JPH0958389A - Cover for air bag - Google Patents

Abstract

PROBLEM TO BE SOLVED: To provide an inexpensive cover for air bag which does not cause an unnecessary crack, is broken in the proper order only in the set thin-walled rupture section and develops, and can ensure inflation projection performance of an air bag securely. SOLUTION: A horizontal thin-walled ruptured section 42 of which wall is thinner than that of a cover 40 is arranged like line groove which crosses a central part horizontally. and longitudinal thin-walled ruptured sections 44, 46 of which wall is thinner than that of the cover 40 are arranged like line groove which is extended longitudinally at both free ends of the horizontal thin-walled ruptured section 42 in such a manner that its intermediate section is connected on a rear side of the cover 40. The thickness T of a bottom face section of the line groove is gradually increased along a line toward its end from the center side of the cover 40. Furthermore, an opening angle θ which forms a right-angled face on a bottom face of a side face of line groove along the line is gradually increased, or the width H of the bottom face of line groove is narrowed along the line so that a crack due to the inflation of the cover 40 along the line is promoted.

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 An air bag device attached to a steering wheel or the like of an automobile is constructed such that the air bag is inflated when the vehicle is rapidly decelerated, and the air bag is interposed between the steering wheel and an occupant.

In such an airbag device, 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 horizontally crosses the vicinity of the central portion and a vertical thin-walled breaking portion that vertically crosses the vicinity of both left and right ends, and when the airbag device is operating (when the bag is inflated), the cover is The bag is pressed from the inside by a tensile force to act, the lateral thin-wall breaking portion and the vertical thin-wall breaking portion are broken, and at this boundary, the cover is bent and expanded to open both sides to open the opening. Then, the bag pops out of the cover from the opening of the cover, is inflated and deployed, and is interposed between the steering wheel and the occupant,
The shock of the passenger is absorbed.

By the way, when the vehicle suddenly decelerates, the cover breaks and deploys as described above. The inflating and projecting performance of the bag is determined by the deploying position of the cover, and the deploying cover has data such as bag capacity and inflator pressure. It is formed in the optimum position based on.

However, as described above, even if the lateral thin-walled fractured portion and the vertical thin-walled fractured portion are formed at the optimum positions of the cover based on the respective data, when the cover is actually deployed, crack initiation points may occur at a plurality of locations. In addition, cracks may occur in parts other than the thin-walled break part. Therefore, in consideration of the fact that torsional stress is not concentrated at the thin-walled breakage part as planned and the torsional stress concentrates on the developed part of the cover, the rigidity of the parts other than the thin-walled breakage part of the cover body must be strengthened, and the size and weight increase And it was expensive.

[0006]

SUMMARY OF THE INVENTION In consideration of the above facts, the present invention is a low-priced airbag capable of ensuring the inflation and projection performance of the bag by breaking and deploying at a set thin-wall breaking portion as planned. The purpose is to obtain a cover for.

[0007]

A cover for an air bag according to claim 1 of the present invention is used in an air bag device, and is applied to an inflating bag along a thin broken portion formed in a line groove shape. In the airbag cover that ruptures and expands, since the line groove bottom surface portion having the gradually increased wall thickness is provided along the path extending from the cover center side position to the end portion in the thin wall fracture portion, the airbag device is When actuated and the bag pressurizes the cover, a crack occurs at the central part of the thin-walled rupture part in the cover where the structure is weakest, and the crack progresses along a predetermined muscle path starting from this and ruptures and expands the bag appropriately. Can be expanded and projected.

An air bag cover according to a second aspect of the present invention is used in an air bag device and is ruptured along a thin rupture portion formed in a linear groove by being pressed by an inflating bag and deployed. In the bag cover, a line groove bottom surface portion having a gradually narrowing lateral width is provided along a path extending from the cover central side position to the end portion in the thin wall break portion, so that the airbag device operates and the bag covers. When a pressure is applied to the cover, a crack will occur in the central part of the thin-walled rupture part in the cover structure, and the crack will proceed along a predetermined muscle path starting from this, and the rupture and expansion will cause the bag to properly inflate and project. You can definitely.

The airbag cover according to claim 3 of the present invention is used in an airbag device and is broken and deployed along a thin broken portion formed in a linear groove by being pressed by an inflating bag. In the airbag cover, along the path extending from the cover center side position to the end in the thin wall break portion, the bottom portion of the line groove with the thickness gradually increased, and the thin wall break portion from the cover center side position to the end portion. Since the bottom of the line groove is provided along the path toward the bottom, the width of the groove gradually narrows. A crack is generated in the bag, and the crack progresses along a predetermined muscle path with this as a starting point, and the action of causing the bag to expand by breaking and to properly inflate and project can be more reliably achieved.

According to a fourth aspect of the present invention, in the airbag cover according to the first, second or third aspect, the bottom surface of the line groove is provided along a path extending from the cover central side position to the end portion of the thin wall break portion. Since the side surface of the line groove is formed to gradually widen the opening angle that is a right angle surface, when the airbag device operates and the bag presses the cover, the cover is the structure where stress is most likely to concentrate on the thin wall. A crack occurs in the central part of the fracture part, and the crack progresses along a predetermined muscle path from this,
The bag can be ruptured and expanded to properly inflate and project.

[0011]

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

As shown in the figure, 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 in 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 the bag 26.

Therefore, the bag 26 has the inflator 18
It is folded and stored on the passenger side. 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. It is fixed at 18. A strap (not shown) is sewn inside the bag 26 so as to swell into a predetermined 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 breakage portions 44 and 46 extend substantially at right angles to the extending direction of the horizontal thin-wall breakage portion 42 to form a horizontal thin-film breakage portion 42 and a generally H-shaped thin wall portion.

The lateral thin-walled breaking portion 42 is formed by providing a groove having a linear groove shape at a predetermined portion of the cover 40 and having a trapezoidal cross section having linear groove side surfaces rising obliquely from both sides of the bottom surface. ing. Further, at the central position in the lengthwise direction of the lateral thin wall break portion 42, the wall thickness T1 is relatively thin, the lateral width H1 is wide, and the opening angle θ1 between the bottom surface of the groove side surface and the surface forming a right angle is an acute angle. Along with this, the horizontal thin-wall breaking portion
As illustrated in FIG. 4, the wall thickness T2 is gradually made thicker, the lateral width H2 is gradually narrowed, and the opening angle θ2 is gradually widened as approaching from the center to both ends.

By forming in this manner, the lateral thin-walled breaking portion 42 has a weaker strength than the other portions because the central portion thereof is thin and wide. Moreover, since the opening angle θ1 is acute, the slope between the thin portion and the thick portion is short, and the rigidity changes remarkably at these boundaries, so stress is concentrated due to the so-called notch effect. Therefore, the stress concentrates on the weak places, and the fracture easily occurs, and the structure satisfies the condition as the crack starting point.

Each of the vertical thin-walled fractured portions 44 and 46 formed in the same line groove shape as the horizontal thin-walled fractured portion 42 and intersecting with each other at the T-shaped crossing portion and connecting to each other is shown in FIG. As shown in FIG. 6, the wall thicknesses T3 and T4 of the bottom surface of the groove are set to be thicker than the wall thickness T2 described above, the lateral widths H3 and H4 of the bottom surface are set to be narrower than the lateral width H2 described above, and the opening angles θ3 and θ4 of the side surfaces are set. The angle is wider than the opening angle θ2 described above.

Further, as shown in FIG. 7 and FIG. 8, the vertical thin-wall breaking portions 44, 46 respectively have the wall thicknesses T5, T6 which are the same as the above-mentioned wall thickness T as shown in FIG. 7 and FIG.
3 and T4, and the widths H3 and H4 are the above-mentioned width H
3 and H4, and the opening angles θ3 and θ4 are wider than the opening angle θ2. That is, T1 ≦ T2 <T
3 or T4 <T5 or T6, and H1 ≧ H2
> H3 or H4> H5 or H6, and θ1 ≦
The configuration is such that θ2 <(θ3 or θ4) <(θ5 or θ6).

The thickness of the cover 40 is 6 to 6, for example.
It is formed to 7 mm. In addition, the thickness of each of the horizontal thin-wall break portion 42 and the vertical thin-wall break portions 44, 46 is, for example, T1 = 0.5 mm, T2 = 1.0 mm, T3 = 1.2 mm, T4 = 1.2 mm, T5 = 1.5 mm. , T6 = 1.5 mm H1 = 1.8 mm, H2 = 1.5 mm H3 = 1.2 mm, H4 = 1.2 mm H5 = 0.8 mm, H6 = 0.8 mm θ1 = 10 degrees, θ2 = 30 degrees θ3 = 50 degrees, θ4 = 50 degrees, θ5 = 70 degrees, and θ6 = 70 degrees.

The lateral thin-walled breaking portion 42 and the vertical thin-walled breaking portions 44, 46 are designed so that the cover 40 is fractured and expanded in an open double-sided manner when the bag is inflated and opened. 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 bag 26
The cover 40 is pressurized from the inside by this pressure, and the cover 40 once bulges outward due to this pressure.
Also, the vertical thin-wall breaking portions 44 and 46 are broken, and the cover 40 is broken and developed into the upper developing portion 48 and the lower developing portion 50 with this breaking as a boundary.

Further, here, at the respective ends of the vertical thin wall break portions 44 and 46, arcuate stop circle portions 52 having a diameter (for example, 5 to 7 mm) larger than the width dimension of other portions in plan view are provided. Has been.

Next, the operation of the present 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 to the outside, and this deformation ruptures the lateral thin wall rupture portion 42 and the vertical thin wall rupture portions 44, 46. The lower expansion section 50 is expanded downward while being expanded upward. As a result, the bag 26 is projected to the outside of the cover 40 and interposed between the steering wheel 14 and the occupant to absorb the kinetic energy of the occupant.

The horizontal thin-wall breaking portion 42 and the vertical thin-wall breaking portion 4
When 4 and 46 are broken, first, the stress due to the expansion protrusion of the bag 26 is concentrated on the central position of the lateral thin wall break portion 42, and the weakest place is broken. After that, the rupture portion becomes the crack starting point, and the crack spreads continuously along the set path from the direction with higher stress concentration to the direction with lower stress concentration and from the direction with weaker strength to the higher direction. To do. That is, specifically, this myocardium is cracked from the crack origin at the center of the lateral thin-wall fracture portion 42 in the lengthwise direction to the both ends of the lateral thin-wall fracture portion 42 in sequence, and from each T-shaped crossing portion on both ends. Subsequently, the cracks change direction to the central portion in the longitudinal direction of each of the vertical thin wall break portions 44, 46, and from this, the process of sequentially breaking to the stop circles 52 at both ends of each of the vertical thin wall break portions 44, 46 is performed. To take.

In this way, the transverse thin inner rupture portion 42 and the vertical thin wall rupture portions 44, 46 crack and progress along a predetermined course and reliably rupture, so that the upper deploying portion 48 and the lower deploying portion 50. The bag can be expanded from the opening by properly expanding without applying an unexpected load such as twisting.

Here, since the arcuate stop circles 52 having a diameter larger than the widths of the other portions are provided at the ends of the vertical thin-wall breaking portions 44, 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. For this reason, the vertical thin-wall breaking portions 44, 46
Unnecessary expansion of the rift beyond the end portion of the cover is prevented, and the cover 40 has a lateral thin wall break 42 and a vertical thin wall break 4
Only 4 and 46 are broken and deployed.

Of course, the airbag cover of the present invention can be used in an airbag device for a passenger seat or the like.

[0028]

EFFECT OF THE INVENTION The airbag cover according to the present invention can be ruptured and expanded in a predetermined order at the set thin-walled rupture portion to surely secure the inflation and projection performance of the bag, and the structure Since it is simple and can be configured without adding any other member, it has an excellent effect that an inexpensive product can be provided.

[Brief description of drawings]

FIG. 1 is a front view showing a state in which an airbag cover according to an embodiment of the present invention is viewed from an occupant side.

FIG. 2 is a cross-sectional view showing the 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 cross-sectional view of an essential part showing a cross section taken along line III-III of FIG. 1.

FIG. 4 is a cross-sectional view of an essential part showing a cross section taken along line IV-IV of FIG. 1.

5 is a cross-sectional view of an essential part showing a cross section taken along line VV of FIG.

FIG. 6 is a cross-sectional view of an essential part showing a cross section taken along the line VI-VI of FIG. 1.

7 is a cross-sectional view of a main part showing a cross section taken along the line VII-VII of FIG. 1.

8 is a cross-sectional view of a main part showing a cross section taken along the line VIII-VIII of FIG.

[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 (4)

[Claims] 1. An airbag cover for use in an airbag device, wherein a thin wall breaking portion formed into a linear groove by being pressed by an inflating bag is broken and deployed. An airbag cover having a line groove bottom surface portion having a gradually increasing wall thickness along a path extending from a position to an end portion. 2. An airbag cover for use in an airbag device, wherein a thin wall breaking portion formed in a linear groove by being pressed by an inflating bag is broken and deployed, wherein the cover central side at the thin wall breaking portion. An airbag cover having a line groove bottom surface portion whose width is gradually narrowed along a path extending from the position to the end portion. 3. An airbag cover which is used in an airbag device and in which an inflating bag is ruptured and expanded by a thin groove breaking portion formed in a linear groove when pressed, wherein the cover central side at the thin wall breaking portion. Along the path extending from the position to the end, the line groove bottom surface part with the wall thickness gradually increased, and along the path extending from the cover center side position to the end in the thin wall breaking part, the line whose width is gradually narrowed. An air bag cover comprising: a groove bottom surface portion. 4. A line groove side surface portion formed so as to gradually widen an opening angle formed with a surface perpendicular to the bottom surface of the line groove along a path extending from a position on the center side of the cover to the end of the thin-walled breaking portion. The airbag cover according to claim 1, claim 2, or claim 3.