Abstract:
In a threaded mechanism with rolling bodies comprising a spindle rod, a spindle nut at least partially enclosing said spindle rod, and a number of interposed rolling bodies, an axial and radial mounting support is provided for the spindle nut that is adapted to receive both tilting movements of the spindle nut about its longitudinal axis as well as radial movements transversely to its longitudinal axis.

Description:
TECHNICAL FIELD  
         [0001]    The present invention generally relates to threaded mechanisms and more particularly relates to threaded mechanisms with interposed rolling bodies.  
         BACKGROUND OF THE INVENTION  
         [0002]    Radial forces may be produced in threaded mechanisms with rolling bodies in different applications. In many applications, these radial forces, give rise to premature wear of the threaded mechanism. For example, in steering gears for vehicles, radial forces can act on the steering rod due to the travel-responsive inclined position of the steering tie rods coupled to the wheels, said radial forces producing friction forces in the bearings and cause the entire steering rod to deflect.  
         BRIEF SUMMARY OF THE INVENTION  
         [0003]    An object of the present invention is to develop a threaded mechanism with rolling bodies and a drive mechanism of an automotive vehicle axle guide module in such a manner that the mounting support of a spindle nut is exposed to an evenly distributed load.  
           [0004]    According to the invention, this object is achieved in that in a threaded mechanism with rolling bodies, which includes a spindle rod, a spindle nut enclosing the said spindle rod at least in part, and a number of interposed rolling bodies, there is provision of an axial and radial mounting support for the spindle nut that is so designed as to allow both tilting movements of the spindle nut about its longitudinal axis and radial movements transversely relative to its longitudinal axis.  
           [0005]    Consequently, it is essential for the threaded mechanism with rolling bodies of the invention that an axial and radial mounting support is provided for a spindle nut that is operatively connected to the spindle rod by the intermediary of rolling bodies, with said mounting support permitting tilting movements of the spindle nut about its longitudinal axis and radial movements of the spindle nut transversely relative to its longitudinal axis. Advantageously, the threaded mechanism with rolling bodies of the invention allows achieving an evenly distributed load on the mounting support. This means that defined flexibility is ensured and a defined radial clearance admitted in addition.  
           [0006]    In a preferred embodiment of the invention, at least one axial roller bearing is provided for the axial mounting support of the spindle nut having a radial flange, the frontal ends of which are designed as an abutment for the axial roller bearing. This renders it possible that the mounting support in the axial bearing is evenly loaded.  
           [0007]    According to a preferred embodiment of the invention, the axial mounting support is provided on a housing that is designed on facing frontal ends as an abutment for the axial roller bearing.  
           [0008]    According to a preferred embodiment of the invention, the housing includes two housing shells subdivided transversely relative to the axis of rotation of the threaded spindle, and each one axial roller bearing is interposed between the radial flange and each of the housing shells.  
           [0009]    The two housing shells accommodate the axial bearings in a clearance-free manner according to a favorable aspect of the invention.  
           [0010]    According to a favorable aspect of the invention, facing frontal ends of legs of the housing are configured as an abutment for axial bearing rings of the axial roller bearings.  
           [0011]    It is arranged for according to a preferred embodiment of the invention that the facing frontal ends of the legs include projecting, convexly shaped abutments for the axial bearing rings of the axial roller bearings. These abutments are used to ensure defined flexibility by permitting a defined tilting of the axial bearing rings and thus of the spindle nut.  
           [0012]    According to a preferred embodiment of the invention, the legs are elastically deflectable. Preferably, the legs and also the radial flange are elastically deflectable.  
           [0013]    A radial roller bearing is arranged for the radial mounting support of the spindle nut according to a preferred embodiment of the invention.  
           [0014]    According to a preferred embodiment of the invention, a bearing seat being designed on the housing is provided for the radial roller bearing, and a radial clearance is arranged between the bearing seat and the radial roller bearing.  
           [0015]    According to a preferred embodiment of the invention, a damping element for damping radial movements of the spindle nut is arranged between the housing and the radial roller bearing.  
           [0016]    According to a preferred embodiment of the invention, the bearing seat for the radial roller bearing has a hollow-cylindrical design and includes a circumferential groove housing a rubber-elastic, annularly closed damping element, which at least partly projects from the groove in a radially inward direction.  
           [0017]    According to a preferred embodiment of the invention, the rolling bodies of the threaded mechanism with rolling bodies have a spherical design.  
           [0018]    This object is likewise achieved by a drive device of an automotive vehicle axle guide module with a threaded mechanism with rolling bodies of the invention, being characterized in that the drive device includes a rotary drive that is connected to the spindle nut in terms of driving by way of a flexible torque clutch.  
           [0019]    According to a preferred embodiment of the invention, the threaded spindle of the threaded mechanism with rolling bodies is arranged in an axial direction behind a movable component of the automotive vehicle axle guide module that is connected or connectable to a steering wheel operable by a driver and, by displacement, effects turning of steerable vehicle wheels.  
           [0020]    According to a preferred embodiment of the invention, the movable component of the automotive vehicle axle guide module is a toothed rack to which the threaded spindle is rigidly connected.  
       
    
    
     BRIEF DESCRIPTION OF THE DRAWINGS  
       [0021]    [0021]FIG. 1 is the threaded mechanism of the present invention including rolling bodies along the longitudinal axis, with a cross-section taken through the spindle nut.  
         [0022]    [0022]FIG. 2 is a cross-sectional view of the threaded mechanism with rolling bodies shown in FIG. 1 transversely to the longitudinal axis in the area of the spindle nut.  
         [0023]    [0023]FIG. 3 is a perspective view of the threaded mechanism with rolling bodies shown in FIG. 1.  
         [0024]    [0024]FIG. 4 is a cutout of the threaded mechanism with rolling bodies shown in FIG. 1, with a cross-section taken through the spindle nut along the longitudinal axis of the threaded mechanism with rolling bodies.  
         [0025]    [0025]FIG. 5 is an enlarged view of a cutout of the spindle nut shown in FIG. 4.  
         [0026]    [0026]FIG. 6 is a schematic view of the possible movements of the threaded mechanism with rolling bodies. 
     
    
     DETAILED DESCRIPTION OF THE PREFERRED EMBODIMENTS  
       [0027]    The threaded mechanism with rolling bodies illustrated in FIG. 1, FIG. 2, and FIG. 3 is an independent functional subassembly wherein a spindle rod ( 1 ) could be part of a toothed rack subassembly of an automotive vehicle axle guide module. The threaded mechanism with rolling bodies comprises a ball screw ( 2 ) and spherical rolling bodies ( 3 ) between the spindle rod ( 1 ) and a spindle nut ( 4 ). It is used herein as a rotation/translation gear unit of the drive device of the axle guide module. The threaded mechanism with rolling bodies is designed by a corresponding mounting support ( 5 ) of the spindle nut ( 4 ) in such a manner that both tilting movements of the spindle nut ( 4 ) about its longitudinal axis and radial movements transversely relative to its longitudinal axis are permitted.  
         [0028]    The mounting support ( 5 ) of the spindle nut ( 4 ) is illustrated in detail in FIG. 4 and FIG. 5. The axial mounting support of the spindle nut ( 4 ) is carried out by means of two axial roller bearings ( 6 ) interposed between a radial flange ( 7 ) and two housing shells ( 8 ) subdivided transversely relative to the longitudinal axis of the threaded spindle ( 1 ). This mounting support is generally clearance-free. But a tilting movement of the spindle nut ( 4 ) about its longitudinal axis is rendered possible by legs ( 9 ) of the housing shells ( 8 ), which include convexly shaped abutments ( 10 ) for axial bearing rings ( 11 ) of the axial roller bearings ( 6 ), said abutments projecting from facing frontal ends of said legs. Legs ( 9 ) and, as the case may be, the radial flange ( 7 ) are elastically deflectable and permit tilting movement of the spindle nut ( 4 ) by tilting of the axial roller bearings ( 6 ) or the axial bearing rings ( 11 ) in the range of the elastic deformation. This achieves an elastic mounting support in contrast to a coaxial stiff connection to the spindle rod ( 1 ). The radial mounting support of the spindle nut ( 4 ) is carried out by means of a radial roller bearing ( 12 ), which is arranged on a bearing seat ( 13 ) designed on the housing shells ( 8 ), with a radial clearance (R) provided between the housing shells ( 8 ) and the radial roller bearing ( 12 ). Arranged between the housing shells ( 8 ) and the radial roller bearing ( 12 ) is a damping element ( 14 ) that is used, on the one hand, to prevent co-rotation of the housing shells ( 8 ) and thus to safeguard the function of the bearing and, on the other hand, serves for dampening radial movements of the spindle nut. The bearing seat ( 13 ) for the radial roller bearing ( 12 ) has a hollow-cylindrical design and includes a circumferential groove ( 15 ) in which the damping element ( 14 ) is incorporated. The damping element ( 14 ) is preferably an O-ring made of a rubber-elastic material and projects at least partly from said groove in a radially inward direction.  
         [0029]    As shown in FIG. 6, when the threaded mechanism of the present invention is incorporated into an automatic vehicle axle guide, the spindle rod ( 1 ) can deform, when exposed to the load of radial forces ( 17 ), and a corresponding elastic line ( 18 ) is produced. If the spindle rod ( 1 ) was hindered by a bending-resistant mounting support of the spindle nut ( 4 ) to effect a certain tilt ( 38 ) about the imaginary axis (X), very high radial forces would be exerted on the bearings due to the length of the bearing. These radial forces can cause a poor mechanical efficiency or lead to the destruction of individual components. In addition, an unsymmetrical load of the ball tracks ( 2 ) would occur in the screw thread shown in FIG. 1 and reduce the load capacities and useful life of the threaded mechanism.  
         [0030]    Induced by the elastic line ( 18 ), the axial roller bearings ( 6 ) and the axial bearing rings ( 11 ), due to the defined elastic deformability of the legs ( 9 ), will oscillate to balance the unsymmetrical stress, and the spindle nut ( 4 ) can align itself to the elastic line ( 18 ). As this occurs, the spherically and convexly configured abutment surfaces ( 10 ) of the legs ( 9 ) will transmit the acting axial force onto the axial roller bearings ( 6 ) always at a right angle and centrically through the axial bearing rings ( 11 ), also by deforming the legs ( 9 ) and possibly the radial flange ( 7 ). This renders the load on the rolling bodies ( 3 ) more uniform, increases their load capacity, the efficiency and total useful life of the axial roller bearings ( 6 ).  
         [0031]    The radial escape of the spindle rod ( 1 ) and the spindle nut ( 4 ) is intercepted by the integrated radial roller bearing ( 12 ) when an integrated clearance (R) is exceeded. The spindle rod is stabilized radially in its center when increased forces prevail. This is because the radial roller bearing ( 12 ), retained by the O-ring ( 14 ), runs without load in a defined range, dependent on clearance (R). As a whole, favorable improvements of the total efficiency and the response characteristic of the threaded spindle mechanism are achieved by the radial and flexible drive and bearing of the present invention. In order to ensure the zero backlash of the threaded mechanism with rolling bodies, the entire threaded mechanism is pre-assembled in a ring ( 16 ) with a defined preload of the two housing shells ( 8 ), thus forming a subassembly that is easy to integrate at a later time. The preload of the axial roller bearing ( 6 ) is preferably achieved by calking ring ( 16 ) within axial limits. Calking is limited by measuring the stall torque of the spindle nut ( 4 ). It is also possible to realize the connection by a screw coupling or other known types of connection. Ring ( 16 ) is stationarily fitted to the automotive vehicle axle guide module. The threaded mechanism with rolling bodies is then a subassembly of a drive device with a rotary drive that is connected in terms of driving to the spindle nut ( 4 ), preferably by way of a flexible torque clutch. The threaded spindle ( 1 ) of the threaded mechanism with rolling bodies is movable by the spindle nut ( 4 ), with the result that the toothed rack arranged behind it in an axial direction is entrained and brings about turning of steerable vehicle wheels.