replacement of the electrodes is required, replacement can be made quickly in this way. The voltage supply at the electrodes of the spark gap can

For example, be increased gradually until a predetermined second threshold is reached. Subsequently, it can be checked whether the parameter and / or characteristic has reached or have reached a suitable value with respect to the reference. Here, the second threshold

For example, a maximum allowable characteristic or characteristic

indicate from which an electrically safe operation of the

Ignition system and / or an energetically meaningful operation of the

Ignition system and / or a permanent reliability of the ignition system are no longer guaranteed.

Preferably, upon reaching the predetermined second threshold, an error signal indicating the necessary replacement of the electrodes (e.g., a spark plug) may be output. The error signal can be stored, for example, in an error memory and / or for optical and / or acoustic

Output of a signal to a user of the ignition system can be used.

According to a second aspect of the present invention, an ignition system for a spark-ignition internal combustion engine is proposed. This includes a spark gap, a primary voltage generator for generating a

Spark on the spark gap and an evaluation unit. Of the

Primary voltage generator can be configured for example as ignition coil or as ignition transformer. The evaluation unit can be used, for example, as a programmable processor, programmable controller, ASIC or FPGA (Field

Programmable Gate Array) be configured. By the evaluation unit, which can evaluate the characteristic and / or the characteristic of the electrical state variables on the spark gap and predefined references, the ignition system according to the invention is adapted to carry out a method as has been described in detail in connection with the first aspect of the invention. The features, combinations of features and the advantages resulting therefrom correspond to those set forth in connection with the first aspect of the invention so that reference is made to the above statements to avoid repetition.

The ignition system according to the invention can also have a step-up converter for maintaining a spark whose output lies in an electrical mesh with the spark gap. The boost converter is on set up in this way, a predefined electrical variable, in particular an output current and / or an output voltage and / or a

To feed output power in the spark gap, which is better controlled by an ignition transformer. On this basis, the determined characteristics or the determined characteristic function in conjunction with the predefined reference can directly allow conclusions to be drawn about the electrodes of the spark gap. If the ignition system or its evaluation by the result of

Comparing the characteristic / characteristic with the predefined reference determines the need for this, it may be the operation of the boost converter, so its electrical output or the voltage supply of

Adjust the primary voltage generator accordingly. Even an advanced state of wear of the electrodes thus does not jeopardize the functionality of the ignition system according to the invention.

Brief description of the drawings

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

1 shows a circuit diagram according to a first embodiment of an ignition system according to the invention;

FIG. 2 shows an illustration of crank angle ranges in which the ignition spark according to the invention can advantageously be generated; and

Figure 3 is a flow chart illustrating steps of a

Embodiment of a method according to the invention.

Embodiment 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 secondary side 4 of the step-up transformer 2 is supplied via an inductive coupling of the primary coil 8 and the secondary coil 9 with electrical energy and has a the prior art diode 23 for power-on suppression, which diode 23 can 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 to ground 14, via which the Zündstrom \ _{2 is} to ignite the combustible gas mixture. At the spark gap 6 is located at the ignition usually a fluctuating spark ignition voltage U burn on.

According to the invention, a boost converter 7 between the electric

Power source 5 and the secondary side 4 of the step-up transformer 2 is provided. Further, an inductor 15 is connected via a switch 22 and a diode 16 to a capacitor 10, whose one end is connected to the secondary coil 9 and the other end to the electrical ground 14. The inductance serves as an energy store in order to maintain a current flow. The diode 16 is oriented in the direction of the capacitance 10 conductive.

Between the capacitor 10 and the secondary coil 9 is a shunt 19 as

Power measuring means or voltage measuring means provided, the measuring signal of the switch 22 and the switch 27 is supplied. In this way, the switches 22, 27 are arranged to respond to a defined range of the current intensity i ₂ through the secondary coil 9. The diode 16 facing terminal of the switch 22 is connected via a further switch 27 to the electrical ground 14 connectable. To secure the capacitance 10 is a Zener diode 21 in

Reverse direction parallel to the capacity 10 switched. Furthermore are

Switching signals 28, 29 indicated, by means of which the switches 22, 27 can be controlled. While the switching signal 28 a turn on and

Represents "closed" represents an entire ignition cycle, the switching signal 29 outlines a simultaneous alternating signal between "closed" and

"open". When the switch 22 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 switches 22, 27 are closed. When the switch 27 is open, the current is conducted via the diode 16 to the capacitor 10. The adjusting in response to the current in the capacitor 10

Voltage adds to that across the secondary coil 9 of the

Up transformer 2 dropping 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 inductance 15 by closing the switch, in order to reopen the

Switch 27 to load this energy back to the capacitor 10. The control 31 of the switch 30 provided in the primary side 3 can be seen kept significantly shorter than that for the switches 22 and 27 is the case. Since the switch 22 does not assume a decisive function for the processes according to the invention, but merely switches the circuit on or off, this is merely optional and can therefore also be dispensed with. If, according to the invention, such a time is selected for the generation of the spark at the spark gap 6, at which the spark-burning voltage U _{b is} essentially independent of the gas mixture within the combustion chamber, electrical characteristics at the spark gap 6 can be determined, for example, via the shunt 19 in the evaluation unit 36 of the ignition system are evaluated for conclusions on the electrode spacing. By way of the output-side capacitance 10, the boost converter 7 provides to PO an electric power adapted in response to the aforesaid evaluation in order to determine the duration of the

Zündfunkens and the spark current i ₂ in for a reliable

Mixture inflammation to bring appropriate ranges of values.

FIG. 2 shows suitable regions for generating the spark proposed according to the invention over the crank angle. While the to

Flame ignition at 0 ° crank angle and 720 ° crank angle serve sparks of the mixture ignition are the marked

Crank angle ranges 13 between 180 ° and 360 ° and between 900 ° and

1080 ° suitable to generate a spark at the spark gap without igniting an ignitable mixture in the combustion chamber. In particular, comparatively low pressures and turbulences are prevalent in these crank angle ranges, so that a comparatively low energy is required for generating the spark.

FIG. 3 shows steps of an exemplary embodiment of a method according to the invention. In step 100, a spark at the spark gap in a

Operating condition without ignition of an ignitable mixture in the

Combustion chamber generated. Preferably, the spark is therefore in an ejection

Power stroke generated. In step 200, a spark current characteristic over time is determined and compared in step 300 with a predefined reference. In this case, the need is determined, due to an erosion-induced increased electrode spacing in step 400, the spark current by increasing the output of a to maintain the

Ignite sparks used boost converter. In order to maintain the advanced state of erosion of the electrodes despite the invention To document operational readiness of the ignition system, a fault memory entry is made in step 500, which suggests to renew the spark plugs during a next workshop visit. According to the disclosure of the wear information

For example, to the on-board diagnostic (OBD) are used to make the spark plug change dependent on demand and otherwise adjust the electrical characteristics of the ignition system to the current state of wear. Moreover, the present invention enables a reduction in the provision of electrical power that is always required in the prior art

More energy to ensure a proper ignition. The analysis according to the invention enables a reduction of these safety reserves and thus an increase in the efficiency of the ignition system. In addition, by a needs-based provision of electrical energy the

Spark erosion at the electrodes reduced. The thermal and electrical stress of the components of the ignition system can be reduced.

In real applications, the inventive method, for example, every 1000 km driving route with the ignition system according to the invention

equipped vehicles are performed. For stationary internal combustion engines, for example, a performance can be provided every 5 to 10 hours of operation. It is crucial to ensure that the conditions in the combustion chamber are constant. In other words, temperature, pressure, flow velocity must be known or predictable, at least within narrow limits. A suitable operating condition is

For example, an idle at a predefined oil / cooling water temperature.

Even if the aspects of the invention and advantageous

Embodiments with reference to the attached

Drawings of the illustrated embodiments are 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 for generating a spark on a spark gap (6) in a combustion chamber of a spark-ignition internal combustion engine, characterized by the steps of generating (100) the spark on the spark gap (6) in an operating state without ignition of an ignitable mixture in the combustion chamber,

Determining (200) one of the spark current (i ₂ ) and / or the spark voltage (U _br enn) and / or the spark duration

representing parameter or characteristic

Compare (300) the characteristic or characteristic with a reference

Adjusting an energy to build up the voltage to spark and / or maintain a spark for mixture ignition, in particular for a future ignition, depending on a difference between the characteristic or the characteristic and the reference.

The method of claim 1, wherein the value of the reference is a first threshold set based on the spark gap at initial start-up of the ignition system and taking into account maximum allowable wear.

The method of claim 1 or 2, wherein the spark with a

Generated primary voltage generator (2) and in particular with a boost converter (7), preferably exclusively with the boost converter (7) is maintained.

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

Comparing (300) the characteristic with the reference includes an evaluation of a characteristic of the characteristic over time. Method according to one of the preceding claims 1 to 4, wherein the spark at a time without the presence of flammable mixture, and in particular at a time with low turbulence in the combustion chamber, is generated.

Method according to one of the preceding claims 1 to 5, wherein the spark in an exhaust stroke, in particular with closed intake valves of the internal combustion engine is generated.

Method according to one of the preceding claims 1 to 6, wherein the spark by means of a constant electric power of a

Hochsetzstellers (7) is maintained.

Method according to one of the preceding claims 1 to 7, wherein the characteristic is determined in a substantially stationary state.

Method according to one of the preceding claims to 8 further comprising

in the event that an electrical voltage is used as the reference, determining whether an overrun condition is satisfied by determining whether the spark voltage (U _br hen) exceeds the reference, or for the case that an electric current is used as a reference , Determine if one

Underrun condition is satisfied by determining whether the spark current (l ₂ ) or an output current (l _H ss) of a

Boost converter (7) falls below the reference,

Increasing (400) a voltage supply for sparking and / or increasing (400) an output power of the

Primary voltage generator or the boost converter (7), in particular by increasing the spark current (l ₂ ) and / or an output current (l _H ss) of the boost converter (7) when the

Exceeding condition or the underflow condition is satisfied.

Method according to one of the preceding claims 3 to 9, characterized in that a voltage supply by the

Primary voltage generator or by the boost converter is increased.

1 1. Method according to one of the preceding claims, characterized

characterized in that the voltage supply to the electrodes is gradually increased until a predetermined second threshold is reached.

12. The method of claim 1 1, characterized in that after exceeding the predetermined second threshold value, an error signal is output, indicating the necessary replacement of the electrodes.

13. Ignition system for a spark-ignition internal combustion engine comprising

a spark gap (6),

a primary voltage generator (2) for generating a spark at the spark gap (6), and

an evaluation unit (36),

characterized in that

the evaluation unit (36) is designed to carry out a method according to one of the preceding claims 1 to 12.

14. The ignition system of claim 13, further comprising

a boost converter (7) whose output (P ₀ ) is in an electrical mesh with the spark gap (6), wherein the boost converter (7) is arranged, a predefined electrical variable, in particular an output current (l _H ss) and / or a Output voltage (U HSS) and / or an output power, to maintain a spark in the spark gap (6) feed.

An ignition system according to claim 13 or 14, wherein the evaluation unit (36) is arranged to adjust an operation of the boost converter (7) or a primary voltage generator (2) in response to the result of the comparing (300).