Rack and pinion steering, especially for motor vehicles

Abstract

Rack and pinion steering for motor vehicles with a rotatably mounted steering pinion which engages via a toothing in a toothed region of a rack (10) such that a rotation of the steering pinion leads to a displacement of the rack (10) in the direction of its longitudinal axis, wherein the rack (10) is guided longitudinally displaceably in a steering housing (20) and is mounted within the steering housing (20) via at least one support bearing which comprises at least two support bearing halves (30; 30'), between which the rack (10) is movably guided, in that at least one support bearing half (30; 30') has a bearing surface (31; 31') on which the rack (10) rests, and in that at least this support bearing half (30; 30') is designed to be movable within the steering housing (20) and clamping means (40) are provided which exert a force at least on the movable Apply the support bearing half (30;30') in such a way that its bearing surface (31;31') is movable in the direction of the other support bearing half (30; 30'), which in this case serves as a counter bearing, whereby the two support bearing halves (30; 30') exert a force in the direction of the steering pinion on the rack (10) through the interaction of their geometries at least via the support surface (31; 31') of the movable support bearing half (30; 30'), characterized in that the clamping means (40) applies a force at least to the movable support bearing half (30; 30') on the side of the rack (10) opposite the support point between the at least one support bearing half (30; 30') and the rack (10), and that the two support bearing halves (30; 30') are designed such that they can overlap in the region of the support point of the rack (10).

Description

The present invention relates to a rack and pinion steering system for motor vehicles according to the preamble of claim 1.Rack and pinion steering systems of this type have long been used in motor vehicle technology. In rack and pinion steering systems, the steering torque is generally introduced into the steering system from the steering wheel via a steering column and a steering pinion. The steering pinion engages a toothed section of a toothed rack and converts the rotational movement of the steering wheel into a usually horizontal linear movement for pivoting the steered wheels.From DE 691 03 226 T2 a rack and pinion steering of the generic type for motor vehicles is known.It is known to mount the rack in a steering housing so as to be longitudinally displaceable with two bearing points. For example, the published patent application DE 101 18 642 A1 discloses such a rack and pinion steering system with two bearing points in the form of linear rolling bearings. A first bearing point is located in the end region of the steering housing and a second bearing point is overlapped with the toothed region of the toothed rack to form the steering pinion.Patent document DE 10 2006 011 752 B3 also discloses a rack and pinion steering system with a rack in a steering housing, wherein the rack is mounted with a low-friction bearing and at least one roller bearing is provided on the steering housing in a bearing region for longitudinally displaceable mounting of the rack. At least one axially extending slot is formed in the steering housing in the bearing region, and means are provided for changing the slot width for setting the bearing play with respect to the toothed rack.The steering pinion and the toothed rack must not have any noticeable play in engagement, or the play between the teeth of the toothed rack and the steering pinion should be adjustable and also adjustable as far as possible. For this purpose, for example, a pressure piece is used which presses the toothed rack against the tooth forces acting during operation on the pinion. This pressure piece is elastically mounted and usually loaded with a spring in order to compensate for the height tolerances in the toothing of pinion and rack, which tolerances are caused by the production.Since, in the event of strong impacts, the forces which drive the steering pinion and the toothed rack apart exceed the forces of the spring element, an end stop is provided which is usually formed by the side of the pressure piece facing away from the toothed rack. Usually, the spring is also located on this side of the pressure piece. In the case of normal loading, therefore, only the pressure piece is pressed against a stationary surface via the spring and is correspondingly driven back again in the event of a change in loading. In the case of very high forces and in the case of impact loads, the spring force is overcome and the rear side of the pressure piece comes into contact with the stationary, opposite surface, as a result of which a further movement of the pressure piece is ruled out. The movement of the pressure piece is thus adjustable by means of the spring force and the gap dimension relative to the stationary surface, wherein a distance of approximately 0.15-0.2 mm has proven sufficient.A pressure piece can also cooperate with sliding blocks, the surfaces of which are adapted to the contour of the toothed rack and are pressed against the toothed rack. For example, the published patent application DE 197 17 797 A1 discloses a rack-and-pinion steering system with a pressure piece which has two slots transversely to the longitudinal axis of the rack, in which slide blocks are guided, one base surface of which is matched to the inclined base surface of the pressure piece, the other inclined base surface of which is matched to the contour of the rack and the radially outer surface of which is matched to a pressure piece bore. Furthermore, it can be provided to press a toothed rack against the steering pinion via eccentrics or inclined planes.However, a significant problem, particularly when using pressure pieces and / or sliding blocks, is the generation of noise. Because the steering pinion strikes against the toothed rack and the pressure piece strikes against the stationary surface, considerable noise is generated. This is the case in particular when electromechanically reinforced steering systems are used, so-called EPAS systems. In such systems, the steering pinion has to bear the entire load of the rack, so that separation forces are significantly higher than, for example, in hydraulically operated steering systems. This means that even with low rack forces, high forces act on the spring element.In particular, mechanical steering gears are simultaneously subject to ever higher demands on the NVH (noise-vibration-severity) behavior. Since these steering gears do not have damping hydraulics and significantly higher loads in the toothing region, special measures are required here.The object of the present invention is therefore to provide a rack and pinion steering system for motor vehicles which can be produced as wear-free and cost-effectively as possible and which has as little noise generation as possible during operation.According to the invention, this object is achieved by a rack and pinion steering system according to independent claim 1. Advantageous further developments of the rack and pinion steering system are described in dependent claims 2-19.According to the preamble of claim 1, the invention relates to a rack and pinion steering system for motor vehicles having a rotatably mounted steering pinion which engages via a toothing system into a toothed region of a rack in such a way that a rotation of the steering pinion leads to a displacement of the rack in the direction of its longitudinal axis. The rack is guided in a longitudinally displaceable manner in a steering housing. According to the invention, the rack is mounted within the steering housing via at least one support bearing which comprises at least two support bearing halves, between which the rack is movably guided. This guidance is realized in that at least one support bearing half has a support surface on which the toothed rack rests. Furthermore, at least this support bearing half is designed to be movable within the steering housing, and clamping means are provided which apply a force at least to this movable support bearing half in such a way that its bearing surface can be moved in the direction of the other support bearing half, which in this case serves as a counter bearing. As a result, the two support bearing halves exert a force on the rack in the direction of the steering pinion by the interaction of their geometries at least via the bearing surface of the movable support bearing half. The force of the clamping means preferably acts constantly on the at least one movable support bearing half, wherein the magnitude of the force does not have to be constant, since this can change during the course of the operation of the bearing. Rather, a force acting constantly in the sense of this invention means that the force acts permanently on the at least one movable support bearing half during operation of the bearing.The movement of the at least one support bearing half is preferably a rotational or tilting movement about an axis which runs parallel to the longitudinal axis of the steering housing and thus also to the longitudinal axis of the toothed rack. The support bearing half abuts the inner side of the steering housing and slides along this inner side of the steering housing into another angular position with respect to a plane through the longitudinal axis of the toothed rack. Since the rack is preferably located eccentrically within the steering housing, the axis of rotation or tilting does not correspond to the longitudinal axis of the steering housing, but rather runs parallel to the latter. In this case, the rotation / tilting axis can also be displaced during the movement, so that the at least one support bearing half is rotated and displaced during its movement.The required force in the direction of the steering pinion is effected by the special geometry of the two cooperating support bearing halves, in that a movement of the at least one movable support bearing half within the steering housing has the result that the bearing surface of this support bearing half moves in the direction of the other support bearing half and in the process changes its position, for example by a rotational movement, such that it moves / presses the toothed rack against the steering pinion in cooperation with the geometry of the other support bearing half. In this case, the angle between the bearing surface and a plane through the longitudinal axis of the toothed rack preferably changes, and the other support bearing half, toward which the movable bearing surface moves, serves as a fixed or likewise movable counter bearing. The counter bearing then either only prevents the rack from sliding laterally off the bearing surface of the other support bearing half, or it contributes, for example, by means of an oblique stop surface to the movement of the rack in the direction of the steering pinion. At least one bearing point of the toothed rack on a bearing surface moves in the direction of the steering pinion.Once the rack abuts the steering pinion, it is constantly pressed against the steering pinion under the bias of the clamping means, so that there is no appreciable play in engagement. Thus, static manufacturing tolerances can be compensated in a simple manner. Dynamic manufacturing tolerances can be compensated for, for example, by an elastic material on the inner side of the steering housing and / or of the bearing and / or by the elasticity of the toothed rack. The Rubore® product can be used in particular as elastic material, but other materials can also be used. In addition, dynamic manufacturing tolerances can also be compensated for by selecting a flexible or preferably elastic material as the material for manufacturing the bearing. Thus, the bearing is inherently flexible.Furthermore, high demands on the NVH behavior of the associated steering gear can be fulfilled, since undesired noise generation can be significantly reduced or does not occur as a result of the design according to the invention. Even in the event of wear of the rack and / or of the steering pinion during operation of the associated steering gear, the wear can be compensated for by an adapted displacement of the position of the rack in the direction of the steering pinion, so that no undesired play arises even then. The geometries of the two support bearing halves together with the force of the clamping means cause the toothed rack to move closer to the steering pinion in order to successively compensate for play occurring as a result of closing or not to let it first occur. For this purpose, no separate mechanisms for adjusting the play need be present, but the readjustment is effected automatically by the constantly applied force of the clamping means.It is advantageous that in particular no sliding blocks are used, because the rack and pinion steering system according to the invention provides fewer components compared to embodiments with sliding blocks, and manufacturing and assembly steps can also be saved.In one exemplary embodiment of the invention, the at least two support bearing halves each have a support surface which together form a support region, and the toothed rack lies in this support region on the two support surfaces. Thus, the two bearing surfaces can jointly exert a force on the rack in the direction of the steering pinion due to the interaction of the geometries of the two support bearing halves. At least one of the bearing surfaces is pressed in the direction of the other and thereby changes its position within the steering housing.Preferably, the support surfaces of the two support bearing halves extend in the support region on the side of the rack at an angle α of <180° to one another. The rack thus rests in a kind of depression or funnel which is formed by the two bearing surfaces. In a preferred embodiment of the invention, the rack is arranged eccentrically within the steering housing. The support bearing halves are preferably designed such that in the installed position a self-locking angle results from the contact rod with the toothed rack. This ensures that the bearing surfaces and thus the support bearing halves are not pressed apart by the weight of the rack or by a force introduced from the outside via, for example, the tie rods, because otherwise the rack could move away from the steering pinion. The geometry of the support bearing halves can consequently be configured such that, owing to self-locking angles, readjustment of the toothed rack is possible only in the direction of the steering pinion.The rack rests on the two support surfaces at one point each, and when at least the movable support bearing half moves toward the other support bearing half, the position of these support points changes in the direction of the steering pinion. As a result, the rack moves closer to the steering pinion or is pressed against the steering pinion.The rack and pinion steering system can have one or more such support bearings, comprising at least two support bearing halves. In one embodiment of the invention, at least two support bearing halves are provided per support bearing, but this number can also be increased, so that three or more support bearing halves can also hold one toothed rack. Of these, at least one support bearing half is then designed to be movable within the steering housing.For the mode of operation of the invention, at least one support bearing half must be designed to be movable within the steering housing, while the other support bearing half can be fixedly attached to the steering housing. The clamping means then move the movable support bearing half within the steering housing in such a way that its bearing surface moves in the direction of the stationary support bearing half and interacts with the geometry of the stationary support bearing half.In a preferred exemplary embodiment of the invention, however, both support bearing halves are designed to be movable within the steering housing, such that the toothed rack is guided between two movable support bearing halves, preferably each with a bearing surface. By the force of the clamping means, the bearing surfaces of the two support bearing halves can be simultaneously moved toward one another. Both bearing surfaces can thus move towards one another in opposite directions, but they do not necessarily have to cover the same distance. Rather, the rotation of one support bearing half can be stronger than that of the other support bearing half.Preferably, the two support bearing halves are substantially mirror-symmetrical with respect to the longitudinal axis of the toothed rack. However, there may be slight deviations which do not influence the basic configuration of the two support bearing halves. An axially offset arrangement of a plurality of mirror-symmetrical support bearing halves along the toothed rack is also possible.Various components can be used as clamping means. Preferably, however, the clamping means comprise at least one spring, wherein it can be an elastomer spring, for example. This spring can be, for example, a compression spring which is arranged and clamped between the two support bearing halves in such a way that the two support bearing halves are pressed apart at one point by their force. As a result, at least one of the support bearing halves rotates within the steering housing in such a way that its bearing surface moves in the direction of the other support bearing half. The spring acts together with the geometry of the support bearing halves, because the support bearing halves are adapted to the shape of the steering housing in such a way that the bearing surface of the at least one movable support bearing half moves in the direction of the other support bearing half when they are pressed apart at a specific point by the spring. Thus, for example, these are opposing movements with respect to a rotation / tilting axis. However, the compression spring can also be mounted in such a way that the bearing surface of a movable support bearing half can be pressed directly in the direction of the other support bearing half by its pressure force.The limitation by the steering housing preferably leads to a guided movement of at least one support bearing half within the steering housing. For this guided movement of at least one support bearing half which is configured to be movable within the steering housing, the latter can be designed, for example, in the form of a shell, wherein the outward curvature of the support bearing half corresponds substantially to the inward curvature of the steering housing. This at least one support bearing half is supported in a planar manner on the inner side of the steering housing, so that it can slide off the steering housing during its movement and is forced into a rotational or tilting movement when the support bearing halves are pressed apart in a region by the clamping means. The bearing surface of such a support bearing half is then preferably formed on the inward curvature of the support bearing half.At least two such cup-shaped support bearing halves may be provided to receive the rack between its opposed inward bulges, wherein both cups may be made movable. When the bearing surfaces move towards one another, the bearing points of the toothed rack on the bearing surfaces change in the direction of the steering pinion, whereby the toothed rack is raised or pressed against the steering pinion.However, one of the shell-shaped support bearing halves can also be fixed and / or, for example, can also be combined with other forms of support bearing halves. For example, at least one support bearing half which is stationary or is configured to be movable within the steering housing can be of hook-shaped design, wherein it has a bracket from which a support surface projects at an angle in the direction of the toothed rack. The toothed rack is then guided between this bracket and a shell-shaped support bearing half and rests, for example, on two inwardly projecting bearing surfaces. The rack can also be held by at least two such hook-shaped support bearing halves without shell-shaped support bearing halves being provided.In one exemplary embodiment of the invention, at least one support bearing half, which is designed to be movable within the steering housing, is supported on the inner side of the steering housing via at least two points. In the case of a hook-shaped support bearing half having a bracket and a supporting surface projecting therefrom, said support bearing half can be supported, for example, at least via its bracket and its supporting surface on the inner side of the steering housing. However, further support points or surfaces can also be present.In the case of a hook-shaped support bearing half, a compression spring can be clamped as clamping means, for example, between the two brackets of the support bearing halves. The geometry then causes the contact surfaces protruding inward from the brackets to move toward each other when the compression spring presses the brackets of the two support bearing halves apart. For this purpose, at least one support bearing half can have a clamping region which is designed to support the clamping means. Thus, a spring can be introduced into a receptacle, for example, and can also be fastened there, if appropriate.In all exemplary embodiments of the invention, bearing surfaces can be designed to be concave or straight. Furthermore, the bearing surfaces can be comb-shaped at least in regions, wherein the comb-shaped regions of the two support bearing halves can engage one another in a support region. The comb regions are then designed or the two support bearing halves are arranged with respect to one another such that the teeth of the comb regions slide past one another when the contact surfaces engage one another. Thus, the bearing surfaces can overlap and shift the bearing points of the toothed rack on the bearing surfaces in the direction of the steering pinion without the two support bearing halves abutting each other in the support region. This can also be achieved in that the two support bearing halves are arranged axially offset along the longitudinal axis of the steering housing, so that in the overlap region one support bearing half can slide laterally along another support bearing half without the two support bearing halves abutting each other in the support region.In one exemplary embodiment, the rack is arranged eccentrically within the steering housing. In addition, the geometry of the support bearing halves is preferably designed such that, owing to self-locking angles, readjustment of the toothed rack is possible only in the direction of the steering pinion.In order to compensate for dynamic manufacturing tolerances, it can furthermore be provided that the inner side of the steering housing and / or the inner side of at least one of the support bearing halves is provided with an elastic material. In addition, at least one of the support bearing halves can itself be produced from an elastic material.Further advantages, special features and practical further developments of the invention are evident from the dependent claims and the following description of preferred exemplary embodiments with reference to the figures.The figures show: FIG. 1 ashows a first exemplary embodiment of a support bearing with a schematic cross section through a steering housing with two shell-shaped support bearing halves in a first position; FIG. 1 bshows the exemplary embodiment of FIG. 1 awith the two support bearing halves in a second position; FIG. 2 ashows a second exemplary embodiment of a support bearing with a schematic cross section through a steering housing with two shell-shaped support bearing halves in a first position; FIG. 2 bshows the exemplary embodiment of FIG. 2 awith one of the two support bearing halves in a second position; FIG. 3 ashows a third exemplary embodiment of a support bearing with a schematic cross section through a steering housing with two support bearing halves and curved support surfaces in a first position; FIG. 3 bshows the exemplary embodiment of FIG. 3 awith the two support bearing halves in a second position; FIG. 4 ashows a fourth exemplary embodiment of a support bearing with a schematic cross section through a steering housing with two support bearing halves and straight support surfaces in a first position; FIG. 4 bshows the exemplary embodiment of FIG. 4 awith the two support bearing halves in a second position;The exemplary embodiments of a support bearing illustrated in the figures belong to a rack and pinion steering system, which is not shown in detail in each case and comprises a rotatably mounted steering pinion which engages in a toothed region of a rack via a toothing system. The rack is rotatably guided in a steering housing or steering tube, and FIG. 1 ashows, for example, a schematic cross section through such a steering housing 20 thus with rack 10.The steering housing 20 is tubular, wherein a hollow cylinder is expediently used and the steering housing 20 has an inner surface with a circular cross section. Preferably, the rack 10 is eccentrically arranged within the steering housing 20 and is guided between and thus through at least two support bearing halves 30 and 30', which together form a support bearing. The rack 10 engages with the not-shown steering pinion, which is preferably located above the rack 10. The support bearing preferably supports the rack 10 outside its toothed area.FIG. 1a shows a first exemplary embodiment of a support bearing with two support bearing halves 30, 30' which are designed in the form of shells. Thus, they have a convex outward curvature, with which they each bear against the inner side of the steering housing 20 and thus are supported flat against the latter. The support bearing halves 30, 30' can thus slide on the steering housing 20 and rotate therein.Both support bearing halves 30, 30' each have a concave inner side, within which the toothed rack 10 is guided. In this case, the inwardly curved regions of the support bearing halves 30, 30' which surround the toothed rack 10, merge into straight bearing surfaces 31, 31' on which the toothed rack 10 rests via two bearing points. These support surfaces 31, 31' are preferably at an angle α of <180° to one another, but do not necessarily overlap in this situation.In the opposite region, a respective clamping region 33, 33' is provided, between which a clamping means 40 is introduced, which presses the two support bearing halves 30, 30' apart at this point in a constant manner. The clamping regions 33, 33' can be designed, for example, as depressions or receptacles into which the ends of a compression spring 40 are introduced. By pressing apart the support bearing halves 30, 30' in the upper region, the bearing surfaces 31, 31' are pressed towards one another, as a result of which they press the toothed rack 10 via the bearing points in the direction of the steering pinion, which is not illustrated. In this case, the bearing surfaces 31, 31' exert a compressive force on the rack 10 from both sides, which is converted into a force in the direction of the steering pinion due to the geometries.If wear now takes place on the rack 10 and / or the steering pinion, the support bearing halves 30, 30' can continue to rotate within the steering housing 20 due to their geometry in cooperation with the force of the spring 40 such that the bearing surfaces 31, 31' move towards one another, whereby the bearing points of the rack 10 on the bearing surfaces 31, 31' are displaced further in the direction of the rack 10. As a result, the rack 10 is "raised" and continues to bear under prestress against the steering pinion.The support surfaces 31, 31' can now overlap in the support region, as is shown in FIG. 1b. One support bearing half is then located behind or in front of the other support bearing half in the illustration of FIG. 1b, so that the two support bearing halves 30, 30' can slide along one another. In this case, they can be in contact with one another, or a slight axial gap is provided between the two support bearing halves 30, 30'. In another embodiment, the end regions of the support surfaces 31, 31' are formed comb-like at least in regions, so that these comb regions can engage one another. Here too, the individual teeth of the comb regions are then arranged axially offset with respect to one another.FIG. 2a schematically shows an embodiment of the invention in which only one shell-shaped support bearing half 30' is designed to be movable, while the other support bearing half 30 is fixedly mounted within the steering housing 20. Such an embodiment can also be realized with other forms of support bearing halves, so that it is to be explained with reference to FIGS. 2 aand 2 b merely by way of example for shell-shaped support bearing halves. Furthermore, the embodiments of other figures could also be implemented with a fixed and a movable support bearing half, in particular without the mirror-symmetrical shape of the support bearing halves being changed in this case. For the exemplary embodiment of FIGS. 2 aand 2 b, however, the support bearing halves are not designed mirror-symmetrically.The movable support bearing half 30' has a support surface 31', on which the toothed rack 10 rests. In this case, it can rest laterally on the fixed support bearing half 30, but it does not rest on this support bearing half 30, but instead gives the rack lateral support only. If the support bearing half 30' is pressed away from the fixed support bearing half 30 in the upper region by the clamping means 40, the support bearing half 30' rotates and tilts within the steering housing 20 such that its bearing surface 31' changes position. The geometry of the movable support bearing half 30' is selected such that the contact point of the toothed rack 10 on the contact surface 31' must be displaced in the direction of the steering pinion, not shown again, i.e. in the direction of the longitudinal axis of the steering housing 20. Furthermore, it can be provided that the toothed rack 10 now no longer rests only on the straight bearing surface 31', but also on an adjoining concave region.In the third exemplary embodiment of FIG. 3a, the two support bearing halves 30, 30' are designed to be mirror-symmetrical and substantially hook-shaped along the toothed rack 10. This hook shape includes a bracket 32 and 32' from which support surfaces 31 and 31' project angularly. In this case, the bearing surfaces 31, 31' each project in the direction of the toothed rack 10 from their associated bracket 32, 32', so that the two support bearing halves 30, 30' encompass the toothed rack 10. The two support surfaces 31, 31' together form a support region, within which the toothed rack 10 rests on the two support surfaces 31, 31' and between the two brackets 32, 32'.The support surfaces 31, 31' are, for example, curved, with their concave side directed towards the rack 10 so that the latter rests in the concave inward curvature. The brackets 32, 32' are straight, however, they may be of other suitable shapes.Furthermore, the two support surfaces 31, 31' overlap in a lower overlap region, wherein they are at an angle α of <180° to one another. The rack 10 thus rests in a kind of depression or funnel which is / is formed by the bearing surfaces 31, 31' of the two support bearing halves 30, 30'. Preferably, in the installed position, the contact rod with the toothed rack 10 forms a self-locking angle which prevents the toothed rack 10 from pressing the support bearing halves 30, 30' apart.The overlap can be achieved, for example, by the two support bearing halves 30, 30' being arranged offset relative to one another in the axial direction along the toothed rack 10. This overlap can again be realized by support bearing halves 30, 30' arranged offset axially with respect to one another or comb-like shaped support surfaces 31, 31' which engage in one another.The two support bearing halves 30, 30' are supported in each case via two points on the inner side of the steering housing 20. The first point is formed by the lower end of each bearing surface 31, 31' which rests on the inside of the steering housing 20. The other point is formed by the opposite free end of each bracket 32, 32' which rests at the top against the inside of the steering housing 20. The rack 10 rests on a bearing surface 31, 31' at one point, so that the position of these two bearing points determines the position of the rack 10 within the steering housing 20.A compression spring 40 is tensioned between the two support bearing halves 30, 30', wherein this is preferably effected between the two brackets 32, 32'. For this purpose, tensioning regions 33 and 33' can be formed on the free ends of the brackets 32, 32', between which tensioning regions the spring 40 is tensioned. In the exemplary embodiment of FIG. 3a, such a clamping region 33, 33' is formed, for example, in that the bracket 32, 32' bends away outwards in this region. A spiral spring can be selected as the compression spring 40, for example, but other types of springs such as leaf springs, etc. can also be used.At least one support bearing half is movably mounted within the steering housing 20, wherein both support bearing halves 30, 30' can also be movable, as provided by the exemplary embodiment of FIG. 3a. Both support bearing halves 30, 30' are rotatable or tiltable about an axis which runs parallel to the longitudinal axis of the rack 10 and during this movement slide in opposite rotational directions along the inner side of the steering housing 20.The described geometry and the movability of the two support bearing halves 30, 30' then causes the toothed rack 10 to be pressed upward by the two support surfaces 31, 31' against the not-shown steering pinion, i.e. to bear against the latter under prestress. In the case of a rack 10 arranged eccentrically within the steering housing 20, the latter is thus pressed in the direction of the longitudinal axis of the steering housing 20. The spring 40 thereby presses the clamping regions 33, 33' apart, whereby the contact surfaces 31, 31' move towards each other. As a result, the position of the two bearing surfaces 31, 31' relative to one another changes such that the bearing points of the toothed rack 10 on the bearing surfaces 31, 31' are necessarily displaced in the direction of the steering pinion. This is achieved in that the support surfaces 31, 31' standing at an angle α of <180° to one another exert pressure on the rack 10 from both sides, which is converted into a movement of the rack 10 in the direction of the steering pinion by the inclination of the support surfaces 31, 31'.If wear now takes place on the rack 10 and / or the steering pinion, which requires a displacement of the rack 10 in the direction of the steering pinion, this takes place automatically, since the rack 10 can then be successively raised by the particular geometry of the support bearing halves 30, 30' and the force of the spring 40 to such an extent that it continues to bear against the steering pinion under prestress. This situation is shown in FIG. 3 b, wherein the length of the compression spring 40 has increased visually. As a result, the support bearing halves 30, 30' have rotated within the steering housing 20 in such a way that the bearing surfaces 31, 31' have moved towards one another. As a result, the point of intersection between the bearing surfaces 31, 31' has moved in the direction of the toothed rack 10, so that the latter has been raised or pressed in the direction of the steering pinion. The overlap area between the two support bearing halves 30, 30' has become larger.FIG. 4 ashows a second exemplary embodiment of a support bearing with substantially the same / identically acting components as in the exemplary embodiment of FIGS. 3 aand 3 b. However, in this embodiment the support surfaces 31, 31' are not curved but are formed straight, so that the rack 10 in a support region rests on two straight support surfaces 31, 31', which, however, are preferably also at an angle α of <180° to each other. This design also makes it possible for the bearing points of the toothed rack 10 on the two bearing surfaces 31, 31' to be displaced in the direction of the steering pinion when wear occurs on the toothed rack 10 and or the steering pinion, in order thus to keep the toothed rack 10 bearing against the steering pinion under prestress. Such a second position of the rack 10 is shown in FIG. 4b, wherein the overlap area between the two support bearing halves 30, 30' has also become larger here.List of reference numbers:10 Rack 20 steering housing, steering tube 30, 30' support bearing half, shell 31, 31' support surface 32, 32' bracket 33, 33' clamping region, receptacle 40 clamping means, spring, compression spring α angle

Claims

Rack and pinion steering system for motor vehicles having a rotatably mounted steering pinion which engages via a toothing system in a toothed region of a rack (10) in such a way that a rotation of the steering pinion leads to a displacement of the rack (10) in the direction of its longitudinal axis, wherein the rack (10) is guided in a steering housing (20) in a longitudinally displaceable manner, and is held within the steering housing (20) via at least one support bearing which comprises at least two support bearing halves (30;30'), between which the rack (10) is guided in a movable manner, in that at least one support bearing half (30;30') has a bearing surface (31;31'), on which the rack (10) rests, and in that at least this support bearing half (30;30') is designed in a movable manner within the steering housing (20) and clamping means (40) are provided, which apply a force at least to the movable support bearing half (30;30') in such a way that its bearing surface (31;31') is movable in the direction of the other support bearing half (30;30'), which in this case serves as a counter bearing, whereby the two support bearing halves (30;30') exert a force on the rack (10) at least via the bearing surface (31;31') of the movable support bearing half (30;30') by the interaction of their geometries, characterized in that the clamping means (40) applies a force on the side of the rack (10) opposite the bearing point between the at least one support bearing half (30;30') and the rack (10) at least to the movable support bearing half (30;30'), and in that the two support bearing halves (30; 30') are designed such that they can overlap in the region of the bearing point of the toothed rack (10).Rack and pinion steering system according to Claim 1, characterized in that the at least two support bearing halves (30; 30') each have a bearing surface (31; 31'), which together form a support region and the rack (10) in this support region bears on the two bearing surfaces (31; 31').Rack and pinion steering system according to Claim 2, characterized in that the bearing surfaces (31; 31') in the support region on the side of the rack (10) run at an angle α of <80° with respect to one another.Rack and pinion steering system according to one or more of Claims 1 to 3, characterized in that both support bearing halves (30; 30') are designed to be movable within the steering housing (20).Rack and pinion steering system according to one or more of Claims 1 to 4, characterized in that the two support bearing halves (30; 30') are designed to be mirror-symmetrical with respect to the longitudinal axis of the rack (10).Rack and pinion steering system according to one or more of Claims 1 to 5, characterized in that the clamping means comprise at least one spring (40).Rack and pinion steering system according to Claim 6, characterized in that the spring is a compression spring (40) which is arranged and clamped between the two support bearing halves (30; 30') in such a way that the contact surface (31; 31') of at least the movable support bearing half (30; 30') is pressed in the direction of the other support bearing half (30, 30') by means of its force.Rack and pinion steering system according to one or more of Claims 1 to 7, characterized in that at least one support bearing half (30; 30') which is designed to be movable within the steering housing (20) is of shell-shaped design, the outward curvature of the support bearing half (30; 30') corresponding to the inward curvature of the steering housing (20), as a result of which the at least one support bearing half (30; 30') is supported in a planar manner on the inner side of the steering housing (20), and in that the bearing surface (31; 31') is formed on the inward curvature of this support bearing half (30; 30').Rack and pinion steering system according to one or more of Claims 1 to 7, characterized in that at least one support bearing half (30; 30') which is designed to be movable within the steering housing (20) is of hook-shaped design, wherein it has a bracket (32; 32'), from which a bearing surface (31; 31') projects at an angle in the direction of the rack (10).Rack and pinion steering system according to one or more of Claims 1 to 9, characterized in that at least one support bearing half (30; 30') which is designed to be movable within the steering housing (20) is supported on the inner side of the steering housing (20) via at least two points.Rack and pinion steering system according to Claims 9 and 10, characterized in that at least one support bearing half (30; 30') which is designed to be movable within the steering housing (20) is supported on the inner side of the steering housing (20) at least via its bracket (32; 32') and its bearing surface (31; 31').Rack and pinion steering system according to Claim 9 and one of Claims 10 or 11, characterized in that the compression spring (40) is clamped between the two brackets (32; 32') of the support bearing halves (30; 30').Rack and pinion steering system according to one or more of Claims 1 to 12, characterized in that at least one support bearing half (30; 30') has a clamping region (33; 33') which is designed to support the clamping means (40).Rack and pinion steering system according to one or more of Claims 1 to 13, characterized in that a bearing surface (31; 31') is of concave or straight configuration in cross section.Rack and pinion steering system according to one or more of Claims 2 to 14, characterized in that the bearing surfaces (31; 31') are designed at least in regions in comb-shaped fashion, the comb-shaped regions of the two support bearing halves (30; 30') engaging one another in the support region.Rack and pinion steering system according to one or more of Claims 1 to 15, characterized in that the rack (10) is arranged eccentrically within the steering housing (20).Rack and pinion steering system according to one or more of Claims 1 to 16, characterized in that the geometry of the support bearing halves (30; 30') is designed such that readjustment of the rack (10) is possible only in the direction of the steering pinion.Rack and pinion steering system according to one or more of Claims 1 to 17, characterized in that the inner side of the steering housing (20) and / or the inner side of at least one of the support bearing halves (30; 30') is provided with an elastic material.Rack and pinion steering system according to one or more of Claims 1 to 18, characterized in that at least one of the support bearing halves (30; 30') is produced from an elastic material.

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