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 rotation of the gear element causes a linear displacement of the steering spindle (3), wherein a bearing block (7) is fixed to the steering spindle (3) between the first bearing point (4) and the second bearing point (5), which extends radially outwards from the lateral surface of the steering spindle (3) and engages in a guide element (8) stationary relative to the steering spindle (3),wherein between the bearing block (7) and the guide element (8) a first sliding element (9) rests on a first sliding surface (10) of the guide element (8) and a second sliding element (11) rests on a second sliding surface (12) of the guide element (8) opposite the first sliding surface (10).

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.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 offset of the steering spindle, wherein a bearing block is fixed on the steering spindle between the first bearing point and the second bearing point, which bearing block extends radially outwards from the lateral surface of the steering spindle and engages in a guide element which is fixed in relation to the steering spindle, wherein a first sliding element bears on a first sliding surface of the guide element between the bearing block and the guide element and a second sliding element bears on a second sliding surface of the guide element which is opposite the first sliding surface.The steering gear according to the invention achieves an optimized torque support which is provided between the two main bearing points of the spindle or steering rod. This construction provides improved transmission and distribution of forces within the steering gear, thereby enhancing the safety and efficiency of the steering operation in vehicles.The steering gear does not obstruct the steering spindle in its deflection and can be adapted with respect to the deflection deflections and angles, so that the steering gear is not, for example, overdetermined with respect to its mounting.In its simplest form, the torque-supporting point of the steering gear can have a sliding guide which consists of the bearing block serving as a slide and the guide element having a groove, in which the bearing block engages. The two sliding elements lying opposite one another also permit in particular a uniform torque support in both linear offset directions of the steering spindle.The bearing block can be fastened to the steering spindle, for example, by means of a screw connection. In principle, other types of fastening are also conceivable, such as, for example, materially bonded connections, such as, in particular, welding or adhesive bonding.A sliding element can be formed, for example, from a material from the group of metals, polymer composite materials, fluoropolymers, in particular PTFE, ceramics and / or elastomers. Especially preferred here are self-lubricating metals or plastics which are impregnated with solid lubricants such as graphite or molybdenum disulfide in order to ensure continuous lubrication.According to an advantageous embodiment of the invention, it can be provided that the first sliding element is spring-loaded with a first spring element in the direction of the first sliding surface and / or the second sliding element is spring-loaded with a second spring element in the direction of the second sliding surface.An additional spring element, which presses one of the sliding elements with prestress against the sliding surface of the guide element, contributes to configuring the torque support as free of play and preferably prestressed resiliently as possible with respect to the guide element, which leads to a reliable avoidance of rattling and rattling noises which otherwise occur at this point during steering operation. The prestress is advantageously selected such that it is greater than the moment-induced supporting forces which occur from the roadway during "normal" travel. By "normal" is meant here, for example, travel over conventional unevenness of the road, ballast road or head stone compactors-not increased supporting torques, such as occur, for example, in the case of striking holes, parking in a stationary position, etc. The accompanying sliding friction due to the spring prestress additionally has a damping effect with respect to undesired chassis resonances such as, for example, so-called wheel flutter. Thus, the necessary magnitude of the spring biasing force can also be selected with respect to this requirement.In this case, it is advantageous if the first spring element is supported on the one hand on the bearing block and on the other hand on the first sliding element.It can also be advantageous for the first spring element and the second spring element to be formed integrally, in particular monolithically. In other words, the sliding elements are then subjected to spring force by a common spring element, for example by a helical spring. The spring element then bears, on the one hand, against the first sliding element and, on the other hand, against the second sliding element in a prestressed manner.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, torsion springs and / or rubber springs.According to a further preferred development of the invention, it can also be provided that the first spring element and / or the second spring element is formed as a helical spring. A helical spring is usually made of an elastic material, preferably metal, wound into a helical or helical shape. A helical spring can be selected from the group of tension springs, compression springs, torsion springs, conical and non-cylindrical springs.Furthermore, according to a likewise advantageous embodiment of the invention, it can be provided that the first sliding element has a coupling section, against which the first spring element bears. This coupling section can be designed such that it absorbs the forces transmitted by the spring element to the sliding element and introduces and distributes them into the sliding element without this leading to mechanical damage to the sliding element. In this case, the spring element can bear directly against the coupling section of the sliding element. It would also be conceivable to arrange a washer between the coupling section and the spring element, which washer can provide an improved pressure distribution in the sliding element, and can offer a more abrasion-resistant contact surface, which can contribute to increased operating reliability and lower susceptibility to wear of the steering gear.In this context, it may also be preferred that the coupling section has a cylinder-like receptacle, in which the first spring element, which is formed as a helical spring, engages. This can bring about an improved guidance of the spring element relative to the spiral spring, which contributes to preventing unintentional detachment or slipping of the spiral spring relative to the sliding element.According to a further particularly preferred embodiment of the invention, it can be provided that the bearing block has a first receiving region for the first sliding element, wherein the first receiving region has a spherical or cylindrical contact portion, against which a corresponding contact portion of the first sliding element bears in such a way that the first sliding element is pivotable by an angle with respect to the first receiving region. As a result, the sliding guide of the bearing block can be designed such that it is capable of compensating for the deflections and angular errors occurring during operation of the steering spindle and thus ensuring a constant quality of the sliding contact.In this case, it is particularly preferred that an abutment portion of the bearing block is concave and an abutment portion of a sliding element is convex, which leads to particularly favourable force introductions during the axial displacement of the bearing block, since in this case a sliding element edge can bear against the bearing block for support. In principle, however, it would also be conceivable to interchange the convex / concave arrangement.Furthermore, it is advantageous if the spherically designed contact section is adjoined by a cylinder section which extends into the interior of the bearing block and in which a corresponding contact section of the first sliding element engages, which can contribute to an improved mounting of the sliding element on the bearing block.In one possible embodiment, it can be provided that the first sliding element and / or the second sliding element are / is substantially cylindrical. In this case, the contact surface has a substantially round, preferably circular, surface shape. The cylindrical sliding element can have different cylindrical sections with different diameters along its longitudinal extension.In principle, it would also be conceivable for the first sliding element and / or the second sliding element to be / are substantially cuboidal in design. In this case, the contact surface then has a substantially rectangular surface shape.In order in particular also to enable a good connection of a spring element, the first sliding element and the second sliding element can have a spatial shape that differs from one another. In principle, it would also be conceivable, for example in order to increase the degree of equality in the steering gear, to design the sliding elements identically.According to a preferred embodiment, the bearing block can be produced from a metallic material by means of machining production methods or by means of metal casting. In principle, it is also conceivable to mold the bearing block from a plastic, for example by means of injection molding.Furthermore, the invention can also be further developed to the effect that the bearing block is formed from a metal sheet and the bearing block formed from a metal sheet has a first metal sheet section and a second metal sheet section running substantially parallel to the first metal sheet section, wherein the first metal sheet section carries the first sliding element and the second metal sheet section carries the second sliding element. A bearing block produced from sheet metal by means of forming methods can offer cost advantages in particular in the production of the steering gear. It is also possible to realize weight advantages within the steering gear by means of a bearing block formed from sheet metal.In a likewise preferred embodiment variant of the invention, it can also be provided that the first sheet metal section and the second sheet metal section are designed such that they exert a spring force acting in the direction of the first sliding surface and / or in the direction of the second sliding surface on the first sliding element and / or on the second sliding element. By integrating a spring element into the construction of the bearing block, it is possible to dispense with an additional spring element in the steering gear, which can entail corresponding weight and cost advantages. In principle, it is of course also conceivable that, in addition to the spring action of the bearing block made of sheet metal, a separate spring element is also used, which can then, however, possibly be dimensioned smaller.It can also be advantageous to further develop the invention to the effect that a first spring cap is arranged between the first sliding element and the first spring element, which spring cap transmits the spring force of the first spring element to the first sliding element. This offers the advantage that the introduction of force by the spring element does not take place directly on the sliding element, which can contribute to a more uniform pressure distribution. Furthermore, the spring cap can also offer improved guidance of the spring element, in particular of a spiral spring, in that a cup-shaped projection extends into the spiral spring. The spring cap is preferably manufactured from a metallic material, most preferably from a metal sheet.According to a further preferred embodiment of the subject matter of the invention, it can be provided that the first sliding surface is shaped such that it exerts a spring force in the direction of the first sliding element. It would also be conceivable in principle for the second sliding surface to be shaped such that it exerts a spring force in the direction of the second sliding element. Thus, one or both sliding surfaces can exert a spring force on the respective sliding element. As a result, it is then possible, for example, to dispense with a spring element within the movable bearing block and to shift the spring effect to a static region of the steering gear.For applying the spring force, a spring element can be coupled to a sliding surface, wherein the sliding surface itself then does not need to have any spring elasticity.However, it is preferred that a metal sheet for improved friction behavior is inserted between the guide element and a sliding element. This is advantageous in particular when the guide element is formed from an aluminum material and has correspondingly high coefficients of friction. Since a sliding element is then in sliding contact with the sheet metal as a sliding surface, correspondingly lower friction values can be realized between the sliding partners.In this context, it is furthermore advantageous if at least one of the intermediate plates serving as the sliding surface is designed to be resilient. For this purpose, the sheet metal can be curved, arched or angled, for example, in order to thus represent a resilient element.According to one embodiment, the first sliding surface can be formed by a first metal sheet and / or the second sliding surface can be formed as a second metal sheet. It is then preferred here that at least one of the metal sheets has a spring effect.However, it would also be possible for the first sheet and the second sheet to be configured in one piece, in particular monolithically.Finally, the invention can also be advantageously embodied to the effect that a first stop element is arranged on the bearing block, which first stop element abuts against a second stop element that is stationary with respect to the steering spindle when a predefined offset position is reached in a first offset direction of the bearing block. As a result, a mechanical end stop integrated in the steering gear can be formed for the steering movement.In this context, it is furthermore preferred if a third stop element is arranged on the bearing block, which, when a predefined offset position is reached in a second offset direction of the bearing block, abuts against a fourth stop element which is stationary with respect to the steering spindle.In order to reduce the manufacturing and assembly costs, it may furthermore be preferred that the first stop element and the second stop element are embodied in one piece, in particular also monolithically.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 first embodiment of a steering gear in a perspective view, FIG. 2 shows a first embodiment of a steering gear in a cross-sectional illustration, FIG. 3 shows a bearing block and two sliding elements of the first embodiment of the steering gear in an exploded illustration, FIG. 4 shows a cuboid embodiment of a sliding element in two perspective views, FIG. 5 shows a second embodiment of a steering gear in a guide element in a perspective illustration, FIG. 6 shows a second embodiment of a steering gear in a guide element in a perspective illustration, FIG. 7 shows a second embodiment of a steering gear in a guide element in a cross-sectional illustration, FIG. 8 shows a cross-sectional illustration of a third embodiment of a steering gear in a guide element, FIG. 9 shows a fourth embodiment of a steering gear in a guide element in a cross-sectional illustration.FIG. 1 shows a first embodiment of 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. The steering spindle 3 is in engagement with a rotatable gear element such that rotation of the gear element causes linear displacement of the steering spindle 3.The gear element can be, for example, a worm gear or a spindle nut.A bearing block 7 is fastened to the steering spindle 3 between the first bearing point 4 and the second bearing point 5 by means of a screw connection 25, which extends radially outwards from the lateral surface of the steering spindle 3 and engages in a guide element 8 which is stationary with respect to the steering spindle 3, which can be seen easily with reference to FIG. 2.Between the bearing block 7 and the guide element 8, a first sliding element 9 abuts a first sliding surface 10 of the guide element 8 and a second sliding element 11 abuts a second sliding surface 12 of the guide element 8 opposite the first sliding surface 10.It can also be seen from FIG. 2 that the first sliding element 9 is spring-loaded in the direction of the first sliding surface 10 by a first spring element 13 designed as a helical spring. The first spring element 13 is supported in a prestressed manner on the bearing block 7 on the one hand and on the first sliding element 9 on the other hand. The second sliding element 11, on the other hand, is mounted on a protruding dome 29 of the bearing block 7 without direct action of spring force, in that the dome 29 engages in a corresponding depression of the second sliding element 11. The second sliding element 11 is however indirectly prestressed in that the spring element 13 is supported on the bearing block 7, which in turn then presses against the second sliding element 11.The first sliding element 9 has a coupling section 15 against which the first spring element 13 bears. As can also be seen well from FIG. 3, the coupling section 15 has a cylinder-like receptacle 16, in which the first spring element 13, which is formed as a helical spring, engages.The bearing block 7 also has a first receiving region 17 for the first sliding element 9, wherein the first receiving region 17 has a spherical bearing portion 18, against which a corresponding bearing portion 19 of the first sliding element 9 bears in such a way that the first sliding element 9 can be pivoted by an angle with respect to the first receiving region 17. The second sliding element 11 also has a corresponding second receiving region 28 for the second sliding element 11. This second receiving region 28 likewise has a spherically designed contact section 26, against which the correspondingly shaped contact section 27 of the second sliding element 11 bears in such a way that the second sliding element 11 can also compensate angular misalignment.Adjoining the spherically designed contact section 18 is a cylinder section 30 which extends into the interior of the bearing block 7 and in which a corresponding contact section 20 of the first sliding element 9 engages.In the embodiment shown in FIGS. 1-3, the first sliding element 9 and the second sliding element 11 are substantially cylindrical, wherein the first sliding element 9 and the second sliding element 11 have a different spatial shape from one another.As shown in FIG. 4, however, it is also conceivable in principle to design a sliding element 9, 11 to be substantially cuboidal and substantially identical. A sliding element 9, 11 shaped in this way then also does not have a spherical but a cylindrical contact section 19, which is accommodated in a corresponding, cylindrical contact section 18 of the accommodation region 17 of the bearing block 7. Whereas spherical contact sections 18, 19 permit an angle compensation in practically all spatial directions, in the case of a cylindrical contact section 18, 19 the angle compensation is possible only about a pivot axis.FIGS. 5-9 show further embodiments of the steering gear 1 in which the bearing block 7 is formed from a metal sheet 22. The bearing block 7 formed from a metal sheet 22 has a first metal sheet section 23 and a second metal sheet section 24 running substantially parallel to the first metal sheet section 23, wherein the first metal sheet section 23 carries the first sliding element 9 and the second metal sheet section 24 carries the second sliding element 11, which can be seen clearly from FIG. 6.In this case, the first sheet metal section 23 and the second sheet metal section 24 can be designed such that they exert a spring force acting in the direction of the first sliding surface 10 and / or in the direction of the second sliding surface 12 on the first sliding element 9 and / or on the second sliding element 11.FIG. 5 shows the guide element 8 that, in the exemplary embodiment shown, is formed as a housing component of the steering gear 1. The steering spindle 3 extends through the guide element 8, which has sliding surfaces 10, 12 running parallel to this longitudinal extension of the steering spindle 3. In this embodiment variant, it is conceivable that the bearing block 7 together with the length of the housing guide shown likewise serves as a mechanical steering end stop, and the bearing block 7 can abut against the end-face abutment surfaces of the guide element 8.In this case, at least one stop element (not shown) made of a plastic, in particular an elastomer, can additionally be provided, which is connected to the bearing block 7, for example by the stop element being placed over the bearing block 7. It would also be possible for a first stop element to be arranged on the bearing block 7, for a second stop element which is stationary with respect to the steering spindle 3 to abut when a predefined offset position is reached in a first offset direction of the bearing block 7, and for a third stop element to be arranged on the bearing block 7, for a fourth stop element which is stationary with respect to the steering spindle 3 when a predefined offset position is reached in a second offset direction of the bearing block 7. The first stop element and the second stop element can be embodied in one piece, in particular also monolithically.It can be seen in FIG. 7 that a first spring cap 21 is arranged between the first sliding element 9 and the first spring element 13, which spring cap transmits the spring force of the first spring element 13 to the first sliding element 9. The spring branch 21 engages in the spiral-shaped first spring element 13, which contributes to an improved guidance of the spring element 13 relative to the spring branch 21. The first spring element 13 then abuts a circumferential, radially outwardly extending collar of the spring cap 21.FIGS. 8-9 show embodiments of the steering gear 1 in which the first sliding surface 10 is shaped such that it exerts a spring force in the direction of the first sliding element 9. For this purpose, the first sliding surface 10 is formed on a first metal sheet 32 which is arranged between the guide element 8 and the first sliding element 9. The first metal sheet 32 has a convex curvature pointing in the direction of the first sliding element 9, which convex curvature brings about the spring force of the first sliding surface 10. A second sheet metal 33 is likewise arranged on the opposite side in order to ensure a sliding friction which is as identical as possible on both sides between the sliding surfaces 10, 12 and the sliding elements 9, 11. The second sheet metal 33 has no curvature and thus also no spring effect.As can be seen in FIG. 9, the resilient action of the first sliding surface 10 can also be brought about by a metal sheet 32 which is bent in a U-shape and has a curvature in the region of the first sliding surface 10. In this case, one free leg of the U-shaped metal sheet 32 then serves as the first sliding surface 10 and the other free leg serves as the second sliding surface 12.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 7 Bearing block 8 Guide element 9 Sliding element 10 Sliding surface 11 Sliding element 12 Sliding surface 13 Spring element 15 Coupling section 16 Receptacle 17 Receiving region 18 Contact section 19 Contact section 20 Contact section 21 Spring cap 22 Sheet metal 23 Sheet metal section 24 Sheet metal section 25 Screw connection 26 Contact section 27 Contact section 28 Receiving region 29 Dome 30 Cylinder section 31 Contact surface 32 Sheet metal 33 Sheet metal

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 such that a rotation of the gear element brings about a linear offset of the steering spindle (3), characterized in that a bearing block (7) is fixed to the steering spindle (3) between the first bearing point (4) and the second bearing point (5), which bearing block extends radially outwards from the lateral surface of the steering spindle (3) and engages into a guide element (8) which is fixed in relation to the steering spindle (3), wherein between the bearing block (7) and the guide element (8) a first sliding element (9) abuts a first sliding surface (10) of the guide element (8) and a second sliding element (11) abuts a second sliding surface (12) of the guide element (8) opposite the first sliding surface (10).Steering gear (1) according to Claim 1, characterized in that the first sliding element (9) is subjected to a spring force by means of a first spring element (13) in the direction of the first sliding surface (10), and / or the second sliding element (11) is subjected to a spring force by means of a second spring element in the direction of the second sliding surface (12).Steering gear (1) according to Claim 1 or 2, characterized in that the first spring element (13) and / or the second spring element is formed as a helical spring.Steering gear (1) according to one of the preceding claims, characterized in that the first sliding element (9) has a coupling section (15), against which the first spring element (13) bears.Steering gear (1) according to one of the preceding claims, characterized in that the bearing block (7) has a first receiving region (17) for the first sliding element (9), wherein the first receiving region (17) has a spherical or cylindrical contact portion (18), on which a corresponding contact portion (19) of the first sliding element (9) bears in such a way that the first sliding element (9) can be pivoted by an angle with respect to the first receiving region (17).Steering gear (1) according to one of the preceding claims, characterized in that the bearing block (7) is formed from a metal sheet (22) and the bearing block (7) formed from a metal sheet (22) has a first metal sheet section (23) and a second metal sheet section (24) running substantially parallel to the first metal sheet section (23), wherein the first metal sheet section (23) carries the first sliding element (9) and the second metal sheet section (24) carries the second sliding element (11).Steering gear (1) according to Claim 6, characterized in that the first sheet-metal section (23) and the second sheet-metal section (24) are designed such that they exert a spring force acting in the direction of the first sliding surface (10) and / or in the direction of the second sliding surface (12) on the first sliding element (9) and / or on the second sliding element (11).Steering gear (1) according to one of the preceding claims, characterized in that a first spring cap (21) is arranged between the first sliding element (9) and the first spring element (13), said spring cap transmitting the spring force of the first spring element (13) to the first sliding element (9).Steering gear (1) according to one of the preceding claims, characterized in that the first sliding surface (10) is shaped in such a way that it exerts a spring force in the direction of the first sliding element (9).Steering gear (1) according to one of the preceding claims, characterized in that a first stop element is arranged on the bearing block (7) and, when a predefined offset position is reached in a first offset direction of the bearing block (7), abuts against a second stop element which is stationary with respect to the steering spindle (3).

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