Formed airbag chute with door reinforced by hollow channel

Abstract

This disclosure provides a "molded airbag chute with a door reinforced by a hollow channel". An airbag chute assembly for an automotive dashboard is injection molded to form an integral deployment chute, door, and attachment flange. The flange is attached to the dashboard around an opening in the dashboard. The tubular chute extends inwardly from the flange to a lower end and defines a deployment path along a longitudinal axis, the lower end being configured to receive an inflated airbag from an airbag module. A door wing is disposed at the upper end of the chute and is rotatable from the flange to protrude through the opening. The inner side of the door wing is subjected to the impact of the inflated airbag and has multiple raised reinforcing ribs. The door wing has at least one closed-section hollow channel projecting from the inner side to a channel height extending beyond the reinforcing ribs formed by gas-assisted injection molding.

Description

Technical Field

[0001] The present invention relates generally to automotive air bag systems and, more particularly, to a concealed air bag deployment door formed by an instrument panel substrate and a molded air bag chute. Background Art

[0002] Airbag deployment chute assemblies have been put into commercial use for the passenger side of the dashboard of a motor vehicle. The chute assembly connects the airbag module (generally including a folded canvas bag and a chemical propellant for inflating the bag when needed) to the door support plate or base plate of the dashboard. The typical structure of the chute assembly includes a tubular chute outer wall, one or more door wings, a flange around the door area, and one or more hinge members or areas connecting the one or more door wings to the outer wall and the flange.

[0003] For styling purposes, it is desirable that the airbag deployment door in the instrument panel is not visible when viewed from the passenger compartment. In other words, the visible or "Class A" surface of the instrument panel is preferably seamless. Therefore, a pre-weakened seam is required in the substrate (on the "Class B" side) to facilitate tearing the door open during airbag deployment. In order to prevent torn or broken substrate fragments from flying into the passenger compartment, one or more door wings of the chute are attached to the substrate door area so that the door wings and hinges act as tethers. A common method of attaching the chute door wings and flanges to the substrate is by plastic welding, such as vibration welding, hot plate welding, etc.

[0004] A typical passenger air bag door is designed to transfer the air bag pressure load generated by the inflating air bag to the tear seam to release the door as quickly as possible during deployment. Clean and rapid separation of the tear seam helps avoid material fragmentation during air bag deployment. A stiffer door can transfer the air bag load to the tear seam faster and with less risk of fragmentation than a more flexible door. Therefore, one of the challenges in passenger air bag door design is to develop a slide and door system with sufficient rigidity to effectively transfer the air bag deployment forces to the tear seam while keeping production costs and weight low.

[0005] A typical airbag chute structure is formed as a one-piece thermoplastic injection molded part that combines a flange or collar for attachment to the instrument panel substrate, a door connected to the flange by a hinge, and a chute for connecting to the airbag module and providing a deployment path to the door. A common material is TPO (thermoplastic olefin), such as Dexflex TM, or other materials that exhibit excellent ductility at extremely low temperatures of at least -30°C and good toughness at high temperatures of at least 90°C (e.g., TPE or TEO). Since these materials have a certain flexibility, the stiffness of the door is increased by adding ribs and / or increasing the material thickness. Since the slide assembly is injection molded, a mold lock condition must be avoided during the molding process, which limits the range of compatible rib shapes and sizes that can be used. Therefore, known methods may not achieve the desired stiffness and may result in other disadvantages, such as increased cost and weight (e.g., an undesirable stiffness-to-weight ratio).

[0006] Due to the relative positions of the airbag module and the deployment door and the orientation of the sculpted surfaces of the instrument panel, the inflating airbag produces an impact force on the door that is inclined relative to a direction perpendicular to the door. The present invention further recognizes that the known orientation results in a shortened moment arm of the resultant force (forces are concentrated near the door hinges), and that it is desirable to increase the moment arm. Summary of the invention

[0007] In one aspect of the present invention, an airbag chute assembly for an automotive instrument panel includes an outer flange configured to be attached to the instrument panel around a hole in the instrument panel. A tubular chute extends inwardly from the flange to a lower end and defines a deployment path along a longitudinal axis, the lower end being configured to receive an inflated airbag from an airbag module. A door wing is disposed at an upper end of the chute and is capable of rotating from the flange to be exposed through the hole. An inner side of the door wing is impacted by the inflated airbag and has a plurality of raised reinforcing ribs. The door wing has at least one closed cross-section hollow channel, the hollow channel protruding from the inner side to a channel height, the channel height extending beyond the reinforcing ribs. BRIEF DESCRIPTION OF THE DRAWINGS

[0008] FIG. 1 is a perspective view of an automotive instrument panel system showing the passenger air bag deployment area.

[0009] FIG. 2 is a cross-sectional view taken along line 2 - 2 of FIG. 1 , illustrating a conventional passenger airbag system.

[0010] FIG. 3 is a cross-sectional perspective view of the airbag chute assembly of FIG. 2 .

[0011] 4 is a diagram showing airbag inflation and resulting door pivoting movement after tearing of a door seam.

[0012] Figure 5 is a diagram showing an improved door profile for improving door seam tearing efficiency in the present invention.

[0013] FIG. 6 shows a force diagram and moment arms according to a conventional door configuration.

[0014] Figure 7 A force diagram and moment arms according to an embodiment of the present invention are shown.

[0015] Figure 8 is a bottom perspective view of a preferred embodiment of an air bag chute assembly having a closed cross-section hollow channel for a reinforced door.

[0016] Fig. 9 yes Figure 8 Another bottom perspective view of the chute assembly.

[0017] Fig.10 yes Figure 8 Schematic side view of an impact airbag on a deployment door of a slide assembly.

[0018] Fig.11 yes Figure 8 A side cross-sectional view of the chute assembly.

[0019] Fig.12 yes Figure 8 A top view of the slide assembly.

[0020] Fig.13 yes Figure 8 A cross-sectional view of the other side of the slide assembly.

[0021] Fig.14 is a bottom perspective view showing another embodiment of an air bag chute assembly having a nested closed cross-section hollow channel for a reinforced door.

[0022] Fig.15 is a bottom view showing another alternative embodiment of a closed cross-section hollow channel for reinforcing a door.

[0023] Fig.16 is a bottom view showing another alternative embodiment of a closed cross-section hollow channel for reinforcing a door.

[0024] Fig.17 is along Fig.16 A cross-sectional view of the hollow channel along line 17-17.

[0025] Fig.18 is a bottom view showing another alternative embodiment of a closed cross-section hollow channel for reinforcing a door.

[0026] Fig.19 is along Fig.18 A cross-sectional view of the hollow channel along line 19-19. DETAILED DESCRIPTION

[0027] Referring now to FIGS. 1 to 3 , an instrument panel 10 includes a passenger airbag system having a hidden seam 11 defining a deployment door area 12. An instrument panel substrate 15 provides the instrument panel with the desired shape and rigidity. It is covered by a cover layer 16, which may include a conventional elastic material surface layer and a foam layer between the surface layer and the substrate 15. A chute 17 includes a tubular passage 18 and a deployment door wing 20 located at its upper end. The deployment door 20 is connected to the passage 18 along one side by a hinge 21. For example, a gap 22 may define an outer edge on three sides of the door 20. Instead of a gap, a pre-weakened seam may define a door hole that is opened only after breaking during deployment. The chute 17 includes a flange (collar) 23 surrounding the door 20. As better shown in FIG. 3 , the flange 23 and the door 20 may have a plurality of welding ribs 24 that are used to weld the chute 17 to the instrument panel substrate 15.

[0028] As shown in FIG. 2 , the instrument panel substrate 15 and the cover layer 16 may include a hidden seam 25 for tearing during the opening of the deployment door 20. The seam 25 defines a door aperture, which may be formed by mechanical or laser scoring prior to attaching the chute 17 by vibration welding. In some embodiments, the door aperture may be a complete opening in the substrate 15. An airbag module 27 is mounted to a plurality of holes 26 in the chute passage 18. The airbag module 27 includes a rigid box that houses a propellant source 30 and a folded bag (not shown) that, once inflated with gas from the propellant source 30, is directed to the door 20 along a deployment path defined by the passage 18. The airbag module 27 includes a plurality of hooks 31 that are received in a corresponding plurality of windows 26. Fasteners 32 couple the airbag module 27 to the cross member of the vehicle via a bracket.

[0029] To achieve the desired strength and appearance, the instrument panel substrate and the chute assembly may preferably be formed of a formable thermoplastic material. Preferred materials for the chute assembly include thermoplastic polyolefins (TPO), thermoplastic elastomers (TPE), and thermoplastic elastomer olefins (TEO). The most preferred material is TPO compounded with fillers that change the material's melting temperature, flexural modulus (i.e., stiffness), and other properties.

[0030] FIG. 4 depicts the action of an inflated airbag 33 impacting an airbag door wing 34 located between a hinge 35 and a tear seam 36 in a door aperture defined within a chute assembly outer flange / instrument panel substrate 37. The door wing 34 is substantially flat, but it may also include reinforcing ribs (not shown) as known in the art. In either case, the inner surface of the door 34 impacted by the airbag 33 is angled relative to the deployment direction of the airbag 33 (i.e., the longitudinal axis of the tubular chute is not perpendicular to the inner surface of the door). After the impact force of the airbag 33 successfully separates the tear seam 36, the door wing 34 pivots about the hinge 35 to an open position 38, exposing the airbag 33 to provide occupant restraint.

[0031] like Figure 5 As shown in FIG. 6 , the present invention improves the airbag door, wherein the door 40 between the hinge 41 and the tear seam 42 includes an internal "push surface" 43, the height of which from the outer surface of the door 40 increases in proportion to the distance from the pivot hinge 41. Due to the slope of the surface 43, it is less inclined relative to the longitudinal axis 44 of the airbag deployment path within the tubular chute. By arranging the push surface 43 to be more normal to (i.e., perpendicular to) the axis 44, a better force transmission to the tear seam 42 is obtained. By comparing FIG. 6 and FIG. Figure 7 This can be seen in Figure 4, because the inner surface of the door is tilted away from the airbag deployment path, the impact force of the inflating airbag on the door is concentrated toward the hinge, as shown in Figure 6. Therefore, with the door D pivoting about the hinge H, a series of effective force vectors range from a maximum force 45 closest to the hinge H to a minimum force 46 farthest from the hinge H. The effective moment arm 47 of the sum of the forces acts on the door D close to the hinge H and at a distance 48 from the tear seam. As shown in Figure 6, Figure 5 As shown, since the inner surface of the door is closer to perpendicular to the airbag deployment path, Figure 7 As shown, the impact force of the inflated airbag on the door is more constant between the hinge H and the tear seam. The effective moment arm 49 of the sum of the forces is farther away from the hinge H and acts on the door D at a distance 50 from the tear seam. As the moment arm 49 is offset away from the hinge H and closer to the tear seam, the force transmitted to the tear seam increases. Therefore, the seam can be separated more quickly and more evenly, the deformation of the slide assembly is smaller, and the material is less broken from the slide assembly, the dashboard, the surface layer and the foam. Although the reinforcing ribs already used on the inner side of the door wing can be configured to provide an inclined height, the effect on the force transmission will be minimal, and potential damage to the airbag may be undesirable. Therefore, a structure wider than the reinforcing rib is disclosed below. As shown in the embodiment described below, the inclined push surface does not need to involve the entire inner surface of the door wing. Only an area sufficient to transmit most of the force is required.

[0032] Reference Figure 8and Fig. 9 , the airbag chute assembly 51 has an outer flange 52 and a tubular chute 53, wherein the outer flange is configured to be attached to the instrument panel and the tubular chute extends inwardly from the flange 52. A door wing 54 is disposed at the upper end of the chute 53 and is rotatable about a hinge 58 so as to be exposed through a hole in the instrument panel (not shown). A plurality of reinforcing ribs 55 preferably extend in a raised manner from the inner side of the door wing 54 arranged in a grid structure. In order to provide even greater reinforcement, at least one closed cross-section hollow channel 56 is provided, which protrudes from the inner side of the door wing 54 to a channel height greater than the height of the ribs 55. As defined herein, "closed cross-section" means that each hollow channel defines a closed perimeter around the internal channel from beginning to end along the main structure of the channel as viewed in transverse cross-section, excluding the channel inlet and channel outlet at the opposite ends of the channel associated with the channel manufactured using gas-assisted injection molding as described below. In Figure 8 and Fig. 9 In the embodiment, a pair of U-shaped channels 56 and 57 are arranged side by side, and each channel 56 and 57 has a variable channel height that conforms to the inclined height profile, so that the pushing surface of the formed U-shaped channel is basically perpendicular to the longitudinal axis of the tubular slide 53.

[0033] In order to form the closed-section hollow channels 56 and 57 by gas-assisted injection molding, a pair of gas inlets 61 and 62 and a pair of gas outlets 63 and 64 are provided for the channels 56 and 57, respectively.

[0034] Fig.10 The advancing airbag front 65 during deployment is shown impacting the inclined height profile 66 of the closed cross-section hollow channels which act as a pushing surface substantially perpendicular to the longitudinal deployment axis of the airbag and produce improved force transfer for evenly tearing the tear seam.

[0035] exist Fig.11 In a cross-sectional view of , the hollow interior of the U-shaped channel 56 has a channel height extending from the top surface of the door wing 54, which varies between a short height 67 near the hinge edge 58 of the door wing and a larger height 68 away from the hinge edge 58. Preferably, the variable channel height follows a certain height profile, which makes the protruding side of the hollow channel 56 perpendicular to the longitudinal axis of the tubular chute 53. In addition, the reinforcing ribs 55 are preferably formed on the inner surface of the door wing both inside and outside the U-shaped profile of the channel 56. More specifically, the U-shaped hollow channel 56 includes side legs 70 and 71, which have a height that gradually increases away from the hinge edge 58. The far side 72 of the channel 56 completes the inclined portion. On average, the channel 56 can provide an aspect ratio of about 2:1. In a typical design, the channel can have a width of about 20 mm and a height of about 10 mm (e.g., a median height).

[0036] exist Fig.12 , the top side of the chute assembly 51 shows the gap 73 between the flange 52 and three sides of the door wing 54 excluding the hinge edge 58. Although not actually visible from the top, the location of the ribs 55 and closed cross-section hollow channels 56 and 57 protruding from the hidden side of the door wing 54 are indicated to show the increased degree of rigidity across the door wing 54, which results in improved deployment performance.

[0037] Fig.13 Another embodiment of the injection molded runner assembly 75 in 70 includes U-shaped closed cross-section hollow channels 76 and 77 protruding from the door wing front surface 78, which is disposed within a flange 79 at the end of a tubular runner 80. The runner 80 has a longitudinal axis that defines an airbag deployment path that is inclined relative to a plane defined by the door wing front surface 78. Preferably, the closed cross-section hollow channels 76 and 77 have a height profile that provides a push surface to the inflating airbag that is perpendicular to the longitudinal axis.

[0038] As in the previous embodiment, the closed cross-section hollow channels 76 and 77 are produced by gas-assisted injection molding. Channel 76 has an open inlet 81, which is connected to an open outlet 83 through the hollow interior of channel 76. Channel 77 has an open inlet 82, which is connected to an open outlet 84 through the hollow interior of channel 76. The arrow indicates the direction of inert gas flow during gas-assisted injection molding. This method known in the art includes a first step of injecting plastic material into the mold to fill all the expected solid areas of the molded part and partially fill the area intended to provide the cavity (i.e., the closed cross section, like the hollow channel of the present invention). While the injected plastic remains in a molten state, an inert gas (e.g., nitrogen) is injected and passed through the area intended to form the cavity. When the gas travels between the inlet 81 / 82 and the outlet 83 / 84, it forms hollow hollow channels 76 and 77 by displacing the molten material onto the corresponding mold surface. After cooling and demoulding (i.e., removal from the mold), a one-piece plastic body (including flanges, slides and door wings) is obtained, in which the inlet and outlet can remain open because the channel itself provides enhanced rigidity due to its structure. In the areas not occupied by channels 76 and 77, conventional reinforcing ribs shorter than channels 76 and 77 can also be included.

[0039] Many other arrangements of closed cross-section hollow channels for reinforcing the unfolding door wings can achieve the desired reinforcement. Fig.14 In the embodiment, the airbag chute assembly 85 includes a series of nested U-shaped hollow channels 86, 87 and 88 formed by gas-assisted injection molding. Fig.15, a slide assembly 90 is shown having a W-shaped hollow channel 91 formed by gas-assisted injection molding using a gas inlet 92 and a pair of gas outlets 93 and 94 .

[0040] like Fig.16 As shown, a series of side-by-side closed cross-section hollow channels 96, 97 and 98 parallel to the hinge edge are used in the chute assembly 95. Channels 96-98 can follow a wavy path to provide reinforcement on the door wing in multiple directions. In order to also provide a variable channel height that conforms to the height profile perpendicular to the longitudinal axis of the tubular chute, channels 96-98 preferably have different sizes protruding from the door wing 100, such as Fig.17 shown in cross section.

[0041] Fig.18 A similar arrangement in has a series of closed cross-section hollow channels 102, 103, 104 and 105 arranged side by side, perpendicular to the hinge edge in the chute assembly 101. Channels 102 to 105 may follow an undulating path to provide reinforcement on the door wing in multiple directions. To also provide a variable channel height that conforms to the height profile perpendicular to the longitudinal axis of the tubular chute, each channel has a corresponding slope. For example, channel 102 is at Fig.19 The hollow channel 102 has a hollow cavity 108 between a door wing front wall 106 and a protruding channel wall 107 which is inclined to provide a channel height which increases with increasing distance from the hinge edge.

Claims

1. An airbag chute assembly for a vehicle dashboard, comprising: an outer flange configured to be attached to the instrument panel about a hole in the instrument panel; a tubular chute extending inwardly from the outer flange to a lower end and defining a deployment path along a longitudinal axis, the lower end being configured to receive an inflated airbag from an airbag module; and A door wing is disposed at the upper end of the slide slot and is capable of rotating from the outer flange to be exposed through the hole, wherein the door wing has 1) an inner side with a plurality of raised reinforcing ribs to be impacted by the inflated airbag, and 2) at least one closed cross-section hollow channel, the closed cross-section hollow channel protruding from the inner side to a channel height, the channel height extending beyond the reinforcing ribs, wherein the height profile of the closed cross-section hollow channel is substantially perpendicular to the longitudinal axis.

2. The chute assembly of claim 1, wherein the longitudinal axis is inclined relative to the door wing, and wherein the channel height is variable so that it follows the height profile that is substantially perpendicular to the longitudinal axis.

3. The slideway assembly as claimed in claim 1, wherein the closed cross-section hollow channel has an open inlet and an open outlet, suitable for forming the closed cross-section hollow channel by gas-assisted injection molding.

4. The slideway assembly of claim 3, wherein the door wing has a hinge edge, wherein the closed cross-section hollow channel is U-shaped, the open inlet and the open outlet are adjacent to the hinge edge, and wherein the side legs of the U-shaped closed cross-section hollow channel have a channel height that increases with increasing distance from the hinge edge according to the height profile.

5. The slideway assembly of claim 3, wherein the door wing has a hinge edge, wherein the assembly has a plurality of closed cross-section hollow channels, each closed cross-section hollow channel extending substantially parallel to the hinge edge, and wherein the closed cross-section hollow channels have respective channel heights that increase with increasing distance from the hinge edge according to the height profile.

6. The chute assembly of claim 1 , wherein the assembly has a plurality of closed-section hollow channels, wherein the longitudinal axis is inclined relative to the door wing, and wherein each closed-section hollow channel has a respective channel height that follows a height profile that is substantially perpendicular to the longitudinal axis.

7. The chute assembly as claimed in claim 1, wherein the width of the closed cross-section hollow channel is greater than 150% of the maximum channel height.

8. A passenger airbag system, comprising: an instrument panel substrate defining an aperture; a slide assembly mounted at the hole; and an airbag module mounted to the chute assembly and including an inflatable airbag for deployment through the chute assembly and the aperture; The slide assembly comprises: an outer flange configured to be attached to the instrument panel about a hole in the instrument panel; a tubular chute extending inwardly from the outer flange to a lower end and defining a deployment path along a longitudinal axis, the lower end being configured to receive an inflated airbag from an airbag module; and A door wing is disposed at the upper end of the slide slot and is capable of rotating from the outer flange to be exposed through the hole, wherein the door wing has 1) an inner side with a plurality of raised reinforcing ribs to be impacted by the inflated airbag, and 2) at least one closed cross-section hollow channel, the closed cross-section hollow channel protruding from the inner side to a channel height, the channel height extending beyond the reinforcing ribs, wherein the height profile of the closed cross-section hollow channel is substantially perpendicular to the longitudinal axis.

9. A passenger airbag system as claimed in claim 8, wherein the longitudinal axis is inclined relative to the door wing, and wherein the channel height is variable so that it follows the height profile that is substantially perpendicular to the longitudinal axis.

10. The passenger airbag system of claim 8, wherein the closed-section hollow channel has an open inlet and an open outlet, adapted to be formed by gas-assisted injection molding.

11. A passenger airbag system as described in claim 10, wherein the door wing has a hinge edge, wherein the closed cross-section hollow channel is U-shaped, the open inlet and the open outlet are adjacent to the hinge edge, and wherein the side legs of the U-shaped closed cross-section hollow channel have a channel height that increases as the distance from the hinge edge increases according to the height profile.

12. A passenger airbag system as described in claim 10, wherein the door wing has a hinge edge, wherein the assembly has a plurality of closed-section hollow channels, each closed-section hollow channel extending substantially parallel to the hinge edge, and wherein the closed-section hollow channels have respective channel heights that increase with increasing distance from the hinge edge according to the height profile.

13. The passenger airbag system of claim 8, wherein the assembly has a plurality of closed-section hollow channels, wherein the longitudinal axis is inclined relative to the door wing, and wherein each closed-section hollow channel has a respective channel height that follows a height profile that is substantially perpendicular to the longitudinal axis.

14. The passenger airbag system of claim 8, wherein the closed cross-section hollow channel has a width greater than 150% of a maximum channel height.

15. A method for manufacturing an airbag chute assembly, comprising: injecting molten thermoplastic into a mold cavity, the mold cavity defining a unitary body having an outer flange, a tubular runner, and a door wing with a plurality of ribs on an inner surface, wherein the tubular runner defines a deployment path along a longitudinal axis; as well as An inert gas is injected between the inlet and outlet of the cavity to form a closed cross-section hollow channel protruding from the inner surface to a channel height extending beyond the ribs, wherein the closed cross-section hollow channel height profile is substantially perpendicular to the longitudinal axis.

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