Abstract:
A device and a method trigger a vehicle occupant protection device of a motor vehicle. The device has a plurality of sensors that are disposed at a first location within the motor vehicle, and an evaluation device that is disposed at a second location within the passenger car. The plurality of signals that are assigned to the plurality of sensors are transmitted from the first location to the evaluation device via a first and a second transmission link of the device.

Description:
BACKGROUND OF THE INVENTION 
     Field of the Invention 
     The invention relates to a device and a method for triggering a vehicle occupant protection device of a motor vehicle. 
     Motor vehicles may be equipped with a vehicle occupant protection device which is activated, for example if the motor vehicle is in an accident, by an evaluation device and is intended thereby at least to reduce the risk of injury to the vehicle occupants in the accident. Examples of such vehicle occupant protection devices include air bags and seat belt retractors. In order to detect an accident, in general an emergency situation of the motor vehicle, the motor vehicle includes a plurality of sensors whereof the signals are evaluated by the evaluation device, as disclosed for example in WO 02/34579 A1, DE 101 23 215 A1 or indeed DE 198 07 124 A1. 
     For reliable functioning of the sensors, it may be necessary to provide at least a substantial proportion of the sensors at only particular points within the motor vehicle. Conventionally, the sensors and the evaluation device are accommodated in a common housing, which can give rise to problems of space. 
     DE 101 19 621 A1 (see FIGS. 1 and 5 and the description thereof) discloses a device for triggering a vehicle occupant protection device, having a plurality of sensors at a first location within a motor vehicle, which provide at the first location a plurality of signals including an item of information on an emergency situation of the motor vehicle, and having in each case an associated transmission link, these being provided for transmitting the plurality of signals from the first location to a second location within the motor vehicle. The remote transmission of signals from sensors in this way may, however, easily be disrupted from outside, in particular by electromagnetic or indeed mechanical influences, for example if an associated signal line is damaged mechanically or even completely severed during a vehicle accident. 
     BRIEF SUMMARY OF THE INVENTION 
     It is therefore the object of the present invention to provide a secure device and a secure method for triggering a vehicle occupant protection device of a motor vehicle such that this device may be arranged within the motor vehicle with more flexibility. 
     The object of the invention is achieved by a device for triggering a vehicle occupant protection device of a motor vehicle, including: a plurality of sensors which are arranged at a first location within the motor vehicle and provide at the first location a plurality of signals including an item of information on an emergency situation of the motor vehicle, a first and a second transmission link which are provided for transmitting the plurality of signals from the first location to a second location within the motor vehicle, the two transmission links being arranged such that both transmission links transmit at least a first signal of the plurality of signals from the first location to the second location, and an evaluation device which is arranged at the second location and has a first evaluation means, a second evaluation means and an output means, the evaluation device being constructed such that signals associated with a respective one of the sensors are supplied to the first evaluation means and the first signal is supplied to the second evaluation means, wherein the first evaluation means evaluates the signals supplied thereto for the existence of an emergency situation of the motor vehicle and passes on a corresponding first item of information to the output means, and the second evaluation means evaluates the first signal supplied thereto for the existence of an emergency situation of the motor vehicle and passes on a corresponding second item of information to the output means, and wherein the output means is constructed such that it only emits a second signal, which is provided for activating the vehicle occupant protection device of the motor vehicle, as an output signal of the evaluation device if both the first and the second items of information correspond to an emergency situation. 
     The device according to the invention for triggering a vehicle occupant protection device of a motor vehicle therefore includes the plurality of sensors arranged at the first location and the evaluation device arranged at the second location. The sensors emit the signals required for the detection of the emergency situation of the motor vehicle, and these are in turn evaluated by the evaluation device. According to the invention, the plurality of sensors and the evaluation device are arranged at two different locations within the motor vehicle. If, for operation of the inventive device, the plurality of sensors has to be arranged at a particular point within the motor vehicle, this is possible in a relatively simple manner with the inventive device, since the plurality of sensors takes up relatively little space. By contrast, the choice of location within the motor vehicle for installing the evaluation device is typically less critical. 
     However, as a result of the inventive spatial separation of the plurality of sensors and the evaluation device, when the signals are transmitted from the first location to the second, malfunctions which can have the effect of unintentionally triggering the vehicle occupant protection device may occur. For this reason, the inventive device includes the two transmission links over which the signals are transmitted from the sensors to the evaluation device, that is to say from the first location to the second location. Here, at least one of the signals of the plurality of sensors is transmitted over both the first and the second transmission link. This has the effect of creating a precondition that, in the event of disruption of one of the transmission links, the evaluation device does not unintentionally trigger the vehicle occupant protection device. This improves the reliability of the inventive device in respect of unintentional triggering of the vehicle occupant protection device. 
     The evaluation device of the inventive device includes two evaluation means. All signals are supplied to the first evaluation means, and at least the at least first signal is supplied to the second evaluation means. Both evaluation means evaluate the signals supplied thereto independently of one another and pass on the result of their evaluations to the output means of the evaluation device. The evaluation device includes for example an AND element, with the result that it only activates the vehicle occupant protection device if both evaluations of both evaluation means detect an emergency situation of the motor vehicle. This means that the risk of unintentionally triggering the vehicle occupant protection device if there is a disruption to the signals is reduced. 
     According to preferred embodiments of the inventive device, the latter is constructed such that only a first portion of the plurality of signals is transmitted to the evaluation device over the first transmission link and/or a second portion, different from the first portion, of the plurality of signals is transmitted to the evaluation device over the second transmission link. This means that the bandwidth of the two transmission links can be reduced. 
     According to a further variant of the inventive device, the latter includes first and second read devices which are arranged at the first location, the first read device reading the sensors associated with the first portion of the signals and the second read device reading the sensors associated with the second portion of the signals. Preferably, the first transmission link is arranged downstream of the first read device and the second transmission link is arranged downstream of the second read device. 
     If the at least first signal is to be transmitted to the evaluation device over both transmission links, then according to a variant of the inventive device the two read devices are constructed such that they each read the sensor associated with the first signal. 
     The first evaluation means bases its evaluation on all signals, and the second evaluation means bases its evaluation at least on the at least one first signal. If only the first signal is supplied to the second evaluation means, as provided for according to a preferred embodiment of the inventive device, then the first signal is used for example as a plausibility check of the evaluation made by the first evaluation means. 
     According to a preferred variant of the inventive device, the first signal is supplied to the second evaluation device over both the first transmission link and the second transmission link. In this way, it is possible for the second evaluation means to be able, on the basis of a comparison between the first signal transmitted over the first transmission link and the first signal transmitted over the second transmission link, to detect a disruption of one of the two transmission links and hence to be able to block triggering of the vehicle occupant protection device. 
     The object is also achieved by a method for triggering a vehicle occupant protection device of a motor vehicle, having the following method steps: providing a plurality of signals, coming from a plurality of sensors, at a first location at which the plurality of sensors is arranged within the motor vehicle, wherein the plurality of signals includes an item of information on an emergency situation of the motor vehicle, transmitting the plurality of signals over a first and a second transmission link to an evaluation device which is arranged at a second location within the motor vehicle and includes a first and a second evaluation means, wherein at least a first signal of the plurality of signals is transmitted to the evaluation device over both transmission links, supplying signals which are associated with a respective one of the sensors to the first evaluation means, and supplying the first signal to the second evaluation means, evaluating the signals supplied to the first evaluation means using the first evaluation means and evaluating the first signal using the second evaluation means, and emitting a second signal, which is provided for activating the vehicle occupant protection device of the motor vehicle, as an output signal of the evaluation device if both the evaluation made by the first evaluation means and the evaluation made by the second evaluation means give the result that the motor vehicle is in the emergency situation. 
     The inventive method may in particular be implemented using the inventive device. Preferred embodiments of the inventive method emerge from the dependent claims. 
     An exemplary embodiment of the invention is illustrated by way of example in the attached schematic drawings, in which: 
    
    
     
       BRIEF DESCRIPTION OF THE SEVERAL VIEWS OF THE DRAWING 
         FIG. 1  shows an automobile, 
         FIG. 2  shows the automobile illustrated in  FIG. 1 , as a partial block diagram, 
         FIG. 3  shows a device for detecting an emergency situation of the automobile illustrated in  FIGS. 1 and 2 , and an air bag, and 
         FIG. 4  shows a graph illustrating the time sequence of data transmission within the device shown in  FIG. 3 . 
     
    
    
     DESCRIPTION OF THE INVENTION 
       FIG. 1  shows an automobile PKW having a vehicle body  1 , a passenger compartment  2  and a steering wheel  3  which is arranged inside the passenger compartment  2 . In the case of the present exemplary embodiment, an air bag  4  (illustrated in  FIGS. 2 and 3 ) is integrated within the steering wheel  3  and, if an emergency situation of the automobile PKW occurs, for example if the latter overturns, this air bag is inflated in a generally known manner in order at least to reduce the risk of injury to a driver (not illustrated in the figures). 
     In the case of the present exemplary embodiment, the air bag  4  is activated in an emergency situation of the automobile PKW by means of a control circuit  5  illustrated in  FIG. 3 . In the case of the present exemplary embodiment, the control circuit  5  includes five acceleration sensors  6  to  10  which are read by two read devices  11 ,  12 . The sensors  6 - 10  and the two triggering devices  11  and  12  are arranged in a common housing  13 . The housing  13 , in turn, in the case of the present exemplary embodiment is arranged centrally within the passenger compartment  2  of the automobile PKW, as indicated in  FIG. 2 . 
     In the case of the present exemplary embodiment, the sensor  6  measures acceleration of the automobile PKW in relation to its longitudinal axis X, and the sensor  7  measures acceleration of the automobile PKW in relation to its transverse axis Y. Similarly, the sensor  9  measures acceleration of the automobile PKW in relation to its transverse axis Y, and the sensor  10  measures acceleration of the automobile PKW in relation to an axis Z which is aligned at a right angle to the plane defined by the longitudinal axis X and the transverse axis Y of the automobile PKW. In the case of the present exemplary embodiment, the two sensors  6  and  7  are more sensitive than the sensors  9  and  10 . The sensor  8  measures the angular acceleration of the motor vehicle PKW in relation to the Z axis. 
     The two sensors  6  and  7  are connected by way of electrical lines  14  and  15  to the first read device  11 , and the two sensors  9  and  10  are connected by way of electrical lines  16  and  17  to the second read device  12 . The first read device  11  is provided for reading the two sensors  6  and  7  and for providing the resulting electrical signals S 1  and S 2  at an output  18  of the read device  11 . The second read device  12  is provided for reading the two sensors  9  and  10  and for providing corresponding electrical signals S 3  and S 4  at an output  19  of the second read device  12 . The sensor  8  is connected via an electrical line  36  to both read devices  11  and  12 , with the result that the two read devices  11  and  12  each read the sensor  8 , and the first read device  11  provides a corresponding electrical signal S 5  at its output  18  and the second read device  12  provides a corresponding electrical signal S 5 ′ at its output  19 . The outputs  18 ,  19  of the two read devices  11 ,  12  are accessible through the housing  13 . 
     The control circuit  5  furthermore includes an evaluation device  20  which, in the case of the present exemplary embodiment, is arranged below the dashboard A of the automobile PKW. In the case of the present exemplary embodiment, the evaluation device  20  is surrounded by a housing (not illustrated in more detail) and includes a first evaluation means  21 , a second evaluation means  22  and two inputs  23  and  24 . The input  23  of the evaluation device  20  is connected to the output  18  of the read device  11  by way of a first transmission link  25 , and the output  24  of the first evaluation device  20  is connected by way of a second transmission link  26  to the input  19  of the second read device  12 . The two transmission links  25  and  26  are electrical lines in the case of the present exemplary embodiment. 
     The signals S 1  to S 5 ′ of the evaluation device  20 , associated with the sensors  6  to  10  and read by the two read devices  11  and  12 , are transmitted over the two transmission links  25  and  26 . In the case of the present exemplary embodiment, the electrical signals S 1  and S 2  associated with the sensors  6  and  7  and the electrical signal S 5  associated with the sensor  8  are transmitted to the evaluation device  20  over the first transmission link  25  every 166 μs, and the electrical signals S 3  and S 4  associated with the acceleration sensors  9  and  10  and the electrical signal S 5 ′ associated with the sensor  8  are transmitted to the evaluation device  20  over the second transmission link  26  every 166 μs. This is illustrated in  FIG. 4 . 
     Furthermore, the input  23  of the evaluation device  20  is connected to the first evaluation means  21  by way of an electrical line  27  and to the second evaluation means  22  by way of an electrical line  28 . The input  24  of the evaluation device  20  is connected to the second evaluation means  22  by way of an electrical line  29  and to the first evaluation means  21  by way of an electrical line  30 . 
     In the case of the present exemplary embodiment, the electrical signals S 1 , S 2 , S 3  and S 4  associated with the sensors  6 ,  7 ,  9  and  10  and the electrical signal S 5  transmitted over the first transmission link  25  and associated with the sensor  8  are supplied to the first evaluation means  21 . The first evaluation means  21  is furthermore constructed such that it analyzes these electrical signals S 1  to S 5  in a manner which is generally known, by comparing the electrical signals S 1  to S 5  with stored limit values. If the analysis gives the result that the automobile PKW is in an emergency situation, the first evaluation means  21  transmits a corresponding item of information by way of an electrical line  31  to an output device  32  of the evaluation device  20 . 
     In the case of the present exemplary embodiment, the second evaluation means  22  is supplied with both the electrical signal S 5  which is associated with the sensor  8  and transmitted over the first transmission link  25  and with the electrical signal S 5 ′ which is associated with the sensor  8  and transmitted over the second transmission link  26 . It is arranged such that it first compares the two electrical signals S 5  and S 5 ′ with one another. Only if the two electrical signals S 5  and S 5 ′ differ by less than a pre-fixed limit value is the electrical signal S 5  compared with a further limit value. If the electrical signal S 5  exceeds this further limit value, then the second evaluation means transmits an item of information relating to the potential existence of an emergency situation of the automobile PKW to the output device  32  by way of an electrical line  33 . 
     The output device  32  is for its part constructed such that it only passes on an electrical signal to an output  34  of the evaluation device  20  if both evaluation means  21  and  22  indicate that there is an emergency situation of the automobile PKW. 
     The output  34  of the evaluation device  20  is for its part connected to the air bag  4  by way of an electrical line  35  such that the air bag  5  is activated by way of the electrical line  35  if the output device  32  emits a corresponding signal. 
     Although the present invention has been described with reference to a preferred exemplary embodiment, the invention is not restricted thereto but may be modified in a variety of ways. In particular, vehicle occupant protection devices other than the air bag  4  described may be used.