BACKGROUND OF THE INVENTION  
       [0001]     1. Field of the Invention  
         [0002]     The present invention relates to a charging method for a plurality of squibs which charge storage devices built or attached to the squibs which are connected to an ignition control device via a common bus, and can be selectively operated by electrical energy and an electrical signal which are supplied from the ignition control device.  
         [0003]     Priority is claimed on Japanese Patent Application No. 2004-028090, filed Feb. 4, 2004, the content of which is incorporated herein by reference.  
         [0004]     2. Description of Related Art  
         [0005]     In an occupant restraint system used at the time of a collision as examplified by an air bag device, a gas is produced by combustion of the propellant mainly built in an occupant restraint system as high pressure gas which is used.  
         [0006]     Moreover, an ignition element which plays a role in igniting the propellant is also built in the occupant restraint system with the propellant.  
         [0007]     Each ignition element and an ignition control device which controls the ignition element is connected one-to-one via a harness.  
         [0008]     However, there is a problem in that the number of ignition elements also increases by increasing the number of occupant restraint systems using the propellant mounted in a car, the number of harnesses increase in accordance with the increase of the number of the occupant restraint systems, and the need to remodel the ignition control device may arise.  
         [0009]     On the other hand, a technology in which a plurality of squibs in which are built the ignition elements, the ignition circuits which operate the ignition elements, the communication circuit which is required in the case of communicating with the ignition control device are connected to the common bus extended from the ignition control device, and electric power is supplied from the ignition control device to all squibs, while the ignition control device supplies the electrical signal only to a predetermined squib and ignites the ignition element is proposed (Patent Document 1: Japanese Unexamined Patent Application, First Publication No. H10-154992; Patent Document 2: Japanese Unexamined Patent Application, First Publication No. 2000-241098).  
         [0010]     Moreover, a squib which includes the communication circuit required in the case of communicating with the ignition control device via the bus, and the ignition circuit which operates the ignition element is proposed (Patent Document 2).  
         [0011]     Furthermore, a technology which enables connecting the existing occupant restraint system with a bus without any changes by building an IC which holds the communication circuit, the ignition circuit, and the ignition element within a squib having a conventional external shape without modifying the existing occupant restraint system is being examined.  
         [0012]     Furthermore, regarding the squib which builds or attaches the circuit for connecting the bus transmitting electric power and a data signal such as the squib attaching the communication circuit and the ignition circuit according to Patent Document 2, as an energy source which heats the ignition element and ignites the squib, a technique of accumulating electric power obtained from the ignition control device to the storage devices, such as a condenser, via the bus is proposed.  
         [0013]     In this way, in the state in which sufficient electric power is accumulated in the storage device, electric power which should be supplied from a bus to the storage device can be held down to a level required for supplementing the electric charge lost in natural electric discharge and the like.  
         [0014]     However, when there are many squibs connected to the bus, the storage devices for supplying ignition energy which is built or attached the squibs also increase in proportional to the number of the squibs, but the amount of electric power from the bus is usually small.  
         [0015]     For this reason, after the ignition control device begins to operate, it is necessary that a special charging technique to be used, and each storage device is charged to some degree in advance so that charging can be completed in a short time in preparation for a collision.  
         [0016]     However, when the constitution in which, in the state of connecting a plurality for squibs to the bus, each storage device charges by drawing charging electrical current simultaneously from a bus is adapted, the failure of the bus itself or the ignition control device which supplies electrical current may arise when the input of electrical current is excessive.  
         [0017]     Therefore, in order to prevent the above problem, a new electrical current restriction element or new electrical current restriction circuit should be introduced, and thereby the number of parts is increased, while the cost increases.  
         [0018]     Moreover, when the constitution of performing the restriction of electrical current by resistance at the side of the ignition control device or each squib in order to suppress the total amount of input current at the time of starting charging is adopted, thereinafter, a large quantity (that is, a degree that a problem arises in the case of drawing electrical current to all squibs simultaneously) of electrical current cannot be drawn in each squib.  
         [0019]     As a countermeasure therefor, a technique of performing restriction of electrical current with high resistance value only at the time of the initial charge has been considered. However, even if such a technique is used, when the total amouont (the total capacity) of the storage devices increases or decreases, as the case may be, the ignition control device must change the amount of electrical current at the time of the initial charging.  
         [0020]     In such a case, there is a problem in that an advantage of using the bus which does not need circuit change of the ignition control device is lost.  
         [0021]     On the other hand, when the storage device acts as an ignition energy supply source in the squib, it is indispensable to diagnose the final initial charge and the fact of being a necessary and sufficient capacity by using a certain means.  
         [0022]     In contrast, the adoption of a constitution of setting a diagnostic circuit in each storage device which is built in or attached to each squib connected to the bus has been considered.  
         [0023]     However, it is important and necessary for the ignition control device to ultimately be able to comprehend a diagnostic result.  
         [0024]     For this reason, when a complicated circuit or a complicated technique for each diagnosis itself is not required, the circuit and the communication protocol for transmitting the diagnostic result to the ignition control device by communication is required, and thereby there is a problem of increase in communication specifications or cost.  
       SUMMARY OF THE INVENTION  
       [0025]     The objects of the present invention are to provide an ignition method for squibs in which the amount of initial charge electrical current for the storage device can be regulated regardless of increase and decrease in the number of squibs, and in which reliability can be enhanced.  
         [0026]     In order to solve the above problems, the present invention adopted the following means.  
         [0027]     The present invention is a charging method for a plurality of squibs which charges each storage device built in or attached to each squib which is connected to an ignition control device via a common bus, and can be selectively operated by electrical energy and electrical signal which are supplied from the ignition control device, in which, in the case of charging each storage device, the ignition control device carries out a direction of charging initiation, an electric power supply for charging, and a direction of charging stop for each storage device successively, and thereby the charging for all storage devices is completed.  
         [0028]     According to the present invention, the amount of initial charge electrical current for the storage device can be regulated regardless of increase or decrease in the number of squibs which the storage device is built in or attached to, and a safe design for preventing the initial charge electrical current from operating as input electrical current can be easily conducted.  
         [0029]     Moreover, because an electrical current limitation circuit in the ignition control device does not need to modify specifications regardless of increase and decrease in the number of the squibs, an primary advantage of using the bus can be derived, and an increase of cost due to the increase of the useless specifications can be avoided.  
         [0030]     In the present invention, when the ignition control device transmits an electrical signal which implies an ignition initiation to a charging control circuit for the storage device in each squib via the bus, a path which draws electrical current from the bus to the storage device of the squib is formed, and an initial charging of the storage device may be initiated using electrical power provided from the ignition control device.  
         [0031]     According to the present invention, when the charging initiation is detected, the path which makes it possible to charge quickly is formed, and thereby rapid and safe charging can be conducted.  
         [0032]     In the present invention, in the case in which electrical power for the initiation charging of each storage device is supplied, the ignition control device monitors the electrical current which is consumed by the bus, and when an electrical current value thereof conforms with the electrical current value of the electrical current which is consumed by the bus before the charging operation is initiated, a supply of electrical power for the squib is completed, the time taken for completion of charging is sought, and the ignition control device may judge the capacity of each storage device by computing the capacity from the charging time using a time constant of the storage device.  
         [0033]     According to the present invention, the capacity of each storage device can be judged accurately, the ignition control device is able to comprehend a diagnostic result ultimately without an increase in the communication specifications or cost.  
         [0034]     In the present invention, in the case in which electrical power for an initiation charging of each storage device is supplied, a charging control circuit for the storage device in each squib monitors electrical current which is consumed by the bus, and when an electrical current value thereof conforms with the electrical current value of the storage device before the charging operation is initiated, a completion of charging is detected and is notified to the ignition control device, the time taken for completion of charging is sought, and the charging control circuit for the storage device in each squib may judge the capacity of each storage device by computing the capacity from the charging time using a time constant of the storage device.  
         [0035]     According to the present invention, the capacity of each storage device can be judged accurately, the ignition control device is able to comprehend a diagnostic result ultimately without an increase in the communication specifications or cost.  
         [0036]     In the present invention, when each electrical signal which implies an ignition completion of each storage device is transmitted to the ignition control device via the bus, a completion of charging of each storage device is detected by the ignition control device, while when the ignition control device detects the completion of charging of each storage device, a path which draws in electrical current from the bus to the storage device is blocked, and thereby the initial charging is finished, and a supplement charge from the bus may be conducted.  
         [0037]     According to the present invention, because the ignition control device can directly diagnose the capacity of each storage device, the cost for providing the capacity diagnosis circuit at the side of the storage device or the need to transmit a diagnosis result due to the communication and the like will not occur.  
         [0038]     Moreover, a diagnosis of short breakdown in addition to a capacity diagnosis can be conducted.  
         [0039]     In the present invention, in the case in which electrical power for the initiation charging of each storage device is supplied, the ignition control device monitors electrical current which is consumed by the bus, and when an electrical current value thereof conforms with the electrical current value of the electrical current which is consumed by the bus before a charging operation is initiated, a completion of charging is detected, when a path which draws in electrical current from the bus to the storage device is blocked, the initial charging is finished, and a supplement charge from the bus may be conducted.  
         [0040]     According to the invention, because the ignition control device can directly diagnose the capacity of each storage device, the cost for providing a capacity diagnosis circuit at the side of the storage device or for causing a need to transmit a diagnosis result due to the communication and the like will not occur.  
         [0041]     Moreover, a diagnosis of short breakdown in addition to a capacity diagnosis can be conducted. 
     
    
     BRIEF DESCRIPTION OF THE DRAWINGS  
       [0042]      FIG. 1  is a schematic diagram of a deployment control system which has a plurality of squibs according to a preferred embodiment of the present invention.  
         [0043]      FIG. 2  is a block diagram showing a circuit structure of the squib shown in  FIG. 1 .  
         [0044]      FIG. 3  is a graphical view showing a relationship between time and voltage at the time of initial charging of each squib.  
         [0045]      FIG. 4  is a graphical view showing a relationship between time and electric current at the time of initial charging of each squib.  
         [0046]      FIG. 5  is a diagram showing modification of the squib. 
     
    
     DETAILED DESCRIPTION OF THE INVENTION  
       [0047]     The squib according to the preferred embodiment of the present invention will be explained with reference to the figures.  
         [0048]      FIG. 1  is a schematic diagram of a deployment control system of the squibs which are included in an air bag device according to an embodiment of the present invention.  
         [0049]     As shown in  FIG. 1 , the ignition control device  17  and a plurality of squibs  1 , 1  are connected via the bus  19 .  
         [0050]     The ignition control device  17  is a control device which is a center of an occupant protection apparatus which protects an occupant from an impact on a vehicle.  
         [0051]     Each squib  1  is provided to a plurality of assistant restriction apparatus (not shown in the drawings) one-to-one which is positioned at the proper place of the vehicle in order to protect the occupant, and is connected in parallel using the unbalanced type of bus  19 , for example in which one of a pair of wire rods is grounded.  
         [0052]     Moreover, each squib  1  builds in the communication control circuit  10 , the condenser  13  which is the storage device, the heat producing portion which is the ignition element, and the ignition agent at the upper portion of the header  4  which includes pins  7  and  8  which are connection terminals provided in order to connect with two lines type of bus line which is the external signal wire.  
         [0053]     A circuit structure of each squib  1  is explained referring to  FIG. 2 .  
         [0054]     As shown in  FIG. 2 , each squib  1  is provided with an initial charging circuit  20  and a stationary charging circuit  21  in addition to the condenser  13 . These charging circuits  20  and  21  are connected to the bus  19  via a switching means  24 .  
         [0055]     The switching means  24  is provided with a terminal  23   a  connected to the bus  19 , a terminal  23   b  connected to the terminals except the charging circuits  20  and  21 , a terminal  23   c  connected the initial charging circuit  20 , a terminal  23   d  connected to the stationary charging circuit  21 , and a switch  22  which is rotatably connected to the terminal  23   a , and is able to connect to the terminals  23   b - 23   d , selectively.  
         [0056]     A resistance component of the initial charging circuit  20  is set up lower than the resistance component of the stationary charging circuit  21 , and the initial charging circuit  20  can perform the charging in a shorter time than the stationary charging circuit  21 .  
         [0057]     Furthermore, the switch  22  connected the terminal  23   a  is connected with the terminal  23   b , and thereby, the path (the path A) which does not charge to the condenser  13  is formed.  
         [0058]     Moreover, the switch  22  is connected to the terminal  23   c , and thereby, the path (path B) which performs the initial charging to the condenser  13  is formed.  
         [0059]     Furthermore, the switch  22  is connected to the terminal  23   d , and thereby, the path (the path C) which performs the stationary charging to the condenser  13  is formed.  
         [0060]     The charging method for each squib constituted as such is explained.  
         [0061]     In an initial state, the switch  22  of each squib  1  is connected to the terminal  23   b , and thereby, the path A which is indifferent to the charging is formed.  
         [0062]     Then, a charging process is performed for each squib successively using the ignition control device  17 .  
         [0063]     Thereinafter, an example of one squib  1  among each squib  1  is explained.  
         [0064]     First of all, the ignition control device  17  transmits an electrical signal which implies the charging initiation to the control circuit  10  of the squib  1  which is an object of the charging process via the bus  19 .  
         [0065]     Thereby, the switch  22  of the squib  1  is switched from the terminal  23   b  to the terminal  23   c , and the path B which performs the initiation charging is formed.  
         [0066]     Then, the initial charging is started for the condenser  13  of the squib  1 .  
         [0067]     At this time, the ignition control device  17  monitors electrical current consumed by the bus  19 , and conducts the capacity diagnosis of the condenser  13 .  
         [0068]     This is concretely explained referring to  FIG. 3  and  FIG. 4 .  
         [0069]     The capacity of the condenser  13  is represented by “C”, a sum of the charging path for the condenser  13  and the internal resistance of the condenser  13  is represented by “R”, a time when a charging electrical potential “Vc” of the condenser  13  in the case that a charging electrical pressure is “V” becomes about 0.993 V is represented by “5 CR”. The ignition control device  17  can calculate a value of “C” from a time of “5 CR” by previously measuring “R” and a potential difference at this time.  
         [0070]     That is, when a value of electrical current which is transmitted to the condenser  13  conforms with the electrical current value of the electrical current which is consumed by the bus  19  before the charging operation is initiated, the completion of charging is detected, the time took for a completion of charging is sought, and the ignition control device judges a capacity of each condenser  13  by computing the capacity from the charging time using a time constant of the condenser  13 .  
         [0071]     Thereby, the capacity of each condenser  13  can be judged accurately, the ignition control device is able to comprehend a diagnostic result ultimately without an increase in the communication specifications or cost.  
         [0072]     Thus, when the ignition control device  17  which conducted the capacity diagnosis of the condenser  13  judges the completion of charging of the condenser  13 , the connection of switch  22  is switched from the terminal  23   c  to the terminal  23   d  by the electrical signal, and the path C is formed.  
         [0073]     Thereby, for the condenser  13  to which the initial charging is finished, a small quantity of invariable electrical current is drawn in the stationary charging circuit  21  from the bus  19 .  
         [0074]     Furthermore, the process as mentioned above is performed for each condenser  13  of each squib  1 , successively.  
         [0075]     That is, a performance that after the initial charging for a condenser  13  of one squib  1  is finished, the initial charging for a condenser  13  of the other squib  1  begins is conducted, successively.  
         [0076]     By conducting the above operation, finally, the path C which conduct the stationary charging are formed for all squibs  1 .  
         [0077]     As mentioned above, because in the case of charging each condenser  13 , the ignition control device  17  conducts the supply of electrical current for charging to each condenser  13  successively, thereby the charging for all condensers  13  is finished, the amount of initial charge electrical current for the condenser  13  can be regulated regardless of an increase and a decrease of the number of squibs  1 , and a safe design for preventing the initial charge electrical current from operating as input electrical current can be easily conducted.  
         [0078]     Moreover, as a result of an electrical current limitation circuit in the ignition control device  17  not being necessary to modify specifications regardless of an increase and a decrease in the number of the squibs  1 , an primary advantage of using the bus can be derived, and an increase in cost due to an increase in useless specifications can be avoided.  
         [0079]     Furthermore, when the charging initiation is detected, the path which makes it possible to charge quickly is formed, thereby rapid and safe charging can be conducted.  
         [0080]     In addition, because the ignition control device  17  can directly diagnose a capacity of each condenser  13 , the cost for providing a capacity diagnosis circuit at the side of the condenser  13  or for causing the need to transmit diagnosis results due to the communication and the like is not necessary.  
         [0081]     Moreover, a diagnosis of short breakdown in addition to a capacity diagnosis of the condenser  13  can be conducted.  
         [0082]     In addition, a content of the present invention is not limited to the embodiment as mentioned above.  
         [0083]     For example, it is not necessary to use the condenser  13  as the storage device. Other storage devices such as a battery and the like may be used.  
         [0084]     Moreover, the condenser  13  does not need to be built in the squib  1 , and may be attached to the squib  1  via the connecter  28  as shown  FIG. 5 .  
         [0085]     While preferred embodiments of the invention have been described and illustrated above, it should be understood that these are exemplary of the invention and are not to be considered as limiting. Additions, omissions, substitutions, and other modifications can be made without departing from the spirit or scope of the present invention. Accordingly, the invention is not to be considered as being limited by the foregoing description, and is only limited by the scope of the appended claims.
A charging method for a plurality of squibs which charges up each storage device built in or attached to each squib which is connected to an ignition control device via a common bus, and can be selectively operated by electrical energy and electrical signals which are supplied from the ignition control device, in which, in the case of charging each storage device, the ignition control device carries out a direction of charging initiation, an electric power supply for charging, and a direction of charging stop for each storage device successively, thereby the charging for all storage devices is completed.