EP0827569B1 - Inductive ignition device - Google Patents

Abstract

The invention relates to an inductive ignition device for sparking plugs in an internal combustion engine, with at least one driving circuit for at least one ignition coil and with at least one sparking plug. Said device is characterised in that one of the high voltage switches (13; 13a to 13n) is associated with at least one sparking plug and is moved into a conductive, connected state by a first driving signal of the driving circuit. The spark current (I2) of at least one sparking plug (3; 3a to 3n) moves through said high voltage switch when it is in a connected state, and said high voltage switch is arranged in such a manner that it remains in a conductive state without further driving until the spark stream falls below a certain value (holding current).

Description

State of the art

The invention is based on an inductive ignition device for spark plugs of an internal combustion engine according to the preamble of claim 1, also by one Method for controlling a spark plug Internal combustion engine according to the preamble of the claim 10th

Inductive ignition devices of those mentioned here Kind are known. You can use single spark coils have or with an electronic high-voltage distribution be equipped. Also are Methods of the type mentioned above are known. In particular at high engine speeds it is often problematic to measure ion current perform the combustion behavior the internal combustion engine can be monitored. It has also been shown that in this operating state the one intended for a discharge process Energy not completely dissipated via a spark plug can be, but rather that residual energy after Termination of the ignition process is due to the power loss in the ignition device can rise sharply. It has already been tried a current limitation in the ignition output stage of the ignition device to provide or a current limit to perform over primary resistors. In both However, cases result in high power losses in the ignition stage or in the ignition coil. It was also tries to run the energy through the ignition coil Reduce the withdrawal of the closing time at high speeds. However, the problem has arisen here that not in all operating conditions sufficient voltage and energy supply ensured can be.

Advantages of the invention

The inductive ignition device according to the invention with the features mentioned in claim 1 and the method with the features listed in claim 10 are characterized by the fact that the mentioned here Disadvantages are avoided. It's sure, that performed an ion current measurement can be without the tension and the secondary initial current supplied to the spark plug will have to be reduced. In addition, a so-called residual energy operation in multi-cylinder engines even at high speed, even when activated with only one power amplifier, avoided. It can triggering of the spark plugs at a given energy with a low initial current, so that there is less candle wear.

drawing

Figur 1

ein erstes Ausführungsbeispiel einer induktiven Zündeinrichtung, die jeweils eine Einzelfunkenspule für je eine Zündkerze aufweisen;

Figur 2

eine erste Ausführungsform einer induktiven Zündeinrichtung mit einer elektronischen Hochspannungsverteilung;

Figur 3

eine zweite Ausführungsform einer induktiven Zündeinrichtung mit elektronischer Hochspannungsverteilung und

Figur 4

ein schematisches Diagramm von Spannungen und Strömen, die innerhalb der induktiven Zündeinrichtungen gemäß den Figuren 1 bis 3 gemessen werden können.

The invention is explained in more detail below with reference to the drawing. Show it:

Figure 1

a first embodiment of an inductive ignition device, each having a single spark coil for each spark plug;

Figure 2

a first embodiment of an inductive ignition device with an electronic high-voltage distribution;

Figure 3

a second embodiment of an inductive ignition device with electronic high-voltage distribution and

Figure 4

a schematic diagram of voltages and currents that can be measured within the inductive ignition devices according to Figures 1 to 3.

Description of the embodiments

Figure 1 shows a schematic diagram of a inductive ignition device 1, in which each spark plug 3 of an internal combustion engine also as a single spark coil designated ignition coil 5 assigned which can be controlled via an ignition output stage, from which only the control signal 7 via the time is indicated that on a switching device, here a transistor 9 is given. There is a primary winding on the primary side of the ignition coil 5 11 'provided on the one hand with a Power supply marked with a plus sign and on the other hand via the transistor 9 is connected to ground. On the secondary side the ignition coil 5 is at its high voltage output 11, a high-voltage switch 13 is provided, which in the connection path 15 between the high voltage output 11 and spark plug 3 is arranged. The on that High voltage output 11 connected winding 17 the secondary side of the ignition coil 5 is on the other hand connected to ground via a measuring circuit 19. The Measuring circuit 19 comprises a in parallel connection Zener diode 21 with its cathode at a connection point 23 and is connected to ground with its anode. Is parallel between the connection point 23 and ground a series connection to the Zener diode 21 a capacitor 25 and a diode 27, the cathode to ground and its anode with the capacitor 25 is connected. At the anode of the diode 27 respectively the capacitor 25 is a resistor 29 connected, which is on the other hand to ground. The resistor 29 is therefore parallel to the diode 27. At the junction between diode 27 and the capacitor 25, on which the resistor 29 is connected, there is a measuring voltage output 31, to which a proportional ion current Voltage can be measured.

For each spark plug 3 of the internal combustion engine an ignition coil 5 and preferably also a measuring circuit 19 provided.

The core of the inductive ignition device 1 is the high-voltage switch 13, which is provided on the secondary side of the ignition coil 5 and is designed here as a high-voltage breakover diode, the cathode of which is at the high-voltage output 11 and the anode of which is at the spark plug 3. By means of a dashed, oppositely polarized diode 33 lying parallel to the high-voltage switch, it is indicated that the high-voltage switch 13 is designed to conduct backwards. The diode 33 allows a positive potential to reach the high-voltage output 11 and the connection path 15 to the spark gap 35 of the spark plug 3 even when the high-voltage switch is switched off. The positive potential U is applied to the spark gap 35 via the capacitor 25 in order to be able to measure an ionization current I _ION in a known manner. This ionization current provides information about the combustion process, in particular about knocking of the cylinder assigned to the spark plug 3 and about the combustion taking place in the combustion chamber.

The current flowing on the primary side of the ignition coil 5 through the transistor 9 is designated I ₁ , the current flowing on the secondary side I ₁ . The control signal applied to the base of the transistor 9, which comes from an output stage control, not shown here, is referred to as U _ES . The ignition timing is indicated by a lightning symbol.

The inductive ignition device 1 ', which is shown in FIG is shown schematically, points in principle same components as the ignition device in Figure 1. Matching parts were the same Provide reference numbers.

In the inductive ignition device 1 'according to FIG. 2 is a control signal 7 of a not shown here Power stage control on a turn here switch indicated as transistor 9, which drives a single ignition coil 5 the plurality of spark plugs 3a to 3n lying in parallel can be connected. Between the high voltage output 11 on the secondary side of the ignition coil 5 are the spark plugs via a connection path 15 3a to 3n each via high voltage switch 13a connected up to 13n. Every spark plug is there a separate high-voltage switch is assigned. Through a parallel to the high voltage switches 13a to 13n, dashed lines Diode 33a to 33n is indicated that the high voltage switch are designed to conduct backwards.

By appropriately controlling the high-voltage switch the energy of the ignition coil 5 distributed to the spark plugs 3a to 3n (electronic). Figure 2 thus shows an ignition device electronic high voltage distribution.

On the secondary side of the ignition coil 5 is on the High voltage output 11 opposite end of the Winding 17 in turn a measuring circuit 19 is provided, whose structure is identical to that in Figure 1 illustrated and explained. It will therefore referred to what has been said for FIG. 1.

On the primary side of the ignition coil 5, a current I _1, on the secondary side of a current I ₂ which is forwarded via the high voltage switches 13a to 13n to the respective spark plug 3a to 3n. The ignition coil 5 is in turn driven by a drive signal 7, referred to as U _ES , of an output stage drive, not shown here, which is connected to the base of the transistor 9. The ignition point is again indicated by a lightning symbol.

The high-voltage switch 13a to 13n is designed here purely by way of example as a light-triggered breakover diode (LKD), which comprises an overhead high-voltage diode 13'a or 13'n and a light-controllable switch 13''a or 13 "n. The light-controllable switch can be via a light signal The light required for switching through is indicated by two wavy arrows, and the current required to generate the light is identified by I _EHV .

Within the high-voltage switch 13a and 13n, the two diodes, i.e. the light-controllable switch and the switch which can be switched overhead, are connected in series, the anode of the switch 13'a / 13'n which can be switched overhead being connected to the spark plug 3a / 3n and the cathode thereof the anode of the light-controllable switch 13''a / 13''n. The cathodes of the light-controllable switches are connected to the high-voltage output 11 of the ignition coil 5 via the connection path 15. In Figure 2 it is indicated that the spark plugs 3a to 3n are driven with a negative potential. As mentioned above, the light-triggered breakover diodes 13a to 13n are designed to be reverse conducting, that is to say they are conductive at a certain positive measuring potential, the charge on the capacitor 25, so that the ion current I _ION given over the spark gap of the spark plugs 3a to 3n can be detected. The measuring voltage used for the ion current measurement is 100 V to 500 V, preferably 200 V to 300 V. This applies to all circuit variations.

FIG. 3 shows an embodiment variant of the one in FIG 2 shown inductive ignition device 1 ' electronic high voltage distribution. The ignition device 1 "in Figure 3 differs only in that the spark plugs 3a to 3n driven with a positive potential via the high voltage output 11 and the connection path 15 via the high voltage switch 13a to 13n is placed on the spark plugs 3a to 3n. The high voltage switches 13a to 13n are again designed as light-triggered breakover diodes (LKD) and each have a light controllable switch 13''a to 13 "n and a high voltage breakover diode, which have an overhead switch 13'a to 13'n. The one shown in Figure 3 Circuit used switches 13a to 13 n lock in reverse.

The polarity of the diodes of the high voltage switch 13a to 13n is the reverse of that shown in FIG Embodiment. The anodes of the light controllable Switches 13''a to 13 "n are therefore located via the connection path 15 at the high voltage output 11, while the cathodes of the overhead switchable Switches 13'a to 13'n on the spark plugs 3a to 3n lie.

However, the measuring circuit 19 'differs from that shown in FIGS. 1 and 2: it includes, for example, a series circuit comprising a resistor 37, a diode 39 and a resistor 41. The resistor 37 is connected to the primary side of the ignition coil 5, specifically here to the Collector of transistor 9. On the other side of resistor 37 is the anode of diode 39, the cathode of which is connected to resistor 41 and capacitor 42. The end of the capacitor 42 opposite the resistor 41, at which the voltage proportional to the ion current I _ION is tapped, is grounded via the resistor 44. At the end of the resistor 41 opposite the capacitor 42 there is a connection point 23 to which the high-voltage switches associated with the spark plugs 3a to 3n, here high-voltage diodes 43a to 43n, are connected, the anodes of which are connected to the connection point 23 and the cathodes of which are connected to the spark gap 3a to 3n are connected, to which the high-voltage switches 13a to 13n are also located. The opposite end of the spark gap of the spark plugs 3a to 3n is grounded.

A positive voltage signal is applied to the spark plugs 3a to 3n via the measuring circuit 19 'in order to detect the ion current I _ION . The polarization of the high-voltage diodes 43a to 43n prevents the high voltage applied to the spark plugs 3a to 3n from reaching the measuring circuit 19 '.

Otherwise, the components correspond to the inductive ones Ignition device 1 "according to FIG. 3 to that in FIG 2 shown embodiment. Same Parts are given the same reference numbers. It In this respect, reference is made to the description of FIG. 2.

FIG. 4 schematically shows the course of the drive voltage U _ES applied to the base of the transistor 9 over time t, including the primary current I ₁ in the ignition coil 5 over time, and also the secondary current I ₂ in the ignition coil 5, which feeds the controlled spark plugs and in a fourth partial diagram the secondary voltage U ₂ applied to the spark plugs over time t. Finally, the last, lowest partial diagram in FIG. 1 indicates the current I _EHV , which is used to control the light-controllable switches 13''a to 13''n mentioned in FIGS. 2 and 3 and thus the electronic high-voltage distribution.

It can be seen from the illustration in FIG. 4 that the control voltage U _ES is present during the so-called closing time up to the time t ₁ and is switched off at the ignition time, which is indicated by a lightning symbol. The primary current I _{1 increases} linearly up to the time t ₁ and then drops suddenly. The secondary current I ₂ remains at zero until the time t ₁ and rises to its maximum value at the time t ₁ . At the same time, the peak for the ignition voltage U ₂ results at the time t ₁ .

The desired spark duration extends over the period t ₁ to time t ₂ . It can be seen from FIG. 4 that the secondary current I ₂ drops essentially linearly during the period t ₁ t t t t ₂ . The high-voltage switches of the inductive ignition devices in FIGS. 1 to 3 can be selected such that the switches switch off at the current value of I ₂ given at time t2, because the so-called holding current of these high-voltage switches is not reached.

The voltage peak of U ₂ causes the high-voltage switch 13 of the inductive ignition device 1 according to FIG. 1, which is designed as an overhead switchable high-voltage breakover diode, to be switched through at time t ₁ , so that the secondary current I _{2 flows} across the spark gap 35 of the spark plug 3, the ignition spark burning. The spark goes out as soon as the high-voltage switch switches off. This can be done by the secondary current falling below the holding current value. The special design of the high-voltage switch can thus ensure that the spark duration is limited. However, the spark duration can also be limited by forcibly switching off the secondary current I ₂ and thereby falling below the holding current value of the high-voltage switch. The secondary current is switched off in that a second control signal A is emitted via the control circuit at time t ₂ , on the basis of which the current I ₁ flows again. The second control signal of the output stage control is maintained for a period of 10 µs to 500 µs. A control signal with a duration of 100 µs has proven particularly useful. During this period t ₂ ≤ t ≤ t ₃ , the current I ₁ rises and falls back to zero. As a result, the current flow I _{2 is} forcibly ended. The current I ₂ thus drops in a defined and inevitable manner to a value which is below the holding current of the high-voltage switch. After a period of time, which is also referred to as the recovery time or release time, of approximately 50 microseconds, a voltage can again be applied to the high-voltage switch in the forward direction.

After the control signal A is switched off at the time t ₃ , the secondary voltage U ₂ rises again briefly and then drops towards zero. There is a rapid, defined reduction in the residual energy in the ignition coil, the voltage U ₂ no longer exceeding the blocking voltage of the high-voltage switch. These therefore remain in their switched-off state, so that the spark plugs no longer ignite.

The voltage and current profiles indicated in FIG. 4 also result for those in FIGS and 3 illustrated inductive ignition systems.

The high-voltage switches 13a to 13n, which are designed as light-triggered breakover diodes, are switched on by activating the light-controllable switches 13''a to 13 "n. In the activated state, the light-triggered switches therefore release the connection between the switches which can be switched overhead and the high-voltage output 11, so that the overhead switches switchable switches 13'a to 13'n can be switched on by the overvoltage U _2. The switch which can be switched overhead is released by a current signal I _EHV which is transmitted to the light-controllable switch 13 '' immediately before the ignition voltage U _{2 occurs} at time t ₁ . a to 13 "n of the spark plug 3a to 3n is applied to which the energy of the ignition coil 5 is to be supplied. By way of example only, it is assumed that the switching signal I _{EHV is present for} 100 μs before and after the time t ₁ at one of the light-switchable switches 13 ″ a to 13 ″ n. It can be seen that for the defined termination of the spark duration no further signal I _{EHV has} to be applied to the light switchable switch. The light-triggerable switches 13a to 13n, or the high-voltage breakover diodes 13'a to 13'n assigned to these switches, are switched off exclusively by the second control signal A applied at time t ₂ , which is shown in the uppermost partial diagram of FIG.

By the signal U _ES Thus, the primary current I ₁ is also in the ignition means, which are shown in Figures 2 and 3, at time t ₂ to rise again, so that there too the secondary current I ₂ is forcibly terminated and -As from Figure 4 evident - drops by approximately 20 mA / 50 µs, so that the spark duration is forcibly ended. Also in the embodiment variants according to FIGS. 2 and 3, the secondary voltage U _{2 will} rise again at time t ₃ when the second control signal U _{ES is switched} off, but without reaching the blocking voltage of the switches 13'a to 13'n which can be switched overhead, and then against Fall off zero. The residual energy in the spark plug is thus rapidly reduced without the spark plugs igniting again.

The circuits shown in FIGS. 1 to 3 are characterized in that the spark duration can be shortened in a targeted manner. On the one hand, this is possible by using high-voltage switches, such as those shown in FIG. 1 or those that have been explained with reference to FIGS. 2 and 3, whose holding current is selected such that the secondary current I ₂ at time t ₂ is switched on because the holding current of the high-voltage switch is undershot.

A significantly reliable function of the circuits is obtained if the secondary current I _{2 is} specifically switched off by a second control signal A, which is generated at time t ₂ and is delivered to the ignition coil. The second control signal at time t ₂ , as described above, leads the secondary current I ₂ down to zero in a defined manner, so that the high-voltage switches are definitely switched off and remain switched off after a certain period of time (recovery time / release time).

Due to the high-voltage switch being switched off, the spark plugs are decoupled from the ignition coil, so that the spark plugs cannot be re-ignited even after the secondary voltage U ₂ rises after time t ₃ .

From these explanations, on the one hand, the function of the inductive ignition devices according to FIGS. 1 to 3 results, on the other hand the method for controlling a spark plug of an internal combustion engine with the aid of an inductive ignition device, which is characterized in that two control signals are generated to implement a defined spark duration of a spark plug become. The first control signal is used to trigger the ignition process at time t ₁ ; the second control signal A emitted at time t ₂ has the purpose of switching off the secondary current in the spark plug in a defined manner and thus limiting the spark duration. It has been shown that the second control signal must be provided for a period of preferably 100 microseconds so that, on the one hand, the recovery time / release time for the high-voltage switch used is observed. On the other hand, the short duration of the second control signal ensures that when the primary current I _{1 is switched off,} the secondary current I ₂ does not rise again at time t ₃ .

Due to the special design of the circuits of Figures 1 to 3 and by the interpretation of The spark plugs can be moved with a measuring current are applied, with measuring circuits 19 and 19 'can be used in the Figures 1 and 2 and 3 shown and have been explained. The measuring current over the spark gap the spark plug flows is evaluated, while the ignition spark is no longer burning. He flows due to the in the combustion chamber during combustion existing ions. With this also as ion current measurement designated method can be the combustion process be monitored. The measuring current lies in a range from 20 µA to 200 µA. Preferably becomes a measuring current of 50 µA to 100 µA chosen. From the explanations to those in the figures 1 and 2 high-voltage switches used clearly that for carrying out the ion current measurement reverse-conducting breakover diodes, i.e. backwards conductive high voltage diodes respectively reverse-conducting, light-triggered breakover diodes be used so that the implementation of the ion current measurement done with relatively little effort can. If, as explained with reference to FIG. 1, Single spark coils are used, it is possible a separate measuring circuit for each spark plug to provide. It is also conceivable, for several, for example four spark plugs, a single measuring circuit to use.

In Figure 3 reverse high-voltage switches used. The one shown in Figure 3 Measuring circuit is also available for arrangements Figure 1 applicable, the high voltage switch 13th according to Figure 1 are then designed to be reverse-locking.

From what has been said above, it can be seen that the ion current measurement is possible in the inductive ignition devices shown in FIGS. 1 to 3 without the voltage supply delivered to the spark plugs or the secondary initial current I ₂ having to be reduced. Due to the defined "shutdown" of the secondary current, a high amount of energy can be delivered to the candles in the ignition coil, so that there is a sufficient supply of voltage and energy under all operating conditions.

By deliberately switching off the high-voltage switches, either by a special specification of the Holding current of the high voltage switch or preferably a second control signal ensures that that there is no increased power loss in the output stage control or the spark plug sets.

By blocking the high-voltage switch, the energy remaining in the ignition coil can swing out with a small time constant without the spark plugs being re-ignited. Finally, by deliberately ending the spark duration, residual energy operation in multi-cylinder engines, for example in engines with more than five cylinders, at high speed and when controlled with only one output stage, can be avoided. For a given energy, a relatively low initial current can be selected for the spark plugs, with a correspondingly long spark duration. The low initial value of the secondary current I ₂ results in a relatively low spark plug wear. This mode of operation can be implemented particularly in connection with an electronic high-voltage distribution, as was explained with reference to FIGS. 2 and 3.

Claims (14)

1. Inductive ignition device (1, 1') for sparkplugs (3, 3a-3n) of an internal combustion engine, having at least one drive circuit (9) for at least one ignition coil (5) and having at least one sparkplug (3), characterized by a high-voltage switch (13; 13a to 13n) which is associated with at least one sparkplug and is changed to a conductive, switched-on state by a first drive signal of the drive circuit, has the spark current (I₂) of the at least one sparkplug (3; 3a to 3n) flowing through it in the switched-on state, and is designed such that, without any further drive, it remains in the conductive state until the spark current becomes less than a specific value (latching current).
2. Ignition device according to Claim 1, characterized in that the drive circuit emits a second drive signal in order to end the spark duration in a defined manner.
3. Ignition device according to Claim 1 or 2, characterized in that the second drive signal is sufficiently short that no renewed secondary current (I₂) is produced, and in that the second drive signal is sufficiently long that the high-voltage switch (13; 13a to 13n) remains in the switched-off state after a recovery time.
4. Ignition device according to Claim 3, characterized in that the time for which the second drive signal is switched on is 10 µs to 500 µs, preferably about 100 µs.
5. Ignition device according to one of the preceding claims, characterized in that the high-voltage switch (13; 13a to 13n) is arranged between the sparkplug (3; 3a to 3n) and a high-voltage output (11) on the secondary side of the ignition coil.
6. Ignition device according to one of the preceding claims, characterized in that the high-voltage switch is designed as a breakover diode, or is designed to be triggerable.
7. Ignition device according to Claim 6, characterized in that the high-voltage switch (13) is designed as a reverse-conducting high-voltage breakover diode.
8. Ignition device according to Claim 6, characterized in that the high-voltage switch (13a to 13n) is designed as a reverse-conducting, light-triggered breakover diode.
9. Ignition device according to one of the preceding claims, characterized by a measurement circuit (19; 19'), which applies a measurement voltage to the sparkplugs (3; 3a to 3n), in order to detect the ion current.
10. Method for driving a sparkplug of an internal combustion engine with the aid of an inductive ignition device, in particular by means of an inductive ignition device according to one of Claims 1 to 9, characterized in that two drive signals are produced in order to provide a defined spark duration for a sparkplug, in which case the first drive signal is used to produce the ignition spark, and the second drive signal is used to switch off the secondary current, and thus to end the spark duration.
11. Method according to Claim 10, characterized in that the second drive signal is used to switch off the high-voltage switch via which the spark current flows to the sparkplug.
12. Method according to Claim 10 or 11, characterized in that the second drive signal is provided for a time period of from 10 µs to 500 µs, preferably of about 100 µs.
13. Method according to one of Claims 10 to 12, characterized in that a measurement voltage is applied to the sparkplugs, in order to monitor the combustion process by means of an ion current measurement.
14. Method according to the preceding Claims 10 to 13, characterized in that a measurement voltage of from 100 V to 500 V, preferably of from 200 V to 300 V, is chosen.

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