GB2469550A

GB2469550A - Method for manufacturing a component of a vehicle structure

Info

Publication number: GB2469550A
Application number: GB1004594A
Authority: GB
Inventors: Juergen Maier; Andreas Cott
Original assignee: GM Global Technology Operations LLC
Current assignee: GM Global Technology Operations LLC
Priority date: 2009-04-14
Filing date: 2010-03-19
Publication date: 2010-10-20
Anticipated expiration: 2030-03-19
Also published as: DE102009017374A1; GB2469550B; GB201004594D0; US20110030438A1; CN101862935A

Abstract

The present invention pertains to a method for manufacturing a component 3 of a vehicle structure particularly a vehicle seat structure that comprises the steps: pressing a starting material through a die 2 in order to produce an extruded product 1; separating a section from the extruded product 1, and forming the separated section into the component 3, wherein a varying wall thickness of the separated section is produced during the pressing through the die 2. Preferably, the component is a crossbeam of a frame-like backrest structure with the separated section having a greater wall thickness in the region of a headrest receptacle 3.1. The component may also be a seat shell. Preferably the starting material contains magnesium, aluminium or their alloys and the extruded product may be formed by impact extrusion or extrusion.

Description

METHOD FOR MANUFACTURING A STRUCTURAL COMPONENT FOR A

MOTOR VEHICLE

Description

The present invention pertains to a method for manufacturing a component of a vehicle seat structure for a motor vehicle seat or a motor vehicle structure, as well as to a motor vehicle seat or a motor vehicle with a structure that features several components, at least one of which was manufactured by means of such a method.

The backrest frames of motor vehicle seats frequently consist of metal and have the shape of an upside down U. The limbs of the U are referred to as the longitudinal beams that are connected by a crossbeam. The backrest frame needs to withstand the highest loads when the vehicle is subjected to longitudinal impacts and the torso and head of the person using the seat are thrown against the backrest and the headrest. In this case, high loads occur, in particular, at the connecting points between the backrest frame and the seat frame, as well as at the connecting points between the backrest frame and the headrest.

In order to save material and weight, the components of the supporting structure of a vehicle seat should only have a cross-sectional surface that is adapted to the respective maximum load at all locations. In frequently used backrest frames that are formed of a bent round tube, a minimum cross-sectional surface required at locations subjected to maximum loads also needs to be used at locations, at which only low loads occur.

In frames that are realized in the form of diecast magnesium parts, the cross-sectional surface can be adequately adapted to the expected load. However, certain restrictions result from the minimum wall thickness of the structural component caused by the casting technology. Other disadvantages are the high costs of the casting mould, the high material price, the low ductility of casting alloys and the high expenditures required for avoiding or detecting casting defects such as shrink holes or pores.

In frames that are formed of folded and bent sheets, limitations result from the fact that the sheets have the same thickness at all locations. A great sheet thickness is only required, for example, at the connecting points of the backrest frame to the seat frame and the headrest brackets or in the zones subjected to bending stress in the cross-sectional regions situated far from the neutral axis. A smaller wall thickness would be advantageous at all other locations because these locations are not subjected to any significant loads.

Consequently, EP 0 745 508 Bi proposes a method according to the preamble of Claim 1 for manufacturing an approximately U-shaped frame of a backrest of a motor vehicle seat that consists of two longitudinal beams and a crossbeam, wherein a profiled part with a strong center zone that is followed on both sides by a weaker region and then an adjacent strong region is initially produced from an originally straight band-like, flat extruded product or rolled product with constant cross-sectional surface by means of subsequent rolling and trimming, and wherein this profiled part is subsequently bent into the U-shaped frame.

In this case, it is disadvantageous that the rolling process represents an additional production step required for realizing the different regions of the originally straight band-like, flat extruded product or rolled product with constant cross-sectional surface.

According to DE 43 33 500 Al that does not concern the manufacture of a component of a vehicle structure or vehicle seat structure, it is necessary to subject an extruded profile to subsequent production steps, particularly to cut open and roll said profile. Alternatively, WO 00/29138 proposes to weld together adjacently arranged strips of different wall thickness in order to produce a profiled part with different wall thicknesses.

The present invention is based on the objective of improving a structure for a motor vehicle seat or a motor vehicle and a method for manufacturing a component of such a structure.

This objective is respectively attained with the characteristics of Claims 1 and 11. Advantageous embodiments of the invention form the objects of the dependent claims.

According to the invention, one or more components of a structure for a motor vehicle seat or a motor vehicle are manufactured by pressing a starting material through one or more dies in order to produce an extruded product. The extruded product may be manufactured, in particular, by means of impact extrusion or extrusion.

Subsequently, a section is separated from the extruded product, for example, by means of sawing, particularly with a band saw, cutting, particularly with a laser, or another separating method, wherein the separated section subsequently serves as a semi-finished product that is formed into the component. This may be realized, for example, by means of compressive deformation, particularly open-die forging, closed-die forging such as, in particular, forging, indentation forming and/or additional extrusion.

Additionally or alternatively, the separated section may also be formed into the component by means of indirect compression, particularly cold drawing, deep drawing, spinning, plunging, upset bulging and/or hydroforming. The separated section may be additionally or alternatively formed into the component by means of tensile forming, particularly extending and/or expanding, and/or by means of bending, particularly wiping die bending and/or die bending.

According to the invention, a varying wall thickness of the separated section is already realized when the starting material is pressed through one or more dies such that said section already has a varying wall thickness transverse to the extruding direction prior to the additional forming.

This advantageously makes it possible to eliminate one or more additional rolling or welding steps after the extrusion in the manufacture of a structural component such that the manufacturing costs and the manufacturing time are reduced.

On the other hand, regions that are subjected to higher loads can be realized with greater wall thicknesses and therefore safer and regions that are subjected to lower loads can be realized with smaller wall thicknesses and therefore lighter and with less material, namely without requiring an additional production step between the extrusion and the forming into the component of the structure.

An inventive method makes it possible, in particular, to manufacture a crossbeam of a frame-like backrest structure, in which the separated section advantageously has a greater wall thickness at least in the region of a headrest receptacle.

An inventive method likewise makes it possible to manufacture, for example, a seat shell, wherein the separated section advantageously has a greater wall thickness at least in the region of a bearing point, particularly an adjustable pivot joint for producing a connection with a backrest.

Alternatively, an inventive method also makes it possible to manufacture other components of a motor vehicle structure such as, for example, car body or paneling components.

With respect to the formability during the extrusion process, the strength and the weight, magnesium or a magnesium alloy is particularly advantageous as a starting material. In this case, it may be particularly advantageous to form the separated section into the component by means of hot forming, preferably by utilizing a heating process realized prior to or during the extrusion through the die. In comparison with conventional methods used so far, in which magnesium sheets with homogenous wall thickness were initially extruded or continuously cast and these sheets were subsequently cold-formed, the hot forming of the separated section that is still hot from the extrusion or continuous casting process provides superior formability, a superior texture and/or energy savings.

According to one preferred embodiment, the extruded product has a smaller width than the finished component during the extrusion through the die. This makes it possible, for example, to initially produce a narrow sheet that is subsequently widened, particularly in regions with greater wall thickness, by means of forming processes, preferably hot forming, particularly by utilizing a heating process realized prior to or during the extrusion through the die, such that wider structural components can be manufactured with narrower dies. Other advantageous additional developments of the present invention result from the dependent claims and the following description of preferred embodiments. In the partially schematic drawings: Figure 1A shows a step of a manufacturing method according to the state of the art; Figure lB shows a separated section according to the state of the art manufactured in the step shown in Figure 1A; Figure 1C shows a crossbeam according to the state of the art formed from the separated section shown in Figure 1B; Figure 2A shows a step of a manufacturing method according to one embodiment of the present invention in the form of a representation that corresponds to Figure 1A; Figure 2B shows a separated section manufactured in the step shown in Figure 2A in the form of a representation that corresponds to Figure 1B; Figure 2C shows a crossbeam formed of the separated section shown in Figure 2B in the form of a representation that corresponds to Figure iC; Figure 3A shows a frame-like backrest structure with the crossbeam according to Figure 2C; Figure 3B shows the crossbeam according to Figure 3A, and Figure 4 shows a seat shell according to another embodiment of the present invention.

Figure 1A shows a step of a manufacturing method according to the state of the art, in which a magnesium alloy is pressed through a die 2' in the y-direction of the coordinate system illustrated in Figure 1A in order to produce a sheet-like extruded product 1' with constant wall thickness in the x-direction, i.e., the transverse direction, wherein the height is measured in the z-direction. Figure lB shows a cross section through the extruded product 1' in the x-z plane, i.e., perpendicular to the extruding or pressing direction y, wherein the constant wall thickness is illustrated in this cross section.

Subsequently, a section is separated from the extruded product 1' by means of a cutting process and formed into the crossbeam 3' for a backrest of a vehicle seat structure shown in Figure 1C in another not -shown forming process. In Figure 1, "y" indicates the extruding or pressing direction of the original extruded product 1'. Due to the constant wall thickness of the separated section, the crossbeam formed thereof also has an identical wall thickness at all locations and therefore is undersized in regions that are subjected to higher loads or oversized in regions that are subjected to lower loads.

Figures 2A to 20 respectively show a crossbeam of a frame-like backrest structure for a motor vehicle seat and its manufacture according to one embodiment of the present invention, namely in the form of representations that correspond to Figures 1A to 10. According to the invention, an extruded product 1 with a wall thickness that varies in the x-direction, i.e., in the transverse direction, is already formed when the magnesium alloy is pressed through the die 2. In the cross section according to Figure 2B, an edge region 1.1 with greater wall thickness and an adjacent region 1.2 with smaller wall thickness are shown.

If the crossbeam 3 is now produced from this extruded product in the above-described fashion by separating a certain section and subsequent forming, the region 1.1 with the greater wall thickness forms a headrest receptacle 3.1 of the crossbeam 3 as indicated with broken lines in Figure 2C if this region 1.1 that extends in the profile direction y is bent during the forming process. This makes it possible to manufacture an advantageous crossbeam 3, the headrest receptacle 3.1 of which is subjected to higher loads and therefore has a greater wall thickness while material and weight are saved due to smaller wall thicknesses in frontal and lateral regions that are subjected to lower loads, namely without having to separately produce an extruded profile with varying wall thickness between the extrusion according to Figure 2A and the forming into the final shape of the crossbeam 3 according to Figure 2C by means of rolling or welding together strips.

Figure 3A shows the frame-like backrest structure 4 with two lateral parts and the aforementioned upper crossbeam 3 that is illustrated in an enlarged fashion in Figure 3B such that, in particular, headrest guide receptacles 3.2 in the region of the headrest receptacle 3.1 are clearly visible.

Figure 4 shows a seat shell 5 that was manufactured accordingly by means of extruding and subsequent forming into the final shape, namely without an intermediate rolling process for changing the wall thickness of the extruded profile 1. Since one edge region 1.1 was once again realized with a greater wall thickness and rear bearing points 5.1 of the seat shell 5 are produced with this edge region during the forming process, the bearing points 5.1 that are subjected to higher loads also have a greater wall thickness while material and weight are saved in a front region that is subjected to lower loads.

List of Reference Symbols 1, 1' Extruded product 1.1, 1.2 Region of extruded product 2, 2' Die 3 Crossbeam 3.1 Headrest receptacle 3.2 Headrest guide receptacle 4 Backrest structure Seat shell 5.1 Bearing point