Abstract:
The invention relates to a device for controlling a multiple spark operation of an internal combustion engine, wherein an ignition transformer can be switched off and back on again for delivering or interrupting an ignition spark energy based on at least one current threshold. The invention proposes that the at least one current threshold be programmable.

Description:
This application is a National Stage Application of PCT/EP2008/062094, filed 11 Sep. 2008, which claims benefit of Serial No. 10 2007 051 249.1, filed 26 Oct. 2007 in Germany and which applications are incorporated herein by reference. To the extent appropriate, a claim of priority is made to each of the above disclosed applications. 
     BACKGROUND 
     A device and a procedure for regulating a multiple spark operation of a combustion engine of the type that is mentioned above are generally known. In order to ensure a secure ignition of a mixture of fuel and air in all operating points of the combustion engine further ignition sparks are created in the same ignition cycle in the sense of a multiple ignition with the aid of an ignition plug in some operating statuses, such as during a starting phase, by turning back on an ignition transformer immediately after one ignition spark dies. With the aid of a device a controlling of the multiple spark ignition takes place. 
     Further solutions are known, which improve the multiple spark operation—also called multiple spark mode. Thereby a primary inductance that is located in the primary current circuit of the transformer is reloaded already before igniting the ignition spark. Due to a still existing residual energy in the ignition transformer a recharging time of the primary inductance is significantly reduced. In this context it can be profited from an effect, at which a significant part of the ignition spark energy that is created by the transformer is transformed at the beginning of each ignition spark, thus if the ignition spark current is the highest, whereby it subsequently sinks almost linearly. By doing so several ignition sparks of short duration but comparably high energy can be created during an ignition cycle. The device provides thereby merely the total duration of the multiple spark operation, while a regulator electronic takes over a regulation of the multiple spark operation, thus a series of consecutive ignition sparks. The regulator electronic is usually located together with the ignition transformer in a common housing. 
     Typically firm threshold values are stored in the regulator electronic for a primary current and for a secondary current, at which the ignition transformer is turned off and back on. But there are several influencing factors, such as the composition of a fuel air mixture, ignition plug ageing and such alike, which complicate an optimal operation of the combustion engine at specified threshold values. 
     SUMMARY 
     According to the invention for regulating a multiple spark operation of a combustion engine, an individual adjustment of the threshold values, in particular the current thresholds, can be carried out for the primary current and/or for the secondary current depending on the operating status of the combustion engine. Thereby a programming of at least one current threshold takes place. The individual adjustment of the current thresholds enables therefore a demand-oriented adjustment of the follow-up current thresholds of the multiple spark operation in each single cylinder or work cycle of the combustion engine. 
     With the aid of the individual adjustment of the current threshold and the corresponding demand-oriented adjustment of the follow-up current thresholds of the multiple spark operation influencing factors, as for example the mixture composition, ignition plug ageing and such alike, which complicate the optimal operation of the combustion engine, can therefore be considered and compensated at ignition processes. With other words the feed of ignition energy to an ignition plug can be adjusted to the demand of the corresponding operating and load status of the combustion engine. 
     Lastly the present invention does not only ensure an improved fuel ignition but also a reliable operation of the combustion engine. Additionally the improved fuel ignition has a positive effect on a fuel consumption of the combustion engine on the one hand and on a power request of the combustion engine on the other hand. The same applies analogously for the procedure for regulating the multiple spark operation of a combustion engine. 
     According to a preferred embodiment of the invention it is provided that an adjustment of the at least one current threshold takes place depending on a transformer current, in particular a primary current and/or secondary current, that can be detected with a detection device or measured. An individual adjustment of the thresholds can thereby take place with the aid of a control unit in such a way that they are brought into accordance with the optimal thresholds, which are known for each operating status and stored in the control unit. Ultimately the multiple spark operation is enabled by this means, in particular including the adjusted thresholds. 
     It is provided in an advantageous embodiment of the invention that a transmission of the default value for a follow-up current threshold takes place from a control unit to a regulator electronic of the ignition transformer with the aid of an encoded interval between a first control signal that is emitted by a control unit and a second control signal that is emitted by the control unit. By means of the coding of the interval or the pause time between the two control signals of the control unit an information that qualifies for the ignition transformer can be transmitted over a provided current threshold 
     It is provided in a further advantageous embodiment of the invention that the transmission of the default value for the follow-up current threshold, in particular the secondary current switch-off threshold, takes place by means of the duration of the interval. The duration of the interval or the pause time between the two control signals of the control unit represents a signal gap, which is present anyway and which can be used by a targeted and scheduled change to a value association. Thus an interval of for example 30 μs can be associated with a secondary current switch-off threshold of 70 mA or an interval of 160 μs with secondary current switch-off threshold of 40 mA. 
     According to a preferred embodiment of the invention it is provided that the transmission of the default value takes place by means of the duration of the interval in combination with a further default value for a corresponding follow-up current threshold, in particular a primary current switch-off threshold, which is based on an additional current threshold. That results in a synergy effect, at which a value combination can be transmitted for the secondary current switch-off threshold as well as for the primary current switch-off threshold by means of only one parameter namely the interval. 
     According to a preferred embodiment of the invention it is provided that the transmission of the default value takes place in connection with a current threshold difference value over the duration of the interval. With other words a value delta is thereby transmitted over the pulse pause, which lowers the corresponding current threshold at a longer pulse pause for example by 10 mA. At a short pulse pause the corresponding current threshold can be raised with the aid of the value delta for example by 10 mA. A constellation can also be provided, at which an average pulse pause causes no change of the relevant current threshold. 
     It is provided in a preferred embodiment of the invention that a bidirectional interface is provided between the control unit and the ignition transformer, in particular for transmitting a spark burning time. A feedback of information of the ignition transformer can thereby take place by a switchover of a control current. The control current during the spark burning time can for example correspond with a value of 20 mA and during the loading phase with a value of 10 mA. The control unit is then able to determine the spark burning time over the current and increases or reduces the secondary current threshold depending on the required spark burning time. Ultimately an erroneous interpretation of present pulse pauses, in particular during the transmission of current threshold difference values, can be thereby avoided. Furthermore it is ensured that the information in the control unit and in the ignition transformer always correspond, whereby an error is not carried along in each further ignition cycle. 
     It is provided in a further advantageous embodiment of the invention that the transmission of the default value and/or the further default value takes place with the aid of a protocol that contains current threshold values over the duration of the interval. The protocol comprises thereby rules, which determine the format, the contents, the meaning and the order of sent information between different instances, in particular between the regulator electronic that is located in the ignition transformer and the ignition transformer itself or between the control unit and the regulator electronic. 
     According to a preferred embodiment of the invention it is provided that a detection of an amplitude value of a first primary current pulse takes place for adjusting the at least one current threshold, in particular the primary current switch-off threshold. The amplitude of the first primary current pulse is therefore used to adjust or program the primary current threshold. The amplitude value of the first pulse corresponds thereby with the current threshold for all subsequent pulses. Alternatively the current threshold can be increased or reduced by a firm factor. 
     According to a preferred embodiment of the invention it is provided that the transmission of the default value of the secondary current switch-off threshold takes place over the duration of the interval during the detection of the amplitude value of the first primary current pulse for adjusting the primary current switch-off threshold. The amplitude value is thereby used as default for all further primary current switch-off thresholds and simultaneously transmitted over the pause of the secondary current threshold. Advantageous is also an embodiment of the invention, which provides that the transmission of a combination of the secondary current switch-off threshold and primary current switch-off threshold takes place with the amplitude respecting the amplitude value of the first primary current. Thereby a firm value combination results from the threshold value, whereby the pause remains disregarded. An amplitude of 15 A can for example be associated with a value combination of 15 A for the primary current switch-off threshold and of 40 mA for the secondary current switch-off threshold. Furthermore the switch-off threshold for the primary current can lie at 16 A and the switch-off threshold for the secondary current at 50 mA at an amplitude of 16 A. at a switch-off threshold of 17 A for the primary current and a switch-off threshold of 60 mA for the secondary current the amplitude can have a value of 17 A. 
     It is provided in an advantageous embodiment of the invention that the control unit adjusts the duration of the interval depending on the operating status of the combustion engine, whereby a measurement and storage of the upcoming secondary current value takes place at the end of the interval, which serves as default value of the corresponding follow-up current threshold, in particular the secondary current threshold, whereby a further alternative to the previously mentioned value defaults is given. 
     It is provided in a further advantageous embodiment of the invention that the transmission of the default value and/or the further default value takes place over the duration of the second control signal with the aid of a protocol that contains current threshold values or with the aid of a value signal that contains the current threshold values, in particular a pulse width modulated value signal. For transmitting the corresponding information during the multiple spark phase a protocol has to be provided that is suitable for single-wire interfaces or also a suitable pulse width modulated signal. In order to avoid an undesired switching on or switching off of the ignition transformer due to the information transmission very short pauses can be used, which can be preferably filtered for a standard function. The sent information are processed for this case not until the next ignition cycle. 
    
    
     
       BRIEF DESCRIPTION OF THE DRAWINGS 
       The invention as well as advantageous embodiments according to the characteristics of the further claims are subsequently further explained with the aid of the embodiments that are illustrated in the drawings, without a limitation of the invention; it comprises furthermore all variations, changes and equivalents, which are possible within the scope of the claims. It is shown in: 
         FIG. 1  a diagram with a control signal course, in particular the course of a control voltage, as well as with a primary current course and with a secondary current course, at which the adjustment of the secondary current switch-off threshold takes place over a short pulse pause; 
         FIG. 2  a further diagram with a control signal course, in particular the course of a control voltage, as well as with a primary current course and with a secondary current course, at which the adjustment of the secondary current switch-off threshold takes place over a long pulse pause; 
         FIG. 3  a diagram with a control signal course, in particular a course of a control voltage, and with a course of a control current as well as with a primary current course and with a secondary current course, at which a change of the control current takes place by a regulator electronic of an ignition transformers depending on the operating status of the transformer (reloading=20 mA and unloading (ignition spark)=10 mA); 
         FIG. 4  a diagram with a control signal course, in particular a course of a control voltage, as well as with a primary current course and with a secondary current course, at which the adjustment of a primary and secondary current switch-off threshold, in particular with the aid of a switch-off threshold value pair takes place over a short pulse pause; 
         FIG. 5  a further diagram with a control signal course, in particular a course of a control voltage, as well as with a primary current course and with a secondary current course, at which the adjustment of a primary and secondary current switch-off threshold, in particular with the aid of a switch-off threshold value pair takes place over a long pulse pause; and 
         FIG. 6  a diagram with a control signal course, in particular a course of a control voltage, as well as with a primary current course and with a secondary current course, at which an information transmission takes place for adjusting the current switch-off thresholds during a multiple spark phase. 
         FIG. 7  shows an ignition control unit  78  connected to a control unit  80 , a primary side coil  72  connected to the ignition control unit  78  and also to a power supply  70 , and a secondary side coil  76  connected to a spark plug  74 . 
     
    
    
     DETAILED DESCRIPTION 
       FIG. 1  shows a diagram  10 , which comprises the course of a control voltage  11 , the course of a primary current  12  as well as the course of a secondary current  13 . At a multiple spark system of the present type a control unit typically sends out a first pulse  14  and a second pulse  15  at the use of a single-wire interface in an ignition cycle. The first pulse  14  corresponds with a conventional transistor coil ignition, whereby the control unit provides a loading time as well as an ignition time. The second pulse  15  provides the duration of a multiple spark phase. There is a pulse pause  16  or also an interval between the two pulses  14 ,  15 —also called control signals, which is relatively short according to  FIG. 1  and which serves for programming at least one of the current thresholds. As long as the pause time  16  is encoded between the two pulses  14 ,  15  that are sent out by the control unit, information or data values, such as values of a secondary current threshold  17 , can be transmitted over the pulse pause  16  to the ignition transformer, in particular ignition coil. The encoding can thereby take place by different variants. 
     According to  FIG. 1  a transmission of values of the secondary current switch-off threshold  17  takes place over the duration or length of the pulse pause  16 . In the present embodiment the pulse pause  16  has a value of 10 μs and corresponds therefore with a secondary current switch-off threshold  17  of 80 mA, which is equivalent to a high switch-off current. Besides the secondary current switch-off threshold  17  there is a primary current switch-off threshold  18 . At additional pairs of values the pulse duration  16  provides values of 30 μs, 60 μs, 100 μs or 160 μs, while the secondary current switch-off threshold  17  is set to values of 70 mA, 60 mA, 50 mA or 40 mA. According to  FIG. 2  or according to a corresponding diagram  20  the secondary current switch-off threshold  17  corresponds with the lastly mentioned value of 40 mA of the pulse pause  16  at 160 μs, which mirrors a low switch-off current at a comparably long pulse pause. Apart from that the diagram according to  FIG. 2  corresponds with the diagram according to  FIG. 1  and provides also the course of the control signal  11 , the course of the primary current  12  with a corresponding primary current switch-off threshold  18  as well as the course of the secondary current  13 . 
       FIG. 3  shows a diagram  30 , which describes the course of the control voltage  11 , the course of the control current  19  as well as the course of the primary current  12  and the course of the secondary current  13 . A current threshold difference value or also a value delta is thereby transmitted over the pulse pause  16 . A long pulse pause means in that context a sinking of the current threshold by 10 mA. A short pulse pause causes an increase of the current threshold by 10 mA. In order to avoid an erroneous interpretation of present pulse pauses, in particular at the transmission of current threshold difference values, a bidirectional interface can be provided between the control unit and ignition transformer. A feedback of information of the ignition transformer can thereby take place by a switchover of a control current. The control current  19  can for example correspond with a value  21  of 20 mA during a spark burning time and with a value  22  of 10 mA during a reloading phase. The control unit is able to determine the spark burning time over the current and increases or reduces the secondary current threshold depending on the required spark burning time. It is thereby ensured that the information in the control unit and in the ignition transformer do always correspond with each other, whereby an error is not carried along into every further ignition cycle. 
       FIG. 4  shows a diagram  40 , which illustrates the course of the control voltage  11 , the course of the primary current  12  as well as the course of the secondary current  13 . Thereby a combination of values from the secondary current switch-off threshold  17  and the primary current switch-off threshold  18  are transmitted over the duration of the pulse pause  16 . The duration of the pulse pause  16  of 160 μs corresponds thereby with 50 mA for the secondary current switch-off threshold  17 , and  17 A for the primary current switch-off threshold  18 . According to  FIG. 5 , whose diagram  50  also provides the course of the control current  11 , the course of the primary current  12  and the course of the secondary current  13 , the duration of the pulse pause is 100 μs, so that a value of 50 mA is associated to the secondary current switch-off threshold  17  and a value of 15 A to the primary current switch-off threshold  18 . Further associations provide a current threshold relation of 70 mA to 17 A for a pulse pause of 60 μs and a current threshold relation of 70 mA to 15 A at a pulse pause of 30 μs for the secondary current switch-off threshold  17  or for the primary current switch-off threshold  18 . 
       FIG. 6  shows a diagram  60 , which comprises the course of the control voltage  11  as well as the course of the primary current  12  and the course of the secondary current  13 . The transmission of the information about the current thresholds takes thereby place during the multiple spark phase, thus during the second pulse  15 . For the transmission of the information and values a protocol can be used that is suitable for single-wire interfaces. The multiple spark phase or its signal course are thereby the basis for a programming of the current thresholds. Alternatively also a pulse width modulated signal can be used. In order to avoid an undesired switching on or switching off of the ignition transformer due to the information transmission during the multiple spark phase, preferably very short pulses  15 . 1  to  15 . 4  are used, which can be filtered for a standard function. The sent information are processed for that case not unit the next ignition cycle, since the multiple spark phase or its signals themselves serve as information carriers.