JP4918820B2 - Tearline break control method and airbag door tearline - Google Patents

Description

  The present invention relates to a tear line break control method and a tear line for an airbag door. More particularly, the present invention relates to a tear line break control method for breaking a tear (surface) of an airbag door integrally provided on an instrument panel in a desired and suitable pattern when the airbag is deployed. The present invention relates to a tear line for airbag doors, which is one of the excellent embodiments of this method.

  When an airbag device for a passenger seat is provided in an automobile, the airbag device is generally attached to the back side of the instrument panel. Therefore, an airbag door composed of a pair of doors is usually set in the corresponding portion of the instrument panel. The airbag door is formed by a tear line that is tiered so as to be quickly broken by the inflation pressure when the airbag is deployed.

  The instrument panel is a laminated structure of a base layer on the back side and a skin layer on the front side (vehicle compartment side). The base layer may be composed of only a base material layer made of a thermoplastic resin or the like, but in many cases, it is composed of a two-layer structure of a base material layer and a foam material layer in contact with the skin layer. The tear process is essentially a process to be performed on the skin layer in consideration of the fracture of the skin layer when the airbag is deployed. However, on the other hand, from the viewpoint of appearance, the tier processing or its trace is required to be invisible (not visible when viewed from the passenger compartment side). Therefore, the tearing process involves the following technical difficulties.

  That is, the tiering must not be exposed on the skin layer side, but must be performed from the base layer side (the back side of the instrument panel). Moreover, in order to ensure the breaking performance when deploying an airbag, a tearing process that reaches from the base layer to the thick part of the skin layer is required, but too much importance is attached to the breaking performance, and excessive tearing is applied to the thin skin layer. When the processing is performed, there is a difficulty that the trace of the tier processing is raised as unevenness on the surface side of the instrument panel and becomes visible. Furthermore, although it was invisible immediately after tearing, it became gradually visible after the actual vehicle was mounted due to the effects of the high-temperature environment in the passenger compartment. In some cases. Such visible phenomenon called “thermal strain” should be avoided. After all, unless the cutting pattern or cutting pattern of the tier processing is optimal, there has been a technical difficulty that the tear line skin breaking performance, invisibility, thermal distortion, etc. are greatly affected.

  On the other hand, regarding a general tear processing method for an instrument panel, conventionally, a desired tear processing is performed on the back side of the skin layer in advance, and then this skin layer is directly bonded to the base material layer, or this skin layer There is also a method of forming a foam material layer by performing urethane injection foaming or the like between the base material layer and the base material layer. However, in recent years, a so-called concave vacuum forming method has been used. This method is a process of vacuum forming the skin layer and the foam material layer and simultaneously press-molding them to the base material layer. Therefore, in the process, after forming the three-layer laminated structure, the skin layer is formed from the base material layer side. It is necessary to perform accurate tearing at a depth that reaches the layer, and it is more difficult to perform good tearing on the skin layer that is a thin layer.

JP-A-2003-212075 discloses a tear line structure set in a shape along a pair of doors of an airbag door. This tear line is created by intermittently forming dotted holes (dot cuts) having a depth reaching from the back side of the instrument panel to the vicinity of the epidermis in a broken line shape.

  From the description of paragraph “0023” in the specification of Patent Document 1 and the contents of FIGS. 3 and 4, it is considered that the base material 2 is provided with a groove-like notch along the tear line. It is done. Furthermore, there is a disclosure of a removal portion 11 in which the foamed resin layer 3 is removed to about half of its wall pressure.

Japanese Patent Laid-Open No. 2005-96705 discloses an air bag tear line forming apparatus and a forming method. As described in the abstract, the present invention is intended to accurately control the processing of thin-walled members using an end mill, with the aim of being applied to those requiring strict thickness control such as instrument panel airbag tear lines. It is something to try.

  As shown in FIG. 1 of Patent Document 2, a tear line having substantially the same shape as that disclosed in Patent Document 1 is assumed. There is no disclosure regarding the variability in tearing cut form and / or cut frequency in each part.

  By the way, according to the above-mentioned technical difficulty of tiering, according to the research of the present inventor, the tear line for airbag doors formed on the instrument panel depends on the contents of tiering in each part of the tier line. The pattern of surface (skin) breakage when the airbag is deployed changes greatly. If the skin breaking pattern is inappropriate, for example, the following problems may occur.

  a) It is difficult to ensure breakage of the side lines on both sides corresponding to both side ends of the pair of doors constituting the airbag door.

  b) As another obstacle, since the base material layer and the like are not ruptured clearly, burrs or the like are formed at the ruptured portion, which may damage the deployed airbag.

  The conventional techniques such as Patent Document 1 and Patent Document 2 described above do not pose any problems with respect to these points, and, of course, do not disclose or suggest solutions for such problems. In Patent Document 1, the base material 2 is only provided with a uniform groove-shaped cut along the tear line, and the removal portion 11 is also provided only in the setting portion of the leakage preventing member 8, None of them is a configuration for controlling the tear line skin breaking pattern. In Patent Document 2, the tiered holes are simply arranged in parallel.

Accordingly, the present invention provides a tear line break control method for breaking a tear line of an airbag door in a desired pattern when the airbag is deployed, and a suitable airbag door tear line as an embodiment of this method. Providing is a technical issue to be solved.
〔Viewpoints〕

  The inventor of the present application prototyped tear lines for airbag doors having various cut forms, and repeated the breaking experiments, and as a result, obtained the following findings 1) to 4).

  1) There is a very preferable skin breaking pattern that does not cause the above problems a) and b) when the airbag is deployed.

  2) By making a predetermined relative difference in the skin breaking strength of each part of the tear line, it is possible to control the above-mentioned extremely preferable skin breaking pattern.

  3) In order to make a relative difference in the skin breaking strength of each part of the tear line, it is effective to select at least one of the cutting form and the cutting frequency of the tearing process in each part of the tear line.

  4) As a cut form of tear processing, a long hole-like linear cut part provided intermittently at a depth reaching the vicinity of the skin layer in the base layer, and a thick part of the skin layer passing through the base layer It is effective to use in combination with a dot cut that is a point-like cut portion that reaches.

  The present invention has been completed on the basis of these findings. The eye of the present invention is that “in the formation of a tear line, not just tearing for the purpose of breaking, but also for the purpose of controlling the breaking pattern. It is in the point of applying a tier process with changeability.

(First invention)
The configuration of the first invention of the present application for solving the above-mentioned problems is by selecting at least one of the cut form and the cut frequency of the tear processing in each part of the airbag door tear line set in the instrument panel for automobiles, It is a tear line break control method that performs relative differentiation on the surface break strength of each portion of the tear line, and controls the surface break order and the break form of each portion of the tear line when the airbag is deployed.

  In the first aspect of the present invention, “surface rupture” means, as will be described later, that the rupture to the surface is premised on the rupture of the entire tiered portion of the panel, and only the surface portion in the tiered portion is ruptured. It may mean that. In addition, since a skin layer usually exists in the tiered portion, “surface fracture” also means “skin fracture”. The “rupture form” means a break form of each layer of the instrument panel including the skin layer.

  According to the first aspect of the present invention, the surface break strength of each part of the tear line is relatively differentiated, so that the order of the surface break and the form of break of each part of the tear line when the airbag is deployed can be controlled. Further, since the means for making a relative difference in the surface breaking strength of each part of the tear line is selection of at least one of the cutting form and the cutting frequency of the tearing process in each part of the tear line, the tear line breaking control described above is performed. Can be performed reliably.

  The inventor of the present application, in this technical field, includes at least one of the cut form and the cut frequency according to each part of the airbag door tear line formed on the vehicle instrument panel, including Patent Document 1 and Patent Document 2 described above. However, there is no document that discloses or suggests the technical idea that the tear line is subjected to different tiering, thereby controlling the tear line surface rupture order and rupture form during airbag deployment.

(Second invention)
The structure of the second invention of the present application for solving the above-described problem is that when the tear line according to the first invention is formed on the instrument panel for automobiles, which is a laminated structure including a base layer and a skin layer, It is a tear line break control method in which choices of a cutting form and a cutting frequency of processing are as described in the following (1) to (3).

  (1) The above-mentioned tear processing cut form options include a linear cut portion provided intermittently at a depth reaching the portion near the skin layer in the base layer, and a thick portion of the skin layer passing through the base layer. And a dot cut which is a dot-like cut portion.

  (2) In the dot cut, a dot cut provided at the bottom of the linear cut part and a dot provided so as to reach from the base layer to the thick part of the skin layer in a part where the linear cut part is not set Including cuts.

  (3) The options for the cutting frequency of the tiering are the length of the linear cut portions, the mutual interval between the linear cut portions, and the bottom of the linear cut portion or the portion where the linear cut portion is not set. And the mutual interval of the provided dot cuts.

  According to the 2nd invention, the choice of the cutting form of the tear processing in the said 1st invention or a cutting frequency is provided.

  As described above, the options for the cut form include a linear cut portion and a dot cut provided intermittently. The dot cut includes a dot cut provided at the bottom of the linear cut portion and a dot cut that reaches the thick portion of the skin layer through the base layer in a portion where the linear cut portion is not set.

  Generally, as described in Patent Document 1, for example, the linear cut portion is formed into a groove shape or provided with a depth reaching the thick portion of the skin layer. Although the strength can be sufficiently reduced, it has been found that the adverse effects of thermal distortion are also great. However, according to the dot cut, it is possible to weaken the skin breaking strength and to effectively avoid thermal distortion.

  Therefore, a combination of a linear cut part provided intermittently at a depth that reaches the vicinity of the skin layer in the base layer and a dot cut that is a dotted cut part that passes through the base layer and reaches the thick part of the skin layer This is extremely effective for the purpose of weakening the tear strength of the tear line while effectively avoiding thermal distortion.

  Options for the cut frequency include the length of the linear cut portions, the mutual interval between the linear cut portions, and the mutual interval between the two types of dot cuts. Various combinations of the three types of cut forms and the formation cut frequencies thereof enable various differences in the surface breaking strength of each part of the tear line.

(Third invention)
The configuration of the third invention of the present application for solving the above problem is that when the base layer according to the first invention or the second invention is composed of a base material layer and a foam material layer, the linear cut portion passes through the base material layer. Then, the tear line breakage control method is provided at a depth reaching the portion near the skin layer in the foam layer.

  The instrument panel is basically composed of a base layer and a skin layer, and the base layer may be composed of only a base material layer made of a thermoplastic resin such as polypropylene, or may be composed of a base material layer and a foam material layer. is there. In the latter case, as in the third invention, the linear cut portion is provided at a depth that reaches the portion near the skin layer in the foam material layer through the base material layer. In addition, when a base layer consists of a base material layer and a foam material layer, an adhesive layer may exist between these both layers.

(Fourth invention)
The configuration of the fourth invention of the present application for solving the above problems is a tear line in which the tear line according to any one of the first to third inventions is formed in a shape along a pair of doors of an airbag door. In addition, the center line corresponding to the boundary line of the pair of doors is provided with an extension portion that is further extended on both sides from the intersection with the side lines on both sides corresponding to both side ends of the pair of doors. This is a tear line breaking control method.

  As a means for controlling the surface breaking order and the breaking mode of each part of the tear line, in addition to the selection of at least one of the cutting form and cutting frequency of the tearing process in each part, the overall shape of the tear line is a new one as in the fourth invention. The shape is also important.

  That is, there is a problem in that it is difficult to ensure breakage of the side line as described above as a defect of “a)” when the tear line skin breaks. If the breakage of the side line is not ensured, the pair of airbag doors may not be opened sufficiently, which may hinder sufficient deployment of the airbag. By further extending the center line in the tear line from the intersection with the side line, it is possible to break the extended portion in the center line when the airbag is deployed, and to suppress the stretching of the skin of this portion. As a result, the skins on both sides sandwiching the side line are pulled, and it is possible to ensure breakage of the side line.

(Fifth invention)
The configuration of the fifth invention of the present application for solving the above-mentioned problem is a dot cut that is a point-like cut portion that passes through the base layer and reaches the thick portion of the skin layer at the extension of the center line according to the fourth invention On the other hand, the center line and the side line excluding the extension are intermittently provided with a linear cut portion having a depth reaching the vicinity of the skin layer in the base layer and the bottom of the linear cut portion and the linear shape. An extension of the center line when deploying an airbag by providing a dot cut that is a dotted cut that passes through the base layer and reaches the thick part of the skin layer on at least one of the part where the cut part is not set And a tear line break control method that provides a difference in the break strength of the base layer from the center line and the side line excluding the extension.

  As in the fourth aspect, it is important to provide a center line extension portion and to make the skin break to the center line extension portion when the tear line skin breaks. However, at that time, the portion other than the centerline extension in the tear line is scheduled to break to the base layer, but only the skin breakage should occur in the centerline extension, and the base layer breaks in the extension. For example, it is preferable to avoid breaking the base layer for reasons such as preventing the airbag from being damaged. According to the fifth invention, when the airbag is deployed, the portion other than the centerline extension in the tear line breaks to the base layer when the skin breaks, but only the skin break occurs in the centerline extension, and the base layer breaks. do not do.

(Sixth invention)
The structure of the sixth invention of the present application for solving the above-mentioned problems is the center part of the center line in the tier line according to any of the first to fifth inventions, the intersection part of the center line with the side lines on both sides, and The surface break strength of the side lines on both sides is set to be relatively weak by the selection of the tear processing, and the surface break of the tear line at the time of deployment of the airbag is caused in the following order (1) to (3), Alternatively, it is a tear line break control method in which (2) and (3) are simultaneously caused after (1).

  (1) First, the center part of the center line breaks.

  (2) Fracture in a straight line until the entire center line reaches both ends. Here, the “entire center line” means to include the extension of the center line described in the fourth invention.

  (3) A pair of side lines breaks.

  According to various experiments by the inventor of the present application, the surface breakage strength of the specific part of the tear line is set to be relatively weak as in the sixth invention, and the surface breakage of the tear line is the above (1) to (3) If they are raised in order or (2) and (3) are raised simultaneously after (1), the above problems a) and b) can be solved satisfactorily. In other words, a quick and sufficient deployment mode of the airbag can be ensured, the side lines on both sides can be broken, and the base material layer can be clearly broken to form burrs that can interfere with the deployed airbag. Not.

(Seventh invention)
The structure of the seventh invention of the present application for solving the above problems is a tear line for an airbag door formed in a shape along a pair of doors of an airbag door by subjecting an instrument panel of an automobile to a tearing process. The center line corresponding to the boundary line of the pair of doors is provided with an extension portion further extended to both sides from the intersection with the side lines on both sides corresponding to both side ends of the pair of doors. It is a tear line for airbag doors.

  In the seventh invention, for example, with respect to the conventional general tear line shape as disclosed in FIG. 3 of Patent Document 2, the center line extends further from the intersection with the side lines on both sides to both sides. It has a characteristic tear line shape that is provided with an extended portion. As a result, the effect based on the centerline extension as described above is ensured.

(Eighth invention)
The configuration of the eighth invention of the present application for solving the above problem is a laminated structure in which the instrument panel according to the seventh invention is composed of a base layer and a skin layer, and the base layer is composed of only the base material layer, or It is a tear line for an airbag door, which is composed of a base material layer and a foam material layer.

  In general, an instrument panel is a laminated structure including at least a skin layer, and a portion other than the skin layer is referred to as a “base layer” in the present invention. Whatever the configuration of the base layer including the case of the eighth invention, the tear line for an airbag door of the present invention can be formed.

(9th invention)
The structure of the ninth invention of the present application for solving the above problems is a dot cut that is a dotted cut portion that passes through the base layer and reaches the thick part of the skin layer at the extension of the center line according to the eighth invention On the other hand, the center line and the side line excluding the extension are intermittently provided with a linear cut portion having a depth reaching the vicinity of the skin layer in the base layer and the bottom of the linear cut portion and the linear shape. The airbag door tier line is provided with a dot cut that is a dotted cut portion that passes through the base layer and reaches the thick portion of the skin layer on at least one of the portion where the cut portion is not set.

  According to the tear line for airbag doors of the ninth aspect of the invention, the actions and effects described with respect to the fifth aspect of the invention can be obtained.

(10th invention)
The structure of the tenth invention of the present application for solving the above-mentioned problem is that the linear cut portion has a depth that reaches the vicinity of the skin layer in the base layer over the entire tear line excluding the extension of the centerline according to the eighth invention. In addition, the center of the center line, the intersection with the side lines on both sides of the center line, and the side lines on both sides reach the thick part of the epidermis layer through the base layer It is the tear line for airbag doors which provided the dot cut which is a shape cut part.

  According to the tenth aspect of the present invention, since the linear cut portion is provided intermittently over the entire tier line as a basic tier process, and the specific portion is further provided with a dot cut. It is possible to cause tear line surface breaks in the ideal sequence described.

(11th invention)
The structure of the eleventh invention of the present application for solving the above-mentioned problems is that the center part of the centerline according to the tenth invention, the part in the vicinity of the intersection with the side lines on both sides of the centerline (excluding the extension part of the centerline) In addition, the airbag door tier line has the following dot cut setting conditions (4) to (6).

  (4) In any of the above portions, a dot cut is provided at least at the bottom of the linear cut portion.

  (5) In the center part of the center line and the side lines on both sides, the distance between the dot cuts provided at the bottom part of the linear cut part is small.

  (6) Further, in the side lines on both sides, dot cuts are also provided in portions where the linear cut portions are not set.

  According to the eleventh aspect of the present invention, the dot cut setting conditions at the specific portion in the tenth aspect are finely set as described in the above (4) to (6). The tear line surface breaks in the sequence can be caused particularly reliably.

  That is, in the eleventh aspect of the invention, the surface break strength of the side line is relatively weakest, then the surface break strength of the center portion of the center line is weak, and the surface of the portion near the intersection with the side lines on both sides of the center line The breaking strength is relatively strong. However, all of these portions are considerably weaker than the surface breaking strength of portions other than these portions in the tear line.

  Under such a relative difference in surface breaking strength, when the airbag is deployed, the fracture starts from the center of the center line that is first subjected to the deployment pressure of the airbag, and the center line as a whole It breaks in a straight line until it reaches. Also, the portion near the intersection with the side lines on both sides in the center line does not have a strong surface breaking strength as described above, and the side lines on both sides have the lowest surface breaking strength. Therefore, the breaking operation of the center line is smoothly converted into the breaking operation of the side line in a direction intersecting at a substantially right angle with the center line breaking operation. As a result, the tear line surface breakage in the ideal order described in the fifth aspect of the invention occurs particularly reliably.

(Twelfth invention)
The structure of the twelfth invention of the present application for solving the above problem is that when the base layer according to any of the ninth to eleventh inventions comprises a base material layer and a foam material layer, the linear cut portion is the base material. It is a tear line for airbag doors provided at a depth that passes through the layer and reaches a portion near the skin layer in the foam layer.

  As in the case of the third invention, when the base layer is composed of a base material layer and a foam material layer, the linear cut portion passes through the base material layer and is a portion near the skin layer in the foam material layer. It is provided at a depth reaching up to.

  By the above inventions of the present application, an ideal skin rupture pattern of the tear line at the time of airbag deployment is presented for the first time, and the relative difference in the surface rupture strength of each part of the tear line necessary to express the skin rupture pattern is shown. Specific methods and means are provided.

  Next, modes for carrying out the first invention to the twelfth invention of the present application will be described including the best mode.

[Tearline break control]
The present invention relates to controlling a surface fracture pattern of each part of a tear line in a tear line for an airbag door formed on an instrument panel for an automobile.

[Automotive instrument panel]
An automotive instrument panel is a laminated structure including a skin layer located on the front surface side (vehicle compartment side). A preferable application object is an instrument panel including the above-described skin layer and base layer. The base layer may be a single-layer base material layer made of a thermoplastic resin such as polypropylene, for example, or may be a laminated structure including such a base material layer. The laminated structure is composed of, for example, a base material layer and a foam material layer made of foamed polypropylene, foamed polyurethane, or the like and in contact with the skin layer. In this case, an adhesive layer may be provided between the base material layer and the foam material layer. In the laminated structure, an appropriate material layer may be provided in place of the foam material layer, and another material layer may be provided in addition to the base material layer and the foam material layer.

  In the case where the automotive instrument panel has any of the above-described configurations, the linear cut portion described later is provided at a depth that reaches the vicinity of the skin layer of the material layer in contact with the skin layer in the base layer. The cut is provided at a depth that passes through the entire base layer and reaches the thick part of the skin layer.

[Tearline shape]
In the present invention, the shape of the airbag door tear line is not limited. For example, as disclosed in FIG. 1 of Patent Document 1, a center line corresponding to a boundary line of a pair of doors of an airbag door, and side lines on both sides corresponding to both side ends of the pair of doors, An “H” -shaped tear line shape composed of a horizontal line corresponding to the upper and lower ends of a pair of doors (as parallel to the center line) is disclosed as disclosed in FIG. Also included are “day” shaped tear line shapes with directional lines. In short, all are included as long as the tear line shape is set corresponding to the set shape of the airbag door.

  However, as a preferable tear line shape peculiar to the present invention, there can be mentioned a tear line shape in which the center line is further provided with an extension portion that is further extended on both sides in a straight line from the intersection with the side lines on both sides. . In the tear line having such a shape, excellent effects as described above with respect to the fourth to sixth inventions can be obtained.

[Tear cut form]
One of the major features of the present invention is that, in order to make a relative difference in the surface breaking strength of each portion of the tear line, a plurality of options are provided for the cut form of tear processing in the tear line. Of the following first to third cut forms, two cut forms are preferably used in combination, and all cut forms are particularly preferably used in combination.

  A 1st cut form is the linear cut part provided intermittently in the depth which reaches the skin layer vicinity part in a base layer. The shape of the opening of the linear cut portion is a so-called long hole shape. The short diameter of the long hole may be defined by means of tearing (for example, an end mill), but is not particularly limited as long as the design needs are satisfied, and may be 1 mm, for example. The short diameter of the long hole need not be uniform in each part of the tear line.

  The second cut form is a dot cut provided at the bottom of the linear cut part. Hereinafter, this is also referred to as “bottom dot cut”. The dot cut is a dot-like (round hole shape, square hole shape, etc.) cut portion provided at a depth reaching the thick portion of the skin layer. The hole diameter of the dot cut is not limited, but may be set to be the same as the short diameter of the linear cut portion, for example. The hole shape and hole diameter of the dot cut need not be uniform in each part of the tear line.

  The 3rd cut form is a dot cut provided in the depth which reaches from the base layer to the thick part of an outer skin layer in the intermittent part of the linear cut part provided intermittently. Hereinafter, this is also referred to as “intermittent dot cut”. The hole diameter and hole shape for this form of dot cut are the same as in the case of the dot cut according to the second cut form.

  A 4th cut form is the dot cut provided in the depth which reaches from the base layer to the thick part of an outer skin layer in the part in which the linear cut part is not originally set. Hereinafter, this is also referred to as “independent dot cut”. The hole diameter and hole shape of this form of dot cut are the same as those of the dot cut according to the second cut form.

[Tear cutting frequency]
One of the other major features of the present invention is that the cutting frequency of tear processing in each part of the tear line is diversified in order to make a relative difference in the surface breaking strength of each part of the tear line. It is.

  More specifically, for example, the length (major diameter) of the linear cut portions, the mutual interval between the linear cut portions (the width of the intermittent portions of the linear cut portions provided intermittently), the above three types of dots It is the mutual interval (dot cut pitch) in the cut. The major axis of the linear cut portion can be appropriately designed as necessary, but can be, for example, about 4 mm, and does not need to be uniform in each portion of the tear line. Although the mutual space | interval of linear cut parts can be suitably designed as needed, it can be set, for example as about 6 mm, and does not need to be uniform in each part of a tear line.

  The formation of dot cuts and the setting of their mutual spacing have a great influence on the surface breaking strength of each part of the tear line. Therefore, a dot cut is not formed in a portion of the tear line where the surface breaking strength is not required to be relatively weak, and a dot cut is formed in a portion where the surface breaking strength is desired to be relatively weak. In particular parts such as the center part of the center line, the intersection of the center line with the side line on both sides, and the specific part such as the side line on both sides, the distance between the dot cuts may be reduced. preferable. However, if the mutual interval between the dot cuts is too small, the dot cuts are not practically connected to each other, and the surface breaking strength may be excessively weakened or the thermal distortion may be adversely affected. Therefore, for example, when the hole diameter of the dot cut is 1 mm, it is desirable that the mutual interval between the dot cuts is 0.5 mm or more, more preferably 1 mm.

  Furthermore, there is a case where it is desired to differentiate the relative surface breaking strength between the specific portions described above. In such a case, the dot cut provided at the bottom of the linear cut portion is used in combination with the dot cut provided at the intermittent portion of the linear cut portion, particularly in the portion where the surface breaking strength is desired to be weak, and the linear cut is provided in other portions. It is possible to design that a dot cut is provided only at the bottom of the cut part.

  On the other hand, regarding the effect on the breaking strength of the base layer, the influence of forming the linear cut portion is large, and the influence of the independent dot cut is small. Therefore, it is effective to provide only the independent dot cut without providing the linear cut portion for the portion of the tear line where it is desired to ensure the surface breakage but avoid the base layer breakage. An example of an extension of the center line can be given as an example of a tear line portion that causes such a request.

[Preferable tear line break pattern]
The suitable skin breaking pattern of the tear line to be realized by the tear line breaking control method according to the present invention is not particularly limited as long as the problems a) and b) described above are effectively eliminated.

  However, as long as it is based on the experimental results up to the present, various selections of the tier processing described above for the center line of the center line in the tear line, the intersection of the center line with the side lines on both sides, and the skin breaking strength of the side lines on both sides The tear line skin breakage at the time of deployment of the airbag is caused in the order of (1) to (3) below, or (2) and (3) are simultaneously performed after (1). The skin breaking pattern to be caused is suitable.

  (1) First, the center part of the center line breaks.

  (2) Fracture in a straight line until the entire center line reaches both ends.

  (3) A pair of side lines breaks.

  If the tear line of the airbag door tears with the above pattern, the skin will be properly ruptured, and a quick and sufficient deployment mode of the airbag can be realized. In addition, the base material layer or the like is ruptured clearly, and there is no fear of airbag damage due to formation of burrs or the like in the ruptured portion. Such a suitable skin breaking pattern can be realized particularly reliably in the airbag door tier line embodiments described below.

  In a more preferable tear line break pattern, the base layer breaks over the entire tear line except for the extension of the center line, with the above-mentioned skin break pattern secured, and the base layer extends at the center line extension. No breakage. This breaking pattern can be realized in the case of the fifth and ninth inventions.

[Preferred Embodiment of Tier Line for Airbag Door]
One particularly preferred embodiment of the airbag door tear line according to the present invention will be described. This embodiment relates to formation of a tear line for an air bag door that is set in a shape along a pair of doors of an air bag door by performing a tear process on an instrument panel of an automobile. However, there may be one or more other effective embodiments regarding the overall shape of the tear line, the selection of at least one of the cut form and the cut frequency of the tear process in each part of the tear line, and the like.

  In this embodiment, the instrument panel includes a base layer and a skin layer, and the base layer includes a base material layer and a foam material layer in contact with the skin layer.

  As the tear line, at least a center line corresponding to the boundary line of the pair of doors and side lines on both sides corresponding to both end portions of the pair of doors are formed. The center line has an extended portion that is further extended to both sides from the intersection with the side lines on both sides thereof. The center line extension is preferably extended from the original center line in a straight line, but it is extended with a certain degree of bending angle, or to some extent with a curved line that gently curves upward or downward. There can be. The length of the center line extension is not limited, and is designed to an appropriate length as necessary.

  Further, a linear cut portion having a depth reaching the portion near the skin layer in the base layer is intermittently provided over the entire tear line excluding the center line extension portion. In addition, the center part of the center line, the part in the vicinity of the intersection with the side lines on both sides of the center line (excluding the center line extension), and the side lines on both sides have at least bottom dot cut and intermittent dot cut. Provide one. An independent dot cut is provided at the center line extension.

  More specifically, in the center line, bottom dot cuts that are closely spaced from each other are provided in the center and in the vicinity of the intersection with the side line (excluding the center line extension). On the side lines on both sides, a bottom dot cut with a close interval and an intermittent portion dot cut with a close interval are provided. In the centerline extension, independent dot cuts are provided at the required density.

  Even in the portions other than the above in the tear line, bottom dot cuts and intermittent dot cuts that are not closely spaced can be provided in a design-suitable portion.

  Next, an embodiment of the present invention will be described with reference to FIGS. The technical scope of the present invention is not limited by the following examples.

  The airbag door tear line of the present embodiment is set at the front part of the passenger seat in the vehicle instrument panel. As shown in FIG. 1, the tear line 1 has, as a basic shape, a center line 2 corresponding to a boundary line of a pair of airbag doors and side lines on both sides corresponding to both side ends of the pair of doors. 3 and upper and lower horizontal lines 4 corresponding to the upper and lower ends of a pair of doors formed in parallel to the center line 2. In addition, as a characteristic tear line portion, a center line extension portion 5 in which a part of the center line 2 is further extended to both sides from the intersection with the side lines 3 on both sides is also provided.

  As shown in FIGS. 2 to 5 in common, the instrument panel 6 according to the present embodiment is in contact with the base material layer 7 constituting the back side surface, the relatively thick foam material layer 8 in contact with the base material layer 7 and the base material layer 7. And it is a laminated structure which consists of the thin skin layer 9 which comprises the surface side (vehicle compartment side) surface of the instrument panel 6 with it. The base material layer 7 is made of polypropylene, the foam material layer 8 is made of foamed polypropylene, and the skin layer 9 is made of polyolefin.

  As shown in FIG. 2 (a) and FIG. 2 (b), as a basic tiering process in all parts of the tier line 1 shown in FIG. A linear cut portion 10 having a depth reaching the vicinity of the skin layer 9 is provided. 2A is a cross-sectional view taken along the tear line 1 of the instrument panel 6, and FIG. 2B is a plan view of the illustrated portion of FIG. 2A viewed from above.

  The linear cut portion 10 is a long hole formed intermittently along the tear line 1 as shown in FIG. 2B, and its short diameter is 1 mm. Further, as shown in FIG. 2A, the major axis of the linear cut portion 10 is uniformly 4 mm, and the width of the intermittent portion 11 where the linear cut portion 10 is not formed is uniformly 6 mm. Basic tear processing shown in FIGS. 2A and 2B is performed on the upper and lower horizontal lines 4 in the tear line 1.

  Here, for convenience of explanation based on the figure, the center line center part 12 and the center line extension part from the center line 2 are displayed as indicated by broken lines for each part of the tier line 1 shown in FIG. A centerline intersection 13 that is an intersection with the sidelines 3 on both sides in a portion extending over 5, a sideline portion 14 that is a portion of the sidelines 3 on both sides, and the centerline 12 and the centerline in the centerline 2 An area name of the center line side part 15 which is an intermediate part with the intersection part 13 is given. Except for the portion of the centerline extension portion 5 at the centerline intersection portion 13, each of these regions is shown in FIG. 3 to FIG. 3 for the purpose of imparting different relative weaknesses to the skin rupture strength at those portions. The dot cut 16 which is the additional tiering shown in FIG. These dot cuts 16 have a hole diameter of 1 mm, which is the same as the short diameter of the linear cut part 10, and therefore, for example, the linear cut part 10 and the dot cut 16 are continuously formed in the same process using the same end mill. can do.

  In the centerline side part 15, as shown in FIG. 3, the dot cut 16 which reaches from the bottom part of each linear cut part 10 which has a major axis of 4 mm to the thick part of the skin layer 9 is formed one by one. Yes. That is, the formation density of the dot cuts 16 is low. Accordingly, the center line side portion 15 is not weak in the relative skin breaking strength in the tear line portion where the dot cut 16 is provided.

  Next, in the center line center part 12 and the part excluding the center line extension part 5 in the center line intersection part 13, as shown in FIG. 4, from the bottom part of each linear cut part 10 having a long diameter of 4 mm. Two dot cuts 16 are formed. As described above, considering that the particularly preferable mutual distance between the dot cuts 16 having a hole diameter of 1 mm is about 1 mm, the formation density of the dot cuts 16 is very high. Therefore, in these portions, the relative skin breaking strength is considerably weak in the tear line portion provided with the dot cuts 16 because of the high density of the dot cuts 16 in the linear cut portions 10.

  Further, in the side line portions 14 on both sides, as shown in FIG. 5, two dot cuts 16 are formed from the bottom of each linear cut portion 10, and each intermittent portion having a width of 6 mm. Also from the part 11, dot cuts 16 reaching from the base material layer 7 to the thick part of the skin layer 9 are formed at a mutual interval of 1 mm.

  As shown in FIG. 5, the number of dot cuts 16 formed in each intermittent portion 11 is two to three from the relationship between the hole diameter of the dot cuts 16 and the mutual interval, and three dot cuts 16 are formed. In this case, one dot cut 16 is formed at the end of the adjacent linear cut portion 10. As described above, in the side line portions 14 on both sides, the dot cuts 16 are formed at a very high density both in the linear cut portions 10 and in the intermittent portions 11, and therefore, in the tier line portion where the dot cuts 16 are provided. The relative skin breaking strength is the weakest.

  Next, in the portion of the centerline extension portion 5 in the centerline crossing portion 13, as shown in FIG. A dot cut 16 (independent dot cut described above) reaching from the material layer 7 to the thick part of the skin layer 9 is formed. Therefore, although the skin breaking strength is weak in the centerline extension part 5, the breaking strengths of the base material layer 7 and the foam material layer 8 are much stronger than those of the other regions described above.

  In the present embodiment, since the tear line 1 is configured as described above, when the airbag is deployed, the skin rupture starts from the centerline central portion 12 that first receives the deployment pressure of the airbag. Line 2 includes the center line side part 15 and the skin breaks at a stretch. Furthermore, since the center line extension 5 is extended in the center line 2, the entire tear line in the direction of the center line 2 including the center line intersection 13 is cut in a straight line.

  Further, since the side line portions 14 on both sides have the weakest surface breaking strength, the skin breaking operation in the center line direction is smoothly changed to the skin breaking operation of the side line 3 in a direction intersecting substantially at right angles to the center line direction. Converted to

  Moreover, at the time of these skin breaks, in the portion other than the centerline extension portion 5 in the tear line 1 is accompanied by the breakage of the base material layer 7 and the foam material layer 8, but only the skin breakage occurs in the centerline extension portion 5, The base material layer 7 and the foam material layer 8 do not break.

  As a result of these series of breaking operations, the pair of doors of the airbag doors are sufficiently opened, and there is no hindrance to sufficient deployment of the airbag. In addition, since the airbag door is ruptured in a clear manner, burrs or the like are not generated at the rupture edge portion, and there is no possibility of damaging the deployed airbag.

  According to the present invention, an ideal skin break pattern of a tear line at the time of airbag deployment can be realized, and a tear line forming method and means necessary for developing the skin break pattern are provided.

It is a figure which shows the whole shape of the tear line which concerns on an Example.

It is sectional drawing which shows the basic form of the tear process which concerns on an Example.

It is sectional drawing which shows the additional form of the tear process which concerns on an Example.

It is sectional drawing which shows the additional form of the tear process which concerns on an Example.

It is sectional drawing which shows the additional form of the tear process which concerns on an Example.

It is sectional drawing which shows the form of tear processing which concerns on an Example.

Explanation of symbols

DESCRIPTION OF SYMBOLS 1 Tier line 2 Center line 3 Side line 4 Horizontal line 5 Center line extension part 6 Instrument panel 7 Base material layer 8 Foam material layer 9 Skin layer 10 Linear cut part 11 Intermittent part 12 Center line center part 13 Center line crossing part 14 Side line part 15 Center line side part 16 Dot cut

Claims (5)

In an automotive instrument panel, which is a laminated structure consisting of a base layer and a skin layer, a center line corresponding to the boundary line of a pair of doors of an airbag door and sides on both sides corresponding to both side edges of the pair of doors It is a tier line set by tier processing,
The center part of the center line in the tier line, the intersecting part of the center line with the side lines on both sides, and the skin rupture strength of the side lines on both sides are selected by selecting at least one of the cutting form and the cutting frequency of the tiering process in the part. It is set so that the tear line skin breakage occurs in the order of (1) to (3) below, or (2) and (3) occur simultaneously after (1). A tear line for airbag doors.
(1) First, the center part of the center line breaks.
(2) Fracture in a straight line until the entire center line reaches both ends.
(3) A pair of side lines breaks. The tear line for airbag doors according to claim 1, wherein at least one option of a cutting form and a cutting frequency of tear processing in the tear line is as follows (1) to (3).
(1) The above-mentioned tear processing cut form options include a linear cut portion provided intermittently at a depth reaching the portion near the skin layer in the base layer, and a thick portion of the skin layer passing through the base layer. And a dot cut which is a dot-like cut portion.
(2) In the cut form of the dot cut, the dot cut provided at the bottom of the linear cut portion and the portion where the linear cut portion is not set reach from the base layer to the thick part of the skin layer. And provided dot cuts.
(3) The options for the cutting frequency of the tiering are the length of the linear cut portions, the mutual interval between the linear cut portions, and the bottom of the linear cut portion or the portion where the linear cut portion is not set. And the mutual interval of the provided dot cuts. The base layer includes a base material layer and a foam material layer, and the linear cut portion is provided at a depth that passes through the base material layer and reaches a portion near the skin layer in the foam material layer. Item 3. The airbag door tear line according to Item 2. The airbag according to any one of claims 1 to 3, wherein a center line in the tear line is provided with an extension portion further extended to both sides from an intersection with the side lines on both sides. Door tear line . The center line and the side line excluding the extension portion are provided with only dot cuts that are dot-like cut portions that pass through the base layer and reach the thick part of the skin layer in the extension portion of the center line. In addition to intermittently providing a linear cut portion having a depth reaching the vicinity of the skin layer in the base layer, at least one of the bottom portion of the linear cut portion and the portion where the linear cut portion is not set passes through the base layer The tear line for airbag doors according to claim 4, wherein a dot cut that is a dot-like cut portion reaching a thick portion of the skin layer is provided.

Images