JP6642376B2 - Airbag cover and method of manufacturing the same - Google Patents

Description

  The present invention relates to an airbag cover for covering an airbag of a vehicle.

In recent years, it has been desired to reduce the weight of a vehicle, and it is also desired to reduce the weight of a resin molded body constituting a part of the vehicle.
One of the methods for reducing the weight of the resin molded body is a foam molding method. The foam molding method is a resin molding method in which a foamed resin material is foamed in a cavity of a mold. The foamed resin molded article obtained by the foam molding method has many pores inside. Since the pores contain gas, the foamed resin molded article has a relatively low density and is lightweight.

  The airbag cover is a resin molded body for covering an airbag mounted on a vehicle. A typical airbag cover has a cover, a base surrounding the cover, and a tear line provided on the cover. The tear line portion is generally thinner than a portion of the cover portion other than the tear line portion (referred to as a general cover portion), and is broken by being pressed by an airbag that is deployed at the time of sudden braking or the like. When the tear line portion is broken and the cover portion is deformed, the airbag covered by the cover portion can be deployed in the vehicle interior.

  As a method of manufacturing this type of airbag cover using a foam molding method, a base and a skin material are set in a cavity of a molding die, and a foaming resin material is injected between the base and the skin material to form a foam. A method of forming a foamed portion made of a resin molded body has been proposed (for example, see Patent Document 1). However, the method for manufacturing the airbag cover has a problem that it is difficult to reduce the manufacturing cost of the airbag cover because the number of steps and the number of parts are relatively large.

  As a method of reducing the manufacturing cost of the airbag cover, a method of forming the airbag cover using only the foamed resin molded article can be considered. The portion of the foamed resin material that is injected into the cavity and that comes into contact with the mold surface of the mold is solidified before foaming due to cooling by the mold and becomes a non-foamed portion. Other portions of the foamed resin material injected into the cavity foam and become foamed portions. The non-foamed portion is also called a skin layer, and constitutes part or all of the surface of a general foamed resin molded article. For this reason, if the non-foamed portion is regarded as a skin material, there is a possibility that the airbag cover can be constituted only by the foamed resin molded body.

  However, the airbag cover composed of only the above-mentioned foamed resin molded article may not be able to exhibit the performance required for the airbag cover. In particular, in the airbag cover composed only of the foamed resin molded article described above, when the airbag is deployed and the tear line portion is broken, even the cover portion is broken, and the airbag cover is positioned at an intended position. Is difficult to break. Therefore, there is a demand for further improvement of a technology capable of manufacturing a lightweight airbag cover at low cost.

JP-A-2002-104124

  The present invention has been made in view of the above circumstances, and an object of the present invention is to further improve a technology capable of manufacturing a lightweight airbag cover at low cost.

The airbag cover of the present invention that solves the above problems,
A resin airbag cover for covering the airbag,
A cover portion, a base portion surrounding the cover portion, and a tear line portion provided on the cover portion,
The tear line portion is thinner than the base portion and is constituted by a non-foamed portion,
The base is an airbag cover that includes a non-foamed portion and a foamed portion.

A method for manufacturing an airbag cover of the present invention that solves the above-mentioned problems,
A foam resin material is injected into a cavity formed between the first mold and the second mold to have a cover, a base surrounding the cover, and a tear line provided in the cover. A method of manufacturing an airbag cover, comprising:
The cavity is configured by a tear line cavity forming the tear line portion, a general cover cavity forming the cover portion other than the tear line portion, and a base cavity forming the base portion,
A method of manufacturing an airbag cover, comprising: increasing the thickness of the base cavity while maintaining the thickness of the tear line cavity after injecting the foamed resin material into the cavity.

Another aspect of the method for manufacturing an airbag cover of the present invention that solves the above problems is
A foam resin material is injected into a cavity formed between the first mold and the second mold to have a cover, a base surrounding the cover, and a tear line provided in the cover. A method of manufacturing an airbag cover, comprising:
The cavity is configured by a tear line cavity forming the tear line portion, a general cover cavity forming the cover portion other than the tear line portion, and a base cavity forming the base portion,
After injecting the foamed resin material into the cavity,
First, increasing the thickness of the tear line cavity, the thickness of the general cover cavity, and the thickness of the base cavity,
Next, a method of manufacturing an airbag cover, wherein the thickness of the tear line cavity is reduced while the thickness of the base cavity is maintained.

  According to the technique of the present invention, a lightweight airbag cover can be manufactured at low cost.

FIG. 2 is an explanatory diagram schematically illustrating an appearance of the airbag cover of the first embodiment. FIG. 2 is an explanatory diagram schematically illustrating a state in which the airbag cover of the first embodiment is cut at a position AA in FIG. 1. FIG. 4 is an explanatory diagram schematically illustrating a method for manufacturing the airbag cover of the first embodiment. FIG. 4 is an explanatory diagram schematically illustrating a method for manufacturing the airbag cover of the first embodiment. FIG. 9 is an explanatory view schematically illustrating a method for manufacturing the airbag cover of the second embodiment. FIG. 9 is an explanatory view schematically illustrating a method for manufacturing the airbag cover of the second embodiment. FIG. 9 is an explanatory diagram schematically illustrating an appearance of an airbag cover according to a third embodiment. FIG. 8 is an explanatory diagram schematically illustrating a state in which the airbag cover of the third embodiment is cut at a position AA in FIG. 7. FIG. 13 is an explanatory diagram schematically illustrating a method for manufacturing the airbag cover of the third embodiment. FIG. 13 is an explanatory diagram schematically illustrating a method for manufacturing the airbag cover of the third embodiment. FIG. 13 is an explanatory diagram schematically illustrating a method for manufacturing the airbag cover of the third embodiment.

  Hereinafter, the airbag cover of the present invention and a method for manufacturing the same will be described with reference to specific examples.

  Unless otherwise specified, the numerical range “xy” described in this specification includes the lower limit x and the upper limit y in the range. Then, a new numerical range can be configured by arbitrarily combining these upper and lower limits and the numerical values listed in the embodiment. Furthermore, numerical values arbitrarily selected from within these numerical ranges can be set as upper and lower limit numerical values.

(Example 1)
The airbag cover according to the first embodiment forms an instrument panel of a vehicle. FIG. 1 is an explanatory diagram schematically illustrating the appearance of the airbag cover of the first embodiment, and FIG. 2 is a schematic diagram illustrating a state in which the airbag cover of the first embodiment is cut along a line AA in FIG. 1. FIG. 3 and 4 are explanatory views schematically illustrating a method of manufacturing the airbag cover according to the first embodiment. Specifically, FIG. 3 shows an intermediate between the cavity and the airbag cover in the injection step, and FIG. 4 shows an intermediate between the cavity and the airbag cover in the foam molding step.

  As shown in FIG. 1, the airbag cover 1 according to the first embodiment forms an instrument panel of a vehicle. The airbag cover 1 includes a cover 2 and a base 3, and the cover 2 includes a tear line 20 and a general cover 21. The base 3 surrounds the cover 2, and the tear line 20 forms a part of the boundary between the cover 2 and the base 3. The base 3 is provided with a mounting opening 30 for various vehicle interior components provided on the instrument panel, such as a meter cluster, a register of an air conditioner, and a defroster.

As shown in FIG. 2, the tear line portion 20 is thinner than the general cover portion 21 and the base 3. Specifically, the maximum thickness of the general cover portion 21 and the base portion 3 is 3 mm, and the thickness of the tear line portion 20 is 0.45 mm. In the airbag cover 1 according to the first embodiment, the thickness of the tear line portion 20 is substantially constant.
The airbag cover 1 is disposed on the vehicle with the front surface 1a facing the interior of the vehicle. An unillustrated airbag is provided on the back surface 1b side of the airbag cover 1. On the front surface 1 a side of the airbag cover 1, the surfaces of the tear line portion 20, the general cover portion 21 and the base 3 are flush, and on the rear surface 1 b side of the airbag cover 1, the surface of the tear line portion 20 is And the surface of the base 3 are depressed. With such a shape, the tear line portion 20 is a portion that is easily broken in the airbag cover 1, so that when the airbag is deployed, the tear line portion 20 is broken. At this time, the general cover portion 21 is pressed by the airbag and is deformed so as to be turned upside down with respect to the base portion 3. Therefore, an opening (not shown) through which the airbag can pass is formed in the airbag cover 1.
The tear line portion 20 of the airbag cover 1 of the first embodiment surrounds the substantially rectangular general cover portion 21 in a substantially U-shape except for one long side 2L. For this reason, even if the tear line portion 20 is broken, the integration of the cover portion 2 and the base portion 3 is maintained at the one long side 2L, and detachment of the cover portion 2 from the airbag cover 1 is suppressed.

  The base portion 3 and the general cover portion 21 include a foamed portion 40 and a non-foamed portion 41. The non-foamed portion 41 is a portion generally called a skin layer, has a layer shape covering the foamed portion 40, and forms the surfaces of the base 3 and the general cover 21. The foamed portion 40 is a porous portion having many pores 50, and the non-foamed portion 41 is a portion having no pores 50 or having only a few pores 50 as compared with the foamed portion 40. The small pores 50 referred to here are small pores 50 as compared with the pores 50 of the foaming section 40, or a small number of pores 50 as compared with the pores 50 of the foaming section 40. The pores 50 in the foaming section 40 may be closed-cell type pores or open-cell type pores. Since the base portion 3 and the general cover portion 21 have the foamed portion 40, the airbag cover 1 of the first embodiment is lightweight. In addition, the base 3 and the general cover 21 in the airbag cover 1 of the first embodiment include the foamed portion 40 and the non-foamed portion 41, and do not have a conventionally required large-mass member such as a base. For this reason, the airbag cover 1 of the first embodiment is much lighter than a conventional airbag cover as introduced in Patent Document 1.

  The tear line portion 20 is thinner than the base portion 3 and includes a non-foamed portion 41. In this way, when the airbag is deployed, that is, when the airbag cover 1 is broken, the tear line portion 20 is easily broken, and the portion formed of the foamed portion 40 and adjacent to the tear line portion 20 (the base portion in the first embodiment). 3 and the transmission of the breakage of the tear line portion 20 to the general cover portion 21). Therefore, the airbag cover 1 according to the first embodiment breaks at an intended position, that is, at the tear line portion 20, although the airbag cover 1 is formed only of the foamed resin molded body without using the base or the skin material.

The tear line portion 20 is constituted by a non-foamed portion 41, and the base 3 is constituted by a foamed portion 40 and a non-foamed portion 41.
The tear line portion 20 is formed of a non-foamed portion 41 having a small thickness so that a break position when the airbag is deployed can be controlled. On the other hand, the base 3 includes a foamed portion 40 for reducing the weight of the airbag cover 1 and a non-foamed portion 41 which is a skin layer covering the foamed portion 40. As described above, the foamed portion 40 only needs to be porous, and the non-foamed portion 41 does not have the pores 50, or has the pores 50 smaller than the pores 50 of the foamed portion 40, Alternatively, it is only necessary to have a small number of pores 50 as compared with the pores 50 of the foamed portion 40. Specifically, the non-foamed portion 41 and the foamed portion 40 can be defined by a pore diameter or a density.

  First, when the foamed portion 40 and the non-foamed portion 41 are defined by the pore diameter, the foamed portion 40 can be a portion having pores 50 having a pore diameter of 10 μm or more. On the other hand, the non-foamed portion 41 can be a portion having no pore 50 having a pore diameter of 1 μm or more. More specifically, a section where the cross section of the airbag cover 1 is observed and a pore 50 having a pore diameter of 1 μm or more is not observed in a 0.3 mm × 0.3 mm test section can be regarded as a non-foamed portion 41. Similarly, by observing the cross section of the airbag cover 1, a portion where a pore 50 having a pore diameter of 10 μm or more is observed in a 0.3 mm × 0.3 mm test section can be regarded as the foamed portion 40. The airbag cover 1 may have a portion other than the foamed portion 40 and the non-foamed portion 41. In some cases, a portion where the number of pores 50 having a pore diameter of 1 μm or more confirmed in the test compartment is 1 or less, 2 or less, or 3 or less is referred to as a non-foamed portion 41. Can also be considered.

  The tear line portion 20 may be thinner than the general cover portion 21 and the base portion 3. However, the tear line portion 20 preferably has a thickness of 1 mm or less, and 0.8 mm It is more preferably at most 0.6 mm, more preferably at most 0.6 mm, particularly preferably at most 0.5 mm. The thickness of the non-foamed portion 41 in the general cover portion 21 and the base portion 3 (that is, the thickness of the so-called skin layer) is not particularly limited, but is generally 0.1 mm or more and 1 mm or less.

  Hereinafter, a method for manufacturing the airbag cover of the first embodiment will be described.

  The airbag cover 1 according to the first embodiment is manufactured through the following preparation step, injection step, pressure-holding step, and foam molding step using a molding die 6 including a first die 61 and a second die 62. .

  The molding die 6 includes a first die 61 and a second die 62. The first mold 61 is a fixed mold, and the second mold 62 is a movable mold. The second mold 62 includes a general movable mold part 70 and a core part 71. The position of the second mold 62, that is, the general movable mold part 70 and the core part 71, can be changed integrally, and the position of the second mold 62 can be changed with respect to the first mold 61 in the direction of opening and clamping. Further, the general movable mold part 70 can also move relative to the core part 71, and can move in the mold opening and mold clamping direction with respect to the first mold 61. The mold surface of the first mold 61 mainly forms the front surface 1a of the airbag cover 1, and the mold surface of the second mold 62 mainly forms the back surface 1b of the airbag cover 1.

(Preparation process)
In the preparation step, the molding material is placed in a foaming resin molding machine (not shown) and heated and softened to obtain a fluid foaming resin material. The foamed resin material used in the production method of the example contains polypropylene and ABS as resin components, and contains sodium bicarbonate as a foaming agent. Sodium bicarbonate is thermally decomposed to produce sodium carbonate, water and carbon dioxide. Of these, carbon dioxide can form bubbles in the foamed resin material. In addition, since the decomposition reaction rate increases in the presence of water, the foaming of the foamed resin material by the decomposition reaction can proceed continuously.

(Injection process)
In the injection step, the fluid foam resin material 85 obtained in the above-described preparation step is injected into the cavity 8 of the molding die 6 via an injection machine (not shown). As shown in FIG. 3, the cavity 8 formed between the first mold 61 and the second mold 62 includes a general cover cavity 81, a tear line cavity 82, and a base cavity 83. The tear line cavity 82 is defined by the mold surface of the first mold 61 and the mold surface of the core 71 of the second mold 62 and forms the tear line portion 20. The general cover cavity 81 is defined by the mold surface of the first mold 61, the mold surface of the general movable mold part 70 of the second mold 62, and the mold surface of the core part 71 of the second mold 62. It is the part to be formed. The base cavity 83 is defined by the mold surface of the first mold 61, the mold surface of the general movable mold part 70 of the second mold 62, and the mold surface of the core 71 of the second mold 62, and forms the base 3. It is. In the injection step, the second mold 62 is arranged at the mold clamping position shown in FIG.

  In the injection step, the fluid foamed resin material 85 is injected into the general cover cavity 81, the tear line cavity 82, and the base cavity 83. At this time, the second mold 62, which is a movable mold, is clamped toward the first mold 61 with a force sufficient to maintain the size of the cavity 8 against the fluid pressure by the foamed resin material 85. In other words, at this time, the second mold 62 is clamped toward the first mold 61 with a force sufficient to remain at the mold clamping position shown in FIG. 3 against the fluid pressure by the foamed resin material 85. .

(Packing process)
In the pressure-holding step, following the above-described injection step, while maintaining the mold clamping force in the injection step, the state in which the pressure in the cavity 8 is kept substantially constant is maintained for 0.5 to 3 seconds.
In the above-described injection step and pressure-holding step, a portion of the foamed resin material 85 injected into the cavity 8 that is in contact with the mold surface of the molding die 6 is cooled by the molding die 6, and is subjected to the following foam molding step. To partially solidify. The foamed resin material 85 separated from the mold surface of the molding die 6 remains in a fluid state.

(Foam molding process)
The foam molding process is a process of partially foaming the foamed resin material 85 by changing the position of a part of the mold 6 and changing the thickness of the cavity 8 after the above-mentioned pressure holding process.
Specifically, as shown in FIG. 4, the position of the core portion 71 of the first die 61 and the second die 62 is not changed, and only the general movable die portion 70 of the second die 62 is opened as indicated by an arrow in the figure. Change the position in the direction. By doing so, only the thickness of the base cavity 83 and the thickness of the general cover cavity 81 increase while the thickness of the tear line cavity 82 remains unchanged. Then, the base cavity 83 and the general cover cavity 81 have a negative pressure, and the foamed resin material 85 in the fluid state at the central portion of the base cavity 83 and the general cover cavity 81 foams. By cooling and solidifying the foamed resin material 85 in this state, the foamed portion 40 made of the foamed foamed resin material 85 is formed. Since the foamed resin material 85 in contact with the mold surface of the molding die 6 is solidified before foaming to form the non-foamed portion 41, the base portion 3 and the general cover portion 21 formed by the base cavity 83 and the general cover cavity 81 are formed of 40 and a non-foamed portion 41 covering the foamed portion 40 (FIG. 2).

  On the other hand, as shown in FIG. 4, the thickness of the cavity 8 changes only in the base cavity 83 and the general cover cavity 81 in the foam molding process, and the thickness of the tear line cavity 82 does not change. Therefore, the foamed resin material 85 in the tear line cavity 82 does not foam even in the foam molding step, and is cooled and solidified as it is. Therefore, the tear line portion 20 formed by the tear line cavity 82 is constituted only by the non-foamed portion 41 (FIG. 2).

  In the method of manufacturing the airbag cover 1 of the first embodiment, the lightweight airbag cover 1 can be manufactured at low cost by forming the airbag cover 1 only with the foamed resin material 85 without using the skin material or the base.

  In the method of manufacturing the airbag cover 1 according to the first embodiment, polypropylene is used as the resin material and sodium hydrogen carbonate is used as the foaming agent, but the combination of the resin material and the foaming agent is not limited to this. Preferably, the resin material is a thermoplastic resin. As thermoplastic resins other than polypropylene, polyethylene, polystyrene, polyvinyl acetate, acrylonitrile-butadiene-styrene copolymer resin (so-called ABS resin), acrylonitrile-styrene copolymer resin (so-called AS resin), acrylic resin, polyamide, polyacetal, Examples thereof include polycarbonate, modified polyphenylene ether, polyethylene terephthalate, polybutylene terephthalate, and cyclic polyolefin. Further, a fiber reinforced plastic (a so-called FRP) in which a fiber material is added to these resin materials may be used.

  The foaming agent is also not particularly limited, and a foaming agent having an appropriate foaming performance and foaming temperature may be appropriately selected according to the resin material used. For example, as the foaming agent, a general one that generates a gas by being thermally decomposed can be used. Alternatively, it is possible to use a material whose volume is increased by heat.

  Common foaming agents include inorganic compounds such as sodium bicarbonate, ammonium bicarbonate and ammonium carbonate, azodicarbonamide, 2,2′-azobis9isobutyronitrile, azohexahydrobenzonitrile, and diazoaminobenzene. Azo compounds such as benzenesulfonylhydrazide, benzene-1,3-sulfonylhydrazide, diphenylsulfone-3,3'-disulfonylhydrazide, diphenyloxide-4,4'-disulfonylhydrazide, 4,4'-oxybis9 ( Benzenesulfonyl hydrazide), sulfonyl hydrazide compounds such as paratoluenesulfonyl hydrazide, and nitrites such as N, N'-dinitrosopentamethylenetetramine, N, N'-dinitroso-N, and N'-dimethylphthalamide Seo compounds, terephthalic azide, and the azide compounds such as p-t-butyl-benzimidazole azide and the like.

  Examples of the foaming agent whose volume is increased by heat include a capsule foaming agent. The capsule foaming agent refers to a foaming agent encapsulated in an outer shell made of a thermoplastic resin. Copolymers such as vinylidene chloride, acrylonitrile, acrylates, and methacrylates are used as the thermoplastic resin constituting the outer shell, and isobutane, pentane, petroleum ether, hexane, heptane, low-boiling halogenates are used as blowing agents. Volatile organic solvents such as hydrocarbons and methylsilane are used. Note that the volatile organic solvent is also called a swelling agent.

  In any case, the foaming agent foams, for example, a gas is generated from the foaming agent, a gas is generated by a chemical reaction between the foaming agent and the foaming initiator, or the volume of the gas is increased. Air bubbles are formed in the foamed resin material 85. Then, the foamed portion 40 is formed by expanding or growing the bubble in the foam molding process. The bubbles remain in the foaming section 40 as pores.

  The tear line portion 20 of the airbag cover 1 manufactured by the manufacturing method of the first embodiment may be subjected to a post-processing for forming a further concave fracture starting point portion. In this case, since the stress concentrates on the fracture starting point portion when the airbag is deployed, the tear line is more easily broken when the airbag is deployed.

  In the method of manufacturing the airbag cover according to the first embodiment, only the thickness of the base cavity 83 and the thickness of the general cover cavity 81 are increased in the foam molding process while keeping the thickness of the tear line cavity 82 unchanged. As used herein, not only indicates that the thickness of the tear line cavity 82 does not change, but also allows a change in the thickness of the tear line cavity 82 of about 30%. Even if the thickness of the tear line cavity 82 increases or decreases by about 30%, the tear line portion 20 including the non-foamed portion 41 can be formed.

(Example 2)
The airbag cover of the second embodiment is substantially the same as the airbag cover of the first embodiment except that the general cover portion does not have a foamed portion. The method of manufacturing the airbag cover of the second embodiment is substantially the same as the method of manufacturing the airbag cover of the first embodiment except for the foam molding step. 5 and 6 are explanatory views schematically showing a method of manufacturing the airbag cover according to the second embodiment. Specifically, FIG. 5 shows an intermediate between the cavity and the airbag cover in the injection step, and FIG. 6 shows an intermediate between the cavity and the airbag cover in the foam molding step.

  As shown in FIG. 5, the molding die 6 used in the method of manufacturing the airbag cover of the second embodiment includes a first die 61 and a second die 62. The first mold 61 is the same as the first mold 61 used in the method of manufacturing the airbag cover of the first embodiment, and the second mold 62 is the second mold used in the method of manufacturing the airbag cover of the first embodiment. Different from 62. The first mold 61 is a fixed mold, and the second mold 62 is a movable mold.

  The second mold 62 includes a general movable mold part 70 and a core part 71. The tear line cavity 82 and the general cover cavity 81 are defined by the mold surface of the first mold 61 and the mold surface of the core portion 71 of the second mold 62. The base cavity 83 is defined by the mold surface of the first mold 61, the mold surface of the general movable mold portion 70 of the second mold 62, and the core portion 71. Similarly to the molding die used in the method of manufacturing the airbag cover of the first embodiment, the position of the general movable mold part 70 and the core part 71 can be changed integrally, and the opening and the mold of the first mold 61 can be changed. The position can be changed in the tightening direction. Further, the general movable mold part 70 can also move relative to the core part 71, and can move in the mold opening and mold clamping direction with respect to the first mold 61. The mold surface of the first mold 61 mainly forms the front surface 1a of the airbag cover 1, and the mold surface of the second mold 62 mainly forms the back surface 1b of the airbag cover 1.

  The method of manufacturing the airbag cover of the second embodiment is substantially the same as the method of manufacturing the airbag cover of the first embodiment except for the foam molding step. Therefore, in Example 2, only the foam molding step will be described.

(Foam molding process)
As shown in FIG. 6, in the foam molding step, the position of the core 71 of the first mold 61 and the second mold 62 is not changed, and only the general movable mold 70 of the second mold 62 is indicated by an arrow in the figure. The position is changed in the mold opening direction shown. In the method of manufacturing the airbag cover according to the second embodiment, the general movable mold part 70 forms the base cavity 83, and the core part 71 mainly forms the tear line cavity 82 and the general cover cavity 81. Only the thickness of the base cavity 83 increases while the thicknesses of the line cavity 82 and the general cover cavity 81 remain unchanged. Accordingly, the fluid foamed resin material 85 foams in the base cavity 83, and the base 3 formed by the base cavity 83 includes the foaming part 40 and the non-foaming part 41 covering the foaming part 40 (not shown). . On the other hand, the foamed resin material 85 in the tear line cavity 82 and the general cover cavity 81 does not foam even in the foam molding step, and is cooled and solidified as it is. Therefore, the tear line portion 20 and the general cover portion 21 formed by the tear line cavity 82 and the general cover cavity 81 are constituted only by the non-foamed portion 41 (not shown).

  In the airbag cover of the second embodiment, the general cover portion 21 does not have a foam portion, but the base portion 3 has a foam portion 40. Therefore, the airbag cover of the second embodiment is also lightweight. Further, since the tear line portion 20 is formed only of the thin non-foamed portion 41, the airbag cover of the second embodiment is also formed of only the foamed resin molded body without using the base or the skin material. When the airbag is deployed, it breaks at the intended tear line portion 20.

(Example 3)
The airbag cover of the third embodiment differs from the airbag cover of the first embodiment in the shape of the tear line portion. The method for manufacturing the airbag cover of the third embodiment includes a foaming step and a molding step instead of the foaming step. FIG. 7 is an explanatory diagram schematically illustrating the appearance of the airbag cover of the third embodiment. FIG. 8 is a schematic diagram illustrating a state in which the airbag cover of the third embodiment is cut at the position AA in FIG. 7. FIG. 9 to 11 are explanatory diagrams schematically showing a method of manufacturing the airbag cover of the third embodiment. Specifically, FIG. 9 shows an intermediate between the cavity and the airbag cover in the injection step, FIG. 10 shows an intermediate between the cavity and the airbag cover in the foaming step, and FIG. Represents the body.

  As shown in FIG. 7, in the airbag cover 1 according to the third embodiment, the tear line portion 20 has a substantially H shape and is provided inside the peripheral portion of the cover portion 2. Therefore, in the airbag cover 1 according to the third embodiment, most of the boundary between the cover 2 and the base 3 is constituted by the general cover 21, and the tear line 20 divides the general cover 21 into four parts. ing. When the airbag is deployed, the tear line portion 20 is broken, and the breakage of the tear line portion 20 divides the general cover portion 21 into four portions. Deform to bend up. Therefore, in the airbag cover 1 of the third embodiment, the opening through which the airbag passes when the airbag is deployed is formed in the cover portion 2 itself.

  As shown in FIG. 8, the general cover portion 21 includes a foamed portion 40 and a non-foamed portion 41. The tear line portion 20 is constituted by a thin non-foamed portion 41. Although not shown, the base 3 also includes a foamed portion 40 and a non-foamed portion 41. Therefore, the airbag cover 1 of the third embodiment also breaks at the tear line portion 20 despite being formed only of the foamed resin molded body. As shown in FIG. 8, the tear line portion 20 is formed with a groove-shaped fracture starting point portion 20 a. The fracture starting point portion 20a is molded in a molding step as described later. The rupture starting point portion 20a is a starting point when the tear line portion 20 breaks. Note that the fracture starting point portion 20a may be formed continuously over the entire length of the tear line portion 20 or may be formed intermittently.

  In the airbag cover 1 according to the third embodiment, the thickness of the general cover 21 and the thickness of the base 3 are substantially constant, and there is no step at the boundary between the general cover 21 and the base 3. A thinner portion than the general cover 21 and the base 3 may be provided at the boundary between the base 21 and the base 3. The thin portion may be configured by the general cover portion 21 or the base portion 3. In any case, by providing the thin portion, the general cover portion 21 can be easily deformed when the airbag is deployed, that is, when the tear line portion 20 is broken. The thin portion at the boundary between the general cover portion 21 and the base 3 is preferably thicker than the tear line portion 20, and more preferably has a thickness exceeding 1 mm. This is to prevent the thin portion from being broken when the airbag is deployed.

  The airbag cover 1 according to the third embodiment is manufactured through a preparation process, an injection process, a pressure-holding process, a foaming process, and a molding process using a molding die 6 including a first mold 61 and a second mold 62. . Since the preparation step, the injection step, and the pressure-holding step are substantially the same as those of the method for manufacturing the airbag cover of the first embodiment, in the third embodiment, only the foaming step and the molding step will be described.

  As shown in FIG. 9, the molding die 6 used in the method for manufacturing the airbag cover of the third embodiment includes a first die 61 which is a fixed die and a second die 62 which is a movable die. The second mold 62 is composed of a general movable mold part 70 and a core part 71, and the mold surface of the first mold 61 and the mold surface of the core part 71 are similar to the molding mold in the method of manufacturing the airbag cover of the first embodiment. The tear line cavity 82 is partitioned, and the general cover cavity 81 and the base cavity 83 are partitioned by the mold surface of the first mold 61, the mold surface of the general movable mold part 70, and the mold surface of the core part 71.

(Foaming process)
In the foaming step, the position of the first mold 61 is not changed after the pressure holding step, and the position of the general movable mold part 70 and the core part 71 of the second mold 62 is changed in the mold opening direction indicated by the arrow in FIG. By doing so, the thickness of the tear line cavity 82, the base cavity 83, and the general cover cavity 81 increases, and the fluid foam resin material 85 in the tear line cavity 82, the base cavity 83, and the general cover cavity 81 foams. .

(Molding process)
As shown in FIG. 11, in the molding process, after the foaming process, that is, after the foamed resin material 85 foams in the tear line cavity 82, the base cavity 83, and the general cover cavity 81, the base cavity 83 and the general cover cavity 81 The thickness of the tear line cavity 82 is reduced while keeping the thickness. Specifically, only the core 71 of the second mold 62 is moved in the mold clamping direction indicated by an arrow in FIG. 11 without changing the position of the general movable mold 70 of the first mold 61 and the second mold 62.

  In the foaming step, the foamed resin material 85 foams in the tear line cavity 82, the base cavity 83, and the general cover cavity 81 to generate the pores 50. However, by reducing the thickness of the tear line cavity 82, the pores 50 are reduced. Disappears. By cooling and solidifying the foamed resin material 85 in this state, the tear line portion 20 formed by the tear line cavity 82 can be constituted only by the non-foamed portion 41. A projection 71a is provided on the mold surface of the core 71 constituting the tear line cavity 82. The tear line portion 20 is molded into the tear line portion 20 by the convex ridge 71a.

  The airbag cover 1 manufactured by the method of manufacturing the airbag cover of the third embodiment is also lightweight, and is formed of only the foamed resin molded body. Break.

  In the method of manufacturing the airbag cover of the third embodiment, the thickness of the general cover cavity 81 is kept as it is in the molding step. However, if necessary, the thickness of the general cover cavity 81 together with the tear line cavity 82 is formed in the molding step. May be reduced. By doing so, the general cover portion 21 can be constituted by the non-foamed portion 41. In this case, it is preferable that the thickness of the general cover cavity 81 is larger than the thickness of the tear line cavity 82. That is, the general cover portion 21 is preferably thicker than the tear line portion 20. This is for avoiding breakage of the general cover portion 21 when the airbag is deployed. Specifically, the thickness of the general cover cavity 81 preferably exceeds 1 mm.

(Other)
The present invention is not limited to the embodiment described above and shown in the drawings, and can be implemented with appropriate modifications without departing from the scope of the invention. The components shown in the embodiments can be arbitrarily extracted and combined.

The airbag cover of the present invention can be expressed as follows.
(1) A resin airbag cover 1 for covering an airbag,
A cover portion, a base portion surrounding the cover portion, and a tear line portion provided on the cover portion;
The tear line portion 20 is thinner than the base portion 3 and includes a non-foamed portion 41,
The airbag cover, wherein the base 3 includes the non-foamed portion 41 and the foamed portion 40.
(2) The airbag cover according to (1), wherein the foamed portion 40 has pores 50 having a pore size of 10 μm or more, and the non-foamed portion 41 does not have pores 50 having a pore size of 1 μm or more.

The method for manufacturing an airbag cover of the present invention can be expressed as follows.
(3) The foamed resin material 85 is injected into the cavity 8 formed between the first mold 61 and the second mold 62 to cover the cover 2, the base 3 surrounding the cover 2, and the cover 2. And a tear line portion 20 provided in the airbag cover 1, comprising:
The cavity 8 includes a tear line cavity 82 forming the tear line portion 20, a general cover cavity 81 forming the cover portion 2 other than the tear line portion 20, and a base cavity 83 forming the base portion 3. And
A method for manufacturing an airbag cover, wherein after the foamed resin material 85 is injected into the cavity 8, the thickness of the base cavity 83 is increased while the thickness of the tear line cavity 82 is maintained.

Another embodiment of the method for manufacturing an airbag cover of the present invention can be expressed as follows.
(4) The foamed resin material 85 is injected into the cavity 8 formed between the first mold 61 and the second mold 62 to cover the cover 2, the base 3 surrounding the cover 2, and the cover 2. And a tear line portion 20 provided in the airbag cover 1, comprising:
The cavity 8 includes a tear line cavity 82 forming the tear line portion 20, a general cover cavity 81 forming the cover portion 2 other than the tear line portion 20, and a base cavity 83 forming the base portion 3. And
After injecting the foamed resin material 85 into the cavity 8,
First, the thickness of the tear line cavity 82, the thickness of the general cover cavity 81, and the thickness of the base cavity 83 are increased,
Next, a method of manufacturing an airbag cover, wherein the thickness of the tear line cavity 82 is reduced while the thickness of the base cavity 83 is maintained.

1: airbag cover 2: cover part 20: tear line part 21: general cover part 3: base part 41: non-foamed part 40: foamed part 50: pore 61: first type 62: second type 8: cavity 81: general Cover cavity 82: tear line cavity 83: base cavity 85: foam resin material

Claims (2)

A foam resin material is injected into a cavity formed between the first mold and the second mold to have a cover, a base surrounding the cover, and a tear line provided in the cover. A method of manufacturing an airbag cover, comprising:
The cavity is configured by a tear line cavity forming the tear line portion, a general cover cavity forming the cover portion other than the tear line portion, and a base cavity forming the base portion,
A method for manufacturing an airbag cover, comprising: increasing the thickness of the base cavity while maintaining the thickness of the tear line cavity after injecting the foamed resin material into the cavity. A foam resin material is injected into a cavity formed between the first mold and the second mold to have a cover, a base surrounding the cover, and a tear line provided in the cover. A method of manufacturing an airbag cover, comprising:
The cavity is configured by a tear line cavity forming the tear line portion, a general cover cavity forming the cover portion other than the tear line portion, and a base cavity forming the base portion,
After injecting the foamed resin material into the cavity,
First, increasing the thickness of the tear line cavity, the thickness of the general cover cavity, and the thickness of the base cavity,
Next, a method of manufacturing an airbag cover, wherein the thickness of the tear line cavity is reduced while maintaining the thickness of the base cavity.

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