JP2006256325A - Method for arranging ejection channel on airbag covering loaded with target breaking line and assembly component manufactured by the method - Google Patents

Abstract

<P>PROBLEM TO BE SOLVED: To provide a method for integrating an ejection channel onto an airbag covering by melting, without mechanical force applied on the airbag covering. <P>SOLUTION: A material engagement is performed by laser transmission welding, to avoid a mechanical load on a target breaking line integrated in an airbag covering (1) in arranging the ejection channel (2) by material engagement. A pressing force required for this purpose is applied by a frictional engagement or a positive engagement encompassing joint surfaces (3) to be welded. <P>COPYRIGHT: (C)2006,JPO&NCIPI

Description

  In an airbag cover with an integrated airbag opening, the size and shape of the opening created for the airbag passage for its operation is determined by the shape of the target break line. The airbag cover represents all the inner panels or covers of the passenger car in which the airbag is accommodated.

  The target break line often represents a closed rectangular, trapezoidal, elliptical or free-form surface. This surface is blocked only in the hinge region, leaving an opening of the same shape and size when the target break line is torn. The hinge region extends over the entire lateral length, so that the target break line is, for example, U-shaped.

  It is also known to form a target break line as a connecting line between points located on the outer peripheral line of the intended opening contour. For example, an H-shaped or X-shaped target break line.

  Regardless of the manner in which the target break line is applied to the airbag cover, a mechanical weakening of the airbag cover generally occurs along the target break line.

  The airbag cover has a very slight tear resistance that can be remanufactured along this weakened line, so that the airbag acts as a result of a predetermined pressure acting on it to open the opening for the airbag passage. The degree of mechanical weakening must be selected to ensure that the target break line will tear when activated.

  However, the tear resistance must be sufficiently high so that any mechanical force acting from the driver's compartment side will not cause part of the target break line to tear, for example, for luggage carried to passengers or passenger cabins. Don't be.

  Regardless of any forces and long-term stresses due to the effects of the natural environment, the target break line should not be permanently visible from the passenger compartment for aesthetic reasons.

  For example, care must be taken not to damage the target break line when working on the airbag cover later to place the firing passage.

  The firing passage is essentially tubular and has a different cross-sectional shape. It limits the lateral inflation of the opening airbag and serves to guide the direction of inflation of the airbag toward the passenger compartment. The firing passage is substantially adapted to the shape of the opening with respect to its inner circumference. Various external shapes of the launch passage are possible. Often, various other functional components such as air channels, securing elements, cable holders, etc. are formed in the firing passage outside the actual functional area. In this case, the firing passage is the chamber portion of the wider substructure of the airbag cover.

  Ideally, in order to hold the airbag cover along the target break line on the one hand and spread the airbag at full volume in the passenger compartment when actuated on the other hand, the launch passage adjacent to the airbag cover The inner circumference must be somewhat smaller than the opening defined by the target break line.

  In all cases, the inner circumference of the launch passage must be close to the target break line. However, this is not immediately possible with the methods known from the prior art for providing a firing passage in the airbag cover.

  In the case of a launch passage, airbag cover or multilayer airbag cover, the inner layer facing the launch passage is made of plastic.

  Ultrasonic welding or friction welding is suitable for automated mass production and creates a bond between two permanently fixed plastic parts.

  As is well known, welded connections occur by ultrasonic welding due to the vibration of the parts to be joined. That is, the dynamic mechanical force acts through the time when the welded connection is made and is transmitted to the target break line.

  In friction welding, in addition to the dynamic mechanical forces acting in the entire process, static mechanical forces are also generated, compressing the two parts to be joined together.

  In order to prevent mechanical forces from loading the target break line as much as possible, the selected coupling region should not be close to or adjacent to the target break line.

  Therefore, the selected perimeter of the firing passage must be larger than the perimeter of the intended airbag opening, or special steps must be taken in terms of construction.

  The need for an expensive holding device that carries the air bag cover and firing passage and is held against each other during welding is also disadvantageous.

  It is also known to those skilled in the art to weld plastics by laser transmission welding. In this case, the person skilled in the art knows that a welding pressure must be generated during welding in order to make a welded connection. Therefore, this method seems not suitable for another method.

  It is an object of the present invention to develop a method for joining a firing passage to an airbag cover by welding without mechanical forces acting on the airbag cover.

  It is another object of the present invention to provide an assembly part having an airbag cover and a firing passage which are coupled to each other by a welding method without mechanical force acting on the airbag cover during welding.

  This object is achieved by the method according to the invention of claim 1 and the assembly according to the invention of claim 5.

  Advantageous structures are indicated in the dependent claims.

  The essence of the invention is that the mechanical pressing force required for welding is applied between the two parts to be joined (firing passage and airbag cover) and stored prior to the welding process itself. This is achieved in that the parts to be joined are fixed together by frictional engagement or positive engagement. Coupling is performed manually or automatically by applying a static force once outside the airbag opening where no load is applied to the target break line.

  The invention will be described more fully below with the aid of examples and using the figures.

  In order to connect the airbag cover and the firing passage to each other according to the present invention, special structural steps are taken in the airbag cover and the firing passage. That is, the geometry of the coupling area must be adapted so that a frictional or positive engagement is created.

  The airbag cover must have on the side facing the firing passage a ring collar surrounding the given shape of the target breaking line outside the airbag opening, so that the firing passage just overlaps the target breaking line. It is located on this ring-shaped collar so as to extend to the area surrounded by the collar.

  Examples of cross-sectional shapes with different collars are shown in FIGS. The firing passage combined with the collar is shown schematically in each case.

  For example, FIG. 1 shows a trapezoidal or conical cross section of a collar formed in an airbag cover 1. Due to the corresponding shape of the firing channel 2, when the two parts are joined, a conical joint is created that holds the two parts together to be joined by frictional engagement. A force acts between the outer cone formed in the collar and the outer surface of the inner cone formed in the firing passage 2. These two outer surfaces also represent the bonding surface 3 where the two parts are to be welded together.

  In FIG. 2, the color cross section is rectangular. When coupled with the firing passage 2, another frictional engagement occurs by press-fit. Even in this case, the cylindrical surfaces that are compressed together are the bonding surfaces 3 for the welded connection.

  In FIG. 3, two parts to be joined are connected by snap-in connection.

  As long as there is no tension between the two parts in the pre-bonded state, i.e. as long as the connection only relies on positive engagement, the resulting material dissolution will only be between the bonding surfaces of the two parts. Force acts first.

  For example, a direct screw connection is possible, but certainly not as good as positive engagement.

  Since the strength of the laser weld connection is generally not inferior to the material strength, the spatial position of the bonding surface in the airbag cover is in principle not important for reasons related to strength. Ideally, the coupling space is arranged so that only shear stress acts when the airbag is spread. The person skilled in the art designs the geometry of the parts to be joined and the position of the joining surface so that the laser beam required for welding is optimally coupled.

  The height of the collar formed on the airbag cover is as low as possible so as not to interfere with the introduction of the target break line, but is sufficient to make a preliminary coupling connection with the firing passage as described above. The frictional or positive engagement thus produced is hereinafter referred to as a preliminary coupling connection in order to clearly distinguish it from an actual connection made by laser transmission welding. Preliminary joint connection positions and fixes the parts to be joined together and stores a pressing force with which surfaces (hereinafter referred to as joining surfaces) are pressed together.

  This pressing force then creates the necessary welding pressure when creating material engagement by laser transmission welding that provides permanent mechanical stability to the connection. When the preliminary coupling connection is simply positive engagement, this pressing force is first generated as an opposite force when the material dissolution formed in the coupling region is about to spread.

  The need for a laser transmission welding method and an appropriate combination of laser transmission material and laser absorption material is known to those skilled in the art and need not be described further here. In principle, it is possible to irradiate the coupling surface from the rear of the airbag cover to which the launch passage is fixed and from the front as long as only the material located in front of the coupling surface in the irradiation area is transparent for the laser beam It is.

  Preliminary joining of the parts to be joined has the decisive advantage that, during laser transmission welding, no expensive equipment is required to hold the firing path and airbag cover in the welding position under the influence of the required welding pressure. Have.

  The airbag cover is held by the same holding device that is held when the target break line is introduced. During the welding process, the mechanical force does not act on the airbag cover and therefore does not act on the target break line.

  Those skilled in the art of the present invention are not limited to the details of the embodiments provided by way of example in the specification, and do not depart from the scope of the invention as set forth in the appended claims. It can be understood that other special forms can be implemented.

It is a figure which shows the assembly component by press fitting as preliminary connection. FIG. 5 shows an assembly part with a conical connection as a preliminary connection. It is a figure which shows the assembly component by a snap-in connection as a preliminary connection.

Explanation of symbols

1 Airbag cover 2 Launch passage 3 Binding surface

Claims (8)

A method of attaching a firing passage to an airbag cover with an incorporated target break line,
Making a preliminary connection for positioning and fixing the firing passage (2) with respect to the airbag cover (1), and coupling in a ring-shaped coupling area surrounding the target break line by frictional engagement or positive engagement of the preliminary coupling The launch passage (2) and the airbag cover (1) are in flat contact with each other along the surface (3),
Having a method step of creating material engagement between the coupling surfaces of the preliminary connection by laser transmission welding;
A method in which the necessary welding pressure is provided by the preliminary connection.   The method according to claim 1, wherein the frictional engagement is realized by press-fit.   The method according to claim 1, wherein the frictional engagement is realized by a conical connection.   The method according to claim 1, wherein positive engagement is achieved by a snap-in connection. An assembly part having an airbag cover (1) with a built-in target break line and a firing passage (2),
A collar surrounding the target break line is provided on the airbag cover (1),
An assembly in which a ring-shaped coupling surface (3) is formed in the collar and connected to the coupling surface (3) formed in the firing path by frictional engagement or positive engagement and material engagement by laser transmission welding.   6. Assembly according to claim 5, characterized in that the coupling surface (3) is the outer surface of a cone.   6. Assembly part according to claim 5, characterized in that the coupling surface (3) is the outer surface of a cylinder.   6. Assembly part according to claim 5, characterized in that the coupling surface (3) is a circular surface.

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