Steering Gear and Method for Mounting a Steering Gear for a Motor Vehicle

Abstract

In a steering gear for a motor vehicle, a bush is pressed into a concentric opening in the worm gear, wherein the steering pinion is inserted into the bush, and wherein the bush is designed to transmit a torque acting from the worm gear onto the bush onto the steering pinion. The disclosure further relates to a method for mounting a steering gear for a motor vehicle.

Claims

1. A steering gear for a motor vehicle comprising: a steering gear housing; and a steering pinion configured to couple to a steering shaft, which is inserted into the steering gear housing and meshes with a rack; and a servo drive configured to provide a steering assist force on the steering pinion, wherein the servo drive has a worm driven by an electric motor and a worm gear which meshes with the worm, wherein a bush is pressed into a concentric opening in the worm gear, wherein the steering pinion is inserted into the bush, and wherein the bush is configured to transmit a torque from the worm gear acting on the bush onto the steering pinion.

2. The steering gear as claimed in claim 1, characterized in that wherein: the steering pinion has a first axial end section configured to connect to the steering shaft, and a second axial end section, at which the bush is secured to the steering pinion, a first spline is formed in at least some sections on an outer circumference of the steering pinion, and a second spline is formed on an inner circumference of the bush, the second spline meshing with the first spline to transmit torque between bush and steering pinion.

3. The steering gear as claimed in claim 2, wherein the bush is configured to bridge a difference in diameter between the worm gear and the steering pinion, and the first spline is configured to transmit the torque between the bush and the steering pinion without play.

4. The steering gear as claimed in claim 2, wherein: the first spline is formed with a longitudinal convexity so as to produce a freedom of play between the second spline and the first spline, the second spline and the first spline have an interference fit, and the first spline has, in axial end sections, a predefined angle of inclination with respect to a radial axis of the steering pinion.

5. The steering gear as claimed in claim 1, wherein: the bush has an outer surface with a first seat configured to receive a slipping clutch and a second seat configured to receive an inner circumference of the concentric opening of the worm gear, the first seat has a first diameter and the second seat has a second diameter, the first diameter being smaller than the second diameter, the second seat extends from a radial projection formed in a first axial end section of the bush as far as to a second axial end section of the bush, and the first seat is formed within the second seat in an axial direction of the bush.

6. The steering gear as claimed in claim 5, wherein the radial projection of the bush is arranged adjacent to a fixed bearing inserted into the steering gear housing, the radial projection of the bush forming a planar stop for the worm gear pressed onto the bush.

7. The steering gear as claimed in claim 5, wherein, the slipping clutch pressed into the first seat of the bush is provided to form an overload safety device of the worm gear between the worm gear and the bush, the slipping clutch being formed by a tolerance ring.

8. The steering gear as claimed in claim 2, wherein: the worm gear is positioned relative to the steering pinion by first and second centering sections formed on the steering pinion, the first centering section is arranged in front of the first spline in an axial direction of the steering pinion and the second centering section is arranged behind the first spline in the axial direction, and the first centering section and the second centering section have the same diameter.

9. The steering gear as claimed in claim 8, wherein: a thread, onto which a securing nut is screwed, is formed on the second axial end section of the steering pinion, the bush is formed as a spacer between the securing nut and the fixed bearing to secure the fixed bearing axially on the steering pinion, the bush is configured to transmit an axial force that is produced during movement of the steering pinion from the fixed bearing onto the securing nut, and the thread arranged on the second axial end section of the steering pinion is configured to absorb tangential and axial forces of the bush.

10. The steering gear as claimed in claim 2, wherein: a bearing seat of the steering pinion has a larger diameter than a tooth tip circle of the first spline of the steering pinion, and wherein a tooth tip circle diameter formed in the region of the rack is larger than the bearing seat of the steering pinion.

11. A method for assembling a steering gear for a motor vehicle, comprising: assembling a preassembled subgroup by pressing a worm gear with an inner circumference onto an outer circumference of a bush; pressing a fixed bearing for supporting a steering pinion into a steering gear housing; drawing the steering pinion into the steering gear housing with a pulling device secured to an axial end section of the steering pinion; bringing toothing formed on an outer circumference of the worm gear into engagement with a worm coupled to a servo drive; and pressing the pre-assembled subgroup on an inner circumference of the bush onto the steering pinion drawn into the steering gear housing.

12. The steering gear as claimed in claim 10, wherein a root tip diameter of further toothing of the steering pinion is larger than the bearing seat of the steering pinion

Description

BRIEF DESCRIPTION OF THE DRAWINGS

[0027] The appended drawings are intended to provide further understanding of the embodiments of the invention. They illustrate embodiments and, in conjunction with the description, serve to explain the principles and concepts of the invention.

[0028] Other embodiments and many of the advantages mentioned can be gathered in a view of the drawings. The illustrated elements of the drawings are not necessarily shown true to scale in relation to one another.

[0029] FIG. 1 shows a cross-sectional view of a steering gear for a motor vehicle according to a preferred embodiment of the invention;

[0030] FIG. 2 shows a schematic illustration of a steering pinion according to the preferred embodiment of the invention;

[0031] FIG. 3 shows a schematic illustration of a bush according to the preferred embodiment of the invention; and

[0032] FIG. 4 shows a flowchart of a method for assembling a steering gear for a motor vehicle according to the preferred embodiment of the invention.

[0033] In the figures of the drawings, the same designations designate identical or functionally identical elements, parts or components, if nothing to the contrary is indicated.

[0034] FIG. 1 shows a cross sectional view of a steering gear for a motor vehicle according to a preferred embodiment of the invention.

[0035] The steering gear 1 of the motor vehicle has a steering gear housing 10 and a steering pinion 14 that can be coupled to the steering shaft 12. The steering pinion 14 is inserted into the steering gear housing 10 and meshes with a rack 16.

[0036] The steering gear 1 further has a servo drive 18 for providing a steering assist force on the steering pinion 14. The servo drive 18 has a worm 22 driven by an electric motor 20 and a worm gear 24. The worm gear 24 meshes with the worm 22. Furthermore, the steering gear 1 has a bush 26. The bush 26 is pressed into a concentric opening 24a of the worm gear 24 in the region of an outer circumference of the bush 26. The steering pinion 14 is also inserted into the bush 26. The bush 26 is also designed to transmit a torque M from the worm gear 24 acting on the bush 26 onto the steering pinion 14.

[0037] The steering pinion 14 has a first axial end section 14a and a second axial end section 14b. The first axial end section 14a can be connected to the steering shaft 12. In the second axial end section 14b, the bush 26 is secured to the steering pinion 14. A spline 14d is formed in some sections on the outer circumference 14c of the steering pinion 14. A spline 26b is likewise formed on an inner circumference 26a of the bush 26. The spline 26b meshes with the spline 14d of the steering pinion 14 to transmit torque between bush 26 and steering pinion 14.

[0038] The bush 26 is further designed to bridge a difference in diameter between the worm gear 24 and the steering pinion 14, wherein the spline 14d of the steering pinion 14 is designed to transmit a torque between bush 26 and steering pinion 14 without play.

[0039] A radial projection 30 of the bush 26 is arranged adjacent to a fixed bearing 32 inserted into the steering gear housing 10. As a result, the radial projection 30 of the bush 26 forms a planar stop 34 for the worm gear 24 pressed onto the bush.

[0040] Between the worm gear 24 and the bush 26, a slipping clutch 28 pressed into the first seat 26d of the bush 26 is provided to form an overload safety device of the steering pinion 14. The slipping clutch 28 is preferably formed by a tolerance ring. Alternatively, the slipping clutch can be arranged in another suitable way by appropriately shaped metal plates.

[0041] A thread 35, onto which a securing nut 36 is screwed, is formed on the second axial end section 14b of the steering pinion 14. The bush is thus formed as a spacer between the securing nut 36 and the fixed bearing 32 to secure the fixed bearing 32 axially on the pinion 14. Furthermore, the bush 26 is designed to transfer an axial force of the fixed bearing 32, produced during movement of the steering pinion, onto the securing nut 36, and wherein the thread 35 arranged on the second axial end section 14b of the steering pinion 14 is designed to absorb tangential and axial forces of the bush 26.

[0042] A bearing seat 14i of the steering pinion 14 preferably has a larger diameter D3 than a tooth tip circle D6 of the spline 14d of the steering pinion 14. A tooth tip circle diameter D4, preferably likewise a root circle diameter D5, of further toothing 14j of the steering pinion 14, formed in the region of the rack 16, is preferably larger than the bearing seat 14i of the steering pinion 14.

[0043] FIG. 2 shows a schematic illustration of a steering pinion according to the preferred embodiment of the invention.

[0044] Freedom of play between the spline of the bush and the spline 14d of the steering pinion 14 can advantageously be provided by forming the spine 14d of the steering pinion 14 with a longitudinal convexity. The spline of the bush and the spline 14d of the steering pinion 14 advantageously have an interference fit. The spline 14d of the steering pinion 14 also has a predefined angle of inclination with respect to a radial axis R of the steering pinion 14 in one of the axial end sections 14e, 14f.

[0045] The worm gear (not illustrated in FIG. 2) can thus be positioned relative to the steering pinion 14 by centering sections 14g, 14h formed on the steering pinion 14. A first centering section 14g is provided in front of the spline 14d in the axial direction A of the steering pinion 14, and a second centering section 14h is arranged behind the spline 14d in the axial direction A of the steering pinion 14. In addition, the first centering section 14g and the second centering section 14h have the same diameter.

[0046] FIG. 3 shows a schematic illustration of a bush according to a preferred embodiment of the invention.

[0047] The bush 26 has on an outer surface 26c a first seat 26d to receive a slipping clutch (not shown in FIG. 3) and a second seat 26e to receive an inner circumference of the concentric opening of the worm gear (not shown in FIG. 3).

[0048] The first seat 26d has a first diameter D1, and the second seat 26e has a second diameter D2. The first diameter D1 is preferably smaller than the second diameter D2, wherein the second seat 26e extends from a radial projection formed on a first axial end section 26f of the bush 26 as far as a second axial end section 26g of the bush 26. In addition, the first seat 26d is formed within the second seat 26e in the axial direction A of the bush 26.

[0049] FIG. 4 shows a flowchart of a method for assembling a steering gear for a motor vehicle according to the preferred embodiment of the invention.

[0050] The method for assembling a steering gear for a motor vehicle comprises assembling S1 a preassembled subgroup by providing a worm gear and a bush, wherein the worm gear is pressed with an inner circumference onto an outer circumference of the bush.

[0051] The method further comprises pressing S2 a fixed bearing for supporting a steering pinion into a steering gear housing.

[0052] The method further comprises drawing S3 the steering pinion into the steering gear housing by means of a pulling device secured to an axial end section of the steering pinion.

[0053] The method moreover comprises bringing S4 toothing formed on an outer circumference of the worm gear into engagement with a worm coupled to a servo drive.

[0054] The method additionally comprises pressing S5 the pre-assembled subgroup on an inner circumference of the bush onto the steering pinion drawn into the steering gear housing.

[0055] Although the present invention has been described above by using preferred embodiments, it is not restricted thereto but rather can be modified in many ways. In particular, the invention can be changed or modified in multifarious ways without departing from the core of the invention.

[0056] For example, a shape, dimension and/or a nature of the components of the steering gear for the motor vehicle can be changed.