Abstract:
A vehicle safety arrangement having a sensor unit ( 7 ) comprising at least one sensor ( 8, 9 ) responsive to acceleration; an actuator ( 13 ) for activating a safety device, the actuator being located remotely from the sensor unit; and a control unit ( 2 ) located remotely from the sensor unit and from the actuator, the control unit having no sensors responsive to acceleration and being operable to receive information from the sensor unit and to transmit an actuating command to the actuator to activate the safety device.

Description:
CROSS REFERENCE TO RELATED APPLICATION 
     This application claims priority to PCT/SE2003/001622, filed Oct. 21, 2003, GB 0 224 429.1, filed Oct. 21, 2002, and GB 0 228 054.3, filed Dec. 2, 2002. 
     FIELD OF THE INVENTION 
     This invention relates to a safety arrangement for a vehicle, and in particular concerns an improved arrangement for detecting a crash situation and controlling at least one safety device, such as an air-bag. 
     BACKGROUND OF THE INVENTION 
     Modern vehicle safety systems typically comprise a main control unit, which is the hub of the system. The main control unit comprises one or more accelerometers to measure the rate of change of velocity of the vehicle, a processor operable to perform a decision algorithm on the signals output by the accelerometers in order to establish whether a crash situation has occurred and implement a crash algorithm to activate one or more safety devices accordingly, an energy source, normally in the form of one or more capacitors, storing sufficient ignition energy to activate the safety device, and an ignition circuit, which is controlled by the output of the crash algorithm, and which connects the capacitor(s) to the safety device(s) to deploy the safety device(s) upon detection of a crash situation. The control unit may also comprise means for controlling the communications between the control unit and various external units, and have a diagnostic function. 
     Due to the fact that the control unit comprises accelerometers, the control unit must be physically located in a part of the vehicle where the sensed acceleration will be representative of the acceleration of the vehicle as a whole. The ideal location for this purpose is the central tunnel of the vehicle, which comprises a ridge running along the centre of the floor of the chassis of the vehicle, and in many known systems the control unit is mounted on an upper surface of the control tunnel, i.e. within the vehicle cabin. 
     Due to the number of components contained in the control unit, the control unit is rather large and heavy. It may, therefore, be difficult to allocate sufficient space to the control unit on the central tunnel of the vehicle, which typically also carries other components such as the gear stick. 
     In addition, a heavy control unit will generate substantial vibration while the vehicle is moving, and this is likely to compromise the accuracy of the signal output by accelerometers provided therein. 
     It is an object of the present invention to alleviate one or more of the above difficulties. 
     SUMMARY OF THE INVENTION 
     Accordingly, one aspect of the present invention provides a vehicle safety arrangement, the arrangement includes a sensor unit having at least one sensor responsive to acceleration, the sensor unit being located substantially along a central longitudinal line of the vehicle. 
     The safety arrangement further includes an actuator for activating a safety device, the actuator being located remotely from the sensor unit; and a control unit located remotely from the sensor unit and from the actuator, the control unit being operable to receive information from the sensor unit and to transmit an actuating command to the actuator to activate the safety device. The control unit of this invention does not have sensors responsive to acceleration, but includes a signal processor for sampling data gathered by sensors of the sensor unit. 
     Preferably, the sensor unit is located on a central tunnel of the vehicle. 
     Conveniently, the sensor unit comprises at least two sensors responsive to acceleration, which are configured to measure at least longitudinal and lateral acceleration of the vehicle. 
     Advantageously, the at least one sensor responsive to acceleration is configured to measure vertical acceleration of the vehicle. 
     Conveniently, the signal processor is operable to transmit the sampled data to the control unit. 
     Advantageously, the signal processor is operable to perform a crash algorithm, which causes the signal processor to instruct the control unit to transmit the actuating command to the actuator. 
     Alternatively, the signal processor is operable to receive the output of a decision algorithm, which determines whether the vehicle is in a crash situation. 
     Preferably, the decision algorithm is performed in the control unit. 
     Conveniently, the signal processor is operable to receive data from other remote sensors. 
     Advantageously, the sensor unit comprises one or more sensors operable to measure an angular velocity of the vehicle around a longitudinal axis thereof. 
     Preferably, the actuator comprises an ignitor for igniting a charge to activate the safety device. 
     Conveniently, the control unit comprises one or more capacitors configured to store sufficient energy to cause the actuator to activate the safety device. 
     Advantageously, the discharge of the one or more capacitors comprises the actuation command. 
     Preferably, the actuator is located in a unit that also comprises a capacitor configured to store energy to activate the safety device, the capacitor being discharged to activate the safety device in response to the actuation command. 
     Conveniently, the safety arrangement further comprises at least one left side sensor on a left side of the vehicle and at least one right side sensor on a right side of the vehicle. 
     Advantageously, the control unit is connected to a main battery of the vehicle, and supplies power to the sensor unit and the actuator. 
     Preferably, the sensor unit has a smaller volume than that of the control unit. 
     Conveniently, the sensor unit has a volume less than half that of the control unit. 
     Advantageously, the sensor unit has a smaller mass than that of the control unit. 
     Preferably, the mass of the sensor unit is less than half that of the control unit. 
     Conveniently, the sensor unit is provided on a single microchip. 
     Advantageously, the sensor unit comprises a processor. 
    
    
     
       BRIEF DESCRIPTION OF THE DRAWINGS 
       In order that the present invention may be more readily understood, embodiments thereof will now be described, by way of example, with reference to the accompanying drawings, in which: 
         FIG. 1  shows a first safety arrangement embodying the present invention; 
         FIG. 2  shows a second safety arrangement embodying the present invention; 
         FIG. 3  shows a third safety arrangement embodying the present invention; and 
         FIG. 4  shows a fourth safety arrangement embodying the present invention. 
     
    
    
     DETAILED DESCRIPTION OF THE INVENTION 
     Referring to  FIG. 1 , a schematic representation of a first safety arrangement  1  embodying the present invention is shown. The first safety arrangement  1  comprises a control unit  2  which has a processor  3 . The processor  3  is, as discussed above, operable to apply a decision algorithm to signals received from sensors (described below), to determine from these signals whether a crash situation has occurred. Such algorithms are known in the art. 
     The control unit  2  further comprises an ignition circuit  4 , which is operable to send an actuation command (in this case in the form of an ignition energy pulse) to a safety device of the vehicle, for instance an air-bag, as will be described in more detail below. The ignition circuit  4  is connected to one or more substantial capacitors  5   a , which are charged with sufficient energy to activate the safety device, and will transmit the stored energy to the safety device upon receipt of a trigger signal from the processor  3 . Alternatively, the ignition energy could be taken directly from the vehicle battery, although the battery may become disconnected from the safety arrangement  1 , which could result in a failure of the safety device to deploy. 
     Finally, the control unit  2  comprises a voltage regulator  5   b , which receives power from the vehicle battery  6 , or from an alternative power source, and regulates the voltage for charging the capacitors but could also provide power to the processor  3 , and other components of the first safety arrangement  1 . 
     It will be appreciated that the control unit  2  will be relatively large and heavy, particularly due to the presence of the capacitors and the ignition circuit  4 , which normally comprises two switches for each safety device. The switches are respectively closed in response to an arming signal and to the trigger signal. 
     The safety arrangement  1  further comprises a sensor unit  7 , which comprises a pair of accelerometers  8  and  9  one of which is orientated so as to measure longitudinal acceleration a x  of the vehicle, and the other of which is orientated to measure lateral acceleration a y  of the vehicle. The sensor unit  7  comprises a signal processor  10 , which receives outputs from the accelerometers  8  and  9  and manipulates the data to be in a suitable form for feeding to the processor  3  of the control unit  2 . 
     Left and right sensors  11  and  12  respectively (which may also be accelerometers) are also provided, separately from the sensor unit  7 , and the left and right sensors  11  and  12  are configured to be located on respective left and right hand sides  101  and  102  (schematically illustrated) of the vehicle to provide additional information that may be useful in determining whether or not the vehicle has encountered a crash situation, or in providing information on the type of crash that has occurred. 
     The safety arrangement  1  also comprises one or more actuators  13 , in the form (in this example) of squibs or other devices such as relays which, upon activation thereof may, by way of example, inflate air-bags and release belt pre-tensioners. 
     As discussed above, it is important for the sensor unit  7  to be physically located on the vehicle in a position where the sensed acceleration will be representative of the acceleration of the vehicle as a whole. Hence, the sensor unit  7  is positioned substantially along a central longitudinal line of the vehicle. In advantageous embodiments of the invention, the sensor unit  7  is located on the central tunnel  103  (schematically illustrated) of the vehicle, and in such embodiments the sensor unit  7  may be directly attached by any suitable means to an upper or lower surface of the central tunnel, or to a covering thereof. The sensor unit  7  may be located within the cabin of the vehicle. 
     However, the control unit  2 , which comprises rather heavier components, is located remotely from the sensor unit  7  and indeed may be placed in any suitable location on the vehicle, not necessarily anywhere near the central longitudinal line thereof (e.g. on a different part of the tunnel or behind the dashboard). 
     The control unit  2  communicates with the sensor unit  7  over a sensor communication line  14 , which may take any suitable form. 
     The remote location of the control unit  2  from the sensor unit  7  means that it is not necessary to house the control unit  2  in the central tunnel of the vehicle, thus alleviating the difficulty discussed above. 
     In addition, the relatively large vibrations that the control unit  2  will undergo during movement of the vehicle will not affect the sensor unit  7 , which will therefore provide more reliable data regarding the acceleration of the vehicle. 
     The control unit  2  is also located remotely from the actuator  13 , and communicates therewith over an activation communication line  15 . As discussed above, the control unit  2  comprises an ignition circuit  4  connected to capacitors  5   a  charged with sufficient energy to activate the actuator  13  (for instance, to activate one or more ignitors to ignite the squibs), and in this embodiment the activation communication line  15  may simply comprise a power line, with the control unit  2  initiating activation of the actuator  13  by discharging the capacitors along the power line. 
     It will be appreciated that, with the above arrangement, the volume and mass of the components that are located in the sensor unit  7  on the central tunnel of the vehicle are kept to an absolute minimum, with the larger, more massive components being conveniently located elsewhere in the vehicle in the control unit  2 . 
       FIG. 2  shows a second safety arrangement  16  embodying the present invention. Common components between the first safety arrangement  1  discussed above and the second safety arrangement  16  are designated by like reference numerals. 
     In the second safety arrangement  16 , the processing unit  3  in the control unit  2  receives data from the left and right sensors  11 , 12 , and performs signal processing, the output of which is sent to the signal processor  10 , which now implements the main crash algorithm and hence decides whether the safety device is to be deployed. The signal processor  10  will, upon receiving a signal from the processing unit  3 , perform the crash algorithm, and will (if appropriate) instruct the ignition circuit  4  to send an actuation command to the actuators  13 . 
     The second safety arrangement  16  also comprises a third sensor  17  in the sensor unit  7 , this third sensor  17  being position to allow measurement of movement of the vehicle around the roll axis (angular velocity, ω x ). Components of second safety arrangement  16 , along with additional embodiments described below, include components common with those of the first safety arrangement  1 , and are identified by like reference numbers. 
       FIG. 3  shows a third safety arrangement  18  embodying the present invention. The third safety arrangement  18  comprises further sensors  19 , which measure parameters of the car other than the acceleration thereof. For instance, the further sensors  19  may detect whether seat belt buckles are engaged, or may otherwise detect the presence of an occupant in a given seat of the vehicle, for instance by the weight exerted on the seat, or may measure the position of the seat or a part thereof (such as the headrest). The further sensors  19  may also gather information relating to the speed of the vehicle. The information output by the further sensors  19  is passed to the control unit  2  via an information bus  20 , which allows communication between the control unit  2  and any other remote crash sensors (for instance the left and right sensors  11  and  12 ) and the actuator  13 . 
     The information gathered by the further sensors  19  allows the processor  3  of the control unit  2  to arrive at a more informed decision regarding whether to activate the safety device. For instance, if the further sensors  19  detect that the passenger seat of the vehicle is unoccupied during a crash, the control unit  2  may prevent the triggering of a passenger-side air-bag, since this is unlikely to offer protection to the occupants of the vehicle, and may hinder efforts to leave the vehicle, or remove people from the vehicle, following a crash. 
     Also, in the third safety arrangement  18 , the sensor unit  7  is provided on a single microchip, and it will be appreciated that this arrangement further reduces the size and mass of the components that are to be located in the central tunnel of the vehicle. 
     With reference to  FIG. 4 , a fourth safety arrangement  21  embodying the present invention is shown. The fourth safety arrangement  21  is similar to the third safety arrangement  18 , however each safety device is provided with a unit comprising a capacitor  5   a , an ignition circuit  4  and an actuator  13 , and the information bus  20  continuously transmits power from the control unit  2  to the capacitors and other remote units of the arrangement  21 , including for instance the sensor unit  7 . The bus  20  also transmits the actuation command, now in form of a trigger signal, from the processor  3  to the ignition circuits. If an arming switch is used in circuit  4 , an arming signal will also be sent. The sensor unit could also comprise a vertical accelerometer  22  to measure vertical acceleration a z . 
     It will be understood that the present invention provides an improved safety arrangement, providing favourable distribution of components around a vehicle, while improving the accuracy with which a crash situation may be detected. 
     As a person skilled in the art will readily appreciate, the above description is meant as an illustation of the implementation of the principles of this invention. This description is not intended to limit the scope or application of this invention in that the invention is susceptible to modificatioon, variation and change, without departing from the spirit of this invention, as defined in the following claims.