RACK-AND-PINION GEAR FOR A MOTOR VEHICLE

Abstract

A rack-and-pinion steering gear for a motor vehicle allows adjustment of an inclination angle between the rack and pinion at the point of contact therebetween to reduce noise. A yoke is spring-biased against the rack to urge rack into engagement with the pinion. The yoke is supported in a bushing which can be adjusted within and relative to a housing such that the yoke moves in a plane parallel to a longitudinal axis of the rack and to a longitudinal axis of the pinion shaft. The yoke engages the rack to permit steering-type movement of the rack relative to the yoke along the rack longitudinal axis, but movement of the yoke parallel to the pinion shaft longitudinal axis forces the portion of the rack contacting the yoke to move along with the yoke, thereby adjusting the inclination angle between the rack and the pinion.

Claims

1. A rack-and-pinion steering gear, comprising: a pinion shaft having a toothed pinion adjacent an end thereof; a rack supported inside a housing and having a toothed surface engaging the pinion; a cylindrical yoke biased along a pressure axis to press against the rack at a location opposite the pinion and urge the rack into toothed engagement with the pinion, engagement between the yoke and the rack a) allowing movement of the rack relative to the yoke along the rack longitudinal axis during steering and b) restraining against movement of the rack relative to the yoke in an adjustment direction parallel with a pinion shaft longitudinal axis; and a bushing having a circular outer surface and an eccentrically-positioned inner contour receiving the yoke therein, the bushing retained in the housing and rotatable relative thereto to displace the yoke in a direction having a component in the adjustment direction.

2. The rack-and-pinion steering gear of claim 1, further comprising a coil spring biasing the yoke against the rack.

3. The rack-and-pinion steering gear of claim 1, wherein the bushing is lockable against rotation with respect to the housing.

4. The rack-and-pinion steering gear of claim 1, wherein: a surface of the rack against which the yoke presses is cylindrical, and a face of the yoke pressing against the rack has a concave cylindrical shape conforming to the rack.

5. A rack-and-pinion gear, comprising: a cylindrical yoke biased along a pressure axis to urge a rack against a pinion; and a component having a circular circumference and an eccentrically-positioned inner contour receiving the yoke therein, and rotatable within a rack housing to displace the yoke in a plane perpendicular to the pressure axis and thereby move a yoke-contacting portion of the rack parallel to a longitudinal axis of the pinion.

6. The rack-and-pinion gear of claim 5, further comprising a coil spring biasing the yoke against the rack.

7. The rack-and-pinion gear of claim 5, wherein the component is lockable against rotation with respect to the rack housing.

8. The rack-and-pinion steering gear of claim 5, wherein: a guide face of the yoke pressing against the rack has a concave cylindrical shape conforming to a cylindrical surface of the yoke-contacting portion of the rack.

9. A rack-and-pinion gear, comprising: a yoke biased along a pressure axis against a portion of the rack to urge the rack into toothed engagement with a pinion, and movable perpendicular to the pressure axis to force the portion along an adjustment axis parallel with a longitudinal axis of a pinion shaft; and a component movable within a rack housing to displace the yoke in a direction having a component along the adjustment axis.

10. The rack-and-pinion gear of claim 9, further comprising a coil spring biasing the yoke against the rack.

11. The rack-and-pinion gear of claim 9, wherein: the yoke is cylindrical; and the component has a circular outer surface and an eccentrically-positioned inner contour receiving the yoke therein, the component retained within the housing and rotatable relative thereto to displace the yoke.

12. The rack-and-pinion steering gear of claim 11, wherein: a guide face of the yoke pressing against the rack has a concave cylindrical shape conforming to a cylindrical surface of the rack against which the guide face presses.

13. The rack-and-pinion gear of claim 11, wherein the component can be locked against rotation with respect to the housing.

14. The rack-and-pinion gear of claim 9, wherein the component is linearly adjustable relative to the housing.

Description

BRIEF DESCRIPTION OF THE DRAWINGS

[0028] FIG. 1 is a perspective illustration of a steering gear according to a first disclosed embodiment;

[0029] FIG. 2 is a sectioned illustration of the steering gear of FIG. 1;

[0030] FIG. 3 is a sectioned illustration along the line 3-3 in FIG. 2;

[0031] FIG. 4 is a sectioned illustration of a steering gear according to a second disclosed embodiment; and

[0032] FIG. 5 is a sectioned illustration along the line 5-5 in FIG. 4.

DETAILED DESCRIPTION

[0033] As required, detailed embodiments of the present invention are disclosed herein; however, it is to be understood that the disclosed embodiments are merely exemplary of the invention that may be embodied in various and alternative forms. The figures are not necessarily to scale; some features may be exaggerated or minimized to show details of particular components. Therefore, specific structural and functional details disclosed herein are not to be interpreted as limiting, but merely as a representative basis for teaching one skilled in the art to variously employ the present invention.

[0034] In the different Figures, identical components are always given the same reference numerals, for which reason they are generally also only described once.

[0035] FIGS. 1-3 show a first embodiment of a rack-and-pinion steering gear 1 for a passenger vehicle, wherein FIG. 1 is a perspective illustration of the entire steering gear 1. This comprises a pinion shaft 10 with a toothed pinion 11 adjacent its lower end which cooperates with teeth 31 formed along the length of a rack 30. In the Figures, the X-, Y- and Z-axes of the vehicle (in accordance with the commonly accepted convention in the automotive industry) are drawn in accordance with the provided installation position of the steering gear 1. A longitudinal axis A of the rack 30 is parallel with the Y-axis and consequently horizontal, whilst an axial direction B of the pinion shaft 10 (at least approximately) can extend within the X-Z plane or also at an angle to all three axes. Both the pinion shaft 10 and the rack 30 are supported inside a housing 40. In this instance, the rack 30 is linearly displaceable in the direction of the Y-axis, and the pinion shaft 10 is rotatable about its longitudinal axis B.

[0036] The rotatable support of the pinion shaft 10 is produced by means of three bearings 12, 13, 14 or roller bearings which are received in a stationary manner inside the housing 40. Spacing along the rack 30 from the pinion shaft 10 is a servo subassembly 50 which cooperates with the rack 30. The structure and function of the servo subassembly 50 are not significant to the present invention and are thus not explained in greater detail. However, in the region of the servo subassembly 50, there is formed a bearing location 51 for the rack 30 on which it is supported with respect to the housing 40.

[0037] In order to improve the engagement between the rack teeth 31 and the pinion 11, the rack 30 is subjected to pressure by a pressure element or yoke 43 to urge or force the rack toward the pinion shaft 10. The yoke 43 has a cylindrical lateral surface and a guide face 43.1 on the end which contacts and applies pressure to the rack 30. In the depicted embodiment, the guide face 43.1 is concave as viewed along the rack longitudinal axis A as shown in FIG. 2, and circular as viewed along the pressure direction D, so that it conforms to the cylindrical surface of the rack at the area of contact between the two components. The guide face therefore has a concave cylindrical surface, defined herein for purposes of description as the surface formed when a concave arc is projected along a line perpendicular to the axis of a cylinder.

[0038] The relative configurations of the guide face 43.1 and the surface of the rack 30 contacted thereby create a partial positive-locking connection to the rack 30: The contact or engagement between the yoke 43 and the rack 30 permits the rack to move freely along the longitudinal axis A relative to the yoke (which occurs during normal steering activity), whilst it securely restrains the rack against displacements relative to the yoke in directions transverse to the rack axis A. In the embodiment shown in FIG. 2, the restraining or locking effect in the direction parallel with the pinion shaft axis B (and perpendicular to axes D and B in FIG. 2) is provided by the fact that the guide face 43.1 extends around the cylindrical lateral surface of the rack, as seen in FIG. 2.

[0039] In spite of the urging of the rack against the pinion, a potential problem involves the engagement between the respective teeth of pinion shaft 10 and rack 30 not being optimum, which may, for example, lead to undesirable rattling noises (NVH). Whether these noises occur is at least in part dependent on the inclination of the pinion shaft 10 inside the housing 40 and with relative to the rack 30. In this instance, small changes of the inclination angle can influence the toothed engagement in a decisive manner.

[0040] In order to prevent the housing 40 from having to be manufactured with a relatively high degree of precision (small dimensional manufacturing tolerances), the position of the yoke 43 can be adjusted so as change the inclination angle. More specifically, a position of the yoke 43 parallel to the pinion shaft axis B can be adjusted. To this end, the yoke 43 is supported inside a bushing 45 which has a circular outer circumference 45.1 and a circular inner contour or hole 45.2 which is positioned eccentrically (non-concentrically) relative thereto. As a result of the circular outer circumference 45.1, the bushing 45 can (during manufacture and/or servicing of the steering gear) be rotated within the housing 40 to assume any angular position around the yoke 43. This rotation of the bushing 45 is shown in FIG. 3 by adjustment movement E, indicated by the double-headed, curved arrow. Depending on this rotational/angular adjustment of the bushing, the inner contour/hole 45.2 and consequently the yoke 43 received therein are displaced in a circular manner about the axis of rotation of the bushing 45, which (in the depicted construction) is coaxial with the pressure axis D. Because of the configuration of the engagement between the yoke guide face 43.1 and the surface of the rack 30 (described above), this circular displacement of the yoke 43 within the housing 40 forces the portion of the rack that is contacted by the guide face to move, along with the yoke, in a direction parallel to the pinion longitudinal axis B.

[0041] The adjustment operation thus results in a bending or deflection of the rack 30 (of relatively small magnitude) about a support point collocated with the bearing 51, with the bending angle being determined by the magnitude of movement of the yoke 43 along or parallel to the pinion shaft axis B. This bending directly results in a change in the inclination angle of the rack 30 relative to the pinion 11. In the depicted embodiment, any movements of the yoke 43 relative to the housing 40 in the pressure direction D are decoupled from the bushing 45. The yoke 43 can be displaceably arranged in the pressure direction D in the bushing 45, more specifically in a through-opening 45.3 thereof

[0042] The rotational adjustment E of the bushing 45 brings about a circular movement of the yoke in the plane of the section shown in FIG. 3, and therefore also causes a displacement of the yoke 43 which has a component along the longitudinal axis A of the rack. This A-axis movement does not contribute to changing the inclination of the rack 30, and does not apply any force to the rack since the rack is able to move freely relative to the yolk 42 along (parallel to) the A-axis.

[0043] Under some circumstances, friction between the bushing 45 and the housing 40 may be sufficient to prevent an undesirable rotation of the bushing during operation of the vehicle. If this is not the case, the bushing may be locked with respect to the housing 40 by means of a locking screw 16 after the optimal angular position has been achieved. To facilitate the adjustment of the angular position, the bushing 45 may have at the end side structures for the positive-locking engagement with a tool, for example, an internal hexagon socket or the like.

[0044] Whilst the bushing outer circumference 45.1 may be constructed to be smooth, there may alternatively be formed at that location an outer thread which cooperates with a corresponding inner thread on the housing 40. In this instance, under some circumstances it is possible to dispense with the locking screw 16 and if necessary a fluid screw securing can be used.

[0045] FIGS. 4 and 5 show a second embodiment of a steering gear 1 according to the invention which substantially corresponds to the embodiment shown in FIGS. 1 to 3 and thus will not be explained again. In place of the eccentric bushing 45, the steering gear 1 has a bearing component 46 to support the yoke 43. In a through-opening 46.1 of the bearing component 46, the yoke 43 is displaceably supported in the pressure direction D. The bearing component 46 can be adjusted in a linear manner inside a bearing channel 40.1 of the housing 40, wherein the double-headed arrow E in FIG. 5 indicates the direction of adjustment movement. In this depicted embodiment, the friction forces between the bearing component 46 and the housing 40 may not be sufficient to reliably prevent an undesirable displacement of the bearing component during operation of the vehicle. For this reason, there must generally be provided a locking screw 17 which can be seen in FIG. 5 and by means of which the bearing component 46 is locked after an optimum inclination of the rack 30 has been adjusted.

[0046] In this FIGS. 4-5 embodiment, the adjustment of the yoke 43 relative to the rack 30 and housing 40 is always made purely parallel with the axis B of the pinion shaft. This is advantageous in so far as the connection between an adjustment path and the change of the inclination of the rack 30 which is thereby brought about is approximately linear. This is in contrast to the embodiment of FIGS. 2 and 3, where an adjustment of the position of the yoke 43 perpendicularly to the axial direction A of the rack 30 [parallel with the pinion shaft axis B] is necessarily accompanied by an adjustment parallel with the axial direction A.

[0047] While exemplary embodiments are described above, it is not intended that these embodiments describe all possible forms of the invention. Rather, the words used in the specification are words of description rather than limitation, and it is understood that various changes may be made without departing from the spirit and scope of the invention. Additionally, the features of various implementing embodiments may be combined to form further embodiments of the invention.