DE102013010685A1 - Method for controlling the ignition energy - Google Patents

Abstract

A method for regulating the ignition energy, the method being implemented with an ignition system (1) of an internal combustion engine with external ignition, which ignition system (1) has an ignition coil (3) with a primary circuit (5) and a secondary circuit (7) and one in the secondary circuit (7) has a spark plug (11) arranged on a combustion chamber of the internal combustion engine, with a setting specification (EZS, i + 1 = f (IZS, i + 1, tZS, i + 1) for a current work cycle (i + 1) of the internal combustion engine ) is determined as a function of a determined breakdown voltage (UZ, i) for each of the previous work cycle (i) and is made available for regulating the ignition energy (EZ) in the current work cycle.

Description

The present invention relates to a method for controlling the ignition energy according to the preamble of claim 1.

In the prior art are from the document DE 10 2010 015 998 A1 a generic electronic ignition method and an ignition system for a spark-ignition internal combustion engine, which counteract the ignition energy in the event of a fault, ie to a value at the error, such as. As misfiring, are effectively avoided.

Proceeding from this, the present invention has the object to provide an executable in particular with a pre-chamber spark plug method, which allows an improved energy-optimized and thus wear-optimized control of ignition.

This object is solved by the features of claim 1.

Advantageous developments and embodiments of the invention are specified in the further claims.

According to the invention, a method is proposed for regulating the ignition energy, wherein the method is provided for execution with an ignition system of an internal combustion engine with spark ignition. Preferably, the spark-ignition internal combustion engine z. B. a gas engine. The ignition system which can be used with the method has an ignition coil with a primary (current) circuit and a secondary (current) circuit and a spark plug arranged in the secondary circuit on a combustion chamber (cylinder) of the internal combustion engine, particularly preferably a pre-chamber spark plug.

The inventive method is characterized in that for a current working cycle of the internal combustion engine, a steep default (E _{ZS, i + 1} ) = f (I _{ZS, i + 1} , t _{ZS, i + 1} )) in response to a detected breakdown voltage, in particular an actual ignition energy, depending on the previous work cycle is determined and is provided for the control of the ignition energy (in the current work cycle). The setting for setting a minimum ignition energy in the current working cycle is preferably provided.

In particular, by the Arbeitstpielauflösung invention can be provided over the operation of the internal combustion engine advantageously always optimized, especially minimal ignition energy, so that the wear of the spark plug significantly reduced and thus the service life is increased, woneben breakdown voltage and actual ignition energy can be determined in an advantageous simple manner, For example, be provided by commercially available ignition control devices at an output as tappable information already.

In the context of the present inventive method is further preferred, the expended ignition energy or the control target for the current cycle further depending on a molecular concentration or density (of the mixture) in the combustion chamber and the electrode gap of the spark plug and / or at least one engine operating variable load, calorific value , Burning rate and combustion air ratio, in particular each of the previous cycle to determine.

O. a. specified (engine operating) variables (density, electrode spacing, load, calorific value, burning rate and combustion air ratio), which are, for example, measured variables or calculated, can be correlated for the provision of the control input in a respective control loop, for example, with a map (which z. B. was generated at the test bench).

According to the invention, it has been recognized in connection herewith that it is precisely the burning rate (function of pressure, temperature, fuel concentration) and the electrode spacing for the determination of the respective setting value (s) that represent significant quantities and are preferably taken into account. In particular, the consideration of the actual electrode spacing makes it possible to regulate the minimum energy in the respective working cycle. It has been found that the higher the breakdown voltage, the lower the spark duration requirement, ie the time required for the glow phase (which is essentially determined by a default value for t _{ZS, i} or the spark duration).

In a particularly simple manner, the breakdown voltage can be calculated, for example, from the course of the primary current or the primary voltage (each in the primary circuit). The primary current can be measured for this purpose, for example.

Within the scope of the proposed method, it is provided that a spark duration and / or a current (for the current operating cycle) can be set via the setting input (E _{ZS, i + 1} ) = f (I _{ZS, i + 1} , t _{ZS, i + 1} )). in the secondary circuit) are set in the current working cycle, that is, the default setting each includes a default value for the spark duration and / or the (to be set in the secondary circuit) current. By means of the default value for the current, the mean secondary current level can preferably be predetermined. An adjustment or default values for current or spark duration can or can be determined based on a map.

Generally, it is provided according to the invention that the method is carried out iteratively. For the start of the method, a start parameter set can be provided, which is predetermined by the motor parameter set, for example. A parameter set which contains a start specification can be determined, for example, at the (engine) test bench.

The invention also proposes an ignition system for carrying out the method described above. The ignition system preferably has an ignition energy regulator, which may furthermore preferably be provided in the form of the engine controller (ECU). In addition, an ignition control device may be provided, which cooperates with the ignition energy regulator. Alternatively, the ignition energy regulator may also have the functionality of the control unit according to the invention.

For example, the controller may provide the ignition controller with information about the secondary voltage or breakdown voltage for the control, and in particular also the ignition energy used. The ignition energy regulator in turn can transmit the control variable determined therefor for the current working cycle to the ignition control device for the provision of the ignition energy by the same.

The method proposed according to the invention can be carried out in particular with a multi-cylinder internal combustion engine such that the ignition energy is regulated individually for each cylinder. For this purpose, a setpoint can be determined for each cylinder for a respective working cycle. Such a setting specification comprises in particular a cylinder-individual specification for the spark duration, in particular also the current, for example - as described above - for the mean secondary current level.

Further features and advantages of the invention will become apparent from the following description of embodiments of the invention, with reference to the figures of the drawings, which show details essential to the invention, and from the claims. The individual features can be realized individually for themselves or for several in any combination in a variant of the invention.

Exemplary embodiments of the invention are explained below with reference to the accompanying drawings. Show it:

1 exemplary and schematically an ignition system of an internal combustion engine for carrying out the method according to a possible embodiment of the invention;

2 an example and schematically a diagram illustrating the process flow according to a possible embodiment of the invention.

In the following description and the drawings elements of the same or comparable function correspond to the same reference numerals.

1 exemplifies and simplifies an ignition system 1 for carrying out the method according to the invention. The ignition system 1 , which is provided for an internal combustion engine (not shown), has an ignition coil 3 with a primary (electricity) circle 5 and a secondary (current) circle 7 on, with the ignition coil 3 acts as energy storage and transformer.

The primary side 5 the ignition coil 3 is via an ignition controller 9 supplied with a current or primary current, which primary current for generating a high voltage on the secondary side 7 is suitably interruptible, for example via a switch of the primary side 5 (not shown). The switch is for example an IGBT or generally a transistorized switch, which in particular is part of the control unit 9 can be.

The induction-based generated high voltage on the secondary side 7 is intended to be at one in the secondary circuit 7 on a combustion chamber or cylinder of the internal combustion engine (not shown) arranged spark plug 11 , in particular in the form of a pre-chamber spark plug to generate a spark, ie between the electrodes 11a . 11b , Successful energy transfer from the spark to the fuel-air mixture to be ignited requires a minimum ignition energy.

With the ignition controller 9 , which provides an adjustment for the spark duration and preferably also of the power supply, for example in the form of a PWM output option (PWM pulse width modulation), continues to act an ignition energy regulator 13 together, which is preferably formed by an engine controller (ECU) of the internal combustion engine. The ignition regulator 13 is z. B. connected to one or more sensors (not shown), which provided for the process engine operating information to the controller 13 provide.

2 exemplifies the inventive method for controlling the ignition energy, which with the ignition system described above 1 an internal combustion engine is executable.

In the method becomes for a current working cycle i + 1 of the internal combustion engine a Setpoint E _{ZS, i + 1} = f (I _{ZS, i + 1} , t _{ZS, i + 1} ) = f (U _{Z, i} , H _{U, i} , λ _i , P _i , v _{B, i} ) depending a determined breakdown voltage U _Z , in particular also an actual ignition energy E _ZI , depending on the previous working cycle i determined and provided for the control of the ignition energy E _Z in the current working cycle, ie to the control unit 9 to hand over. The control unit 9 thus sets current I _{ZS, i + 1} and spark duration t _{ZS, i + 1} at the spark plug 11 via ignition coil 3 according to I _{ZS, i + 1} and t _{ZS, i + 1} (it should be noted here that the indexing I is an actual value, the indexing S is intended to denote a desired value or a specification, and Z an ignition process).

Based on the height of the (cylinder-specific) breakdown voltage U _Z , the new spark duration t _{ZS, i + 1} can be determined in the proposed method, with the new or current spark duration t _{ZS, i + 1 being} set the lower, depending higher is the breakdown voltage U _Z in the previous cycle. Furthermore, the magnitude of the (feed) current I _{ZS is} correlated with the ignition time (ZZP) and the burn rate estimable from the calorific value, lambda, pressure and temperature in the combustion chamber. In this case, the (feed) current I _Z can be reduced with increasing burning speed and later ZZP. The adjustment limits for the parameters spark duration t _Z and supply current I _Z are increased by the performance of the ignition controller 9 and down given, for example, from the claim to the engine running rest.

The breakdown voltage U _Z as well as the actual ignition energy E _ZI , ie that of the respective working cycle, is preferred by the ignition controller 9 to the controller 13 reported, s. Feedback path or interface 15 in 1 and 2 , Preferably, the breakdown voltage U _{Z of} the respective working cycle is estimated, in particular advantageously calculated inexpensively from a primary current profile of the working cycle. The control unit 9 may be suitable for this purpose. Alternatively, the breakdown voltage U _Z may be measured, for example.

For the first working game, i = 0 in 2 , a parameter set determined on the engine test bench with starting specifications for the initial spark duration t _{ZS, i = 0} and the current to be set in the secondary circuit I _{ZS, i = 0 is used} as setting for E _Z , s. 2 , The starting values can be in the controller 13 be deposited.

In the context of the control method, the ignition energy E _Z to be expended for the current working cycle (i + 1) is furthermore preferably dependent on a density in the combustion chamber and the electrode spacing of the spark plug 11 and / or at least one engine operating variable determined from load P, calorific value H _u and combustion air ratio λ of each of the preceding operating cycles, see eg. 2 according to which the setting input (s) E _{ZS, i + 1} or (I _ZS , t _ZS ) _{i + 1} is / are determined as a function of H _u , λ, P and U _Z.

This will be explained below, especially in conjunction with 2 discussed in more detail.

According to the invention, it has been recognized that the electrode spacing EA on the spark plug can be determined from a large number of chemical and physical influencing factors which might have to be considered in the context of the ignition energy application 11 , in particular also the calorific value H _U , the combustion air ratio λ and the instantaneous power output P (all influencing variables of the combustion speed), are to be considered as essential. Their influence can be compensated in the context of the method according to the invention for optimized ignition energy supply or is corrected.

Generally applies to the applied minimum energy of a particular ignition process (combustion rate v _B = f (P, λ, H _U )): E _{Z, Min} = f (P, λ, H _U , E a) (1)

Furthermore, it must be considered that the following applies to the ignition energy: E _Z = ∫U (t) I _Z (t) dt (2)

Based on the laws (1) and (2), in the context of the method according to the invention for each working cycle, a setting (E _{ZS, i + 1} in 2 ) are determined for the energy E _Z to be expended, in particular for a corresponding adjustment of the current I _Z and / or the spark duration t _Z. Depending on the respective engine operating situation, the disturbances P, λ, H _U , EA are to be regarded as differentiated with regard to their effect as such.

In this case, the following relationships were identified as essential and the regulation for the determination of the setpoint E _{ZS of} a respective work cycle as a basis: P ↑ then U _Z ↑↑, I _Z ↓↓ and t _Z ↓↓ = f (U _Z ) λ ↑ then U _Z ↑, I _Z ↑ and t _Z ↑ = f (v _B ) H _u ↑ then U _Z ↓, I _Z ↓ and t _Z ↓ = f (v _B ) EA ↑ then U _Z ↑↑, I _Z ↓↓ and t _Z ↓↓ = f (U _Z )

It can be seen that the burning speed v _{B of} the compressed mixture and the breakdown voltage U _{Z are} significant. In the course of test series, it was recognized that the influence of the calorific value H _U in a gas engine and the use of fuel in the form of natural gas is relatively low. It has also been found that the air ratio λ is not significant in natural gas applications, but could be relevant to off-gas applications such as biogas or hydrogen.

U_Z

Durchbruchsspannung [V]

c

Proportionalitätskonstante [Vm²/kg]

ρ_Z(ZZP)

Dichte des Gemisches im Zylinder zum Zündzeitpunkt [kg/m³]

EA

Elektrodenabstand der Zündkerze [m]

wobei die Dichte ρ_Z(ZZP) zum Beispiel anhand des Motorbetriebspunkts ermittelbar ist.Furthermore, E _{ZS is} taken into account in the context of the method, which may be valid for the determination of a respective setpoint U _Z = c · ρ _Z (ZZP) · EA (3) With

U _Z

Breakdown voltage [V]

c

Proportionality constant [Vm ² / kg]

ρ _Z (ZZP)

Density of the mixture in the cylinder at the ignition point [kg / m ³ ]

EA

Electrode distance of the spark plug [m]

wherein the density ρ _Z (ZZP) can be determined, for example, based on the engine operating point.

With knowledge of U _Z and ρ _Z (ZZP), it is thus possible according to the invention to estimate both the electrode spacing EA and the spark duration t _ZS to be set for the ignition energy E _ZS or the mean secondary current I _{ZS to} be set. In the context of the control method proposed according to the invention, the burning rate as a function of pressure, temperature, calorific value and lambda of the mixture in the combustion chamber is also taken into account for setting the spark duration t _Z and the current I _Z (primary or secondary current) or the ignition energy E _Z to be expended , as far as at a certain U _Z / EA (4) a certain average secondary current I _Z or a specific spark duration t _Z (I _Z and t _Z = f (E _{Z, min} )) is required for a successful ignition. The latter relationship can be determined empirically by means of an experimental test, but can also be correlated on the basis of an estimate of the burning rate and spark volume.

In the case of the regulation of the ignition energy E _Z according to the method, (a) the secondary voltage or breakdown voltage U _{Z, i} is transmitted via the interface 15 from the ignition controller 9 to the ignition regulator 13 returned. Together with further quantities such as P _i , H _{u, i} and λ _i , (b) the transmitted breakdown voltage U _{Z, i} for recalculation of E _{ZS, i + 1} into the controller 13 used. After (c) calculation of E _{ZS, i + 1} , this determined setting is via the communication interface 15 (d) to the ignition controller 9 returned.

As a result, (e) becomes E _{ZS, i + 1} = f (I _{ZS, i + 1} , t _{ZS, i + 1} ) in the controller 9 implemented and from now on (f) in the primary circuit 5 or via the ignition coil 3 in the secondary circuit 7 fed, bringing the spark plug 11 receives a modified secondary current I _Z and a modified spark duration t _Z. Hereinafter, steps (a) to (f) are repeated as part of the iterative process execution.

By means of the procedure becomes the spark plug 11 Demand-dependent energy as a function of power, calorific value, emission of the engine and the state of wear of the spark plug 11 fed. Opposite a z. B. constant Zündparametereinstellung is significantly reduced by the Kerzenverschleiß and thus achieved a significant operating cost reduction for the engine operator.

Furthermore, very small spark plug electrode distances can be operated with this method, without the necessarily disproportionately high ignition energies over the entire service life of a spark plug 11 to drive, because over the secondary voltage at any time the state of wear of the candle 11 can be estimated. Furthermore, a service or replacement recommendation to the engine operator via the engine controller 13 and a tethered alarm communication interface, which also allows wear to be optimized on an application-by-case basis for each cylinder, engine operating load, and chemical stress from the main combustion chamber, all of which is spark plug wear 11 participate.

LIST OF REFERENCE NUMBERS

1

ignition system

3

ignition coil

5

primary circuit

7

secondary circuit

9

Ignition control unit

11

spark plug

11a, b

electrode

13

Zündenergieregler

15

interface

QUOTES INCLUDE IN THE DESCRIPTION

This list of the documents listed by the applicant has been generated automatically and is included solely for the better information of the reader. The list is not part of the German patent or utility model application. The DPMA assumes no liability for any errors or omissions.

Cited patent literature

• DE 102010015998 A1 [0002]

Claims (10)

Method for controlling the ignition energy, wherein the method of execution with an ignition system ( 1 ) of an internal combustion engine with spark ignition is provided, which ignition system ( 1 ) an ignition coil ( 3 ) with a primary circuit ( 5 ) and a secondary circuit ( 7 ) as well as one in the secondary circuit ( 7 ) arranged on a combustion chamber of the internal combustion engine spark plug ( 11 ), characterized in that for a current working cycle (i + 1) of the internal combustion engine an actuating input (E _{ZS, i + 1} = f (I _{ZS, i + 1} , t _{ZS, i + 1} )) in dependence of a determined breakdown voltage (U _{Z, i} ) each of the previous cycle (i) is determined and provided for the control of the ignition energy (E _Z ) in the current work cycle. A method according to claim 1, characterized in that the setting (E _{ZS, i + 1} ) for the current cycle (i + 1) further in dependence of a density (ρZ (ZZP)) in the combustion chamber and the electrode spacing (EA) of the spark plug ( 11 ) and / or at least one engine operating variable from load (P), calorific value (H _u ), burning speed (v _B ) and combustion air ratio (λ) of each of the preceding working cycle (i) is determined. A method according to claim 1 or 2, characterized in that the breakdown voltage (U _Z ) is calculated. A method according to claim 3, characterized in that the breakdown voltage (U _Z ) from the course of the primary current (I _Z ) and or the primary voltage is calculated. Method according to one of the preceding claims, characterized in that via the setting input (E _{ZS, i + 1} = f (I _{ZS, i + 1} , t _{ZS, i + 1} )), a current (I _ZS ) and / or a spark duration (t _ZS ) can be set in the current working cycle (i + 1). Method according to one of the preceding claims, characterized in that the respective control input (E _{ZS, i + 1} = f (I _{ZS, i + 1} , t _{ZS, i + 1} )) is determined map-based. Method according to one of the preceding claims, characterized in that the method is performed iteratively. Ignition system ( 1 ) for carrying out the method according to one of claims 1 to 7. Ignition system ( 1 ) according to claim 8, characterized in that the ignition system ( 1 ) an ignition regulator ( 13 ) and an ignition controller ( 9 ), wherein the setting (E _{ZS, i + 1} = f (I _{ZS, i + 1} , t _{ZS, i + 1} )) of the Zergergeregler ( 13 ) to the ignition controller ( 9 ) provided. Method according to one of claims 1 to 7 or ignition system ( 1 ) according to one of claims 8 and 9, characterized in that the spark plug is a Vorkammerzündkerze and / or the internal combustion engine is a gas engine.

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