Zf Lenksysteme Gmbh

Zf Friedrichshafen

Alfred Brenner

Werner Breitweg

Andreas Eisenhuth

Bernd Koziara

A technique for manufacturing a gear rack ( ) for a rack-and-pinion steering gear for automobiles makes use of a blank ( ) for the gear rack ( ) having at least in the latter's toothed area a form deviating from a circular cylinder. Size and form of the cross-section of the blank ( ) are selected in a manner that the contour of the finished gear rack ( ) in the toothed area ( ) does not project beyond the envelope given by the dimensions of neighboring parts of the rack-and-pinion steering gear. The gear rack ( ) is formed from the blank ( ) by means of tumble-forging. After tumble-forging, the gear rack ( ) in its toothed area ( ) outside the toothed section has a convex or concave longitudinal profile, which serves to support the tumbling torques during tumble-forging.

Method for producing a rack

A method for producing a blank for a gear rack for rack-and-pinion steering of motor vehicles includes the following steps: In a first step, a starting material having an essentially circular cross-section is placed into a stamping apparatus containing at least three form tools movable relatively to one another. In a second step, at least one force in at least one direction is exerted upon at least one of the form tools, the form tools moving relative to one another by this force, so that the starting material is reformed into a blank for the gear rack. At least in the axial region of the tooth system of the gear rack to be formed, the blank is provided with a shape differing from a circular cylinder. Using this method, part of the material of the starting material is displaced on one side from the middle into the region of the tooth system to be formed, without having much strain-hardening occur in this region. This makes subsequent production processes easier.

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Heubach, Germany

Alfred Brenner