steering gear

Abstract

The invention relates to a steering gear (1) for a motor vehicle, comprising a rotationally fixed and linearly displaceable steering spindle (3), which is mounted on a first bearing point (4) and a second bearing point (5) spaced apart in the longitudinal extent of the steering spindle (3), wherein the steering spindle (3) engages with a rotatable gear element such that a rotation of the gear element causes a linear displacement of the steering spindle (3), wherein a first roller (6) is rotatably mounted on the linearly displaceable steering spindle (3), and a second roller (7) opposite the first roller (6) is rotatably mounted on the linearly displaceable steering spindle (3), wherein a first raceway (10) is formed on the steering spindle (3), on which the first roller (6) rolls during operation of the steering gear (1), and / or a second raceway (11) is trained,on which the second roller (7) rolls during operation of the steering gear (1), wherein the first roller (6) and / or the second roller (7) are / is subjected to force in such a way that the first roller (6) and / or the second roller (7) bear / rest against the steering spindle (3) without play during operation of the steering gear (1).

Description

The present invention relates to a steering gear for a motor vehicle comprising a steering spindle which is arranged in a rotationally fixed and linearly displaceable manner and is mounted at a first bearing point and a second bearing point spaced apart in the longitudinal extent of the steering spindle, wherein the steering spindle is in engagement with a rotatable gear element such that a rotation of the gear element causes a linear displacement of the steering spindle.The present invention relates to a steering gear for vehicles, and more particularly to an improved steering gear that makes the transmission of steering forces more efficient and safe. A steering gear is an essential component of the steering system in vehicles. It converts the rotational motion of the steering wheel into a linear motion which then controls the wheels. In the case of steer-by-wire steering, there is no mechanical connection between the steering wheel and the steering gear, since the steering commands are transmitted from the steering wheel to a road-wheel actuator via an electrical signal path. In this case, the steering gear is then driven by a correspondingly controlled electric actuator.In conventional steering gears, the actuation of the steering rod is driven by a gear mechanism, which frequently exerts an additional torque on the spindle. This torque must in turn be supported against the transmission housing, which entails various challenges depending on the design of the steering gear. One such challenge is that the tie rods are usually at an angle to the axis of the steering rod, which can lead to bending of the steering rod, in particular when steering forces and shocks introduced from the roadway become effective.When using such steering gears in steer-by-wire steering systems, there is also a central challenge in ensuring a high force feedback quality for the driver. Traditional systems suffer from significant frictional losses and high steering rod push-through forces caused by the slide bearing or the losses of the transmission used. These factors affect the transmission of important information from the roadway to the driver because they are lost in the friction offset.Conventional plain bearing based sliding bearings tend to produce increased sliding forces due to their inherent friction properties. These forces continue to increase with increasing steering forces, which negatively affects the efficiency and feedback experience.It is therefore the object of the invention to avoid or at least reduce these problems and to provide an improved steering gear for motor vehicles.This object is achieved by a steering gear for a motor vehicle comprising a steering spindle which is arranged in a rotationally fixed and linearly displaceable manner and is mounted at a first bearing point and a second bearing point spaced apart in the longitudinal extent of the steering spindle, wherein the steering spindle is in engagement with a rotatable gear element such that a rotation of the gear element brings about a linear displacement of the steering spindle, wherein a first roller bears in a rotatably mounted manner on the linearly displaceable displaceable steering spindle, and a second roller opposite the first roller bears in a rotatably mounted manner on the linearly displaceable displaceable steering spindle, wherein a first raceway is formed on the steering spindle, on which raceway the first roller rolls during operation of the steering gear and / or a second raceway is formed on the steering spindle, on which raceway the second roller rolls during operation of the steering gear, wherein the first roller and / or the second roller are / is subjected to force in such a way that the first roller and / or the second roller bear / bear on the steering spindle without play during operation of the steering gear.As a result, a purely rolling steering spindle bearing arrangement consisting of at least two rollers mounted in a independently rotatable manner, which rollers cooperatively support the steering spindle with respect to all radially acting forces and against rotation, but which permits axially displaceable freedom with as little friction losses as possible.The two rollers thus make it possible to support the torques introduced by the steering spindle. In addition, the steering gear is play-compensating due to the at least one power-loaded roller, which contributes to a smooth operation of the steering gear, since undesired rattling or rattling noises can be avoided by the prestress.The steering gear according to the invention thus provides a displacement bearing for the steering spindle, which is designed specifically for minimizing the thrust forces. Due to the significant reduction of the frictional forces, the steering gear according to the invention offers an optimized solution which both improves the quality of the force feedback and thus the interaction between the vehicle and the driver and also increases the efficiency of the overall system.It is preferred here that at least two rollers roll on at least three raceway sections extending axially along the steering spindle, wherein one of the rollers consists of a first and second roller half and at least one of the roller halves is arranged displaceably along its axis of rotation and is prestressed by a spring element so as to press against the steering rod.The steering spindle can also be referred to as steering rod in the sense of this application.According to an advantageous embodiment of the invention, it can be provided that the first roller has a first axis of rotation which is oriented perpendicularly to the longitudinal extent of the steering spindle and / or the second roller has a second axis of rotation which is oriented perpendicularly to the longitudinal extent of the steering spindle, which has proven to be particularly favorable with regard to reducing resistance torque to a linear offset of the steering spindle and also with regard to as high a torque support as possible.According to a further preferred development of the invention, it can also be provided that the first roller and / or the second roller) is / are subjected to spring force, in particular in the axial direction. By means of a spring force application, an accurate and cost-effective force application for prestressing a roller relative to the steering spindle can be effected. A spring element as used in connection with this invention is a mechanical component that stores and releases energy in the form of elastic deformation. It is designed to undergo a certain deformation upon application of a force and return to its original shape upon removal of this force. A spring element can be selected from the group of the spiral springs, leaf springs, disk springs, disk springs, torsion springs and / or rubber springs.According to a further preferred development of the invention, it can also be provided that the spring element is configured as a disk spring which is designed as a frustoconical, conical disk spring. Disk springs can be used in connection with this invention individually or in columns consisting of several springs arranged one above the other. The arrangement of the disk springs can be parallel (in the same direction) or serial (in the opposite direction) in order to achieve different spring characteristic curves and load characteristics and to adapt the spring stiffness and the load limits exactly to the specific requirements of the steering gear.The raceways for the rollers formed on the steering spindle preferably have a planar contact surface in the longitudinal extent of the steering spindle. In other words, the raceways have no thread, but may be present in the axially adjacent sections of the steering spindle. Advantageously, at least one of the raceways is formed by a radially inwardly directed material removal from the circular cross-sectional shape of the steering spindle, with the result that a transmission of torques between this raceway and a corresponding roller is made possible.Furthermore, according to a likewise advantageous embodiment of the invention, it can be provided that the second raceway of the steering spindle has a first raceway section which differs from a circular section shape and is directed radially inward, and / or the second raceway of the steering spindle has a second raceway section which differs from a circular section shape and is directed radially inward.The advantageous effect of this embodiment is due to the fact that the second raceway with one or both raceway sections enables torques to be absorbed and transmitted between the corresponding roller or roller half. As a result, torque can be transmitted from the steering spindle to one or more rollers at circumferentially distributed points, which can contribute to making the steering gear more compact on account of a better load distribution.According to a further particularly preferred embodiment of the invention, it can be provided that the first roller is designed as a cylindrical roller. Because the cylindrical roller forms a linear contact with the corresponding raceway of the steering spindle, a torque transmission between the steering spindle and the cylindrical roller is also made possible.In a preferred embodiment of the invention, it can also be provided that a roller can be formed in multiple parts. Preferably, a roller is embodied in two parts, with a first roller half and a second roller half, wherein it is further preferred that both roller halves are guided axially displaceably relative to one another. Furthermore, the invention can also be further developed to the effect that the second roller is formed in two parts, with a first roller half and a second roller half arranged coaxially to the first roller half, wherein the first roller half has a first running surface which during operation of the steering spindle rolls on the second running path of the steering spindle and the second roller half has a second running surface which during operation of the steering spindle rolls on the second running path of the steering spindle.The running surfaces of the roller halves with the steering spindle can be designed either convexly, concavely or conically-corresponding to the respectively associated running path of the steering spindle. It is particularly preferred that, independently of the shape of the raceways and running surfaces, a spherical contact is formed between a running surface and a running surface, so that drilling friction in the rolling contact can be reduced. Thus, for example, the rolling shape radius of a convexly shaped roller half is smaller than the concave shape radius in the corresponding raceway of the steering spindle-and vice versa. Furthermore, it is advantageous that the components rolling with the steering spindle, in particular the rollers and the spindle itself, are hardened at least in the contact regions.Preferably, both roller halves are mounted with respect to one another by a common axis, i.e. are positioned coaxially with respect to one another. The first roller half and the second roller half can preferably be arranged on a common shaft and / or bolt.It is also preferable that the first roller half and the second roller half are rotatable relative to each other. Due to the axial displaceability, the contact points of the roller halves with the steering spindle are generally not static. Since the steering spindle can execute small tilting angles under torque, the contact areas can migrate, for example in the case of a present crowning, which leads to different instantaneous rolling diameters with respect to the roller axis and the two roller halves can then rotate at different angular speeds.In a likewise preferred embodiment variant of the invention, it can also be provided that the first roller half and / or the second roller half are / is spring-loaded by a spring element in the axial direction directed toward the steering spindle. In this way, it can be achieved in particular that the steering spindle is always in contact with the rollers or roller halves at its at least three raceway regions within the scope of the prestressing force and thus represents a smooth, play-free mounting of the steering spindle.It may also be advantageous to further develop the invention to the effect that the first roller half is rotatably mounted on a first angular contact ball bearing and / or the second roller half is rotatably mounted via a second angular contact ball bearing.A angular contact ball bearing is a rolling bearing specifically designed to accommodate both radial and axial loads. It is characterized by the oblique arrangement of the balls with respect to the raceways of the rolling bearing, which enables the angular ball bearing to absorb loads which occur at an angle to the bearing axis.An outer ring of a angular ball bearing is preferably provided by a rolling thrust washer of the steering gear. The outer ring or the rolling thrust disc is arranged here on the side of the angular ball bearing facing away from the steering spindle.The inner ring of a tapered ball bearing is preferably formed by a roller half. The inner ring or the roller half is arranged here on the side of the angular ball bearing directed toward the steering spindle.Rolling rolling rolling bodies are arranged between an inner ring and an outer ring of the angular ball bearing. Between these three main components inner ring, outer ring and the rolling elements, rolling friction generally occurs mainly within the angular contact ball bearing. Since the rolling bodies in the inner and outer rings can preferably roll on hardened steel surfaces with optimized lubrication, the rolling friction is low.The term angular contact ball bearing as used in this application does not exclude the possibility that roller-shaped rolling bodies can also be used in an angular contact ball bearing instead of bearing balls. The rolling elements can thus have the shape of a ball or a roller depending on the type of rolling bearing. They roll on the raceways of the angular contact ball bearing and have the task of transmitting a force acting on the angular contact ball bearing from the outer ring to the inner ring and vice versa. Roller-shaped rolling elements are also referred to as roller rolling elements and spherical rolling elements as bearing balls.Roller-shaped rolling bodies can be selected, for example, from the group of symmetrical pendulum rollers, asymmetrical pendulum rollers, cylindrical rollers, needle rollers and / or conical rollers.Rolling elements can be guided in a cage or by rolling element spacers and be spaced apart from one another. It is also conceivable in principle to form a cageless angular contact ball bearing, which is also referred to as a full-roller angular contact ball bearing. In the case of full-rolling angular ball bearings, adjacent rolling bodies can contact one another.The rolling bodies can roll within the angular ball bearing, in particular on the inner ring raceway of the inner ring. For this purpose, the surface of the inner ring raceway can advantageously be designed to be correspondingly abrasion-resistant, for example also by a corresponding surface treatment method and / or by applying a corresponding additional material layer. The inner ring raceway can be planar or profiled. A profiled configuration of the inner ring raceway can serve, for example, for guiding the rolling bodies on the inner ring raceway. A planar formation of the inner ring raceway, on the other hand, can allow for a certain axial displaceability of the rolling bodies on the inner ring raceway, for example.The rolling bodies can roll within the angular ball bearing, in particular on the outer ring raceway of the outer ring. For this purpose, the surface of the outer ring raceway can advantageously be designed to be correspondingly abrasion-resistant, for example also by a corresponding surface treatment method and / or by applying a corresponding additional material layer.The outer ring raceway can be planar or profiled. A profiled configuration of the outer ring raceway can serve, for example, for guiding the rolling bodies on the outer ring raceway. A planar formation of the outer ring raceway, on the other hand, can allow for a certain axial displaceability of the rolling bodies on the outer ring raceway, for example.A spherical bearing can have a cage, wherein the cage guides the rolling bodies. The cage is designed such that the rolling body balls and / or the rolling body rollers are spaced apart from one another, so that, for example, the friction and heat generation of the rolling bodies is kept as low as possible. Furthermore, the cage holds the rolling element balls and / or rolling element rollers at a fixed distance from one another during rolling, as a result of which a uniform load distribution can be achieved. The cage can be embodied in one piece or in multiple pieces.The first angular contact ball bearing and the second angular contact ball bearing may be arranged in an X or O configuration.According to a further preferred embodiment of the subject matter of the invention, it can be provided that the pressure lines of the rolling contacts of the first roller intersect with the first raceway of the steering spindle with the pressure cone of the first angular contact ball bearing and of the second angular contact ball bearing. This minimizes the resulting tilting moment acting on a roller half. Since the two roller halves are displaceable relative to one another on a common shaft, these reduced tilting torques counteract possible increases in friction (for example due to tilting effects) and ensure ready movement of the axial displacement of the steering spindle even under load.Finally, the invention can also be advantageously embodied to the effect that the spring element is designed as a compression spring which is supported on the one hand on an axially displaceable first rolling thrust washer of the first angular ball bearing and on the other hand on an axially displaceable adjusting screw, so that the spring prestress of the spring element exerted on the first roller half can be adjusted via the adjusting screw. The spring element acting axially on a roller half, for example a disk spring, can thus make it possible, together with the pressure angle mentioned, to effectively compensate for any play in the bearing point between the steering spindle and the rollers.The adjusting screw can also provide an end stop in the case of high lateral spindle forces or moments, in which the prestressing force of the spring element is exceeded and the corresponding roller half together with the bearing with the rolling pressure disk escapes axially and compresses the spring element. The end stop can be effected either between the adjusting screw and the rolling pressure disc or between the adjusting screw and the plane-pressed disk spring, which then again bears like a disc against the rolling pressure disc.The invention will be explained in more detail below with reference to figures without limiting the general concept of the invention.It shows: FIG. 1 shows a steering gear in a longitudinal sectional view, FIG. 2 shows a first embodiment of a steering gear in a cross-sectional illustration, FIG. 3 shows a second embodiment of a steering gear in a cross-sectional illustration, FIG. 4 shows a third embodiment of a steering gear in a cross-sectional illustration, FIG. 5 shows a fourth embodiment of a steering gear in a cross-sectional illustration, FIG. 6 shows a fifth embodiment of a steering gear in a cross-sectional illustration.FIG. 1 shows a steering gear 1 for a motor vehicle comprising a steering spindle 3 which is arranged in a rotationally fixed and linearly displaceable manner and is mounted at a first bearing point 4 and a second bearing point 5 spaced apart in the longitudinal extent of the steering spindle 3, wherein the steering spindle 3 is in engagement with a rotatable gear element such that a rotation of the gear element causes a linear offset of the steering spindle 3. In this case, a first roller 6 is rotatably mounted on the linearly displaceable steering spindle 3 and a second roller 7 opposite the first roller 6 is rotatably mounted on the linearly displaceable steering spindle 3.A first track 10 is formed on the steering spindle 3, on which the first roller 6 rolls during operation of the steering gear 1. Furthermore, a second raceway 11 is formed on the steering spindle 3, on which the second roller 7 rolls during operation of the steering gear 1. The second roller 7 is acted upon by force in such a way that the first roller 6 and the second roller 7 bear on the steering spindle 3 without play during operation of the steering gear 1.This will now be explained in more detail below with reference to the cross-sectional representations of various embodiments of the steering gear 1 in FIGS. 2-5.FIG. 2 shows a first embodiment of a steering gear 1, in which the first roller 6 has a first axis of rotation 8, which is oriented perpendicularly to the longitudinal extent of the steering spindle 3, and the second roller 7 has a second axis of rotation 9, which is oriented perpendicularly to the longitudinal extent of the steering spindle 3. The two axes of rotation 8, 9 thus run axis-parallel.In the embodiment shown, the first roller 6 is designed as a cylindrical roller and rolls on the first raceway 10 of the steering spindle 3, which has a straight, linear contour in cross section, which is oriented parallel to the first axis of rotation 8. This results in a linear rolling contact of the first roller 6 with the steering spindle 3, which in particular also enables a transmission of torques between the steering spindle 3 and the first roller 6.This embodiment of the first raceway 10 is also referred to as spindle flattening.The first roller 6 is preferably provided in one piece with two axially outwardly extending bolt-like bearing sections, which define a shaft 33 of the first roller 6 and via which the first roller 6 is linked to the needle bearings 31, 32 and is mounted rotatably with respect to the transmission housing 26. For the assembly and / or maintenance of the steering gear 1, a housing cover 34 is provided in the region of the first roller 6 in the gear housing 26.The second raceway 11 of the steering spindle 3 has a first raceway section 16 which differs from a circular section shape and is directed radially inward, and a second raceway section 17 which differs from a circular section shape and is directed radially inward.FIG. 2 also shows that the second roller 7 is formed in two parts, with a first roller half 12 and a second roller half 13 which is arranged coaxially with the first roller half 12 and is designed to be axially displaceable. The first roller half 12 has a first running surface 14 which during operation of the steering spindle 3 rolls on the second running surface 11 of the steering spindle 3, and the second roller half 13 has a second running surface 15 which during operation of the steering spindle 3 rolls on the second running surface 11 of the steering spindle 3. In this case, the first roller half 12 and the second roller half 13 are arranged on a common shaft 25, wherein the second roller half 13 is guided on the shaft 25 so as to be displaceable and preferably also rotatable relative to the shaft 25.The second roller half 13 is spring-loaded and thus prestressed in the axial direction directed toward the steering spindle 3 by a spring element 18. The spring element 18 is designed as a disk spring. The spring element 18 is supported on the one hand on an axially displaceable first rolling thrust washer 23 of the first angular ball bearing 19 and on the other hand on an axially displaceable adjusting screw 24, so that the spring prestress of the spring element 18 exerted on the first roller half 12 can be adjusted by means of the adjusting screw 24. A small air gap between the adjusting screw 24 and the roller thrust washer 23 can be adjusted by means of the adjusting screw 24, so that the second roller half 13 can "breathe" axially over the tolerance fluctuations associated with the travel path. Larger steering spindle forces acting laterally to the right can exceed the prestressing force of the spring element 18 during operation of the steering gear 1, and therefore the adjusting screw 24 can also serve as an axial travel limiter. The adjusting screw 24 is sealed off from the transmission housing 26 via the seal 27.The first roller half 12 is rotatably mounted via a first angular ball bearing 19 and the second roller half 13 is rotatably mounted via a second angular ball bearing 20. Here, the roller halves 12, 13 each form an inner ring of the respective angular contact ball bearing 19, 20 and the rolling thrust washers 23, 30 each form an outer ring. The inner rings each have an inner ring raceway for the rolling bodies 28, 29 and the outer rings each have an outer ring raceway for the rolling bodies 28, 29.The rolling thrust washer 30 is securely embedded in the transmission housing 26, while the rolling thrust washer 23 is guided in the transmission housing 26 so as to be axially displaceable relative to the latter. In the embodiment of FIG. 2, the first angular contact ball bearing 19 and the second angular contact ball bearing are formed in an O-configuration.The roller halves 12, 13 of the first roller 7 are designed in the widest sense to be disk-shaped in their contact rolling region with the steering spindle 3, the rolling region of which is in spherical contact with the corresponding raceway sections 16, 17 of the steering spindle 3. In this case, the raceway sections 16, 17 can be basically concave (as shown), convex or conical. The contact area of the roller halves 12, 13 of the second roller 7 with the steering spindle 3 can thus take place at a defined pressure angle, similar to a spherical bearing. Thus, the second roller 7 is also able to absorb lateral forces of the steering spindle 3.The spherical contact paths between the path sections 16, 17 and the roller halves 12, 13 lead here, in combination with the outer contact region of the first roller 6, which is designed as a cylinder, to a more favorable increase in the lever arm during the torque support because of the contact angle. As a result, pressures on the first roller or the first raceway 10 can be reduced when the torque is applied, which can contribute to making the diameter of the first roller 6, which is designed as a cylinder, as small as possible. Alternatively, the extent of spindle flattening can also be reduced, which leads to more spindle cross section.FIG. 3 shows an embodiment of a steering gear 1, which corresponds substantially to the structure of the steering gear 1 already known from FIG. 2, in which, however, the angular ball bearings 19, 20 are arranged in an X configuration, which can be advantageous on account of the ball contact pressures occurring in the angular ball bearings 19, 20. It can be seen clearly that the pressure lines 21 of the rolling contacts of the first roller 6 intersect with the first raceway 10 of the steering spindle 3 with the pressure cone 22 of the first angular contact ball bearing 19 and of the second angular contact ball bearing 20. The perpendicular to the rolling contact of each roller half 12, 13 thus describes a pressure line 21, similar to a spherical bearing. This minimizes the tilting moment resulting on the roller halves 12, 13. Since the two roller halves 12, 13 are displaceable relative to one another on the common shaft 25 and are rotatable relative to one another, reduced tilting torques counteract possible increases in friction (tilting effects) and ensure ready rotation of the axial displacement and of the relative rotation even under load.In the embodiments of FIGS. 4-5, the region of the second raceway 11 with its two raceway sections 16 has been retained as a cylindrical-section-shaped region of the steering spindle 3 without a thread, which facilitates particularly cost-effective production of the steering gear 1.In these embodiments, the roller halves 12, 13 have a concave crowning so that a good osculation is achieved with the cylindrical raceway sections 16, 17 of the steering spindle 3. Of course, the roller halves 12, 13 can also be designed conically, be particularly simple in construction, but lead to somewhat higher contact pressures. In this design, the X-arrangement of the angular contact ball bearings 19, 20 is particularly advantageous, since a compact design is made possible as a result. Analogously to the spindle flattening in the case of the first roller 6, spindle flattenings can likewise be carried out in the contact regions with the two roller halves 12, 13 in the case of conical roller halves 12, 13. Here too, a slight crowning will then preferably be taken into account either on the steering spindle 3 and / or on the conical roller halves 12, 13.It is understood that in these embodiments of FIGS. 4-5, the moment support is realized solely by the upper cylindrical first roller 6. Since edge carriers in the contact region of the spindle edges (transition from flattening to the lateral surface) with the first roller 6 are to be avoided, either the first roller 6 or the first raceway 10 is designed in a spherical manner in these regions.As in the embodiments already known from FIGS. 2-3, the first and the second roller half 12, 13 of the first roller 7 are guided on a common shaft 25, wherein at least one of the roller halves 12, 13 (here the second roller half 13) is mounted so as to be axially displaceable and rotatable relative to the first roller half 12. Alternatively, two identical roller halves 12, 13 are also conceivable, which are guided as a common axis on a common shaft 25 supported in a floating manner. Of course, an additional sliding bearing sleeve can be provided between the shaft 25 and a roller half 12, 13, which is not shown in the figures, however.FIG. 5 shows a further development of the variant of a steering gear 1 already known from FIG. 4 Here, too, the rolling thrust washer 23 is mounted in the gear housing 26 in an axially displaceable manner via the adjusting screw 24. The outer circumferential surface of the rolling pressure disc 23 can, as is also provided in the embodiments of FIGS. 2-4, be slightly crowned (convex) in order to avoid tilting of the rolling pressure disc 23 with the transmission housing 26. The same applies analogously to the rolling thrust washer 30. the rolling thrust washers 23, 30 are preferably embodied in identical parts. Alternatively, as is now shown in FIG. 5, the rolling thrust washer 23 can be designed with a somewhat greater radial clearance and can thereby be guided with clearance in the transmission housing 26. In the region of the axial offset of the rolling thrust washer 23, a seal 35 designed as an O-ring is embedded in the transmission housing 26, which seal generates a centering action with respect to the rolling thrust washer 23 with the transmission housing 26.It is understood that all components of the steering gear 1 can be arranged in the gear housing 26 and the steering spindle 3 extends in its longitudinal extension on both sides out of the gear housing 26. As a result, the components arranged within the transmission housing 26 can be well protected from external mechanical and / or chemical influences.Due to their axial displaceability, the contact points of the roller halves 12, 13 with the steering spindle 3 are generally not static. Since the steering spindle 3 can make small angles of inclination under torque, the contact areas can migrate in the case of a present crowning, which leads to different instantaneous rolling diameters with respect to the roller axis and the two roller halves 12, 13 can then rotate at different angular speeds. This is shown in FIG. 6 and is explained in more detail below.FIG. 6 illustrates different rolling radii (contact point with respect to the axis of rotation) on the basis of conical roller halves 12, 13. This is caused by an increased supporting torque on the steering spindle 3, as a result of which the second roller half 13 is pressed to the right against the end stop of the adjusting screw 24. The rolling pressure disc 23 is therefore shown in the blocked or end stop state with the disc spring (spring element 18) pressed flat. It can be seen easily that in such an operating state the rolling radius R of the first roller half 12 is greater than the rolling radius r of the second roller half 13 with the spindle 3, which leads to different rotational speeds of the roller halves 12, 13. Because the second roller half 13 is also rotatably mounted on the shaft 25, the first and the second roller half 12, 13 can consequently be rotated relative to one another.FIG. 6 also shows a further development of the adjusting screw 24 which has a central through bore. The set axial travel on the right-hand roller thrust washer 23 can be measured and set through this bore by simultaneously applying a torque (or radial force directed downward in the direction of the roller halves 12, 13) to the steering spindle 3. Subsequently, the through hole is watertightly closed by inserting a rubber plug.The invention is not limited to the embodiments shown in the figures. The foregoing description is, therefore, not to be considered as limiting, but illustrative. The following claims should be understood to mean that a said feature is present in at least one embodiment of the invention. This does not exclude the presence of further features. If the patent claims and the above description define "first" and "second" features, this designation serves to distinguish two features of the same type without specifying a ranking.List of reference characters1 Steering gear 3 Steering spindle 4 Bearing point 5 Bearing point 6 Roller 7 Roller 8 Axis of rotation 9 Axis of rotation 10 Raceway 11 Raceway 12 Roller half 13 Roller half 14 Raceway 15 Raceway 16 Raceway section 17 Raceway section 18 Spring element 19 Angular ball bearing 20 Angular ball bearing 21 Pressure lines 22 Pressure cone 23 Rolling pressure disk 24 Adjusting screw 25 Shaft 26 Transmission housing 27 Seal 28 Rolling elements 29 Rolling elements 30 Rolling pressure disk 31 Needle bearing 32 Needle bearing 33 Shaft 34 Housing cover 35 Seal

Claims

Steering gear (1) for a motor vehicle comprising a steering spindle (3) which is arranged in a rotationally fixed and linearly displaceable manner and is mounted at a first bearing point (4) and a second bearing point (5) spaced apart in the longitudinal extent of the steering spindle (3), wherein the steering spindle (3) is in engagement with a rotatable gear element in such a way that a rotation of the gear element brings about a linear displacement of the steering spindle (3), characterized in that a first roller (6) bears, rotatably mounted, against the steering spindle (3) which can be displaced linearly displaceably, and a second roller (7) which is opposite the first roller (6) bears, rotatably mounted, against the steering spindle (3) which can be displaced linearly, wherein a first raceway (10) is formed on the steering spindle (3), on which the first roller (6) rolls during operation of the steering gear (1) and / or on which a second raceway (11) is formed on which the second roller (7) rolls during operation of the steering gear (1), wherein the first roller (6) and / or the second roller (7) are / are subjected to force in such a way that the first roller (6) and / or the second roller (7) bear / bear on the steering shaft (3) without play during operation of the steering gear (1).Steering gear (1) according to Claim 1, characterized in that the first roller (6) has a first axis of rotation (8) which is oriented perpendicularly to the longitudinal extent of the steering spindle (3) and / or the second roller (7) has a second axis of rotation (9) which is oriented perpendicularly to the longitudinal extent of the steering spindle (3).Steering gear (1) according to Claim 1 or 2, characterized in that the first roller (6) and / or the second roller (7) are / is subjected to spring force, in particular in the axial direction.Steering gear (1) according to one of the preceding claims, characterized in that the second raceway (11) of the steering spindle (3) has a first raceway section (16) which differs from a circular section shape and is directed radially inwards, and / or the second raceway (11) of the steering spindle (3) has a second raceway section (17) which differs from a circular section shape and is directed radially inwards.Steering gear (1) according to one of the preceding claims, characterized in that the first roller (6) is designed as a cylindrical roller.Steering gear (1) according to one of the preceding claims, characterized in that the second roller (7) is formed in two parts, having a first roller half (12) and a second roller half (13) arranged coaxially with the first roller half (12), wherein the first roller half (12) has a first running surface (14) which during operation of the steering spindle (3) rolls on the second running surface (11) of the steering spindle (3) and the second roller half (13) has a second running surface (15) which during operation of the steering spindle (3) rolls on the second running surface (11) of the steering spindle (3).Steering gear (1) according to Claim 6, characterized in that the first roller half (12) and the second roller half (13) can be rotated relative to one another.Steering gear (1) according to one of the preceding claims 6 - 7, characterized in that the first roller half (12) is / are rotatably mounted by a first angular ball bearing (19) and / or the second roller half (13) is rotatably mounted by a second angular ball bearing (20).Steering gear (1) according to Claim 8, characterized in that the pressure lines (21) of the rolling contacts of the first roller (6) with the first raceway (10) of the steering spindle (3) intersect with the pressure cone (22) of the first angular ball bearing (19) and of the second angular ball bearing (20).Steering gear (1) according to one of the preceding claims 6 - 9, characterized in that the spring element (18) is designed as a compression spring which is supported on the one hand on an axially displaceable first rolling pressure disc (23) of the first angular ball bearing (19) and on the other hand on an axially displaceable adjusting screw (24), so that the spring prestress of the spring element (18) exerted on the first roller half (12) can be adjusted via the adjusting screw (24).

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