Abstract:
In the case of a subassembly for a vehicle seat, in particular a fitting for a motor vehicle seat, having a first component ( 11 ) and having a second component ( 12, 21 ) which can move relative to the first component ( 11 ) and by means of regions ( 15, 17, 19 ) which are assigned to the first component ( 11 ) is mounted, guided and/or supported with respect to the first component ( 11 ) or interacts therewith in another manner, the first component ( 11 ) is at least partially hardened.

Description:
CROSS-REFERENCE TO RELATED APPLICATION 
     This is a continuation of PCT/EP02/03790, which was filed Apr. 5, 2002, published in German, and is entirely incorporated herein by reference. 
    
    
     BACKGROUND OF THE INVENTION 
     The present invention relates to a subassembly for a vehicle seat and, more particularly, to a fitting for a motor vehicle seat. 
     WO 00/44582 discloses a subassembly which is designed as a fitting and is provided as an inclination adjuster for the backrest of a vehicle seat. Frequent changes in the inclination of the backrest result in a certain amount of wear in the long term. 
     BRIEF SUMMARY OF THE INVENTION 
     One aspect of the present invention is the provision of an improved subassembly for a vehicle seat, in particular a fitting for a motor vehicle seat, having a first component and a second component which can move relative to the first component. By way of regions which are assigned to the first component, the second component is mounted, guided and/or supported with respect to the first component or interacts therewith in another manner. The first component is at least partially hardened. 
     By virtue of the first component (and preferably also the second component) being at least partially hardened, the wear behavior can be significantly improved and, by increasing the fatigue strength, the service life of the subassembly can be significantly increased. The clearance which is present is not enlarged, so that malfunctions of the fitting are avoided. In addition, a relatively high surface pressure is possible in the hardened regions, which increases the range of use of the fitting according to the invention. 
     In order to keep the increased outlay and production low in terms of costs and in order not to change the static and dynamic behavior of the component to a great extent, the first component is preferably hardened only in those regions which interact with components of the fitting which can move relative to the first component, for example the bearing and/or the guide and/or other supports, and, in particular, is preferably only hardened locally, i.e. on the bearing surfaces, guide surfaces, tooth surfaces and other supporting surfaces, and is otherwise unhardened. The reduction in the wear does not affect the geometrical qualities of these supporting surfaces. 
     In a particularly preferred embodiment, the hardened regions are specifically hardened in the boundary layer by means of a laser. In comparison with case hardening or induction hardening, this method has the advantage that a better dimensional stability can be obtained, that specific hardening with a defined hardening zone geometry can take place in certain regions, and that only a small distortion of the component occurs after cooling. Owing to the low drawing-in of heat, which is caused by the method, after the hardening process, the component can be immediately further processed. A quenching medium is not required, since automatic quenching takes place, i.e. the heat, which is introduced, is dissipated into the cold base material predominantly by thermal conduction. In addition, a more cost-effective use within a fully automatic installation system is possible. 
    
    
     BRIEF DESCRIPTION OF THE DRAWINGS 
     The invention is explained in greater detail below with reference to three exemplary embodiments illustrated in the drawing, in which: 
     FIG. 1 shows a view of a fitting lower part of the first exemplary embodiment, 
     FIG. 2 shows a section through the first exemplary embodiment, 
     FIG. 3 shows a vehicle seat equipped according to the invention, 
     FIG. 4 shows a section through a fitting upper part of the second exemplary embodiment, and 
     FIG. 5 shows a partial view of a third exemplary embodiment in the region of a bearing bushing. 
    
    
     DETAILED DESCRIPTION OF THE INVENTION 
     In the first exemplary embodiment, a vehicle seat  1  for a motor vehicle for the adjustment of the inclination of its backrest  3  has, as a subassembly on both of its sides, a respective fitting  5  which is designed as a latching fitting. The two fittings  5  are in a geared connection to each other by means of a transmission rod  7 . A hand lever  9 , which fits in a rotationally fixed manner on the transmission rod  7 , is used for the manual actuating of the fittings  5 . The following directional details refer to the cylinder coordinate system defined by the transmission rod  7 . 
     Each fitting  5  has a fitting lower part  11  as the first fitting part and a fitting upper part  12  as the second fitting part. The upper and lower parts  11 ,  12  are held together in the axial direction by retaining plates (not illustrated in detail). Four guide and bearing segments  15  of virtually quarter-circle-shaped profile are integrally formed on the fitting lower part  11 , which is fixed on the seat part. Each guide and bearing segment  15  has, radially on the outside, a narrow bearing surface  17  which is curved around the center of the fitting lower part  11 . The four bearing surfaces  17  together form a cylindrically shaped bearing surface, which is interrupted four times, for a correspondingly curved, radially inwardly pointing bearing surface of the fitting upper part  12  which is designed as a ring gear and is fixed on the backrest. Each guide and bearing segment  15  furthermore has a narrow, planar guide surface  19  running in the radial direction. Two guide surfaces  19  in each case together form a radial guide for a toothed segment  21  which is arranged such that it can move radially. 
     Each toothed segment  21  bears as a latch, a multiplicity of teeth on a side placed radially further outward, which teeth can interact with corresponding teeth of the fitting upper part  12  and the bearing surface thereof, in order to lock the fitting  5 . Two guide sides  23 , which run parallel to the radial direction, bear against the guide surfaces  19  of the associated two guide and bearing segments  15 . The radially inwardly placed side of the toothed segment  21  bears against an eccentric disk  25  having eccentrically curved clamping surfaces. The eccentric disk  25  is seated in a rotationally fixed manner on the transmission rod  7  by means of a bushing-shaped transmission element  27  and is prestressed in the circumferential direction by two spiral springs  29  in order to lock the fitting  5  by pressing on the toothed segments  21 . A driver disk (not illustrated for reasons of clarity) which is also seated in a rotationally fixed manner on the transmission rod  7  by means of the transmission element  27  and which interacts in a manner known per se with the two toothed segments  21  via pin-and-slot guides, is used for returning the toothed segments  21  inward in the radial direction, i.e. for the unlocking process which is initiated by a rotation of the transmission rod  7  by means of the hand lever  9 . 
     The four guide and bearing segments  15  are hardened locally in the region of their bearing surfaces  17  and their guide surfaces  19  including in each case a narrow, adjacent region, while the remaining regions and the fitting lower part  11  are unhardened, i.e. remain soft. The surfaces interacting with these surfaces, i.e. the internal toothing of the fitting upper part  12  and the guide sides  23  of the toothed segments  21 , can also be hardened. The hardening takes place by means of a laser. This method with a specific, local application of heat and integral quenching results in only a small distortion of a component. At the same time, the wear of the supporting surfaces in the case of frequent stress is greatly reduced, and higher surface pressures can be absorbed. 
     In the second exemplary embodiment, a fitting  105  has a fitting upper part  112  which is designed as a ring gear. For this purpose, the fitting upper part  112  has a radially inwardly pointing toothing  132  on the circumferential surface of a cup-shaped depression. The tooth flanks and tooth heads of the toothing  132  are laser hardened. Furthermore, the fitting upper part  112  has, in its center, a collar formation  134  which is used as a bearing and whose outer circumferential surface  134 ′ is likewise laser hardened. 
     The third exemplary embodiment relates to a wobble fitting  205  with a central free pivoting means which is placed on it and acts between a fitting upper part  212  and those parts of the wobble fitting  205  which contain the gear. For this function, a bearing bushing  240  is provided in the bearing of the fitting upper part  212 , said bushing having, on its radially outwardly pointing circumferential surface, three regions  240 ′ which are offset with respect to one another, slightly protrude radially and are laser hardened. 
     Unless explained in greater detail, the exemplary embodiments correspond or are designed in a manner known per se.