Method for Preparing a Steering Gear for Subsequent Use, and Steering Gear

Abstract

A method is disclosed for preparing a steering gear for subsequent use as part of a steering system of a motor vehicle, the steering gear includes at least a gear and a pinion meshing with the gear, and at least the teeth of the gear and/or of the pinion being made of plastic. The pinion is first pressed against the gear by way of a first force, while at the same time the pinion and the gear are rotated first in a first direction of rotation and subsequently in the second direction of rotation. The first force is preferably selected so high that plastic deformation of the plastic of the pinion and/or of the gear is achieved. Subsequently, the pinion is pressed against the gear by way of a second, defined force, which is less than the first force, the second force being permanently set.

Claims

1. A method for preparing a steering gear mechanism for subsequent use as part of a steering system of a motor vehicle, wherein the steering gear mechanism has (i) a gear having gear teeth, and (ii) a pinion having pinion teeth which meshes with the gear teeth, and wherein at least the gear and/or the pinion teeth are formed from plastics material, comprising: (a) pressing the pinion with a first force against the gear; (b) during step (a), rotating the pinion and the gear in a first rotation direction and subsequently in a second rotation direction; and (c) after step (b), pressing the pinion with a second force which is smaller than the first force against the gear, wherein this second force is permanently adjusted.

2. The method as claimed in claim 1, wherein the first force is selected to be so high that a plastic deformation of the plastics material of the gear and/or of the pinion is achieved.

3. The method as claimed in claim 1, wherein step (b) includes rotating the pinion and the gear in the first rotation direction and/or in the second rotation direction until the gear has carried out at least one complete revolution.

4. The method as claimed in claim 1, wherein step (a) further includes subjecting the gear and/or the pinion at least temporarily to an atmosphere which differs from ambient atmosphere.

5. The method as claimed in claim 1, wherein step (a) further includes introducing a contact mechanism into the tooth engagement of the pinion and gear at least during step (a) so as to influence friction in the tooth engagement.

6. (canceled)

7. A steering gear mechanism for a steering system of a motor vehicle, comprising: a housing, a gear having gear teeth, a pinion shaft including a pinion having pinion teeth which meshes with the gear teeth, wherein at least the gear teeth and/or the pinion teeth are formed from plastics material wherein the pinion shaft is supported at one side of the pinion in a fixed bearing which comprises a rotary bearing in which the pinion shaft is received, wherein the fixed bearing enables a pivoting of the pinion shaft about a pivot axis which is orientated perpendicularly to the rotation axis and at the other side of the pinion is supported in a movable bearing which comprises a rotary bearing, in which the pinion shaft is received, wherein for the rotary bearing a movability within the housing with regard to the pivoting movability of the pinion shaft which is guided by the fixed bearing is ensured, and wherein an adjustment device which is integrated in the fixed bearing and/or in the movable bearing and by way of which a force with which the pinion shaft is pressed against the gear can be adjusted in a variable manner.

8. The steering gear mechanism as claimed in claim 7, wherein: the rotary bearing of the fixed bearing is received in a fixed bearing sleeve and the fixed bearing further comprises a pivot ring which has an outer ring and an inner ring which are connected to each other by way of one or more torsion webs so as to be able to be pivoted about the pivot axis defined by the one or more torsion webs, the inner ring is received in the fixed bearing sleeve and the outer ring is supported inside the housing, and the adjustment device is further constructed in such a manner that using it the position of the outer ring of the pivot ring can be adjusted inside the housing with respect to the directions which are orientated perpendicularly to the longitudinal axis of the outer ring and perpendicularly to the pivot axis.

9. The steering gear mechanism as claimed in claim 8, wherein: the adjustment device comprises a first bearing journal whose longitudinal axis is orientated perpendicularly to the longitudinal axis of the outer ring and to the pivot axis and which connects the outer ring of the pivot ring to a bearing location of the housing, and the bearing location comprises means for fixing the first bearing journal in different positions with respect to the longitudinal axis thereof.

10. The steering gear mechanism as claimed in claim 9, wherein the means for fixing the first bearing journal comprises a threaded element which has a thread which cooperates with a counter-thread of the bearing location.

11. The steering gear mechanism as claimed in claim 9, further comprising: a second bearing journal which is arranged radially opposite the first bearing journal with respect to the longitudinal axis of the outer ring and which is supported along the longitudinal axis thereof so as to be able to be moved in the outer ring or in the housing.

12. The steering gear mechanism as claimed in claim 11, wherein the bearing journals are orientated coaxially relative to each other with respect to the longitudinal axes thereof.

13. The steering gear mechanism as claimed in claim 10, wherein the bearing journals are rotatably supported about the longitudinal axes thereof in the outer ring or in the housing.

14. The steering gear mechanism as claimed in claim 9, wherein the outer ring of the pivot ring has a tubular portion, on which the bearing journals are arranged.

15. The steering gear mechanism as claimed in claim 14, wherein the bearing journals are received as separate components in an opening or recess of the tubular portion.

Description

[0034] The invention is explained in greater detail below with reference to an embodiment of a steering gear mechanism according to the invention as illustrated in the drawings, in which:

[0035] FIG. 1: is a longitudinal section through the steering gear mechanism;

[0036] FIG. 2: is a perspective view of a bearing device of a fixed bearing and a movable bearing and a pinion shaft the steering gear mechanism;

[0037] FIG. 3: is a view of the steering gear mechanism without the associated housing in the viewing direction III in FIG. 1; and

[0038] FIG. 4: is a cross-sect ion through the steering gear mechanism along the plane of section IV-IV in FIG. 1.

[0039] FIG. 1 shows the significant components of a steering gear mechanism according to the invention. It comprises a housing 1, inside which a gear 2 and a pinion 3 which meshes with the gear 2 and which is in the form of a helical pinion are rotatably arranged. The pinion 3 and a (helical) pinion shaft 4 which comprises the pinion 3 are constructed integrally the form of a worm. At least a portion forming the teeth of the gear 2 comprises plastics material. However, the pinion 3 or the entire pinion shaft 4 is preferably constructed from metal and in particular steel.

[0040] The gear 2 is securely fixed to an output shaft 5 of the steering gear mechanism. This output shaft 5 which in the embodiment shown has a tooth arrangement for a secure, rotationally fixed connection to the gear 2 may, for example, mesh with a steering rod which is formed in at least one portion as a toothed rack, whereby the toothed rack carries out a translational movement which in known manner can be converted by means of wheel steering levers (not illustrated) into a pivot movement of steerable wheels (not illustrated) of the motor vehicle. The output shaft 5 may, however, also be a steering column of a power-assisted steering system which is connected to a steering wheel and which acts via a steering pinion on the steering rod.

[0041] The pinion shaft 4 has a drive-side end, via which it can be connected in a rotationally secure manner to the output shaft of a steering motor (not illustrated; for example, an electric or hydraulic motor). In the region of this drive-side end, the pinion shaft 4 is supported by means of a first bearing in the housing 1. This bearing is constructed as a fixed bearing 6, which permits a pivoting of the pinion shaft 4 about a pivot axis 7 (cf. FIGS. 2 and 3). This pivot axis 7 extends in this instance in FIG. 1 perpendicularly to the drawing plane. Such a pivoting brings about a deflection of the end of the pinion shaft 4 opposite the drive-side end, which pinion shaft 4 is supported at that location by means of a movable bearing 8 within the housing 1. This movable bearing 8 is constructed in such a manner that it permits the deflection of this end of the pinion shaft 4, as results from the pivoting of the pinion shaft 4.

[0042] Both the fixed bearing 6 and the movable bearing 8 each comprise a rotary bearing 9 in the form of a ball bearing.

[0043] The corresponding portions of the pinion shaft 4 are supported in inner bearing rings 10 of these rotary bearings 9, whilst external bearing rings 11 of the rotary bearings 9 are supported in a bearing device 12, 13 in each case which are in turn received within the housing 1. The bearing devices 12, 13 are structurally constructed in such a manner that they permit in the case of the fixed bearing 6, inter alia, the pivoting of the pinion shaft 4 about the pivot axis 7 and in the case of the movable bearing 8 the deflection of the free end of the pinion shaft 4.

[0044] To this end, the bearing device 12 of the fixed bearing 6 comprises a fixed bearing sleeve 14 with circular-ring-like cross-sections which receives at the inner side in a first longitudinal portion the associated rotary bearing 9 and in a second longitudinal portion an inner ring 16 of a pivot ring 15. This inner ring 16 of the pivot ring 15 and the outer bearing ring 11 of the rotary bearing 9 of the fixed bearing 6 are supported so as to be axially

[0045] secured within the fixed bearing sleeve 14 with two annular disks 17 being interposed, wherein the inner ring 16 of the pivot ring 15 is supported, with the annular disks 17 being interposed, on the one hand, on the outer bearing ring 11 of the rotary bearing 9 and, on the other hand, on a first peripheral shoulder which is formed by the fixed bearing sleeve 14 at an axial end. In the same manner, the side of the outer bearing ring 11 of the rotary bearing 9, which side is distally located from the inner ring 16 of the pivot ring 15, is supported on a second, peripheral shoulder which is formed by the fixed bearing sleeve 14 at the other axial end.

[0046] The pivot ring 15 also comprises in addition to the inner ring 16 an outer ring 19. This outer ring 19 is connected to the inner ring 16 by means of two torsion webs 20 (cf. FIGS. 2 and 3). The outer ring 19, the inner ring 16 and the torsion webs 20 are constructed integrally, for example, from spring steel.

[0047] The two torsion webs 20 define the position of the pivot axis 7, about which the outer ring 19 can be pivoted relative to the inner ring 16 of the pivot ring 15. The torsion webs 20 of the pivot ring 15 enable in this instance not only a pivoting of the outer ring 19 relative to the inner ring 16 and consequently of the pinion shaft 4 relative to the gear 2 or the housing 1, but also bring about at the same time the resilient force by means of which the pinion 3 is pressed into the tooth arrangement of the gear 2 in order to achieve the smallest possible gear play and consequently the smallest possible generation of noise during operation of the steering gear mechanism, in particular during alternating steering. This resilient force results from the fact that, during the assembly of the steering gear mechanism, the pinion shaft 4 is deflected as a result of contact with the gear 2 to such an extent that sufficient twisting (torsion) of the torsion webs 20 is produced, whereby the resilient restoring torques which result from this torsion of the torsion webs 20 counteract the deflection of the pinion shaft 4 and consequently press it against the gear 2.

[0048] An axial position fixing of the inner bearing ring 10 of the rotary bearing 9 of the fixed bearing 6 on the pinion shaft 4 and the components which are arranged within the fixed bearing sleeve 14 is carried out with there being interposed a pressure piece 21 which is in abutment with the inner bearing ring 10 and which is screwed to a threaded portion 22 at the drive-side end of the pinion shaft 4.

[0049] The outer ring 19 of the pivot ring 15 is constructed in a pot-like manner and accordingly comprises a radially extending portion 23 and an axially extending tubular portion 24 with circular-ring-like cross-sections. The tubular portion 24 extends, in this instance from the side of the radially extending portion 23 of the outer ring 19 of the pivot ring 15, which side faces away from the rotary bearing 9. In the region of the tubular portion 24, the wall of the outer ring 19 of the pivot ring 15 forms two radially or diametrically opposing through-openings, in which a cylindrical bearing journal 25, 26 is received in a fixed manner. The bearing journals 25, 26 whose longitudinal axes 27 are orientated coaxially with respect to each other protrude in this instance over the outer side of the wall of the outer ring 19 of the pivot ring 15. The bearing journals 25, 26 protrude with these portions, into bearing receiving members 28, 29 of the housing 1 in order to ensure, on the one hand, a relatability of the bearing device 12 with respect to a rotation axis 30 which is orientated perpendicularly, on the one hand, to the longitudinal axis 31 of the outer ring 19 and, on the other hand, the pivot axis 7. On the other hand, these bearing journals 25, 26 are components of an adjustment device of the steering gear mechanism, by means of which the position of the outer ring 19 of the pivot ring 15 can be adjusted within the housing 1 with respect to the directions which correspond to this rotation axis 30.

[0050] The fixing of the bearing journals 25, 26 within the through-openings of the wall of the outer ring 19 of the pivot ring 15 is selected to be non-releasable and may in particular be carried out in a materially engaging manner, for example, by means of welding, soldering or adhesive bonding. Non-positive-locking (for example, by means of a press-fit) and positive-locking connection (for example, by means of a screw connection), then where applicable also releasable connection variants are also possible.

[0051] The adjustment device further comprises in addition to the two bearing journals 25, 26 a threaded element 32, which forms an outer thread which cooperates with an inner thread of a first (28) of the bearing receiving members of the housing 1. At the end face facing the outer side of the housing 1, the threaded element 32 forms a recess 33 which is hexagonal in cross-section and in which there can be inserted a corresponding tool (not illustrated) by means of which a torque can be transmitted to the threaded element 32, whereby the threaded element 32, as a result of a cooperation of the outer thread thereof with the inner thread (counter-thread) of the first bearing receiving member 28 can be moved along the longitudinal axis 27 of the first bearing receiving member 28 which extends coaxially relative to the longitudinal axes 27 of the bearing journals 25, 26. At the end face facing the inner side of the housing 1, the threaded element 32 also forms a recess which is cylindrical or circular in cross-section and in which an end portion of a first (25) of the bearing journals engages in a play-free manner to the greatest possible extent.

[0052] If the threaded element 32, when viewed from the outer side of the housing 1, is screwed further into the bearing receiving member 28, this movement of the threaded element 32 is transmitted to the first bearing journal 25 and from there to the outer ring 19 of the pivot ring 15 and to the second bearing journal 26 which in this instance is displaced in a longitudinally axial manner in the second bearing receiving member 29 of the housing 1 which is also constructed in a cylindrical manner and with an only slightly larger diameter in comparison with the diameter of the second bearing journal 26.

[0053] The displacement of the outer ring 19 and consequently of the pivot ring 15 brought about by such a screwing-in action of the threaded element 32 into the first bearing receiving member 28 leads as a result of the support of the pinion 3 on the gear 2 to a pivoting of the pinion shaft 4. This pivoting of the pinion shaft 4 and of the connected inner ring 16 of the pivot ring leads at the same time to an increasing torsion of the torsion webs 20 since the outer ring 19 of the pivot ring 15 cannot follow this pivot movement of the inner ring 16 since the bearing of the bearing pins 25, 26 in the bearing receiving members 28, 29 of the housing 1 does not permit such a pivot movement of the outer ring 19.

[0054] If, however, the threaded element 32 is unscrewed to a small extent from the first bearing receiving member 28, the resilient application of the pinion shaft 4 results in the outer ring 19 with the two bearing pins 25, 26 following the movement of the threaded element 32, whereby the torsion of the torsion webs 20 and consequently the resilient application of the pinion shaft 4 is reduced. Accordingly, as a result of a change of the position of the outer ring 19 of the pivot ring 15 within the housing 1 with respect to the directions mentioned, the resilient application of the pinion shaft 4 or the force with which the pinion shaft 4 is pressed against the gear 2 can be adjusted.

[0055] The bearing device 13 of the movable bearing 8 comprises a stop element in the form of a stop sleeve 35 which is arranged to be able to be moved within a receiving space 36 formed by the housing 1 in such a manner that, within the limits of a structurally defined basic play, the pivoting movability about the pivot axis 7 defined or formed by the fixed bearing 6 is possible. In this instance, this movability is limited in one direction by a contact which is complete or which occurs on two flanks of the individual teeth of the pinion 3 and gear 2 and which is brought about by the resilient loading by means of the twisted torsion webs 20 and, in the other direction, by a stop which is brought about by means of a contact of contact faces 37, 38 which are formed, on the one hand, by the stop sleeve 35 and, on the other hand, by the wall of the housing 1 which delimits the receiving space 36 (cf. FIG. 4).

[0056] Details relating to the structure and operation of the movable bearing 8 can be derived from the previously unpublished German patent application 10 2017 211 461.4.

[0057] The steering gear mechanism further comprises a connection element 39 which connects the fixed bearing sleeve 14 to a movable bearing sleeve 40 of the movable bearing 8 and to this end is constructed in an integral and materially uniform manner with the bearing sleeves 14, 40. As can be seen in FIGS. 1 and 2, the connection element 39 is constructed in a tubular manner with circular-ring-like or partially circular-ring-like cross-sections, wherein it has a covering opening 34 which is arranged in a central portion of the connection element 39 and which extends over a portion of the periphery thereof. As a result of this covering opening 34, a portion of the gear 2 may protrude into the inner space which is delimited by the connection element 39 and which receives the pinion shaft 4 in the portion which inter alia forms the pinion 3 in order to allow an engagement of the tooth arrangements of the gear 2 and the pinion 3.

[0058] The connection element 39 results, on the one hand, in the resilient restoring torques which result from the torsion of the torsion webs 20 of the pivot ring 15 of the fixed bearing 6 not being transmitted exclusively via the rotary bearing 9 of the fixed bearing 6 to the pinion shaft 4, which would be linked with a relatively high tilting loading of this rotary bearing 9. Instead, these resilient restoring torques are transmitted primarily via the fixed bearing sleeve 14 of the fixed bearing 6 and the integrally connected connection element 39 and via the movable bearing sleeve 40 to the rotary bearing 9 of the movable bearing 8. On the other hand, as a result of the connection element 37, a relative rotation between the fixed bearing sleeve 14 and the movable bearing sleeve 40 about the longitudinal axes 18 thereof is prevented.

[0059] The steering gear mechanism, as a result of the integration of the adjustment device into the fixed bearing 6, is advantageously suitable for carrying out a method according to the invention, whereby it is intended to be prepared for a subsequent use as part of a steering system of a motor vehicle.

[0060] To this end, the threaded element 32 of the adjustment device is first screwed to a relatively large extent into the first bearing receiving member 28 of the housing 1, which results in a correspondingly significant torsion of the torsion webs 20, which in turn leads to a correspondingly high (first) force, by means of which the pinion shaft 4 or the pinion 3 is pressed against the gear 2.

[0061] Subsequently, the pinion shaft 4 is rotatingly driven by means of a rotary drive which may be the steering motor which is provided as part of the steering system or a rotary drive (not illustrated) which is provided only for carrying out the method, firstly in a first of the two possible rotation directions and subsequently in the other of these rotation directions. This is carried out in each case at least until the gear 2 has carried out at least one complete revolution, where applicable a large number of revolutions. The correspondingly high surface pressure which is applied as a result of the relatively large first force in the tooth engagement between the pinion 3 and the gear 2 leads to a plastic deformation or the plastics material of the gear 2 which results in a globoid tooth arrangement of this gear 2. Tolerance-related deviations from the structurally provided tooth engagement are thereby compensated for and a settlement of the plastics material of the gear 2, which would otherwise only occur in the context of the operation of the steering gear mechanism as part of the steering system, is brought about.

[0062] Subsequently, the threaded element 32 is again unscrewed from the first bearing receiving member 28 of the housing 1 to such an extent and consequently the force with which the pinion shaft 4 or the pinion 3 is pressed against the gear 2 is reduced until (when a second value for this force is reached) for the individual steering gear mechanism the most optimum possible compromise between, on the one hand, a sufficiently large resilient application of the pinion shaft 4 and, on the other hand, a not excessively high friction in the tooth engagement is achieved. The sufficiently large resilient application ensures only a low generation of noise during operation of the steering gear mechanism, whilst, as a result of the relatively low friction in the tooth engagement, an advantageous steering sensation and a relatively low wear of the sets of teeth of the pinion 3 and gear 2 over the intended service-life of the steering gear mechanism is achieved. The steering gear mechanism can then advantageously be used with this adjustment of the threaded element 32 as a part of a steering system of a motor vehicle.

LIST OF REFERENCE NUMERALS

[0063] 1 Housing

[0064] 2 Gear

[0065] 3 (Helical) pinion

[0066] 4 (Helical) pinion shaft

[0067] 5 Output shaft

[0068] 6 Fixed bearing

[0069] 7 Pivot axis

[0070] 8 Movable bearing,

[0071] 9 Rotary bearing

[0072] 10 Inner bearing ring of a rotary bearing

[0073] 11 Outer bearing ring of a rotary bearing

[0074] 12 Bearing device of the fixed bearing

[0075] 13 Bearing device of the movable bearing

[0076] 14 Fixed bearing sleeve

[0077] 15 Pivot ring

[0078] 16 Inner ring of the pivot ring

[0079] 17 Annular disk

[0080] 18 Longitudinal axes of the fixed bearing sleeve/movable bearing sleeve/pinion shaft

[0081] 19 Outer ring of the pivot ring

[0082] 20 Torsion web

[0083] 21 Pressure piece

[0084] 22 Threaded portion of the pinion shaft

[0085] 23 Radially extending portion of the outer ring

[0086] 24 Axially extending portion of the outer ring

[0087] 25 First bearing journal

[0088] 26 Second bearing journal

[0089] 27 Longitudinal axis of a bearing journal/a bearing receiving member

[0090] 28 First bearing receiving member of the housing

[0091] 29 Second bearing receiving member of the housing

[0092] 30 Rotation axis

[0093] 31 Longitudinal axis of the outer ring

[0094] 32 Threaded element

[0095] 33 Recess of the threaded element

[0096] 34 Covering opening of the connection element

[0097] 35 Stop sleeve

[0098] 36 Receiving space of the housing

[0099] 37 Contact face of the stop sleeve

[0100] 38 Contact face of the housing

[0101] 39 Connection element

[0102] 40 Movable bearing sleeve