JP4230625B2 - Assist grip and manufacturing method thereof - Google Patents

Description

[0001]
BACKGROUND OF THE INVENTION
The present invention relates to an assist grip that is attached to a ceiling of a car, for example, a roof trim, and supports a body by being gripped by an occupant, and a method for manufacturing the same.
[0002]
[Prior art]
Conventionally, an assist grip has a known structure in which the surface of a core core material made of a hard thermoplastic resin is encapsulated with a skin material made of a soft resin such as soft PVC (for example, Japanese Patent Laid-Open No. 8-11611). . The assist grip having such a structure is formed by an insert molding method in which a core core material is inserted into an injection mold and a soft resin is injected and filled into the mold.
[0003]
As another structure, an assist grip having a hollow body structure using a gas injection method is also known (for example, JP-A-6-270183). This is because the skin is set on the wall of the cavity, the mold is closed, the resin in a softened state is injected into the cavity, and the softened resin is inflated from the inside by injecting nitrogen gas or the like into the cavity to adhere to the skin. Is.
[0004]
[Problems to be solved by the invention]
From the viewpoint of occupant protection, this type of vehicle's assist grip does not give a high impact to the human body when it collides with the human body due to a collision, etc., does not scatter debris even if it is damaged, and does not have a sharp edge Is required. However, in the structure described supra Publication (JP-A-8-11611), a core core when formed by a hard resin, which is output thrust from the skin material becomes sharp edges broken by collision or the like, passenger Cause injuries. Further, as described in the above-mentioned publication, there is a problem that countermeasures against molding defects such as sink marks are necessary.
[0005]
On the other hand, when molding is performed using the gas injection method, appearance defects such as silver are likely to occur and the defect rate tends to be higher than in a normal injection molding method. In addition, this molding method generally has a problem of high cost.
[0006]
The present invention has been made in view of such circumstances, and provides an assist grip that is not easily damaged even when subjected to an impact, and that is unlikely to have a sharp edge even if it is damaged.
[0007]
The present invention also provides a method of manufacturing an assist grip that is less likely to cause poor appearance.
[0008]
[Means for Solving the Problems]
The present invention (Claim 1) is an assist grip attached to a ceiling or the like of an automobile, and is made of a material obtained by mixing a base material made of a thermoplastic resin, a modifier for adjusting a flexural modulus, and a foam material. Is. In such a configuration, the assist grip molded from the above-mentioned mixed material has a bending elastic modulus reduced by the modifying material, an impact absorption relaxation efficiency is improved, and a sharp edge is hardly formed even if it is damaged. The base material is in the range of 69 to 79.95% by weight, the modifier is in the range of 20 to 30% by weight, and the foaming material is in the range of 0.05 to 1.0% by weight. It is a mixture. In such a configuration, a bending elastic modulus suitable for shock absorption and relaxation can be obtained, and a molded body that is not easily broken can be obtained. In addition, it is difficult to form a sharp edge even if it is damaged. At the same time, the bending elastic modulus of the molded body made of the mixed material is set in the range of 700 to 1000 MPa. If the bending elastic modulus is in such a range, it will not be deformed even if the occupant pulls strongly, and elasticity that absorbs and relaxes the impact can be obtained.
[0009]
In the present invention (Claim 2), the base material is made of polypropylene resin, and the modifier is ethylene propylene rubber, butyl rubber, ethylene butene rubber, polyethylene resin, polyolefin-based thermoplastic elastomer or these. And the foaming material is made of any of sodium hydrogen carbonate, azodicarponamide, N, N′-dinitrosopentamethylenetetramine, 4,4′-oxybis (benzenesulfonylhydrazide) or a mixture thereof. Is. In such a configuration, an appropriate bending elastic modulus is obtained by the modifying material, and a porous structure is obtained by the foamed material.
[0012]
According to the present invention (Claim 5), there is provided a manufacturing method of an assist grip attached to a ceiling or the like of an automobile, wherein a base material in the range of 69 to 79.95% by weight mainly composed of polypropylene resin is subjected to bending elasticity. Mixing the modifier in the range of 20 to 30% by weight to adjust the rate and the foaming material in the range of 0.05 to 1.0% by weight for foaming the base material and the modifier during molding, heating The molded product made of the mixed material has a bending elastic modulus in the range of 700 to 1000 MPa by melting and injecting into the mold having the assist grip-shaped cavity and molding the foamed material. set in such a shall. In such a configuration, the pressure in the mold rises due to the foaming of the foam during molding, thereby suppressing appearance defects such as sink marks in the molded body.
[0013]
DETAILED DESCRIPTION OF THE INVENTION
1 to 3, reference numeral 1 denotes an assist grip, which is attached to the ceiling of an automobile, for example, both sides of the roof trim 2, and is held by the occupant with one hand. The assist grip 1 has an elongated and curved shape, and a cavity 3 and a cap 4 covering the cavity 3 are formed at both ends. A screw hole 5 is formed in the cavity 3, and a bolt 6 is inserted into the hole 3 and is screwed to the roof trim 2 with a nut 8 via a spacer 7. The cap 4 is formed integrally with the assist grip 1, and its boundary is formed thinly to form a hinge structure 9. Reference numeral 10 denotes a pair of engaging protrusions formed on the inner surface of the cap 4. The cap is rotated in the direction of arrow a in the figure to engage the inside of the cavity 3 and fix the cap 4.
[0014]
The assist grip 1 is obtained by injection molding a material in which a thermoplastic resin, preferably a polypropylene resin is used as a base material, and a modifier and a foaming material are mixed with the base material. Ethylene propylene rubber can be used as the modifying material, and baking soda can be used as the foaming material.
[0015]
The modifier made of ethylene propylene rubber serves to lower the flexural modulus. That is, the polypropylene resin itself has a high flexural modulus, and therefore, it is easy to bend when an impact is applied, and when it is folded, the tip becomes a sharp edge, which is dangerous for the occupant. Such physical properties are unsuitable for automobile interior members that may cause a collision. The modifier improves such physical properties and is mixed in the range of 20 to 30% by weight with respect to the entire mixed material. Thus, the flexural modulus is set in the range of 700 to 1000 MPa. If the flexural modulus is less than 700 MPa, the softness is too soft, and there is a risk of plastic deformation when the occupant pulls with a strong force, or the nut 8 tends to loosen due to the softness. On the other hand, if the flexural modulus exceeds 1000 MPa, it becomes hard and brittle, and there is a danger that the occupant will easily come in contact with it and be injured when subjected to an impact.
[0016]
In addition to the ethylene propylene rubber, butyl rubber, ethylene butene rubber, polyethylene resin, and polyolefin-based thermoplastic elastomer can be used as the modifier, and these are used alone or in combination. Polyolefin thermoplastic elastomers are, for example, polyethylene resins mixed with ethylene propylene rubber and EPDM as soft materials to make elastomers, polyethylene resins mixed with butyl rubber as soft materials to make elastomers, and similarly polypropylene resins In addition, an elastomer obtained by mixing ethylene propylene rubber and EPDM as a soft material, and an elastomer obtained by mixing butyl rubber as a soft material in a polypropylene resin can be used.
[0017]
The foamed material is used by being mixed with a carrier resin such as a low density polyethylene resin in order to uniformly disperse the base material. The mixing ratio is about 95% by weight for the low density polyethylene resin and about 5% by weight for the baking soda. is there. If it is this ratio, powdered baking soda will disperse | distribute uniformly to a pellet-like low density polyethylene resin. A small amount of a foaming aid made of citric acid or the like is added to this mixture in order to adjust its thermal decomposition temperature, that is, to match the molding temperature. This is because the foam material alone has a high decomposition temperature and does not conform to the foam molding conditions. In such a configuration, the baking soda is mixed in the range of 0.05 to 1.0% by weight. If it is less than 0.05% by weight, foaming becomes insufficient, the molded product becomes hard, and molding defects such as sink marks increase. On the other hand, if the amount is more than 1.0% by weight, excessive foaming may occur and the molded body may expand and deform. The foamed material is thermally decomposed by heating at the time of molding to generate a gas, and fine bubbles are formed inside the molded body to form a porous structure.
[0018]
In addition to the above baking soda, azodicarponamide, N, N-dinitrosopentamethylenetetramine, and 4,4′-oxybis (benzenesulfonylhydrazide) can be used as the foaming material. In addition to the citric acid, urea compounds and zinc compounds can be used as foaming aids. As a result of the modifier and the foaming material being mixed in the above range, the polypropylene resin and carrier resin as the base material are used in the range of 69 to 79.95% by weight.
[0019]
【Example】
Polypropylene resin 75% by weight, ethylene propylene rubber 23% by weight, baking soda 0.1% by weight, low density polyethylene resin 1.9% by weight as a baking soda carrier resin, mixed in pellet form, heated and melted at 220 ° C Then, an assist grip was formed by injection molding. Baking soda is mixed in advance with low density polyethylene resin pellets and dispersed, and then mixed with polypropylene resin and ethylene propylene resin pellets. The assist grip obtained after the injection molding had a bending elastic modulus of 780 MPa and a foaming ratio of 7%. This assist grip molded body has a skin layer formed on the surface at the time of molding, and air bubbles do not appear on the surface. This molded body can be attached to an automobile as a finished assist grip product. It was also confirmed that the occurrence of sink marks was prevented by the expansion of the foam material during molding. When an impact is applied, the assist grip having the above structure bends due to its elasticity, absorbs and relaxes the impact, and hardly breaks. Even when it breaks due to an extreme impact, its tip is unlikely to be a sharp edge, and it has been confirmed that there is little risk of piercing the skin even if it touches the occupant's body. Note that with the foaming ratio as described above, the touch when touched by a person is in the range where a hard feeling is obtained, and it is said that elasticity is generated by foaming, but when a strong force is applied such as at the time of collision For the first time, the elastic action is exhibited.
[0020]
【The invention's effect】
According to the present invention (Claim 1), the flexural modulus is set in consideration of the magnitude of the force pulled by the occupant and the impact force applied to the occupant during a car collision. In other words, it is set so that it is not deformed by a force that is normally pulled by the occupant, but elastically deformed with respect to a large impact force applied at the time of a collision or the like, so that when the vehicle collides with a human body, the impact can be absorbed and reduced . Further, by adopting a porous structure, even when damaged due to impact, the tip is unlikely to have a sharp edge, and the possibility of damaging the human body can be kept low. Specifically, the substrate is in the range of 69 to 79.95% by weight, the modifier is in the range of 20 to 30% by weight, and the foam is in the range of 0.05 to 1.0% by weight. Since they are mixed, a bending elastic modulus suitable for shock absorption and relaxation can be obtained, and a molded body that is difficult to break can be obtained. In addition, since the flexural modulus of the molded body is set in the range of 700 to 1000 MPa, it does not deform even when the occupant pulls strongly, and elasticity that absorbs and relaxes the impact is obtained.
[0021]
According to the present invention (Claim 2), the base material is made of polypropylene resin, and the modifying material and the foaming material are also easy to mix with the base material, so that it is easy to mold and therefore the defect rate is reduced. Can do. Further, the action of the modifying material and the foamed material can realize an assist grip having a porous structure that is not easily broken and that efficiently absorbs and reduces shock.
[0024]
According to the present invention (Claim 5), during the injection molding, the foaming material is foamed and the pressure to expand is applied, so that molding defects such as sink marks, which are likely to occur in the injection molding method, are prevented, and the product walks. Can be improved.
[Brief description of the drawings]
FIG. 1 is a perspective view of an assist grip according to an embodiment of the present invention.
2 is a cross-sectional view taken along line II-II in FIG.
3 is a cross-sectional view taken along line III-III in FIG.
[Explanation of symbols]
DESCRIPTION OF SYMBOLS 1 Assist grip 2 Roof trim 3 Cavity 4 Cap 5 Screw hole 6 Bolt 7 Spacer 8 Nut 9 Hinge structure 10 Engagement protrusion

Claims (3)

A assist grip is attached to the ceiling of an automobile, a substrate made of a thermoplastic resin, a modifier for adjusting the flexural modulus, Ri name of a material obtained by mixing a foaming material,
The base material is mixed in the range of 69 to 79.95% by weight, the modifier is mixed in the range of 20 to 30% by weight, and the foaming material is mixed in the range of 0.05 to 1.0% by weight. And
The mixed molded product of the bending assist grip modulus ing been set to 700 to the range of 1000MPa made of material.   The base material is made of polypropylene resin, the modifier is made of ethylene propylene rubber, butyl rubber, ethylene butene rubber, polyethylene resin, polyolefin-based thermoplastic elastomer or a mixture thereof, and the foam material is sodium hydrogen carbonate. , An azodicarbonamide, N, N′-dinitrosopentamethylenetetramine, 4,4′-oxybis (benzenesulfonylhydrazide), or a mixture thereof. A method of manufacturing an assist grip attached to a ceiling or the like of an automobile, wherein a base material in a range of 69 to 79.95% by weight mainly composed of polypropylene resin is applied to a base material in a range of 20 to 30% by weight to adjust a flexural modulus . A gold having an assist grip-shaped cavity by mixing a reforming material with a foaming material in the range of 0.05 to 1.0% by weight for foaming the base material and the reforming material at the time of molding. molded while by injection injected into the mold by foaming the foam material, the mixed flexural modulus of made of a material molded body 700 to the production method of the assist grip ing is set in a range of 1000 MPa.

Images