The present invention relates to a method for producing a control arm for arrangement on an automobile axle and to a control arm for arrangement on an automobile axle.
The following discussion of related art is provided to assist the reader in understanding the advantages of the invention, and is not to be construed as an admission that this related art is prior art to this invention.
Axle components in form of tie rods, control arms or coupling rods are used to transmit static and dynamic wheel forces to an auxiliary axle frame or to an automobile body. These axle components are hereby rotatably and/or pivotally coupled between wheel supports and support locations on the vehicle. The coupling occurs mostly by way of rubber-metal bearings.
The wheel forces to be transmitted have hereby a peak range of up to several thousand Newton, so that the wheel guiding control arms must be able to withstand high and strong peak loads as well as continuous vibrational loads. The wheel guiding control arms are additionally subjected to strong vibrations resulting from different driving conditions, in particular uneven road surfaces, but also unbalances on a vehicle wheel.
The dynamic driving profile required for modern automobiles necessitates the use of particularly lightweight components on the side of the unsprung masses. In addition, automobile manufacturer are continuously required to reduce the overall vehicle weight in order to reduce fuel consumption and CO2 emission.
Conventional control arms are largely constructed as steel components, so that they can satisfy the requirements of low weight, high stiffness, long service life and advantageous manufacturability. For example, multi-part control arms made of steel typically have an upper shell and a lower shell, to which different bearing seats, spring seats or damper seats are attached. A control arm of this type is typically finished with weld joints. Producing a robust component with a long service life requires numerous process steps as well as extensive anticorrosion post-treatment.
Disadvantageously, the hardened structure of welded assemblies fundamentally changes in the region of the weld seam and in the zone around the weld seam affected by the heat. A clean welding result is frequently difficult to achieve in particular with components having a complex geometry. Disadvantageously, welded steel structures are also susceptible to corrosion. Although the weld seams increase the stiffness when the different components are joined to form a control arm, the weight of the component itself also increases due to the additional welding material.
Control arms can also be manufactured cost-effectively by molding, for example casting. Control arms with an X-shaped structure can be formed in this way. Complex geometrical shapes are possible by casting, which are not possible with a welded steel structure. For example, control arms in form of hollow aluminum parts are produced by casting. Lost cores, for example sand cores and the like, are mostly used for the hollow space. Disadvantageously, control arms produced by casting, in particular as a hollow component, have a high production tolerance. For supporting the cores enclosed in cast components, it may sometimes be necessary to leave the exterior sides open, which may adversely affect the torsional stiffness of such profile components.
Another disadvantage of cast components is a high porosity of the component itself. This results in a lower strength compared to, for example, components processed by forming. In most cases, a subsequent forging process is used for increasing the strength of cast components. However, the forging process itself in turn increases the production costs of the component, as well as reduces the degrees of freedom in the production.
Control arm with variable curvature can also be produced by extrusion. However, the extrusion process is difficult to control.
It would therefore be desirable and advantageous to obviate prior art shortcomings and to provide an improved method for producing a control arm, as well as a control arm which can be produced more cost-effectively compared to conventional production methods, while simultaneously providing high stiffness of the control arm and in particular good dimensional accuracy.