Abstract:
The invention relates to a method to manufacture a shaft ( 22 ) as well as a device containing such a shaft ( 22 ), in particular an armature shaft ( 22 ) of an electromotive drive ( 10 ), which is held by at least one shaft mounting, whereby a curved, rounded stopping tip ( 40 ) that can support itself on an axial stopping face ( 32, 34 ) is formed at least one fore part ( 28, 30 ) of the shaft ( 22 ) by means of material displacement.

Description:
RELATED APPLICATION 
     This application is a 35 USC 371 of International Application No. PCT/DE03/01599, filed May 19, 2003. 
     BACKGROUND OF THE INVENTION 
     The invention relates to a method to manufacture a shaft with rounded stopping tips as well as a device containing such a shaft, as well as a device to manufacture such a shaft in accordance with the species of the independent claims. 
     With WO 01/65 668, a device has become known that is used, for example, to move window panes, sun roofs or seats. In order to avoid undesired longitudinal play in the armature shaft, it is proposed there that a damping rubber piece be pressed into a recess of the housing on at least one of the fore parts. The armature shaft features a rounded stopping tip on one of its fore parts, which is supported against a stop disk, which is pressed in turn against the damping rubber piece. 
     This type of rounded stopping tip is normally manufactured by means of turning on a lathe or grinding in a machining process on the fore part of the armature shaft before installation of the electric motor. Afterwards, the rounded stopping tip is polished in order to achieve a high surface quality and then hardened so that the rounded stopping tip does not get damaged when the electric motor is assembled. This method is very labor intensive and expensive. 
     SUMMARY OF THE INVENTION 
     The method in accordance with the invention has the advantage that a high-quality and wear-resistant surface is created when forming a rounded stopping tip by means of cold forming in one work step. It is possible to completely dispense with the process steps of polishing and hardening since, on the one hand, the surface is created in one work step by means of material displacements and, on the other hand, this procedural step can be conducted in a favorable manner after assembly of the armature. 
     Advantageous further developments of the method are possible. In terms of manufacturing techniques, it is especially simple to perform the material deformation by means of a roller-burnishing process in which a rotating rolling tool rolls on the shaft. A very dimensionally accurate, rotationally symmetrical rounded stopping tip can be manufactured as a result. In addition, a long tool service life and a smooth work piece surface are achieved because of the rolling off of the tool. 
     To manufacture the rounded stopping tip on an assembly line, it is advantageous to secure the shaft with a gripper and adjust a rotating deformation roller with an axial working surface. A radius is then formed on the fore part of the shaft because of the tilting of the axis of the deformation roller, vis-à-vis the shaft axis. 
     The material deformation takes place during the tilting of the deformation roller on a spiral-shaped line so that with increased tilting of the material of the shaft there is continuous displacement in the radial and axial direction. This continuous flow process creates a very smooth and hard surface of the rounded stopping tip. 
     Due to the selection of the crossing point of the shaft axis with the axis of the deformation roller when tilting the same, the radius of the rounded stopping tip can be produced in accordance with the requirements of the axial mounting of the shaft. As a result, any desired radii can be formed with one working surface of the deformation roller. Before assembly of the armature shaft on its fore part, a phase is manufactured, through which the diameter of the rounded stopping tip can be prescribed in connection with the pressing force of the deformation roller against the shaft. The phase guarantees that the shaft material can yield during its deformation, thereby reducing deformation volume and deformation time. 
     It is favorable not to execute the rounded stopping tip until an advanced assembly stage of the electric motor after various components have already been fixed to the armature shaft since then the surface of the rounded stopping tip can no longer be damaged during further assembly. 
     On the other hand, it is advantageous to form the rounded stopping tip before rolling a worm on the shaft, since then the worm cannot be damaged with acceptance into the deformation head during manufacture of the rounded stopping tip or when fixing the armature shaft. 
     A device, in accordance with another embodiment of the invention to adjust movable parts in motor vehicles, has the advantage that a cost-effective axial mounting of the armature shaft, which is wear-resistant over long service lives with a surface roughness of the rounded stopping tip of less than one micrometer, is realized with the rounded stopping tips formed by means of a deformation roller. 
     A device, in accordance with another embodiment of the invention, has the advantage that it can be favorably integrated procedurally into an assembly line due to the axial adjustment and tilting of the deformation roller, vis-à-vis the rotational axis. 
    
    
     
       BRIEF DESCRIPTION OF THE DRAWINGS 
       Exemplary embodiments of the devices in accordance with the invention are depicted in the drawing and explained in more detail in the following description. The drawings show: 
         FIG. 1  A section of a device to adjust movable arranged parts. 
         FIG. 2  A device to manufacture a shaft according to the method in accordance with the invention 
         FIG. 3  An enlarged detail of the rounded stopping tip in  FIG. 2 . 
     
    
    
     DETAILED DESCRIPTION 
       FIG. 1  shows an adjusting drive  10 , with a motor  12  and a multipart housing  16  surrounding a gear  14 . The motor  12  is electrically commutated and features an armature  18 , a commutator  20  and a multiply positioned armature shaft  22 , which extends into the area of the gear  14 . A worm  26 , which communicates with a worm wheel  24  via gear toothing  25 , is arranged on the armature shaft  22 . This is supported on the fore parts  28  and  30  of the armature shaft  22  in the longitudinal direction via stop disks  32  and  34 , as well as via a damping rubber piece  36  on the housing  16 , or a portion of the same. A rounded stopping tip  40  is formed on one end  38  of the armature shaft  22  by means of material displacement. The radius  42  of the rounded stopping tip  40  determines the size of the surface with which the armature shaft  22  is pressed against the stop disk  32 . The smaller this surface is, the smaller the frictional losses; however, wear increases with a diminishing stopping face. As a result, the radius  42  of the rounded stopping tip  40  is specified in such a way that a good compromise is achieved between low friction and low wear. In addition, such a great tip height of the rounded stopping tip  40  is selected via the radius  42  that during the entire service life, the rounded stopping tip  40  does not sink too deep into the stop disk  32  (which for the most part is manufactured of plastic), and that the tip edges  41 , which delimit the radius  42  of the rounded stopping tip  40 , touch the stop disk  32 . 
       FIG. 2  depicts the method in accordance with the invention on the basis of a device to manufacture a shaft  22 . Several components  44 , such as an armature  18 , a commutator  20  or a ring magnet  21  are already pre-mounted on the shaft  22  before the armature shaft  22  is held for example by means of a gripper (not shown) having, for example, a pivoted guide bush to receive the shaft  22 . The deformation device  50  is composed essentially of a drive  52 , which allows a deformation head  54  to rotate. A deformation roller  56  is arranged in the deformation head  54  on a central rotational axis  58 . The deformation head  54  can be fed in the axially direction  63  by means of an adjusting unit  60  and the deformation roller  56  can be tilted vis-à-vis the central rotational axis  58  of the deformation head  54  via a reversing lever  62 . In this exemplary embodiment, the rotational axis  58  lies congruent with an axis  64  of the armature shaft  22 . While the deformation head  54  rotates around the rotational axis  58 , the deformation roller  56  is set against the fore part  28  of the armature shaft  22  and the deformation roller  56  is tilted vis-à-vis the axis  64  of the armature shaft  22 . As a result, the deformation roller  56  touches the armature shaft  22  with an axial working surface  66  in a punctiform deformation area  68 , which during the rotation runs in accordance with arrow direction  55  and during tilting of the working surface  66  in accordance with arrow direction  80  on a spiral-shaped line. In this connection, the material of the armature shaft  22  is displaced from the axis  64  radially towards the outside and axially towards the armature  18 , whereby a curved surface of a rounded stopping tip  40  is formed on the armature shaft  22 . The cold forming of the material produces a compression of the surface material and therefore a surface roughness of less than 1 micrometer. 
       FIG. 3  shows an enlarged detail of the rounded stopping tip  40  in  FIG. 2 , whereby a phase  70  is manufactured on the armature shaft  22  before forming a rounded stopping tip, which phase permits a corresponding clearance zone  71  for the material deformation by the deformation roller  56 . The phase  70  in the exemplary embodiment is executed in two stages, but can just as well be manufactured as a continuous phase  70 . The radial extension  72  of the phase  70  specifies, within certain limits and in connection with the to-be-applied application force of the deformation roller  56 , a diameter  74  (of 3 to 4 millimeters for example) of the rounded stopping tip  40  since the material cannot be reformed to any width in the clearance zone  71  of the phase  70 . The curvature of the surface of the rounded stopping tip  40  has a radius  76 , which is created by tilting the axial working surface  66  of the deformation roller  56  around a tilting point  78  on the axis  64  of the armature shaft  22  in accordance with arrow direction  80 . In this connection, the deformation roller  56  is tilted in accordance with arrow direction  80 , e.g., over an angle range  82  from −5° or +20°. The radius  76  is usually smaller than the swivel radius of the deformation roller  56  since the shaft  22  is subject to axial tension during the deformation process and is permanently pressed back. 
     In another variation of the method, a rotating deformation roller  56  is attached in a stationary manner and the fore part  28  of the shaft  22  is pressed against the working surface  66  of the deformation roller  56  and tilted vis-à-vis the shaft axis  64  by a tilting angle  82 . 
     In another alternative of the method, the shaft  22  rotates around its axis  64  and is set against the stationary working surface  66  of the deformation roller  56  and either the armature shaft  22  or the deformation roller  56  is tilted by a tilting angle  82 . 
     In the case of these variations of the method in accordance with the invention, what matters is that the fore part  28  of the shaft  22  is rotated against a working surface  66  and these two surfaces are continuously tilted against one another. As a result, a high-quality surface of a rounded stopping tip  40  is generated by means of material displacement, which rounded stopping tip can be formed on one or both ends  38 ,  39 . 
     In another exemplary embodiment, as the method of material displacement, a curved stamping tool is moved under pressure against the fore part  28 ,  30  of the shaft  22 , whereby this does not necessarily have to be a pure rotational movement. 
     It is preferred that the method in accordance with the invention be used for manufacturing an electric gear/drive unit, but it is not limited to this. The invention also includes individual features of the exemplary embodiments or any combination of the features of the different exemplary embodiments.