Abstract:
To provide a seat that enhances the stability and expansion speed with respect to the inflation expansion performance of airbag unit disposed thereinside. In one form, a seat is provided comprising a backrest part covered at its entirety with top fabric material and, at a given region of the top fabric material, it is furnished with tear line; an airbag constituted of a bag consisting of two basis fabrics joined together and disposed within the backrest part so as to at the time of inflation, cleave the tear line and expand over the head of driver or passenger; and reinforcing fabric disposed on the top fabric material so as to inhibit any cleavage of the top fabric material at regions other than the tear line.

Description:
CROSS-REFERENCE TO RELATED APPLICATIONS 
     This is a US national phase application of PCT/JP2006/320595, filed Oct. 16, 2006, which claims priority from Japanese Application No. 2006-003292, filed Jan. 11, 2006, which is hereby incorporated herein by reference in its entirety. 
     TECHNICAL FIELD 
     The present invention relates to a seat mounted to a vehicle, such as an automobile, and including an airbag in its interior. 
     BACKGROUND ART 
     Hitherto, various airbag devices, such as a driver airbag device that is inflated for deployment towards a driver from a rotational center of a steering wheel at a driver&#39;s seat, and a passenger airbag that is inflated for deployment towards a passenger&#39;s seat from an instrument panel, are used for restraining the body of an occupant when, for example, an automobile collides. 
     In recent years, an airbag device has already been proposed (refer to, for example, Japanese Unexamined Patent Application Publication No. 2002-37011) to overcome the following. That is, when a serious accident that applies a large external force to an automobile occurs, for example, overturning of a vehicle body, resulting from a collision, or falling of a heavy object, such as a tree, a shock may be due to the shock generated during the serious accident. 
     In the aforementioned related art, the following basic structure is discussed. That is, an airbag, formed of a bag member in which base cloths are joined to each other, is accommodated in a backrest (or a headrest) of a seat of a vehicle, and the airbag is inflated by supplying a pressure fluid from an inflator in an emergency, to deploy the airbag towards the upper side of the head of an occupant. 
     SUMMARY OF THE INVENTION 
     In optimizing an airbag device provided in the seat, it is necessary to increase stability and deployment speed in an inflation/deployment performance. 
     It is an object of the present invention to provide an effective technology that increases deployment speed and stability in an inflation/deployment performance of an airbag device provided in a seat. 
     To this end, a first invention provides a seat comprising a backrest covered with a skin cloth and including a cleavage portion at a predetermined portion of the skin cloth; an airbag formed of a bag member in which a base cloth is joined, the airbag being provided in an interior of the backrest so as to be deployed towards an upper side of the head of an occupant as a result of cleaving the cleavage portion during inflation; and a cleavage restricting member provided at the skin cloth so as to restrict a cleavage of the skin cloth at a portion other than the cleavage portion. 
     When supplying a pressure fluid to the airbag, first, inflation of the airbag is started in the interior of the backrest, and, during the inflation, the skin cloth that covers the backrest is pressed to cleave the cleavage portion. Then, the airbag is inflated towards the outside of the backrest through the opened cleavage portion, and is deployed towards the upper side of the head of the occupant. The airbag is formed so as to deployed at a predetermined disposition and in a predetermined order in an inflation/deployment process thereof, and is accommodated in the interior of the backrest by being folded in such a way as to be capable of being predeterminately deployed. The cleavage portion is provided with a proper length and at a proper position so as to be capable of being predeterminately deployed. 
     The present invention includes the aforementioned cleavage restricting member, so that, when the airbag cleaves the cleavage portion in the inflation/deployment process, it is possible to restrict excess cleavage of the skin cloth at portions other than the cleavage portion. Therefore, the airbag can be deployed in accordance with the predetermined deployment operations, that is, the stability of the inflation/deployment performance of the airbag device can be increased. 
     In addition, since the pressing force by the airbag can be concentrated only at the cleavage portion, the cleavage portion can be quickly cleaved, that is, the deployment speed of the inflation/deployment performance of the airbag device can be increased. 
     According to a second invention, in the first invention, an end of the cleavage restricting member is provided so as to substantially match an end of the cleavage portion. 
     This makes it possible to restrict tearing, serving as a source of excessive cleavage, in an end of the cleavage portion. 
     According to a third invention, in either the first invention or the second invention, the cleavage restricting member is provided near an/the end of the cleavage portion. 
     This makes it possible to restrict the occurrence of tearing in, in particular, an end of the cleavage portion that tends to become a source of excessive cleavage. 
     According to a fourth invention, in any one of the first to third inventions, the cleavage restricting member is provided at a stitch portion of the skin cloth. 
     This makes it possible to restrict cleavage in, in particular, the stitch portion of the skin cloth that tends to be cleaved. 
     According to a fifth invention, in any of the first to fourth inventions, a damping layer is provided at an inner side of the skin cloth, and the cleavage restricting member is provided at the damping layer. 
     This makes it possible to also restrict cleavage of the damping layer, so that the absorption performance of shock applied to the occupant can be maintained, thereby making it possible to increase safety. 
     According to the present invention, it is possible to increase deployment speed and stability in an inflation/deployment performance of an airbag device provided in a seat. 
    
    
     
       BRIEF DESCRIPTION OF THE DRAWINGS 
         FIG. 1  is a schematic side view for when a seat according to an embodiment of the present invention is installed in an automobile. 
         FIG. 2  is a perspective view showing a structure in which the airbag device of the seat according to the present invention is secured to a seat frame. 
         FIG. 3  is an exploded perspective view of the airbag device, showing the securing structure shown in  FIG. 2  in more detail. 
         FIG. 4  is a perspective view of the entire structure of an airbag in a completely inflated and deployed state as seen obliquely from the back. 
         FIG. 5  is an enlarged perspective view of the vicinity of a tear line of a backrest as seen obliquely from the front side. 
         FIG. 6  is a sectional view of the backrest taken along line VI-VI′ of  FIG. 5 . 
     
    
    
     DETAILED DESCRIPTION OF THE PREFERRED EMBODIMENTS 
     An embodiment of the present invention will hereunder be described with reference to the drawings. 
       FIG. 1  is a schematic side view of when a seat  1  according to an embodiment of the present invention is installed in an automobile, with  FIG. 1(   a ) showing a normal state and  FIG. 1(   b ) showing a state when an airbag is being inflated. In the following description, a forward direction is a direction in which an occupant  2  seated on the seat  1  faces the front, and a backward direction is a direction opposite thereto. 
     In  FIG. 1 , the occupant  2  is seated on the seat  1 . The seat  1  includes a sitting portion  1 A, and a backrest  1 B that protrudes upward from the sitting portion  1 A. A headrest  1 C is mounted to the top portion of the backrest  1 B. 
     In the seat  1 , an airbag device  10  for restraining a head  2 A of the occupant  2  when, for example, a vehicle body is overturned due to an accident is installed in the interior of the backrest  1 B. The airbag device  10  includes an airbag  11 , a retainer  12 , and an inflator  1 . The airbag  11  comprises a bag member, formed by sewing and connecting a first base cloth  35  and a second base cloth  36  (refer to  FIG. 4 ) to each other, and is provided so as to be deployed towards the upper side of the head  2 A of the occupant  2  when the airbag  11  is inflated. The retainer  12  accommodates the airbag  11  in a folded state. The inflator  13  supplies gas (pressure fluid) for inflating and deploying the airbag  11  (refer to  FIGS. 2 and 3 ). 
     The seat  1  includes in its interior a seat frame (strength supporting member)  14  including side plates  14 A (refer to  FIG. 2 ) and a cross member  14 B (refer to  FIG. 2 ), and forming the skeleton of the seat  1 . The retainer  12  and the inflator  13  are provided at the seat frame  14  (described in detail below). The entire sitting portion  1 A and the entire backrest  1 B of the seat  1  are covered with a skin cloth  1 D. A tear line (cleavage portion)  41 , which tends to tear compared to other portions, is formed by a perforated line along a horizontal straight line in a front top portion of the skin cloth  1 D covering the backrest  1 B. A foam layer  42 , which is a damping layer, is provided at the inside surface (at the inner side of the backrest  1 B) of the skin cloth  1 D. Further, a reinforcement cloth (cleavage restricting member)  43  is adhered around the tear line  41  at the inside surface of the foam layer  42  (refer to  FIGS. 5 and 6 ). 
     Although not shown, various sensors that detect the occurrence of (or prediction of the occurrence of) overturning or collision (including side collision) of an automobile are provided in the automobile to which the airbag device  10  is installed. On the basis of detection signals from these sensors, an inflator controlling circuit (not shown) starts an initiator (not shown) of the inflator  13 . 
     As shown in  FIG. 1(   a ), in a normal state, the airbag  11  is accommodated in a folded state in the retainer  12 . In contrast, when, for example, the automobile collides or is overturned as mentioned above, the sensors detect the collision or the overturning of the automobile, and a starting signal is input from the inflator controlling circuit to the initiator of the inflator  13 , so that, as shown in  FIG. 1(   b ), an upper deployment portion  38  of the airbag  11  is inflated, and is deployed between a roof  3  of the automobile and the head  2 A of the occupant  2 . At this time, the airbag  11  bulges outward after the tear line  41 , formed in the skin cloth  1 D of the backrest  1 B, is cleaved, and is deployed towards the upper side of the head  2 A of the occupant  2 . Then, the airbag  11  is inflated so that the head  2 A of the occupant  2  is pushed forward by the operation of a lower deployment portion  37  (refer to  FIG. 1)  of the airbag  11 , causing the head  2 A of the occupant  2  to bend forward, thereby making it possible to reduce a load on the neck. The consecutive deployment operations of the airbag  11  are set so that each portion of the airbag  11  is set so as to be inflated and deployed in a predetermined order and disposition. Accordingly, the shape of and the way in which the airbag  11  is folded in the retainer  12  are considered in accordance with this setting. 
       FIG. 2  is a perspective view showing a structure in which the airbag device  10  is secured to the seat frame  14 .  FIG. 3  is an exploded perspective view of the airbag device  10 , showing in more detail the aforementioned securing structure. 
     In  FIGS. 2 and 3 , the seat frame  14  includes the pair of side plates  14 A and  14 A, provided at respective sides in a vehicle-width direction (that is, respective sides in a horizontal direction in  FIG. 2 ) in the interior of the backrest  1 B of the seat  1 , and the cross member  14 B, extending between the side plates  14 A and  14 A along substantially the vehicle-width direction and connecting the side plates  14 A and  14 A to each other. The side plates  14 A and  14 A and the cross member  14 B are each provided in the interior of the backrest  1 B of the seat  1 . Although not particularly illustrated, the seat frame  14  includes a base plate provided in the interior of the sitting portion  1 A. 
     A gas supply port  11   a , connected to the inflator  13  through a pipe member  20 , and mounting portions  11   b  and  11   b , positioned at respective sides of the gas supply port  11   a , are provided at a base-end side (inflator side, lower side in  FIG. 3 ) of the airbag  11 . Two bolt holes  22  each for inserting mounting bolts  21   a  for securing the airbag  11  and the retainer  12  to each other are formed at the mounting portions  11   b  and  11   b,  respectively. Mounting portions  12   a  and  12   b,  having bolt holes  24  for inserting mounting bolts  23  for securing the retainer  12 , are formed at respective sides in the vehicle-width direction of the retainer  12 . A mounting portion  12   c,  similarly having bolt holes  25  at positions corresponding to the positions of the bolt holes  22  of the airbag mounting portions  11   b , is provided below (at the inflator side, lower side in  FIG. 3 ) the mounting portions  12   a  and  12   b.    
     While the airbag  11  is folded and accommodated in the retainer  12 , the plurality of mounting bolts  21   a  (four in the embodiment) are inserted into the bolt holes  25  of the retainer mounting portion  12   c,  the bolt holes  22  of the airbag mounting portions  11   b , and bolt holes  27 , formed in mounting plates  26  at positions corresponding to the bolt holes  22  of the airbag mounting portions  11   b ; and are fastened with nuts  21   b . This secures the airbag  11  to the retainer  12  while the airbag  11  is in a folded state. The mounting bolts  23  (two in the embodiment) are inserted into the bolt holes  24  of the retainer mounting portions  12   a  and  12   b , and are, then, fastened to fastening holes (not shown) provided in the cross member  14 B. This secures the retainer  12 , in which the airbag  11  is accommodated in a folded state, to the cross member  14 B. 
     The pipe member  20  is, for example, a metallic pipe that is bent at a plurality of locations (two locations in the embodiment), and is provided below the retainer  12 . The pipe member  20  and the airbag  11  are connected to each other by covering a bag-side end portion  20   a  of the pipe member  20  with the gas supply port  11   a  of the airbag  11 , and by caulking and securing them to each other with, for example, a metallic clamp band  30 . The pipe member  20  and the inflator  13  are connected to each other by covering a top end portion  13   a  of the inflator  13  with a connection portion  20   b,  provided at an inflator-side end portion of the pipe member  20 , and by adhering (or, for example, welding) them to each other. Accordingly, the airbag  11  and the inflator  13  are connected to each other through the pipe member  20 . 
     The inflator  13  is provided further below the pipe member  20 , and is mounted to one of the side plates  14 A (on the right side in the vehicle-width direction in the embodiment) with a mounting member  31 . The mounting member  31  includes a pair of mounting plates  31 A and  31 B that support the inflator  13  as a result of being placed on both sides of the inflator  13 . These mounting plates  31 A and  31 B are connected to each other using rivets by inserting a plurality of rivets  31   a  (four in the embodiment), formed at the mounting plate  31 A, into a plurality of rivet holes  31   b  (four in the embodiment), formed in corresponding positions of the mounting plate  31 B, so that the mounting plates  31 A and  31 B are secured to each other as a result of being placed on both sides of the inflator  13 . A mounting portion  31   c  is formed on one side (on the right side in the vehicle-width direction) of the mounting plate  31 A so as to be bent by substantially 90 degrees. A plurality of mounting bolts  32  (two in the embodiment) are inserted into respective bolt holes  33 , formed in the mounting portion  31   c , and are fastened to respective fastening holes (not shown) of the side plate  14 A, so that the mounting member  31  is secured to the side plate  14 A. As a result, the inflator  13  is secured to the side plate  14 A through the mounting member  31 . 
     The initiator (not shown) of the inflator  13  and the aforementioned inflator controlling circuit (not shown) are connected to each other with a cable  34 , so that an ignition control of the inflator  13  is carried out through the cable  34 . 
       FIG. 4  is a perspective view of the entire structure of the airbag  11  in a completely inflated and deployed state as seen obliquely from the back. 
     In  FIG. 4 , the airbag  11  comprises the bag member formed by sewing and connecting the first base cloth  35  and the second base cloth  36  as mentioned above. When the airbag  11  is in an inflated and deployed state as illustrated, the airbag  11  has a shape in which the lower deployment portion  37  and the upper deployment portion  38  are integrally formed. First, pressure fluid is supplied to the gas supply port  11   a  from the inflator  13 , so that the lower deployment portion  37  is inflated and deployed at a side opposing the back of the head of the occupant, causing the head of the occupant to be bent forward. Then, the upper deployment portion  39  is inflated and deployed towards the upper side of the head of the occupant. 
       FIG. 5  is an enlarged perspective view of the vicinity of the tear line  41  of the backrest  1 B as seen obliquely from the front side.  FIG. 6  is a sectional view of the backrest  1 B taken along line VI-VI′ of  FIG. 5 . To simplify the illustrations, the headrest is not shown in  FIGS. 5 and 6 . 
     In  FIGS. 5 and 6 , as mentioned above, the entire backrest  1 B is covered with the skin cloth  1 D, and the tear line  41  (a dotted line portion in  FIG. 6 ), which tends to tear compared to other portions, is formed, in this embodiment, along a horizontal straight line in the front top portion (left front side in  FIG. 5 ) of the backrest  1 B among the portions of the skin cloth  1 D by, for example, a perforated line. The length and disposition of the tear line  41  are set to a length and a disposition that allow the aforementioned predetermined deployment to be properly performed when it is pressed and cleaved at a suitable stage in an inflation/deployment process of the airbag  11  and, then, the airbag  11  bulges outward from the completely opened tear line  41 . An ornamental cloth  1 Da, in which design (esthetics) is considered, is sewed to the skin cloth  1 D at the front side of the backrest  1 B. A stitch portion  45  reaches the tear line  41 . The stitch portion  45  is sewed so that the skin cloth  1 D and the foam layer  42  at the inner side thereof are joined to each other. 
     The foam layer  42 , which is a damping layer that is formed of, for example, a sponge sheet and that absorbs, for example, shock applied to an occupant, is provided at the inside surface (at the inner side of the backrest  1 B) of the skin cloth  1 D. Further, the reinforcement cloth  43  (a broken line portion in  FIG. 6 ), formed of a material that has a high tensile strength and that does not break easily, is adhered to around the tear line  41  at the inside surface of the foam layer  42 . The foam layer  42  and the reinforcing cloth  43  are integrally provided with the inside surface of the skin cloth  1 D. Slits  44  whose lengths and locations match those of the tear line  41  of the slit cloth  1 D are formed at both the foam layer  42  and the reinforcing cloth  43 . 
     Open ends of the slit  44  of the reinforcing cloth  43  are adhered, for example, by using an adhesive or by welding to the inside surface of the skin cloth  1 D so as to match open ends of the tear line  41  that has been cleaved. Since the length (length in the vehicle-width direction) of the entire reinforcing cloth  43  is sufficiently longer than that of the tear line  41 , the reinforcing cloth  43  is adhered to where it overlaps the entire tear line  41 , including both ends  41   a,  and the stitch portion  45  at the vicinity of the tear line  41 . The reinforcing cloth  43  increases breakage strength of the foam layer  42  and the skin cloth  1 D at the vicinity of the tear line  41  while maintaining breakage property at the tear line  41 . 
     The seat  1  according to the embodiment having the above-described structure provides the following advantages. 
     That is, in the seat  1  according to the embodiment, providing the reinforcing cloth  43  can restrict excessive cleavage of the skin cloth  1 D at portions other than the tear line  41  when the airbag  11  cleaves the tear line  41  in the inflation/deployment process of the airbag  11 . Therefore, the airbag  11  can be deployed in accordance with the deployment operations carried out on the basis of the predetermined order and disposition. That is, the stability of the inflation/deployment performance of the airbag device  10  can be increased. 
     Since the pressing force by the airbag  11  can be concentrated at only the tear line  41 , the tear line  41  can be quickly cleaved. That is, the deployment speed in the inflation/deployment performance of the airbag device  10  can be increased. 
     A reinforcing cloth  43  may be provided at locations other than where the reinforcing cloth  43  overlaps the entire tear line  41  and the vicinity thereof unlike in the embodiment. For example, a reinforcing cloth  43  may be provided at a location far away from the tear line  41  where the airbag  11  may press the skin cloth  1 D (foam layer  42 ) in a concentrated manner and cause it to be cleaved during the inflation and deployment. Even in this case, escape of excessive pressing force of the airbag  11  caused by cleaving portions other than the tear line  41  can be restricted, so that the deployment speed and stability in the inflation/deployment performance of the airbag device  10  can be increased. 
     In the embodiment, by providing the open ends of each slit  44  of the reinforcing cloth  43  so as to substantially match the open ends of the tear line  41 , the production of a cleavage, which is a source causing progression of excessive cleavage at the open ends of the tear line  41 , can be restricted. 
     In addition, in the embodiment, providing the reinforcing cloth  43  near the ends  41   a  of the tear line  41  can restrict the production of a cleavage at the ends  41   a  of the tear line  41 , which tends to be a source causing excessive cleavage. 
     Further, in the embodiment, providing the reinforcing cloth  43  at the stitch portion  45  of the skin cloth  1 D makes it possible to restrict a cleavage at, in particular, the stitch portion  45  of the skin cloth  1 D, which has low rupture strength and which tends to be cleaved. 
     In the embodiment, providing the reinforcing cloth  43  at the inside surface of the foam layer  42  makes it possible to also restrict a cleavage of the foam layer  42 . Therefore, it is possible to maintain the capability of absorbing shock applied to an occupant in, for example, a collision of a vehicle, and to increase stability. 
     Although, in the embodiment, the reinforcing cloth  43 , formed of a cloth material and serving as a cleavage restricting member provided at portions other than the tear line  41 , is provided, the present invention is not limited thereto. For example, a reinforcing plate, formed of a material having a high strength, such as a metal or ceramic, may be provided, for example, in particular, near the ends  41   a  of the tear line  41  whose rupture strength needs to be increased. 
     Although, in the embodiment, the structure in which the airbag device  10  is provided in the interior of the backrest  1 B is described, the prevent invention can be applied to a structure in which the airbag device  10  is provided in the interior of the headrest  1 C covered with the skin cloth  1 D, and similar advantages can be provided. 
     The specific structure according to the above-described embodiment does not, strictly speaking, limit the content of the present invention. The details can obviously be variously changed in accordance with the gist of the present invention.