Abstract:
A gas generator for an air belt apparatus and an air belt apparatus that secures operation safety over years is provided.  
     A gas generator  1  for an air belt apparatus which is used in an air belt apparatus for inflating an air belt by introducing a gas discharged from the gas generator, comprising a solid gas generating agent to be burnt and generate at least one of a gas and a heat and a housing accommodating the solid gas generating agent, wherein the housing is provided with a gas discharging port  2  for discharging a gas generated inside, and the gas discharging port discharges a gas in the radial direction of the housing.

Description:
FIELD OF THE INVENTION  
         [0001]    The present invention relates to an apparatus to protect a vehicle occupant in a moving body such as a vehicle, an aircraft, and a high-speed ship at the time of collision of a vehicle and so on, and particularly relates to an air belt apparatus which is equipped by a vehicle occupant like a seat belt and is inflated by a gas from a gas generating device.  
         BACKGROUND OF THE INVENTION  
         [0002]    An air belt apparatus inflates at least part of a belt portion in a seat belt apparatus (in particular, part attaching to a body of a vehicle occupant) in a collision or a rollover of a vehicle. Usually this apparatus is provided with an air belt introducing a gas into the belt to inflate, and also includes a gas generator supplying a gas into the air belt, and the gas generator is provided to activate at a vehicle collision and so on.  
           [0003]    An air belt apparatus for a vehicle is disclosed, for example, in JP-A No. 5-85301 (U.S. Pat. No. 5,346,250) and so on. In the apparatus disclosed in this document, one end of an air belt is connected to a tongue, a gas flowing passage is provided in each of the tongue and a buckle receiving the tongue, and a gas is introduced into the air belt through the gas flowing passage. And these gas flowing passages are connected by inserting the tongue into the buckle.  
           [0004]    Once such an air belt apparatus is installed in a vehicle, it is usually used for years afterwards, and therefore, it has to activate unfailingly even after used for years.  
           [0005]    However, it is the fact that an air belt apparatus which solves an adverse effect occurring in a use over years has not been provided yet.  
         SUMMARY OF THE INVENTION  
         [0006]    Thus, the present invention recognizes an adverse effect occurring in a use over years and further provides a means to solve this adverse effect. More concretely, in a conventional air belt apparatus, there is such a possibility that, in a use over years, a gas flowing passage (that is, a conduit) is clogged by a foreign material and a gas discharging port of a gas generator is closed. In this case, a gas generated in the gas generator cannot be discharged ordinarily, so that a gas generator may explode. Particularly in a gas generator in which a gas discharging port is closed by a closing member (such as a seal tape, a rupturing disk) and the closing member is ruptured by the increased inner pressure of the housing (wherein the inner pressure of the housing can be increased by generating a gas or heat) to release a gas, the inner pressure of the housing rises temporarily. So, if a gas discharging port of the gas generator is clogged by a foreign material at the time when the closing member should be ruptured, the housing itself of the gas generator can be broken. Therefore, focusing attention on this problem, the present invention provides a gas generator for an air belt apparatus and an air belt apparatus in which such an adverse effect that a gas generator explodes at the time of activation in a use over years cannot be obtained and operational safety can be secured.  
           [0007]    Incidentally, in JP-A No. 2001-322522, there is disclosed an art for reducing pressure load added to a member like an air belt, which prevents a stress added to an air belt from becoming too high when a gas pressure from a gas generator is excessively high. However, this does not solve the problem derived in a use over years. Practically, in the structure described in this document, a gas cannot be released if an introducing pipe (in particular, in the vicinity of a gas discharging port) is clogged with a foreign material, and thereby, explosion of the gas generator cannot be avoided.  
           [0008]    Such a danger that a gas generator can explode because of a foreign material clogging the inside of a gas flowing passage (that is, a conduit) in a use over years to close a gas discharging port of a gas generator is recognized, and the cause thereof is studied, thereby obtaining the present invention.  
           [0009]    In other words, the present invention can solve this problem by investigating the cause of the clogging the gas flowing passage (that is, a conduit) in a use over years and reaching such a conclusion that, in a conventional gas generator, a gas is discharged in the axial direction of the housing and the discharged gas passes through a substantially cylindrical discharging pipe (or a conduit) which is provided in the discharging direction of the gas, and thereby, the gas discharging port or the discharging pipe (or a conduit) is clogged by a foreign matter, and a gas cannot be released in case of being clogged. Therefore, in the gas generator and the air belt apparatus according to the present invention, a direction of discharging a gas discharged from the gas generator (to inflate an air belt) and a structure in the vicinity of the gas discharging port are improved.  
           [0010]    Thus, the gas generator for an air belt apparatus of the present invention is a gas generator used in an air belt apparatus for inflating an air belt by introducing a gas discharged from the gas generator, and comprises a solid gas generating agent to be burnt and generate at least one of a gas and a heat, and a housing accommodating the solid gas generating agent, wherein the housing is provided with a gas discharging port for discharging a gas generated inside, and the gas discharging port discharges a gas in the radial direction of the housing.  
           [0011]    Since the gas discharging port discharges a gas in the radial direction of a housing, a danger of a gas discharging port clogged with a foreign material can be avoided as much as possible. Also, even if a foreign material enters in the axial direction of a gas generator and clogs a conduit (a discharging pipe or an introducing pipe) for a gas to flow, the gas is discharged radially from the gas discharging port, so that it is easy to secure another flowing passage (an escape) other than the normal flowing passage (that is, a flowing passage passing through the conduit) by, for example, a means described below. And by securing such another flowing passage (an escape), an unusual increase in a pressure inside the gas generator can be avoided.  
           [0012]    Also, the safety at the time of distribution and assembling of the gas generator can be obtained by making a gas discharged into the radial direction of the gas generator. Namely, in the present invention, by circumferentially arranging gas discharging ports, which discharges a gas radially, at equal intervals, or at least by arranging each gas discharging port at a position to counteract drifting power of the discharged gas, an erroneous activation of the gas generator and a displacement of the gas generator due to drifting power of the discharged gas can be avoided. In order to make this effect more remarkable, it is preferable to arrange the conduit at the final stage in assembly of an air belt apparatus.  
           [0013]    The escape for a gas discharged radially can be secured by disposing the conduit directly connected to the gas generator housing such that its end portion covers and faces the gas discharging port, and, in addition, by forming a gas pressure releasing means in the conduit for releasing a gas inside the conduit when the inner pressure of the conduit at least in the vicinity of the gas discharging port is not less than a given pressure value.  
           [0014]    The conduit which is directly connected to the gas generator housing is the conduit which receives first the gas discharged from the gas generator, and it includes a conduit which is connected through a sealing member such as an O-ring or a connecting structure other than a conduit (e.g. a flange member), as well as a conduit contacting the gas generator housing. Such a conduit corresponds to an introducing pipe when the gas discharged from a gas generator is introduced into an air belt directly through an introducing pipe. And such a conduit corresponds to a discharging pipe when the gas discharged from the gas generator is introduced into an introducing pipe through a discharging pipe connecting to the gas generator. A gas pressure releasing means can also be provided with a discharging pipe.  
           [0015]    The gas pressure releasing means is a structure or a member which deforms or opens by the pressure inside the pipe increased due to a gas discharged from the gas generator when the conduit (which indicates “an introducing pipe or a discharging pipe”, hereinafter) is clogged with a foreign material, and operates when the inner pressure of the conduit in the vicinity of a gas discharging port is not less than a given pressure value, in other words, when a foreign material is clogged in the conduit to increase the inner pressure of the conduit up to a predetermined pressure (PX) and over.  
           [0016]    Usually at the initial stage of a gas flowing from the gas generator into the conduit, the inside pressure of the conduit increases temporarily (the pressure at this time is referred to as PY). However, the inside pressure of the conduit (PY) decreases as the gas flows towards the air belt. So, a gas pressure releasing means in the present invention is formed to operate when at least a relational expression of PY&lt;PX is met, although depending on output performance of a gas generator. That is, the gas pressure releasing means in the present invention is formed to operate at the pressure (that is, PX) exceeding a pressure (PY) increasing temporarily in the conduit. The reason is that, if a gas pressure releasing means operates at a pressure not more than this pressure (PY), the function of an air belt apparatus cannot be secured.  
           [0017]    Such a gas pressure releasing means can be formed, for example, as follows.  
           [0018]    That is, a conduit which is connected directly to the gas generator housing is formed substantially tubular, the end portion in the side covering the gas discharging port is formed as a flange portion of an inward flange shape, and the conduit is disposed such that a tip end of this flange portion contacts the gas generator housing. And a gas can escape through the gas releasing space by making a portion in the vicinity of the flange portion in the conduit deform with the inner pressure of the conduit being not less than a given pressure value (PX), and by forming a gas releasing space between the housing and the conduit. In this case, the flange portion can be formed to deform by itself. In case of forming in this way, in order to secure the deformation due to the inner pressure of the conduit being not less than a given pressure value, a thickness, a material, a size of each portion, and a shape of this conduit are adjusted so that it operates at the pressure (PX) inside the conduit not less than the pressure (PY) which increases temporally, and further thereby, this does not deform by the discharging pressure (PZ) of a gas from gas discharging ports but deforms only by the inner pressure (PX) in the conduit being not less than a given pressure value.  
           [0019]    It is also possible that a conduit, which is directly connected to the gas generator housing, is formed tubular and a fragile portion is formed on the circumferential surface such that this fragile portion is broken due to the inner pressure of the conduit being not less than a given pressure value (PX). Such a fragile portion can be formed, for example, by providing a notch or a nick on the circumferential surface of the conduit existing near a gas discharging port, or by forming an opening portion in the vicinity of a gas discharging port in the conduit and covering this opening portion with a thin film made of metal and so on. In case of forming in this way, a depth of a notch or a size of a nick, and an opening diameter or strength of thin film have to be adjusted to open due to the inner pressure of the conduit being not less than a given pressure value (PX).  
           [0020]    In addition, a gas pressure releasing means can be formed by a configuration in which the inner pressure of the conduit increased up to a given pressure value (PX) and over is released by rupture of a portion in the vicinity of a gas discharging port in the conduit when the inner pressure of the conduit reaches the given pressure value (PX) and over.  
           [0021]    Thus, a gas pressure releasing means formed in a gas generator operates at a higher inner pressure of the conduit (PX) than an inner pressure of the conduit (PY) increased temporarily in activation of a gas generator, or a discharging pressure (PZ) of a gas from a gas discharging port.  
           [0022]    In the above gas generator of the present invention, in a normal operation, that is, in an operation with no clogging inside the conduit, when a gas is released radially from a gas discharging port, it strikes an inner circumferential surface of the conduit, is changed in the flowing direction thereof, and normally passes through the conduit. Therefore, between a gas discharging port and the inner circumference surface of the conduit, it is necessary to secure a space for a gas flowing. Thus, in the gas generator of the present invention, in order to secure a space for a gas flowing between a gas discharging port and the inner circumference surface of the conduit, desirably, a portion of the gas generator, in which a gas discharging port is formed, is formed to have a smaller outer diameter than a main body of the gas generator housing (a portion accommodating a gas generating agent). In this sense, a structure in which a housing has a tubular shape and a gas discharging port is arranged at one end portion is desirable.  
           [0023]    In the gas generator related to the present invention, it is necessary to accommodate a gas generating agent, which generates at least a gas or heat by combustion, inside the housing. By accommodating such a gas generating agent, in an operation, an inner pressure of the housing increases to be not less than a given pressure value. Furthermore, in this housing, a pressurized gas to inflate an air belt can be filled other than a gas generating agent. Also, the gas generator can include only a pressurized gas.  
           [0024]    Also, in this gas generator, as to arranging an activating device for burning a gas generating agent (e.g. an igniter and so on), or having a structure preventing the outside air from entering into the housing before activation of the gas generator (for example, a member closing a gas discharging port), an conventionally known structure can be adopted.  
           [0025]    The above gas generator is used together with an air belt which inflates by introducing gas, thereby comprising the air belt apparatus of the present invention. In manufacturing of this air belt apparatus, the conduit directly connected to the gas generator housing can be used either as a component of an air belt apparatus or as a component of the gas generator. In addition, the above conduit may be a component of an air belt.  
           [0026]    As to necessary components and structures, which are used in manufacturing of an air belt apparatus, such as an air belt, conventional arts can be employed except for a gas generator and the conduit directly connected to the gas generator.  
           [0027]    Since the gas generator for an air belt apparatus of the present invention composed as described above discharges a gas in the radial direction of a housing, even when a conduit is clogged with a foreign material and a flowing passage does not work properly, another flowing passage can be secured.  
           [0028]    Particularly, in a gas generator provided with a conduit, when the inner pressure of the conduit increases unusually, an escape of a gas can be formed by deforming or cutting part of the conduit, and so on.  
           [0029]    As the result, even when the gas flowing passage (that is, the conduit) is clogged with a foreign material and a gas discharging port of a gas generator is clogged in a use over years, unusual pressure increase in a gas generator is prevented and an inconvenience such as explosion of a gas generator housing can be avoided. Accordingly, a gas generator for an air belt apparatus and an air belt apparatus that secures operation safety over years is provided.  
           [0030]    Also, the gas generator of the present invention discharges a gas in the radial direction thereof, so that, even though it operates erroneously in distribution or assembling of a gas generator, drifting power of the discharged gas is counteracted. Therefore, a gas generator is prevented from launching off, and safety in distribution and assembling can also be obtained. 
       
    
    
     BRIEF DESCRIPTION OF THE DRAWINGS  
       [0031]    [0031]FIG. 1 is an obliquely observed view of an essential part showing an air belt apparatus of the first embodiment.  
         [0032]    [0032]FIG. 2 is a principal cross section showing an operation in an air belt apparatus of FIG. 1.  
         [0033]    [0033]FIG. 3 is a principal cross section showing an operation state in a gas pressure releasing means.  
         [0034]    [0034]FIG. 4 is an obliquely observed view of an essential part showing another example of a gas pressure releasing means.  
         [0035]    [0035]FIG. 5 is an obliquely observed view of an essential part showing an air belt apparatus related to another embodiment. 
     
    
     DESCRIPTION OF NUMERALS  
       [0036]    [0036]                                       1   gas generator       2   gas discharging port       3   inserting pipe       4   flange portion       5   notch       6   discharging pipe       7   sealing member       10   air belt       X   buckle       Y   tongue       Z   foreign material                    
       DESCRIPTION OF PREFERRED EMBODIMENTS  
       [0037]    The present invention is explained below based on the embodiments shown in the drawings.  
         [0038]    [0038]FIG. 1 is an obliquely observed view of an essential part showing an air belt apparatus of the first embodiment. FIG. 2 is a principal cross section showing an operation in an air belt apparatus of FIG. 1. FIG. 3 is a principal cross section showing an operation state in a gas pressure releasing means. FIG. 4 is an obliquely observed view of an essential part showing another example of a gas pressure releasing means. FIG. 5 is an obliquely observed view of an essential part showing an air belt apparatus related to another embodiment.  
         [0039]    In an air belt apparatus shown in FIG. 1, an air belt  10 , which introduces a gas into an belt portion restraining a vehicle occupant to inflate, is arranged, and a tongue Y is connected to this belt portion (or an air belt  10 ). And, in this tongue Y, as a conduit to introduce a gas from a gas generator  1  and to lead the gas to an air belt  10 , an introducing pipe  3  is provided.  
         [0040]    Meanwhile, in a buckle X extending from a floor or a seat of a vehicle, a gas generator  1 , which receives an operation signal and generates a gas to inflate an air belt  10 , is provided. This gas generator  1  is provided with gas discharging ports  2  to discharge a gas generated by combustion of a gas generating agent (not shown) (or by inflation due to heat of combustion), and the gas discharging ports  2  are arranged at equal intervals on a circumferential surface of the end portion side in a housing of the gas generator  1 .  
         [0041]    And, a flange portion  4  of inward flange-like shape is formed at an end portion of the introducing pipe  3  in the gas generator side, and, when the tongue Y is inserted into the buckle X, the inner circumferential surface of this flange portion  4  contacts an outer circumferential surface of a housing (an shell container) of a gas generator  1 . At this time, a gas discharging port  2  necessarily exists in an introducing pipe  3 .  
         [0042]    In an air belt apparatus comprising as described above, in a use over years, even when a foreign material Z enters an introducing pipe  3  and a gas flowing passage is clogged as shown in FIG. 2( a ), a gas is discharged from the gas generator  1  in the radial direction, so that an escape to another direction (in the drawing, to the diagonally backward direction) can be secured as shown in FIG. 2( b ). As the result, since unusual pressure increase in a gas generator housing is prevented, a housing is prevented from exploding.  
         [0043]    As a structure of an air belt  10  itself in an air belt apparatus shown in FIG. 1, a conventionally known art such as described in JP-A No. 2001-322522 can be employed, and also as to the inner structure of a gas generator  1 , for example, a gas generating agent or a structure of an ignition means which activates upon receiving an operation signal and burns the gas generating agent (such as an igniter), conventionally known art can also be used. Therefore, in the present embodiment, a detailed description is omitted. Furthermore, also as to an apparatus for sending an operation signal to an ignition means included in a gas generator  1  (such an igniter), conventionally known art can be used, so that, in the present embodiment, a detailed description is omitted.  
         [0044]    In FIG. 2( b ), a portion in the vicinity of a flange portion  4  is to be deformed upon receiving a pressure being not less than a given pressure value and to form a space for releasing a gas, and thus the portion in the vicinity of a flange portion  4  in a introducing pipe  3  to be deformed by a pressure is a gas pressure releasing means. In this embodiment, this introducing pipe  3  (that is, a conduit) is formed in a cylinder made of stainless steel, in order to obtain deformation of the portion in the vicinity of flange portion  4  with such a gas pressure. As the result, it does not deform by the gas pressure discharged from a gas discharging port  2 , but deforms only by the pressure in an introducing pipe  3  when an introducing pipe  3  is clogged.  
         [0045]    Also, when a gas releasing means is formed, the introducing pipe  3  in the gas generator side is made tubular and the end portion thereof is provided with a sealing means  7  such as an o-ring as shown in FIG. 3, without forming a flange portion  4  as shown in FIG. 1. In this case, the sealing means  7  closely joins to a housing of a gas generator  1  and seals between an introducing pipe  3  and a gas generator  1 . When an introducing pipe is formed in this way, a certain volume of space for realizing gas circulation also needs to be secured between a gas discharging port  2  and an introducing pipe  3 . When, in the gas generator  1  shown in FIG. 3( a ), the introducing pipe  3  is clogged by a foreign material Z and the inner pressure of the introducing pipe  3  increases up to a given pressure value and over, as shown in FIG. 3( b ), a portion in the vicinity of a surface, which faces a gas discharging port  2 , in the introducing pipe  3  is bent and a flowing passage for releasing a gas can be formed.  
         [0046]    In addition, a gas pressure releasing means can be formed to face a gas discharging port  2  in an introducing pipe as a fragile portion. For example, as shown in FIG. 4, in such a state that a gas generator  1  and an introducing pipe  3  are connected, a nick  5  which deforms and opens only by a pressure inside the introducing pipe  3  generated when the introducing pipe  3  is clogged, can be formed as a fragile portion in a portion in the vicinity of a surface which faces a gas discharging port  2 . In this case, the nick portion  5  opens by unusual pressure increase in the introducing pipe  3  and the pressure in the introducing pipe  3  is released.  
         [0047]    Further, a gas pressure releasing means can be formed by forming a port in a portion in the vicinity of a surface, which faces a gas discharging port, in an introducing pipe and closing the port with a metallic foil such as a seal tape to be ruptured by a pressure being not less than a given pressure value in the introducing pipe. The pressure at which a metallic foil is ruptured can be adjusted by opening diameter or opening area of a port, number of ports, material or thickness of metallic foil, and so on.  
         [0048]    When a gas pressure releasing means is formed by using a fragile portion or a metallic foil, desirably, it is formed not to receive a gas from a gas discharging port directly.  
         [0049]    In air belt apparatuses shown in above FIG. 1 to  4 , when an introducing pipe  3  is not clogged (that is, normal state), the gas discharged radially from a gas discharging port  2  passes through a space between a gas discharging port  2  and an inner circumferential surface of an introducing pipe  3 , and passes inside an introducing pipe  3  in the length direction thereof.  
         [0050]    Although, in the air belt apparatuses shown in FIGS.  1  to  4 , the introducing pipe  3  constituting part of an air belt  10  is directly connected to a gas generator  1 , however, such an embodiment can be employed that a discharging pipe  6 , that is a conduit directly connected to a gas generator  1  housing and connecting a gas generator  1  and an introducing pipe  3 , as shown in FIG. 5. In this case, the embodiment of the above gas pressure releasing means, that is, the portion in the vicinity of a flange portion  4 , which deforms due to a gas pressure being not less than a given pressure value, is arranged in the discharging pipe  6  (that is, the conduit which is directly connected to a housing of a gas generator  1 ).  
         [0051]    Thus, the air belt apparatus of an embodiment shown in FIG. 5 is the same as that shown in the above FIG. 1 in arranging an introducing pipe  3  in a tongue Y provided in an belt portion of a seat belt (or an air belt  10 ), and in arranging a gas generator  1  in a buckle X extending from a floor or a seat of a vehicle. However, the embodiment shown in FIG. 5 is different from the air belt apparatus shown in above FIG. 1 in that a gas generator  1  and an introducing pipe  3  are connected via a discharging pipe  6 , and that an introducing pipe  3  is not directly connected to a gas generator  1 .  
         [0052]    In an air belt apparatus shown in this embodiment, since one end of a discharging pipe  6  is directly connected to a gas generator  1 , a gas pressure releasing means is arranged in a portion connected to a gas generator  1  inside the discharging pipe  6 . Naturally, a gas pressure releasing means may be formed in an introducing pipe  3  connected to an opposite side end portion of a discharging pipe  6 .  
         [0053]    In an air belt apparatus comprising as described above, even when a foreign material Z enters into an introducing pipe  3  or a discharging pipe  6 , and a pressure near a gas discharging port  2  increases unusually, a gas pressure releasing means arranged in this discharging pipe  6  operates to release gas. Therefore, a gas generator  1  shown in this embodiment can also prevent unusual pressure increase in a housing and a gas generator  1  housing can be prevented from exploding.