EP1415085B1 - Method for controlling ignition parameters of a spark plug for internal combustion engine - Google Patents

Abstract

The invention is a method for controlling ignition parameters of a spark plug ( 16 ) for an internal-combustion engine whose ignition is controlled by an engine control calculator, with the spark plug receiving a high voltage (U_HT) and a current (I_HT) from an ignition emulator (E). The method establishes a target current and/or voltage values (Ucible_HT, Ucible_Boost, Icible_HT, Icible_Boost) to obtain the desired electric arc at the spark plug electrodes, stores the target values in a parametering unit ( 32 ), measuring at regular intervals, after an ignition command by the calculator, at least one of a voltage (U_HT, U_Boost, U_Batt) and current (I_HT, I_Boost) parameter coming from the emulator, comparing the parameters with the target values, and when variation occur between the measured parameters and the target values, adjusting the parameters to reach the target values for controlling the ignition parameters of a spark plug for an internal-combustion engine. The spark plug receives a voltage (U_HT) and a current (I_HT) from ignition emulator (E). At least one interruption means (K 1 , K 2 , K 3 ) control the voltage applied to the spark plug.

Description

The present invention relates to a method for controlling ignition parameters of a spark plug for an internal combustion engine and an ignition device using such a method.

It is already known to use ignition coils to generate a high voltage applied to a spark plug disposed in an engine. The high voltage applied to the spark plug will create at the electrodes of the latter an electric arc whose energy is used to ignite an air / fuel mixture present in the combustion chamber that includes the engine.

These ignition coils generally consist of a primary winding, called primary, connected to a DC source, such as the battery of a motor vehicle, and a secondary winding, called secondary, connected to a candle and which, under the effect of the voltage applied to the primary, generates a high voltage that will be applied to the spark plug to form the electrodes thereof an electric arc or spark that ignites the air / fuel mixture.

This ignition, the triggering time of which will be determined by a computer, referred to as the engine computer, which a motor usually comprises, is therefore dependent on the quality of the arc, that is to say mainly on its duration and electrical parameters such as the Current intensity, voltage, ...

Currently, the ignition coils that are used in the motors have been the subject of numerous tests to determine empirically their parameters to act in the most efficient way on the candles both in the voltage applied to the secondary and the the duration and current of the arc.

For this, it is planned to vary the voltage at the primary to vary simultaneously the secondary voltage until we find the ideal operating point of this coil.

This has significant disadvantages in the sense that the maximum capacitances of the coils are easily reached because the primary of these coils is quickly saturated with primary current.

In addition, in difficult contexts (poor mixture, high rate of recycled gases, etc.) resulting in poor ignition quality of the air / fuel mixture or even absence of ignition, it is impossible to determine which parameter (voltage , duration or intensity of the arc, ...) could be cause and therefore it leads to use coils with maximum capacity in all areas which aggravates its cost price.

It is also known by an article entitled "Capacitor Discharge Ignition System" published in July 1992 under the reference No. RD 33975, an ignition device comprising an ignition coil whose primary is powered by a voltage-loaded capacitor and a secondary connected to a spark plug.

The primary of this coil is further connected in series with a field effect transistor which acts as a switch whose opening and closing phases are controlled by a control.
Thus, when the control actuates the switch in the closed position, the capacitor discharges into the primary by creating a voltage in the secondary to supply the spark plug under high voltage and generate the arc or the spark at its electrodes.
After a short period of primary power supply, the control then actuates this switch in the open position for a short time, which interrupts the supply of the primary and causes a gradual drop in current thereof. Then this switch is closed before the current in the primary and secondary is zero. These commands for opening and closing the switch are performed repeatedly to obtain an electric arc whose intensity will be decreasing in time.

By these different provisions, it is possible to configure the parameters of this ignition device (in duration of the electric arc to the electrodes of the candle, voltage applicable to the secondary) only for a single type of use.
If it is desired to change these parameters for another type of coil, it is necessary to establish another type of command for closing and opening the switch, or even to change the primary and secondary of the new coil .

He is also known by US 6,138,653 to set current target values and / or to obtain the desired electric arc at the spark plug electrodes, to store these target values in a parameterization unit, to measure at least one voltage parameter and / or current from the emulator, then compare these parameters to the target values and, in case of drift between the measured parameters and the target values, adjust these parameters to reach the target values.

However, as in the case of conventional ignition coils, it is impossible to monitor the operating parameters of this ignition, such as the secondary voltage or the duration of the arc or its intensity, to possibly correct them in case of deviation from reference values.

The present invention proposes to overcome the disadvantages mentioned above by having an ignition device replacing the ignition coil and to easily control all the parameters related to the electric arc of the candle.

For this purpose, a method for controlling ignition parameters of a spark plug for an internal combustion engine whose ignition is ordered by an engine control computer, said candle receiving a high voltage and a current emanating from an ignition emulator, a method in which the target values are determined in current and / or in voltage to obtain the desired electric arc at the electrodes of the candle, these target values are stored in a parameterization unit, measured , at regular intervals, after the ignition command given by the computer, at least one voltage and / or current parameter emanating from the emulator, these parameters are compared with the target values and, in case of drift between the parameters measured values and the target values, these parameters are adjusted to reach the target values, characterized in that a chopper (14) is supplied with voltage by a voltage converter (10) and in that at least one mo interruption yen (K1, K2, K3) of said voltage converter (10) and / or said chopper contained in the emulator (E) for controlling the voltage (U_HT) applied to the spark plug.

Preferably, it is possible to act on at least one chopper interruption means for controlling the voltage rise applied to the spark plug.

It is also possible to act on at least one means of interrupting the chopper to control the voltage drop applied to the spark plug.

It is also possible to act on at least one means of interrupting the voltage converter to adjust the high voltage received by the spark plug.

The invention also relates, for the implementation of the method, to an ignition emulation device for an internal combustion engine according to claim 5.

The control box may include inputs for voltage and / or current signals emanating from the emulator.

Advantageously, the control box may comprise at least one input for at least one target voltage and / or current value to be applied to the spark plug.

The housing may include at least one output for control signals to interrupt means included in the emulator.

Thanks to the invention, it is possible to have variable parameters that will configure the same device for several types of use and get all the information on the adequacy of the arc produced by the candle.

• la figure 1 est un schéma d'un émulateur d'allumage applicable pour le procédé et le dispositif selon l'invention ;
• la figure 2 est un schéma d'un bottier de contrôle d'un émulateur d'allumage selon la figure 1 ;
• la figure 3 montre les courbes théoriques de tension et d'intensité à appliquer à la bougie du dispositif d'allumage ;
• la figure 4 montre les courbes réelles de tension et d'intensité qui sont appliquées à la bougie .

The other features and advantages of the invention will now appear on reading the description which follows, given solely by way of example, and with reference to the appended figures in which:

• the figure 1 is a diagram of an ignition emulator applicable for the method and the device according to the invention;
• the figure 2 is a diagram of a control cabinet of an ignition emulator according to the figure 1 ;
• the figure 3 shows the theoretical curves of voltage and current to be applied to the spark plug of the ignition device;
• the figure 4 shows the actual curves of tension and intensity that are applied to the candle.

On the figure 1 , it is shown an ignition emulator E for an internal combustion engine, especially a motor vehicle, comprising a voltage converter 10 for converting the voltage from a battery 12 to a voltage of 600V, here preferably up to at 400V, and a chopper 14 for generating a high voltage on a candle 16, high voltage which will generate an electric arc or spark at the electrodes of this candle thus making it possible to ignite an air / fuel mixture present in a combustion chamber. an internal combustion engine.

As better visible on the figure 1 the converter 10 comprises a switch K3 making it possible to vary the voltage at its output up to the desired voltage to be applied to the chopper 14.

The chopper 14 whose input is connected to the output of the converter 10 comprises a transformer 18 equivalent to an ignition coil with a primary 20 and a secondary 22.
The primary 20 comprises two switches, a high switch K1 for controlling the rise of current in this primary and a high switch K2 for the descent of this current in the same primary.
The secondary 22 is connected, in a conventional manner, to the spark plug 16 by an electrical conductor 24.

This emulator is connected to a control box 30 (see figure 2 ) which receives measurement input signals from the emulator E, target value signals from a parameterization unit 32 via a channel 34 and which outputs signals to control the switches K1 and / or K2 and / or K3 and / or K4 of emulator E.

The parameterization unit 32 contains all the theoretical target values that make it possible to obtain the desired electric arc at the candle for a determined period of time.
These values are in particular the voltage (Ucible_HT) and the current intensity (Icible_HT) at the output of the chopper 14, the voltage (Ucible_Boost) and the intensity of the current (Icible_Boost) at the output of the converter 10. These target values thus make it possible to determine the maximum voltage at the secondary (Us max), the moment (Tmax US) at which this maximum voltage must be reached and the voltage (Uarc) to maintain the electric arc at the electrodes of the candle for a determined time (Ts).
According to these values and as visible on the figure 3 a theoretical curve of the voltage U = f (t) to be applied to the secondary has been defined to obtain the desired electric arc at the electrodes of the candle.
According to this curve, after the ignition command has been given by the engine computer, the secondary 22 of the transformer 18 is voltage-loaded by the primary 20, in a substantially linear increasing manner, up to the maximum voltage Us max and during a determined time Tmax Us where is created the arc with the electrodes of the candle. At the creation of the arc, the voltage at the secondary drops sharply to reach a determined voltage value Uarc which will be maintained for a certain period of time Ts to maintain the electric arc. At the end of the time Ts, the secondary will no longer be supplied with voltage and will reach a zero value for the extinction of the arc.

This theoretical secondary supply curve makes it possible to obtain a theoretical waveform I = f (t) of the intensity of the current as a function of the time applied to secondary 22, therefore to the electrodes of the candle, and comprises a maximum of intensity of the current Is of the actual realization of the arc.

With this arrangement, the unit 32 can thus contain values making it possible to simulate all forms of coils with capacitances ranging up to a secondary voltage of 50kV in a time ranging from 10μs to 500μs, an arc duration at the candle electrodes of 10 μs (microseconds) to 10 ms (milliseconds) and a current intensity applied to the secondary up to at 1 A.

The chosen theoretical values are communicated by channel 34 to the box 30 which, in addition, receives the input signals measuring the actual battery voltages (U_Batt), the output of the converter (U_Boost) and the output of the chopper (U_HT) as well as as input signals corresponding to the measurement of the actual currents at the switch K3 of the converter (I_Boost), at the low switch K2 of the chopper (I_K2) and at the output of the chopper (I_HT).

The parameter unit 32 may also contain other values such as the number of arcs in case of multi-spark ignition and the time between two arcs.

In practice and as is visible on the figure 4 the ignition device according to the invention makes it possible to obtain, in the upper part, the voltage curve as a function of the time measured at the secondary and, at the bottom, the curve of the intensity of the current as a function of the time recorded at the secondary.
On these curves, it can be seen that the ignition device has to adjust all the parameters necessary for the voltage curve to correspond to that of the theoretical curve of the figure 3 so that the intensity curve has a general shape approximating that of the theoretical curve.

• on stocke dans l'unité de paramétrage 32 les valeurs cibles en tension et/ou en courant permettant d'obtenir une forme d'onde souhaitée au secondaire 22 et corollairement aux électrodes de la bougie ;
• le boîtier 30 reçoit par la voie 32 les valeurs cibles en tension et/ou en courant ;
• on mesure, après l'ordre d'allumage donné par le calculateur, les paramètres de tension (U_HT, U_Boost,...) et/ou d'intensité (I_HT, I_Boost,...) émanant de l'émulateur
• les valeurs cibles sont comparées aux signaux de mesures réelles de tensions et/ou de courant ;
• en cas de dérive entre les signaux reçus et les valeurs cibles, le boîtier de contrôle 30 envoie des signaux de sortie pour commander un ou plusieurs interrupteurs K1, K2, K3, K4 de façon à ce que ces valeurs cibles soient atteintes.

To achieve this result, the operating process is as follows:

• the voltage and / or current target values are stored in the parameterization unit 32 making it possible to obtain a desired waveform at the secondary 22 and correspondingly to the electrodes of the candle;
• the housing 30 receives by channel 32 the target values in voltage and / or current;
• the voltage parameters (U_HT, U_Boost, ...) and / or intensity parameters (I_HT, I_Boost, ...) emanating from the emulator are measured after the ignition command given by the computer.
• the target values are compared with actual voltage and / or current measurement signals;
• in case of drift between the received signals and the target values, the control box 30 sends output signals to control one or more switches K1, K2, K3, K4 so that these target values are reached.

Preferably, to ensure a good monitoring of the ignition parameters, the voltage and / or current measurements are made every microsecond as soon as the ignition switch of the engine control unit is switched off, that is to say after the ignition was given by this calculator and even before the electric arc is created at the electrodes of the candle.

In practice, if a difference is detected by the control box, the latter will control the switch K3 to increase or decrease the voltage at the input of the chopper 14 which will cause an increase or decrease in the voltage of the primary 20 and by therefore an increase or decrease in high voltage at secondary 22.
The housing can also, thanks to the commands on the switches K1 and K2, control the rise of the current in the primary 20 by the switch K1 and / or the descent of this current through the switch K2, which will have for influence to control the rise and fall of the high voltage that will be applied to the candle 16.

Of course and without departing from the scope of the invention switches K1, K2 or K3 or K4 can be ordered separately or together or in combination.

Thus, thanks to this arrangement, it is possible at all times to manage the parameters of the arc at the electrodes of the candle and more particularly the energy of the arc, its duration, the number of arcs for a determined duration and the time between two arcs in case of ignition multi-spark and that by controlling the voltage and the current of the secondary
In addition, it is also possible to manage the maximum voltage of the secondary 22 and the time required to reach this maximum voltage.

The present invention is not limited to the examples described above but encompasses all variants.

In particular, it can be provided that the emulator E comprises an ionization module 26 which makes it possible to know whether there has been a combustion in the chamber considered of the engine and thus to determine that the ignition parameters are correctly established for achieve this combustion.

In addition, it can also be expected that the emulator E comprises a voltage source 28, variable through a switch K4, and which will allow to inject the calculator that usually comprises a motor, a current similar to that of a ignition coil to prevent any fault in said computer, this current being measured by the housing 30 by the U_Cde channel.

Of course, the invention described above can also be applied to an internal combustion engine simulation bench.
In this case the parameterization unit will be replaced by any means such as a PC computer type calculator, which will allow to directly parameterize a multitude of ignition device with various waveforms that can be generated by the secondary .

Claims (8)

1. A method for controlling the ignition parameters of a spark plug (16) for an internal combustion engine whose ignition is sequenced by an engine control calculator, said spark plug receiving a high voltage (U HT) and a current (I_HT) emanating from an ignition emulator (E), in which method the target values are established as current and/or as voltage (Ucible_HT, Ucible_Boost, Icible_HT, Icible_Boost, etc.) enabling the desired electrical arc to be obtained at the electrodes of the spark plug, these target values are stored in a parameterisation unit (32), at least one voltage parameter (U_HT, U_Boost, U_Batt) and/or current parameter (I_HT, I_Boost) emanating from the emulator is measured at regular intervals after the ignition command given by the calculator, these parameters are compared with the target values and, in the case of a deviation between the measured parameters and the target values, these parameters are adjusted in order to reach the target values, characterised in that a chopper (14) is supplied with voltage by a voltage converter (10) and in that at least one interruption means (K1, K2, K3) of said voltage converter (10) and/or of said chopper contained in the emulator (E) is acted upon in order to control the voltage (U_HT) applied to the spark plug.
2. The method according to Claim 1, characterised in that at least one interruption means (K1) of the chopper (14) is acted upon in order to control the increase in voltage applied to the spark plug.
3. The method according to Claim 1 or 2, characterised in that at least one interruption means (K2) of the chopper (14) is acted upon in order to control the decrease in voltage applied to the spark plug.
4. The method according to one of Claims 1 to 3, characterised in that an interruption means (K3) of the voltage converter (10) is acted upon in order to adjust the high voltage (U_HT) received by the spark plug.
5. An ignition emulating device for an internal combustion engine comprising a spark plug (16) associated with a combustion chamber and supplied with high voltage by an ignition emulator (E) for implementing the method according to one of Claims 1 to 4, characterised in that the ignition emulator (E) includes a voltage converter (10) associated with an interruption means (K3), this voltage converter supplying a chopper (14) associated with an upper interruption means (K1) and a lower interruption means (K2) and in that said device includes a parameterisation unit (32) and a control box (30) which are associated with the ignition emulator (E), said parameterisation unit containing the target values as current and/or as voltage (Ucible_HT, Ucible_Boost, Icible_HT, Icible_Boost, etc.) enabling the obtention of the desired electrical arc at the electrodes of the spark plug, and said box receiving at least one measured parameter of voltage (U_HT, U_Boost, U_Batt) and/or of current (I_HT, I_Boost) emanating from the emulator and comparing these parameters with the target values, so as to adjust these parameters, in the case of a deviation between the measured parameters and the target values, by controlling said interruption means in order to reach the voltage and/or current target values at the output of the voltage converter (10).
6. The device according to Claim 5, characterised in that the control box (30) includes inputs for voltage and current signals emanating from the emulator (E).
7. The device according to Claim 5 or 6, characterised in that the control box (30) includes at least one input (34) for at least one voltage and/or current target value to be applied to the spark plug.
8. The device according to one of Claims 5 to 7, characterised in that the box (30) includes at least one output for command signals to interruption means (K1, K2, K3, K4) which the emulator (E) comprises.

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