Patent Publication Number: US-2004041382-A1

Title: Inflator with a cap

Description:
TECHNICAL FIELD TO WHICH THE INVENTION BELONGS  
       [0001] The present invention relates to an inflator with a cap suitable as an inflator for a curtain air bag, an inflator for a side collision air bag or the like for an automobile or the like, and an air bag apparatus using the inflator with a cap.  
       BACKGROUND ART  
       [0002] As an inflator for inflating type safety system of an automobile, in order to optimally protect a passenger in accordance with a position of a seat in a vehicle such as driver side, a passenger side next to the driver and the like, there are known various inflators such as an inflator for a driver side, an inflator for a passenger side next to the driver, an air bag inflator for a side collision, an inflator for a curtain air bag, an inflator for a knee-bolster air bag, an inflator for an inflatable seat belt, an inflator for a tubular system and an inflator for pretensioner. Among these inflators, the inflator for a curtain air bag instantaneously inflates and develops the curtain-like air bag having a thickness of several centimeters over windows of a vehicle when the vehicle receives the impact from the side.  
       [0003] As related prior arts, the following documents have been known. For example, a device for inflating a flexible container using helium and hydrogen is disclosed in U.S. Pat. No. 5,527,066, a gas flow device for an air bag using a pressurized inert gas is disclosed in U.S. Pat. No. 5,782,486, an air bag apparatus for inflating an air bag by nitrogen or helium is disclosed in U.S. Pat. No. 3,680,886, a side inflator housing for an air bag using a pressurized gas and a gas generating agent is disclosed in U.S. Pat. No. 5,803,493, and a pressurized gas inflator using argon or nitrogen as a pressurized gas is disclosed in JP-U No. 3031246.  
       [0004] It is demanded that various inflators are reduced in size and weight because of the demands of reducing weight on the vehicle itself, and, additionally, it is demanded to improve workability, simplify the manufacturing process and improve safety at a time of actuation. However, the above related prior arts cannot satisfy all the demands completely.  
       DISCLOSURE OF THE INVENTION  
       [0005] An object of the present invention is to provide an inflator with a cap which can achieve reduction in size and weight, can improve workability and can facilitate the manufacturing process, and an air bag apparatus using the same.  
       [0006] The present invention provides, as one means for solving the above-described problem, an inflator with a cap comprising a cylindrical inflator housing which is closed at one end and has an opening portion at the other end and in which the interior is charged with a pressurized medium, a diffuser portion which is fixed to the opening portion side of the inflator housing and is provided with a first gas discharging port for discharging outside the pressurized medium flowing out of the opening portion at a time of actuation, a rupturable plate closing an outflow path for the pressurized medium between the opening portion of the inflator housing and the diffuser portion, and a rupturing means for the rupturable plate provided at the diffuser portion, wherein a cap which covers at least an outer surface including the first gas discharging port and has an opening portion serving as a second gas discharging port is mounted to the diffuser portion by crimping.  
       [0007] By mounting the cap by the crimping in this manner, the manufacturing process can be facilitated as compared with a case of applying welding or the like. Further, when an air bag is attached to the inflator, such an effect can be obtained that the air bag can be connected and fixed by using the crimped portion.  
       [0008] In the above-described invention, preferably, the cap is a barrel-like member which has minimum diameter portions provided at both ends thereof in the longitudinal direction, a maximum diameter portion provided at the central portion thereof in the longitudinal direction and a stepped portion provided between the minimum diameter portion and the maximum diameter portion, the opening portion serving as the second gas discharging port is provided at the stepped portion or the maximum diameter portion, and the cap is mounted to the diffuser portion at the minimum diameter portion.  
       [0009] By providing the second gas discharging ports at the stepped portion, the maximum diameter portion, or both of the stepped portion and the maximum diameter portion, a distributing space for the pressurized medium can be secured between the first gas discharging port and the second gas discharging port, so that discharging of the pressurized medium can not be blocked.  
       [0010] In the above-described invention, preferably, the cap is mounted by crimping one or both of the minimum diameter portions at a groove provided on a peripheral surface of the diffuser portion. It is desirable that the groove provided on the peripheral surface of the diffuser portion is a continuous groove (a ring groove) provided along the peripheral surface.  
       [0011] By mounting the cap in the groove in this manner, the cap can be fixed to the diffuser portion more firmly, and such an effect can also be obtained that, when the air bag is attached to the inflator, it can be connected and fixed thereto by using the groove (the crimped portion).  
       [0012] In the above-described invention, preferably, the total opening area of the second gas discharging ports is larger than that of the first gas discharging ports, and the total opening area of the second gas discharging ports is 1.5 times or more that of the first gas discharging ports.  
       [0013] By defining the total opening areas of the first gas discharging ports and the second gas discharging ports in this manner, a discharging pressure of the pressurized medium can be controlled by the first gas discharging ports.  
       [0014] In the above invention, plural first gas discharging ports are provided, and it is preferable that at least two of the plural first gas discharging ports are disposed at positions symmetrical to each other in the widthwise direction or positions approximating these positions.  
       [0015] In this invention, a cross-section of the diffuser portion in the widthwise direction is circular, and when two or three or more first gas discharging ports are provided, the positions of at least two first gas discharging ports are disposed symmetrically in the widthwise direction (in the radial direction) or nearly symmetrically. It is preferable that, when three first gas discharging ports are provided, three discharging ports are disposed at an equal angle therebetween of 120°, and when four first gas discharging ports are provided, the four discharging ports are disposed at equal intervals, making the angle of 90°. When five or more discharging ports are provided, the ports are disposed in the same manner as the above.  
       [0016] In the event of such an unexpected situation that fire or the like breaks out at a time of transportation/storage of an inflator to cause malfunction thereof, if only one first gas discharging port is provided, the inflator launches like a rocket by the pressurized medium discharged therefrom, which will cause much danger. As described above, however, when arrangement of at least two first gas discharging ports is adjusted, in some cases, when arrangement of three or four or more first gas discharging ports is adjusted, such an abnormal event can be avoided.  
       [0017] In the above invention, by using a cylindrical inflator housing which is symmetrical in the axial and widthwise directions, workability at a manufacturing time can be improved.  
       [0018] Further, the present invention provides, as one means for solving the above problem, an air bag apparatus comprising actuation-signal outputting means comprising an impact sensor and a control unit, and a module case in which the above-described inflator with a cap and an air bag are accommodated in a case.  
       [0019] The inflator of the present invention can facilitate an assembling work and reduce a burden of a worker, and can enhance connection when an air bag is connected. 
     
    
    
     BRIEF DESCRIPTION OF THE DRAWINGS  
     [0020]FIG. 1 is a sectional view of an inflator of the present invention in the axial direction, and  
     [0021]FIG. 2 is a view for explaining a method of mounting a cap in the inflator shown in FIG. 1. 
    
    
     EXPLANATION OF NUMERALS  
     [0022] 10  inflator  
     [0023] 12  inflator housing  
     [0024] 19  rupturable plate  
     [0025] 20  diffuser portion  
     [0026] 22  first gas discharging port  
     [0027] 25  igniter  
     [0028] 31  ring groove  
     [0029] 40  cap  
     [0030] 45  second gas discharging port  
     PREFERRED EMBODIMENT OF THE PRESENT INVENTION  
     [0031] The following is a description of one embodiment on the present invention with reference to the drawings. FIG. 1 is a sectional view of an inflator  10  of the present invention in the longitudinal direction, and FIG. 2 is a view for explaining a method of mounting a cap by crimping.  
     [0032] An inflator housing  12  has an opening portion  14  at one end and the other end side thereof is closed by swaging, spinning or the like. A pressurized medium comprising an inert gas such as argon or helium or nitrogen gas is charged into the internal space  16  formed by the inflator housing  12  and a diffuser portion  20  at the maximum pressure of about 60,000 kPa. A cross section of the inflator housing  12  in the widthwise direction thereof is circular and the opening portion  14  is circular similarly.  
     [0033] The inflator housing  12  can be made symmetrical with respect to the axial direction and the widthwise direction thereof. After the diffuser portion  20  is connected to the inflator housing  12 , the pressurized medium is charged from a clearance between a thin hole provided at the closed end surface and a sealing pin  17  fitted into the thin hole, and then the thin hole and the sealing pin  17  are welded to be completely closed.  
     [0034] In the opening portion  14  side of the inflator housing  12 , the diffuser portion  20  is connected, and the diffuser portion  20  has a first gas discharging port  22  for discharging the pressurized medium to the outside. The first gas discharging port  22  is not closed, and a screen  29  comprising an annular wire mesh for removing broken pieces of a rupturable plate  19  is disposed inside the first gas discharging ports  22 .  
     [0035] The inflator housing  12  and the diffuser portion  20  may be connected to each other by a welding (a welded portion  26 ) as shown in FIG. 1. Alternatively, they may be connected by screwing a male screw portion provided on an end portion outer peripheral surface of the inflator housing  12  and a female screw portion provided on an end portion inner peripheral surface of the diffuser portion  20 .  
     [0036] An outflow path  18  for the pressurized medium inside the diffuser portion  20  is closed by the rupturable plate  19 , and the internal space  16  of the inflator housing  12  is kept hermetic with a high pressure before actuation.  
     [0037] An igniter  25  provided with a priming is arranged in the diffuser portion  20 , as rupturing means for the rupturable plate  19 . The igniter  25  is mounted after the inflator housing  12  and the diffuser portion  20  are connected to each other, and the igniter  25  is fitted in from the opening portion provided at the one end of the diffuser portion  20  towards the rupturable plate  19 , and thereafter, it is fixed by crimping a peripheral edge  28  of the opening portion provided at the one end of the diffuser portion  20 . The igniter  25  is mounted coaxially with the center axis of the inflator housing  12 .  
     [0038] A cap  40  is mounted to the diffuser portion  20 , such that it covers an outer surface including the first gas discharging ports  22 . The cap  40  is a barrel-like member having the minimum diameter portions  41   a  and  41   b  provided at both sides thereof in the longitudinal direction, the maximum diameter portion  43  provided at the central portion in the longitudinal direction, and stepped portions  42   a  and  42   b  provided between the minimum diameter portions  41   a ,  41   b  and the maximum diameter portion  43 . The cap  40  is crimped at the minimum diameter portion  41   b  to be fixed at a ring groove  31 . It is preferable in view of connectability at the time of mounting an air bag that a flat surface or a recess is provided on an outer surface of the minimum diameter portion  41   a.    
     [0039] A distributing space  46  comprising an outer peripheral surface of the diffuser portion  20 , the stepped portions  42   a ,  42   b , and the maximum diameter portion  43  is formed between the outer peripheral surface of the diffuser portion  20  and the cap  40 . For this reason, after the pressurized medium discharged from the first gas discharging ports  22  flows into the distributing space  46 , it is discharged from the second gas discharging ports  45  provided at the stepped portions  42   a ,  42   b , so that the pressurized medium is discharged from all the second gas discharging ports  45  by equal amounts.  
     [0040] Since the second gas discharging ports provided at the stepped portions  42   a ,  42   b  and the first gas discharging ports  22  do not face each other correctly, the pressurized medium flowing into the distributing space  46  is discharged radially. And, since the discharging direction of the pressurized medium is adjusted according to an inflating and developing direction of an air bag, the second gas discharging ports  22  may be provided on only the stepped portion  42   a  or only the stepped portion  42   b , or they may be provided on only the maximum diameter portion  43 . Alternatively, they may be provided on the stepped portions  42   a ,  42   b  and the maximum diameter portion  43 .  
     [0041] It is preferable that the diameter of the first gas discharging port  22  is made smaller than that of the second gas discharging port  45 , which can similarly be applied to the case that plural discharging ports are provided. For this reason, the total opening area of the second gas discharging ports  45  becomes larger than that of the first gas discharging ports  22 , and the former is adjusted to be 1.5 times the latter.  
     [0042] As the first gas discharging port  22 , it is preferable in view of preventing the inflator  10  from launching like a rocket due to malfunction that two first gas discharging ports  22  are provided symmetrically in the radial direction, for example.  
     [0043] Next, a method for mounting the cap  40  in the inflator  10  will be explained. First, as shown in FIG. 2, the cap  40  is fitted into the diffuser portion  20  from the igniter  25  side to have the minimum diameter portion  41   b  and the ring groove  31  coincided with each other. At this time, an end portion of the minimum diameter portion  41   a  abuts on a portion of the diffuser portion  20  near the opening edge  28 , and an O-ring  30  is disposed at the abutted portion in order to keep hermetic. Thereafter, as shown in FIG. 1, the cap  40  is fixed to the ring groove  31  by crimping a portion of the minimum diameter portion  41   b  of the cap  40  in FIG. 2.  
     [0044] An air bag apparatus using the inflator  10  is one constituted by combining actuation-signal outputting means comprising an impact sensor and a control unit, a module case accommodating the inflator  10  and a curtain-like air bag  50  in the case thereof, and the like, and it can be constituted to have the same constitution as shown in FIG. 17 in JP-A 11-334517.  
     [0045] When an air bag is connected to the inflator  10 , such a method of connecting can be applied that an opening portion of the air bag covers the cap  40  and is fastened by a fixing band at the ring groove  31  (the minimum diameter portion  41   b ) at which the cap  40  is crimped. By fixing the opening portion of the air bag at the ring groove  31  in this manner, connection between the air bag and the inflator  10  can be enhanced. Further, by fastening at the minimum diameter portion  41   a  (where the flat surface or the recess is provided) by a fixing band in the same manner, if required, the connection can further be enhanced.  
     [0046] Next, an operation of the air bag apparatus using the inflator  10  will be explained with reference to FIG. 1. When a vehicle is received the impact, the igniter  25  receives a signal from the impact sensor to be actuated, and the priming is ignited and burnt to rupture the rupturable plate  19 . Since the outflow path  18  for the pressurized medium is opened by rupturing of the rupturable plate  19 , the pressurized medium in the internal space  16  passes through the outflow path  18  and the filter  29  and then flows into the distributing space  46  through the first gas discharging port  22 . Thereafter, the pressurized medium is discharged through the second gas discharging port  45  to inflate the air bag. At this time, broken pieces of the ruptured rupturable plate are removed by the filter  29 .