Abstract:
An electrically adjustable steering column includes a steering column servo-drive with a motor in two planes. The steering column is configured so that an inner shaft, mounted in an outer shaft provides for vertical movement or so that the inner shaft accomplishes the lengthwise movement.

Description:
FIELD OF THE INVENTION 
   The invention concerns an electrically adjustable steering column, especially an electrically adjustable steering column in two planes with a motor, and a method of operation for it. 
   BACKGROUND OF THE INVENTION 
   In order to adjust a secure and comfortable position, steering columns of passenger cars are often adjustable in height and length in the prior art. In versions with electrical servo-motors, one motor is customarily used for each direction of adjustment. 
   Zahnradfabrik Friedrichshafen, based on practical experience, uses one motor and one shaft and employs electromagnets to couple each threaded nut indicating the steering wheel inclination and the forward/backward position. 
   The Elba company of Bremen, in a steering column with two flexible shafts of the prior art, whose drive unit is switched on and off with a coupling, engages the two directions of adjustment forward or back. 
   The goal of the present invention, which it achieves, is to improve the existing technique. 
   Furthermore, the present invention advantageously creates more cost-favorable and simple alternatives with respect to the embodiments of the prior art. 
   SUMMARY OF THE INVENTION 
   The present invention creates an electrically adjustable steering column and an operating method for it, configured with a steering column adjustment drive with a motor in two planes, such that one shaft, mounted in the second shaft, preferably provides for the height adjustment, or such that the inner shaft accomplishes the lengthwise adjustment. 
   In a preferable modification of the invention, the steering column adjustment drive is configured such that both shafts, which can turn but are otherwise stationary, are each provided with a pinion. This can advantageously be modified so that the shaft pinions mesh with pinions of a ratchet mechanism, which accomplishes the vertical or lengthwise movement of a steering column in both directions of turning. 
   Furthermore, it is preferable to modify the electrically adjustable steering column and its operating method so that a bent lever system is provided for the vertical adjustment and is preferably geometrically configured so that the drive shafts can be fixed stationary on the steering column bearing. 
   Yet another preferred embodiment of the device and method of the invention consists in a transfer of motion by bent lever to the opposite side, so that a perfectly nonconstrained and “stable” adjustment is achieved. 
   Benefits of the invention are, in particular,
         a stable drive system for the steering wheel adjustment, since the shafts are mounted to be stationary,   a simple construction, since the shafts are nested one inside the other,   the possibility of favorably achieving an advantageous and especially necessary crash resistance, since the two shafts [nested] one inside the other prevent any “buckling,”   an easier mounting of the shafts “nested,” than when mounted separately,   less room required for the nested shafts,   lower weight, and   lower costs.       

   In particular, and advantageously, the present invention thus creates, both in device and in method, a simple system with two threaded spindles, which are stationary and rotate one inside the other, for the lengthwise and vertical adjustment of a steering column with only one motor and one ratchet mechanism. 
   Preferred and/or advantageous embodiments of the invention result from the claims and combinations thereof, as well as from the overall application documents submitted. 

   
     BRIEF DESCRIPTION OF THE FIGURES 
       FIG. 1  shows a steering column tube according to the present invention. 
       FIG. 2  shows in cross section A—A of  FIG. 1 . 
   

   DETAILED DESCRIPTION OF THE INVENTION 
   The invention shall now be explained more closely by means of sample embodiments, making reference to the drawings. 
   The invention is only illustrated as an example by means of the embodiment and application examples described hereafter and presented in the drawings. Method and device features shall also appear from the device and method descriptions. 
   The same reference numbers in the individual figures and images of the drawings designate the same or similar components, or those with the same or similar action. The representations in the drawing also indicate features not provided with reference numbers, whether or not such features are subsequently described. On the other hand, features are also contained in the present description, yet do not appear or are not represented in the drawing, but are easily understandable to a person skilled in the art. 
   Individual features indicated and/or represented in connection with specific embodiments are not limited to these embodiments or a combination with the other features of these embodiments, but rather can be combined insofar as is technically possible with any other variants, even if not specifically treated in the present documents. 
     FIG. 1  shows a steering column tube  1 , which is mounted in a steering column bearing  2 . The steering column bearing  2  is hinged by joints/bearings  3  to a fastening plate  9 , so that the steering column bearing  2  can pivot at the forward point and levers  4  are arranged at the rear point, being linked in turn as double bent levers to a nut  5 . The fastening plate  9  is secured to the body  10 , as usual. 
   For the adjustment of the steering column tube  1 , there is provided a drive shaft  6 , which is mounted at one end on the steering column bearing  2  by means of a bearing  8  in a “fixed bearing”  7 , so that it can turn but not move lengthwise. This drive shaft  6  is fixed to the steering column tube  1  by means of a pillow block  11 , in which a drive nut  12 , such as one made from brass, POM, or sintered material, is accommodated. On the drive shaft  6 , moreover, there is secured a drive pinion  13 , which is powered by a pinion  14  from a ratchet and stepdown gearing mechanism  15 . 
   For the lengthwise adjusting motion, a motor  21  drives the shaft  6  with a pinion  14 . Since the drive nut  12  is firmly mounted in the pillow block  11 , the steering column tube  1  moves forward or backward according to the direction of turning of the pinion  14 . 
   On the lengthwise adjustment drive shaft  6 , a hollow drive shaft  16  is mounted for the vertical adjustment, which can rotate independently. As an alternative, the forward bearing  17  of this drive shaft  16  and the drive pinion  13  can be made from a single piece. On the vertical adjustment drive shaft  16 , a drive pinion  18  is secured, which draws its motion from the ratchet and stepdown gearing mechanism  15  depending on the set position and transfers it via a pinion  14 . 
   The vertical adjustment drive shaft  16  has a thread  19  on its outer diameter. This thread  19  turns in the nut  5  and thus moves the bent levers  4 , which produce a swivel motion of the steering column bearing  2  by their geometrical arrangement. The lower lever  4  of the bent lever system is secured at the side of the steering column bearing  2 , as shown. 
     FIG. 2  shows in cross section A—A of  FIG. 1  the arrangement of the bent levers  4  and their transmission to the other side of the steering column tube  1  by means of an axle  20 , on either side of which the pairs of bent levers  4  are secured. The axle  20  is mounted in joints/bearings  3 , which are secured to the fastening plate  9 . 
   The shafts  6  and  16 , furthermore, can also alternatively and additionally be designed as crash load absorbers in advantageous and preferred manner. 
   The invention is presented merely as an example by means of the embodiments in the specification and the drawings and is not confined to them, but rather encompasses all variations, modifications, substitutions and combinations that a person skilled in the art will find in the present documents, especially in the context of the claims and the general representations in the introduction to this specification and the description of the embodiments and their representations in the drawings and that he can combine with his technical know-how as well as with the prior art. In particular, every individual feature and possible configuration of the invention and its embodiments can be combined. 
   LIST OF REFERENCE NUMBERS  
   
       
         1  Steering column tube 
         2  Steering column bearing 
         3  Joints/bearings 
         4  Lever 
         5  Nut 
         6  Lengthwise adjustment drive shaft 
         7  Fixed bearing 
         8  Bearing 
         9  Fastening plate 
         10  Vehicle body 
         11  Pillow block 
         12  Drive nut 
         13  Drive pinion for lengthwise adjustment 
         14  Pinion 
         15  Ratchet and stepdown gear mechanism 
         16  Drive shaft for vertical adjustment 
         17  Drive shaft bearing 
         18  Drive pinion for vertical adjustment 
         19  Vertical adjustment thread 
         20  Axle