Abstract:
A safety module for a motor vehicle includes at least one inflatable cushion with a first fixation interface and at least one actuating device. The at least one actuating device includes an igniter and an igniter support. The igniter has a plastic overmolding forming a second fixation interface. The igniter support has a third fixation interface designed to receive and fix the second fixation interface. The at least one actuating device retains the first fixation interface by sandwiching it between at least one part of the second fixation interface and at least one part of the third fixation interface.

Description:
CROSS-REFERENCE TO RELATED APPLICATIONS 
     This application is a 371 U.S. National Stage of International Application No. PCT/EP2014/072887, filed Oct. 24, 2014. This application claims the benefit of and priority to French Patent Application No. 1360455, filed Oct. 25, 2013. The disclosures of the above applications are incorporated herein by reference. 
     FIELD 
     The present invention relates in a general manner to a fixation interface for a pyrotechnical actuator arranged in a safety module for an automobile and in particular a safety module comprising an airbag with a vent, wherein the pyrotechnical actuator is designed to control the vent. 
     BACKGROUND 
     Devices for vent control are known in the prior art such as the one described in the document US20100090445 in which a pyrotechnical actuator is designed to cut a control linkage of an airbag vent. On the other hand, this system has in particular the disadvantage of comprising numerous parts with in particular a cutting blade, which increases the cost and the complexity of the proposed solution. Moreover, the fixation of the linkage is complicated because it is necessary to place the linkage at first into the cutting mechanism in order to then fix it around the pyrotechnical cutting actuator. The mounting operations are complex, which produces a risk of non-conformity. 
     In the case in which the cutting device is replaced by an inflatable cushion which controls the linkage, the fixation of the inflatable cushion is similar to that of the linkage in the above example and the same problems of the complexity of the fixation appear. 
     SUMMARY 
     A goal of the present invention is to respond to the disadvantages of the document of the prior art cited above and in particular, first of all, to suggest a fixation interface for an inflatable cushion which is economical and easy to mount. 
     To this end a first aspect of the invention relates to a safety module for an automobile, which module comprises: 
     at least one inflatable cushion with a first fixation interface; 
     at least one actuating device comprising: 
     an igniter with a plastic overmoulding forming a second fixation interface; 
     an igniter support with a third fixation interface designed to receive and fix the second fixation interface; characterized in that said at least one actuating device is designed to retain the first fixation interface by sandwiching it between at least one part of the second fixation interface and at least one part of the third fixation interface. 
     The present implementation proposes mounting the first fixation interface (that of the inflatable cushion) directly between the igniter and the igniter support. Therefore, the first fixation interface is retained and fixed by this sandwich hold, which permits the localization of the first, the second and the third fixation interface at the same location and simplifies the rest of the structure by accumulating the fixation functions on the same pieces. 
     The igniter is advantageously designed to inflate only the inflatable cushion. In other words, there is no secondary charge outside of the igniter. 
     According to an embodiment the igniter is designed to pressurize the inflatable cushion an absolute pressure of 30 bars maximum. 
     The at least one actuating device advantageously comprises a projecting fourth fixation interface designed to receive at least one eyelet formed in the first fixation interface. The retention and the fixation of the first fixation interface is secured with this projecting part that receives an eyelet of the first fixation interface. Moreover, the sandwich hold prevents the eyelet from exiting from the projecting part, thus making the retention and the fixation of the first interface reliable. According to this implementation the first fixation interface can be slipped onto the fourth fixation interface, which offers a function of prepositioning the inflatable cushion on the actuating device during the mounting. Therefore, the mounting can be broken down into a first stage of prepositioning the inflatable cushion via its first fixation interface followed by a second stage of mounting the igniter or the actuating device on the module, for example. 
     The eyelet is advantageously designed to be mounted tightly on the fourth fixation interface. According to this implementation the prepositioning is more robust. 
     The third fixation interface advantageously comprises a fixation orifice, the first fixation interface comprises at least one inflatable cushion tongue on which said at least one eyelet is arranged, and said at least one tongue is inserted into the fixation orifice of the igniter support. The passage of the tongue into the third fixation interface (which will therefore receive the second fixation interface of the igniter) also secures the fixation of the inflatable cushion. 
     The igniter advantageously has an axial direction, the fourth fixation interface is formed by two indices arranged in a dissymmetric manner relative to the axial direction of the igniter in order to offer an angular keyway between the igniter and the igniter support, and the first fixation interface comprises two eyelets, each designed to be mounted tightly on one of the two indices. The axial direction can be defined, for example, by an axis of symmetry of an ignition case or by a direction of connection pins of the igniter. The fourth fixation interface is advantageously used to offer an angular keyway between the igniter and the igniter support, which reduces the risks of an incorrect mounting. 
     The indexes are advantageously arranged on the igniter support and the igniter comprises recesses arranged to receive the indexes. This reduces the risk of the inflatable cushion escaping during its deployment since the degrees of freedom of the tongues are limited in this manner and ensure a keyway of the inflatable cushion relative to the igniter support. 
     The safety module advantageously comprises: 
     an airbag with a vent, 
     a linkage connecting the inflatable cushion and the vent. 
     The linkage connected to the inflatable cushion advantageously keeps the vent closed, the linkage is designed to detach itself from the inflatable cushion when the latter is inflated, and the igniter, when it is ignited, is designed to inflate the inflatable cushion. 
     The linkage advantageously is connected to the inflatable cushion by a meltable seam designed to break during an inflation of the inflatable cushion caused by an ignition of the igniter. 
     The igniter advantageously has a direct communication with the inflatable cushion. In other words, the igniter traverses the igniter support in order to deliver the inflation gases directly into the inflatable cushion. 
     The second fixation interface advantageously comprises clipping means on the igniter support. 
     The clipping means advantageously comprises at least one deformable part designed to elastically deform during the mounting of the igniter on the igniter support and to assume by elastic return a position of blocking against the igniter support when the igniter is in mounted position for preventing any withdrawal of the igniter. 
     The igniter advantageously comprises elongated connection pins and the plastic overmoulding forms at the level of the connection pins a connection imprint designed for receiving and retaining a connector. The connector is advantageously a male connector. 
     The igniter advantageously comprises: 
     at least one pyrotechnical material designed to be ignited by a heating element, 
     a case enclosing said at least one pyrotechnical material and arranged in a pit of the plastic overmoulding, 
     elongated connection pins, and the pit has an axial direction substantially parallel to the connection pins. 
     The case advantageously comprises a lateral wall and a bottom with a thickness greater than that of the lateral wall. The risks of rupture and/or of detachment of the case petals during the functioning of the igniter causing an opening under great pressure on the case are reduced with this implementation. This furthermore permits the limiting of the angular amplitude of the opening of the petals and the inflation of the case and therefore the reducing of the stresses on the plastic overmoulding during the igniting of the igniter. 
     The case advantageously comprises a bottom comprising weakened lines designed to bring about a petalling of the bottom during the functioning of the igniter, and the number of petals is less than eight. This implementation improves the resistance to rupture of the petals during the functioning. 
     The pit advantageously has a depth greater than or equal to one half the diameter of the case. This will prevent the petals from exceeding the overmoulding pit and therefore any attack on an element outside of the pyrotechnical igniter such as an airbag tissue. 
     Said at least one deformable part advantageously has a blocking face on the support and the pit has an end for the exit of the gases of the igniter arranged at a distance from said upper blocking face or equal to 15 millimeters. This implementation allows leaks to be limited by the fixation of the igniter on the support. 
     The pit advantageously has a depth comprised between 5 and 10 millimeters, terminals included. 
     The pit advantageously has a diameter two to three millimeters greater than that of the case. The deployment of the petals is optimal with this implementation: the petals do not support themselves on the pit during their opening and therefore do not risk damaging it. This furthermore allows the realization of a moulding tool for realizing the plastic overmoulding which is sufficiently massive for avoiding any erosion during the injection and therefore for avoiding any premature wear of the mould. Finally, this allows the igniter to be correctly held during the operation of overmoulding and therefore allows pieces of constant dimensions. 
     The igniter advantageously comprises a cross-connector of glass to which the case is fixed by a welding and said at least one deformable part is arranged on the plastic overmolding facing a case zone between the welding and the case bottom. During the operation of the igniter the case has a tendency to inflate above the welding with the cross-connector of glass. The maximum deformation and therefore the maximum stress of the overmolding will be found at the level of the contact zone between the case and the overmolding, between the welding and the case bottom. According to this implementation, facing this zone, the deformable part or parts also act as reinforcement ribs. 
     The welding is advantageously arranged to be facing the support when the igniter is in the inserted position. The support participates in the resistance of the welding and supplies it with a recovery of stress. 
     The plastic overmoulding is advantageously made of polyamide 6.6 with 30% by mass of glass fibres. 
     Advantageously, according to one embodiment 
     the igniter support comprises a checking opening, 
     the deformable part comprises a male part of which a first part faces the checking opening when the deformable part has passed into the blocking position. This implementation allows a check of the presence of the deformable part after mounting. 
     The male part advantageously comprises a second part, with a greater surface than the first part, which faces the checking opening when the igniter is in the inserted position with the deformable part remaining deformed. This implementation allows a check to be made that the deformable part is in a good blocking position after insertion. 
     The module advantageously comprises a casing and the igniter support is a part of the casing. The general structure of the module is simplified. 
     According to an embodiment the airbag is designed to retain an occupant of the vehicle during a collision and the inflatable cushion is designed to carry out an order of a mechanism of the safety module. 
     A second aspect of the invention is an automobile comprising at least one safety module according to the first aspect of the invention. 
    
    
     
       DRAWINGS 
       Other characteristics and advantages of the present invention will appear more clearly from a reading of the detailed following description of an embodiment of the invention given by way of a non-limiting example and illustrated by the attached drawings, in which: 
         FIG. 1  shows a safety module according to the present invention in a first configuration of deployment; 
         FIG. 2  shows the safety module of  FIG. 1  in a second configuration of deployment; 
         FIG. 3  shows an exploded view of a pyrotechnical actuating device and of an inflatable cushion of the safety module of  FIG. 1 ; 
         FIGS. 4, 5 and 6  each show a stage of the mounting of the pyrotechnical actuating device and of the inflatable cushion of  FIG. 3 ; 
         FIG. 7  shows a detail of the igniter support and of the igniter inserted in the igniter support according to three mounting scenarios; 
         FIG. 8  shows a view of a section of the igniter. 
     
    
    
     DETAILED DESCRIPTION 
       FIG. 1  shows a safety module for an automobile comprising an airbag  10 , a gas generator  20  designed to inflate the airbag  10 , a pyrotechnical actuating device  30  (comprising an igniter  31  and an igniter support  32 ) and an inflatable cushion  40  connected to a vent  11  of the airbag  10  by a linkage  41 . 
     As is shown, the airbag  10  is deployed under the action of inflation gases generated by the gas generator  20 . A pressure P 1  prevails in the airbag  10 , calculated for example to retain and cushion an occupant during a collision of the automobile with an obstacle. Under certain collision conditions or during a certain lapse of time during the retention of the occupant the pressure should be maintained in the airbag  10  and the vent  11  should remain closed. To this end the linkage  41  keeps it closed and it is kept stretched by the inflatable cushion  40 . 
       FIG. 2  shows the safety module of  FIG. 1  with the vent  11  open. In fact, under certain collision conditions if the occupant is detected outside of his normal position or at the end of the retention of the occupant it can be important to lower the pressure in the airbag  10 . This is when the actuating device  30  is activated in order to inflate the inflatable cushion  40  in order to release the linkage  41  which is no longer stretched and allows the vent  11  to open in order to obtain a pressure P 2  lower than P 1 . 
     The igniter  31  of the actuating device  30  has inflated the inflatable cushion  40  and a meltable seam  42  (visible in  FIG. 1 ) has broken, thus freeing the linkage  41 . 
       FIG. 3  shows an exploded view of the igniter support  32 , of the inflatable cushion  40  and of the igniter  31 . The inflatable cushion  40  comprises two tongues  40   a , each of which carries an eyelet  40   b , all together forming a first fixation interface. 
     The igniter  31  comprises a cylinder  31   b  and two feet  31   a . The feet  31   a  are deformable parts of the plastic overmoulding forming the body of the igniter  31 . The cylinder  31   b  and the feet  31   a  form a second fixation interface. 
     The igniter support  32  comprises a fixation orifice  32   a  and two slots  32   c  which form a third fixation interface designed to receive and fix the second fixation interface of the igniter  31  (the cylinder  31   b  engages into the fixation orifice  32   a  and the feet  31   a  deform elastically during the insertion into the slots  32   c  in order to go into a position of blockage against the igniter support  32  once the igniter  31  has been completely inserted into the igniter support  32 ). The feet  31  move into a position of blockage by elastic return at the level of a shoulder (not visible) in each slot  32   c.    
     The igniter  31  advantageously comprises connection pins which are perpendicular to the shoulders so that the stresses caused by the putting in place and/or the withdrawal of a connector are exerted in an axial direction of the feet  31   a.    
     The igniter support  32  also comprises two indexes  32   b  forming a fourth fixation interface designed to receive the eyelets  40   b  of the first fixation interface. In fact, prior to the insertion of the igniter  31  the tongues  40   a  are inserted into the fixation orifice  32   a  and the eyelets  40   b  are forcefully threaded onto the indexes  32   b . Therefore, the inflatable cushion  40  is pre-positioned on the igniter support  32  and the insertion of the igniter  31  sandwiches the first interface of the inflatable cushion  40  between a part of the second fixation interface (the cylinder  31   b ) and the third fixation interface (the fixation orifice  32   a ). 
       FIG. 4  shows the igniter support  32  before any operation of mounting. It shows the igniter support  32  in detail, which comprises the fixation orifice  32   a  and the two slots  32   c  which form the third fixation interface, as well as two indexes  32   b  which form the fourth fixation interface. 
     It is also possible to note the presence of a bevel on the ridge of the fixation orifice  32   a  caused to be brought in contact with the second fixation interface of the igniter, which can also be bevelled in this zone in order to improve the relative positioning of the two components, and also to increase the tightness during functioning. 
       FIG. 5  shows the igniter support  32  with the inflatable cushion  40  pre-positioned on top. To this end the eyelets  40   b  were installed on the indexes  32   b  with the tongues  40   a  moved inside the fixation orifice  32   a.    
       FIG. 6  shows the last stage of the assembly with the igniter  31  inserted into the igniter support  32 . Once the igniter  31  has been completely inserted into the support  32 , the feet  31   a  are put in a position of blockage by elastic return behind a non-visible shoulder of the slots  32   c , which makes any withdrawal of the igniter  31  impossible. 
     It will also be noted that two recesses  31   c  (visible in  FIG. 3 ) of the igniter  31  engage with the indexes  32   b  in order to guarantee a good angular orientation of the igniter  31  relative to the igniter support  32  along an axis  31   d  of the igniter  31 . The angular keyway is obtained by arranging the indexes  32   b  non-symmetrically relative to the axis  31   d.    
       FIG. 7  shows a detail of the top view of the igniter  31  inserted in the igniter support  32  at the level of a slot  32   c  and of the corresponding foot  31   a  (see  FIG. 3 ) in order to illustrate three mounting scenarios. 
     The left figure shows a correct mounting. The foot  31   a  with a T-section is correctly placed in a position of blocking after insertion of the igniter  31 . Only a first lower part  311   a  of the T is visible through the slot  32   c . A second part  311   b  with a greater area than the first part  311   a  is behind the igniter support  20 , represented in dotted lines. Therefore, it is possible to insert a checking fork comprising a central release into the slot  32   c  (which then acts as a checking opening) for verifying that the foot  31   a  is in the proper blocking position. 
     The figure in the middle illustrates a mounting scenario in which the foot  31   a  is incorrectly placed in a blocking position, which means that a withdrawal of the igniter  31  is possible. The rest of the T-shaped foot  31   a  is seen: the second part  311   b  with a greater area than the first part  311   a , and it would be impossible to insert the checking fork because it would strike against the second part  311   b  of the T-shaped foot  31   a . This type of error can therefore be detected. 
     The figure on the right shows a mounting scenario with the foot  31   a  absent due to a rupture, for example. The entire slot  32   c  is free and the checking fork would completely pass without the central, hollowed-out part striking the first part  311   a  of the foot  31   a , which also makes this error detectable. 
       FIG. 8  shows a sectional view of the igniter  31 . It comprises a plastic overmoulding that surrounds a case  31   g  welded on a glass cross-connector  31   i  and enclosing a pyrotechnical material  31   m . A pit  31   n  formed in the plastic overmoulding allows the case  31   g  to open in order to allow gases and/or hot particles created during the functioning of the igniter to pass. 
     The functioning of the igniter is initiated by the igniting of the pyrotechnical material  31   m . Several techniques can be used such as, for example here the passage of an electrical current in a resistive element which therefore heats up and causes the ignition of the pyrotechnical material  31   m . The pressure in the case  31   g  rapidly increases and forces the case  31   g  to break. 
     The case  31   g  has a cylindrical wall  31   e  and a bottom  31   f  In order to facilitate the opening of the case  31   g , the bottom  31   f  is petalled, preferably in eight sectors or petals in order to limit the risk of rupture and/or detachment of the petals during the functioning of the igniter. 
     Furthermore, the thickness of the bottom  31   f  is greater than that of the wall  31   e , which reduces even more the risk of rupture of petals as well as the angular amplitude of the opening of the petals. 
     The pit  31   n  has a depth H 1  greater than or equal to one half the diameter dl of the case. Consequently, the petals, once open, do not extend beyond the pit and can therefore not attack an element outside of the igniter such as an airbag fabric which could be located in the vicinity. This furthermore allows a better guiding of the gases and/or particles generated during the igniting of the igniter so that they are directly directed toward an inflatable cushion, for example. Moreover, the pit  31   n  has a diameter D 2  greater than the diameter dl so that the petals can open without being limited or striking the pit  31   n . The diameter D 2  is ideally greater than the diameter dl by 1.5 to 3 millimeters. This reduces the risk of rupture of the pit. 
     Note that the feet  31   a  and the slots  32   c  may not be arranged in a symmetric manner along the axis of the igniter but on the contrary can be arranged in an asymmetric manner in order to offer an angular keyway and correctly orient the pins of the igniter relative to the support and to the rest of the safety module. Finally, the feet  31   a  have a free length H 2  comprised between 5 and 10 millimeters in order to offer a good flexibility. Ideally, the free length H 2  is comprised between 7 and 9 millimeters in order to have a good elastic return and a good ability to be clipped at the end. 
     It is understood that various modifications and/or improvements evident to a person skilled in the art can be added to the different embodiments of the invention described in the present description without leaving the scope of the invention defined by the attached claims.