Ignition system and method for controlling an ignition system for a spark-ignited internal combustion engine

Abstract

An ignition system and a method for controlling an ignition system for a spark-ignited internal combustion engine are described, having a primary voltage generator for generating an ignition spark and a boost converter for maintaining an ignition spark. The method includes sending a signal from an engine control unit to the ignition system, in order to determine a predetermined ignition timing for triggering an ignition spark, sending an additional signal from the engine control unit to the ignition system, in order to determine a predetermined additional ignition timing for triggering an additional ignition spark, and sending a control signal for influencing the operating mode of the boost converter from the engine control unit to the ignition system between the signal and the additional signal.

Claims

1. A method for controlling an ignition system for a spark-ignited internal combustion engine, having a primary voltage generator for generating an ignition spark and a boost converter for maintaining the ignition spark, the method comprising: transmitting a signal from an engine control unit to the ignition system to determine a predetermined ignition timing for triggering an ignition spark; transmitting an additional signal from the engine control unit to the ignition system to determine a predetermined additional ignition timing for triggering an additional ignition spark; and sending a control signal for influencing an operating mode of the boost converter from the engine control unit to the ignition system between the signal and the additional signal, wherein: each of the signal and the additional signal includes respective sequences of multiple pulses, one specific pulse of the sequence of the signal determines the predetermined ignition timing for triggering the ignition spark, one specific pulse of the sequence of the additional signal determines the predetermined additional ignition timing for triggering the additional ignition spark and between the pulse of the signal and the pulse of the additional signal, the control signal for influencing the operating mode of the boost converter is transmitted in the form of pulses of the signal and in the form of pulses of the additional signal.

2. The method as recited in claim 1, wherein the signal and the control signal are transmitted over an identical channel, the signal and the control signal being sent over an identical electric line.

3. The method as recited in claim 1, wherein the control signal exhibits at least one of: i) a high level identical to that of the signal, and ii) a low level compared to the signal.

4. The method as recited in claim 1, wherein the operating mode of the boost converter is influenced at least one of :i) by a point in time, and ii) by a time duration, of the presence of at least one of a high level and a low level of the control signal.

5. The method as recited in claim 1, wherein the operating mode of the boost converter is influenced by a position of both edges of the control signal.

6. The method as recited in claim 1, wherein the operating mode of the boost converter is influenced by a number of pulses within the control signal.

7. The method as recited in claim 1, wherein the operating mode of the boost converter is influenced by an extent of a high level of the control signal.

8. The method as recited in claim 1, wherein an at least one control signal characterizes at least one of: i) a time delay between a switching-on of the primary voltage generator and a switching-on of the boost converter, ii) a power output of the boost converter, iii) a pulse duty factor of the boost converter, iv) a switching frequency of the boost converter, v) a switch-off instant of the boost converter, and vi) a start of operation of the boost converter for suppressing a switch-on spark by the primary voltage generator.

9. The method as recited in claim 1, wherein additional control signals are sent for influencing additional parameters of the operating mode of the boost converter.

10. The method as recited in claim 9, wherein the additional control signals include at least one of: i) a signal which defines a delay time between a switching-on of the primary voltage generator, in particular, of an ignition transformer current, and a switching-on of the boost converter , ii) a signal which defines a power output of the boost converter, iii) a signal which selects a method for varying the power output of the boost converter, in particular, the use of at least one of a pulse duty factor and a frequency, and iv) a signal which defines a switch-off instant of the boost converter.

11. An ignition system for a spark-ignited internal combustion engine, comprising: a primary voltage generator for generating an ignition spark; a boost converter for maintaining the ignition spark; an evaluation unit; and a signal input, wherein: the evaluation unit is configured to receive, via the signal input, a signal from an engine control unit for determining a predetermined ignition timing for triggering an ignition spark, and an additional signal from an engine control unit for determining an additional predetermined ignition timing for triggering an additional ignition spark, and wherein the evaluation unit is further configured to receive and to evaluate a control signal from the engine control unit for influencing the operating mode of the boost converter between the signals, each of the signal and the additional signal includes respective sequences of multiple pulses, one specific pulse of the sequence of the signal determines the predetermined ignition timing for triggering the ignition spark, one specific pulse of the sequence of the additional signal determines the additional predetermined ignition timing for triggering the additional ignition spark and between the pulse of the signal and the pulse of the additional signal, the control signal for influencing the operating mode of the boost converter is transmitted in the form of pulses of the signal and in the form of pulses of the additional signal.

12. An engine control unit for controlling an ignition system for a spark-ignited internal combustion engine, having a primary voltage generator for generating an ignition spark and a boost converter for maintaining the ignition spark, which is configured to send via a signal output, a signal to the ignition system for determining a predetermined ignition timing for triggering an ignition spark, and to send an additional signal to the ignition system for determining an additional predetermined ignition timing for triggering an additional ignition spark, wherein the engine control unit is further configured to send via the signal output a control signal to the ignition system for influencing the operating mode of the boost converter between the signal and the additional signal, wherein each of the signal and the additional signal includes respective sequences of multiple pulses, wherein one specific pulse of the sequence of the signal determines the predetermined ignition timing for triggering the ignition spark, wherein one specific pulse of the sequence of the additional signal determines the additional predetermined ignition timing for triggering the additional ignition spark and wherein, between the pulse of the signal and the pulse of the additional signal, the control signal for influencing the operating mode of the boost converter is transmitted in the form of pulses of the signal and in the form of pulses of the additional signal.

13. A system, including an engine control unit for controlling an ignition system for a spark-ignited internal combustion engine, having a primary voltage generator for generating an ignition spark and a boost converter for maintaining the ignition spark, which is configured to send via a signal output, a signal to the ignition system for determining a predetermined ignition timing for triggering an ignition spark, and to send an additional signal to the ignition system for determining an additional predetermined ignition timing for triggering an additional ignition spark, wherein the engine control unit is further configured to send via the signal output a control signal to the ignition system for influencing the operating mode of the boost converter between the signal and the additional signal, a signal output of the engine control unit being connected to a signal input of the ignition system, wherein each of the signal and the additional signal includes respective sequences of multiple pulses, wherein one specific pulse of the sequence of the signal determines the predetermined ignition timing for triggering the ignition spark, wherein one specific pulse of the sequence of the additional signal determines the additional predetermined ignition timing for triggering the additional ignition spark and wherein, between the pulse of the signal and the pulse of the additional signal, the control signal for influencing the operating mode of the boost converter is transmitted in the form of pulses of the signal and in the form of pulses of the additional signal.

Description

BRIEF DESCRIPTION OF THE DRAWINGS

(1) Exemplary embodiments of the present invention are described in detail below with reference to the figures.

(2) FIG. 1 shows a circuit diagram according to a first exemplary embodiment of an ignition system according to the present invention.

(3) FIG. 2 shows a time diagram of signals and control signals during the operation of an exemplary embodiment of a system according to the present invention when carrying out an exemplary embodiment of a method according to the present invention.

(4) FIG. 3 shows an illustration of an influence of an increased burn voltage on the required power level of an ignition system designed according to the present invention.

(5) FIG. 4 shows a flow chart illustrating steps of one exemplary embodiment of a method according to the present invention.

DETAILED DESCRIPTION OF EXAMPLE EMBODIMENTS

(6) FIG. 1 shows a circuit of an ignition system 1, which includes a step-up transformer 2 as a high voltage generator, the primary side 3 of which may be supplied with electrical power from an electrical energy source 5 via a first switch 30. Secondary side 4 of step-up transformer 2 is supplied with electrical power via an inductive coupling of primary coil 8 and secondary coil 9, and includes a conventional diode 23 for suppressing a switch-on spark, this diode 23 being alternatively replaceable by diode 21. A spark gap 6 is provided in a loop with secondary coil 9 and diode 23 to ground 14, via which the ignition current i.sub.2 is intended to ignite the combustible gas mixture. According to the present invention, a boost converter 7 is provided between electrical energy source 5 and secondary side 4 of step-up transformer 2. For this purpose, an inductance 15 is connected via a switch 22 and a diode 16 to a capacitance 10, the one end of which is connected to secondary coil 9 and the other end of which is connected to electrical ground 14. The inductance in this case serves as an energy store in order to maintain a current flow. Diode 16 is conductively oriented in the direction of capacitance 10. A shunt 19 is provided as a current measuring means or voltage measuring means between capacitance 10 and secondary coil 9, the measuring signal of which is fed to switch 22 and to switch 27. In this way, switches 22, 27 are configured to respond to a defined range of current intensity i.sub.2 through secondary coil 9. Switches 22 and 27 are connected to each other at node 35. The terminal of switch 22 facing diode 16 is connectable via an additional switch 27 to electrical ground 14. To protect capacitance 10, a Zener diode 21 is connected in the reverse direction in parallel to capacitance 10. In addition, switch signals 28, 29 are indicated, with the aid of which switches 22, 27 may be controlled. Whereas switch signal 28 represents a switching-on and remaining closed for an entire ignition cycle, switch signal 29 outlines a concurrent alternating signal between closed and open. With switch 22 closed, inductance 15 is supplied with a current via electrical energy source 5, which flows directly to electrical ground 14 when switches 22, 27 are closed. With switch 27 opened, the current is conducted to capacitor 10 via diode 16. The voltage arising in response to the current in capacitor 10 is added to the voltage dropping over secondary coil 9 of step-up transformer 2, as a result of which the arc at spark gap 6 is supported. Capacitor 10 discharges in the process, however, so that by closing switch 27, power may be brought into the magnetic field of inductance 15 in order to charge capacitor 10 again with this power when switch 27 is opened again. Control 31 of switch 30 provided in primary side 3 is recognizably kept significantly shorter than is the case for switches 22 and 27, Switch 2Z since it assumes no crucial function for the processes according to the present invention, hut rather merely switches the circuit on and off, is merely optional and may therefore be omitted. An engine control unit 40 including a signal output 44 is also depicted, via which signals identified by S.sub.CEI for determining a predetermined ignition timing for triggering an ignition spark, and control signals for influencing according to the present invention the operating mode of boost converter 7, are transmitted to an evaluation unit 42 equipped with a signal input 43. In this way, engine control unit 40 may influence extensively the switch states of primary voltage generator 2 and of boost converter 7.

(7) FIG. 2 shows time characteristics of a signal S.sub.CEI transmitted from an engine control unit to an ignition system according to the present invention for three different desired power outputs of the boost converter (P1, P2, P3). Depicted among these is switch-on signal S.sub.HSS of the boost converter, which results from the time characteristics depicted above it. The time characteristic of a current I.sub.1 through the primary side of the ignition coil of the high voltage generator, spark current I.sub.2 and an output voltage U.sub.HSS of the boost converter are also plotted over time. In the example, a delay time is defined by the duration of control signal t.sub.1, which elapses between the switching-on of an ignition transformer current (current I.sub.1 through the primary side of the primary voltage generator) and the switching-on of the boost converter. Since the voltage of the boost converter on the output side only gradually approaches a stationary voltage level, it is possible in this way, for example, to control the level of the power supply at the spark gap in the ignition timing. The power level of the boost converter on the output side is recognizably controlled by the duration of control signal t.sub.2 exhibiting a low level, in response to which spark current I.sub.2 assumes three different time characteristics after the ignition timing. In this case, idealized combustion chamber conditions and an initially constant spark combustion voltage are assumed. The duration of the energization of the ignition transformer is established via time duration t.sub.3, reduced by time duration t.sub.6. In other words, the closing time (ignition timing) of the ignition transformer is established. The position of the falling edge of control signal t.sub.3, in particular, thus defines the position of the ignition timing over the crankshaft angle. The low level of control signal t.sub.4 may be used to control different parameters of the ignition system or of the boost converter. For example, a type of power output variation method for the boost converter may be predefined via the duration of control signal t.sub.4. For example, a switch frequency and/or a pulse duty factor of the boost converter may be selected or adapted as a function of the duration. Finally, the switch-off instant of the boost converter is determined via switch signal t.sub.5 and, in particular, its falling edge t.sub.5. After this point in time, spark current I.sub.2 recognizably drops off quickly until the ignition spark breaks off. The rising edge between control signals t.sub.2 and t.sub.3 recognizably optionally also defines the starting point of a switch operation of the boost converter for a duration ?, via which a voltage overshoot of the ignition system on the output side is avoided, by operating the boost converter for a duration ? until a predefined voltage threshold value U.sub.HSSmax is reached. Voltage U.sub.HSS of the boost converter drops drastically the moment current I.sub.1 on the primary side is switched on. The voltage at the spark gap, however, remains in a range in which an undesirable ignition is unable to take place. In the example, the power levels of the boost converter are selected at 50%, 75% and 100%. One possibility of reducing undesirable interferences due to an electromagnetic excitation of the surroundings of the ignition system according to the present invention is to adapt the frequency range of the boost converter via signal t.sub.4. With a suitable selection or dimensioning of control signals t.sub.1 through t.sub.6, it is also possible to implement a single-spark operation (without the operation of the boost converter) by controlling a mixture ignition under combustion chamber conditions, which necessitate a low power requirement for generating an ignition spark.

(8) Control signals t.sub.1 and/or t.sub.2 may, for example, be used for a corresponding control. If a single-spark operation is used for the targeted discharging of a residual voltage remaining at the spark gap, a control signal may be used in order to generate a conductive spark gap for discharging the spark gap in the absence of an ignitable mixture in the combustion chamber. This may take place, for example, by selecting a control signal t.sub.1 within a range of predefined limits, upon receipt of which the ignition system recognizes that control signal t.sub.1 lies outside the predefined interval. In response to such an input value, the ignition system generates a discharge spark at a point in time in which no ignitable mixture is present in the combustion chamber, as a result of which a residual energy remaining in the ignition system is dissipated without causing damage to the internal combustion engine. A single-spark operation or a quenched spark, for example, may also be generated by control signals t.sub.2, which are not predefined for power levels of the boost converter. In other words, a value of t.sub.2 invalid for the power position is taken by the ignition system as a signal for starting the single-spark operation or for generating a quenched spark. The ignition system is operated, in principle, in accordance with a conventional inductive ignition coil. This means, the ignition coil is supplied once with power via the energization of the primary side, and the power is used to build up a high voltage and after ignition, the stored magnetic energy remaining in the inductance of the voltage generator is delivered to the spark gap.

(9) FIG. 3 illustrates the required power levels of the boost converter as a function of a spark burning voltage U.sub.burn. The spark burning voltage U.sub.burn is plotted rising essentially linearly over time. At a power level of the boost converter of 50%, the spark current I.sub.fu50 drops sharply until it reaches a minimum value I.sub.min. In response thereto, a control signal according to the present invention causes the power level of the boost converter to increase to 75%, as a result of which the resulting spark current I.sub.fu75 jumps into a stable range. A further increase of the spark burning voltage U.sub.burn again results in a reduction of the current to the minimum value of the current I.sub.min, in response to which a control signal according to the present invention to the ignition system sets the power level of the boost converter to 100%, in response to which the spark current I.sub.fu100 again jumps to a stable value.

(10) FIG. 4 shows steps of an exemplary embodiment of a method according to the present invention for controlling an ignition system for a spark-ignited internal combustion engine having a primary voltage generator for generating an ignition spark and a boost converter for maintaining the ignition spark. In step 100, the method starts by transmitting a signal from an engine control unit to the ignition system, the signal determining a predetermined ignition timing for triggering a first ignition spark. In step 200, a control signal for influencing the operating mode of the boost converter is transmitted from the engine control unit to the ignition system. For example, a piece of information for overlapping the operating mode of the primary voltage generator and the boost converter, a power level to be used and a switch-on spark-suppression function may be communicated. Numerous additional possibilities for the operating parameters to be influenced according to the present invention have been cited above. In step 300, an additional signal is transmitted from the engine control unit to the ignition system, with which a predetermined additional ignition timing for triggering an ignition spark is determined. In this way, the operation of an ignition system including a primary voltage generator and a high voltage generator may be easily controlled and the ignition system itself may be simply designed.

(11) Even though the aspects according to the present invention and advantageous specific embodiments have been described in detail with reference to the exemplary embodiments explained in conjunction with the figures, modifications and combinations of features of the depicted exemplary embodiments are possible for those skilled in the art, without departing from the scope of the present invention.