Patent Publication Number: US-2022234536-A1

Title: Tear inducing apparatus for pab door and manufacturing method thereof

Description:
CROSS-REFERENCE TO RELATED APPLICATION 
     This application claims priority to and the benefit of Korean Patent Application No. 10-2021-0010414 filed on 25 Jan. 2021, the disclosure of which is incorporated herein by reference in its entirety. 
     BACKGROUND 
     1. Field of the Invention 
     The present invention relates to a passenger airbag (PAB), and more particularly, to an apparatus for inducing tearing of a PAB door when an airbag deploys and to a method of manufacturing a PAB door having the apparatus. 
     2. Discussion of Related Art 
     A passenger airbag (PAB) is installed as a safety device in a crash pad panel of a car and, in case of emergency, the passenger airbag (PAB) deploys through a PAB door (or chute). There are various methods for assembling a PAB door depending on a construction method. However, among the method, a structure in which the PAB door is coupled to the rear surface of a crash pad through vibration welding is widely used. 
     The PAB door includes a main tear portion and a hinge portion. When the PAB door is opened by the expansion of an airbag cushion, the main tear portion is first opened. The hinge portion (i.e., door rotation point) maintains the normal rotation trajectory of the PAB door, thereby preventing the PAB door from being separated from or deviating from a body of the crash pad. Stable airbag deployment performance can be secured only when such a reasonable open action is maintained. 
     However, due to the intermittent open delay of the main tear portion, a phenomenon that the entire PAB door is lifted up occurs, such that the open time is delayed and thus cracks occur in the surrounding parts including the PAB door. To prevent that, for example, a structure having arbitrary shaped tear inducing ribs are added to the main tear portion inside the PAB door. A distance between the PAB door and the airbag cushion is reduced by the tear inducing ribs. Therefore, the airbag cushion comes into contact with the tear inducing ribs at the beginning of the expansion of the airbag cushion to induce timely tear in the main tear portion. 
     As shown in  FIG. 1 , the tear inducing ribs are provided as 12 to 14 pairs of ribs  15   a  and  15   b  having arbitrary shapes of about 1.8 to 2.0 mm thick, which are arranged to face each other on both sides of a scoring line (or tear line)  13  of the main tear portion on an inner side of a PAB door  11 . Referring to the cross-sectional view of  FIG. 2 , the pair of tear inducing ribs  15   a  and  15   b  erected on both sides of the scoring line  13  of the PAB door  11 , which is coupled to a crash pad panel  17  through vibration welding, protrude inward and a distance between the PAB door  11  and an airbag cushion  19  is further reduced. Accordingly, when the airbag cushion  19  expands, the airbag cushion  19  comes into contact with the tear inducing ribs  15   a  and  15   b  before the scoring line  13 , and the airbag cushion  19  is pushed to tear the scoring line  13 , thereby solving the problem of the open time delay. 
     Side effects occur due to the tear inducing ribs  15   a  and  15   b  described above. First, as a plurality of ribs are arranged, an uneven area is wide, and thus the area that a pressing jig for vibration welding can directly press is reduced when coupling the PAB door  11  to the crash pad panel  17  through vibration welding, and thus an adhesive force is reduced. In addition, the airbag cushion may be torn during deployment due to large frictional resistance and interference with the airbag cushion caused by a large number of uneven shapes due to the excessive number and height of the ribs. 
     In addition, since the conventional tear inducing ribs  15   a  and  15   b  need to be formed of a material such as thermoplastic olefin (TPO), which is the material of the PAB door, various types of problems may occur under the conditions of deployment temperature and, furthermore, may damage the airbag cushion, thereby disturbing the normal functions of the airbag. For example, at high temperatures (about 85° C.), the ribs  15   a  and  15   b  are crushed and laid down, resulting in degradation of the tear inducing function. At low temperatures (about −35° C.), cracks occur in the ribs  15   a  and  15   b , and as a result, sharp residual edges are generated along with the scattering of debris, which may cause damage (tearing) of the airbag cushion  19 , resulting in a fatal loss of function. 
     The present invention suggests a tear inducing apparatus for a PAB door so as to solve these problems. 
     SUMMARY OF THE INVENTION 
     The present invention is directed to a tear inducing apparatus in which a conventional tear inducing apparatus having the shape of ribs is replaced with the shape of pockets so that the contact area is increased so as to stably induce the tear of a scoring line as compared to the case where an airbag cushion locally pushes several conventional thin ribs (having the thickness of 1.8 to 2.0 mm). 
     That is, the conventional several ribs are combined to form a small number of pockets (e.g., four to five), and the small number of pockets are evenly distributed over the entire length of the PAB door to maintain the balance of tear inducing. In addition, the risk of damage to the cushion is reduced by dispersing frictional resistance concentrated on the airbag cushion rather than sharp ribs, thereby preventing shape deformation and crushing of the tear inducing apparatus during deployment at high temperatures, and eliminating the risk of the occurrence of cracks at low temperatures. 
     According to an aspect of the present invention, a tear inducing apparatus for a passenger airbag (PAB) door, which is vibration-welded with a crash pad panel, includes: a scoring line disposed on the PAB door and configured to be opened when an airbag cushion deploys, and a plurality of tear inducing pockets (hereinafter, “pockets”) disposed on both sides of the scoring line to face each other and arranged in a longitudinal direction of the scoring line. Each of the plurality of pockets includes an empty inner space and a ridge including a flat portion positioned toward the airbag cushion. 
     According to another aspect of the present invention, a method of manufacturing a passenger airbag (PAB) door to be vibration-welded with a crash pad panel includes: forming a scoring line on the PAB door, in which the scoring line is opened when an airbag cushion deploys, and forming a plurality of pairs of tear inducing pockets (hereinafter, “pockets”) disposed on both sides of the scoring line to face each other and arranged in a longitudinal direction of the scoring line. Each of the plurality of pockets includes an empty inner space and a ridge including a flat portion positioned toward the airbag cushion. 
     The above-described configurations and operations of the present invention will become more apparent from embodiments described in detail below with reference to the drawings. 
    
    
     
       BRIEF DESCRIPTION OF THE DRAWINGS 
       The above and other objects, features and advantages of the present invention will become more apparent to those of ordinary skill in the art by describing exemplary embodiments thereof in detail with reference to the accompanying drawings, in which: 
         FIG. 1  shows tear inducing ribs according to the related art; 
         FIG. 2  is a cross-sectional view of  FIG. 1 ; 
         FIG. 3  is a schematic diagram of a tear inducing apparatus according to an embodiment of the present invention; 
         FIG. 4  shows only a passenger airbag (PAB) door ( 11 ) of  FIG. 3 ; 
         FIG. 5  is a cross-sectional view of the PAB door taken along line A-A of  FIG. 4 ; 
         FIG. 6  is a detailed view of one ( 21   b ) of tear inducing pockets; 
         FIG. 7  shows the opposite side of the pocket shown in  FIG. 6 ; 
         FIG. 8  is a cross-sectional view of the PAB door taken along line B-B of  FIG. 4 ; 
         FIG. 9  shows a structure between neighboring pockets; 
         FIGS. 10 and 12  illustrate two different examples of the shape of pockets ( 21   a  and  21   b ); 
         FIG. 11  is a cross-sectional view of the pockets taken along line X-X of  FIG. 10 ; 
         FIG. 13  is a cross-sectional view of the pockets taken along line Y-Y of  FIG. 12 ; 
         FIG. 14  illustrates a further embodiment of the present invention; and 
         FIG. 15  is an enlarged view of C in  FIG. 14 . 
     
    
    
     DETAILED DESCRIPTION OF EXEMPLARY EMBODIMENTS 
     Advantages and features of the present invention and methods for achieving them will be made clear from embodiments described in detail below with reference to the accompanying drawings. However, the present invention may be embodied in many different forms and should not be construed as being limited to the embodiments set forth herein. Rather, these embodiments are provided so that this disclosure will be thorough and complete and will fully convey the scope of the present invention to those of ordinary skill in the technical field to which the present invention pertains. The present invention is defined by the claims. Meanwhile, terms used herein are for the purpose of describing the embodiments and are not intended to limit the present invention. As used herein, the singular forms include the plural forms as well unless the context clearly indicates otherwise. The term “comprise” or “comprising” used herein does not preclude the presence or addition of one or more other elements, steps, operations, and/or components other than stated elements, steps, operations, and/or components. 
     Hereinafter, exemplary embodiments of the present invention will be described in detail with reference to the accompanying drawings. In describing the present invention, the detailed description of a related known configuration or function will be omitted when it obscures the gist of the present invention. 
       FIG. 3  is a schematic diagram of an embodiment of a tear inducing apparatus according to the present invention. It shows a state in which a passenger airbag (PAB) door  11  is vibration-welded with a crash pad panel  17 . The tear inducing apparatus is configured by replacing tear inducing ribs according to the conventional art with tear inducing pockets  21   a  and  21   b . About ten pairs of ribs according to the conventional art are clustered and reduced to four to five pairs of pockets  21   a  and  21   b , and these pockets  21   a  and  21   b  are evenly distributed over the entire width of the PAB door  11  to maintain the balance of tear inducing. 
       FIG. 4  is an inner-side plan view of the PAB door  11 . A scoring line or tear line  13  is formed in the center of the PAB door  11 , and four pairs of tear inducing pockets  21   a  and  21   b  face one another on both sides of the scoring line  13 . 
       FIG. 5  is a cross-sectional view of the PAB door  11  taken along line A-A of  FIG. 4 . A plurality of welding ribs  25  formed on the outer surface of the PAB door  11  are coupled with the crash pad panel  17  by welding method. In addition, a pair of pockets  21   a  and  21   b , having an approximately right triangle shape, face each other with the scoring line  13  therebetween. The inner space of the pockets  21   a  and  21   b  is empty, and several reinforcing ribs  23  are therein provided to reinforce the empty space. These reinforcing ribs  23  are preferably formed integrally with the welding ribs  25  that are originally present to be welded with the crash pad panel  17 . An airbag cushion  19  is adjacent to a ridge of each of the pockets  21   a  and  21   b.    
     In  FIG. 5 , when it is defined that a distance between the inner bottom surface (base surface) of the PAB door  11  and the ridge of the pockets  21   a  and  21   b  is referred to as a “pocket height H”, and a gap between the ridge and the airbag cushion  19  is referred to as “G”, H is about 14.5 mm and G is about 5 mm. The pocket height H is determined depending on the package conditions (i.e., the size of a PAB assembly) but should not exceed the height of the front/rear hinges of the PAB door  11 . In the case of a package in which the foremost line of the airbag cushion  19  is higher than the hinge, H=14.5 mm is ignored and G should be set to maintain a distance of about 5.0 mm. 
       FIG. 6  is a detailed view of one pocket  21   b  of the tear inducing pockets  21   a  and  21   b . The ridge includes a flat surface  24  with rounded corner. The airbag cushion  19  is designed to come into contact with the flat surface  24  of the ridge so that damage to the airbag cushion  19  can be greatly reduced. 
       FIG. 7  shows the opposite side of the pocket of  FIG. 6 . As described above, it can be seen that the pocket has a hollow shape with an empty space  22  formed therein. The reinforcing ribs  23  pass through the empty space  22  of the pocket on the bottom surface integrally with the original welding ribs  25  (see  FIG. 5 ). That is, the reinforcing ribs  23  are integrally formed with the welding ribs  25  (ribs that are welded by coming in contact with the crash pad panel  17  during vibration welding) that are originally present on the outer surface of the PAB door  11  and are integrally formed with the PAB door  11  to pass through the outer surface of the crash pad panel  17  without interruption so that there is no degradation of adhesive force after vibration welding with the crash pad panel  17 . Also, these welding ribs  25  maintain a supportive force so that cracks do not occur in the pockets  21   a  and  21   b  during a process of deployment of the airbag cushion  19 . In  FIG. 7 , it is expressed that the thickness of each of the reinforcing ribs  23  is smaller than that of the welding ribs  25 . According to the design, the thickness of each of the reinforcing ribs  23  may be about 1.5 mm, which may be about 50% of the thickness (about 3.0 mm) of each of the welding ribs  25 . 
       FIG. 8  is a cross-sectional view of the PAB door  11  taken along line B-B of  FIG. 4 . Looking at the illustrated dimensions, the distance (width) between the outer walls of the pocket  21   a  or  21   b  is about 10 mm, and the thickness of each wall is about 2.0 mm. Also, the curvature radius R of an outer corner of each of the pockets  21   a  and  21   b  is about 3 mm or more (see also  FIGS. 11 and 13 ). In this way, the corners of the ridge of the pocket  21   a  or  21   b  are rounded to prevent damage to the cushion when the airbag cushion  19  deploys. 
       FIG. 9  shows a structure between neighboring pockets. Lengthwise ribs  26  and  27  are connected between the pockets  21   a  and  21   b  and neighboring pockets  21   a  and  21   b  so as to prevent the PAB door  11  from being bent like a bow when the airbag deploys. The lengthwise ribs  26  and  27  include a relatively high first lengthwise rib  26  located under the ridge portion of the pockets  21   a  and  21   b , and a relatively low second lengthwise rib  27  located under the narrow wall portion of the pockets  21   a  and  21   b.    
     According to an actual design, heights of the lengthwise ribs  26  and  27  (i.e., the altitude from the inner bottom (base surface) of the PAB door  11 ) may respectively be 5.0 mm or less and 2.0 mm or less, each of which is lower than the height of the pocket. In particular, preferably, rounding treatment of R1.0 is performed on heads of the lengthwise ribs  26  and  27  to relieve frictional resistance when the airbag cushion  19  deploys. In addition, preferably, the positions of the lengthwise ribs  26  and  27  are not collinear with the welding ribs  25  (more preferably, the lengthwise ribs  26  and  27  are positioned to intersect the welding ribs  25 ). The reason is to prevent a sink mark and to ensure that the pressing force of a pressing jig for welding is evenly distributed during vibration welding with the crash pad panel  17 . 
     Also, a first breadthwise rib  31  having triangular shapes is connected between the first lengthwise rib  26  and the second lengthwise rib  27 , and a second breadthwise rib  29  having triangular shapes is connected between the first lengthwise rib  26  and the base surface (inner bottom surface) of the PAB door  11 . For the purpose thereof, preferably, these breadthwise ribs  31  and  29  are connected to the height of the lengthwise ribs  26  and  27  without a step height. That is, the maximum height (altitude) of the hypotenuse of the first breadthwise rib  31  is the same as the height of the first lengthwise rib  26 , and the minimum height thereof is the same as the height of the second lengthwise rib  27 . In addition, the maximum height of the hypotenuse of the second breadthwise rib  29  is the same as the height of the first lengthwise rib  26 , and the minimum height thereof is the same as the base surface (inner bottom surface) of the PAB door  11  and thus is formed to be almost zero. 
     By using these first breadthwise rib  31  and second breadthwise rib  29 , the lengthwise ribs  26  and  27  are reinforced to prevent cracks; and an uneven shape, in which frictional resistance can be generated when the airbag cushion  19  deploys, is concealed in the pocket and thus, the airbag cushion  19  can deploy more smoothly. 
       FIGS. 10 to 13  illustrate two examples of the shape of the pockets  21   a  and  21   b .  FIG. 10  illustrates an example in which the sizes of the pockets  21   a  and  21   b  facing each other are different from each other and the pockets  21   a  and  21   b  face each other in a position where the pockets  21   a  and  21   b  are shifted by a distance of approximately 6:4.  FIG. 12  shows an example in which the sizes of the pockets  21   a  and  21   b  facing each other are the same and the pockets  21   a  and  21   b  face each other in the same position.  FIG. 11  is a cross-sectional view taken along line X-X of  FIG. 10 , and  FIG. 13  is a cross-sectional view taken along line Y-Y of  FIG. 12 . 
     In  FIG. 11 , the dimensions of the larger pocket  21   a  in the shifted position are illustrated, and cross-sectional structures of the pockets  21   a  and  21   b  are shown. In  FIG. 11 , the corner curvature of the flat portion of the ridge of the pocket  21   a  is R=3, and the corner curvature of the flat portion of the ridge of the pocket  21   b  is R=4, which are different from each other. Also, “A” means an angle that the flat surface  24  (see  FIG. 6 ) of the ridge of the pocket  21   a  on the engine compartment side is set to normal (90°) at a deployment direction of the airbag cushion  19 . The reason for the normal setting is that that point is a contact surface that the airbag cushion  19  comes in contact with and pushes out. In addition, “B” means that the difference between the height of the pocket  21   a  on the engine compartment side and the height of the pocket  21   b  on the interior side is about 6.0 mm and the height of the pocket  21   b  on the interior side is set to be smaller than the pocket  21   a  on the engine compartment side. The reason is that the example of  FIG. 10  is an example in which the width of the PAB door  11  is relatively small, and in this case, the deployment resistance of the cushion is higher. 
       FIG. 13  shows that the pocket  21   a  on the engine compartment side and the pocket  21   b  on the interior side have the same shape and dimensions. Even in this case, like “A” of  FIG. 11 , the flat surface  24  of the ridge of the pocket  21   a  on the engine room side is set to normal (90°) at the deployment direction of the airbag cushion  19 . 
       FIGS. 14 and 15  illustrate a further embodiment for maximizing early tearing (opening) by the pockets of the present invention upon tearing of the PAB door by airbag cushion expansion. 
     In this embodiment, both facing pockets  21   a  and  21   b  are pushed by the inflation force of the airbag cushion (in the direction of the arrows), so that both portions of the PAB door  11  about the scoring line rotate around the door rotation points (i.e., the hinge portion)  35   a  and  35   b , respectively. The dimensions of the pockets are intentionally designed to be large so that facing surfaces  33   a  and  33   b  of both pockets  21   a  and  21   b  are docked (contacted) with each other when in initial open. 
     In  FIG. 15 , the docking point of the pockets&#39; facing surfaces  33   a  and  33   b  are indicated by “38”. The docking point will be described through an enlarged view of part C of  FIG. 14 . As shown in  FIG. 15 , when the door  11  is opened while the pockets  21   a  and  21   b  are pushed by the airbag cushion, they draw rotation trajectories  37   a  and  37   b . On the rotation trajectories  37   a  and  37   b , the dimensions of the pockets  21   a  and  21   b  are set so that the facing surfaces  33   a  and  33   b  overlap each other in the size of G (for example, 0.8 mm). 
     In this way, when in door&#39;s initial open, a concentrated tensile force is additionally induced on the scoring line formed in the PAB door  11 , by virtue of the docking by the overlap design of the pocket facing surfaces  33   a  and  33   b . That is, the docking point is leveraged as a support point at the time of docking the pockets, and an additional tensile force is generated in the scoring line of the door in both directions, and accordingly, early tearing of the scoring line is made smoothly, so that the early tearing time can be secured and the tearing stability can be achieved. 
     According to the present invention, the frictional resistance applied to a cushion when the airbag cushion deploys is reduced compared to the related art so that the risk of damage to the cushion can be eliminated, and scattering caused by cracks in a door during the deployment is eliminated so that secondary injury to passengers can be reduced. 
     In addition, many ribs of an existing PAB door are integrated to configure a tear inducing ribs in the shape of a few (e.g., four or five) pockets so that the pressure loss of a welding jig in the process of coupling the door to a crash pad panel through vibration welding can be minimized and thus the quality of welding can be stabilized. 
     Although the present invention has been described in detail above with reference to the exemplary embodiments, those of ordinary skill in the technical field to which the present invention pertains should be able to understand that various modifications and alterations can be made without departing from the technical spirit or essential features of the present invention. Therefore, it should be understood that the disclosed embodiments are not limiting but illustrative in all aspects. The scope of the present invention is defined not by the above description but by the following claims, and it should be understood that all changes or modifications derived from the scope and equivalents of the claims fall within the scope of the present invention.