Airbag system

Abstract

To provide an airbag device having a breaking device which is used to bring a strap into a free state and has a simple structure and a simple operation mechanism.SOLUTION: An airbag device 1 includes: an airbag 2 having a vent hole 21 having an opening shape; a flap 4 attached to the airbag 2 and configured to cover the vent hole 21; a strap 5 extending from the flap 4, fixed to a strap attachment part 2, and fixing the flap 4 to a closed position for closing the bent hole 21; and a heat generation device 60 for breaking a fixing material 50 for fixing the strap 5 to the strap attachment part 2 by heat to bring the strap 5 into a free state.SELECTED DRAWING: Figure 3

Description

Technical Field

[0001] The present invention relates to an airbag device mounted on a vehicle.

Background Art

[0002] In various airbag devices, upon collision, an inflation fluid such as gas generated by an inflation fluid source such as an inflator is supplied to an airbag connected to the inflation fluid source, and the airbag is deployed and inflated between the vehicle body and the occupant to protect the occupant.

[0003] By the way, in an airbag device, for the purpose of protecting the occupant from the impact of a collision, it is necessary to supply a sufficient amount of inflation fluid to the airbag quickly and sufficiently during its deployment and inflation. However, on the other hand, the airbag applies a large reaction force to the occupant, which causes significant discomfort to the occupant. If the reaction force is excessive, it will give a large impact to the occupant, and as a result, there is a risk of burdening the occupant's body.

[0004] In order to avoid the above problems during the deployment and inflation of the airbag, an airbag device provided with an open vent hole in the airbag is known. In this type of airbag device, at the initial stage during the deployment and inflation of the airbag, the vent hole is closed to supply a sufficient amount of inflation fluid to the airbag quickly and increase the internal pressure of the airbag to a sufficient level to protect the occupant. Then, by opening the vent hole, the inflation fluid inside the airbag is allowed to flow out to the outside, reducing the internal pressure of the airbag and reducing the above-mentioned reaction force applied to the occupant.

[0005] Various methods have been proposed as methods for opening and closing the vent hole of the airbag.

[0006] Patent Document 1 describes an airbag device in which a vent hole 14 is provided in the airbag 1, the vent hole 14 is closed by bringing a protruding portion 13 into close contact with the surface of the airbag 1, and the vent hole 14 is opened by raising the protruding portion 13 relative to the airbag 1.

[0007] A strap 4, which is roughly cord-shaped, is connected to the above-mentioned protruding portion 13. In the airbag device described in Patent Document 1, tension is applied to the strap 4, and consequently to the projection 13, causing the projection 13 to adhere tightly to the surface of the airbag 1 and closing the vent hole 14. Then, by using a cutting device including a cutter 53 to break the strap 4, the strap 4 is freed, causing the projection 13 to stand upright relative to the airbag 1 and opening the vent hole 14.

[0008] Patent Document 2 discloses a method in which a through-hole 4b is provided around the vent hole 4a for passing a strap (tether 5), and a portion of the tether 5 is passed through the through-hole 4b and makes a full circle around the vent hole 4a. In the airbag system described in Patent Document 2, as the airbag 4 deploys, the tether 5 becomes taut and constricts the vent hole 4a, thereby closing the vent hole 4a. Furthermore, after the airbag 4 has fully deployed, the tether 5 is released from tension (i.e., the strap becomes free) by using a rupturing device including a cutter (tether cutter 6), and the vent hole 4a is opened when an occupant collides with the deployed airbag 4. [Prior art documents] [Patent Documents]

[0009] [Patent Document 1] Japanese Patent Publication No. 2013-35473 [Patent Document 2] Japanese Patent Publication No. 2020-185893 [Overview of the project] [Problems that the invention aims to solve]

[0010] Here, the breaking device for cutting a strap using a cutter, as described in Patent Documents 1 and 2 above, requires a drive mechanism for changing the position of the cutter.

[0011] Specifically, for example, in the drive mechanism of the airbag device described in Patent Document 1, the squib 54 generates a thrust force that slides the cutter 53 toward the strap 4. Furthermore, the drive mechanism of the airbag device described in Patent Document 1 requires a mechanism to fully utilize the thrust force generated by the squib 54, such as a pressure-receiving surface 53b provided on the cutter 53 to receive the combustion products generated by the squib 54, and a housing 55 for housing the squib 54 and the cutter 53.

[0012] Therefore, in the type of airbag devices described in Patent Documents 1 and 2, that is, airbag devices that use a cutter to sever straps in order to open vent holes, the structure of the severing device, including the drive mechanism, is complex, making it difficult to reduce manufacturing costs.

[0013] Furthermore, in order for the above-mentioned breaking device to break the strap, it is necessary to operate the drive mechanism correctly to generate driving force, correctly transmit the driving force generated by the drive mechanism to the cutter, and operate the cutter correctly. For this reason, in an airbag device that breaks the strap with a cutter, the operation of the breaking device as a whole requires very high precision. For this reason, there is room for improvement in the operating mechanism of the breaking device that breaks the strap.

[0014] This invention has been made in view of the above circumstances, and aims to solve the problem of providing an airbag device that can release the strap with a simple structure and simple operating mechanism. [Means for solving the problem]

[0015] The airbag device of the present invention, which solves the above problems, An airbag having an open vent hole, and a flap attached to the airbag and covering the vent hole, a strap extending from the flap, fixed to a strap attachment portion, and positioning and fixing the flap in a closed position for closing the vent hole, a fixing member for fixing the strap to the strap attachment portion, and a heating device that releases the strap by thermally breaking the fixing member. The airbag device includes these components.

[0016] The airbag device of the present invention can put the strap in a free state with a simple structure and a simple operating mechanism.

Brief Description of the Drawings

[0017] [Figure 1] It is an explanatory diagram schematically explaining a state in which the airbag in the airbag device of Example 1 is deployed and inflated. [Figure 2] It is an explanatory diagram schematically explaining a state in which the airbag in the airbag device of Example 1 is deployed and inflated. [Figure 3] It is an enlarged view of the main part of FIG. 1. [Figure 4] It is an explanatory diagram schematically explaining a unit of an airbag, a flap, a strap, an inflation fluid generation source, and a case in the airbag device of Example 1. [Figure 5] It is an explanatory diagram schematically explaining a cap in the airbag device of Example 1. [Figure 6] It is an explanatory diagram schematically explaining a state of a flap, a strap, and a fixing member in the airbag device of Example 1 as viewed from the outside of the airbag. [Figure 7] It is an explanatory diagram schematically explaining a state in which the active vent hole of the airbag in the airbag device of Example 1 is closed or opened by the flap. [Figure 8]It is an explanatory diagram schematically explaining the state in which the flap closes or opens the active vent hole of the airbag in the airbag device of Example 1. [Figure 9] It is an explanatory diagram schematically explaining the state in which the flap closes or opens the active vent hole of the airbag in the airbag device of Example 1. [Figure 10] It is an explanatory diagram schematically explaining the state in which the flap closes or opens the active vent hole of the airbag in the airbag device of Example 1. [Figure 11] It is an explanatory diagram schematically explaining the state in which the flap closes or opens the active vent hole of the airbag in the airbag device of Example 1. [Figure 12] It is an explanatory diagram schematically explaining the state in which the flap closes or opens the active vent hole of the airbag in the airbag device of Example 1. [Figure 13] It is an explanatory diagram schematically explaining the cap in the airbag device of Example 2. [Figure 14] It is an explanatory diagram schematically explaining the state in which the airbag in the airbag device of Example 2 is deployed and inflated. [Figure 15] It is an explanatory diagram schematically explaining the state of the flap, strap, and fixing material in the airbag device of Example 3 as seen from the outside of the airbag. [Figure 16] It is a graph showing the results of the evaluation test. [Figure 17] It is a graph showing the results of the evaluation test.

Modes for Carrying Out the Invention

[0018] The airbag device of the present invention comprises an airbag having an open vent hole, a flap attached to the airbag and covering the vent hole, a strap extending from the flap and fixed to a strap attachment portion to fix the flap in a closed position that closes the vent hole, and a fixing material for fixing the strap to the strap attachment portion. In the airbag device of the present invention, the vent hole is closed by the flap in the closed position.

[0019] The airbag device of the present invention further comprises a heating device. The heating device releases the strap by causing the fixing material to break due to heat. Herein, in this specification, "breaking" includes both cutting an object using a blade and cutting an object without using a blade. Furthermore, as described above, a heating device for breaking a strap by heat can be called a breaking device. In addition, if the airbag device of the present invention is equipped with a cap as described later, the breaking device can be said to include the cap and the heating device.

[0020] In the airbag device of the present invention, the heat generated by the heating device causes the fixing material to break. This frees the strap, and further frees the flap that was fixed to the strap attachment part via the strap, causing the flap to change position from a closed position that closes the vent hole to a position that opens the vent hole (hereinafter referred to as the open position as needed).

[0021] In the airbag device of the present invention, the heat generated by the heating device causes the fixing material to rupture. For this reason, the rupture device that ruptures the strap in the airbag device of the present invention has a simple structure, and the operating mechanism of the rupture device is also simple.

[0022] The airbag device of the present invention will be described below for each of its components. Unless otherwise specified, the numerical range "x~y" described herein includes a lower limit x and an upper limit y. Furthermore, new numerical ranges can be constructed by arbitrarily combining these upper and lower limits, as well as the numerical values ​​listed in the examples. Additionally, any numerical values ​​arbitrarily selected from any of the above numerical ranges can be used as the upper and lower limits of a new numerical range.

[0023] The airbag device of the present invention comprises an airbag, a flap, a strap, a fixing material, and a heating device. Furthermore, the airbag device of the present invention may include a cap, which will be described later. As previously stated, a device for rupturing the fixing material, including the heating device, is referred to as a rupturing device. This rupturing device may include a cap.

[0024] An airbag is a hollow, bag-like device installed in a vehicle to protect occupants in the event of an impact such as a collision. While the airbag may be placed anywhere in the vehicle, it is particularly preferable that it be installed between the occupant and the windshield, for example, on the steering wheel or on the back of the instrument panel, specifically in the area in front of the passenger seat.

[0025] Airbags are connected to an inflation fluid source and deploy and inflate upon impact, receiving the supply of inflation fluid, but are normally folded and stored. For this reason, it is preferable to select an airbag material that is both foldable and deployable. Specifically, it is preferable to select an airbag material that is flexible and high-strength, and for example, woven fabrics using high-strength resin fibers such as polyester or polyamide can be used particularly suitably.

[0026] The airbag in the airbag device of the present invention has an open vent hole. The airbag may have only one vent hole or may have multiple vent holes. The vent hole only needs to connect the inside and outside of the airbag and be able to discharge the inflation fluid inside the airbag to the outside, and its shape is not particularly limited. If the airbag has multiple vent holes, each vent hole may have the same shape or different shapes.

[0027] The flap is attached to the airbag and covers the vent holes described above. In the airbag device of the present invention, if the airbag has multiple vent holes, the flap may cover all of the vent holes. Alternatively, the flap may cover only some of the vent holes, leaving the remaining vent holes uncovered.

[0028] The flap only needs to be able to cover the vent hole when closed and to be able to open the vent hole when open. Therefore, the shape and material of the flap are not particularly limited, but it is preferable that it folds together with the airbag and does not hinder the deployment and inflation of the airbag. As for the material of such a flap, it is preferable to select a material that is flexible and high strength, and it is particularly preferable to select a woven fabric using high-strength resin fibers such as polyester or polyamide, similar to the airbag.

[0029] Any method of attaching the flap to the airbag is acceptable, as long as it does not hinder the deployment or inflation of the airbag. For example, the airbag and flap may be molded as a single unit, or the flap may be molded separately from the airbag and then sewn, glued, or welded to the airbag.

[0030] The flap may cover the vent hole inside the airbag, or it may cover the vent hole outside the airbag.

[0031] The strap only needs to extend from the flap and be secured to the strap attachment point by a fastening material, and can take the shape of a cord or strip, but is not limited to these.

[0032] The strap and flap may be formed as a single unit, or the strap may be formed separately from the flap and then sewn, glued, or welded to the flap. For the strap material, a flexible and high-strength material is preferable, and similar to the flap, a woven fabric using high-strength resin fibers such as polyester or polyamide is particularly preferable. For the fastening material, any material that can be broken by heat is acceptable, and a flexible and high-strength material is preferable. For the fastening material, a thermoplastic high-strength resin fiber such as polyester, polyamide, or polyethylene terephthalate is particularly preferable.

[0033] The attachment point for the strap to which the strap is secured may be part of the airbag device of the present invention, or it may be a vehicle component or interior part located near the airbag device of the present invention. For example, if the airbag device of the present invention is mounted on the steering wheel, the strap may be secured to the steering wheel, or to a base for attaching the airbag of the present invention to the steering wheel. Alternatively, it may be secured to the airbag itself. In each of these cases, the steering wheel, base, or airbag becomes the attachment point for the strap.

[0034] The strap is secured to the strap attachment point by a fastening material. The fastening material should be selected from an appropriate material and shape depending on the positional relationship between the strap and the strap attachment point, their materials, and their shapes. For example, if the strap attachment point is an airbag, the fastening material is preferably in the form of a sewing thread that sews the strap to the airbag. In this case, if the fastening material in the form of a sewing thread is to be ruptured by the heat of the heating element, it is particularly preferable that the fastening material be made of a material that is easily ruptured by heat, such as a sewing thread made of thermoplastic resin. In this specification, "sewing thread" refers to a thread that can be used for sewing, and does not limit its material, spinning method, fiber length, etc.

[0035] It should be noted that the fastening material in this invention is not limited to the sewing thread described above. In other words, the fastening material may take other shapes such as string or tape, or it may be fixed to the strap attachment point other than the airbag by a method other than sewing. For example, the fastening material may be tape-shaped and welded or bonded to the strap and the airbag which serves as the strap attachment point. Alternatively, the fastening material may be a thin cord formed integrally with the strap and may be welded or bonded to the airbag which serves as the strap attachment point, or it may be fastened to the base or steering wheel. In any case, it is particularly preferable that the fastening material has a shape that is more easily broken than the strap, for example, a shape that is thin, narrow, or sparse.

[0036] The strap may be secured to the outside of the airbag or to the inside of the airbag.

[0037] The rupture device requires a heating device and preferably includes a cap. The heating device is preferably a so-called ignition device having a heating element, also known as a squib, initiator, or igniter. In a typical squib, the heating element containing the filament generates heat upon energization; however, the mechanism by which the heating element generates heat in the airbag device of the present invention is not limited to this. Furthermore, the heating temperature of the heating element only needs to be high enough to break the fixing material; for example, if the fixing material is made of thermoplastic resin, the temperature should be above the softening temperature of that thermoplastic resin.

[0038] The rupture device may be located inside the airbag or outside the airbag. Of course, part of the rupture device may be located inside the airbag and the rest outside the airbag.

[0039] The airbag device of the present invention may include a cap as a rupture device in addition to the heating device described above. The cap has a cylindrical portion that surrounds the heating element of the heating device. Since the heating device is designed to break the fixing material, the cap secures the heating device around the fixing material that is to be broken. The cylindrical portion of the cap opens towards the fixing material.

[0040] By fixing the heating device around the fixing material using the cap described above, the heating device can be positioned relative to the fixing material. As a result, the heat generated by the heating element is supplied to the fixing material reliably without escaping from it.

[0041] Furthermore, because the cylindrical portion surrounds the heat-generating element and opens towards the fixing material, at least a portion of the heat transfer path from the heat-generating element to the fixing material is demarcated from the outside world, i.e., from outside the cylindrical portion. As a result, the heat generated by the heat-generating element is less likely to escape to the outside world and is supplied to the fixing material in a sufficient amount. Therefore, with the breaking device having the cap described above, the heat-generating part can reliably break the fixing material, and the strap can be released from its attachment to the strap attachment part, thereby reliably freeing the strap.

[0042] The cap has the function of fixing the above-mentioned heating device around the fixing material, and also has a cylindrical portion that surrounds the heating element of the heating device and opens toward the fixing material. Hereinafter, the portion of the cap that fixes the heating device around the fixing material may be referred to as the heating device fixing portion, as needed.

[0043] The position of the heating device relative to the fixing material is not particularly limited, as long as it is at a position where the heat generated by the heating element of the heating device can rupture the fixing material. The distance between the heating element and the fixing material is also not particularly limited, as long as it is at a distance where the heat generated by the heating element can rupture the fixing material, and should be set appropriately depending on the magnitude of the thermal energy generated by the heating element, the material and shape of the fixing material, etc.

[0044] The heating device fixing part may be used to fix the heating device around the fixing material in any way. For example, if the airbag device of the present invention is mounted on a steering wheel, the heating device fixing part may be fixed directly to the steering wheel, or it may be fixed to a base for attaching the airbag of the present invention to the steering wheel. The heating device fixing part is not limited to these and may be fixed to other mating materials. Methods for fixing the heating device fixing part to a mating material include, but are not limited to, bolt fixing, adhesive bonding, welding, engagement using engaging members such as pins, etc.

[0045] The cylindrical portion only needs to be cylindrical in shape so as to surround the heating element of the heating device, and may be cylindrical or rectangular in shape, for example. In order to transfer the heat generated by the heating element to the fixing material with minimal loss, it is preferable that the distance from the heating element to the cylindrical wall be constant, and in this respect, it is preferable for the cylindrical portion to be cylindrical.

[0046] The height of the cylindrical portion may be constant in the circumferential direction, or it may differ from other parts in the circumferential direction. Preferably, the cylindrical portion has a part in its circumferential direction where the height is lower than other parts. This lower part may be called a notch, and the other parts may be called the general part.

[0047] When the cylindrical portion has a notched section and a general section, the appearance of the cylindrical portion is partially different, which has the advantage of making it easy to position the cap and the heating device when assembling them together.

[0048] Furthermore, for example, if the portion of the cylindrical section facing the airbag is cut out, the cylindrical section will not come into contact with the airbag when the airbag deploys and inflates, or the portion of the cylindrical section that comes into contact with the airbag will be small. This has the advantage of suppressing interference between the cylindrical section and the airbag when the airbag deploys and inflates.

[0049] Considering that the cylindrical portion comes into contact with the airbag during airbag deployment and inflation, it is preferable that the notched portion and the general portion be smoothly continuous. For example, it is particularly preferable that the notched portion has an inclined wall shape in which the cylindrical height gradually increases from the bottom of the notch, which is the lowest part of the notch, to the top of the notch, which is the part of the notch that is continuous with the general portion.

[0050] The airbag device of the present invention may include an inflation fluid source for supplying inflation fluid to the airbag. The source of the expanding fluid is preferably an inflator that generates gas as the expanding fluid, but in some cases, it may also generate an expanding fluid other than gas, such as a liquid or gel.

[0051] The inflation fluid source can be any device for supplying inflation fluid to the airbag. For example, it may be a so-called pyrotype device having a gas generating agent that generates gas as inflation fluid, or it may be a so-called hybrid type device that ruptures the bulkhead of a high-pressure vessel and supplies the gas contained in the high-pressure vessel. The inflation fluid source may be located entirely outside the airbag, or partially or entirely inside the airbag.

[0052] The airbag device of the present invention may comprise other components. Examples of such other components include a retainer that houses at least a portion of the inflation fluid source, a cover that surrounds at least a portion of the airbag, and a wire harness for electrically connecting the inflation fluid source and the airbag control device. However, the airbag device of the present invention is not limited to these and may comprise other components.

[0053] Herein, the above-mentioned expansion fluid source may have a heating device for generating the expansion fluid. This heating device is provided separately from the heating device of the rupture device described above. Hereinafter, the heating device of the expansion fluid source may be referred to as an expansion fluid generating heating device, an expansion fluid squib, etc., as needed. The heating device for generating the expansion fluid may have the same structure as the heating device for the rupture device.

[0054] The heating device of the rupture device does not participate in the generation of the expansion fluid. Furthermore, if the expansion fluid generated by the expansion fluid source is exposed to the heating device of the rupture device, there is a risk of heat loss in the heating device of the rupture device. For this reason, in the airbag device of the present invention, it is preferable to isolate the heating device of the rupture device from the above-mentioned expansion fluid source. Specifically, it is preferable that the airbag device of the present invention has a vertical wall between the heating device of the rupture device and the above-mentioned expansion fluid source.

[0055] The height of the vertical wall is not particularly limited, but it is preferable that it be high enough to cover the gas outlet, such as an orifice, in the expansion fluid source. Even a small vertical wall will have the effect of obstructing the gas flow path from the expansion fluid source to the heating device of the rupture device.

[0056] The airbag device of the present invention will be described below with specific examples.

[0057] (Example 1) The airbag system in Example 1 is a driver's side airbag mounted on the vehicle's steering wheel. Figures 1 and 2 show schematic diagrams illustrating the deployment and inflation of the airbag in the airbag device of Example 1. Figures 1 and 2 represent the airbag device of Example 1 cut at different points. Figure 3 shows an enlarged view of the main part of Figure 1. Figure 4 shows a schematic diagram illustrating the unit of the airbag, flap, strap, inflation fluid source, and case in the airbag device of Example 1. Figure 5 shows a schematic diagram illustrating the cap in the airbag device of Example 1. Figure 6 shows a schematic diagram illustrating the flap, strap, and fixing material of the airbag device of Example 1 as seen from the outside of the airbag. Figures 7 to 12 show schematic diagrams illustrating the opening and closing of the flap through the active vent hole of the airbag in the airbag device of Example 1. Figure 8 shows the active vent hole and flap shown in Figure 7 as seen from the back. Figure 10 shows the active vent hole and flap shown in Figure 9 as seen from the back. Figure 12 shows the active vent holes and flaps shown in Figure 11, viewed from the reverse side.

[0058] As shown in Figure 1, the airbag device 1 of Embodiment 1 comprises an airbag 2, an inflation fluid source 3, a flap 4, a strap 5, a fixing material 50, a rupture device 6, a case 7, and a base 8.

[0059] In the airbag device 1 of Example 1, the inflation fluid source is an inflator 3 that generates gas as the inflation fluid, and includes an inflation fluid generating squib (not shown) for initiating gas generation. The inflator 3 has a gas outlet 31 for blowing out the gas, and the inflation fluid generating squib is connected to a control device (not shown) for deploying and inflating the airbag 2, and operates on power supply.

[0060] The airbag 2 is a hollow bag, and the gas outlet 31 of the inflator 3 described above is connected to the opening 20 of the airbag 2, allowing gas, or inflation fluid, to be supplied to the inside of the airbag 2.

[0061] As shown in Figures 7 and 8, the airbag 2 is provided with multiple vent holes 21. Each vent hole 21 is a roughly circular opening that connects the inside and outside of the airbag 2.

[0062] One of the vent holes 21 is referred to as the active vent hole 21A. The other vent holes 21 are referred to as general vent holes 21G. As will be described later, the active vent hole 21A is covered and closed by the flap 4 in the closed position. The general vent holes 21G are always open.

[0063] A flap 4 is sewn around the active vent hole 21 of the airbag 2. The flap 4 is made of the same nylon fabric as the airbag 2 and is roughly triangular in shape. The sewing thread 45 that sews the flap 4 to the airbag 2 is also made of nylon.

[0064] As shown in Figure 8, one side of the roughly triangular flap 4 is sewn linearly to the inner surface of the airbag 2 around the vent hole 21, and a strap 5 extends from the corner opposite that side.

[0065] The strap 5 is made of the same nylon fabric as the airbag 2 and flap 4, and is in the shape of a narrow strip. One end of the strap 5 is integrated with the flap 4, and the other end of the strap 5 is sewn and fixed inside the airbag 2. As a result, the flap 4 is fixed in a closed position (Figures 7 and 8) inside the airbag 2, covering the active vent hole 21A and closing the vent hole 21. In the airbag device 1 of Embodiment 1, the airbag 2 itself is the attachment point for the strap. The sewing thread used to sew the strap 5 to the airbag 2 is the fixing material 50. The fixing material 50 is made of nylon thread.

[0066] As shown in Figure 6, the fastening material 50 is sewn to the airbag 2 and the strap 5 so that it passes through them. Therefore, part of the fastening material 50 is exposed on the inside of the airbag 2, and the other part is exposed on the outside of the airbag 2.

[0067] The rupture device 6 has a heating device 60 and a cap 61 and is located outside the airbag 2. The heating device 60 is a squib. As shown in Figure 3, the heating device 60 has a heating element 60H and is connected to a power supply (not shown) and the control device (not shown) described above. Note that the heating device 60 is separate from the squib for generating the expansion fluid described above.

[0068] The heating device 60 is attached to the cap 61. As shown in Figure 5, the cap 61 has a heating device fixing portion 62 and a cylindrical portion 65, which will be described later. The heating device fixing portion 62 is fitted onto the base 8 for attaching the airbag device 1 of Embodiment 1 to the steering wheel 90. As a result, the heating device 60 is fixed around the fixing material 50 via the cap 61, with the heating portion 60H facing the fixing material 50.

[0069] The cylindrical portion 65 of the cap 61 has a nearly circular cross-section. The cylindrical portion 65 extends toward the fixing material 50 while surrounding the heating device 60, and opens toward the fixing material 50. The heating element 60H of the heating device 60 is also surrounded by the cylindrical portion 65. As shown in Figures 1 to 3, in the airbag device 1 of Embodiment 1, the cylindrical height of the cylindrical portion 65 is constant in the circumferential direction of the cylindrical portion 65.

[0070] The airbag 2, flap 4, strap 5, and inflation fluid source 3 described above are assembled into a unit in case 7 (Figure 4). Case 7 has a pad 7U and a bag plate 7L. The inflation fluid source 3 is located on the bag plate 7L side, and the airbag 2 is located on the pad 7U side. The flap 4 and strap 5 are located inside the airbag 2. As a result, the airbag 2, flap 4, strap 5, and inflation fluid source 3 are sandwiched between the pad 7U and the bag plate 7L. Case 7 is fixed to a base 8.

[0071] The base 8 is provided with a vertical wall 70 that extends toward the pad 7U. This vertical wall 70 is of a height that covers the orifice 35 of the inflator 3 and is interposed between the heating device 60 and the inflator 3, as shown in Figure 3.

[0072] The operation of the airbag device 1 in Example 1 will be described below.

[0073] When an impact such as a collision occurs to a vehicle equipped with the airbag device 1 of Example 1, the control device (not shown) activates the squib for generating the expansion fluid (not shown), causing the inflator 3 to generate gas, which is the expansion fluid. The gas generated by the inflator 3 is supplied to the inside of the airbag 2. As a result, the airbag 2 deploys and inflates. At this time, the flap 4 is in the closed position and the active vent hole 21A of the airbag 2 is covered by the flap 4 (Figures 7 and 8).

[0074] Immediately after airbag 2 deploys and inflates, the control device activates the heating device 60 of the rupture device 6. This causes the heating element 60H of the heating device 60 to heat up. The heat generated by the heating device 60 is supplied to the fixing material 50 from the outside, i.e., the back side, of the airbag 2 through the inside of the cylindrical portion 65. As a result, the fixing material 50 is heated. Since the fixing material 50 is made of nylon, which is a thermoplastic resin, it is heated and ruptures. As previously described, the sewing thread, or fixing material 50, is sewn together so as to penetrate the airbag 2 and the strap 5, with a portion of it exposed on the outside of the airbag 2. Therefore, by rupturing the fixing material 50 on the outside of the airbag 2 with heat, the strap 5 is released and becomes free. In the airbag device 1 of this embodiment, the heating device 60 is set to generate heat and cause the fixing material 50 to rupture at the moment the occupant collides with the airbag 2.

[0075] Before deployment, i.e., when airbag 2 is folded, the flap 4 is secured in the closed position by the strap 5. Even when airbag 2 is deployed and inflated, the flap 4 remains secured in the closed position by the strap 5. When the fixing material 50 breaks, the strap 5 becomes free, and as a result, the flap 4 becomes free.

[0076] At this time, the gas generated by the inflator 3 continues to be supplied to the inside of the airbag 2. As a result, the gas pressure from the inside to the outside of the airbag 2 pushes the flap 4 outwards, causing it to start changing position from the open position that closes the active vent hole 21A to the open position that opens the active vent hole 21A (Figures 9 and 10). When the flap 4 and the remaining part of the strap 5 connected to it come out of the airbag 2 through the active vent hole 21A, the active vent hole 21A opens (Figures 11 and 12). At this time, the flap 4 can be said to be positioned in the open position that opens the active vent hole 21A.

[0077] When the flap 4 opens the active vent hole 21A, the gas inside the airbag 2 can escape to the outside of the airbag 2 through the active vent hole 21A. As a result, the gas pressure inside the airbag 2 is sufficiently reduced, and the reaction force imposed on the occupant by the airbag 2 is also sufficiently reduced.

[0078] In the airbag device 1 of Example 1, the structure of the breaking device 6 is simple, and the operating mechanism of the breaking device 6 is also simple, as the fixing material 50 to be broken is heated and broken by the heating device 60.

[0079] Then, the cap 61 of the breaking device 6 positions the heating device 60 relative to the fixing material 50, and the heating element 60H of the heating device 60 supplies a sufficient amount of heat to the fixing material 50. As a result, according to the airbag device 1 of this embodiment, the heating element 60H of the heating device 60 reliably breaks the fixing material 50, and the strap 5 can be released with sufficient reliability.

[0080] Furthermore, the airbag device 1 of Example 1 has a vertical wall 70 between the heating device 60 of the rupture device 6 and the orifice 35 of the inflator 3. This obstructs the gas flow path from the inflator 3 to the heating device 60. This avoids the problem of the heating device 60 being inhibited by the gas, and the heating part 60H of the heating device 60 rises to a rapid and sufficient temperature. As a result, with the airbag device 1 of Example 1, it is possible to heat and rupture the fixing material 50 with the heating device 60 at the desired timing, thereby freeing the strap 5, and consequently, opening the active vent hole 21A at the desired timing.

[0081] (Example 2) The airbag device 1 of Example 2 is substantially the same as the airbag device 1 of Example 1, except for the shape of the cylindrical portion 65 in the cap 61. Figure 13 shows a schematic diagram illustrating the cap 61 in the airbag device 1 of Example 2. Figure 14 shows a schematic diagram illustrating the deployment and inflation of the airbag 2 in the airbag device 1 of Example 2.

[0082] As shown in Figure 13, the cap 61 in the airbag device 1 of Example 2 differs from the cap 61 in the airbag device 1 of Example 1 in the shape of the cylindrical portion 65. Specifically, the cylindrical portion 65 of the cap 61 has a cylindrical shape with a roughly circular cross-section. The cylindrical portion 65 has a general portion 66 and a notched portion 67. The general portion 66 is a part of the cylindrical portion 65 in the circumferential direction where the cylindrical height is substantially constant. The notched portion 67 is the remaining part of the cylindrical portion 65 in the circumferential direction where the cylindrical height is lower than that of the general portion 66.

[0083] The notched portion 67 has a roughly V-shaped inclined wall form when viewed from the side. More specifically, the height of the cylindrical portion 65 gradually increases from the bottom portion 67B of the notch, which is the lowest part of the notch 67, towards the top portion 67T of the notch, which is the part of the notch 67 that is continuous with the general portion 66 described above.

[0084] Because the cylindrical portion 65 has a notch portion 67, when manufacturing the airbag device 1 of Embodiment 1, the worker assembling the heating device 60 and the cap 61 can visually and easily recognize the orientation of the cylindrical portion 65. This makes it easier to assemble the heating device 60 and the cap 61 in the correct orientation, and makes it possible to position the heating device 60 and the cap 61 easily and precisely.

[0085] Furthermore, as shown in Figure 13, by providing a notch 67 in the cylindrical portion 65 that forms an inclined wall, the cylindrical portion 65 is less likely to interfere with the deployed and inflated airbag 2, as shown in Figure 14. This has the advantage of allowing the deployment and inflation of the airbag 2 and the rupture of the fixing material 50 by the heating device 60 to proceed smoothly.

[0086] (Example 3) The airbag device 1 of Example 3 is substantially the same as the airbag device 1 of Example 1, except for the shape and position of the fixing material 50 and the relationship between the strap 5 and the airbag 2. Figure 15 shows a schematic diagram illustrating the view of the flap 4, strap 5, and fixing material 50 of the airbag device in Example 3 from the outside of the airbag 2.

[0087] As shown in Figure 15, the strap 5 in the airbag device 1 of Embodiment 3 is a thin strip, similar to the strap 5 in the airbag device 1 of Embodiment 1, and one end is integrated with the flap 4. The airbag 20 in the airbag device 1 of Embodiment 3 is provided with a through hole, and the other end of the strap 5 is exposed to the outside of the airbag 2 through the through hole in the airbag 2.

[0088] The fixing material 50 is an adhesive tape, and the portion of the strap 5 that is exposed to the outside of the airbag 2 is attached to the airbag 2. As a result, the other end of the strap 5 is fixed to the outside of the airbag 2.

[0089] In the airbag device 1 of Example 3, as in the airbag device 1 of Example 1, the heat generated by the heating device 60 is supplied to the outside of the airbag 2 through the inside of the cylindrical portion 65.

[0090] In the airbag device 1 of Example 3, since the fixing material 50 is located on the outside of the airbag 2, the heat generated by the heating device 60 is supplied directly to the fixing material 50, heating it. Because the fixing material 50 is made of thermoplastic resin, it is heated and breaks. As a result, the strap 5 is released and becomes free, and the flap 4 also becomes free. Consequently, the flap 4 opens the active vent hole 21A (not shown), the gas pressure inside the airbag 2 is sufficiently reduced, and the reaction force imposed on the occupant by the airbag 2 is also sufficiently reduced.

[0091] In the airbag device 1 of Example 3, similar to the airbag device 1 of Example 1, the fixing material 50 to be ruptured is heated and ruptured by the heating device 60. Therefore, the structure of the rupturing device 6 can be simplified, and the operating mechanism of the rupturing device 6 can also be simplified.

[0092] [Evaluation Test] For both the integrated heating element 60 and cap 61 of Example 1 (i.e., the breaking device of Example 1) and the heating element 60 included in the breaking device, the temperature change from the time of ignition of the heating element 60 at the position corresponding to the fixing material 50 was calculated by simulation. The results are shown in Figure 16. In Figure 16, the vertical axis represents temperature (°C), and the horizontal axis represents the elapsed time (milliseconds) from the time of ignition (0 milliseconds). Furthermore, Figure 17 shows the thermoelectric product from the time of ignition to 3 milliseconds in the graph shown in Figure 16.

[0093] In the case of the heating device 60 alone, as shown in Figure 16, the temperature is high immediately after ignition, but then it drops rapidly, and as shown in Figure 17, the thermopultality is low up to 3 milliseconds. The rapid temperature drop described above is presumed to be due to the heat generated in the heating section 60H upon ignition of the heating device 60 being absorbed by the housing of the heating device 60.

[0094] On the other hand, in the fracture device of Example 1, although the temperature immediately after ignition is relatively low as shown in Figure 16, the subsequent temperature drop is small, and the thermoimpulse up to 3 milliseconds is high as shown in Figure 17. The reason why the temperature drop after ignition was small in the fracture device of Example 1 is not clear, but it is presumed to be due to the fact that the heating element 60H of the heating device 60 is surrounded by the cylindrical part 65 of the cap 61. In other words, in the fracture device of Example 1, it is presumed that the heat generated in the heating element 60H by the ignition of the heating device 60 is retained inside the cylindrical part 65 and is not easily diffused to the outside of the cylindrical part 65. These results show that the fracture device of Example 1 can provide a sufficient amount of heat to the fixing material 50, making it possible to efficiently heat and fracture the fixing material 50.

[0095] The heating device 60 alone, without the cap 61, finished spraying the ignition agent 0.68 milliseconds after ignition. Because the heating device 60 is exposed, it is thought that the heat generated by the heating device 60 dissipated into the outside environment immediately after it was generated.

[0096] In contrast, in the fracture device of Example 1, which includes the cap 61 and the heating device 60, it is considered that the heat generated by the heating device 60 remained in the cylindrical portion 65 for more than 3.0 milliseconds after ignition. In other words, it is considered that the heat generated by the heating device 60 was accumulated in the cylindrical portion 65. This confirms that, according to the airbag device 1 of Example 1, the heat generated by the heating device 60 can be utilized efficiently, and a sufficient amount of heat can be supplied to the fixing material 50 that is to be heated.

[0097] Although the present invention has been described above, the present invention is not limited to the embodiments described above, and it is possible to implement the invention by appropriately extracting and combining the elements described in the embodiments, and to make various modifications without departing from the spirit of the present invention. Furthermore, the specification of this invention discloses not only the reference relationships of each claim as initially filed, but also a technical concept that appropriately combines the matters described in each claim. [Explanation of symbols]

[0098] 1: Airbag system 2: Airbag 21: Vent hole 3: Expansion fluid source (inflator) 4: Flap 5: Strap 50: Fixing material 2: Attachment part for strap (airbag) 60: Heating device 60H: Heating element 61: Cap 65: Cylinder 66: General section 67: Notched section 67B: Notch bottom 67T: Notch top 70: Vertical wall

Claims

1. An airbag having an open vent hole, A flap attached to the airbag and covering the vent hole, A strap extending from the flap and fixed to the strap attachment point, which positions the flap in a closed position that closes the vent hole, A fixing material for securing the strap to the strap attachment part, A heating device that frees the strap by causing the fixing material to break due to heat, The heating device comprises a cylindrical portion surrounding the heating element and a cap for fixing the heating device in place, The cap secures the heating device around the fixing material. The cylindrical portion is It has a general portion which is part of the circumferential direction, and a notched portion which is another part of the circumferential direction and has a lower cylindrical height than the general portion. An airbag device that opens toward the aforementioned fixing material.

2. The airbag device according to claim 1, wherein the fixing material is a sewing thread used to sew the strap to the airbag.

3. The airbag device according to claim 1 or claim 2, further comprising a vertical wall between the heating device and the inflation fluid source that supplies inflation fluid to the airbag.

4. The airbag device according to claim 1 or claim 2, wherein the notch is shaped like an inclined wall, with the cylindrical height gradually increasing from the bottom of the notch, which has the lowest cylindrical height, toward the top of the notch, which is continuous with the general part of the notch.

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