SYSTEM FOR TRIGGERING A PROTECTING DEVICE

Abstract: A system for the connection of an ignition device (3) to a direct current network (2), the ignition device being able to be activated for triggering a safety device (4-5) in an emergency. For example, the safety device can be constituted of a safety belt stretcher or an airbag (5) in a vehicle arranged to be inflated by a gas generator (4) at a certain deceleration detected. According to an embodiment of the invention at least one safety device is connected to the internal network (2) of the vehicle via an electronic unit (1) including at least one acceleration sensor (6) and an arrangement (7) for the generation of a direct current voltage activating the ignition device (3) at a given deceleration, the direct current voltage generated being higher than the internal line voltage. The system is dimensioned such that the direct current network (2) of the vehicle does not have a potential high enough to be able to activate the ignition device.

Description: System for triggering a protecting device Field of the invention The present invention relates to a system for connecting an ignition device to a direct current network. State of art and summary of the invention. When developing a product of modern vehicles, for exemple, great attention is directed to the safety of the passengers. From a marketing point of view as well as a safety point of view airbag systems have had a great importance during the last years, in addition to safety devices as deformation zones in the car body, suitably designed fittings and safety belts. A modern airbag system may consist of control electronics, ignition devices and gas generators for one or more airbags and possibly pyrotechnical safety belt stretchers. An embodiment of the present invention discloses a system for connecting, at deceleration, at least one releaseable safety device, an airbag for exemple, or a safety belt stretcher, to a vehicle. Preferably, the system comprises an electronic unit including at least one acceleration sensor or the like, which electronic unit is connected to the internal power supply network of the vehicle and to an ignition device for the safety device. The ignition device, including a heating filament, for exemple, is arranged for triggering the safety device, a gas generator for inflating an airbag, for exemple, if an acceleration sensor detects a deceleration of a preset size. However, the system mentioned often has the disadvantage that the respective ignition device is arranged to be triggered approximately at a direct-current voltage being the same or even lower than the voltage of battery of the vehicle, and thus, if there is an error of the cables or the circuits, causing a shortcircuiting of the connections of the ignition device and the power supply network of the vehicle, the safety device is triggered. Even if such an error may be detected it is not sure that, thereafter, one can prevent triggering of the safety device belonging to it. Thus, the error may consist of, that in an electric ignition device, directly at the connections or in the cabling connecting the electronic unit with the ignition device, the one pole being unintentionally brought into contact with the battery supply of the vehicle (12- 16 volts) and the other pole with the chassis of the vehicle. Thus, in this situation an airbag can be inflated and if this happens in a traffic situation this implies obvious risks for the driver, the passengers and the road users. A solution of this problem is shown in WO 90/02673, indicating a system where an electric ignition device can be activated by an a.c.-signai greater than the internal d.c.-voltage of the vehicle. The ignition device is directly at its connections connected in series with a capacitor. The electric system of the vehicle is 12-16 volts d.c, not being able to activate the ignition device. The present invention indicates another solution of the problem mentioned, viz. preventing the safety device from being unintentionally triggered if the connections or cabling to the ignition device are short-circuited by mistake. The special characteristics of the invention are indicated in the accompanying claims. Now, the invention will be explained in greater detail by means of embodiments with reference to the drawings, wherein: Figure 1 indicates diagrammatically a safety device connected to the internal network of a vehicle according to an embodiment of the invention, Figure 2 indicates diagrammatically an ignition device and a gas generator according to an embodiment of the invention, Figure 3 indicates diagrammatically an ignition device according to an embodiment of the invention, Figure 4 indicates diagrammatically an electronic unit according to an embodiment of the invention. Description of embodiments of the invention Figure 1 indicates an electronic unit 1 connected to the internal network 2 of a vehicle and to at least one ignition device 3 of a safety device, in this case a gas generator 4 arranged to be able to inflate an airbag 5, which can be arranged in the steering-wheel of a vehicle or at the driver/passenger place or at any other appropriate place protecting the driver and the passengers from knocking their heads forwards or aside in an accident or the like. In the drawing there are two airbag systems 4-5 connected, but it is obvious that several airbag systems can be connected to the electronic unit 1. The safety system may include pyrotechnical safety belt stretchers. In the electronic unit 1 there is arranged at least one acceleration sensor 6, being able to detect deceleration at least in one direction. Besides, there can be arranged additional acceleration sensors detecting acceleration/deceleration in other directions. Furthermore, in the electronic unit 1 there is an arrangement 7 generating high d.c. voltage, i.e. significantly higher than the internal line voltage of the vehicle (12-16 volts). The arrangement 7 is connected with the respective ignition device 3 via conductors 8. Thus, when an acceleration ε-—sor 6 detects an acceleration/deceleration exceeding a preset value, the electroni- "it 1 is arranged such that the high voltage, generated by the arrangement 7, can be applied to the respective ignition device 3, which is activated and, by means of the heating filament in the ignition device 3, initiates the corresponding gas generator 4, or the like, for inflating the respective airbag 5. All this takes place very rapidly, in about 5-50 milliseconds. If, unintentionally, the conductors get into contact with the internal network 2, the airbag system 4-5 can not be triggered, as the voltage of the internal network (12-16 volts) is not high enough to activate the ignition device 3. Figure 2 indicates an ignition device 3 and a gas generator 4 according to the figure 1. At least one voltage dependent series component 9a, 9b is connected with the cables 8. This component can be arranged in the connection 9a of the ignition device 3 or constitute an integrated part 9b of the ignition device 3. For exemple, the voltage dependent series component 9a, 9b can be a diac or transil or another semi- conductor component with the quality of being able to conduct only a very low currrent up to the point where the potential of the component exceeds a threshold value. In the present case this threshold value is chosen such that it exceeds those 12-16 volts offered by the electric supply network of the vehicle. According to another embodiment a voltage dependent resistor 9 is used, see Fig. 3, which is separate, or possibly part of the heating filament 10, which can be found in the ignition device 3 for starting the gas generator 4, which heating filament 10 then must be dimensioned for this high internal resistance. The figure 3 indicates an embodiment of the ignition device 3 more in detail, the voltage dependent component 9 being connected in series with the heating filament 10. A control impedance 11 is connected in parallel with the voltage dependent component 9. This impedance is chosen such that it can not conduct an activating current but only a control current generated by the electric unit 1 in a special control device, as is explained below. D.c. as well as a.c. can be used for this control current. The figure 4 indicates an embodiment of control electronics for safety systems according to the invention. An electronic unit 1 is arranged permanently in the vehicle body, and in case of a decelaration one or more acceleration sensors 6, which are comprised in the electronic unit 1 , detect a signal which is filtered and amplified in an amplifier 12, after which a microprocessor 13, which is included in the electronic unit, analyses and compares the signals with predetermined criteria and threshold values. If the vehicle according to these critera is found to be in a collision situation requiring triggering of the safety system, the microprocessor 13 activates one or more ignition transistors 14, involving transmitting of the energy, generated in a buffer capacitor 16, via the voltage generator 7, to the ignition device 3 of the gas generator 4, and at the same time or in a sequence within 5-50 ms, the different corresponding safety devices 17a -17d are triggered. As an exemple, the safety device 17a can be an airbag arranged for the driver, 17b an airbag arranged for protecting the passenger, 17c a safety belt stretcher for the driver and 17d a safety belt stretcher for the passenger. Of course, other types of driver and passengers safety devices are possible. Parallel with the analysis of the signals from the acceleration sensors 6 included in the electronic unit 1, continuously, a control of all the functions included in the electronic unit 1 and in the safety devices 4-5, 17, are carried out. This is done continuing to guarantee the function of the system, and to warn the driver, via the warning indicator, of a defect and, in case of a critical situation, to disconnect the safety devices. Normally, this control is done several times every second, and the control impedance 11 indicated in figure 3 is used in a bridge coupling, measuring the ignition device being connected and the correct value of the resistance.

Claims: CLAIMS 1. A system for the connection of an ignition device (3) to a direct current network (2), the ignition device being able to be activated for triggering a safety device (4-5,17) in an emergency, characterized in that an arrangement for generating a direct current voltage (7) significantly higher than the voltage of the direct current network (2) is arranged, for being able to activate the ignition device (3) in said emergency, while the system being dimensioned such that the potential of the direct current network (2) is not high enough for being able to activate the ignition device (3). 2. A system according to claim 1, characterized in that the direct current network is the internal network (2) of a vehicle having at least one safety device (4-5, 17) being able to be triggered at deceleration, which system comprises an electronic unit (1) including at least one acceleration sensor (6), the electronic unit (1) being connected to the internal network (2) of the vehicle and to one ignition device (3) for each safety device ( 4-5, 17), the electronic unit (1) also including said arrangement (7) for generating a direct current voltage higher than the line voltage of the vehicle, which higher direct current voltage being arranged to activate the respective ignition device (3), for triggering the corresponding safety device (4-5, 17) after the detection of a deceleration of a predetermined size. 3. A system according to claim 2, characterized in that a voltage dependent series component (9a) is arranged in connection with the ignition device (3). 4. A system according to claim 2, characterized in that a voltage dependent series component (9b) is arranged as an integrated part of the ignition device (3). 5. A system according to claims 3-4, characterized in that the voltage dependent series component (9) is a semiconductor device. 6. A system according to claims 3-4, characterized in that the voltage dependent series component (9) is a voltage dependent resistance. 7. A system according to any one of the claims 3-6, characterized in that a control device is integrated in the system for controlling the ignition device (3) being connected to the power supply of the vehicle (2) and the resistance of the voltage dependent component (9) being within tolerance limits given, the control device including an impedance (11) connected in parallel with the voltage dependent series component (9) and dimensioned such that the impedance (11) can not conduct an activating current but only a control current. 8. A system according to any one of the preceding claims, characterized in that said arrangement for generating a direct current voltage (7) is connected to a buffer capacitor (16) and one or more ignition transistors (14). 9. A system according to any one of the preceding claims, characterized in that at least one safety device (4-5, 17) is an airbag. 10. A system according to any one of the preceding claims, characterized in that at least one safety device (4-5, 17) is a safety belt stretcher. AMENDED CLAIMS [received by the International Bureau on 22 February 1996(22.02.96); original claim 1 amended; remaining claims unchanged (2 pages)] 1. A system for the connection of an ignition device (3) to a direct current network (2), the ignition device being able to be activated for triggering a safety device (4-5,17) in an emergency, characterized in that an arrangement having a generated direct current voltage (7) significantly higher than the voltage of the direct current network (2) is arranged, for being able to activate the ignition device (3) in said emergency, while the system being dimensioned such that the potential of the direct current network (2) is not high enough for being able to activate the ignition device (3). 2. A system according to claim 1, characterized in that the direct current network is the internal network (2) of a vehicle having at least one safety device (4-5, 17) being able to be triggered at deceleration, which system comprises an electronic unit (1) including at least one acceleration sensor (6), the electronic unit (1) being connected to the internal network (2) of the vehicle and to one ignition device (3) for each safety device ( 4-5, 17), the electronic unit (1) also including said arrangement (7) for generating a direct current voltage higher than the line voltage of the vehicle, which higher direct current voltage being arranged to activate the respective ignition device (3), for triggering the corresponding safety device (4-5, 17) after the detection of a deceleration of a predetermined size. 3. A system according to claim 2, characterized in that a voltage dependent series component (9a) is arranged in connection with the ignition device (3). 4. A system according to claim 2, characterized in that a voltage dependent series component (9b) is arranged as an integrated part of the ignition device (3). 5. A system according to claims 3-4, characterized in that the voltage dependent series component (9) is a semiconductor device. 6. A system according to claims 3-4, characterized in that the voltage dependent series component (9) is a voltage dependent resistance. 7. A system according to any one of the claims 3-6, characterized in that a control device is integrated in the system for controlling the ignition device (3) being connected to the power supply of the vehicle (2) and the resistance of the voltage dependent component (9) being within tolerance limits given, the control device including an impedance (11) connected in parallel with the voltage dependent series component (9) and dimensioned such that the impedance (11) can not conduct an activating current but only a control current. 8. A system according to any one of the preceding claims, characterized in that said arrangement for generating a direct current voltage (7) is connected to a buffer capacitor (16) and one or more ignition transistors (14). 9. A system according to any one of the preceding claims, characterized in that at least one safety device (4-5, 17) is an airbag. 10. A system according to any one of the preceding claims, characterized in that at least one safety device (4-5, 17) is a safety belt stretcher.

Inventors: LUNDBERG LEIF, LUNDBERG, LEIF
Applicants: LUNDBERG LEIF, NOKIA AUDIO & ELECTRONICS AB, LUNDBERG, LEIF
Application year: 1995
Main classification: B60R21
IPC codes: B60R21