Steering Gear and Method for Producing the Steering Gear

Abstract

A steering gear for a steering system of a motor vehicle includes a housing, a gear, a pinion which meshes with the gear, and a pinion shaft that includes the pinion. The pinion shaft is mounted in a fixed bearing on a first side of the pinion, the fixed bearing having a rotary bearing in which the pinion shaft is received and which is received in a bearing sleeve of the fixed bearing, and pivoting ring with an outer ring and an inner ring that are pivotably connected via one or more torsion webs. The inner ring is received in the bearing sleeve, and the outer ring is fixedly arranged in the housing. The bearing sleeve is made of plastic. Thus, the bearing sleeve can be produced in a simple manner and the bearing sleeve exhibits a relatively low component weight as a result of the plastic design.

Claims

1-12. (canceled)

13. A steering gear for a steering system of a motor vehicle, comprising: a housing; a gear wheel; a pinion shaft comprising a pinion meshing with the gear wheel; and a fixed bearing supporting the pinion shaft on a first side of the pinion the pinion shaft, the fixed bearing comprising: a first pivot bearing, in which the pinion shaft is received and which is received in a bearing sleeve that is made of plastic and forms a circumferential step; and a swivel ring, which comprises an outer ring and an inner ring, which are pivotably connected together via one or more torsion webs, the inner ring received in the bearing sleeve and the outer ring supported in the housing, wherein a first inside diameter of the circumferential step at a first edge situated in proximity to the first pivot bearing is formed larger than a second inside diameter at a second edge of an annular element, which is arranged between a first outer bearing ring of the first pivot bearing and the circumferential step, the second edge situated in proximity to the circumferential step.

14. The steering gear as claimed in claim 13, wherein: the pinion shaft is supported on a second side of the pinion in a floating bearing, which comprises a second pivot bearing in which the pinion shaft is received and provides a radial mobility for the second pivot bearing inside the housing, and at least one of the bearing sleeve and the first outer bearing ring is connected via a connecting element to the second outer bearing ring.

15. The steering gear as claimed in claim 14, wherein the connecting element defines an opening in at least one longitudinal portion, the gear wheel extending into the opening.

16. The steering gear as claimed in claim 14, wherein the connecting element is formed in one piece with and from the same material as the bearing sleeve.

17. The steering gear as claimed in claim 14, wherein the second pivot bearing is supported inside a portion of the connecting element.

18. The steering gear as claimed in claim 13, wherein the bearing sleeve is formed as an injection-molded component.

19. The steering gear as claimed in claim 13, wherein reinforcing ribs are formed on an outside of the bearing sleeve running in a longitudinal direction.

20. The steering gear as claimed in claim 13, wherein the circumferential step supports a first axial end of the first outer bearing ring.

21. The steering gear as claimed in claim 20, wherein the first inside diameter of the circumferential step, at the first edge, is formed larger than a third inside diameter of the first outer bearing ring at a third edge situated in proximity to the circumferential step.

22. The steering gear as claimed in claim 20, wherein the bearing sleeve further comprises a second circumferential step, which supports a second axial end of the first outer bearing ring.

23. The steering gear as claimed in claim 16, wherein the bearing sleeve and the connecting element are formed as an injection-molded component.

24. The steering gear as claimed in claim 14, wherein reinforcing ribs are formed on an outside of at least one of the bearing sleeve and the connecting element, the reinforcing ribs running in a longitudinal direction.

25. A method for producing a steering gear that includes (i) a housing, (ii) a gear wheel, (iii) a pinion shaft having a pinion meshing with the gear wheel, and (iv) a fixed bearing supporting the pinion shaft on a first side of the pinion the pinion shaft, the fixed bearing including a first pivot bearing, in which the pinion shaft is received and which is received in a bearing sleeve that is made of plastic and forms a circumferential step, and a swivel ring, which comprises an outer ring and an inner ring, which are pivotably connected together via one or more torsion webs, the inner ring received in the bearing sleeve and the outer ring supported in the housing, wherein a first inside diameter of the circumferential step at a first edge situated in proximity to the first pivot bearing is formed larger than a second inside diameter at a second edge of an annular element, which is arranged between a first outer bearing ring of the first pivot bearing and the circumferential step, the second edge situated in proximity to the circumferential step, the method comprising: forming at least one of the bearing sleeve and the connecting element of injection molded plastic.

26. The method as claimed in claim 25, wherein the forming of the at least one of the bearing sleeve and the connecting element further comprises using an annular gate to form the injection molded plastic.

Description

[0033] The invention is explained in more detail below, referring to an exemplary embodiment represented in the drawings, in which:

[0034] FIG. 1: shows a longitudinal section through a steering gear according to the invention in a first embodiment;

[0035] FIG. 2: shows the fixed bearing, the connecting element integrally formed therewith and the stop ring of the steering gear according to FIG. 1 in a perspective view;

[0036] FIG. 3: shows the fixed bearing with integrated connecting element and stop ring according to FIG. 2 in a longitudinal section;

[0037] FIG. 4: in a perspective view shows a fixed bearing, a connecting element integrally formed therewith and a stop ring for a steering gear according to the invention in a second embodiment;

[0038] FIG. 5: shows the fixed bearing, the connecting element and the stop ring according to FIG. 4 in a longitudinal section;

[0039] FIG. 6: in a perspective view shows a fixed bearing for a steering gear according to the invention in a third embodiment; and

[0040] FIG. 7: shows the fixed bearing according to FIG. 6 in a longitudinal section.

[0041] FIG. 1 shows the main constituent parts of a steering gear according to the invention. This comprises a housing 1, inside which a gear wheel 2 and a pinion 3 in the form of a helical pinion meshing with the gear wheel 2 are rotatably arranged. The pinion 3 and a (helical) pinion shaft 4 comprising the pinion 3 are integrally formed as a worm.

[0042] The gear wheel 2 is firmly fixed on an output shaft 5 of the steering gear. This output shaft 5, which in the exemplary embodiment shown comprises a toothing for a secure, rotationally fixed connection to the gear wheel 2, can mesh, for example, with a steering track rod formed at least in one portion as a rack, so that the rack performs a translational movement, which in a known manner can be translated via steering arms (not shown) into a swiveling movement of steered wheels (not shown) of the motor vehicle. The output shaft 5 may also be a steering column of a power-steering system, however, which is connected to a steering wheel and acts on the steering track rod via a steering pinion.

[0043] The pinion shaft 4 has a drive-side end, via which the shaft can be connected to the output shaft of a steering motor (not shown; for example an electric motor). In the area of this drive-side end the pinion shaft 4 is supported in the housing 1 by means of a first bearing. This bearing takes the form of a fixed bearing 6, which allows the pinion shaft 4 to swivel about a swivel axis 7 (cf. FIG. 2). This swivel axis 7 here in FIG. 1 runs approximately perpendicular to the drawing plane. Such swiveling causes a deflection of the opposite end of the pinion shaft 4 to the drive-side end, the shaft there being supported by means of a floating bearing 8 in a corresponding mount of the housing 1. This floating bearing 8 is designed so that it will permit the deflection of this end resulting from the swiveling of the pinion shaft 4.

[0044] Both the fixed bearing 6 and the floating bearing 8 each comprise a pivot bearing in the form of a ball bearing 9. The corresponding portions of the pinion shaft 4 are supported in inner bearing rings 10 of these ball bearings 9, whilst outer bearing rings 11 of the ball bearings 9 are each supported in a bearing device 12, 13, which are in turn received in the housing 1. The bearing devices 12, 13 are designed so that in the case of the fixed bearing 6 they allow the pinion shaft 4 to swivel about the swivel axis 7, and in the case of the floating bearing 8 they allow deflection of the free end of the pinion shaft 4.

[0045] For this purpose, the bearing device 12 of the fixed bearing 6 comprises a bearing sleeve 14 having an annular cross section, which inside, in a first longitudinal portion, receives the associated ball bearing 9, and in a second longitudinal portion an inner ring 16 of a swivel ring 15. This inner ring 16 of the swivel ring 15 and the outer bearing ring 11 of the ball bearing 9 are supported, axially secured, inside the bearing sleeve 14 with the insertion of multiple annular elements 17, the inner ring 16 being supported on the one hand on the outer bearing ring 11 of the ball bearing 9 and on the other on a first circumferential step 26, formed by the bearing sleeve 14 at one axial end, in each case with the insertion of an annular element 17. Similarly, the side of the outer bearing ring 11 of the ball bearing 9 situated remotely from the inner ring 16 of the swivel ring 15 is supported, with the insertion of an annular element 17, on a second circumferential step 27, formed by the bearing sleeve 14 at this axial end.

[0046] Besides the inner ring 16 the swivel ring 15 also comprises an outer ring 18. This outer ring 18 is connected to the inner ring 16 via two torsion webs 19 (cf. FIG. 2). The outer ring 18, the inner ring 16 and the torsion webs 19 are preferably formed in one piece from spring steel, for example.

[0047] The inner bearing ring 10 of the ball bearing 9 of the fixed bearing 6 is axially secured in position on the pinion shaft 4, with the insertion of a thrust piece 20, by means of a bolt 21, which is screwed into an internal thread which is incorporated into the drive-side end of the pinion shaft 4. The outer ring 18 of the swivel ring 15 is axially secured in position inside the housing 1 by means of a threaded ring 22, which has an external thread which is screwed into an internal thread of the housing 1.

[0048] The two torsion webs 19 define the position of the swivel axis 7, about which the outer ring 18 is able to swivel relative to the inner ring 16 of the swivel ring 15. The torsion webs 19 of the swivel ring 15 here not only allow a swiveling of the outer ring 18 relative to the inner ring 16, and hence of the pinion shaft 4 relative to the gear wheel 2 and to the housing 1, but at the same time produce that spring force which presses the pinion 3 into the toothing of the gear wheel 2, in order to achieve the least possible backlash and thereby the minimum possible noise developed in the operation of the steering gear, particularly in alternate steering. This spring force results from the fact that in assembling the steering gear the pinion shaft 4 is deflected so far through contact with the gear wheel 2 that a twisting of the torsion webs 19 occurs, sufficient for the elastic restoring torques resulting from this twisting of the torsion webs 19 to counteract the displacement of the pinion shaft 4 and therefore to impel the latter against the gear wheel 2.

[0049] The bearing device 13 of the floating bearing 8 comprises a stop element in the form of a stop sleeve 23, which is movably arranged inside a receiving space 24 formed by the housing 1, in such a way that the swiveling mobility about a swivel axis 7 defined by the fixed bearing 6 is possible within the limits of a basic design play. Here this basic play or this swiveling mobility is limited in one direction by a full contact or one occurring on two flanks of each of the individual teeth of the pinion 3 and the gear wheel 2, which is brought about by the spring loading by means of the twisted torsion webs 19, and in the other direction by a stop, which is formed by a contact of the annular stop sleeve 23 with a stop element 25 arranged in a receiving aperture of the housing 1. Here the depth to which the stop element 25 extends into the receiving space 24 may be adjustable at least once.

[0050] The steering gear further comprises a connecting element 28, which is materially integrated in one piece into the bearing sleeve 14 of the fixed bearing 6 or formed as an extension thereof. The connecting element 28, as emerges from FIGS. 1 and 3, is of tubular formation with annular or segmental-shaped cross sections and comprises a shell opening 29, which is arranged in a central portion of the connecting element 28 and which extends over a portion of its circumference. Through this shell opening 29 a portion of the gear wheel 2 can extend into the internal volume defined by the connecting element 28 and receiving the pinion shaft 4 in the portion forming, among other things, the pinion 3, in order to allow engagement of the tooth systems of the gear wheel 2 and the pinion 3.

[0051] A tubular end portion of the connecting element 28 extends into the floating bearing 8 of the steering gear, the ball bearing 9 of the floating bearing 8 with the associated outer bearing ring 11 being supported so that it is axially movable inside this end portion of the connecting element 28. This end portion of the floating bearing 28 is in turn internally supported in the stop sleeve 23 of the floating bearing 8. The connecting element 28 together with the stop sleeve 23 therefore forms a bearing bush for the ball bearing 9 of the floating bearing 8.

[0052] The connecting element 28 on the one hand means that the elastic restoring torques, which result from the torsion of the torsion webs 19 of the swivel ring 15 of the fixed bearing 6, are not transmitted to the pinion shaft 4 exclusively via the ball bearing 9 of the fixed bearing 6, which would be associated with a relatively high buckling load of this ball bearing 9. Rather, these elastic restoring torques are transmitted to the ball bearing 9 of the floating bearing 8 primarily via the bearing sleeve 14 of the fixed bearing 6 and the connecting element 28 integrally connected thereto.

[0053] The bearing sleeve 14 of the fixed bearing 6 and the connecting element 28 integrally formed with the bearing sleeve 14 are produced in the form of an injection-molded component from a plastic, in particular a thermoplastic material. In producing this unit comprising the bearing sleeve 14 and the connecting element 28 by injection molding, the ball bearing 9 of the fixed bearing 6, the swivel ring 15 and the total of three annular elements 17 are partially overmolded by the plastic used for this. For this purpose, the inner bearing ring 10 of the ball bearing 9, the inner ring 16 of the swivel ring 15 and the two annular elements 17 in contact with this inner ring 16 are pushed onto a stepped portion of a first core (not shown). A second core (not shown), which is intended, in particular, to form the internal volume of the tubular connecting element 28, in an end portion of reduced diameter carries the third annular element 17 and at the end abuts the end of the inner bearing ring 10 of the ball bearing 9 situated remotely from the swivel ring 15. After positioning of the cores and the components carried by them, that is to say the ball bearing 9, the swivel ring 15 and the annular elements 17, inside a cavity of an injection molding tool (not shown), the free-flowing plastic can be introduced into the injection molding tool with the additional use of a radially movable slide valve (not shown), which forms the shell opening 29 of the connecting element 28, and brought to final curing. The gating here may preferably be performed annularly in the area of one of the axial ends of the injection molded component to be produced or via a plurality of injection points distributed over a circumference of the injection molded component or the cavity of the injection mold. A central gate (for example, diaphragm gate or disk gate) is also possible. Due to the fact that the inside diameter of the steps 26, formed by the bearing sleeve 14 is greater than the inside diameter of the annular elements 17 adjoining each of these (in each case relative to the near edge), the free-flowing plastic is prevented from getting into the ball bearing 9 during the injection molding process.

[0054] The setting and cooling of the plastic causes a shrinkage of the bearing sleeve 14, which elastically acts radially and axially on the contiguous arrangement of the outer bearing ring 11 of the ball bearing 9, the inner ring 16 of the swivel ring 15 and the three annular elements 17, thereby achieving an absence of play which has an advantageous effect on the noise behavior of the steering gear in operation.

[0055] The sub-assembly comprising the ball bearing 9 of the fixed bearing 6, the swivel ring 15, the annular elements 17 and the unit comprising the bearing sleeve 14 and the connecting element 28 can be removed from the mold in an axial direction relative to the longitudinal axis 30 once the slide valve, which is intended to form the shell opening 29, has been retracted.

[0056] The stop sleeve 23 of the floating bearing 8 is likewise composed of a thermoplastic material, which is relatively more elastic, however, compared to the plastic from which the unit, comprising the bearing sleeve 14 and the connecting element 28, is formed. This is intended to dampen noise generated due to contact with the stop element 25 during operation of the steering gear. The stop sleeve 23 may be produced separately, for example likewise by means of injection molding, and subsequently mounted on the corresponding end portion of the connecting element 28 and connected to the latter. Alternatively, however, it is also possible to produce the stop sleeve 23 and the unit comprising the bearing sleeve 14 and the connecting element 28 in the form of an integral injection molded component by a 2-component injection molding process.

[0057] As can be seen from FIG. 2 in particular, multiple reinforcing ribs 31, which are distributed at uniform intervals in a circumferential direction over the respective outer surface and which extend in a longitudinal direction of the bearing sleeve 14 or the connecting element 28 and run substantially parallel to the longitudinal axis 30, are formed on the outside of the bearing sleeve 14 and on the outside of the connecting element 28. The reinforcing ribs 31 of the bearing sleeve 14 here extend into the end face of the bearing sleeve 14 situated remotely from the connecting element 28, and into the end face which is situated in proximity to the connecting element 28 and which represents the external circumferential step that is formed in the transition between the bearing sleeve 14 and the connecting element 28. In these end faces the reinforcing ribs 31 run radially. The reinforcing ribs 31 of the bearing sleeve 14 and of the connecting element 28, which in each case merge in pairs into one another, are in particular intended to ensure a relatively high flexural stiffness for a simultaneously relatively low component weight of the unit comprising the bearing sleeve 14 and the connecting element 28.

[0058] FIGS. 4 and 5 represent a unit comprising a fixed bearing 6, a connecting element 28 and a stop sleeve 23 for a steering gear according to the invention in a second embodiment. With the exception of the connecting element 28 this steering gear may correspond to the steering gear according to FIG. 1. The connecting element 28 according to FIGS. 4 and 5 differs from that of the steering gear according to FIGS. 1 to 3 in that in that longitudinal portion in which this forms a (shell) opening 29, which allows a toothing engagement of the pinion 3 and the gear wheel 2, is formed with point-symmetrical cross-sectional areas. This is achieved in that the connecting element 28 in this longitudinal portion comprises an identically shaped shell opening 29 situated opposite said shell opening 29. In this longitudinal portion the shell of the connecting element is consequently reduced to two connecting braces, which have identical dimensions and are arranged offset by 180 about the longitudinal axis 30 or situated opposite one another. These connecting braces also have external reinforcing ribs 31.

[0059] FIGS. 6 and 7 show the fixed bearing 6 for a steering gear according to the invention in a third embodiment. This basically corresponds to the fixed bearing 6 of the steering gear according to FIGS. 1 to 3. There is no provision, however, for forming the bearing sleeve 14 of this fixed bearing 6 in one piece with a connecting element 28 and from the same material. A steering gear not further represented and comprising this fixed bearing 6, and which may otherwise correspond to that according to FIG. 1, for example, may be formed without such a connecting element 28. Alternatively, a separately formed connecting element 28 may subsequently be connected to the bearing sleeve 14 of the fixed bearing 6, in turn formed as a plastic injection molded component, according to FIGS. 6 and 7.

LIST OF REFERENCE NUMERALS

[0060] 1. housing [0061] 2. gear wheel [0062] 3. (helical) pinion [0063] 4. (helical) pinion shaft [0064] 5. output shaft of the steering gear [0065] 6. fixed bearing [0066] 7. swivel axis [0067] 8. floating bearing [0068] 9. ball bearing [0069] 10. inner bearing ring of a ball bearing [0070] 11. outer bearing ring of a ball bearing [0071] 12. bearing device of the fixed bearing [0072] 13. bearing device of the floating bearing [0073] 14. bearing sleeve [0074] 15. swivel ring [0075] 16. inner ring of the swivel ring [0076] 17. annular element [0077] 18. outer ring of the swivel ring [0078] 19. torsion web [0079] 20. thrust piece [0080] 21. bolt [0081] 22. threaded ring [0082] 23. stop sleeve [0083] 24. receiving space [0084] 25. stop element [0085] 26. first step of the bearing sleeve [0086] 27. second step of the bearing sleeve [0087] 28. connecting element [0088] 29. shell opening [0089] 30. longitudinal axis of the connecting element, the bearing sleeve, the ball bearings, the annular elements and the pinion shaft [0090] 31. reinforcing rib