JPH07232611A - Air bag cover - Google Patents

Abstract

PURPOSE:To provide such an air bag cover that fractures only a set thin-walled fracture part without generating any unnecessary crack so as to develop a bag and surely secure inflation and projection performance of the bag. CONSTITUTION:Arc stop circular parts 52 having diameters larger, than the width sizes of other parts in a plan view are provided in respective terminal edges of longitudinal thin-walled fracture parts 44, 46 formed on the rear side of a cover 40. Therefore, if force (stress) in developing fracture of the cover 40 acts on respective terminal edges of the longitudinal thin-walled fracture parts 44, 46, the stress is dispersed and eased at the stop circular parts 52, unnecessary enlargement of the crack is prevented, and the cover 40 fractures and inflates only at a prescribed part. Development position of the cover 40 can be thus decided surely and unconditionally so that inflation and projection performance of the bag can be surely secured.

Description

Detailed Description of the Invention

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to an airbag cover used in an airbag device provided on a steering wheel of an automobile.

[0002]

2. Description of the Related Art In an air bag device mounted on a steering wheel of an automobile, the bag is inflated at the time of sudden deceleration of the vehicle so as to be interposed between the steering wheel and an occupant.

Here, the bag is usually covered with a cover and stored inside the cover. This cover is formed with a horizontal thin-walled breaking portion that crosses the central part left and right and a vertical thin-walled judgment part that vertically crosses the vicinity of both left and right ends. When the airbag device is in operation (when the bag is inflated), the cover is a bag. Is applied from the inside by a tensile force to break the lateral thin-walled fractured portion and the vertical thin-walled fractured portion, and the cover is developed on both upper and lower sides with this as a boundary. As a result, the bag is projected to the outside of the cover and is interposed between the steering wheel and the occupant, and the impact of the occupant is absorbed.

By the way, when the vehicle suddenly decelerates, the cover breaks and expands as described above. The expanding position of the cover determines the inflating and projecting performance of the bag, and the expanding cover unnecessarily interferes with the body of the occupant. Is not desirable,
Therefore, it is necessary to properly set the deploying position of the cover, that is, the forming position of the lateral thin-wall breaking portion and the vertical thin-wall breaking portion. For this reason, the horizontal thin-wall breaking portion and the vertical thin-wall breaking portion are formed at optimal positions based on data such as the bag capacity and the inflator pressure.

However, even if the lateral thin wall rupture portion and the vertical thin wall rupture portion are formed at the optimum positions of the cover based on the respective data as described above, the rupture does not stop at these thin wall rupture portions, and the expansion protrusion of the bag is not generated. There was a possibility that the rupture would unnecessarily expand beyond the end portion of the thin-walled fracture portion due to the momentum. Therefore, conventionally, it has been unavoidable to empirically grasp the occurrence of such unnecessary cracks and set the formation position of the thin-wall fracture portion, which is an obstacle in determining the optimum formation position of the thin-wall fracture portion. It was

[0006]

SUMMARY OF THE INVENTION In consideration of the above facts, the present invention ensures that the bag has an inflating and projecting performance by breaking and expanding only at a set thin wall breaking portion without causing unnecessary tears. The purpose is to obtain a cover for an airbag capable of

[0007]

An air bag cover according to the present invention is used in an air bag device provided on a steering wheel, and is provided along a thin-walled break portion which is set in advance by being pressurized by an inflating bag. In the airbag cover that ruptures and expands, an arcuate stop circle having a diameter larger than the width dimension of other portions in a plan view is provided at the end of the thin rupture portion.

[0008]

In the air bag cover having the above-mentioned structure, when the bag is inflated, the bag is pressurized from the inside to break the thin-walled breaking portion, and the airbag is deployed at this boundary. This allows
The bag is projected to the outside of the cover and interposed between the steering wheel and the occupant to absorb the impact of the occupant.

Here, since the arcuate stop circle is provided at the end of the thin-wall break portion, even if the momentum (stress) of the inflation protrusion of the bag acts on the end of the thin-wall break portion,
This stress is dispersed and relaxed at the stop circle. For this reason,
It is possible to prevent the crack from unnecessarily expanding beyond the end portion of the thin-wall breaking portion, and the cover is broken and deployed only at the thin-wall breaking portion.

This makes it possible to reliably and uniquely determine the optimum position for forming the thin-walled fractured portion, and to ensure the inflation and projection performance of the bag.

[0011]

1 is a plan view of an airbag cover 40 according to an embodiment of the present invention, and FIG. 2 is an airbag for a vehicle driver seat to which the cover 40 is applied. A schematic overall configuration of the device 10 is shown.

The airbag device 10 has a base plate 12 and is attached to a hub 16 of a steering wheel 14. An inflator 18 is attached to the base plate 12. In the inflator 18, a starting device 20 is arranged and a gas generating agent 22 is contained. The starting device 20 senses this when the vehicle rapidly decelerates, and the gas generating agent 22 burns. Further, a gas hole 24 is formed on the occupant side peripheral surface of the inflator 18, and the gas generated by the combustion of the gas generating agent 22 is ejected to a bag 26 described later.

On the passenger side of the inflator 18, the bag 2
6 is folded and accommodated. A mounting hole 28 corresponding to the inflator 18 is formed in the bag 26. The peripheral edge of the mounting hole 28 is clamped by a ring plate 30 with the inflator 18 inserted in the mounting hole 28, and the bag 26 is inflated. The structure is fixed to 18. A strap (not shown) is sewn inside the bag 26 to maintain its shape when inflated. Further, a pair of vent holes (not shown) are formed in the vicinity of the upper end of the bag 26, and the gas from the inflator 18 can be discharged to the outside.

A cover 40 is arranged outside the bag 26. The cover 40 is made of synthetic resin, more specifically urethane, and is arranged on the occupant side of the base plate 12 (upper side in FIG. 2) to store the bag 26 between the cover 40 and the base plate 12.

On the back surface side of the cover 40, a horizontal thin-wall breaking portion 42 is formed which laterally crosses the vicinity of the central portion, and at both left and right ends of the horizontal thin-wall breaking portion 42, the cover 40 is vertically crossed vertically. The thin break portions 44 and 46 are continuously formed. The vertical thin-wall breaking portions 44, 46 extend substantially at right angles to the extending direction of the horizontal thin-wall breaking portion 42, and the horizontal thin-wall breaking portion 42 constitutes a substantially H-shaped thin wall portion.

The thickness of the cover 40 is, for example, 6 to 6.
It is formed to 7 mm. Further, the thickness dimension of the horizontal thin-wall break portion 42 and the vertical thin-wall break portions 44, 46 is, for example, 0.9 to 1.
The width dimension is, for example, 2 m.
It is formed in m.

The horizontal thin-wall breaking portion 42 and the vertical thin-wall breaking portions 44 and 46 are adapted to break and expand the cover 40 in a double-door shape when the bag is inflated. That is, the cover 40 is provided with an upper expanding portion 48 that expands upward and a lower expanding portion 50 that expands downward with the horizontal thin wall breaking portion 42 and the vertical thin wall breaking portions 44 and 46 as boundaries. When the bag 26 is inflated, the cover 40 is pressed from the inside by the bag 26, and the cover 40 is once inflated to the outside by this pressure, and by this deformation, the lateral thin wall break portion 42 and the vertical thin wall break portions 44, 46 are broken. As a boundary, the cover 40 is configured so as to be broken and expanded into an upper expansion part 48 and a lower expansion part 50.

Here, as shown in detail in FIG. 3 (A), the ends of the vertical thin wall break portions 44, 46 have a larger diameter (for example, 5 to 7) than the width dimension of other portions in a plan view.
mm) and an arcuate stop circle 52 is provided.

Next, the operation of this embodiment will be described. In the airbag device 10 having the above configuration, the inflator 18 is actuated by the starting device 20 (not shown) when the vehicle is suddenly decelerated, and gas is sent into the bag 26 to inflate the bag 26. Due to this expansion, the cover 40 is pressed from the inside by the bag 26 and swells outward, and this deformation ruptures the lateral thin wall rupture portion 42 and the vertical thin wall rupture portions 44, 46. At the same time as being unfolded, the lower unfolding section 50 is unfolded downward. This allows the bag 26
Is projected to the outside of the cover 40 and is interposed between the steering wheel 14 and the occupant to absorb the impact of the occupant.

Here, since the arcuate stop circles 52 having a diameter larger than the widths of other portions are provided at the ends of the vertical thin-walled break portions 44 and 46, it is assumed that the bag 26 is inflated and protruded. Even if the momentum (stress) acts on the end of each of the vertical thin-wall breakage portions 44, 46, this stress is generated by the stop circle portion 52.
The dispersion is relaxed by. Therefore, as shown in FIG.
Unnecessary expansion of the rift beyond the end portions of the vertical thin-wall breaking portions 44, 46 is prevented, and the cover 40 is broken and developed only at the horizontal thin-wall breaking portion 42 and the vertical thin-wall breaking portions 44, 46.

As a result, the optimum formation positions of the horizontal thin-wall breaking portion 42 and the vertical thin-wall breaking portions 44, 46 (in other words, the vertical spreading widths of the upper developing portion 48 and the lower developing portion 50) are reliably and uniquely determined. Therefore, it is possible to reliably ensure the inflation and projection performance of the bag 26.

In the above embodiment, the stop circles 52 provided at the ends of the vertical thin wall breaks 44 and 46 are formed in an arc shape with a diameter larger than the width dimension of other parts in plan view. However, the thickness of the stop circle 52 may be different from the thickness of other portions, or may be a through hole. Even in this case, the stress concentration acting on the terminal ends of the vertical thin-walled fractured portions 44 and 46 is dispersed and relaxed, and the vertical thin-walled fractured portions 44 and 46 are reduced.
Unnecessary expansion of the rift beyond the end of the is prevented.

[0023]

As described above, the airbag cover according to the present invention does not cause unnecessary tears and breaks and develops only at the set thin-wall breaking portion, so that the inflation and projection performance of the bag is ensured. It has an excellent effect that can be.

[Brief description of drawings]

FIG. 1 is a plan view of an airbag cover according to an exemplary embodiment of the present invention viewed from an occupant side.

FIG. 2 is a sectional view showing an overall structure of an airbag device to which an airbag cover according to an embodiment of the present invention is applied.

FIG. 3 is a plan view showing a stop circle portion provided on a vertical thin-wall breaking portion of the cover, FIG.
(B) is a plan view in a fractured state.

[Explanation of symbols]

 10 Airbag device 14 Steering wheel 26 Bag 40 Cover 42 Horizontal thin-wall breaking part 44 Vertical thin-wall breaking part 46 Vertical thin-wall breaking part 48 Upper deployment part 50 Lower deployment part 52 Stop circle part

Claims (1)

[Claims] 1. An airbag cover used in an airbag device provided on a steering wheel, which is ruptured along a preset thin-wall breaking portion by being pressurized by an inflating bag and deployed. An airbag cover characterized in that an arcuate stop circle portion having a diameter larger than the width dimension of other portions in a plan view is provided at the end of the breakage portion.