CROSS REFERENCE TO RELATED APPLICATIONS

This application is a U.S. National Stage Entry of International Patent Application Serial Number PCT/EP2019/069701, filed Jul. 22, 2019, which claims priority to German Patent Application No. DE 10 2018 212 202.4, filed Jul. 23, 2018, the entire contents of both of which are incorporated herein by reference.

FIELD

The present disclosure generally relates to a gear wheel for an adjustment drive mechanism which has a ring gear.

BACKGROUND

Steering columns for motor vehicles have a steering shaft with a steering spindle, a steering wheel for introducing a steering command by the driver being attached to the rear end thereof facing the driver in the direction of travel. The steering spindle is rotatably mounted about its longitudinal axis in a casing tube of an actuating unit which is retained by a support unit on the vehicle body. As the actuating unit has at least one casing tube which is displaceable in a telescopic manner in the direction of the longitudinal axis in a casing unit, which is connected to the support unit and which is also denoted as a guide box or boxed swing arm, a longitudinal adjustment of the steering wheel relative to the vehicle body may be carried out. A vertical adjustment may be implemented by the actuating unit or a casing unit receiving this actuating unit being pivotably mounted on the support unit. The adjustment of the actuating unit in the longitudinal and/or vertical direction permits the setting of an ergonomically comfortable steering wheel position relative to the driver position in the operating position, also denoted as the driving or operating position, in which a manual steering operation may be carried out.

In the case of motor-adjustable steering columns, it is known to provide a motorized adjustment drive mechanism with a drive unit for the adjustment, said drive unit comprising an electrical drive motor which drives a spindle drive with a threaded spindle screwed into an internal thread of a spindle nut. By means of the drive unit, the threaded spindle and the spindle nut are rotatably drivable relative to one another about the threaded spindle axis, or in short the spindle axis, whereby depending on the rotational direction the threaded spindle and the spindle nut may be moved in a translational manner toward one another or away from one another in the direction of the threaded spindle axis. The threaded spindle and the spindle nut are supported in the direction of the spindle axis on parts of the steering column which are adjustable relative to one another, for example on a casing unit and a support unit or on casing tubes of a casing unit which are telescopable in the axial direction.

The drive of the spindle drive is carried out by the drive unit via a gear wheel which is rotatably drivable about its axis, which is identical to the threaded spindle axis, and which is coupled to the spindle nut in a rotationally fixed manner. In the generic design forming the basis of the invention, the internal thread of the spindle nut is integrated in the gear wheel.

A generic gear wheel has a core element which bears a ring gear on the outside and forms, for example, a worm gear with a toothing into which a worm which is drivable by a drive motor engages in order to form a reduction gear. The internal thread may be configured in the core element as disclosed, for example, in U.S. Pat. No. 4,967,618. Alternatively, it is known that a core element consisting of metal has the ring gear on the outside and an axial passage opening on the inside, into which a threaded bushing is inserted as a threaded element, as disclosed for example in DE 38 86 900 T2. A drawback here is that this known threaded element first has to be manufactured separately as a separate component and then has to be joined and fixed to the core element. The required dimensionally accurate fit requires a correspondingly high degree of manufacturing effort. The assembly in the core element, in which a deformation or faulty alignment of the threaded element has to be avoided as far as possible, and the fixing by a material and/or positive connection, results in additional assembly effort. The load-bearing capacity and durability of the gear wheel may also be impaired by the joint.

Thus, a need exists for an improved gear wheel which requires less manufacturing and assembly effort and has a greater load-bearing capacity and durability.

