PANEL FOR AIR BAGS AND METHOD OF MANUFACTURING THE SAME

Abstract: A panel for an air bag of a vehicle, formed by integrally molding an air bag body and a cover therefor, each made from a synthetic resin, characterized in that the air bag body is provided at a circumferential edge portion of an opening made therein with a joint with respect to the cover, the joint constituting a laminate in which an outer circumferential edge of the cover is laminated on the edge of the opening of the air bag body at the inner side thereof.

Description: TECHNICAL FIELD The present invention relates to a panel for an airbag of an automobile forming an airbag cover (a cover body) made of a synthetic resin in a main body made of another synthetic resin such as an instrument panel and a door trim, and relates to its producing method. BACKGROUND ART An airbag arranged in front of a front passenger seat of an automobile is stored on a rear side of the main body such as an instrument panel and a door trim. When the airbag is operated, the airbag cover (cover body) mounted to the instrument panel is opened and the airbag is swollen out in front of the instrument panel. As shown in Fig. 40, an airbag cover 92 and an instrument panel main body 91 are formed as separate members and the airbag cover 92 is fixed to the instrument panel main body 91 by an unillustrated fixture. The airbag is swollen out in front of the instrument panel by rupturing a weak portion such as a thin wall portion formed in advance in the airbag cover 92. However, in the panel for the airbag having the structure, each of the instrument panel main body 91 and the airbag cover 92 are made in separate processes. Accordingly, a certain number of producing works are required with respect to each of the instrument panel main body 91 and the airbag cover 92. Further, it is necessary to perform an assembly work for integrating both the members 91 and 92 with each other and arrange a fixture. Accordingly, a problem exists in that entire producing cost of the airbag is increased. This problem is similarly caused when a door trim instead of the instrument panel is set to a main body and the airbag cover is formed therein. JP 07 144597 A shows a similar panel for an airbag formed by molding a cover body and a main body made of synthetic resin, the panel comprising a joint portion joined with the cover body provided around an opening portion formed in the main body, wherein the joint portion constitutes an overlapping portion in which an outer peripheral edge of the cover body is overlapped. The cover and main bodies are molded separately. BRIEF DESCRIPTION OF THE INVENTION It is an object of the invention to provide a panel of an airbag for an automobile easily and produced at a low cost and further to provide its production method. The solution on the object as first mentioned above is achieved by a panel for an airbag according to appended claim 1. According to the invention, the overlapping portion is arranged around the opening portion (an airbag swelling-out portion) of the main body such as the instrument panel, in which an outer peripheral edge of the cover body (airbag cover) is overlapped as being arranged on the inner side of an opening edge of the main body. Therefore, neither fixture for connecting both the members nor connecting work are required. Thus, in accordance with the present invention, the number of producing works and cost can be greatly reduced compared with a conventional product in which the cover body and the main body such as the instrument panel are separately formed. Appended claims 3 to 14 are directed towards advantageous embodiments of the inventive panel. Claims 15, 16 and 17 are directed towards a method for producing an inventive panel to provide a solution on the second part of the object of the invention as mentioned above. The invention will be described in the following by way of examples and referring to the drawings. Brief Description of the Drawings Fig. 1 is a sectional view of a panel for an airbag according to Embodiment 1 (a sectional view taken along a line X1-X1 of Fig. 2). Fig. 2 is a perspective view of the panel for an airbag according to Embodiment 1. Figs. 3A to 3C are arrangement plan views of a mold in a process of molding the panel for an airbag according to Embodiment 1. Fig. 4 is an enlarged view of the periphery of a thin wall portion of Fig. 1. Fig. 5 is an enlarged view of the periphery of a non-thin wall portion of Fig. 1. Fig. 6 is a sectional view of a panel for an airbag according to Embodiment 2 (a sectional view taken along a line X1-X1 of Fig. 2). Figs. 7A to 7C are arrangement plan views of a mold in a process of molding the panel for an airbag according to Embodiment 2. Fig. 8 is an enlarged view of the periphery of a non-thin wall portion according to Embodiment 3. Fig. 9 is a perspective view of panel for an airbag according to Embodiment 4. Fig. 10 is a perspective view of an panel for an airbag according to Embodiment 5. Fig. 11 is a sectional view taken along a line X2-X2 of Fig. 10. Fig. 12 is a perspective view of a panel for an airbag according to Embodiment 6. Fig. 13 is a sectional view taken along a line X3-X3 of Fig. 12. Fig. 14 is a perspective view of a panel for an airbag according to Embodiment 8. Fig. 15 is a perspective view of a panel for an airbag according to Embodiment 9. Fig. 16 is a sectional view taken along a line Y1-Y1 of Fig. 15. Fig. 17 is an enlarged view of the periphery of a thin wall portion of a panel for an airbag according to Embodiment 12. Fig. 18 is an enlarged view of the periphery of a thin wall portion of a panel for an airbag according to Embodiment 13. Fig. 19 is an enlarged view of the periphery of a thin wall portion of a panel for an airbag according to Embodiment 14. Fig. 20 is a perspective view of a panel for an airbag according to Embodiment 15. Fig. 21 is a perspective view of a panel for an airbag according to Embodiment 16. Fig. 22 is a sectional view taken along a line X4-X4 of Fig. 21. Fig. 23 is a sectional view of a mold in molding the panel for an airbag according to Embodiment 16. Fig. 24 is a sectional view of a mold in molding a cover body according to Embodiment 16. Fig. 25 is a perspective view of a panel for an airbag according to Embodiment 17. Fig. 26 is a sectional view taken along a line X6-X6 of Fig. 25. Fig. 27 is a sectional view of a mold in molding the panel for an airbag according to Embodiment 17. Fig. 28 is a sectional view of a mold in molding a cover body according to Embodiment 17. Fig. 29 is a sectional view of a substantial part of the mold in molding the panel for an airbag according to Embodiment 17. Fig. 30 is a sectional view of a substantial part of a mold in molding a panel for an airbag according to Embodiment 18. Fig. 31 is a perspective view of a panel for an airbag according to Embodiment 20. Fig. 32 is a sectional view taken along a line X8-X8 of Fig. 31. Fig. 33 is an exploded perspective view of a joint portion of a rib and a bracket according to Embodiment 20. Fig. 34 is a plan view of the bracket according to Embodiment 20. Fig. 35 is a sectional view taken along a line V-V of Fig. 34. Fig. 36 is an enlarged plan view of a protrusion-forming portion according to Embodiment 20. Fig. 37 is a sectional view taken along a line VII-VII of Fig. 36. Fig. 38 is a partial enlarged plan view of a bracket according to Embodiment 21. Fig. 39 is a partial enlarged plan view of another bracket according to Embodiment 21. Fig. 40 is a perspective view of a panel for an airbag in a conventional art. PREFERRED EMBODIMENTS OF THE INVENTION Embodiment 1 In this embodiment, as shown in Figs. 1 and 2, a panel 1 for an airbag of an automobile is constituted such that an airbag cover (cover body) 20 made of olefin elastomer (TPO) is integrally molded with a main body 10 constructed by an instrument panel made of polypropylene resin (PP) as a hard synthetic resin. A joint portion joined with the cover body 20 is formed around an opening portion 12 formed in the main body 10. This joint portion constitutes an overlapping portion 15 in which an outer peripheral edge 205 of the cover body 20 is arranged on an inner side of an opening edge 105 of the main body 10 and is overlapped with this opening edge 105. Explanations of each of these constructional elements will next be supplemented. As shown in Fig. 1, the panel 1 for an airbag in this example stores an airbag 81 therein and is arranged on a front passenger seat side of an automobile. The panel 1 is constituted of a main body 10 formed by an instrument panel and a cover body (airbag cover) 20. A thin wall portion 23 is formed in the cover body 20 along a groove portion 21 and is ruptured at an operating time of the airbag 81. As shown by a line S1 of Fig. 2, a connecting shape of the thin wall portion 23 is a quadrilateral shape with one side opened. The main body 10 and the cover body 20 are integrally formed as follows by two-color molding using polypropylene resin and olefin elastomer. Both the two kinds of synthetic resins are thermoplastic and have compatibility (a consolute property). First, as shown in Fig. 3A, a core 32 is projected and comes in contact with a projecting portion 351 of an opposite mold 35. The clearance between a first cavity portion 41 and a second cavity portion 45 is interrupted so that no polypropylene resin as a material of a first member forming the main body 10 flows into the second cavity portion 45. Next, the polypropylene resin forming the main body 10 is injected into the first cavity portion 41. Thereafter, as shown in Fig. 3B, the core 32 is retreated in a subsequent second process so that the first cavity portion 41 and the second cavity portion 45 are communicated with each other. Then, the olefin elastomer as a material of a second member forming the cover body 20 is injected into the second cavity portion 45 so that an overlapping portion 15 of both the members 10 and 20 is formed in a communicating portion of both the cavity portions 41 and 45. Both the members 10 and 20 are integrally made by adhering these members to each other by utilizing compatibility of both the materials. Finally, as shown in Fig. 3C, movable molds 35 and 36 are separated from each other so that a molded article (the panel 1 for the airbag) is taken out. Thereafter, processing such as painting is performed as necessity requires. Therefore, in this embodiment, the main body 10 formed by the instrument panel and the cover body 20 can be made by a continuous one-time injection molding process. Hence, no fixture for connecting both the members as in a conventional case nor connecting work of both the members are required. Accordingly, the number of producing works and cost can be greatly reduced compared with a conventional article. Further, in this example, as shown in Figs. 3A to 3C, a projecting portion 351 of the width W is continuously formed in the opposite mold 35 along a boundary portion of both the cavity portions 41 and 45. Further, a continuous projecting portion 311 is formed along a line S1 in a predetermined end portion of a fixing mold 31. As a result, as shown in Figs. 4 and 5, a groove portion 21 of the width W formed in the shape of a closed curve is formed in a boundary portion of the cover body 20 and the main body 10. The thin wall portion 23 ruptured when the airbag 81 operates and a non-thin wall portion 24 not ruptured when the airbag 81 are formed into shapes of continuous lines S1 and R1 (Fig. 2) along the groove portion 21. As mentioned above, the groove portion 21 (Fig. 2) having the closed curve shape can be easily formed by forming the projecting portion 351 located in a peripheral portion of the opposite mold 35 and projected from this peripheral portion and having the relatively narrow width W. Further, the projecting portion 311 is formed in the fixing mold 31 and is opposed to the groove portion 21. Accordingly, in a position adjacent to the groove portion 21, the thin wall portion 23 thinner than wall portions in the other positions can be formed simultaneously with the molding. The thin wall portion 23 is easily ruptured when pressure caused by swelling-out of the airbag 81 is applied to this thin wall portion 23. Therefore, the thin wall portion 23 becomes a ruptured portion when the airbag 81 operates. The non-thin wall portion 24 is formed into a shape of one transversal line on an upper side of the cover body 20. The thin wall portion 23 (thickness T) is formed into a quadrilateral shape with one side opened along the groove portion 21 in three directions except for the line R1 forming the non-thin wall portion 24 as indicated by the line S1 (see Fig. 2). Therefore, a cover portion ruptured in the opening shape on one side of the quadrilateral is easily opened with the linear non-thin wall portion 24 as a rotating center. As shown in Fig. 2, the boundary portion of the cover body 20 and the main body 10 can be easily observed by forming the groove portion 21. Further, an excellent appearance in design can be obtained depending on a shape of the groove portion 21. Embodiment 2 In this embodiment, as shown in Fig. 6, a rib 25 is projected in the non-thin wall portion 24 in Embodiment 1, and is connected to an airbag case 82 with a connecting member. Namely, the rib 25 projected onto a rear side of the cover body 20 is supported by a metallic retainer 251 having a bead for preventing falling-out on its surface. This rib 25 is fixed to a bracket 811 of the airbag case 82 with a bolt 252 and a nut 253. In this figure, reference numeral 255 designates a fixture for fixing the bracket 812 of the airbag case 82 to the main body 10. In an injection molding process of the panel, a concave portion 331 is formed in the fixing mold 33 as shown in Fig. 7 so that the rib 25 is formed. The panel 1 for the airbag in this embodiment is reinforced by the rib 25. A root portion of the non-thin wall portion 24 having the rib 25 becomes a rotating center of an opening movement of the cover body 20 at its opening time. Namely, when the thin wall portion 23 is ruptured, a ruptured portion formed into a quadrilateral shape with one side opened of the cover body 20 is rotated and opened with a root C (Fig. 6) of the rib 25 as a rotating center. The rib 25 is tightly fixed to the bracket 811 of the airbag case 82 the connecting member. Accordingly, when the cover body 20 is separated from the main body 10 at the operating time of the airbag 81, the cover body 20 is neither shifted from the airbag case 82 nor is scattered. The other elements are similar to those of Embodiment 1. Embodiment 3 In this embodiment, as shown in Fig. 8, a minimum thickness T1 of the non-thin wall portion 24 is set to be 1.5 times or more a thickness T2 of the cover body 20 in Embodiment 2. The minimum thickness T1 is increased as mentioned above to reinforce the non-thin wall portion. Accordingly, if the retainer 251 is dislocated from the bracket 811 by the operation of the airbag 81, the non-thin wall portion 24 as a rotating center of the opening movement of the cover body 20 is hardly ruptured. Therefore, it is possible to obtain a panel 1 for the airbag with higher safety. The other elements are similar to those of Embodiment 2. Embodiment 4 In this embodiment, the non-thin wall portion 24 is formed into a shape of one transversal line on an upper side of the cover body 20 in Embodiments 2 and 3. Further, as shown in Fig. 9, the thin wall portion 23 is formed along the entire periphery of the groove portion 21 as shown by a closed curve S2 such that a line R1 forming the non-thin wall portion 24 is included in an inner side. The thin wall portion 23 is formed in a shape of the closed curve S2, but no cover body 20 is connected to the airbag case 82 through the rib 25. Accordingly, when the thin wall portion 23 formed on the closed curve S2 is entirely ruptured throughout the entire periphery and is separated from the main body 10, the cover body 20 is neither separated nor scattered when the airbag is operated. In addition, the cover body 20 is separated from the main body 10 by entirely rupturing the thin wall portion 23 formed on the closed along its entire periphery and this leads to the following advantages. Namely, no tensile stress is applied to the main body 10 by the cover body 20 when the airbag is operated. Accordingly, situations hardly occur in which the main body 10 is damaged by stress caused by operating the airbag and is partially damaged and scattered in a certain case. Therefore, safety of the airbag is greatly improved. The other elements are similar to those of Embodiments 2 and 3. Embodiment 5 In this embodiment, as shown in Figs. 10 and 11, the non-thin wall portion 24 having the rib 25 in Embodiment 2 is formed in the shapes of transversal one lines R1 and R2 on upper and lower sides of the cover body 20, respectively. As shown in Fig. 10, the thin wall portion 23 is formed in the shapes of longitudinal one lines S31 and S32 on the left-hand and the right-hand sides of the cover body 20, respectively. Further, a second thin wall portion 26 (Fig. 11) which is not formed along the groove portion 21 is formed in the shape of a transversal one line S33 in a central portion of the cover body 20. The first and second thin wall portions 23 and 26 are entirely formed in an H-shape. In this embodiment, the central second thin wall portion 26 is ruptured when the airbag is operated. An opening portion of the cover body 20 is easily opened on the left-hand and the right-hand sides in Fig. 11 with the non-thin wall portion 24 of the transversal one lines R1 and R2 as a rotating center. The other elements are similar to those of Embodiment 2. Embodiment 6 In this embodiment, as shown in Figs. 12 and 13, no rib 25 is formed in Embodiment 5. Since no rib 25 is formed, the airbag can be produced at a lower cost compared with Embodiment 5. However, since no rib 25 is provided, strength or other properties of the airbag are relatively inferior to those in Embodiment 5. The other elements are similar to those of Embodiment 5. Embodiment 7 In this embodiment, as shown in Fig. 8, a minimum thickness T1 of the non-thin wall portion 24 is set to be 1.5 times or more a thickness T2 of the cover body 20 in Embodiment 5. The minimum thickness T1 is increased as mentioned above to reinforce the non-thin wall portion. Accordingly, if the retainer 251 is dislocated from the bracket 811 by the operation of the airbag 81, the non-thin wall portion 24 as a rotating center of the opening movement of the cover body 20 is hardly ruptured. Therefore, it is possible to obtain a panel 1 for the airbag with excellent safety. The other elements are similar to those of Embodiment 5. Embodiment 8 In this embodiment, as shown in Fig. 14, the thin wall portion 23 is formed on transversal one lines S34 and S35 on upper and lower sides of the cover body 20 in Embodiment 5. The first and second thin wall portions 23 and 26 are entirely formed in a shape in which two quadrilaterals are lined up. In this embodiment, the thin wall portion 23 formed on a closed curve is entirely ruptured throughout the entire periphery so that the cover body 20 is separated from the main body 10 at the operating time of the airbag. As a result, no tensile stress from the cover body 20 is applied to the main body 10 at the operating time of the airbag. Accordingly, situations hardly occur in which the main body 10 is damaged by stress caused by operating the airbag and is partially damaged and scattered in a certain case. Therefore, safety of the airbag is improved. The other elements are similar to those of Embodiment 5. Embodiment 9 In this embodiment, as shown in Figs. 15 and 16, the non-thin wall portion 24 in Embodiment 2 is formed in the shapes of longitudinal one line R3 and R4 on the left-hand and the right-hand sides of the cover body 20, respectively. The thin wall portion 23 is formed in the shapes of transversal one lines S34 and S35 on upper and lower sides of the cover body 20, respectively. Further, a second thin wall portion 26 which is not formed along the groove portion 21 is formed in the shape of a longitudinal one line S36 in a central portion of the cover body 20. The first and second thin wall portions 23 and 26 are entirely formed in an H-shape. In this embodiment, the central second thin wall portion 26 is ruptured when the airbag is operated. An opening portion of the cover body 20 is easily opened on the left-hand and the right-hand sides in Fig. 11 with the non-thin wall portion 24 as a rotating center. The other elements are similar to those of Embodiment 2. Embodiment 10 In this embodiment, no rib 25 is formed in Embodiment 9. Since no rib 25 is formed, the airbag can be produced at a lower cost compared with Embodiment 9. However, since no rib 25 is provided, strength or other properties of the airbag are relatively inferior to those in an airbag with the rib. The other elements are similar to those of Embodiment 9. Embodiment 11 In this embodiment, as shown in Fig. 8, a minimum thickness T1 of the non-thin wall portion 24 is set to be 1.5 times or more a thickness T2 of the cover body 20 in Embodiment 9. The minimum thickness T1 is increased as mentioned above to reinforce the non-thin wall portion. Accordingly, if the retainer 251 is dislocated from the bracket 811 by the operation of the airbag 81, the non-thin wall portion 24 as a rotating center of the opening movement of the cover body 20 is hardly ruptured. Therefore, it is possible to obtain a panel 1 for the airbag with excellent safety. The other elements are similar to those of Embodiment 9. Embodiment 12 In this embodiment, as shown in Fig. 17, the thin wall portion 23 is formed on longitudinal one lines S31 and S32 on the right-hand and the left-hand sides of the cover body 20 in Embodiment 9. The first and second thin wall portions 23 and 26 are entirely formed in a shape in which two quadrilaterals are lined up. In this embodiment, the thin wall portion 23 formed on a closed curve is entirely ruptured throughout the entire periphery so that the cover body 20 is separated from the main body 10 at the operating time of the airbag. As a result, tensile stress from the cover body 20 does not act to the main body 10 at the operating time of the airbag. Accordingly, danger hardly occurs that the main body 10 is damaged by stress caused by operating the airbag and is partially damaged and scattered in a certain case. Therefore, safety of the airbag is improved. The other elements are similar to those in Embodiment 9. Embodiment 13 In this embodiment, as shown in Fig. 18, a concavo-convex portion 159 is formed in a sawtooth shape on a lower face of the main body 10 in an overlapping portion 15. This concavo-convex portion 159 is formed in a non-thin wall portion as well as in the thin wall portion 23. This concavo-convex portion 159 is formed by using a core 32 imparted a concavo-convex shape which is used in molding and then molding the main body 10 and the cover body 20 by two-color molding by using this core 32 similarly to Embodiment 1. The thin wall portion t has 0.8 mm in thickness. The other elements are similar to those of Embodiment 1. In this embodiment, the concavo-convex portion 159 having the sawtooth shape is formed in the overlapping portion 15 of the main body 10. Therefore, both the members are tightly joined because of an anchor effect of the cover body 20 in this concavo-convex portion 159. Accordingly, the cover body 20 is neither dislocated from the main body 10 nor scattered when the airbag is operated. In this embodiment, effects similar to those of Embodiment 1 can be also obtained. Embodiment 14 In this embodiment, as shown in Fig. 19, a concavo-convex portion 158 is formed in a downward convex shape on a lower face of the main body 10 in an overlapping portion 15. The other elements are similar to those of Embodiment 13. In this embodiment, similarly to the Embodiment 13, the anchor effect is improved by the concavo-convex portion 158 in the overlapping portion 15 so that joining strength of the cover body 20 to the main body 10 is improved. In this embodiment, effects similar to those of Embodiment 1 can be also obtained. Embodiment 15 As shown in Fig. 20, a panel for an airbag in this embodiment has a melt-bonded portion 157 formed in an overlapping portion 15 such that the main body 10 and the cover body 20 are joined by high frequency induction heating or vibrational melt-bonding. The other elements are similar to those of Embodiment 13. In this embodiment, the melt-bonded portion 157 is formed by joining both the members 10 and 20 by the high frequency induction heating or the vibrational melt-bonding. Therefore, joining strength of both the members is improved. In this embodiment, effects similar to those in the Embodiment 13 can be also obtained. Embodiment 16 Fig. 21 shows an enlarged perspective view of a forward passenger seat side part of an instrument panel as an example of the panel 1 for an airbag. The instrument panel is formed by a hard synthetic resin material such as polypropylene (PP) mixed with rubber and a filler. An opening portion 12 as an airbag swelling-out port having a substantially rectangular shape is formed on an upper face of a main body 10 of this instrument panel in its central position in a back and forth direction (a slanting vertical direction in Fig. 21) of the main body 10. This opening portion 12 is closed by a cover body 20 molded by two-color molding described later and constructed by a PC (polycarbonate)/ABS(acrylonitrile butadiene styrene) alloy incompatible with PP. Fig. 22 shows a cross section of this opening portion 12. In Fig. 22, an outer peripheral edge 205 of the cover body 20 is bent along the lower face of an opening edge 105 of the opening portion 12 of the main body 10, and is caulked and fixed by bosses 14 projected on this lower face. Namely, as shown in Fig. 21, many bosses 14 are spaced from each other on the lower face of the opening edge 105 of the main body 10 and are formed in a peripheral shape. These bosses 14 downward extend through the outer peripheral edge 205 of the cover body 20, and their end tips are crushed by heat so that a caulking state is formed. Thus, the cover body 20 is tightly connected to the main body 10. An outer peripheral surface of the cover body 20 is stepwise lowered in its entire periphery so that a groove portion 21 is formed in a concave shape between this outer peripheral surface and an opening peripheral face of the opening portion 12. A rib 25 is formed on a rear face of the cover body 20 on its front side (a left-hand side of the cover body 20 in Fig. 22). This rib 25 is formed in the shape of a straight line along this rear face of the cover body 20 and is projected slantingly forward. This rib 25 is covered with a metallic retainer 251. The rib 25 is connected to a bracket 811 located behind the cover body 20 by a bolt 252 and a nut 253. An airbag case 82 storing an airbag 81 therein is fixed by the bolt 252 and the nut 253 to an insert material 13 of the main body 10 with the bracket 812. The rear face of the cover body 20 along its three sides except for the front side is deeply recessed towards the surface, and a thin wall portion 23 to be ruptured when the airbag inflates is formed between this rear face and the groove portion 21 having a concave shape. Accordingly, when the airbag inflates, the thin wall portion 23 (Fig. 21) on the three sides of the cover body 20 is ruptured so that the cover body 20 is opened into a cabin (on an upper side in Fig. 2) with a portion near a root of the rib 25 as a hinge center and the airbag 81 is swollen out of the opening portion 12. Such a panel 1 for the airbag is produced by two-color molding explained below. Namely, in Fig. 23, a convex strip 52 having the same shape as the groove portion 21 having the concave shape is formed in a slide type opposite mold 51 within an upper mold 5 in an outer periphery of its molding face. An end face of a slide core 61 within a lower mold 6 comes in press contact with an end face of this convex strip 52, and a cover body molding cavity C1 and a main body molding cavity C2 outside this cavity C1 are separated from each other. Further, many columnar concave portions 62 are spaced from each other in a peripheral shape on an end face of the slide core 61 and extend to the interior of the slide core 61 at a constant depth. These concave portions 62 are communicated with the main body molding cavity C2. A PP material is injected into such a main body molding cavity C2 so that the main body 10 is molded. At this time, the PP material is simultaneously supplied into each of the concave portions 62 so that the above-mentioned bosses 14 are molded. While the hard synthetic resin material within the main body molding cavity C2 is yet in a semisolid state, the slide core 61 is subsequently retreated by a constant amount as shown in Fig. 24, and the main body molding cavity C2 and the cover body molding cavity C1 are communicated with each other. In this state, a PC/ABS alloy material incompatible with the PP material is injected into the cover body molding cavity C1. The cover body molding cavity C1 is filled with the PC/ABS alloy material. This PC/ABS alloy material also enters a clearance cavity C3 yielded by retreating the slide core 61 and becomes an outer peripheral edge 205 of the cover body 20 so that it fills peripheral portions of the bosses 14. The PC/ABS alloy material is taken out of the mold in this state, and end tips of the bosses 14 projected from the lower face of the opening edge 105 of the opening portion 12 (Fig. 22) of the main body 10 are crushed and caulked by heat. Embodiment 17 Fig. 25 shows an enlarged perspective view of a forward passenger seat side part of an instrument panel as an example of the panel 1 for an airbag. The instrument panel is formed by a thermoplastic hard synthetic resin material such as polypropylene (PP) mixed with rubber and a filler. An opening portion 12 having a substantially rectangular shape is formed on an upper face of a main body 10 of the instrument panel in its central position in a back and forth direction (a slanting vertical direction in Fig. 33) of the main body 10. This opening portion 12 is closed by a cover body 20 molded by integrally two-color molding described later and constructed by olefin thermoplastic elastomer (TPO), etc. Fig. 26 shows a cross section of this opening portion 12. In Fig. 26, an outer peripheral edge 205 of the cover body 20 is bent along the lower face of a peripheral edge of the opening portion 12 of the main body 10, and this peripheral edge and the outer peripheral edge 205 are melt-bonded to each other. An outer peripheral surface of the cover body 20 is stepwise lowered in its entire periphery so that a groove portion 21 is formed in a concave shape between this outer peripheral surface and an opening peripheral face of the opening portion 12. A rib 25 is formed on a rear face of the cover body 20 on its front side (a left-hand side of the cover body 20 in Fig. 34). This rib 25 extends along this rear face and is projected slantingly forward in the shape of a straight line. This rib 25 is covered with a metallic retainer 251. The rib 25 is connected to a bracket 811 of an airbag case 82 located behind the cover body 20 by a bolt 252 and a nut 253. The airbag case 82 which stores an airbag 81 is fixed by the bolt 252 and the nut 253 to an insert material 13 of the main body 10 with a bracket 812. The rear face of the cover body 20 along its three sides except for the front side is deeply recessed in a surface direction, and a thin wall portion 23 which ruptures at an inflating time of the airbag is formed between this rear face and the groove portion 21 having the concave shape. Accordingly, when the airbag inflates, the thin wall portion 23 (Fig. 25) on the three sides of the cover body 20 is ruptured so that the cover body 20 is opened into a cabin (upward in Fig. 26) with a portion near a root of the rib 25 as a hinge center and the airbag is swollen out of the opening portion 12. Here, a concave groove 114 having a rectangular section is formed in a loop shape (Fig. 25) on a lower face of the main body 10 in an external position near a melt-bonded portion of the outer peripheral edge 205 of the cover body 20 so as to surround the outer peripheral edge 205. This concave groove 114 constitutes a deformation restricting portion. Such a panel 1 for the airbag is produced by two-color molding explained below. Namely, in Fig. 27, a convex strip 52 having the same shape as the groove portion 21 having the concave shape is formed in a slide type opposite mold 51 within an upper mold 5 in an outer periphery of its molding face. An end face of a slide core 61 within a lower mold 6 comes in press contact with an end face of this convex strip 52, and a cover body molding cavity C1 and a main body molding cavity C2 outside this cavity C1 are separated from each other. A convex strip 62 having a rectangular cross section and a predetermined height is formed on a molding face of the lower mold 6 so as to surround the exterior of the slide core 61. This convex strip 62 is projected into the main body molding cavity C2. A hard synthetic resin material is injected into such a main body molding cavity C2 so that the main body 10 is molded. While the hard synthetic resin material within the main body molding cavity C2 is yet in a semisolid state, the slide core 61 is subsequently retreated by a constant amount as shown in Fig. 36, and the main body molding cavity C2 and the cover body molding cavity C1 are communicated with each other. In this state, a thermoplastic elastomer material compatible with the hard synthetic resin material is injected into the cover body molding cavity C1. The cover body molding cavity C1 is filled with the elastomer material. This elastomer material also enters a clearance cavity C3 caused by retreating the slide core 61 and becomes an outer peripheral edge 205 of the cover body 20 and is melt-boded to a lower face of the main body 10 in the semisolid state. As shown in Fig. 29, as the elastomer material flows into the clearance cavity C3 (an arrow in Fig. 29), a large injecting pressure is applied to the main body 10 in the semisolid state and each portion of the peripheral edge of the opening portion 12 of the main body 10 is retreated and deformed according to the applied pressure as shown by a chain line in Fig. 29. Thus, as described in the conventional problems, the peripheral edge of the opening portion 12 is shifted from its predetermined shape, resulting in a wavy shape. Here, in this embodiment, as already described, the convex strip 62 having a predetermined height is formed on a molding face of the lower mold 6. Therefore, the above-mentioned concave groove 114 as a deformation restricting portion is formed by this convex strip 62 on the rear face (a lower face in Fig. 29) of the main body 10 in the semisolid state. A side face 114a of the concave groove 114 is engaged with a side face 62a of the convex strip 62 and prevents the retreating deformation of the main body 10 at the peripheral edge of the opening portion 12 against the injecting pressure. As a result, a wavy deforming phenomenon of the opening portion 12 at its peripheral edge is effectively dissolved. Embodiment 18 Effects similar to those in Embodiment 17 are also obtained when a concave groove 63 having a rectangular cross section is formed as a deformation restricting portion on a molding face of a lower mold 6 as shown in Fig. 30 and a convex strip 115 having a rectangular section and a side face 115a engaged with a side face 63a of the concave groove 63 is formed on the rear face of the main body 10. In this case, it is advantageous in strength since no thickness of the main body 10 is reduced. Embodiment 19 The cross sectional shape of the deformation restricting portion is not necessarily set to the rectangular shape as in each of Embodiments 17 and 18, but may be set to such as a curved surface if the cross sectional shape has a face engaged with the mold face and preventing the retreating deformation of the main body at the peripheral edge of the opening portion. Further, it is not necessary to continuously form this deformation restricting portion so as to surround a main body peripheral edge portion, but may be separately spaced from each other. Fig. 31 shows an enlarged perspective view of a forward passenger seat side part of an instrument panel as an example of the panel 1 for an airbag. The instrument panel is formed by a thermoplastic hard synthetic resin material such as polypropylene (PP) mixed with rubber, a filler and the like. An opening portion 12 having a substantially rectangular shape is formed on an upper face of a main body 10 of the instrument panel in its central position in a back and forth direction (a slanting vertical direction in Fig. 31) of the main body 10. This opening portion 12 is closed by a cover body 20 integrally molded by two-color molding and constructed by olefin thermoplastic elastomer (TPO) and the like. Fig. 32 shows a cross section of this opening portion 12. In Fig. 32, an outer peripheral edge 205 of the cover body 20 is bent along the lower face of a peripheral edge of the opening portion 12 of the main body 10, and this peripheral edge and the outer peripheral edge 205 are melt-bonded to each other. An outer peripheral surface of the cover body 20 is stepwise lowered in its entire periphery so that a groove portion 21 is formed in a concave shape between this outer peripheral surface and an opening peripheral face of the opening portion 12. A rib 25 having a plate shape and a constant thickness is formed on a rear face of the cover body 20 on its front side (a left-hand side of the cover body 20 in Fig. 32). This rib 25 extends along this rear face and is projected slantingly forward in the shape of a straight line. A bracket 85 as a connecting member described later in detail is connected to this rib 25. The bracket 85 reaches an airbag case 82 which stores an airbag 81. This airbag case 82 is fixed by a bolt 252 and a nut 253 to an insert material 13 of the main body 10 with a bracket 812. The rear face of the cover body 20 along its three sides except for the front side is deeply recessed towards the surface, and a thin wall portion 23 which ruptures at an inflating time of the airbag is formed between this rear face and the groove portion 21 having the concave shape. Accordingly, when the airbag inflates, the thin wall portion 23 (Fig. 31) on the three sides of the cover body 20 ruptures so that the cover body 20 is opened into a cabin (upward in Fig. 32) with a portion near a root of the rib 25 as a hinge center and the airbag is swollen out of the opening portion 12. As already mentioned above, the bracket 85 is connected to the rib 25 and its detailed construction will next be explained. As shown in Fig. 33, each of notches 831 is formed in a U-shape in an end tip portion of the rib 25 on its plate face. The notches 831 are spaced from each other in a width direction of the rib 25 and extend from an end tip of the rib 25 to the plate interior in plural positions (four positions in this embodiment). The bracket 85 is formed by curving a metallic plate body having a constant width in a substantially U-shape. A base end 853 of the bracket 85 is joined with a side face of the airbag case 82 (Fig. 32) and a plate face of an end tip 854 of the bracket 85 is located along a lower face of the rib 25. Fixing holes 851 are spaced from each other in the width direction on the plate face of the end tip 854 of the bracket 85 and are located in the same positions as the notches 831. As shown in Fig. 34, plural (three on each of left-hand and right-hand sides in this embodiment) projections 852 are formed in left-hand and right-hand positions of the respective fixing holes 851 such that these projections 852 form an inverse V-shape. As shown in Fig. 35, these projections 852 are formed into a trapezoidal shape by punching the plate face of the end tip 854 of the bracket 85 and cut-rising this plate face (Figs. 36 and 37). As shown in Fig. 32, a retainer plate 86 made of a metal is located on an upper face of the rib 25 and is constructed by an elongated plate (Fig. 33) having a length approximately equal to the width of the rib 25. Fixing holes 861 are formed on a face of the retainer plate 86 in the same positions as the notches 831 of the rib 25. The rib 25 and the bracket 85 are connected to each other by locating the respective fixing holes 861 and 851 of the retainer plate 86 and the bracket 85 in conformity with positions of the notches 831 of the rib 25, and inserting a bolt 252 (Fig. 32) into each of these fixing holes 861 and 851 and fastening this bolt 252 by a nut 253. In this fastening, the projections 852 formed on the plate face of the end tip 854 of the bracket 85 is bitten into the plate face of the rib 25 formed by a synthetic resin material. When the airbag is operated, the thin wall portion 23 (Fig. 31) is ruptured as the airbag inflates as already mentioned above. The cover body 20 is rotated and opened into a cabin with a portion near a root of the rib 25 as a hinge center. At this time, the heat of an inflater within the airbag case 82 is transmitted to the cover body 20 so that the synthetic resin material of the cover body 20 is softened and pulling-up force is upward applied to the cover body 20. Here, since the projections 852 of the bracket 85 are bitten into the rib 25 of the cover body 20 so that the rib 25 and the bracket 85 are connected to each other, no rib 25 is separated from the bracket 85 even when the synthetic resin material is softened in this biting portion. Thus, scattering of the cover body 20 can be reliably prevented. Embodiment 21 The arrangement of the projections 852 is not limited to that in Embodiment 20. For example, as shown in Fig. 38, the projections 852 may be arranged in a straight line in left-hand and right-hand positions of the fixing holes 851, or may be arranged in a horseshoe shape surrounding each of the fixing holes 851 as shown in Fig. 39. Further, the shape of the projections 852 is not limited to that in Embodiment 26 if the projections 852 are easily bitten into the synthetic resin material of the rib 25. For example, the projections 852 can be formed in such as a wedge shape. Further, since the number of this arrangement of the projections 852 is determined in design according to a using situation, the number of this arrangement is not limited to that in Embodiment 20. In Embodiment 20, the instrument panel as an example is explained as an inner mounting material made of synthetic resin. However, a door trim and the like may be arranged as this inner mounting material. Further, a base end of the bracket 85 may be also fixed to a structural member on an instrument panel side or a door trim side instead of a structure in which this base end is fixed to the airbag case.

Claims: A panel for an airbag of an automobile formed by integrally molding a cover body (20) made of a synthetic resin with a main body (10) made of another synthetic resin, the panel comprising: a joint portion joined with the cover body provided around an opening portion (12) formed in the main body (10), wherein the joint portion constitutes an overlapping portion (15) in which an outer peripheral edge (205) of the cover body (20) is overlapped as being arranged on the inner side of an opening edge (105) of the main body (10). The panel for an airbag according to claim 1, wherein the synthetic resin of the main body is a hard synthetic resin and the synthetic resin of the cover body is a soft synthetic resin. The panel for an airbag according to claim 1, wherein a concavo-convex portion (158, 159) having a serrate shape or a downward convex shape is formed on a lower face of the main body (10) in the overlapping portion (15). The panel for an airbag according to claim 1, wherein the main body (10) and the cover body (20) are joined in the overlapping portion (15) by high frequency induction heating and vibration melt-bonding. The panel for an airbag according to claim 1, wherein a groove portion (21) having a closed curve shape is formed in a boundary portion of an end portion of the opening portion of the main body (10) in the cover body (20), and a thin wall portion (23) which ruptures and a non-thin wall portion (24) which does not rupture at operating time of the airbag are formed along the groove portion in the cover body in a single line shape or a shape of plural continuous lines. The panel for an airbag according to claim 5, wherein the non-thin wall portion (24) is formed into a shape of one transversal line on an upper or lower side of the cover body (20), and the thin wall portion (23) is formed in a quadrilateral shape with one side opened along a groove portion in three directions except for the line forming the non-thin wall portion. The panel for an airbag according to claim 5, wherein the non-thin wall portion (24) is formed into a shape of one transversal line on an upper or lower side of the cover body (20) and the thin wall portion (23) is formed along an entire periphery of the groove portion such that a line (R1) forming the non-thin wall portion is included in an inner side. The panel for an airbag according to claim 5, wherein the non-thin wall portion (24) can be formed into a shape of one transversal line (R1, R2) on each of upper and lower sides of the cover body (20), and the thin wall portion (23) is formed into a shape of one longitudinal line (S31, S32) on each of left-hand and right-hand sides of the cover body; wherein a second thin wall portion (26) which is not formed along a groove portion (21) is formed into a shape of one transversal line (S33) in a central portion of the cover body (20); and wherein the entire of the first and second thin wall portions can be formed in an H-shape. The panel according for an airbag to claim 5, wherein the non-thin wall portion (24) is formed into a shape of one transversal line on each of upper and lower sides of the cover body, and the thin wall portion (23) is formed along an entire periphery of a groove portion such that a line forming the non-thin wall portion is included in an inner side; wherein a second thin wall portion (26) which is not formed along the groove portion is formed into a shape of one transversal line in a central portion of the cover body; and wherein the entire of the first and second thin wall portions (23, 26) is formed in a shape in which two quadrilaterals are lined up. The panel for an airbag according to claim 5, wherein the non-thin wall portion (24) can be formed into a shape of one longitudinal line (R3, R4) on each of left-hand and right-hand sides of the cover body, and the thin wall portion (23) is formed into a shape of one transversal line (S34, S35) on each of upper and lower sides of the cover body; wherein a second thin wall portion (26) which is not formed along a groove portion (21) is formed into a shape of one longitudinal line (S36) in a central portion of the cover (20); and wherein the entire of the first and second thin wall portions is formed in an H-shape. The panel for an airbag according to claim 5, wherein the non-thin wall portion (24) can be formed into a shape of one longitudinal line on each of left-hand and right-hand sides of the cover body, and the thin wall portion (23) is formed along an entire periphery of a groove portion such that a line forming the non-thin portion is included with an inner side; wherein a second thin wall portion (26) is not formed along the groove portion but is formed into a shape of one longitudinal line in a central portion of the cover body; and wherein the entire of the first and second thin wall portions is formed in a shape in which two quadrilaterals are lined up. The panel for an airbag according to claim 5, wherein a rib (25) is projected in the non-thin wall portion (24) and connected to the airbag case through a connecting member (85). The panel according to claim 1, wherein an opening edge of the opening portion (12) of the main body (10) is mechanically connected to an outer peripheral edge of the cover body. The panel for an airbag according to claim 12, wherein the connecting member (85) is made of a metal, extends from a side of the main body (10) and is connected to the rib, and a projection (852) is formed on a surface or this connecting member and is bitten into a surface of the rib (25) when the connecting member is connected to the rib. A method for producing a panel for an airbag of an automobile formed by integrally molding a cover body made of a synthetic resin with a main body made of another synthetic resin, the method comprising: preparing a thermoplastic material having compatibility as the synthetic resin forming each of the main body and the cover body; arranging a movable core (32; 61) in a male or female die (31; 6) as a mold; interrupting a portion between a first cavity portion (41; C2) for for forming a first member (10) and a second cavity portion (45; C1) for forming a second member (20) by allowing the core (32; 61) to project and contact an opposite die (35; 51); injecting a material of the first member (10) into the first cavity portion (41; C2); forming a communicating portion between the first and second cavity portions (41, 45; C2, C1) by retreating the core (32; 61); and injecting a material of the second member (20) into the second cavity portion (45; C1) and the communicating portion so that an overlapping portion (15) of both the first and second members (10, 20) is formed and adhered and both the first and second members are integrally made. A method for producing a panel for an airbag according to claim 15, wherein the cover body (20) is formed by two-colour molding after forming the main body (10); the movable core (61) is a slide core arranged in the male or female die (6) which is formed with a convex strip (62) and/or a concave groove (63) along a peripheral edge of its molding face so as to surround the exterior of the slide core (61); the first member is the main body (10) and the second member is the cover body (20); and surface portions of the main body (10), formed by the convex strip (62) or the concave groove (63) of the molding surface and being engaged with them, act as a deformation restricting portion which restricts deformation of the main body (10) caused by a molding pressure which acts at molding time of the cover body (20). Method for producing a panel for an airbag according to claim 16, wherein the convex strip (62) has an angular cross-section.

Inventors: FUKUDA HARUO, FURUKAWA YUSAKU, HAYASHI ISAO, INOMATA NOBUO, KANAYAMA TORAO, KONDO YASUO, MIWA AKIHIRO, OKANO TSUTOMU, UEDA TAKASHI, YAMADA HIROFUMI, FUKUDA, HARUO, FURUKAWA, YUSAKU, HAYASHI, ISAO, INOMATA, NOBUO, KANAYAMA, TORAO, KONDO, YASUO, MIWA, AKIHIRO, OKANO, TSUTOMU, UEDA, TAKASHI, YAMADA, HIROFUMI, FUKUDA, Haruo, Toyota Shatai Kabushiki Kaisha, FURUKAWA, Yusaku, Toyota Shatai Kabushiki Kaisha, HAYASHI, Isao, Toyota Shatai Kabushiki Kaisha, INOMATA, Nobuo, Toyota Shatai Kabushiki Kaisha, KANAYAMA, Torao, Toyota Shatai Kabushiki Kaisha, KONDO, Yasuo, Toyota Shatai Kabushiki Kaisha, MIWA, Akihiro, Toyota Shatai Kabushiki Kaisha, OKANO, Tsutomu, Toyota Shatai Kabushiki Kaisha, UEDA, Takashi, Toyota Shatai Kabushiki Kaisha, YAMADA, Hirofumi, Toyota Shatai Kabushiki Kaisha
Applicants: TOYOTA AUTO BODY CO LTD, TOYOTA SHATAI KABUSHIKI KAISHA
Application year: 1998
Main classification: B60R21
IPC codes: B60R21, B65D65, B29C45