Automotive airbag device

This application claims priority to PCT/JP2004/017688 filed Nov. 29, 2004 and to Japanese Patent Application No. 2003-409340 filed Dec. 8, 2003.

1. Field of the Invention

The present invention relates to an airbag for use in motor vehicles. In particular it relates to a side airbag which uses a guide member to stabilize the flow of gas emitted from a gas generator into the airbag.

2. Description of Related Art

An airbag installed on the sides of the interior of a vehicle passenger compartment, and in particularly extended from the front seat region to the rear seat region, is commonly called a “side airbag” or “curtain airbag” in the art. When a side impact occurs, gas inflates the airbag which then expands, drops down from the passenger compartment ceiling, and covers the window, much like a curtain, in order to protect the passenger from injury. An airbag utilizing this type of structure is formed from one piece of fabric-like material folded over on itself, or two mutually overlaid fabric layers, after which the pieces of material are joined by adhering, welding, or sewing to form a bag-like structure.

In a conventional curtain-type automotive airbag device, inflating gas simply enters the airbag at the opening in the airbag where the insertion end of the gas generator is attached, the gas flow into the airbag only being controlled by the partitions formed at the seams where the fabric layers have been joined. This operation results in the adverse effect of an unstable gas flow within the airbag in the periphery of the insertion end of the gas generator, and thus indicates an area where the design of the airbag can be improved.

A countermeasure applied to rectify this problem has been to install a specially designed gas guide member in the airbag and to attach it to the insertion end of the gas generator as means of separating or directing the gas in specific directions therethrough. It has been assumed that the gas guide member may be made from the same flexible material as the airbag in order to be able to install the airbag to the vehicle body in the form of a rolled up spiral or folded over configuration.

It has been determined, however, that forming the gas guide member from a soft material results in the gas guide member vibrating with unstable oscillations due to the pressure of the flowing gas. This vibration has a destabilizing effect on the gas flow direction, and thus defeats the purpose of the gas guide member. Moreover, the high temperature gas may damage the airbag seams, especially those seams placed in proximity to the insertion end of the gas generator. These factors have the potential to adversely affect the performance and dependability of airbag operation.

In consideration of the aforesaid shortcoming of the conventional airbag structure, it is apparent there exists a need for an automotive airbag incorporating an improved gas guide member, to stabilize the flow of gas into the airbag.

The automotive side impact airbag of the present invention is primarily formed by joining mutually facing fabric layers, and including a gas generator used to inflate the airbag part by injecting gas therein, said gas generator having an insertion end which is inserted into and disposed within the airbag. The airbag includes a gas guide as means of guiding the flow of gas from the gas generator into the airbag. A gas guide member is also included incorporating an attachment orifice into which the insertion end part of the gas generator is inserted, and further incorporating gas injection nozzles facing an interior of the airbag. Finally, a convex seam, which is formed as a mutually joined part of the fabric layers, is located in opposition to the gas guide, such that gas flowing into the airbag from the gas generator, when the airbag is being inflated, causes the gas guide member to come into contact with the convex seam.

It is preferable that the gas guide member is equipped with a gas discharge tube which comes into contact with the convex seam when the airbag is being inflated. The gas discharge tube acts to change the direction of gas flow, which is supplied by the gas generator through the gas guide during inflation, to a transverse direction into the interior of the airbag. The gas injection nozzles are provided with the gas discharge tube.

It is preferable that at least one gas injection nozzle is formed over each side of a top part of the convex seam.

It is preferable that the part of the convex seam facing the gas guide member is approximately triangular in shape and the top part thereof is disposed facing the gas guide part in close proximity. It must be pointed out here that this approximate triangular shape is substantially a 3-sided shape. It is also preferable that each corner of the triangular shape is rounded off so as to form a curve through which adjacent sides of the triangle smoothly merge into each other. It is further preferable that the part of the gas discharge tube between the gas discharge nozzles comes into contact with and straddles the two inclined sides of the top part of the convex seam during airbag inflation.

It is preferable that the width of the convex seam facing the gas guide member is from 80 to 120% the width of the gas discharge tube of the gas guide member, and that the clearance between the gas guide member and convex seam is less than 20 mm.

It is further preferable that the gas guide member is made from an expandable material, and that it is designed to expand, as a result of the flow of gas therethrough, toward the convex seam a distance at least 5 mm greater than the clearance therebetween.

The airbag of the present invention has the effect of stabilizing the flow of gas into an airbag equipped with a gas guide member as a means of directing the flow of gas from an insertion end of a gas generator into the airbag.

Further objects, features and advantages of this invention will become readily apparent to persons skilled in the art after a review of the following description, with reference to the drawings and claims that are appended to and form a part of this specification

FIG. 1 is section view of the preferred embodiment of the automotive airbag according to the present invention illustrating the airbag in a undeployed condition with one of the two fabric layers removed for clarity.

FIG. 2 is a perspective view of the FIG. 1 airbag in a rolled up condition.

FIG. 3 is a line drawing describing the positional relationship between the gas guide member and the convex seam.

FIG. 4 is an enlarged cross section of the gas guide member of FIG. 1 during airbag deployment.

The following provides a detailed description of a preferred embodiment of the invention with reference to the attached drawings. The automotive airbag according to the present invention is embodied here in the form of a side impact or curtain airbag comprising, as shown in FIGS. 1 and 2 , a pouch-shaped airbag 2 formed from fabric layers 1 , and a gas generator 3 which inflates the airbag 2 by injecting gas therein.

The embodiment of the airbag 2 described in the drawings is constructed by joining the overlapping and mutually facing fabric layers 1 . Each fabric layer 1 is formed to a length approximately equivalent to the combined length of the front and rear seats in the fore-aft direction, and to a height sufficient to cover the vertical dimension of the side windows. Fastening tabs 4 are located on the perimeter of the airbag 2 as means of attaching the airbag 2 to the vehicle body, and tie tabs 4 a are also provided on the perimeter of the airbag 2 as means of maintaining the airbag 2 in a rolled up configuration as shown in FIG. 2 . Moreover, a vertical passage 1 a is formed as an upwardly protruding part of the airbag 2 in the center of the upper edge of each piece 1 , and a horizontal passage 1 b is formed as a horizontal part continuing in the horizontal direction from the vertical passage 1 a.

The fabric layers 1 are mutually joined along their edges to form a loop-shaped bag seam C 1 which extends from the vertical passage 1 a to the tip of the horizontal passage 1 b with the bag seam C 1 being open at the tip of the horizontal passage 1 b . In addition to being defined by the bag seam C 1 , an interior of the airbag 2 is partitioned by joining the fabric layers 1 at partition seams C 2 which have the purpose of controlling the flow of gas from the gas generator 3 into the airbag 2 . The airbag 2 thus includes airbag body 2 a which is internally partitioned at specific regions, gas generator attachment which is defined by the horizontal passage 1 b and into which the gas generator 3 is inserted, and gas guide part 2 c which is formed as part of the vertical passage 1 a and connects the airbag body 2 a with the gas generator attachment 2 b.

The fabric layers 1 may be mutually joined by any appropriate method such as gluing, welding, stitching etc. FIG. 1 shows a section view through the seam c 1 of the airbag 2 . The airbag 2 may be formed not only by overlapping and joining the two fabric layers 1 , but also by folding a single fabric layer over upon itself and joining parts of the two contacting surfaces, or by forming the bag structure when fabric is fabricated or woven.

One end of the cylindrically shaped gas generator 3 includes an insertion end 3 a , which includes gas discharge ports 5 , and is inserted into the gas generator attachment. The other end is formed as a connector part 3 b to which gas generator actuation wiring is connected and which is exposed externally to the gas generator attachment. FIG. 2 illustrates the airbag 2 in a rolled up configuration with the gas generator 3 attached, and shows the gas generator attachment protruding from the rolled up airbag body 2 a.

Returning to FIG. 1 , a gas guide member 6 extends from the gas generator attachment, through at least the gas guide part 2 c , into the pouch-shaped airbag body 2 a . The gas guide member 6 , which is an expandable pouch-like structure constructed from a fabric material, includes a cylindrical trunk 6 a disposed within the gas guide part 2 c , a cylindrical receiver 6 b formed along the gas generator attachment at the top of the cylindrical trunk 6 a , and a cylindrical gas discharge tube 6 c formed as a bidirectional horizontally extending tube-like structure at the lower end of the cylindrical trunk 6 a above the partition seam C 2 within the airbag body 2 a . The gas guide member 6 is constructed from an expandable material, for example, a nylon 6.6 700 dtex silicone coated fabric.

An attachment orifice 7 is formed at the end of the cylindrical receiver 6 b . The insertion end 3 a of the gas generator 3 , which inserts into the gas generator attachment part 2 b , installs into the cylindrical receiver 6 b of the gas guide member 6 through the attachment orifice 7 , thereby securing the gas discharge ports 5 towards the cylindrical trunk 6 a . Gas injection nozzles 8 , which comprise the left and right parts of the ends of the cylindrical gas discharge tube 6 c within the interior of the airbag body 2 a , are transversely disposed on a plane opposing the direction of incoming gas, and direct gas from the gas generator 3 into the airbag body 2 a . In this embodiment, the left and right ends of the gas discharge tube 6 c form the horizontally oriented the gas injection nozzles 8 . In this embodiment, a convex seam C 3 is formed within the airbag 2 and disposed in opposition to the gas guide part 2 c . The convex seam C 3 is formed as a joint of mutually bonded portions of the fabric layers 1 , and has a protruding rounded top part disposed opposite the gas guide part 2 c . During inflation, the inflow of gas from the gas generator 3 causes the gas guide member 6 to come into contact with the convex seam C 3 . More specifically, the gas inflow pressure from the gas generator 3 causes the gas guide member 6 , which is made of an expandable material, to expand as a result of the cylindrical trunk 6 a extending in upward and downward directions, thus resulting in the gas guide member 6 coming into contact with the convex seam C 3 . The convex seam C 3 is formed with the same joining method used to create the partition seams C 2 . As shown in the drawing, the convex seam C 3 is formed as the integral upper portion of the partition seam C 2 disposed in proximity to the gas guide member 6 . To describe further, the convex seam C 3 is approximately triangular in shape with its upward facing corner part formed as a top part “T” which has a smoothly curved profile disposed in close proximity to the transverse center of the gas discharge tube 6 c of the gas guide member 6 . During inflation, the part of the cylinder-shaped gas discharge tube 6 c between the two gas injection nozzles 8 comes into contact with and straddles two inclined sides “S” of the top part “T”. In other words, the two gas injection nozzles 8 are formed so as to move into contact with the convex seam C 3 with a type of pinching action as shown in FIG. 4 . In order to smooth the flow of gas entering the airbag 2 , it is preferable that the other two corner parts of the triangular shaped seam C 3 have curved profiles in the same manner as that of the top part “T”.

FIG. 3 provides a detailed illustration of the dimensional relationship between the gas discharge tube 6 c of the gas guide member 6 and the convex seam C 3 of the present embodiment. Firstly, it is preferable that a dimension W 1 , that is, the width of the convex seam C 3 facing the gas discharge tube 6 c , be from 80 to 120% of the width of a dimension W 0 which is the width of the gas discharge tube 6 c facing the convex seam C 3 . Should the width of the convex seam C 3 be made to a dimension exceeding 120% of the width of the gas discharge tube 6 c , there is a possibility that the gas exiting from the gas injection nozzles 8 will come into direct contact with and thermally damage the convex seam C 3 . Conversely, should the width of the convex seam C 3 be made to a dimension less than 80% of the width of the gas discharge tube 6 c , there is a possibility that the gas discharge tube 6 c , although in contact with the convex seam C 3 , will oscillate in an unstable manner, thus resulting in the gas potentially contacting and thermally damaging seams C 1 and C 2 .

Moreover, it is preferable that dimension “D”, which is the clearance between the gas discharge tube 6 c of the gas guide member 6 and the convex seam C 3 (particularly the top part “T”), be less than 20 mm. The gas guide member 6 , which is made from an expandable material, expands approximately 25 mm along a vertical plane when directing the gas flow from the gas generator 3 . Considering this extent of expansion, it has been determined that a clearance of less than 20 mm provides complete contact of the gas discharge tube 6 c against the convex seam C 3 . If clearance “D” exceeds 20 mm, there will be insufficient contact of the gas discharge tube 6 c against the convex seam C 3 , thus causing the gas discharge tube 6 c to flutter uncontrollably. While it has been determined that dimension “D” should be less than 20 mm to assure adequate contact between the two components, experimental results have shown that a dimension of from 5 to 8 mm is preferred, and that a dimension of 5.3 mm provides the most stable and dependable contact between the gas discharge tube 6 c and the convex seam C 3 .

The above dimensions are but one exemplary embodiment of the present invention. In general, depending on the material characteristics of the gas guide member 6 , it is preferable that the gas flow-through pressure be able to expand the gas guide member 6 toward the convex seam C 3 at least 5 mm greater than dimension “D”. In the example above, this value is obtained by subtracting the 20 mm clearance dimension from the previously noted 25 mm of extension of the gas guide member 6 , and is done for the same reason as stated previously.

The automotive airbag device invention described in this embodiment is assembled by placing the gas guide member 6 within the vertical passage 1 a and horizontal passage 1 b on one of the two fabric layers 1 . The previously noted clearance “D” is thus formed between the gas guide member 6 and convex seam C 3 as shown in FIG. 1 . Next, the other fabric-like material piece 1 is placed over the fabric-like material piece 1 onto which the gas guide member 6 was placed, and both pieces are joined to form the airbag 2 . The insertion end 3 a of the gas generator 3 is then inserted into the gas generator attachment of airbag 2 , and enters the cylindrical receiver 6 b of the gas guide member 6 via the attachment orifice 7 . The airbag body 2 a is then rolled up into the configuration shown in FIG. 2 , and is thus ready for installation to the vehicle.

The following will describe operation of the airbag as structured according to the current embodiment. Once the gas generator 3 activates, the gas emitted from the gas discharge ports 5 flows through and thereby pressurizes the interior of the gas guide member 6 . The pressure of the flowing gas expands the gas guide member 6 , and the gas simultaneously flows into the airbag body 2 a through the gas injection nozzles 8 , and is distributed within the airbag body 2 a via the partition seams C 2 .

As shown in FIG. 4 , the flow of gas from the gas generator 3 flows through and expands the gas guide member 6 , the cylindrical trunk 6 a elongates toward the convex seam C 3 , and the gas discharge tube 6 c moves downward and contacts the top part of the convex seam C 3 , thereby eliminating the clearance formerly existing there between. By having the gas discharge tube 6 c contact the convex seam C 3 , uncontrolled oscillation of the gas discharge tube 6 c is suppressed and the outflow of gas therefrom is stabilized, thus eliminating the problem of gas from the gas injection nozzles 8 striking and thermally damaging the partition seams C 2 .

As a person skilled in the art will readily appreciate, the above description is meant as an illustration of implementation of the principles this invention. This description is not intended to limit the scope or application of this invention in that the invention is susceptible to modification, variation and change, without departing from spirit of this invention, as defined in the following claims.