Steering gear, steering system and method for manufacturing a swivel ring for a steering gear

Abstract

Steering gear for a steering system of a motor vehicle with - a housing (1), - a gear (2), - a pinion (3) meshing with the gear (2) and - a pinion shaft (4) comprising the pinion (3), wherein the pinion shaft (4) is supported on one side of the pinion (3) in a fixed bearing (6) comprising a rotary bearing (11) in which the pinion shaft (4) is received and which is received in a bearing sleeve (15), and wherein the fixed bearing (6) further comprises a pivot ring (16) having an outer ring (18) and an inner ring (17) which are pivotably connected to each other about a pivot axis (7) defined by the torsion web(s) (19) via one or more torsion webs (19), wherein the inner ring (17) is received in the bearing sleeve (15) and the outer ring (18) is supported in the housing (1), characterized in that the axial width of the torsion webs (19) and of first sections (27) of the outer ring radially adjacent to the torsion webs (19) (18) and of the inner ring (17) is smaller than the axial width of the first sections (27) adjacent in the two circumferential directions,second sections (28) of the outer ring (18) and the inner ring (17).,

Description

[0001] The invention relates to a steering gear for a steering system of a motor vehicle and to a method for manufacturing a swivel ring for such a steering gear. It also relates to a steering system with a steering gear.

[0002] Most motor vehicles are equipped with power steering systems that generate a supporting torque when steering, thereby reducing the steering torque that the driver has to apply to the steering column.

[0003] The known power steering systems are based on a steering gear that translates the drive power of a hydraulic or electric steering motor and transmits it to, for example, the steering column of a motor vehicle. Such steering gears are typically designed as helical gears, and in particular as helical gears or worm gears. These comprise a gear that is directly or indirectly connected to the steering column, and a pinion that meshes with it and is driven by the steering motor via a shaft.

[0004] Gear backlash has proven problematic in such steering gears, developing due to component tolerances, differing thermal expansion of the gear elements, wear, and / or settling of the material in plastic gears. Particularly during so-called alternating steering maneuvers, i.e., consecutive steering inputs with changing steering directions, such gear backlash generates undesirable noise resulting from the alternating engagement of opposing flanks of the pinion and gear teeth.

[0005] It is known to eliminate this backlash by mounting the pinion shaft so that it can pivot about an axis perpendicular to the longitudinal axis of the pinion shaft and at a distance from the meshing of the pinion and gear, and by pressing it against the gear by means of one or more spring elements. The pivoting capability of the pinion shaft is typically integrated into one of the two bearings at its ends. This bearing is called the "fixed bearing." The bearing at the other end is then designed with a defined degree of movement (the so-called "floating bearing") to accommodate the deflection caused by the pivoting motion. The fixed bearing can be located, in particular, on the drive side, while the floating bearing is located at the free end of the pinion shaft.The spring element(s) for pressing the pinion against the gear can be integrated into either the floating bearing or the fixed bearing.

[0006] Such a steering gear, in which the spring force for the rebound is generated by means of the fixed bearing, is known, for example, from DE 10 2009 054 655 A1. In this steering gear, the rolling bearing that supports the pinion shaft in the area of ​​the fixed bearing is mounted externally in a pivot sleeve. The pivot sleeve comprises a bearing sleeve that supports the rolling bearing with minimal play and an outer ring that is held with minimal play in a receptacle of a steering gear housing. The outer ring and the bearing sleeve are connected by several torsion bars, which are twisted when the outer ring is rotated relative to the bearing sleeve. After assembly of the steering gear, the torsion bars are twisted in such a way that the resulting elastic restoring effect causes the rebound of the pinion shaft.

[0007] Designs of steering gears similar to that of DE 10 2009 054 655 A1 are known from DE 10 2008 040 673 A1 and DE 10 2012 103 146 A1.

[0008] DE 10 2013 104 521 A1 discloses a helical gear drive for a steering system, wherein a swivel ring is arranged on the fixed bearing, the swivel ring having an outer ring and an inner ring, the rings being pivotably connected via torsion bars. The document deals with simplifying the assembly of the swivel ring.

[0009] EP 1 767 797 A2 discloses a ball screw drive for a steering system. The ball screw drive has a ball bearing which is pivotally mounted by a spring washer.

[0010] DE 10 2016 104 150 A1 discloses a helical gear drive for a steering system, wherein a pivot ring is arranged on the fixed bearing, the pivot ring having an outer ring and an inner ring, the rings being pivotably connected via torsion bars. The document deals with making the stiffness of the spring mechanism variable by making the effective bar length dependent on the load through corresponding support surfaces.

[0011] The invention was based on the objective of improving the noise behavior of a steering gear, as is generally known from the aforementioned publications.

[0012] This problem is solved by means of a steering gear according to claim 1 and by means of a steering system according to claim 7. A method for manufacturing a swivel ring for such a steering gear is the subject of claim 6. Advantageous embodiments of the steering gear and the steering system according to the invention, as well as preferred embodiments of the method according to the invention, are the subject of further claims and / or will become apparent from the following description of the invention.

[0013] According to the invention, a steering gear for a motor vehicle's steering system comprises a housing, a gear, a pinion meshing with the gear, and a pinion shaft encompassing the pinion, wherein the pinion shaft is supported on one side of the pinion in a fixed bearing. The fixed bearing includes a rotary bearing, preferably a rolling bearing and in particular a ball bearing, in which the pinion shaft is received and which is received in a bearing sleeve. The fixed bearing further comprises a pivot ring having an outer ring and an inner ring, which are pivotably connected to one another about a pivot axis defined by the torsion bar(s) via one or more torsion bars, wherein the inner ring is received in the bearing sleeve and the outer ring is supported within the housing.Furthermore, it is provided that the axial width of the (individual) torsion bars and of the first sections of the outer ring and the inner ring adjacent to the torsion bars in each direction is smaller than the respective axial width of the second sections of the outer ring and the inner ring adjacent to the first sections in the two circumferential directions.This ensures that the torsion bars and the first sections adjacent to them radially to the pivot ring are arranged at a defined distance from the components axially adjacent to the pivot ring. With appropriate dimensioning, this allows for movements of the torsion bars and the first sections resulting from the operation of the steering gear with the inherent torsion of the torsion bars, based on deformation of the pivot ring, without contact and, in particular, contacting relative movement between the torsion bars and the first sections of the pivot ring with the axially adjacent components of the steering gear. Consequently, noise and wear caused by such contact during operation of the steering gear can be avoided.

[0014] According to a preferred embodiment of a steering gear according to the invention, at least one, preferably both, of the axial end faces of the outer ring and / or the inner ring (each) forms a contact surface (preferably a single one) lying in a radial plane, wherein the (each) corresponding first section is designed as a recess with respect to this contact surface. The recess can preferably be designed in the form of a circular arc segment.

[0015] According to a further preferred embodiment of a steering gear according to the invention, which can be particularly distinguished with regard to the advantageous manufacturability of the associated swivel ring, it can be provided that the outer ring, the inner ring, and the torsion webs have rectangular cross-sectional areas. The cross-sections refer to the cross-sectional surfaces transverse to the longitudinal extent of the torsion webs connecting the outer ring and the inner ring of the swivel ring, or to the circumferential extent of the outer ring and the inner ring.

[0016] To manufacture a swivel ring of a steering gear according to the invention, a method according to the invention can provide that the outer ring, the inner ring, and the torsion webs are formed in one piece by stamping a sheet metal component, and the relatively small axial width of the torsion webs and the first sections of the outer ring and the inner ring is formed by machining and / or forming. The machining and / or forming can be carried out before or, preferably, after stamping.

[0017] The invention further relates to a steering system comprising a steering gear according to the invention and a steering motor connected to the pinion shaft of the steering gear in a rotationally driven manner. The gear of the steering gear can further be connected to a steering shaft, in particular a steering column, of the steering system in a rotationally fixed or rotationally driven manner.

[0018] The steering system according to the invention can in particular be designed as an auxiliary steering system, by means of which a supporting torque can be generated by the steering motor, so that the steering torque to be applied to the steering column by a driver of a motor vehicle comprising the auxiliary steering system is reduced (possibly even temporarily to zero). Alternatively, it is also possible to design the steering system such that the steering motor always generates the entire steering torque required for steering.

[0019] A method for manufacturing a steering gear or steering system according to the invention comprises at least the assembly of the associated components.

[0020] The invention also relates to a motor vehicle with a steering system according to the invention.

[0021] The indefinite articles (“a”, “an”, “one”, and “ones”), particularly in the patent claims and in the description generally explaining the patent claims, are to be understood as such and not as numerals. Accordingly, components specified by these articles are to be understood as existing at least once and potentially existing multiple times.

[0022] The invention is explained in more detail below with reference to an embodiment illustrated in the drawings. The drawings show: Fig. 1: a longitudinal section through a steering gear according to the invention; Fig. 2: the bearing device of the fixed bearing of the steering gear according to the Fig. 1 in a perspective view Fig. 3: the swivel ring of the bearing device according to the Fig. 2 in a perspective view; and Fig. 4: the storage device according to the Fig. 2 in a longitudinal section.

[0023] The Fig. Figure 1 shows the essential components of a steering gear according to the invention for a steering system of a motor vehicle. This comprises a housing 1, within which a gear 2 and a worm gear 3 meshing with the gear 2 are mounted. The worm gear 3 and a worm gear shaft 4 encompassing the worm gear 3 are integrally formed in the form of a worm.

[0024] The gear 2 is fixedly mounted on an output shaft 5 of the steering gear. This output shaft 5, which in the illustrated embodiment has a toothed connection for a rotationally fixed connection with the gear 2, can include a steering pinion (not shown) at one end. This pinion meshes, for example, with a steering rod (not shown), which is designed as a rack at least in one section. As the output shaft 5 rotates, the steering rod undergoes a translational movement, which can be translated in a known manner via steering arms (not shown) into a pivoting movement of the steered wheels (not shown) of the vehicle. Alternatively, the output shaft 5 can also be a steering column of the power steering system, which is rotationally fixed to a steering wheel (not shown) and acts on a steering rod via a steering pinion (not shown).

[0025] The helical pinion shaft 4 has a drive-side end via which it can be connected to the output shaft of a steering motor (e.g., an electric motor) not shown. In the region of this drive-side end, the helical pinion shaft 4 is supported in the housing 1 by means of a first bearing. This bearing is designed as a fixed bearing 6, which prevents the helical pinion shaft 4 from pivoting about a pivot axis 7 (see figure). Fig. 2 and Fig. 3) allows. This pivoting causes the free end of the screw pinion shaft 4, opposite the drive-side end, to deflect, where it is supported by a floating bearing 8. This floating bearing 8 is designed such that it allows the deflection of this free end of the screw pinion shaft 4 resulting from the pivoting of the screw pinion shaft 4 within limits.

[0026] The fixed bearing 6 comprises a bearing assembly 9. This bearing assembly 9 and a bearing assembly 10 of the floating bearing 8 each comprise a rotary bearing 11, 12 in the form of a ball bearing. In inner bearing rings 13 of these rotary bearings 11, 12, corresponding sections of the helical pinion shaft 4 are mounted, while outer bearing rings 14 of the rotary bearings 11, 12 are each mounted in a bearing sleeve 15 of the bearing assemblies 9, 10, which in turn are received in the housing 1. The bearing assemblies 9, 10 are designed such that, in the case of the fixed bearing 6, they allow the helical pinion shaft 4 to pivot about the pivot axis 7, and in the case of the floating bearing 8, they allow the free end of the helical pinion shaft 4 to deflect.

[0027] The bearing assembly 9 of the fixed bearing 6 comprises the associated bearing sleeve 15 with annular cross-sectional surfaces, which on the inside accommodates, in a first longitudinal section, the inner bearing ring 13 of the associated rotary bearing 11 and, in a second longitudinal section, an inner ring 17 of a swivel ring 16. The inner ring 17 of the swivel ring 16 is arranged within, specifically between two axial stops 20 of the bearing sleeve 15, with a support disk 21 interposed, in a rotationally fixed and axially secured manner. The inner ring 17 of the swivel ring 16 is supported on one side by the support disk 21 and on the other side by the outer bearing ring 14 of the rotary bearing 11. In addition to the inner ring 17, the swivel ring 16 also comprises an outer ring 18. This outer ring 18 is connected to the inner ring 17 via two torsion bars 19 (see figure). Fig. 2 to 4), wherein the torsion webs 19 extend through appropriately positioned through-openings 26 in the bearing sleeve 15. The outer ring 18, the inner ring 17 and the torsion webs 19 are formed in one piece from, for example, spring steel.

[0028] An axial positional locking of the rotary bearing 11 of the fixed bearing 6 on the helical pinion shaft 4 is achieved by means of a coupling piece 22 and a screw 23, which is screwed into an internal thread integrated into the corresponding end of the helical pinion shaft 4. The coupling piece 22 also serves to transmit drive power from the steering motor to the helical pinion shaft 4, for which purpose they are rotationally fixed together. This rotationally fixed connection is achieved by the engagement of an external toothing of the helical pinion shaft 4 with a complementary internal toothing of the coupling piece 22.

[0029] An axial position securing of the outer ring 18 of the swivel ring 16 within the housing 1 is achieved by means of a screw ring 24, which has an external thread that is screwed into a corresponding internal thread of the housing 1.

[0030] The two torsion bars 19 define the position of the pivot axis 7, about which the outer ring 18 can pivot relative to the inner ring 17 to provide spring support to the screw pinion shaft 4. However, the torsion bars 19, and thus the pivot axis 7, do not pass through the center of the pivot ring 16 and therefore the cross-section of the screw pinion shaft 4, but are radially offset from it (see figure). Fig. 2 and Fig. 3) The pivot axis 7 therefore does not intersect the longitudinal axis 25 of the screw pinion shaft 4. Due to the radial offset of the torsion webs 19 to the center of the pivot ring 16, the pivot axis 7 is displaced to the vicinity of the outer circumference of the screw pinion shaft 4, thereby reducing or preventing the formation of reaction moments that result from the gear forces arising during the meshing of the screw pinion 3 and gear 2 in conjunction with the distance of the line of action of these gear forces from the pivot axis 7.

[0031] The torsion bars 19 of the swivel ring 16 not only allow the outer ring 18 to pivot relative to the inner ring 17 and thus the pinion shaft 4 relative to the gear 2 or the housing 1, but also simultaneously generate the spring force that presses the pinion 3 of the pinion shaft 4 into the teeth of the gear 2 in order to achieve minimal backlash and thus minimal noise during operation of the steering gear, especially during so-called changeover steering. This spring force results from the fact that, during assembly of the steering gear, the pinion shaft 4 is deflected by contact with the gear 2 to such an extent that a defined torsion of the torsion bars 19 occurs. The elastic restoring moments resulting from this torsion of the torsion bars 19 act against the deflection of the pinion shaft 4 and thus exert force on it against the gear 2.

[0032] To manufacture the swivel ring 16, it is provided that it is formed from a sheet metal component by stamping and that two circular arc segments, each comprising one of the torsion webs 19 and first sections 27 of the outer ring 18 and the inner ring 17, are machined on both sides, i.e., on the two axial end faces, by machining and in particular by milling, in order to reduce the axial width of the swivel ring 16 in the area of ​​the torsion webs 19 and the first sections 27 compared to the rest of the swivel ring 16 or compared to the second sections 28 adjacent to the first sections 27 on both sides in the circumferential direction. As a result, the first sections 27 each form a circular arc segment-shaped recess with respect to the adjacent second sections 28, which are part of a single contact surface 30 lying in a radial plane.These two contact surfaces 30 of the outer ring 18 and the inner ring 17 serve for direct contact with those components of the steering gear that adjoin the swivel ring 16. With regard to the outer ring 18, these are, on one side, the housing 1 and, on the other side, the screw ring 24; with regard to the inner ring 17, on the other hand, the outer bearing ring 14 of the rotary bearing 11 and, on the other hand, the support washer 21.

[0033] Due to the relatively small axial width of the swivel ring 16 in the area of ​​the torsion webs 19 and the radially adjacent first sections 27 of the outer ring 18 and the inner ring 17, gaps 31 are formed between the swivel ring 16 and the adjacent components of the steering gear, thus preventing direct contact between these components. This has a positive effect on the noise behavior during operation of the steering gear and on wear, since the functionally intended torsion of the torsion webs 19 and the relatively small but not irrelevant axial deformation of the swivel ring 16 resulting from a pivoting movement of the screw pinion shaft 4 are possible without contact and, in particular, without a contacting relative movement between the deforming sections of the swivel ring 16 and the adjacent components.

[0034] In addition to the stamping process and the machining, only one further step is required for the manufacture of the swivel ring 16 to form an anti-rotation projection 32 (see below). Fig. 1) provided, which is designed to engage in a corresponding recess of the housing 1 in order to prevent the swivel ring 16 from rotating about its longitudinal axis.

[0035] To manufacture the bearing assembly 9 of the fixed bearing 6, a tubular workpiece is provided to form the bearing sleeve 15, and a first of the axial stops 20, specifically the stop 20 adjacent to the rotary bearing 11, is formed by deforming a first end section of the workpiece so that this end section projects radially inwards. Subsequently, the rotary bearing 11, the inner ring 17 of the swivel ring 16, and the support disc 21 are inserted into the bearing sleeve 15 starting from the still open end, i.e., the end that does not yet form an axial stop 20. Then, the second axial stop 20 is also formed by deformation, thereby securing the components received within the bearing sleeve 15, i.e., the outer bearing ring 14 of the rotary bearing 11 or the entire rotary bearing 11, the inner ring 17 of the swivel ring 16 or the entire swivel ring 16, and the support disc 21, in their positions. Reference symbol list 1 case 2 gear 3 screw pinions 4 screw pinion shaft 5 Output shaft 6 fixed bearings 7 Swivel axis 8 loose bearings 9 Bearing device of the fixed bearing 10. Bearing device of the loose bearing 11 Swivel bearings of the fixed bearing 12 pivot bearings of the floating bearing 13 inner bearing ring of a rotary bearing 14 outer bearing ring of a rotary bearing 15 Bearing sleeve 16 Swivel ring 17 Inner ring of the swivel ring 18 Outer ring of the swivel ring 19 Torsion bridge 20 axial stop of the bearing sleeve 21 Support disc 22 Coupling piece 23 screw 24 screw rings 25 Longitudinal axis of the screw pinion shaft 26 Through opening of the bearing sleeve 27 first section of the inner ring and the outer ring of the swivel ring 28 second section of the inner ring and the outer ring of the swivel ring 29 In-depth study 30 Mounting surface of the swivel ring 31 gap 32 Anti-rotation projection

Claims

[1] Steering gear for a steering system of a motor vehicle with - a housing (1), - a gear (2), - a pinion (3) meshing with the gear (2) and - a pinion shaft (4) comprising the pinion (3), wherein the pinion shaft (4) is supported on one side of the pinion (3) in a fixed bearing (6) comprising a rotary bearing (11) in which the pinion shaft (4) is received and which is received in a bearing sleeve (15), and wherein the fixed bearing (6) further comprises a pivot ring (16) having an outer ring (18) and an inner ring (17) which are pivotably connected to each other about a pivot axis (7) defined by the torsion bars (19) via one or more torsion bars (19), wherein the inner ring (17) is received in the bearing sleeve (15) and the outer ring (18) is supported in the housing (1), characterized by, that the axial width of the torsion bars (19) and of the first sections (27) of the outer ring (18) and the inner ring (17) adjacent radially to the torsion bars (19) is smaller than the axial width of the second sections (28) of the outer ring (18) and the inner ring (17) adjacent to the first sections (27) in the two circumferential directions. [2] Steering gear according to claim 1, characterized by , that at least one of the axial end faces of the outer ring (18) and / or the inner ring (17) forms a contact surface (30) lying in a radial plane, wherein the associated first section (27) is formed as a recess (29) with respect to this contact surface (30). [3] Steering gear according to claim 2, characterized by, that both of the axial end faces of the outer ring (18) and the inner ring (17) form a contact surface (30) lying in a radial plane, wherein the respective first section (27) is formed as a recess (29) with respect to this contact surface (30). [4] Steering gear according to claim 2 or 3, characterized by , that the depression (29) has the shape of a circular arc segment. [5] Steering gear according to one of the preceding claims, characterized by , that the outer ring (18), the inner ring (17) and the torsion webs (19) have rectangular cross-sectional areas. [6] Method for manufacturing a swivel ring for a steering gear according to claim 5, characterized by, that the outer ring (18), the inner ring (17) and the torsion webs (19) are formed in one piece by stamping a sheet metal component and the axial width of the torsion webs (19) and the first sections (27) of the outer ring (18) and the inner ring (17) are formed by machining and / or forming. [7] Steering system comprising a steering gear according to one of claims 1 to 5 and a steering motor connected to the pinion shaft (4) of the steering gear in a rotary-driving manner.

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