JP2000264159A - Manufacture of air bag cover - Google Patents

Abstract

PROBLEM TO BE SOLVED: To eliminate a defect of a surface part because of a thin wall part by providing a first weak part as a thin wall part inside of a covering part at the time of molding, and then further providing a second weak part by pressing an insert piece in the thin wall part. SOLUTION: A covering part 12 of an air bag cover is flat on the whole as its appearance with crimp 12a only, and the back thereof is provided with a tear line 30 which is a recessed groove substantially H-shaped in plane. The tear line 30 is formed by a stepped part 31 as a first weak part having a thickness t1 and a cutout 32 as a second weak part cut not to pierce to the surface side with the thickness of the surface side t2 left behind. A cutter is pressed toward the center of the thin wall stepped part 31. The cutter is plural triangular blades arranged in a line on the base. The cutter is held on a holder of an elevator and pressed to the stepped part 31, thereby forming plural cutouts forming a column like a broken line.

Description

DETAILED DESCRIPTION OF THE INVENTION

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to a method for manufacturing an airbag cover in which a defect in a surface portion due to a thin portion is eliminated.

[0002]

2. Description of the Related Art An airbag is inflated by a large amount of inert gas generated by an inflator operated by a starting device which detects a collision or the like, so that an occupant and a part in a vehicle compartment, such as an instrument panel and a steering wheel, are inflated. This prevents or reduces injuries to the occupant due to a so-called secondary collision in which the occupant hits the interior of the vehicle during a collision.

[0003] Before activation, the airbag is folded and covered with a cover made of resin, and is attached to the above-mentioned room. The cover covering such an airbag serves as a part of the interior of a vehicle. Harmoniously arranged around. That is, for example, injection molding is performed using a resin material having a color tone and gloss close to the skin of the instrument panel and a mold for transferring grain such as leather.

[0004] The covering portion of the airbag cover, in which the opening for inflating the airbag is formed, has a predetermined thickness. For example, a substantially H-shaped or C-shaped groove is provided in the covering portion, and the airbag is cut from the groove. Opening is made, but the airbag cover groove is provided on the front side of the airbag cover groove to make a deep groove so that it becomes sharply thin compared to the entire thickness of the coating so that the opening cuts off at the groove. Has a problem that the gloss of the color is different from that of the peripheral portion. That is, when the airbag cover is injection-molded, the flow cross section of the resin rapidly decreases at the thin portion at the bottom of the deep groove, the flow velocity increases, shear heat is generated, and the resin pressure is not applied. Therefore, minute recesses called so-called sink marks are formed on the surface due to the difference in resin shrinkage after molding.

[0005] In a normal airbag cover, the normal thickness of the covering portion is about 4 mm, while the depth of the deep groove portion is set to be less than 0.8 mm, and the width of the deep groove portion is also several times. mm. For this reason, even if the mold surface is evenly embossed to visually conceal minute defects on the surface, there is a difference in gloss on the product surface. Therefore, the appearance is improved by painting the airbag cover, but this method increases the manufacturing cost.

As another method for improving the appearance, a special elastomer resin which does not easily cause a difference in gloss between the thin portion and the peripheral portion under the above conditions is used under specific molding conditions.
There is also a method to address the above problem without painting. However, applying such a very special material and a molding machine capable of processing the material to have a suitable appearance and securing extremely limited processing conditions leads to an increase in product cost.

In the method of introducing a reaction liquid for polyurethane molding into a mold by injection reaction molding, the cross section of the flow path is suddenly changed by a ridge of the mold for forming a groove.
Voids may be formed along the groove due to entrapment or retention of bubbles. As a result, the yield is reduced, and the production cost is also increased. In particular, it is difficult for such a polyurethane resin alone to satisfy the performance as an airbag cover, and insert molding of a reinforcing member such as a nylon net is performed. And it is necessary to reinforce the nylon net to the vicinity of the deep groove part, but the flow of the reaction liquid is apt to be disturbed near the deep groove part, so the nylon net is affected and it is difficult to localize it in the molding die. In addition, bubbles are easily formed by entraining bubbles due to turbulence of the reaction solution.

As described above, there is a method of forming a conventional airbag cover so as to obtain a final shape of a broken portion at the time of molding, but there is also a method of processing the formed portion after forming the broken portion. For example, Japanese Unexamined Patent Publication No. 6-218811 discloses a technique in which a pressing member that applies ultrasonic waves to the skin is melted to form a groove.

[0009]

However, the above-mentioned method using ultrasonic waves involves melting of the resin, so that the influence on the gloss of the surface is inevitable. Has limitations. In addition, since the molten resin rises along the groove, the case may be raised by being pushed by the folded bag. Further, the injection-reaction polyurethane resin is not suitable for thermal processing because it does not generate fluidity when heated.

The present invention solves the above-mentioned problems of the prior art. That is, the object of the present invention is:
An object of the present invention is to eliminate a defect in appearance due to a thin portion (tear line) of an airbag cover body by a simple method without requiring painting and without using a special resin material.

[0011]

As a result of intensive studies, the present inventor has found that a weak portion for tearing is provided in two stages in a covering portion which is an occupant-side surface portion of an airbag cover body, and the first weak portion is provided. It has been found that it is effective to provide a thin portion inside the covering portion at the time of molding, and then to provide a second weak portion by pressing the insertion piece in the thin portion.

That is, the present invention provides (1) a method of manufacturing an airbag cover for covering a folded airbag,
In the airbag cover, a first weak portion is formed inside the covering portion that is broken by the inflation of the airbag to a size smaller than the thickness of the entire covering portion, and an insertion piece is inserted into the first weak portion. A method of manufacturing an airbag cover, wherein the second weak portion is formed by pressing and piercing in the thickness direction, and (2) the thickness dimension of the first weak portion is one of the thickness of the entire covering portion. (3) the method for manufacturing an airbag cover according to (1), wherein the insert is a cutter blade; and (4) the method for manufacturing an airbag cover according to (1) or (2). Is a pin, and the second weak portion is a row of pinholes. The method of manufacturing an airbag cover according to the above (1) or (2), (5) the second weak portion penetrates the front and back of the covering portion. The manufacturing method of the airbag cover according to the above (3) or (4), (6) a method of manufacturing an air bag cover of the (3) to (5), wherein the grain depth of 50 to 180μ m applied to the surface of the covering portion relates.

In the present invention, the first weak portion is made thinner with respect to a preferable thickness of the entire covering portion.
It has a sufficient thickness to prevent sink marks and uneven gloss, and does not involve heat processing. Therefore, it does not affect the surface appearance. Therefore, even if there is a thin portion, there is no need to form a decorative film for improving the appearance such as painting,
Manufacturing costs are reduced. Since the first weak portion has a thickness smaller than the thickness of the entire covering portion, the insertion stroke of the insertion piece may be small, the insertion pressing force and the pull-out resistance are small, the workability is good, and the deformation of the airbag cover is small. .

In the present invention, the first weak portion is prevented from obstructing the molding, that is, the sudden change in the flow cross section of the resin is prevented, and the gloss unevenness (local gloss) due to the change in shrinkage is prevented. Preferably, the thickness of the first weak portion is the thickness of the covering portion as a whole so as to reduce the turbulence of the molding material and to obtain an airbag cover having good physical properties and appearance without causing a gloss change). 1/3 or more. Further, the thickness of the first weak portion is preferably not more than 2/3 of the thickness of the entire covering portion so that the first and second weak portions can be reliably and smoothly broken when the airbag inflates. preferable.

In the present invention, in order to form a second weak portion, an insertion piece is pressed and inserted into the first weak portion to form a second weak portion. When the insertion piece is a cutter blade, the second weak portion has an intermittent slit shape, and when the insertion piece is a pin, it has a pinhole row. Due to the formation of these second weak portions, the covering portion of the airbag cover body is reliably broken when the airbag is deployed, and the air between the slits adjacent to the second weak portion and the intermediate portion between the pinholes. The shape of the portion to be broken when the bag is deployed is stabilized.

Further, at least a part of these slits and pinholes may be penetrating. By forming the second weak portion into a penetrating shape, even if the molding material of the airbag cover is particularly large in elastic deformation due to compression, it is possible to easily form the expected break line. Even if the second weak portion is penetrating, if the tip of the insertion piece forming the second weak portion is sharp, the penetrating mark that appears on the surface side of the covering portion of the airbag cover is minute, and the influence on the appearance is small. It can be said that there is practically no.

Further, the surface of the covering portion may be textured. The depth of this grain is more than 50μm and 180μ
It should be less than meters. When it is smaller than 50 μm, the visual effect of the grain is not substantially obtained on the surface. On the other hand, when the thickness exceeds 180 μm, a rough appearance is given. And even if the tip of the insertion piece reaches or penetrates the surface of the covering portion, the proximity mark or penetration mark of the tip of the insertion piece and the unevenness of the grain are in harmony, so that the influence on the appearance is extremely reduced. Can be.

[0018]

DETAILED DESCRIPTION OF THE PREFERRED EMBODIMENTS An airbag cover according to one embodiment of the present invention will be described below with reference to the drawings.

FIG. 1 is a perspective view of the airbag cover 11 alone, and FIG. 2 is a cross-sectional view showing a state in which the airbag cover 11 in the cross section AA of FIG.

The airbag module 10 includes an airbag cover 11, a retainer 21, an airbag 22, an inflator 23, and the like. The nut 4 is fixed to the mounting plate 3 of the reinforcement 2 of the panel 1. A hook 21 a is provided at a peripheral portion on the opening side of the retainer 21, and the airbag cover 11 is provided with a rectangular through hole 17 in the vertical wall 13.
The hook 21a is attached so as to be hooked. The hook 21a is loosely engaged with the through hole 17,
It is located so as to close the opening 5 of the instrument panel 1, and can absorb minute individual differences (variations) in the distance between the reinforcement 2 and the outer surface of the instrument panel 1. That is, the claw 16 is engaged with the edge of the opening 5, and the airbag cover 11 is positioned without rising or falling from the outer surface of the instrument panel.

The airbag cover 11 includes an airbag 22.
There is a covering portion 12 which is cleaved by the pressure caused by the expansion to form two doors 18 and 19, and the upper surface side is provided with fine irregularities 12a which are fine irregularities showing only a part thereof in FIG. I have. 12b is recessed by a small step,
The embossed portion 12a is a recessed portion in which fine irregularities and characters of a different pattern are engraved. Except for the recessed portion 12b, the covering portion 12 of the airbag cover 11 has an external appearance in which only the embossment 12a is entirely flat and has a rear surface provided with a tear line 30 which is a substantially H-shaped concave groove on the back surface.

The details of the tear line 30 are shown in FIG. The covering portion 12 has a substantially constant thickness t ₀ except for the tear line 30, the thickness t ₀ is 4.3 mm, and the surface side grain 12 a has a depth (difference between a peak and a valley) of 110 μm. It is fine irregularities of a meter. The tear line 30 has a step portion 31 as a first weak portion having a thickness t _1, and a cut portion as a second weak portion cut out from the step portion 31 so as not to penetrate the surface side except for the thickness of the front surface side t _2. Recess 32 is formed. t ₁
And t ₂ dimensions are 2.0 millimeters, 0.
5 mm.

A method for forming the tear line 30 will be described with reference to FIG.

The airbag cover 11 is formed by injection molding of an olefin elastomer resin. The step 31 is provided integrally, but the cut 32 is not provided yet. At this time, t ₀ and t ₁ have the above-mentioned dimensions, and it is possible to prevent a sharp rise in the flow resistance and the accompanying shear heat generation. In addition, since the resin pressure is sufficiently applied and there is no sudden change in thickness, so-called sink marks due to a gloss change or a difference in shrinkage do not occur on the surface side facing the step portion 31. A good appearance can be obtained without the need for surface treatment such as painting.

Next, as shown in FIG. 4, the airbag cover 11 taken out of the molding die is placed on a support die 51 and pressed by clamps 52 and 53.

The clamp 53 presses the airbag cover 11 so as not to cover the tear line 30, and
Press the cutter 54 toward the center of FIG.
I). The cutter 54 is a plurality of triangular blades arranged in a row on a base 55 as shown in FIG. 6. The triangular blades are held in a holder 56 of the elevator and pressed against the stepped portion 31 to form a plurality of rows arranged in a broken line. The cut 32 is formed (FIG. 5II).

Preferably, ultrasonic vibration having a small amplitude is applied to the cutter so that a triangular blade is easily inserted. This ultrasonic vibration is auxiliary and does not cause melting of the resin.

The cutter has a row of triangular blades and the cut 32 is formed in the central transverse portion 30a in FIG. 1. The side portion 30b forming the H-shape of the tear line 30, the reversing portion 30c, Similar processing can be applied to 30d.

In order to deploy the airbag 22, it is preferable that the depth of the center cross section 30a is the deepest, and then the side cross section 30b becomes shallower toward the terminal.

FIG. 7 shows another form of a cutter in which rectangular blades 64 are arranged at predetermined intervals. The rectangular blades 64 were 3 mm wide, and the distance between the adjacent rectangular blades 64 was 3 to 5 mm. The tear line 30 has a width of the cut 32 of 3 to 5 mm and a distance between the cuts, that is, a width of the uncut step 31 connecting the cuts is 3 to 5 mm.
Break-shaped cuts 32 at equal intervals of millimeters are formed. The rectangular blade 64 has a width of 3 mm,
The interval between the adjacent rectangular blades 64, 6 is set to 6 mm, a single cut 32 is formed at an interval of 6 mm as shown in FIG. 8, and the base 55 is moved to the right by 4.5 as shown in FIG.
The space may be moved by millimeters and the second pressing may be performed to make the space between the adjacent cuts 32, 1.5 1.5 mm. Further, the descending stroke of the rectangular blade 64 may be made different between the first time and the second time, and t ₂ can be set so as to be alternately large and small. Therefore, it is easy to process,
In addition, the tear line 3 that can be cut smoothly by deploying the airbag 22
0 can be more suitably formed.

The cutter may be a triangular blade, a rectangular blade, a cutout type, or a fine waveform may be provided at the tip, and may be either a single blade or a double blade.

FIG. 9 shows still another embodiment. A plurality of pins 66 were arranged in place of the triangular blade of the embodiment. The pin is 1.5 mm in diameter, the tip is sharp,
The pitch is 3 to 5 mm.

In the tear line 30, the tear strength of the step portion 31 is reduced due to the pin hole 32 formed as a cut by pushing the pin, and the air bag can be formed without forming the step portion 31 in advance in the same manner as the above-mentioned rectangular blade. The inflation of 22 allows for smooth tearing. It should be noted that it is easier to insert a small amplitude ultrasonic vibration into the pin 66 in the same manner, but since the pin diameter is small and the insertion depth is shallow, sufficient processing is possible without ultrasonic vibration. It is. Further, the pin 66 may penetrate the step portion 31 to reach the front surface side. Since the tip of the pin 66 is fine enough to match the pattern of the grain 12a, there is almost no effect on the appearance. The pins 66 may be prepared so as to be arranged at a narrow pitch so that they can be pressed once, or the pins 66 may be formed at a fine pitch by pressing a plurality of times at a predetermined feed pitch. At this time, the descending stroke may be varied in the same manner as described above, and one of the strokes may be increased to slightly penetrate the surface. A similar effect is achieved by making any one of the pins 66 adjacent to each other longer than the others.

Although the above description has been made based on the injection-molded cover for the passenger-seat airbag, the present invention is not limited to the above and is applicable to various types of airbag devices. Of course. Further, the resin can be applied not only to a thermoplastic elastomer resin but also to a polyurethane resin molded by injection reaction.

[0035]

According to the present invention, as described above, the weak portion is formed in two stages, so that the thickness of the thin portion, which is the first weak portion, is reduced on the surface side during molding so that there is no external obstacle. It is possible to have a sufficient thickness to prevent occurrence of the generation, and thereby, the molding processing conditions are expanded, and the yield can be improved. Since there is no appearance defect on the surface side, concealment treatment of the coating film or the like is not required, and steps requiring energy such as drying of the coating film can be reduced.

Further, since the formation of the weak portion does not involve heat generation or heating, it is possible to provide an airbag cover which can maintain an excellent appearance of the molded product and can be smoothly torn.

[Brief description of the drawings]

FIG. 1 is a perspective view of an airbag cover of the present invention.

FIG. 2 is an explanatory cross-sectional view of FIG. 1A-A.

FIG. 3 is an explanatory sectional view of a tear line according to the present invention.

FIG. 4 is an explanatory view of forming a second weak portion according to the present invention.

FIG. 5 is an explanatory view of forming a second weak portion according to the present invention.

FIG. 6 is an explanatory view of a second weak portion forming cutter used in the present invention.

FIG. 7 is another example of the second weak portion forming cutter used in the present invention.

FIG. 8 is an explanatory view of forming a second weak portion by the cutter of FIG. 7;

FIG. 9 is an explanatory view of still another cutter.

Claims (6)

[Claims] 1. A method of manufacturing an airbag cover that covers a folded airbag, wherein a first weak portion is thinner than a thickness of the entire covering portion inside the covering portion that is broken by inflation of the airbag. Forming a second weak portion by pressing the insertion piece against the first weak portion and piercing in the thickness direction. 2. The method for manufacturing an airbag cover according to claim 1, wherein the thickness dimension of the first weak portion is at least １ ／ of the thickness of the entire covering portion. 3. The method for manufacturing an airbag cover according to claim 1, wherein the insertion piece is a cutter blade. 4. The method for manufacturing an airbag cover according to claim 1, wherein the insertion piece is a pin, and the second weak portion is a row of pinholes. 5. The method for manufacturing an airbag cover according to claim 3, wherein the second weak portion penetrates the front and back of the covering portion. 6. The method for manufacturing an airbag cover according to claim 3, wherein a grain having a depth of 50 to 180 μm is formed on a surface of the covering portion.