Abstract:
The invention relates to a method and a device for triggering at least on firing element for restraining means in a motor vehicle. In said method and device a firing command is transmitted from a control unit to a firing device for the firing elements. The firing command is subsequently repeatedly n-fold, whereby n is at least equal to 1. The n+1 transmitted firing commmands are evaluated in the firing device and once the last of the n+1 firing commands has been transmitted, the firing elements are triggered.

Description:
CLAIM OF PRIORITY 
     This application claims priority to International Application No. PCT/DE01/01162 which was published in the German language on Oct. 4, 2001. 
    
    
     TECHNICAL FIELD OF THE INVENTION 
     The invention relates to a method and a device for firing at least one firing element for a restraining device in a motor vehicle. 
     BACKGROUND OF THE INVENTION 
     Arrangements for firing a restraining device in a motor vehicle usually have a sensor for detecting an accident, a control device which is connected downstream of the sensor, the firing device which is arranged spatially separated from the control device and is connected to it via a line, and at least one firing element (for example a firing cap) for the restraining device, the firing element being electrically connected to the firing device. 
     If, for example, a plurality of firing caps are to be fired simultaneously in such a context using a firing command, but not all the firing caps detect the first firing command and/or fire, the transmission link which is usually embodied as a firing bus between the control device and the firing device may, under certain circumstances, be disrupted to such an extent that no further firing commands can be transmitted. This is the case, for example, if a short circuit or an interruption at the bus occurs as a result of individual undesired detonations. It is then no longer possible to fire the remaining firing caps since no further firing command can be transmitted. 
     SUMMARY OF THE INVENTION 
     The invention discloses a method and an arrangement for firing at least one firing element for a restraining device in a motor vehicle which provides a higher degree of immunity to faults. 
     In one embodiment of the invention, there are firing commands as the first to be transmitted repeatedly (for example 3 times), for firing to be delayed during this time, and for firing of the firing elements, for example by means of the first firing command, to be permitted after the multiple transmission. 
     In the embodiment, there is a method in which a firing command is transmitted, and then the firing command is transmitted n times, from a control device to a firing device for the firing element/elements, n being at least equal to 1. Then, the n+1 transmitted firing commands are evaluated in the firing device and the firing element or elements is/are fired by the firing device after the transmission of the last n+1, for example by the first firing command. 
     In one aspect of the invention, the firing actuation of the firing elements is preferably repeated at least once or, for the sake of simplicity, coupled to the number of transmitter firing commands in order to fire firing elements which have erroneously not yet been fired. Moreover, in addition to simultaneous firing of the plurality of firing elements, it is also possible to provide for the chronologically offset firing of the firing elements so that the firing elements are fired in succession. 
     In another embodiment of the invention, there is a device including a control device for generating n+1 identical firing commands, a firing device for firing the at least one firing element by connecting the firing signal to the firing element, and a transmission device for the transmission of the firing commands by the control device to the firing device. The firing element is not fired by the firing device until after the transmission of the last of the n+1 firing commands, for example by the first firing command. 
     In one aspect of the invention, in order to ensure that the firing of the firing element or elements takes place after the last of the n+1 firing commands has been transmitted, with the control device a delay device is provided for delaying the firing signal, the delay device being fired by the first firing command and having a delay which is longer than the time which is necessary for the transmission of the firing commands. The use of a delay device makes it possible for the firing element or elements to be operated in such a way that firing cannot disrupt the transmission of the firing commands and/or said firing elements are not made to fire until the firing signal has been repeated several times. 
     In another aspect of the invention, in order to be able to increase the immunity to faults further, the firing commands in the control device can be encoded and transmitted to the firing device in encoded form. The firing device contains a firing command decoder in order to decode the firing commands and to generate the firing signals for the firing elements from them. 
     In still another aspect of the invention, it is possible to provide for a plurality of firing elements to be fired in succession by the firing device in order to bring about more uniform loading of the power supply for the firing elements. 
    
    
     BRIEF DESCRIPTION OF THE DRAWINGS 
     The invention is explained in more detail below with reference to the exemplary embodiments illustrated in the figures of the drawing, in which: 
     FIG. 1 shows an exemplary embodiment of a device according to the invention for simultaneously firing a plurality of firing elements. 
     FIG. 2 shows an exemplary embodiment of a device according to the invention for firing a plurality of firing elements with staggered timing. 
     FIG. 3 shows an exemplary embodiment of a device according to the invention for firing a plurality of firing elements with staggered timing. 
    
    
     DETAILED DESCRIPTION OF THE PREFERRED EMBODIMENTS 
     In the exemplary embodiment shown in FIG. 1, an impact sensor  1  is provided, downstream of which impact sensor  1  a control device  2  for evaluating the signals supplied by the impact sensor  1  is connected. In the event of an impact, this is signalled to the control device  2  by means of appropriate signals of the sensor  1 , in response to which the control device  2  transmits, for example, three firing commands  3  to a firing device  5  via a line  4 . These firing commands  3  are identified by the firing device  5 . After a specific number of identical firing commands  3  (for example, a number of firing commands  3  transmitted in total corresponding to the firing command in the exemplary embodiment), three firing caps  6 ,  7 ,  8  which are provided as firing elements then being fired by the firing device  5 . For this purpose, a firing signal (current, voltage) of sufficient strength is applied to the firing caps  6 ,  7 ,  8  when the first delayed firing command occurs. The firing caps are supplied a supply voltage source (not illustrated) with a reference potential  10  and a supply potential  11 . In order to prevent voltage dips in the supply voltage source when the firing caps  6 ,  7 ,  8  are fired, a buffer capacitor  9  is also connected between the reference potential  10  and the supply potential  11 . 
     The firing device  5  includes a decoding device  12  which decodes the firing commands  3  which are encoded by the control device  2  by means of a coding device  13 . A delay device  14 , which delays the firing commands  3  until the firing commands  3  have been transmitted from the control device  2  to the firing device  5 , is connected downstream of the decoding device  12 . 
     This means that the firing command which is first transmitted appears at the output of the delay device  14  when the last of the firing commands  3  has already been transmitted from the control device  2  to the firing device  5 . 
     The output of the delay device  14  controls the base terminals of three transistors  15 ,  16 ,  17  whose emitter-collector paths are connected in series with the firing caps  6 ,  7 ,  8  between the reference potential  10  and the supply potential  11 . When the corresponding number of firing commands occurs, the first firing signal which is delayed by the delay device  14  is therefore made available by the decoding device. The delayed signal then connects through the transistors  15 ,  16  and  17 , as a result of which the latter make available a firing signal for the firing caps  6 ,  7 ,  8 . In this case, the firing caps  6 ,  7 ,  8  are connected to the supply voltage source, as a result of which the latter fire essentially simultaneously. 
     However, it is also alternatively possible to provide for the delay device to be switched upstream of the decoding device and for the latter to control the output of the decoding device  12  directly. This means that the firing commands  3  arrive at the decoding device  12  with delay and then the transistors  15 ,  16 ,  17  connect the firing caps  6 ,  7 ,  8  to the high voltage source. 
     Furthermore, the decoding device and the delay device may be constructed such that the transistors  15 ,  16  and  17  are connected through corresponding to each of the firing commands  3 , the firing caps  6 ,  7 ,  8  not being able to be connected through by means of a firing command alone (power of an individual firing signal is too low) and being fired only after a plurality of firing signals (corresponding to the firing commands  3  which follow one another at short time intervals. 
     The exemplary embodiment shown in FIG. 2 is modified in comparison with the exemplary embodiment according to FIG. 1 in that a firing device  18  is used instead of the firing device  5 . The firing device  18  comprises three decoding devices  19   a ,  19   b ,  19   c  which receive the firing commands  3  from the control device  2  via the line  4 . The decoding devices  19   a ,  19   b ,  19   c  each have delay devices  20 ,  21 ,  22  connected downstream of them, the inputs of the delay devices  20 ,  21 ,  22  each being connected to the output of one of the decoding devices  19   a ,  19   b ,  19   c . The delay devices  20 ,  21 ,  22  have different delays from one another, each of the delays being longer than the time which is required for the transmission of the three firing commands  3  from the control device  2  to the firing device  18 . The delay devices  20 ,  21 ,  22  are each followed by a transistor  23 ,  24 ,  25  for connecting the firing caps  6 ,  7 ,  8  to the supply voltage. Owing to the delays of the delay devices  20 ,  21 ,  22  which are different from one another but longer in comparison with the transmission time period, sequential firing of the firing caps  6 ,  7 ,  8  thus occurs which has, inter alia, the advantage that the supply voltage source (and the capacitor  9 ) are not as heavily loaded as when there is simultaneous firing of the firing caps  6 ,  7 ,  8 . 
     The exemplary embodiment according to FIG. 3 is based on the exemplary embodiment shown in FIG. 2 in that a firing device  26  is used in FIG. 3 instead of the firing device  5  in FIG.  1 . The firing device  26  includes a decoding device  27  for receiving the firing commands  3  from the control device  2  via the line  4 . The decoding device is followed by a delay device  28  which has a delay device  29  connected downstream of it, followed by a delay device  30 . A transistor  31 ,  32 ,  33  which is provided for connecting the firing caps  6 ,  7 ,  8  to the supply voltage is connected to the output of in each case one of the delay devices  28 ,  29 ,  30 . 
     Here, the delay device  28  which directly follows the decoding device  27  has a delay which is longer than the time required for the transmission of the firing commands  3 . The delays of the delay devices  29  and  30  are, in contrast, freely selectable. 
     The embodiments shown are therefore suitable for carrying out a method according to the invention in which a firing command are transmitted repeatedly by the control device to the firing device for the firing element (firing caps). In the firing device, the transmitter firing commands are evaluated and, after the firing commands have been transmitted, the firing caps are fired with a delay. The delay can be implemented here either by means of a sufficiently dimensioned delay or else by counting the firing commands.