SIDE AIR BAG DEVICE

Abstract: A side air bag device embedded in a seat side portion for expanding an air bag (14) by rip-opening a sutured portion (26) of a seat skin material (20) by virtue of the expansion pressure of the air bag (14). In this device, a belt-like body (28) for concentrating the expansion pressure of the air bag when it is expanded is disposed so as to trigger the rip-opening of the sutured portion (26) of the skin rnaterial (20), whereby the quick rip-opening of the sutured portion (26) is made possible. In addition, in the above device, a seat pad (72) is interposed between an air bag case (16) and the seat skin material (20), whereby soft feel and touch of the seat are not lost.

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 JP-A-06064491, 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 stitching part where a covering material covering said opening and another covering material are stitched together, this stitching part is split open under 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 stitching part, depending mainly on differences in the elongation of the covering materials and the elongation of the stitching thread, there is a type of this splitting wherein the stitching part splits open as a result of sewing-machine perforations of the cover material breaking and a type wherein the stitching part 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. It is therefore an object of the invention to provide a side air bag device, by discovering a new construction making a start to splitting-open of a stitching part, with which easily it is possible to achieve causing a stitching part to split-open rapidly, a strength balance between a seat covering material and a stitching thread can be achieved simply and it is possible to increase productivity greatly. On the other hand, the conventional side air bag device described above has the shortcoming that because the air bag case is installed immediately behind the seat covering material there is a hardness in the feel from the seat surface. It is a further object 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. [Disclosure of the Invention] A side air bag device 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 a seat covering material has in the vicinity of an air bag case opening a stitching part where a covering material covering the opening and another covering material are stitched together and this stitching part is to be split open under a predetermined deployment pressure of an air bag, a band for suppressing elongation of the other covering material on deployment of the air bag extends between the other covering material at the stitching part and a fixed member such as a seat frame, one end of the band is fixed to the fixed member and the other end of the band is co-stitched to the other covering material by means of stitching thread of the stitching part. In this side air bag device, on deployment of the air bag the covering material covering the air bag case opening and the other covering material are first pushed by the internal pressure of the air bag, but because at this time elongation of the other covering material is limited by the band the force of the pushing of the air bag concentrates on the stitching of the band and as a result the stitching part of the seat covering material can be easily split open from this stitching part of the band. As a result of making a start to splitting-open of the stitching part by means of the band in this way this splitting-open can be effected rapidly, and, a strength balance between the seat covering material and the stitching thread can be achieved easily and it is possible to greatly raise productivity. When giving examples of splitting-open forms of this stitching part of the seat covering material, depending mainly on differences in the elongation of the covering materials and the elongation of the stitching thread, there are the following four: [1] The stitching part of the seat covering material is split open by the stitching thread starting to break from where the band is co-stitched. [2] The stitching part of the seat covering material is split open by sewing-machine perforations starting to break from where the band is co-stitched. [3] The stitching part of the seat covering material is split open by the stitching thread breaking and a small split being formed where the band is co-stitched and this split then being enlarged by breaking of sewing-machine perforations. [4] The stitching part of the seat covering material is split open by sewing-machine perforations breaking and a small split being formed where the band is co-stitched and this split then being enlarged by breaking of the stitching thread. Thus, the band initiates breaking of the stitching thread or sewing-machine perforations and the stitching part can be made to split open rapidly. In a side air bag device according to this invention, preferably the band is disposed inclined with respect to the stitching line of the stitching part so that the deployment pressure of the air bag concentrates at and splitting-open of the stitching part proceeds rapidly from one side of the stitching of the band. In this case, because the deployment pressure of the air bag is made to concentrate at one side of the stitching of the band, splitting-open of the stitching part can be made more rapid and there are also merits such as that it is possible to obtain a predetermined splitting-open starting point. In a side air bag device according to this invention it is also preferable from the point of further facilitating splitting-open of the stitching part that the end of the band on the seat covering material side be so stitched that it moves in a direction peeling from the stitching part when pulled by the other covering material on deployment of the air bag. Also, in a side air bag device according to this invention, the band may be disposed passing between the air bag case and the case side covering material. In a side air bag device according to this invention 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 invention, in the part of the pad on the inner side of the seat covering material stitching part, instead of forming a slit part for allowing the air bag to pass through on deployment, a weak part to be split open by deployment pressure of the air bag and allow the air bag to pass through may formed. This weak part can be formed by making the pad thinner than the surrounding. Also, this weak 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 invention, the shape of the slit part or the weak part can be a straight line shape or a bracket-like shape, and ends of the slit part or the weak 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 or the weak part can be made thin in the vicinity of the center of the slit part or the weak 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 in the case of the weak part it is possible to make the pad split open with a predetermined shape. Also, in a side air bag device according to the invention, a pad in a side of the seat in which the slit part or the weak 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 or weak part becomes easy, it is possible to make the positional relationship of the slit part or the weak part with respect to the air bag fixed and concentrate the deployment pressure of the air bag on the slit part or the weak 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 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 or the weak part, and by this means the surface of the pad in the vicinity of the slit part or weak part can be protected. [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 perspective view of a seat fitted with this air bag device, Fig. 3 is a horizontal sectional view of this air bag device, Fig. 4 is outline horizontal sectional views illustrating the operation of this air bag device, (a) showing the device before operation and (b) showing an initial stage and (c) a final stage in its operation, Fig. 5(a) is a perspective view of the device in the state shown in the preceding figure (b), and Fig. 5(b) is a perspective view of the device in the state shown in the preceding figure (c). Fig. 6 is a perspective view showing an example of fixing of a band in this air bag device to a fixed member, Fig. 7 is views showing another example of fixing of the band to the fixed member, (a) being a perspective view and (b) a sectional view. Fig. 8 is a sectional view showing another example of stitching of the band to the seat covering material. Fig. 9 is a perspective view of a seat fitted with a side air bag device of another embodiment of the invention, Fig. 10 is a front view showing an example of stitching of a band in this air bag device to a seat covering material, Fig. 11 is perspective views illustrating the operation of this air bag device, (a) showing an initial stage and (b) a final stage in its operation. Fig. 12 is a front view showing another example of stitching of a band in this air bag device, Fig. 13 is a front view showing a further example of stitching of a band, Fig. 14 is a front view showing a further example of stitching of a band, Fig. 15 is a front view showing a further example of stitching of a band. Fig. 16 is horizontal sectional view showing a side air bag device of another embodiment of the first invention of the invention, Fig. 17 is outline horizontal sectional views illustrating the operation of this air bag device, (a) showing the device before operation and (b) showing an initial stage and (c) a final stage in its operation. Fig. 18 is a horizontal sectional view showing a side air bag device of an embodiment of the invention, Fig. 19 is a perspective view of a backrest of a seat fitted with this air bag device, with a seat covering material removed, Fig. 20 is a horizontal sectional view showing another example of a slit part of this air bag device, Fig. 21 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. 22 is a horizontal sectional view showing a side air bag device of another embodiment of the invention of the invention, Fig. 23 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. 24 is a horizontal sectional view of a side air bag device of another embodiment of the invention, Fig. 25 is a perspective view of a backrest of a seat fitted with this air bag device, with a seat covering material removed. Fig. 26 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 or a weak part, Fig. 27 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 or a weak part. Fig. 28 is sketches of examples of modifications to the slit part or the weak part shown in Fig. 26, in (a) through (d) the shape of the ends of the slit part or the weak part and in (e) the pad thickness around the slit part or the weak part being modified. Fig. 29 is sketches of modifications to the slit part or the weak part shown in Fig. 27, in (a) through (d) the shape of the ends of the slit part or the weak part and in (e) the pad thickness around the slit part or the weak part being modified. Fig. 30 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. 31 is an outline sectional view showing a state of the side pad of the seat of the preceding figure on splitting-open. Fig. 32 is a sectional view showing a skin layer formed at the pad surface in the vicinity of a slit part or a weak part, Fig. 33 is a sectional view of a mold illustrating an example of molding of a seat pad. [Preferred Embodiments of the Invention] Figs. 1 through 3 show a side air bag device of a first embodiment of the invention. This side air bag device 10 has an inflator 12, an air bag 14 and an air bag case 16 and is embedded in the compartment wall (door) 20 side of a backrest 18a of a seat 18 of a vehicle, as shown in Figs. 1 through 3, and in an emergency deploys the air bag 14 toward the front of the vehicle between the occupant and the compartment wall 20, as shown in Figs. 1 and 3. A seat covering material 20 covering the surface of the seat 18 has a stitching part 26 where two covering materials 22, 24 are stitched together at the side of the front of the air bag case 16. That is, as shown in Fig. 3, at the side of an opening 16a in the air bag case 16, a case side covering material 22 covering this case opening 16a and an occupant side covering material 24 extending from this toward the side G on which the occupant sits are projected together and stitched, and this stitching part 26 is disposed inside the seat 18 and extends in a roughly vertically direction along the backrest 18a as shown in Fig. 2. As a result of stitching thread 27 of this stitching part 26 being broken by a predetermined deployment pressure of the air bag 14, the stitching part 26 splits open and the air bag 14 expands through this gap. In this side air bag device 10, a band 28 for suppressing elongation of the occupant side covering material 24 on deployment of the air bag 14 is provided extending between the occupant side covering material 24 at the stitching part 26 and a fixed member 30 such as a seat frame (or the air bag case 16), the fixed member side end 28b of this band 28 is fixed to this fixed member 30, and the seat covering material side end 28a is co-stitched to the occupant side covering material 24 with the stitching thread 27 of the stitching part 26. The fixed member side end 28b of this band 28 is fixed to the fixed member 30 by way of a bracket 32 and a bolt nut 34, as shown in Fig. 3 and Fig. 6. For this fixing, as shown in Fig. 7, alternatively a hook 37 or a karabiner-like ring hook (not shown) forcibly fitted onto a round bar 36 of the seat frame or the like may be attached to the fixed member side end 28b of the band 28, and it thereby engaged with the fixed member 30. As shown in Fig. 3, the seat covering material side end 28a of the band 28 is stitched reversely-facing so that it moves in a peeling direction when pulled by the occupant side covering material 24 on deployment of the air bag 14. This seat covering material side end 28a may alternatively be stitched so as to move in a shearing direction when pulled by the occupant side covering material 24, as shown in Fig. 8. However, from the point that it makes it possible to break the stitching thread 27 more easily, stitching the seat covering material side end 28a so that it moves in a peeling direction, as described above, is preferable. This band 28 is preferably made of a cloth made of nylon or polyester or the like having low elongation, and its width should be about 20 to 30mm. The width of the band 28 is preferably narrow like this compared to the width of the air bag 14 (about 300mm) because it then concentrates stress applied by the deployment pressure of the air bag 14. However, depending on the position in which the air bag case 16 is embedded, when the width of the band 28 is too narrow compared to the width of the air bag 14, it sometimes happens that the air bag 14 is bent by the band 28 during its inflation (i.e., the air bag 14 expands around the sides of the band 28) and it is difficult to obtain rapid inflation. For this reason, in such cases, the width of the band 28 is preferably about 150 to 400mm so that the band 28 guides the air bag 14 until the whole of the stitching part 26 has broken. This band 28 can be made of resin or metal instead of cloth, but in that case a hardness remains in the feel of the seat. In this side air bag device 10, when the air bag 14 starts to inflate from the state shown in Fig. 4(a), as shown in Fig. 4(b) and Fig. 5(a), deployment pressure of the air bag 14 first pushes the case side covering material 22 and the occupant side covering material 24 outward. Consequently, the occupant side covering material 24 tends to elongate together with the case side covering material 22, but because elongation of the occupant side covering material 24 is regulated by the band 28, the force of the pushing of the air bag 14 concentrates on the stitching part 26 at the band 28. As a result, as shown in Fig. 4(c) and Fig. 5(b), the stitching thread 27 starts to break from this part and the stitching part 26 of the two covering materials 22, 24 splits open. Because the pushing force of the air bag 14 is concentrated on the stitching part 26 at the band 28 like this, breaking of the stitching thread 27 holding together the covering materials 22, 24 is easy and consequently the stitching part 26 can be split open rapidly. In the embodiment described above, splitting-open of the stitching part 26 is effected by breaking of the stitching thread 27; however, according to the strength balance between the covering materials 22, 24 and the stitching thread 27, splitting open of the stitching part 26 can also be made to take any of the following other forms. That is, this splitting-open can be made to take any form such as one wherein sewing-machine perforations start to break from where the band 28 is stitched and the sewing-machine perforations of the stitching part 26 of the covering materials 22, 24 are entirely broken, one wherein the stitching thread 27 where the band 28 is stitched breaks and the band 28 peels away and a small split is formed in the stitching part 26 and then this split is enlarged by breaking of sewing-machine perforations of the covering materials 22, 24 by the pushing of the air bag 14, or one wherein sewing-machine perforations where the band 28 is stitched break and the band 28 peels and consequently a small split is formed in the stitching part 26 and then this split is enlarged by breaking of the stitching thread 27 by the pushing of the air bag 14. This is also the same in the cases of all the air bag devices discussed hereinafter. Fig. 9 shows a side air bag device 50 of another embodiment of the invention. In this side air bag device 50, the orientation of the band 28 with respect to the stitching part 26 is different from in the side air bag device 10 of the embodiment described above. That is, this embodiment has the characteristic that, as shown in Fig. 10, the band 28 is disposed so that the long axis line X, or length direction, of the band 28 is not perpendicular but rather is inclined with respect to the stitching line Y of the stitching part 26, so that deployment pressure of the air bag 14 concentrates at one side 28c of the stitching of the band 28 and splitting-open of the stitching part 26 occurs rapidly starting from this part. By this means, in this side air bag device 50, as shown in Fig. 11, when on deployment of the air bag 14 the case side and occupant side covering materials 22, 24 are pushed by the deployment pressure of the air bag 14, this pushing force concentrates on the one side 28c of the stitching of the band 28. Consequently, the stitching thread 27 starts to break from this part and the stitching part 26 of the covering materials 22, 24 splits open rapidly. Because by the band 28 being disposed inclined with respect to the stitching line Y of the stitching part 26 in this way it is possible to make the deployment pressure of the air bag 14 concentrate on a single point on the stitching part 26 at the band 28, the stitching thread 27 of the stitching part 26 can be made to break relatively easily and consequently more rapid splitting-open of the stitching part 26 becomes possible. Also, because the stitching thread 27 starts to break from the above-mentioned single point, there are merits such as that a predetermined starting point of splitting can be obtained. When the band 28 is disposed inclined with respect to the stitching line Y of the stitching part 26 in this way, it is made basic to dispose a single band 28 pointing diagonally downward with respect to the stitching line Y of the stitching part 26 at an acute angle of elevation, as shown in Fig. 10, but instead of this, one of two bands 28, 28 may be disposed pointing diagonally downward with respect to the stitching line Y of the stitching part 26 and the other may be disposed pointing diagonally upward with respect to the stitching line Y, as shown in Fig. 12. Also, as shown in Fig. 13 and Fig. 14, the seat covering material side end 28a of the band 28 may be extended and bent and stitched along the stitching line Y. Or, as shown in Fig. 15, a single band 28 may be bent in a V-shape and the bent portion stitched to the stitching part 26 as a seat covering material side end 28a and two fixed member side ends 28b, 28b respectively extending upward and downward from there may be brought together and fixed to the fixed member 30 with a single bolt 32. Also, the band 28, besides being one stitched while oriented at an incline with respect to the stitching line Y of the stitching part 26 as described above, may alternatively be made one stitched while perpendicular with respect to the stitching line Y of the stitching part 26 and then oriented at an incline by for example having its fixed member side end 28b fixed diagonally above or diagonally below the seat covering material side end 28a. Fig. 16 shows a side air bag device 60 of another embodiment of the invention. This side air bag device 60 differs from the side air bag device 10 described above in the point that the band 28 extending between the occupant side covering material 24 at the stitching part 26 and the fixed member 30 is disposed passing between the air bag case 16 and the case side covering material 22. That is, in this embodiment, the band 28 is disposed extending rearward passing between the opening 16a of the air bag case 16 and the case side covering material 22 from the seat covering material side end 28a stitched to the stitching part 26 and the fixed member side end 28b is fixed to the fixed member 30 behind the air bag case 16. Also when it is disposed like this, as shown in Fig. 17, the pushing force of the air bag 14 is concentrated on the stitching part 26 at the band 28 and the stitching part 26 can be rapidly split open. Also, in the case of this side air bag device 60, since it is possible to fix the fixed member side end 28b to the fixed member 30 from the back of the seat 18 after the seat covering material side end 28a is stitched to the stitching part 26, its manufacture is easy. Fig. 18 shows a side air bag device of another embodiment of the invention. In the side air bag device 70 of this embodiment also, as in the side air bag device 10 described above, 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 under 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. 19, this 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. 18 and Fig. 19 to the one having a gap of about 5mm shown in Fig. 20 and Fig. 21 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. 22 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, instead of a slit part 74, a weak part 82 for being split open by deployment pressure of the air bag 14 and allowing the air bag 14 to pass through is formed in the pad 72 disposed between the air bag case 16 and the seat covering material 20. That is, in this example, a weak 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 weak 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 weak 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. 23 shows another version of the weak part 82, and in this example the weak 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. 22 and Fig. 23 wherein a weak 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 weak part 82 split open easily, a small slit, which will be further discussed later, may be provided in the weak part 82. Fig. 24 and Fig. 25 show a side air bag device 90 of another embodiment of the invention. This side air bag device 90 is one wherein the construction of the first invention of the invention is added to the side air bag device 80 of the embodiment described above. That is, 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 weak 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 weak 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. The band 28, like that described in detail in embodiments of the first invention, 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 weak 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 of the invention described above, the shape of the slit part 74 or the weak part 82 can be made a straight line shape of the kind shown in Fig. 26 or a bracket-like shape of the kind shown in Fig. 27. It is also possible to form the upper and lower ends of the slit part 74 or the weak part 82 into a circle shape as shown in Fig. 28(a) and Fig. 29(a), into a T-shape as shown in Fig. 28(b) and Fig. 29(b), into an L-shape as shown in Fig. 28(c) and Fig. 29(c) or into a U-shape as shown in Fig. 28(d) and Fig. 29(d). Also, as shown in Fig. 28(e) and Fig. 29(e), it is possible to make the thickness of parts of the pad 72 adjacent to the slit part 74 or the weak part 82 thin in a central vicinity C of the slit part 74 or the weak part 82 and thicker with progress toward the end parts T. By these terminating treatments, in the case of a 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 the case of a weak part 82 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 of the invention, as shown as diagonal line areas in Fig. 30, it is possible to form a seat side pad 72 in which a slit part 74 or a weak part 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 or the weak part 82 easy, it is possible to fix the positional relationship of the slit part 74 or the weak part 82 with respect to the air bag 14 and concentrate the deployment pressure of the air bag 14 on the slit part 74 or the weak part 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 or the weak part 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. 31 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 or the weak part 82, as shown in Fig. 32. For example, as shown in Fig. 33, 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 or a weak part 82 lower than the surface temperature of the rest of the upper and lower molds 95, 96. In this case, as shown in Fig. 32, a skin layer 92 is formed at the surface of the urethane of the slit part 74 or the weak part 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 and the weak part 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 of this invention, because a band for starting splitting-open of a stitching part is 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 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 compartment wall side of a vehicle seat, wherein a seat covering material (20) has, in the vicinity of an air bag case opening (16a), a stitching part (26) where a covering material (22) covering the opening and another covering material (24) are stitched together and this stitching part is adapted to be split open under a predetermined deployment pressure of the air bag (14), characterised in that a band (28) for suppressing elongation of the other covering material (24) on deployment of the air bag (14) extends between the other covering material at the stitching part (26) and a fixed member (30) such as a seat frame, one end of the band (28) being fixed to the fixed member and the other end being co-stitched to the other covering material by means of stitching thread (27) of the stitching part. The device of claim 1, wherein the stitching part (26) of the seat covering material (20) splits open as a result of any of the following actions taking place: the stitching thread (27) starts to break from where the band (28) is co-stitched; sewing-machine perforations start to break from where the band (28) is co-stitched; the stitching thread (27) breaks and a small split is formed where the band (28) is co-stitched, and this split is then enlarged by breaking of sewing-machine perforations; sewing-machine perforations break and a small split is formed where the band (28) is co-stitched, and this split is then enlarged by breaking of the stitching thread (27). The device of claim 1, wherein the band (28) is inclined with respect to the stitching line of the stitching part (26) so that the deployment pressure of the air bag (14) concentrates at, and splitting-open of the stitching part proceeds rapidly from, one side of the stitching of the band. The device of claim 1, wherein the seat covering material side end of the band (28) is so stitched that it moves in a direction peeling from the stitching part (26) when pulled by the other covering material (24) on deployment of the air bag (14). The device of claim 1, wherein the band (28) passes between the air bag case (16) and the material (22) covering the air bag case opening (16a). The device of claim 1, wherein a seat pad (72) of predetermined thickness is interposed between the air bag case (16) and the seat covering material (20), and a slit part (74) or a weak part (82) for allowing the air bag (14) to pass through on deployment is formed in the pad on the inner side of the stitching part (26). The device of claim 6, wherein the weak part (82) is formed by making the pad (72) thinner than the surrounding, or by providing intermittent holes or slits to form a tear line. The device of claim 6, wherein the slit or weak part (74; 82) has the shape of a straight line or a bracket-like shape. The device of claim 8, wherein an end of the slit or weak part (74; 82) terminates in a circular, T-, L- or U-shape. The device of claim 6, wherein the thickness of a part of the pad (72) adjacent to the slit or weak part (74; 82) is made thin in the vicinity of the centre of, and thick at an end of, the slit or weak part (74; 82). The device of claim 6, wherein a pad in a side of the seat in which the slit or weak 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 6, wherein a 30 to 200 µm thick skin layer is formed at the surface of the pad in the vicinity of the slit part (74) or the weak part (82).

Inventors: NAKAGAWA YOSHIHISA, OZAKI TORU, SHINODA SHOEI, YAMAJI TAKESHI, YAMAMOTO JUNJI, NAKAGAWA, YOSHIHISA, OZAKI, TORU, SHINODA, SHOEI, YAMAJI, TAKESHI, YAMAMOTO, JUNJI
Applicants: TAKASHIMAYA NIPPATSU KOGYO, TOYO TIRE & RUBBER CO, TAKASHIMAYA NIPPATSU KOGYO CO. LTD., TOYO TIRE & RUBBER CO., LTD .
Application year: 1996
Main classification: B60R21
IPC codes: B60R21