Abstract:
An airbag apparatus for safety includes an airbag inflating in response to a signal, and a sensor sensing a movement and generating the signal in response to the movement. A controller is configured to issue a command for squibbing a squib based on the signal. The airbag apparatus also includes a plurality of drivers operating in response to the command and a plurality of independent channels connecting the controller and the drivers to transmit the command from the controller to the drivers and a plurality of switching elements to squib the squib for inflating the airbag, for example, in a vehicle.

Description:
BACKGROUND OF THE INVENTION 
     1. Technical Field of the Invention 
     The present invention relates generally to an on-vehicle airbag system for protecting occupants by inflating an airbag in a car upon collision. 
     2. Background Art 
     Cars are essential to modem life, and an airbag has also become essential for protecting an occupant. A circuitry of a related airbag system (Japanese Patent First Publication No. 9-240416) is shown in  FIG. 1 . As shown, the airbag system  100  comprises a Cpu (Central Processing Unit)  101 , am IC (Integral Circuit)  102  having a first switching element  106  and a second switching element  107 , a mechanical sating sensor  103 , an acceleration sensor  104  (hereinafter, simply referred to as “G-sensor”), a safing switching element  105 , and a squib  120 . 
     A series of operation procedures upon collision is described below. A signal from the mechanical safing sensor  103  is sent to the CPU  101  through an I/O circuit  108 . If the CPU decides to choose ON, an approval signal is issued, and sent to an AND gate  110  through a signal line L 100 . The approval signal is also sent to an AND gate  111  through a signal line L 101 . 
     On the other hand, a detected signal from the G-sensor  104  is sent to the CPU  101  through an A/D (Analog to Digital) converter  109 . If the CPU  101  chooses to squib, a driving signal is issued and sent to the AND gate  111  through a signal line L 102 . If both of the driving signal and the approval signal are sent to the AND gate  111 , an AND signal is sent to a SCI (Serial Communication Interface)  112  from the AND gate  111 . The AND signal is sent to the SPI (Serial Parallel Interface)  113  through a serial transmission channel  119 , and the AND signal is sent to the AND gate  110  through a signal line L 104 . If both of the AND signal and the approval signal are sent to the AND gate  110 , a safing switching element  105  is activated. 
     The driving signal is also sent to a SCI  114  through a signal line L 103 . The driving signal is sent to a SPI  116  in the IC  102  through a serial transmission channel  115 . The driving signal from the SPI  116  is sent to a driving circuit  117  through a signal line L 105 . The first switching element  106  is driven by the driving circuit  117 . The driving signal from the SPI  116  is also sent to a driving circuit  118  through a signal line L 106 . The second switching element  107  is driven by the driving circuit  118 . If the safing switching element  105 , the first switching element  106 , and the second switching element  107  are all driven (that is, all of the elements are made ON), an electric current flows in an electric power line L 107 . A squib  120  generates heat on account of the electric current, and an inflator is fired up, resulting in inflation of an airbag in a car. 
     However, the airbag system  100  has only one channel  115  to connect the CPU  101  and the switching elements  106  and  107  in the IC  102 . (The channel  119  connects only the CPU  101  and the AND gate  110 .) 
     Because there is only one channel  115 , if the channel  115  is effected by, for example, an external noise, it is likely to cause a problem on both of the first switching element  106  and the second switching element  107  simultaneously. Thus, an operation reliability of the airbag system is low. 
     SUMMARY OF THE INVENTION 
     An airbag system of the present invention has been developed considering the above issue in the background art. A purpose of the present invention is to offer the airbag system with a high operational reliability against, for example, an external noise. 
     In order to accomplish the above object, as one aspect of the present invention, there is provided a circuit configured to activate an actuator comprising: a sensor sensing a predetermined physical event to provide a signal indicative of the event; a controller responsive to the signal inputted from the sensor to output actuator activating signals; a plurality of switch drivers responsive to the actuator activating signals outputted from the controller to produce switch on-signals, respectively; a plurality of independent channels each of which connects the controller to one of the switch drivers to transmit the actuator activating signals from the controller to the switch drivers, respectively; and a plurality of switches designed to be turned on in response to the switch on-signals produced by the switch drivers, respectively, the switches being so connected in series with each other that when the switches are all turned on, an actuator turning on-signal being provided to activate the actuator. 
     Preferably, the actuator is a squib for inflating an airbag mounted on a vehicle. 
     As a second aspect of the present invention, there is provided an airbag apparatus for safety comprising: an airbag inflating in response to a signal; a sensor sensing a movement and generating the signal in response to the movement; a controller configured to issue a command for squibbing the squib based on the signal; a plurality of drivers operating in response to the command; a plurality of independent channels connecting the controller and the plurality of drivers to transmit the command from the controller to the plurality of drivers; and a plurality of switching elements, mutually connected in series and driven by the plurality of drivers respectively, to squib the squib. 
     The above configurations of the present invention can be reduced into practice as follows. 
     An airbag system of the present invention is characterized by comprising a CPU, an IC having a plurality of switching elements for squibbing a squib in response to a command of the CPU, and a plurality of independent channels connecting the CPU and the IC independently, for informing the command of the CPU to the plurality of switching elements for squibbing the squib. 
     Briefly, the airbag system of the present invention comprises a plurality of channels. In the airbag system of the present invention, if one of the channels is effected by an external noise, a problem is caused only on the switching element which is informed of a squibbing command through the channel which is effected by the external noise. In other words, the problem is not caused on the switching element connected to the other channel. As a result, a probability for causing the problem on all of the switching elements simultaneously becomes low. Because of the above reason, the airbag system of the present invention has a high operational reliability against, for example, an external noise. 
     Optimally, the plurality of channels are a type of serial transmission system for giving the squibbing command. In other words, all of the channels of the present invention are the type of serial transmission system. Interconnection of the serial transmission system is simpler than that of a parallel transmission system. This means that a circuitry of the serial transmission system becomes simpler than that of the parallel transmission system. 
     Optimally, the plurality of channels comprises a HI side (potentially high side) channel and a LO side (potentially low side) channel. The HI side channel is connected to a higher voltage side of an electric power line for a squib, and the LO side channel is connected to a lower voltage side of it. A signal inputted from a sensor is processed by the CPU based on predetermined programs. A HI side switching element driving signal with high voltage and a LO side switching element driving signal with low voltage are issued based on a result of processing carried out by the CPU. The HI side switching element driving signal transmits in the HI side channel, and drives the switching element connected electrically to the HI side channel. Also, the LO side switching element driving signal transmits in the LO side channel, and drives the switching element connected electrically to the LO side channel. With the above composition, a high operation reliability is realized even though the circuitry is simple in its configuration and the signal processing is also simple. 
     Optimally, at least, one of the HI side channel and the LO side channel has a plurality of routes for driving the plurality of switching elements in the above configuration. 
     With the above composition, the plurality of switching elements can be driven by the one channel. As a result, the circuitry becomes simple if a plurality of airbags are set, for example, in front of a driver&#39;s seat, to the side of the driver&#39;s seat, in front of a passenger&#39;s seat and to the side of the passenger&#39;s seat. 
     Also, the HI side channel and the LO side channel are independent of each other in this configuration. Thus, a high operation reliability is realized even if the channel is effected by, for example, an external noise. 
     Embodiments of the airbag system of the present invention are shown below. 
    
    
     
       BRIEF DESCRIPTION OF THE DRAWINGS 
       The present invention will be understood more fully from the detailed description given hereinbelow and from the accompanying drawings of the preferred embodiments of the invention, which, however, should not be taken to limit the invention to the specific embodiment but are for the purpose of explanation and understanding only. 
       In the drawings: 
         FIG. 1  is a circuit diagram of a conventional airbag system; 
         FIG. 2  is a block diagram showing an airbag system of a first embodiment of the present invention; 
         FIG. 3  is a block diagram showing an airbag system of a second embodiment of the present invention; 
         FIG. 4  is a block diagram showing an airbag system of a third embodiment of the present invention; and 
         FIG. 5  is a block diagram showing an airbag system of a fourth embodiment of the present invention. 
     
    
    
     DETAILED DESCRIPTION OF THE PREFERRED EMBODIMENTS 
     First Embodiment 
     First, an arrangement of an airbag system of a first embodiment for automobile application will now be described. A block diagram of the airbag system of the first embodiment is shown in  FIG. 2 . As shown in  FIG. 2 , the airbag system  1  comprises a CPU  2 , an IC  3 , a mechanical safing sensor  40 , a G-sensor  41 , a safing switching element  50 , and a squib  6 . 
     The CPU  2  includes a first I/O circuit  20 , an A/D converter  21 , a second  110  circuit  22 , a HI side (potentially high side) SCI  23 , and a LO side (potentially low side) SCI  24 . The first I/O circuit  20  is connected to the mechanical safing sensor  40 . The A/D converter  21  is connected to the electrical G-sensor  41 . The second I/O circuit  22  is connected to a safing switching element driving circuit  51  which drives a safing switching element  50 . 
     The IC  3  includes a HI side SPI  30 , a LO side SPI  31 , a HI side driving circuit  32 , a LO side driving circuit  33 , a HI side switching element  34 , and a LO side switching element  35 . The HI side SPI  30 , the HI side driving circuit  32  and the HI side switching element  34  are connected in series to each other. The LO side SPI  31 , the LO side driving circuit  33  and the LO side switching element  35  are also connected in series to each other. 
     The HI side SCI  23  is connected to the HI side SPI  30  by a HI side serial transmission channel  70 . The LO side SCI  24  is connected to the LO side SPI  31  by a LO side serial transmission channel  71 . 
     The channels  70  and  71  are signal lines made of wires, respectively. The each channel includes the wire and ports located at the both ends of the wire, that is, the SCI and SPI. A wireless channel using electromagnetic waves or rays is also possible. 
     The safing switching element  50 , the HI side switching element  34 , and the LO side switching element  35  are connected in series by an electric power line L 1 . A squib  6  is positioned between the HI side switching element  34  and the LO side switching element  35 . The squib  6  has a role of inflating an airbag mounted in front of the driver&#39;s seat. 
     An operating procedure of the airbag system upon collision in the first embodiment will now be described. A signal from the mechanical safing sensor  40  is inputted to the CPU  2  through the first I/O circuit  20 . Alternatively, a signal from the G-sensor  41  is inputted to the CPU  2  through the A/D converter  21 . 
     These signals are processed by the CPU  2  with predetermined programs. If the result of the processing carried out by the CPU  2  meets a predetermined condition, a safing switching element driving signal, a HI side switching element driving signal, and a LO side switching element driving signal are issued. 
     The safing switching element driving signal is sent to the safing switching element driving circuit  51  through the second I/O circuit  22 . If the safing switching element driving circuit  51  receives the safing switching element driving signal, the circuit  51  drives the switching element  50 . 
     The HI side switching element driving signal is sent to the HI side driving circuit  32  through the HI side SCI  23 , the HI side channel  70 , and the HI side SPI  30 . If the HI side driving circuit  32  receives the HI side switching element driving signal, the circuit  32  drives the switching element  34 . 
     The LO side switching element driving signal is sent to the LO side driving circuit  33  through the LO side SCI  24 , the LO side channel  71 , and the LO side SPI  31 . If the LO side driving circuit  33  receives the LO side switching element driving signal, the circuit  33  drives the switching element  35 . 
     If the safing switching element  50 , the HI side switching element  34 , and the LO side switching element  35  are driven, that is, the all elements are made ON, an electric current flows in the electric power line L 1 . Thus, the squib  6  is caused to generate heat by the current and then, an inflator is fired up, resulting in inflation of the airbag in the automobile. 
     Advantages of the airbag system of this embodiment can be described as below. In the case of airbag system  1  of this embodiment, if the HI side channel  70 , that is, one of the HI side channel  70  and the LO side channel  71 , is effected by an external noise, a problem resulting from the noise is caused only on the HI side switching element  34 . However, such a problem is not caused on the LO side switching element  35 . This means that a probability of simultaneously occurring problem on both of the HI side switching element  34  and the LO side switching element  35  is low. Because of this reason, a high operational reliability of the airbag system  1  of this embodiment is realized even if the airbag system  1  receives, for example, an external noise. The airbag system  1  of this embodiment uses the serial transmission system for both the HI side channel and the LO side channel, resulting in a simple circuitry of the airbag system  1 . 
     Second Embodiment 
     Referring to  FIG. 3 , an airbag system of a second embodiment according to the present invention will now be described. The difference between the first embodiment and the second embodiment is that the second embodiment includes two squibs contrasted with the single squib in the first embodiment. Accordingly, an IC includes two HI side (potentially high side) switching elements and two LO side (potentially low side) switching elements. Thus, only different points from the first embodiment will be described below. 
     A circuitry of an airbag system of the second embodiment is shown in  FIG. 3 . Components corresponding to those of the first embodiment are shown with the same reference numbers in the first embodiment. 
     An IC  3  includes a HI side SPI  30 , a LO side SPI  31 , a HI side first driving circuit  32   a , a HI side second driving circuit  32   b , a LO side first driving circuit  33   a , a LO side second driving circuit  33   b , a HI side first switching element  34   a , a HI side second switching element  34   b , a LO side first switching element  35   a , and a LO side second switching element  35   b . The HI side SPI  30 , the HI side first driving circuit  32   a , and the HI side first switching element  34   a  are connected in series to each other. The HI side SPI  30 , the HI side second driving circuit  32   b , and the HI side second switching element  34   b  are also connected in series to each other. The LO side SPI  31 , the LO side first driving circuit  33   a , and the LO side first switching element  35   a  are connected in series to each other. The LO side SPI  31 , the LO side second driving circuit  33   b , and the LO side second switching element  35   b  are also connected in series to each other. A squib  6   a  is positioned between the HI side first switching element  34   a  and the LO side first switching element  35   a . The squib  6   a  has a role of inflating an airbag set in front of the driver&#39;s seat. A squib  6   b  is positioned between the HI side second switching element  34   b  and the LO side second switching element  35   b . The squib  6   b  has a role of inflating an airbag set in front of a passenger&#39;s seat. 
     If a safing switching element  50  is driven, and if the HI side first switching element  34   a  is driven by the HI side first driving circuit  32   a , and also if the LO side first switching element  35   a  is driven by the LO side first driving circuit  33   a , an electric current flows in a electric power line L 1 . The squib  6   a  generates heat by the electric current, and then, an inflator is fired up, resulting in inflation of the airbag in the automobile. 
     Also, if the safing switching element  50  is driven, and if the HI side second switching element  34   b  is driven by the HI side second driving circuit  32   b , and also if the LO side second switching element  35   b  is drived by the LO side second driving circuit  33   b , an electric current flows in the electric power line L 1 . The squib  6   b  generates heat by the electric current, and an inflator is fired up, resulting in inflation of the airbag in the automobile. 
     The airbag system  1  of the second embodiment has identical advantages to that of the first embodiment. If the HI side channel  70 , that is, one of the HI side channel  70  and the LO side channel  71 , is effected by an external noise, a problem resulting from the noise is caused only on the HI side first switching element  34   a  and the HI side second switching element  34   b . However, the problem is not caused on the LO side first switching element  35   a  and the LO side second switching element  35   b . This means that a probability of the problem occurrence on both of the HI side first switching element  34   a  and the LO side first switching element  35   a  simultaneously is low. Also, a probability of the simultaneous problem occurrence on both of the HI side second switching element  34   b  and the LO side second switching element  35   b  is low. Because of the above reasons, a high operational reliability of the airbag system  1  of this embodiment is realized even if the airbag system  1  receives, for example, an external noise. 
     In the airbag system  1  of this embodiment, the HI side first switching element  34   a  and the HI side second switching element  34   b  are driven by the HI side channel  70 . Also, the LO side first switching element  35   a  and the LO side second switching element  35   b  are driven by the LO side channel  71 . Accordingly, a circuitry of this embodiment becomes simple compared with a configuration in which each switching element has its own channel. 
     Third Embodiment 
     Referring to  FIG. 4 , an airbag system of a third embodiment according to the present invention will be described. The difference between the first embodiment and the third embodiment is that the third embodiment has a mechanical safing sensor instead of both the safing switching element and the safing switching element driving circuit adopted in the first embdiment. Thus, only different points from the first embodiment will be described below. 
     A circuitry of an airbag system of the third embodiment is shown in  FIG. 4 . Components corresponding to those of the first embodiment are shown with the same reference numbers in the first embodiment. 
     As shown in  FIG. 4 , the mechanical safing sensor  52  is connected to a HI side (potentially high side) switching element  34  and a LO side (potentially low side) switching element  35  in series to each other through an electric power line L 1 . A signal from the mechanical safing sensor  52  is sent to a CPU  2  through a second I/O circuit  22 . 
     The airbag system  1  of the third embodiment has identical advantages to that of the first embodiment. Also, a circuitry of the CPU  2  for the airbag system  1  of the third embodiment becomes simple. 
     Fourth Embodiment 
     Referring to  FIG. 5 , an airbag system of a fourth embodiment according to the present invention will now be described. The difference between the second embodiment and the fourth embodiment is that a safing switching element of the fourth embodiment is positioned in an IC. Thus, only different points from the second embodiment will be described below. 
     A circuitry of an airbag system according to the fourth embodiment is shown in  FIG. 5 . Components corresponding to those of  FIG. 3  are shown with the same reference numbers of  FIG. 3 . 
     As shown in  FIG. 5 , a safing switching element driving signal is sent to a safing switching element driving circuit  51  through a safing SCI  25 , a serial transmission channel  72 , and a safing SPI  36 . A safing switching element  50  is driven by the safing switching element driving circuit  51 . 
     An airbag system  1  of the fourth embodiment has identical advantages to that of the first embodiment. Also, in the fourth embodiment, all of the switching elements are positioned in an IC  3 , reducing assembly space in the airbag system  1 . 
     Modifications 
     The present invention may be embodied in other specific forms without departing from the spirit or essential characteristics of it. The present embodiments are therefore to be considered in all respects as illustrative and not restrictive, the scope of the present invention being indicated by the appended claims rather than by the foregoing description and all changes which come within the meaning and range of equivalency of the claims are therefore intended to be embraced therein. 
     The various embodiments of the airbag system have been explained. However, composition and configuration of the embodiment that can be adopted by the present invention are not limited to those explained in the above. It is possible for a person skilled in the art to implement many other modified, or improved embodiments. 
     For example, there is no limitation in the number of squibs. The number of the squibs will depend on the number of airbags. It is possible to increase the number of switching elements connected to the HI side channel  70  and the LO side channel  71  respectively. 
     In addition, the airbag system of the present invention is applicable to many kinds of vehicles such as automobiles, motorbikes, carriages at amusement parks, and trains and airplanes.