RACK-AND-PINION GEAR, STEERING GEAR AND STEERING SYSTEM

Abstract

A rack-and-pinion gear is described, which is suitable in particular for a steering system of a motor vehicle. In this a pinion is supported in a pinion housing and meshes with a rack inside this pinion housing. The rack here projects from the pinion housing through at least one housing aperture. A stop ring, which serves to limit a rack longitudinal movement and/or a tilting of the rack, is moreover held in the housing aperture by means of a press fit. In addition, a steering gear having such a rack-and-pinion gear and a steering system for a motor vehicle comprising such a steering gear are described.

Claims

1. A rack-and-pinion gear, in particular for a steering system of a motor vehicle, having a rack and a pinion, wherein the pinion is supported in a pinion housing and meshes with the rack inside the pinion housing, and wherein the rack projects from the pinion housing through at least one housing aperture, and wherein a stop ring, which is held in the pinion housing by means of a press fit, is provided in the housing aperture for limiting a rack longitudinal movement and/or a tilting of the rack.

2. The rack-and-pinion gear as defined in claim 1, characterized in that an inner circumferential surface of the stop ring comprises a first stop face for limiting the tilting of the rack.

3. The rack-and-pinion gear as defined in claim 2, characterized in that a lateral face of the stop ring remote from the pinion comprises a second stop face for limiting the rack longitudinal movement.

4. The rack-and-pinion gear as defined in claim 3 wherein the stop ring is produced from a plastic material, in particular from polyamide.

5. The rack-and-pinion gear as defined in claim 4 wherein the housing aperture is of substantially cylindrical formation and the press fit exists between an outer circumferential surface of the stop ring and a generated surface of the housing aperture.

6. The rack-and-pinion gear as defined in claim 5 wherein the pinion housing is produced by means of a casting process and is unmachined, particularly in the area of the press fit.

7. The rack-and-pinion gear as defined in claim 6 wherein the stop ring comprises a fully or partially circumferential fixing bead on its outer circumferential surface.

8. The rack-and-pinion gear as defined in claim 7 wherein the pinion housing comprises a seating surface, on which a lateral face of the stop ring facing the pinion bears, in particular wherein the seating surface is an integral part of a seating shoulder of the pinion housing.

9. The rack-and-pinion gear as defined in claim 8 wherein the stop ring comprises at least one cavity, which is positioned between an outer circumferential surface and an inner circumferential surface of the stop ring, in particular wherein a depth direction of the cavity runs parallel to a ring central axis.

Description

BRIEF DESCRIPTION OF THE DRAWINGS

[0029] The present disclosure is explained below with reference to two exemplary embodiments, which are shown in the drawings attached, which show:

[0030] FIG. 1 a steering system according to the present disclosure having a steering gear according to the present disclosure, which comprises a rack-and-pinion gear according to the present disclosure,

[0031] FIG. 2 the rack-and-pinion gear in FIG. 1 in a sectional representation,

[0032] FIG. 3 a perspective view of a stop ring of the rack-and-pinion gear in FIG. 2 according to an embodiment slightly modified compared to the variant in FIG. 2 and

[0033] FIG. 4 a further perspective view of the stop ring in FIG. 3.

DETAILED DESCRIPTION

[0034] FIG. 1 shows a steering system 10 for a motor vehicle, which is designed as electrically driven power steering.

[0035] It comprises an electric motor 12, by means of which a steering torque, introduced by a driver via a steering wheel 14, can be assisted or supplemented in such a way that an additional steering force can be exerted on the steered wheels by means of the electric motor 12.

[0036] The steering system 10 here comprises two steering gears, wherein a first steering gear 16 serves to transmit a steering torque introduced via the steering wheel 14 to the steered wheels.

[0037] A second steering gear 18 serves to transmit the torque generated by the electric motor 12 to the steered wheels.

[0038] Both steering gears are designed as rack-and-pinion gears, wherein, however, the respectively associated racks are firmly connected to one another, or only a single rack for is used for both steering gears 16, 18.

[0039] Such steering systems are also referred to as dual-pinion steering, since the common rack or the common rack union interacts with two pinions.

[0040] FIG. 2 shows a rack-and-pinion gear 20, which may be both an integral part of the first steering gear 16 and an integral part of the second steering gear 18.

[0041] It comprises a rack 22, which meshes with a pinion 24. Here both the rack 22 and the pinion 24 are supported in a so-called pinion housing 26.

[0042] In order to ensure a reliable interaction of the rack 22 and the pinion 24, the rack is subjected by means of a yoke 28 to a force in the direction of the pinion 24.

[0043] That area in which the rack 22 meshes with the pinion 24 is situated inside the pinion housing 26.

[0044] Here however, the rack 22 does not lie entirely inside the pinion housing 26, but projects from the housing through a housing aperture 30.

[0045] In order to limit both a rack longitudinal movement, which occurs substantially in a direction illustrated by means of an arrow 32, and a tilting of the rack, which is symbolized by means of an arrow 34, a stop ring 36 is provided in the housing aperture 30.

[0046] In this context the tilting of the rack may also be referred to as rack distortion. The two terms are to be interpreted synonymously.

[0047] The stop ring 36 is held in the pinion housing 26 by means of a press fit 37.

[0048] In the embodiment represented the housing aperture 30 here is of a substantially circular cylindrical design. The press fit 37 therefore exists between an outer circumferential surface 38 of the stop ring 36 and a generated surface 40 the housing aperture 30.

[0049] The stop ring furthermore bears, with a lateral face 42 facing the pinion 24, on a seating surface 44 of the pinion housing 26.

[0050] The seating surface 44 here is formed as a lateral face of a seating shoulder 46.

[0051] Relative to a ring central axis A-A (see FIG. 3 and FIG. 4), the stop ring 36 is therefore positioned in an axial direction in the pinion housing 26 by way of the seating shoulder 46, and the press fit 37 is formed on the circumference of the stop ring 36.

[0052] In order to limit the tilting of the rack, an inner circumferential surface 48 of the stop ring 36 comprises a first stop face. In the embodiment represented the entire inner circumferential surface 48 is formed as first stop face.

[0053] If the rack 22 is therefore tilted in the direction symbolized by the arrow 34, it strikes against the inner circumferential surface 48, thereby restricting a movement of this nature.

[0054] The rack longitudinal movement in the direction indicated by the arrow 32 is limited by means of a lateral face 50 of the stop ring 36 remote from the pinion 24. This lateral face 50 comprises a second stop face. In the embodiment represented the lateral face 50 is formed in its entirety as second stop face. This interacts with a counter-stop face 52 of the rack 22 to limit the rack longitudinal movement.

[0055] The stop ring 36 here is produced from a plastic material, a glass fiber-reinforced polyamide being used in the embodiment represented.

[0056] An injection molding process is used as the method of manufacture.

[0057] The stop ring 36 is not of solid design but comprises cavities 54, which are positioned between the outer circumferential surface 38 and the inner circumferential surface 48.

[0058] In this way substantially the same thickness may be selected for all wall thicknesses of the stop ring 36, which counteracts the formation of pores and inclusions in the course of the injection molding process.

[0059] A depth direction of the cavities 54 runs in the direction of the ring central axis A-A.

[0060] In the embodiment of the stop ring 36 according to FIG. 2 the cavities 54 are axially uninterrupted, forming, as it were, through-holes.

[0061] By contrast, the stop ring 36 according to FIGS. 3 and 4 is slightly modified. Here the cavities 54 are no longer axially uninterrupted. They are formed as blind holes.

[0062] In both variants represented the stop ring 36 comprises a fully circumferential fixing bead 56 on its outer circumferential surface 38.

[0063] This serves to secure the stop ring 36 in the housing aperture 30 and is deformed when pressing the stop ring 36 in.

[0064] The pinion housing 26 is produced by means of a casting process. Here it is unmachined in the area of the press fit 37. This means that after casting of the pinion housing 26 no further machining of any kind, in particular no metal cutting, is performed in the area of the press fit 37.

[0065] By virtue of the geometry and of the material selected for the stop ring 36, however, this can nevertheless be reliably held in the housing aperture 30.

[0066] The rack-and-pinion gear 20 is therefore produced as follows:

[0067] First the pinion housing is cast, for example from diecast aluminum.

[0068] The stop ring 36 is furthermore produced in an injection molding process.

[0069] The stop ring 36 is then pushed or pressed along its ring central axis A-A into the housing aperture 30, until its lateral face 42 bears on the seating shoulder 46. In so doing the fixing bead 56 is deformed.

[0070] No machining of the housing aperture 30 is performed after casting.