The present invention relates, in general, to a control arm structure for wheel suspensions of motor vehicles, and to a method of making such a control arm structure.
Nothing in the following discussion of the state of the art is to be construed as an admission of prior art.
U.S. Pat. No. 5,190,803, issued Mar. 2, 1993, discloses a lightweight structure having a shell-shaped base body which has an interior accommodating reinforcing ribs made from injected-on plastic. Anchors are provided at the connecting points between the base body and the reinforcing ribs to enhance the buckling stability of the base body of steel sheet as well torsional stiffness.
U.S. Patent. Application Publication No. 2004/0131418, published Jul. 8, 2004, describes a force strut brace of a chassis of a passenger car or utility vehicle for the non-positive connection between a chassis and a wheel carrier. The force strut brace includes an elongated basic body and at least two end-side mount supports for introducing and leading out forces. The basic body is composed of a plurality of elements made of plastic and metal, wherein the connection between the metal elements and the plastic elements is realized by a deformation of a part of the plastic elements.
U.S. Patent. Application Publication No. 2003/0070387, published Apr. 17, 2003, describes a composite structure made of at least three profiles, whereby at least two profiles have a free end abutting a further profile, or engage within one another. Attached in the area of connection of the profiles is at least one reinforcing element in form-fitting engagement with the profiles. The profiles are connected to one by means of thermoplastic material in the area of the connection and include terminal indentations which are embraced by the reinforcing element.
Chassis components such as front axle carrier or rear axle carrier, twist beam rear axle, wishbone etc, are normally made of lightweight metal material, typically steel material, having a sufficient ductility to allow the necessary forming processes for realizing the desired final configurations. A high ductility in the relevant processing states runs, however, counter to the desired high mechanical strength. High-strength materials are suitable to reduce the weight of the chassis components, resulting in less fuel consumption of a motor vehicle and enhanced riding comfort as unsprung chassis masses are reduced.
In order to reduce the weight of chassis components as low as possible, the use of steel material with highest possible strength is desired. This poses a problem because the ductility decreases proportionally with an increase in strength of the steel material, rendering the steel material difficult to shape and thus requiring complicated heat treatments to achieve the necessary shaping ductility. Steel material with a tensile strength of more than 800 MPa can be shaped to a desired final configuration with desired high-strength properties, only when delivered in soft state, which requires however special thermal hardening after the shaping operation, or when delivered at high temperature with subsequent final hardening. These additional steps adversely affect manufacturing costs of complex chassis components with variable functional properties.
It would therefore be desirable and advantageous to provide an improved method of making a control arm structure for a wheel suspension of a motor vehicle, to obviate prior art shortcomings and to allow application of steel materials having high strength and low ductility.
It would also be desirable and advantageous to provide an improved control arm structure which can be made of steel materials having high strength and low ductility while still being reliable in operation.