CONTROL ARM AND METHOD FOR MANUFACTURING

Abstract: The present invention involves a control arm for use in the wheel suspension of a car. The arm is produced from a hollow, closed profile of high strength, extruded aluminium. The arm is produced in a wholly cold process, similar to the one used to produce aluminium fenders, involving stretch-bending, pressing, cutting and punching of the aluminium profile into the desired shape. The arm has a closed and smooth shape; in addition, it has a rib on its outer surface for fending off water and snow.

Description: CONTROL ARMANDMETHOD FORMANUFACTURING Field of -the invention The present invention relates to a control or link arm for use in the wheel suspensions of cars, and in particular a control arm made from aluminium, and a method for its manufacture. Prior art Traditionally, control arms are made from steel. The arms are manufactured by stamping separate details of the arm out of steel sheets and pressing them into their desired shape. The separate elements are welded together into a hollow arm, which is then painted. These are techniques that have been in use for more than a century. The necessary equipment for making components for the suspension of cars according to this method is in wide use, and the method is standard in all industrialised countries. This means that components manufactured according to this method are cheap, and all the more so, since the raw materials are cheap as well. However, these components and their method/means of manufacture also have their drawbacks. First, the steel components are relatively heavy. This is a drawback, since car manufacturers try to keep the weight of the movable components in vehicular wheel suspensions as light as possible to improve road handling. They also try to keep the overall weight of car down, to reduce fuel consumption. The manufacturers try to reduce the weight problem by stamping holes in the sheet material to lighten the component. Superfluous material is then removed, where this can be done without adversely affecting the strength of the component. However, the hollow component with its cut-outs are apt to collect snow and dirt in the harsh environment under the car. Humid dirt collects in pockets in the construction, which subsequently become growth sites for rust. The manufacturing process requires rather expensive tools. In addition, the component is made from several elements, and the separate steps in the production; stamping, welding and painting, have to be handled separately, that is, they cannot be handled in a single production line. If the manufacturer wants to change the form of the component, new dies must be made for the presses; this makes the change costly. US patent 5.800.024 describes back suspension constructions for vehicles, made from aluminium. Several of the embodiments shown are made from aluminum profiles, comprising a number of individual sub-components welded together into the finished product. Some cars of the brand BMW (Bayerische Motoren Werke, Germany) are equipped with suspension components made by similar production techniques . The drawback of this technique is that the production becomes more., complicated, demanding a very accurate shaping and welding of each individual subcomponent. The sub-components have to be shaped very accurate if an automated production line is to be used. This relates also to the less important parts of the construction, i.e. sub-components that will experience little loading or not includes mounts, etc. Further, welding of aluminium is a difficult operation that has to be done in an inert atmosphere. Welding of loaded components is generally undesirable, as the structure of the material is impaired and the component becomes weakened and less corrosion resistant. In order to compensate for this weakening, the dimensions, i.e. the wall thickness, have to be increased. Thus, some of the weight reducing benefit of aluminium is lost. Aluminium control arms have also been made as cast/forged aluminium components. This is sometimes a good solution when components with a complex shape are involved. However, the drawback is more limited regulated weight reduction, when the shape has to be solid. Another drawback is that the properties of the materials used in cast/forged processes are generally inferior due to a "short" grain structure, which makes the material brittle. Brief summary of the invention The present invention has as its objective to provide a control arm for use in wheel suspension units for cars, that is near optimum light in weight, is made from one piece, has no welds and has a aerodynamic shape which prevents the collection of dirt, and is corrosion resistant. A further objective of the present invention is to provide a method for manufacturing suspension components for cars that use cheaper tools than traditional methods, which tools might easily be adjusted to fit changes in the shape of the manufactured component, and which uses only one production line. These and other objectives are met by a control arm according to the appended claim 1, and a method for its manufacture according to claim 3. In short, the present invention relates to a control arm made from a stock extruded aluminium profile designed in shape and variable wall thickness to make it simple to form and have good performance related to weight, which has a closed shape without any unnecessary openings, and might be produced in a single production line using standard machinery and a limited tool package for the stretch- bending and forming. Drawings Figure 1 shows the overall shape of the inventive control member in side cross view (A) and flat cross view (C) , as well as in cross views along the lines a-b (B) and c-d (D), respectively. Figure 2 shows an element from the fork-shaped end of the control member with its corresponding cross view. Figure 3 shows elements from the other end of the control member, with corresponding cross views. Figure 4 shows how the control member is adapted for holding a spring when mounted in the suspension unit of a car. Figure 5 shows elements of the control member relating to its specially designed shape for fending off snow and water and for avoiding the build-up of dirt. Detailed description of the invention Figure 1 shows the inventive control arm in overview. The arm is in the form of a., bent bar with a fork at one end. The arm has in its central part (along the line C-D in the figure) an expanded portion at the upper surface. This part of the arm is intended to support a spring. A cup-shaped item inserted in a hole in the arm is adapted to hold the spring in place . The other end of the arm has a narrow shape to fit a corresponding support point of the car. The arm is made from a closed profile of high strength aluminium. The profile is cut into its proper length, and shaped by stretch-bending, pressing and punching. Openings in the construction, like those of the forked end, are cut. Other superfluous material is cut away, to define the outer shape of the arm in the area intended for supporting the spring. Holes are punched in the arm, and finally the cup- shaped item is inserted in its corresponding hole. The arm is produced by a cold process, avoiding heating, forging or welding, and involving only standard machinery. Thus, costly presses are dispensed with. In addition, due to the corrosion resistant properties of the aluminium material, painting or other surface treatment is unnecessary. Altogether this results in a manufacturing process involving a single production line. The manufacturing process is easily and rapidly changed, e.g. if it is desirable to change the form and cross section of the arm. The profile itself is designed in a such way that, while it has a weight-optimised cross section, it also has a form which with simple pressing and cutting produces a properly designed fork in the one end (Figure 2), an attachment for a cup in the central part (Figure 3), and a support face for a helical spring (Figure 4). Adjacent walls of the profile have unequal thickness, as shown on Fig. IB. Here the top and bottom walls are thinner than the side walls. In the manufacturing process, when localised pressure is applied to the side walls, the top and bottom walls easily. give in and get a proper shape. As the arm is designed in such a way that only localised shaping in each end is required, the support arm gets "clean", smooth surfaces. In addition, the profile stock has a cross section with an especially designed rib. The rib is designed to direct the stream of air around the control arm in such a way that water and snow are "torn" away from the arm and not conducted towards the wheel (Figure 5). The water/snow is conducted around the arm until it meets the rib, which has an escarpment where the water leaves the arm. The escarpment has a function similar to that of the throating below a window. Control arms are normally mounted at an inclined angle in relation to the wheel, which has the effect of leading water and debris toward the wheel housing. The inventive shape of the control arm prevents water from being conducted along the arm (Figure 5) .

Claims: P a t e n t c l a i ms 1. Control arm for use in the wheel suspension of a car, c h a r a c t e r i z e d i n that the arm is produced from a single piece of a hollow closed profile of extruded, high strength aluminium. 2. Control arm according to claim 1, c h a r a c t e r i z e d i n that in said profile adjacent walls has different thickness. 3. Control arm according to claim 2, c h a r a c t e r i z e d i n that the arm comprises a rib on its outer surface to fend off air, water and snow. 4. Method for manufacturing a control arm for a wheel suspension of a car, c h a r a c t e r i z e d i n that the method involves: • producing the arm from a single piece of a hollow closed profile of high strength extruded aluminium • shaping the profile, using a cold process involving stretch-bending, pressing, cutting and punching. 5. Method according to claim 4, c h a r a c t e r i z e d i n that the arm is produced from a profile in which adjacent walls has different thickness .

Inventors: RUSTE TRYGVE, WAALER RUNE, RUSTE, TRYGVE, WAALER, RUNE
Applicants: RAUFOSS TECH AS, RUSTE TRYGVE, WAALER RUNE, RAUFOSS TECHNOLOGY AS, RUSTE, TRYGVE, WAALER, RUNE
Application year: 2000
Main classification: D21D53
IPC codes: B60G7