Side air bag device

Abstract: A side air bag device for embedding in a compartment wall side of a vehicle seat, wherein seat covering materials (22,24) are stitched so as to be joined together in the vicinity of an air bag case opening (16a), the stitching part (26) being adapted to be split open by means of a predetermined deployment pressure of the air bag (14) and a seat pad (72) of a predetermined thickness is interposed between the air case (16) and the covering materials (22,24). Either a slit part (74) for allowing the air bag (14) to pass through on deployment is formed in the pad on the inner side of the covering material stitching part (26), or a weak part (82) split open by deployment pressure of the air bag (14) to allow the air bag to pass through is formed in the pad on the inner side of the covering stitching part (26).

Description: [Technological Field] This invention relates to a side air bag device for protecting an occupant from the side in the case of a collision accident of a vehicle. [Background Art] An air bag device is a device for restraining an occupant by inflation of an air bag in the case of a vehicle collision, and generally is made up of an inflator, which is a gas generator, an air bag capable of inflating by gas from the inflator, and an air bag case housing the air bag and the inflator. Air bag devices are not limited to those which restrain the occupant from the front, and recently, as disclosed in WO 9 630 233 A (forming prior art according to Art. 54(3) EPC), ones which restrain from the side have been being developed. With these side air bag devices, for example, an air bag case housing the air bag and the inflator is embedded in a compartment wall side of a seat such as in the door side of a seat backrest, a seat covering material covering the surface of the seat has in the vicinity of an opening of the air bag case a frangible seat seam where a covering material covering said opening and another covering material are stitched together, this frangible seat seam is split open by a predetermined deployment pressure of the air bag, and the air bag deploys through this split-open gap. In the above-mentioned splitting-open of the frangible seat seam, depending mainly on differences in the elongation of the covering materials and the elongation of the stitching thread, there is another type of this splitting wherein the frangible seam splits open as a result of sewing-machine perforations of the cover material breaking and a type wherein the frangible seam splits open as a result of the stitching thread breaking. The former type is widely used for example with composite seat covering materials made of a vinyl chloride leather and a lining material, and the latter type is widely used for example with composite seat covering materials made by lining a fabric material (raised material, moquette) with a polyurethane foam seat material. However, there is the limitation that in the case of the former type of splitting wherein sewing-machine perforations of the cover material are to be broken the strength of the stitching thread must be stronger than the strength of the covering material between sewing-machine perforations and in the case of the latter type of splitting wherein the stitching thread is to be broken reversely the seat covering material must be stronger, and both cases require a high-level balance in quality and technology aspects. [Sumary of the Invention] It is therefore an object of the invention to provide an improved side air bag device. This object is solved by a side air bag device according to claim 1. The subclaims are directed to preferred embodiments of the invention. It is an advantage of an embodiment of the invention to provide a side air bag device with which by disposing a seat pad between the air bag case and the seat covering material and using a construction such that this pad can be split open it is possible to provide comfort with excellent feel from the seat surface and with no feeling of incongruity in the seat. A side air bag device according to an embodiment of the invention is one wherein, in a side air bag device which is an air bag device embedded in a compartment wall side of a seat of a vehicle wherein seat covering materials are stitched so as to be joined together in the vicinity of an air bag case opening and this stitching part is to be split open by means of a predetermined deployment pressure of an air bag, a seat pad of a predetermined thickness is interposed between the air bag case and the covering materials and a slit part for allowing the air bag to pass through the pad on deployment is formed in the pad on the inner side of the stitching part. By the air bag case, which conventionally has been adjacent to the seat covering material, being covered with the pad in this way, it is possible to install the side air bag device without losing the softness or the feeling of the feel of the seat. In a side air bag device according to this embodiment, in the part of the pad on the inner side of the seat covering material stitching part, a slit part for allowing the air bag to pass through on deployment may be formed. This split part can be formed by making the pad thinner than the surrounding. Also, this split part may be one formed by providing holes or slits intermittently in the form of a tear line. In a side air bag device according to this embodiment, the shape of the slit part can be a straight line shape or a bracket-like shape, and ends of the slit part may be terminated into a circular shape, a T-shape, an L-shape or a U-shape. Also, the thickness of parts of the pad adjacent to the slit part can be made thin in the vicinity of the center of the slit part and thick at its ends. By these end treatments, on deployment of the air bag, in the case of the slit part it is possible to prevent its ends from tearing and it is possible to make the pad split open with a predetermined shape. Also, in a side air bag device according to this embodiment of the invention, a pad in a side of the seat in which the slit part is formed can be made harder than a pad of another part of the seat and formed integrally with the pad of another part of the seat. As a result, because maintenance of the shape of the slit part becomes easy, it is possible to make the positional relationship of the slit part with respect to the air bag fixed and concentrate the deployment pressure of the air bag on the slit part and it is possible to make the position of the part of the pad which splits open fixed. Also, because it is possible to make the pad highly elastic with respect to the deployment pressure of the inflating air bag it is possible to increase the strength of a hinge part of the pad opened outward by the splitting-open of the pad. It is also effective in increasing the firmness with which the occupant is held in the seat. In a side air bag device according to this embodiment of the invention it is also possible to form a skin layer of thickness 30 to 200µm at the surface of the pad in the vicinity of the slit part , and by this means the surface of the pad in the vicinity of the slit part can be protected. In a side air bag device embedded in a side wall compartment of a seat of a vehicle which by means of a predetermined deployment pressure of an air bag splits open a stitching part in a seat covering material where a covering material covering an opening in an air bag case and another covering material are stitched together in the vicinity of the opening in the air bag case, a seat pad of a predetermined thickness may be interposed between the air bag case and the seat covering material and a slit part for allowing the air bag to pass through on deployment may be formed in the pad on the inner side of the stitching part and a band for suppressing elongation of the other covering material on deployment of the air bag may be provided extending between the other covering material at the stitching part and a fixed member such as a seat frame, one end of the band may be fixed to the fixed member and the other end of the band may be co-stitched to the other covering material by means of stitching thread of the stitching part. With this construction, the softness and feeling of the seat are not lost and it is possible to make the stitching part split open rapidly on deployment of the air bag. [Brief Description of the Drawings] Fig. 1 is a perspective view of part of a compartment interior showing a side air bag device of an embodiment of the invention after the device has operated, Fig. 2 is a horizontal sectional view showing a side air bag device of an embodiment of an embodiment of the invention, Fig. 3 is a perspective view of a backrest of a seat fitted with this air bag device, with a seat covering material removed, Fig. 4 is a horizontal sectional view showing another example of a slit part of this air bag device, Fig. 5 is a perspective view of a backrest of a seat fitted with the device shown in Fig. 20, with a seat covering material removed. Fig. 6 is a horizontal sectional view showing a side air bag device of another embodiment of the invention, Fig. 7 is a perspective view of a backrest of a seat with a seat covering material removed showing another example of a weak part of this air bag device. Fig. 8 is a horizontal sectional view of a side air bag device of another embodiment of the invention, Fig. 9 is a perspective view of a backrest of a seat fitted with this air bag device, with a seat covering material removed. Fig. 10 is a perspective view of a backrest of a seat with a seat covering material removed showing an example of the shape of a slit part, Fig. 11 is a perspective view of a backrest of a seat with a seat covering material removed showing another example of the shape of a slit part. Fig. 12 is a sketch of examples of modifications to the slit part or the weak part shown in Fig. 10, in (a) through (d) the shape of the ends of the slit part and in (e) the pad thickness around the slit part being modified. Fig. 13 is a sketch of modifications to the slit part or the weak part shown in Fig. 11, in (a) through (d) the shape of the ends of the slit part and in (e) the pad thickness around the slit part being modified. Fig. 14 is a perspective view of a backrest of a seat with a seat covering material removed showing an example wherein a side pad of the seat is made of a foam of a different hardness, Fig. 15 is an outline sectional view showing a state of the side pad of the seat of the preceding figure on splitting-open. Fig. 16 is a sectional view showing a skin layer formed at the pad surface in the vicinity of a slit part, Fig. 17 is a sectional view of a mold illustrating an example of molding of a seat pad. [Preferred Embodiments of the Invention] Figs. 1 and 2 show a side air bag device of an embodiment of the second invention of the invention. In the side air bag device 70 of this embodiment an air bag case 16 housing an inflator 12 and an air bag 14 is embedded in the compartment wall 20 side of a backrest 18a of a seat 18, a case side covering material 22 and an occupant side covering material 24 are stitched together diagonally in front of the opening 16a in the air bag case 16, and by this stitching part 26 being split open by a predetermined deployment pressure of the air bag 14 the air bag 14 is able to expand between the occupant and the compartment wall 20 in an emergency. In the side air bag device 70 of this embodiment, a urethane foam pad 72 of a predetermined thickness is interposed between the air bag case 16 and the seat covering material 20. That is, urethane foam pads 72, 73 are disposed not only in the side G of the seat 18 on which the occupant sits but also in the seat side in which the side air bag device 70 is installed. A slit part 74 which allows the air bag 14 to pass through the pad on deployment of the air bag 14 is formed in the part of this pad 72 that is on the inner side of the stitching part 26 of the covering materials 22, 24. As shown in Fig. 3, the slit part 74 is formed extending in an up-down direction along the side of the seat backrest 18a alongside the stitching part 26. As this slit part 74, any slit part from the one having no gap shown in Fig. 2 and Fig. 3 to the one having a gap of about 5mm shown in Fig. 4 and Fig. 5 is suitable, and as the length of the slit, so that the air bag 14 can pass through, about 300 to 500mm is suitable. In the side air bag device 70 of this embodiment, because the urethane foam pad 72 is interposed between the air bag case 16 and the covering materials 22, 24 covering it, the feel of the seat from the seat surface is superior. Also, because the slit part 74 is provided in this pad 72, there is the effect that the air bag 14 can pass through on deployment and inflation of the air bag 14 in a predetermined position becomes possible. Even when a slit part 74 is provided in the urethane foam pad 72 like this, because of the presence of the seat covering material 20 on the seat surface, a seat with its feeling maintained is possible. Fig. 6 shows a side air bag device 80 of another embodiment of the invention. This side air bag device 80 differs from the side air bag device 70 of the embodiment described above in the point that, a slit part 82 made by making the pad thinner than the surrounding is formed in the part of the pad 72 on the inner side of the stitching part 26 extending in an up-down direction along the side of the seat backrest 18a alongside the stitching part 26, and on deployment of the air bag 14 the slit part 82 is split open by the deployment pressure of the air bag 14 and the air bag 14 expands to outside the seat through this gap. When the slit part 82 is formed by locally making the pad thinner like this, it is preferably formed as if by scooping out the inner wall side of the pad 72, as shown in Fig. 22. Fig. 7 shows the slit part 82, where the slit part 82 is formed by providing holes or slits in the pad 72 intermittently in the form of a tear line. In the cases shown in Fig. 6 and Fig. 7 wherein a slit part 82 is formed in the pad 72, because compared to when a slit part 74 is formed the integrity of the urethane foam pad 72 is higher, it is possible to further preserve the feeling of the seat 18. To make the slit part 82 split open easily, a small slit, which will be further discussed later, is provided in the slit part 82. Fig. 8 and Fig. 9 show a side air bag device 90 of another embodiment of the invention. In this side air bag device 90, as well as a urethane foam pad 72 being interposed between the air bag case 16 and the covering materials 22, 24, a slit part 82 for splitting open on deployment of the air bag 14 and allowing the air bag 14 to pass through is formed in the pad 72 on the inner side of the seat covering material stitching part 26. This slit part 82 has in the middle thereof a small slit part 82a, and a band 28 for suppressing elongation of the occupant side covering material 24 during inflation of the air bag 14 is disposed passing through this small slit part 82a from inside to outside. A band 28, is disposed extending between an occupant side covering material 24 at the stitching part 26 and a fixed member 30 such as a seat frame, and one end 28b thereof is fixed to the fixed member 30 and the other end 28a is co-stitched to the occupant side covering material 24 with stitching thread 27 of the stitching part 26. With this side air bag device 90, while maintaining the softness of the feel of the seat, it is possible to make the seat covering material stitching part 26 split open rapidly on deployment of the air bag 14. Instead of the slit part 82, a slit part 74 of the kind described above may be provided and the band 28 made to pass through this slit part 74. In all the embodiments described above, the shape of the slit part 74, 82 can be made a straight line shape of the kind shown in Fig. 10 or a bracket-like shape of the kind shown in Fig. 11. It is also possible to form the upper and lower ends of the slit part 74, 82 into a circle shape as shown in Fig. 12(a) and Fig. 13(a), into a T-shape as shown in Fig. 12(b) and Fig. 13(b), into an L-shape as shown in Fig. 12(c) and Fig. 13(c) or into a U-shape as shown in Fig. 12(d) and Fig. 13(d). Also, as shown in Fig. 12(e) and Fig. 13(e), it is possible to make the thickness of parts of the pad 72 adjacent to the slit part 74, 82 thin in a central vicinity C of the slit part 74, 82 and thicker with progress toward the end parts T. By these terminating treatments, in one embodiment of the slit part 74 it is possible to prevent the upper and lower ends thereof from tearing on deployment of the air bag 14 and in another embodiment of the slit part 82a it is possible to make the pad 72 split open with a predetermined shape (that is, it is possible to make splitting-open of the pad end at those positions). Also, in all the embodiments of the invention, as shown as diagonal line areas in Fig. 14, it is possible to form a seat side pad 72 in which a slit part 74, 82 is formed, and, depending on the case, the side of the opposite side of the seat, using a urethane foam harder than that of the central pad 73 and integral with the pad 73. In this case, the side pad 72 is formed integrally using for example low molecular weight or highly crosslinked urethane foam of a different hardness. Because this makes shape maintenance of the slit part 74, 82 easy, it is possible to fix the positional relationship of the slit part 74, 82 with respect to the air bag 14 and concentrate the deployment pressure of the air bag 14 on the slit part 74, 82 and the position at which the pad 72 splits open can also be fixed. That is, when the pad 72 is of low hardness, sometimes for example under the body weight of an occupant partially it is not possible to maintain the predetermined shape of the pad and its cross-sectional shape and contours deform, and consequently the obtained effect of stress concentrating at the slit part 74, 82 might decrease; however, by making the side pad 72 hard as described above it is possible to eliminate this problem. Also, because it is possible to make the pad 72 highly elastic with respect to the deployment pressure of the air bag 14, the strength of a hinge part 72a of the pad 72 opening outward after splitting as shown in Fig. 15 can be increased. Furthermore, making the seat side pads harder is also effective in increasing the firmness with which the occupant is held in the seat. Also, in all the embodiments of the invention, by adjusting the surface temperature of molds and the foam pressure during urethane foam molding, a solid skin layer 92 of thickness about 30 to 200µm may be formed at the surface of the pad 72 in the vicinity of the slit part 74, 82, as shown in Fig. 16. For example, as shown in Fig. 17, when carrying out urethane foam molding using an upper mold 95 and a lower mold 96, the above-mentioned skin layer 92 can be formed by making the temperature of a mold forming piece 97 for forming a slit part 74, 82 lower than the surface temperature of the rest of the upper and lower molds 95, 96. In this case, as shown in Fig. 16, a skin layer 92 is formed at the surface of the urethane of the slit part 74, 82 for the air bag 14 to pass through on deployment, and from the surface by way of a microcell layer 93, which is a fine foam layer, to a cell layer 94 which is an ordinary foam layer, the foam diameter successively increases. By forming a skin layer 92 like this it is possible to protect the surface of the pad 72 with which the air bag 14 makes contact on deployment of the air bag 14 and splitting-open of the pad 72 with a neat split surface is possible. The slit part 74, 82 in all the embodiments of the invention can also be formed by a cutting process using a cutter knife or a sander or the like. A cutting process can be carried out easily by hand without special equipment being required and is suitable for low-volume production, and molding is suitable for mass-production. [Industrial Applicability] In a side air bag device according to an embodiment of this invention, because a band for starting splitting-open of a stitching part may be provided, the stitching part can be split open rapidly and because a strength balance between the seat covering material and the stitching thread can be achieved easily it is possible to greatly increase productivity. Also, in a side air bag device according to an embodiment of the invention, because a seat pad is interposed between the air bag case and the seat covering material, it is possible to install the side air bag device in a seat without impairing the softness and feeling of the feel of the seat.

Claims: A side air bag device for embedding in a side wall compartment of a vehicle seat, wherein seat covering materials (22, 24) are joined by stitching in the vicinity of an opening (16a) of an airbag case (16) and this stitching (26) is adapted to be split open by means of a predetermined deployment pressure of the air bag (14), and wherein a seat pad (72) of predetermined thickness is interposed between the air bag case (16) and the covering materials (22, 24), and a slit part (74, 82) for allowing the air bag (14) to pass through on deployment is formed in the pad on the inner side of the covering material stitching (26). The device of claim 1, wherein the slit part (82) is formed by providing intermittent holes or slits to form a tear line. The device of claim 1, wherein the slit part (74; 82) has the shape of a straight line or a bracket-like shape. The device of claim 3, wherein an end of the slit part (74; 82) terminates in a circular, T-, L- or U-shape. The device of claim 1, wherein the thickness of a part of the pad (72) adjacent to the slit part (74; 82) is made thin in the vicinity of the centre of, and thick at an end of, the slit part (74; 82). The device of claim 1, wherein a pad in a side of the seat in which the slit part (74; 82) is formed is made harder than a pad of another part of the seat and is formed integrally with the pad of the other part of the seat. The device of claim 1, wherein a skin layer of thickness 30 to 200 µm is formed at the surface of the pad in the vicinity of the slit part (74; 82).

Inventors: NAKAGAWA YOSHIHISA, OZAKI TORU, SHINODA SHOEI, YAMAJI TAKESHI, YAMAMOTO JUNJI, NAKAGAWA, YOSHIHISA, OZAKI, TORU, SHINODA, SHOEI, YAMAJI, TAKESHI, YAMAMOTO, JUNJI, Ozaki, Toru, c/o Toyo Tire &amp; Rubber Co., Ltd., Yamaji, Takeshi, c/o Toyo Tire &amp; Rubber Co., Ltd., Yamamoto, Junji, c/o Toyo Tire &amp; Rubber Co., Ltd.
Applicants: TAKASHIMAYA NIPPATSU KOGYO, TOYODA GOSEI KK, TAKASHIMAYA NIPPATSU KOGYO CO. LTD., TOYODA GOSEI CO., LTD.
Application year: 1996
Main classification: B60R21
IPC codes: B60R21