WO2003046390A2 - Method for fixing an insert in a component consisting of a lightweight material - Google Patents

Abstract

The invention relates to a method for fixing an insert (6), which can be used as an assembly element, in a component (1) consisting of a lightweight material, especially a metallic cellular material. To this end, the component (1) is provided with a recess (2) into which a body (5) consisting of thermoplastic material is inserted. For introduction into the recess (2), the insert (6) is fixed to a sonotrode (9) which is used to plastify the thermoplastic material and thus to join the insert (6) to the component (1) in a material fit, and in a fixed and positively locking manner, in the region of the recess (2).

Description

Method for attaching an insert to a component made of a lightweight material

The invention relates to a method of the type specified in the preamble of claim 1.

Components made of lightweight materials, in particular metal foams and other (metallic) cellular materials, are increasingly used in vehicle construction in order to reduce the component mass with sufficient strength and rigidity. But they are also used in many areas of mechanical engineering application and characterized by the resolution of the compact and solid structure in an open or closed-cell structure. For the industrial (large) use of such materials or with these produced composite materials, it is necessary to use preferably made of metal mounting elements such. As screws, bolts, pins od. Like. To provide. For this purpose, suitable joining methods are needed, since the mounting elements can not be easily permanently attached to the components.

Bonding, screwing, soldering and special welding processes have proved to be fundamentally suitable joining methods. However, this is not unlimited.

In the case of direct welding of metal foams, problems arise which are foam-side due to the very small and especially uneven thickness of the areas to be welded. The relatively high welding temperature implies residual stresses in the heat affected zone and usually leads to distortion.

When soldering foamed materials, corrosion problems as well as influences on the properties of the cellular material in the contamination area can occur due to the penetration of soldering flux into the porous foam structure. Furthermore, the strength of soldered joints is often significantly lower than the technical yield strength of the foam material at the same density.

The exclusively non-positive joining process "screws" is hardly usable due to insufficient strength of the foam structure.

Ideal would be a surface or voluminous and cohesive joining process. This requirement corresponds to bonding as a joining technique. Almost all material groups can be combined with one another without the material properties of the components being changed inadmissibly. Gluing is one of the low-heat joining methods, in which no local weakening of the joining zone but a planar cohesive connection of the joining parts takes place. Their strength is usually higher than that of the cellular material. Furthermore, the joining method "gluing" in particular in mixed construction, d. H. have multifunctional properties when using different metallic and / or non-metallic materials and additionally perform tasks such as electrochemical insulation and sealing function. Disadvantages with regard to the process speed are the curing times, which are often several hours at room temperature, of suitable, in particular thermoset reaction adhesives. A shortening of the

Curing times would indeed be possible by increasing the curing temperature, but requires further expenditure on equipment and financial commitment.

In the case of the introduction of mounting elements in the form of inserts, with which screws, pins, nuts od. Like. Be firmly connected, allow metallic cellular materials (eg., Metal foams) the on or foaming of these inserts directly at the manufacturing process. For this purpose, however, only compact materials come into question, which have a higher melting point than the prevailing process temperatures during foaming. The use of such inserts made of compact material requires because of the considerable thermal load a larger volume and thus contradicts the lightweight design, which is behind the use of cellular materials. On the other hand, the position of the fastener is clearly defined by the foaming, and any tolerance overlays may not be compensated under certain circumstances.

In addition, it is known for producing a fixed connection between a component made of a cellular material and a component made of a compact material (DE 199 17 132 A1), to place the two components together and then to connect them together by ultrasonic welding. For the production of solid and permanent compounds, however, relatively large contact surfaces are required, which are not always desirable and are not always available.

For the connection of plate-shaped components, it would also be possible to provide a plate with a recess, to use in this a sleeve-shaped insert and then connect the bottom by ultrasonic welding to the other plate (DE 196 10 636 C2). However, such a type of fastening presupposes that at least the insert consists of a material that can be welded by ultrasonic energy, which is not always desirable for stability reasons. In addition, in such a procedure with the bottom of the insert only a relatively small contact surface for the produced, non-positive connection available.

In another known method (US Pat. No. 4,817,264), flanged, rivet-type inserts are used, which are inserted into through holes of the components and plasticized on the flanges remote from the holes projecting ends by ultrasonic energy and deformed into rivet heads , as is common practice in ultrasonic welding. The joining is done here exclusively by positive engagement and requires a component completely penetrating recess. If instead a recess in the form of a blind bore is desired, then first a receiving body of thermoplastic material must be secured in the recess, which is followed in a particular operation by forming a glued and snap connection. Thereafter, the actual use is fixed by ultrasonic energy in the Aufhahmekörper, so that there is a comparatively complex and durchfuhrbares only with suitable, attached to the component surface layers joining process.

Finally, a method of the type described above is known (DE 695 03 284 T2), in which a plate-shaped, made of foam or honeycomb material component is covered on opposing broad sides with cover layers or thermoplastic material and provided with a specific for receiving an insert recess. The insert is made of thermoplastic material and has at its axial ends so-called sacrificial edges which are plasticized by ultrasonic vibrations and melted with the edges of the two cover layers adjoining the recess. This method is therefore only applicable if both the inserts and the outer layers of a thermoplastic material or the inserts are provided in a complex process step with thermoplastic sacrificial edges.

Against this background, the invention is based on the technical problem that

Process of the type described at the outset so that it is also suitable for the connection of metallic inserts to components made of metallic-cellular materials or composites thereof, in a simple way allows a permanent good attachment of the inserts in the components and in principle neither cover layers still continuous recesses required for the inserts.

To solve this problem serve the characterizing features of claim 1.

The invention has the advantage that by the additional introduction of a body made of thermoplastic material is an existing metal insert

Ultrasonic energy are connected to a likewise made of metal component can. The connection must not be made surface by contacting the insert with the component at the intended broadsides, but rather can be made substantially voluminous in the recess itself by means of an intermediate layer of thermoplastic material. If a component made of a (metallic) cellular material is used, then there is the further advantage that the thermoplastic material can penetrate deep into the pores of the material and thereby form a positive connection with the latter. The same applies to the side of the insert when it is provided at its protruding into the recess outer surface with suitable for receiving the thermoplastic material wells. Moreover, the joining method according to the invention requires neither a recess passing through the component nor any cover layers and can be carried out largely independently of the materials provided for the component and the insert.

Further advantageous features of the invention emerge from the subclaims,

The invention will be explained in more detail below in connection with the accompanying drawings of exemplary embodiments. Show it:

1 shows a schematic section through a component to be provided with an insert in a first stage of the method according to the invention;

Fig. 2 to 4 of Figure 1 corresponding views of further stages of the method according to the invention.

Fig. 5 is a view corresponding to Figure 2 in magnification. and

FIGS. 6 and 7 of FIG. 1 corresponding views when using alternative embodiments of the method according to the invention.

In the embodiment of FIGS. 1 to 4 is a component 1 with a z. B. cylindrical recess 2 is provided, which incorporated from a broad side 3 ago and in the manner of a Blind bore is formed. The recess 2 has a central axis 4, which extends in the embodiment substantially perpendicular to the broad side 3. In the recess 2, a body 5 is arranged made of a thermoplastic material, which is formed in the embodiment as hülsenföπniger or hollow cylindrical hollow body and has an axial height, which is expedient equal to the depth of the recess 2. In the inserted state according to FIG. 1, the body 5 therefore terminates flush with the broad side 3.

An insert 6 is intended to be introduced into the recess 2 and firmly connected to the component 1. The insert 6 has at its upper end, in particular Fig. 4 shows, provided with an internal thread 7, axial bore 8. In this bore 8, a fastening screw od after the attachment of the insert 6 on the component 1. The like. Are screwed, whereby the insert 6 forms a mounting element by means of which any other components can be firmly connected to the component 1.

The bore 8 is used, as shown in FIGS. 1 to 3, when carrying out the joining method according to the invention also for receiving the free end of a sonotrode 9, which is provided with an external thread in the internal thread 7 and are firmly screwed into the bore 8 can.

The attachment of the insert 6 in the recess 2 according to the invention z. Example, characterized in that first introduced the body 5 made of thermoplastic material in the recess 2 and then the previously bolted to the sonotrode insert 9 9 in the direction of the arrow of the recess 2 is coaxially approximated to the central axis 4 (Fig. 1). As soon as the lower end of the insert 6 has reached the body 5 (FIG. 2), the sonotrode 9 is activated or set into mechanical ultrasonic oscillations until the thermoplastic material of the body 5 has been largely or completely plasticized and thereby comes close to the body the recess 2 enclosing the circumference of the component 1 and the opposite outer lateral surface of the insert 6 conforms. Of course, the sonotrode 9 as needed, just before or after Contacting the insert 6 with the body 5 are activated.

The insert 6, after being placed on the body 5, is advanced continuously or stepwise with a force F in the direction of the arrow until it preferably rests on the bottom of the recess 2 (FIG. 3) and the plasticized thermoplastic material 10 of the body 5 (FIG. 3 and 4) completely into the space between the peripheral wall of the recess 2 and the lateral surface of the insert 6 occurred and is uniformly distributed in this. Subsequently, the sonotrode 9 is rotated out of the bore 8 and removed (FIG. 4). The cooled thermoplastic material 10 then establishes an intimate and firm connection of the insert 6 with the component 1. The entire joining process, including the cooling of the thermoplastic material takes only a few seconds.

To introduce the insert 6 in the recess 2, the sonotrode 9 is suitably attached to a converter, not shown, the z. B. formed as a piezoelectric vibration generator and in turn is coupled to a motor, hydraulic or pneumatic operated feed unit. For this purpose, suitable devices are for. B. in devices for ultrasonic welding generally known.

For carrying out the described joining method, it is expedient for the body 5 to have an outer cross-section K 1 (FIG. 5) which is slightly smaller than that

Inner cross-section A; the recess 2 is, and therefore can be easily inserted into the recess 2 with a small gap. In contrast, the z. B. cylindrical insert 6 have an outer cross-section E _a , which is slightly larger than the inner cross-section K _; of the body 5 is. This ensures that the cavity formed between the insert 6 and the peripheral wall of the recess 2 has a slightly smaller volume than the body 5 and the thermoplastic material is therefore displaced radially to the central axis 4 during insertion of the insert 6 and during melting. Excess thermoplastic material can therefore occur in particular in open pores and other formed in the peripheral wall of the recess 2 cavities, as they are in particular when using metallic-cellular materials and other lightweight materials, and in this way parallel to the central axis 4 a positive connection with the Enter peripheral wall of the recess 2.

The preferably consisting of a hard, solid metal insert 6 is provided in a particularly preferred embodiment of the invention on its outer, originally cylindrical lateral surface with at least one recess 11 (Fig. 5), the z. B. is formed by a circumferential, incorporated into the lateral surface notch, groove, groove or other recess and can stand next to them corresponding ribs 12 with the dimension E _a . Preferably, a plurality of such recesses 11 is provided. As a result, the thermoplastic material 10, as shown in FIGS. 3 and 4, can also penetrate into the depressions 11 during the melting process in order to form a positive connection with the outer jacket surface of the insert 6. After cooling, the thermoplastic material 10 then forms a hard plug, which connects the insert 6 not only materially, but also positively with the component 1 and therefore could be removed again in the direction of the central axis 4 only with a very high withdrawal force.

As further shown in FIG. 5, the insert 6 is provided at its lower end with a chamfer 14 which, when introduced into the recess 2 or the body 5, serves as an insertion bevel and centering means and the radial displacement of the plasticized material of the body 5 can promote. In addition, it is possible to provide the insert 6 at an _υ axial end or in a region which is arranged above its portion to be located in the recess 2, to be provided with a circumferential flange 15 which has a larger outer cross-section than the measure e _a in Fig. 5 corresponds to, and hang up at the fastening operation on the broad side 3 of the component 1. As a result, the fatigue strength of the connection with respect to tilting movements transversely to the central axis 4 during later use can be improved. In addition, the flange 15 may cover the connection gap and, if appropriate, prevent the lateral outflow of plasticized material before the final curing.

6 shows an exemplary embodiment in which an insert 16 has at its upper end an axially projecting lug 17 provided with an external thread section and onto which a sonotrode 18 provided with a corresponding internal thread is screwed becomes. After Fügeyerfahren and after removing the sonotrode 18 of the insert 16 therefore forms a mounting element, at its approach 17 z. B. a nut or a provided with a corresponding internal thread further component can be attached. It is clear that the bore 8 and the internal thread 7 (FIG. 4) could also be formed on a projection of the insert 6 protruding beyond the component 1. Moreover, the arrangement and the procedure in the exemplary embodiment according to FIG. 6 correspond to those according to FIGS. 1 to 5.

In the embodiment of FIG. 7, a difference from Fig. 1 to 5 is that a component 19 is used from a composite construction, in which z. B. a metallic-cellular material 20 is coated on both sides with a cover layer 21 of metal or other material. Otherwise this embodiment corresponds to that of FIGS. 1 to 5.

The inserts 6, 16 may alternatively be provided instead of an inner or outer threaded portion and inner bores with parallel to the central axis 4 elongated grooves for receiving spring pins or in the manner of studs with cylindrical projections, the transverse bores for receiving dowels or the like. The particular shape of the insert 6, 16 depends on the needs of the case. In addition, it is clear that the properties or features of the insert 6, 16 (for example, external cross-section E _a in FIG. 5) which are important for the joining method _, only the part to be introduced into the recess 2 or to be located in the recess 2 relate, while an additional, after completion of the joining process from the recess 2 outstanding portion of the insert 6 can be made substantially free. However, as shown in FIG. 4, the insert 6 may also be so short that it disappears completely in the recess 2, in particular if it has no flange 15.

A further embodiment of the invention provides that the recess 2 and / or at least the outer lateral surface of the section of the insert 6, 16 located in the recess 2 are non-circular (eg oval or angular), thereby increasing the height relative to a rotationally symmetrical shaping To achieve anti-rotation. In addition, could the recess 2 completely enforce the component 1, in which case the component 1 would have to be deposited on the implementation of the joining method on a suitable base, which generates a force F counter to the counterpressure.

The component 1 and the material 20 of the component 19 may be suitable especially for lightweight construction materials such. As aluminum, steel and magnesium foams and other metals are produced with high porosity. But other materials are useful, provided that they are not adversely affected by the sonotrodes 9, 18 acting on them with ultrasonic vibrations. In contrast, for the body 5 preferably thermoplastic materials such. As polyamide (PA), polycarbonate (PC) or acrylonitrile butadiene styrene (ABS) used, which are easily plasticized by ultrasonic energy. The inserts 6, 16 should eventually consist of a metal or a metal alloy, although other, sufficiently hard and non-thermoplastic meltable plastics would be suitable.

The invention is not limited to the described embodiments, which can be modified in many ways. This applies in particular to the described dimensions and geometric shapes of the various parts. It should also be noted that the outer contour of the introduced into the recess 2 portion of the insert 6, 16 does not have to coincide with the inner contour of the recess 2 surrounding circumferential wall identical. It is only necessary that the body 5 has a sufficiently large volume to the space between the recess wall and the outer surface of the insert 6, 16 as completely as possible, ie volumetric fill. For this purpose, it would also be possible to form the body 5 substantially solid and instead form the insert 6, 16 at least on its underside as a hollow body, so that excess thermoplastic material can be accommodated in a cavity of the insert. In addition, the axial height of the body 5 could also be smaller than the depth of the recess 2. Further, it would be possible to insert the body 5 and the insert 6, 16 at the same time in the recess 2 by the body 5 z. B. formed as a hollow body and optionally with a slight interference fit on the insert 6, 16 is pushed until it z. B. from below against the flange 15th (Fig. 5) abuts. In this case, it would even be possible for the measure K 1 (FIG. 5) to be slightly larger than the dimension A; to choose. Also combinations of these two variants are possible. Of course, it would also be possible to dimension the axial length of the section of the insert 6 coming into the recess shorter than the depth of the recess 2 measured in the axial direction. Furthermore, the sonotrode 9, 18 could be coupled to the insert 6, 16 by means other than those described. Finally, it is understood that the various features can also be used in combinations other than those illustrated and described.

Claims

claims 1. A method of attaching a usable as a mounting element insert (6, 16) on a component (1, 19) made of a lightweight material, in particular a metallzellzellenen material by the component (1, 19) provided with a recess (2), the insert (6, 16) at least partially inserted into the recess (2) and the component (1, 19) and the insert (6, 16) are then firmly joined together by application of ultrasonic energy, characterized in that the insert (6 , 16) or in the recess (2) introduced portion of the insert (6, 16) by means of a likewise in the recess (2) introduced and plasticized by the ultrasonic energy body (5) made of thermoplastic material material and / or positive fit with the recess (2) limiting peripheral wall of the component (1, 19) is connected. 2. The method according to claim 1, characterized in that the existing of thermoplastic material body (5) introduced into the recess (2), the insert (6, 16) attached to a sonotrode (9, 18) and with this in the direction of Recess (2) pushed forward and the sonotrode (9, 18) for plasticizing the body (5) is set in ultrasonic vibration. 3. The method according to claim 1 or 2, characterized in that the consisting of thermoplastic material body (5) is provided with such an oversize, the same when Eiiiführen the insert (6, 16) or a portion thereof in the recess (2) plasticized thermoplastic material is radially displaced in cavities of the peripheral wall of the component (1, 19). 4. The method according to any one of claims 1 to 3, characterized in that the insert (6, 16) is provided at its outer jacket compartment with at least one intended for receiving thermoplastic material recess (11). 5. The method according to claim 4, characterized in that the recess (11) is formed by an incorporated into the cladding surface notch, groove or recess. 6. The method according to any one of claims 1 to 5, characterized in that the existing body of thermoplastic material (5) is formed as a sleeve-shaped hollow body. 7. The method according to any one of claims 1 to 6, characterized in that at least one in the recess (2) to be inserted portion of the insert (6, 16) is formed as a sleeve-shaped hollow body. 8. The method according to any one of claims 1 to 7, characterized in that the insert (6) for receiving a fastening means and / or the sonotrode (9) certain, axial recess (8). 9. The method according to any one of claims 1 to 7, characterized in that the insert (16) has an axially projecting, for receiving a fastening means and / or the sonotrode (19) certain approach (17).