Steering systems for a vehicle

Abstract

A steering system for a vehicle includes a pinion shaft which is mounted rotatably in a locating bearing and in a floating bearing, wherein both the locating bearing and the floating bearing are received in the steering housing.

Claims

1. A steering system for a vehicle comprising: a pinion shaft which is in engagement with a toothed rack and which is rotatably supported in a fixed bearing and in a floating bearing; and an electric servo motor configured to produce a supporting servo torque and to drive the pinion shaft, wherein both the fixed bearing and the floating bearing of the pinion shaft are received in a common steering housing which is constructed in one piece, wherein the fixed bearing includes an inner ring that is axially supported at an end side by a hub, which is positioned on the pinion shaft and which carries a worm wheel.

2. The steering system as claimed in claim 1, wherein a screw is arranged in the common steering housing, the screw configured to be driven by the servo motor and meshing with the worm wheel.

3. The steering system as claimed in claim 2, wherein a servo housing of the servo motor is connected to the steering housing in a transition between a motor shaft of the servo motor and the screw.

4. The steering system as claimed in claim 1, wherein the fixed bearing is arranged at a first side of the pinion shaft facing toward the worm wheel and the floating bearing is arranged at a second side of the pinion shaft facing away from the worm wheel.

5. The steering system as claimed in claim 1, wherein the inner ring of the fixed bearing is axially supported at an opposite end side on a shaft projection of the pinion shaft.

6. The steering system as claimed in claim 1, wherein the fixed bearing includes an outer ring having two end sides, the outer ring being axially supported at the two end sides directly or indirectly on the steering housing.

7. The steering system as claimed in claim 6, wherein a first end side of the two end sides of the outer ring is supported on a securing ring that is inserted into an inner groove on the steering housing.

8. The steering system as claimed in claim 1, wherein the pinion shaft has a pinion shaft end side, and the steering housing is constructed so as to be open adjacent to the pinion shaft end side and in axial extension of the pinion shaft.

9. A method for assembling a steering system for a vehicle, the method comprising: inserting a floating bearing into a common steering housing that is constructed in one piece; pushing a fixed bearing onto a pinion shaft; after pushing the fixed bearing and inserting the floating bearing, inserting the pinion shaft into the common steering housing such that both the fixed bearing and the floating bearing are received in the common steering housing; after inserting the pinion shaft, inserting a securing ring to fix the fixed bearing; and fitting a hub with a worm wheel onto the pinion shaft such that the hub axially supports an inner ring of the fixed bearing at an end side, wherein the pinion shaft is configured to be driven by an electric servo motor that is configured to produce a supporting servo torque.

10. The method of claim 9, wherein pushing the fixed bearing onto the pinion shaft comprises: pushing an inner ring of the fixed bearing against a shaft projection of the pinion shaft.

Description

BRIEF DESCRIPTION OF THE DRAWINGS

(1) Other advantages and advantageous embodiments can be derived from the additional claims, the description of the Figures and the drawings, in which:

(2) FIG. 1 is a schematic illustration of a steering system for a vehicle having an electric steering or servo motor,

(3) FIG. 2 shows a section through the steering housing of the steering system at the height of a pinion shaft for torque transmission from the servo motor to a toothed rack.

DETAILED DESCRIPTION

(4) In the Figures, components which are the same are provided with the same reference numerals.

(5) FIG. 1 illustrates a steering system 1 for a vehicle by way of example. The steering system 1 comprises a steering shaft 2 via which a steering angle which is predetermined by the driver via the steering wheel is transmitted, a steering housing 3 having a steering gear mechanism which is received therein and a steering rod assembly having a toothed rack 4 via which the steering movement is transmitted to the steerable wheels of the vehicle. In order to support the manual torque applied by the driver, there is used an electric steering or servo motor 5 which produces a servo torque which is fed via a pinion shaft 9 into the steering gear mechanism in the steering housing 3. In the embodiment, the electric servo motor 5 is arranged in an axially parallel manner with respect to the toothed rack 4, the motor shaft longitudinal axis 6 of the servo motor 5 extends parallel with the longitudinal axis 7 of the toothed rack 4. The servo housing 8 in which the servo motor 5 is arranged is constructed separately from the steering housing 3, but is securely connected to the steering housing 3, for example, screwed.

(6) A sensor system 23 is arranged between the steering shaft 2 and the steered wheels.

(7) It is also possible for the steering shaft 2 to be connected directly to the pinion shaft 9.

(8) The electric servo motor 5 is, for example, constructed as an electronically commutated synchronous or asynchronous motor.

(9) FIG. 2 shows a longitudinal section through the pinion shaft 9 in the steering housing 3. The pinion shaft 9 is rotatably supported in two bearings in the steering housing 3 in which a fixed bearing 10 with axial and radial fixing and a floating bearing 11 with only radial fixing of the pinion shaft 9 are involved. The fixed bearing 10 has an inner ring 10a and an outer ring 10b, wherein the inner ring 10a is positioned directly on the pinion shaft 9 and is supported with an axial end side axially on a projection 12, which is constructed integrally with the pinion shaft 9. The opposing end side of the inner ring 10a of the fixed bearing 10 is supported axially by a hub 13 which is pushed with press-fitting onto the pinion shaft 9 and which is connected in a rotationally secure manner to the pinion shaft 9. The hub 13 is a carrier of a worm wheel 14 which meshes with a screw 15 and which is driven thereby. The screw 15 which is located in a portion of the steering housing 3 is connected to the motor shaft of the electric servo motor 5 or is driven via a coupling by the motor shaft. The hub 13 may be supported axially via a securing ring 22 on the pinion shaft 9.

(10) The outer ring 10b of the fixed bearing 10 is supported axially at one end on a housing projection 16 of the steering housing 3. At the opposing end side, the outer ring 10b is axially supported on a securing ring 17, which is inserted into an inner groove 18 in the steering housing 3.

(11) The floating bearing 11 is located with a larger axial spacing—with respect to the longitudinal axis 19 of the pinion shaft 9—from the worm wheel 14 than the fixed bearing 10. The floating bearing 11 is located adjacent to the end side of the pinion shaft 9 in the steering housing 3. Between the fixed bearing 10 and the floating bearing 11, there is arranged the pinion tooth 25 arrangement by means of which the pinion shaft 9 is in toothed engagement with the toothed rack 4.

(12) As a result of the fact that both the fixed bearing 10 and the floating bearing 11 of the pinion shaft are located in the steering housing 3, a precise guiding and support of the pinion shaft 9 is ensured, whereby the friction and the noise generation are reduced and a long service-life is ensured.

(13) The steering housing 3 is, in a manner adjacent to the end side of the pinion shaft 9 on which the floating bearing 11 is arranged, provided with an opening 20, which is located in an axial extension of the pinion shaft 9. There is located adjacent to the opening 20 a radially inwardly protruding, housing-side projection 21 which reduces the free diameter of the opening 20 and which prevents the floating bearing 11 from becoming disengaged via the opening 20.

(14) For assembly, in a first step, the floating bearing 11 is introduced into the steering housing 3 via the opening axially opposite the opening 20. Subsequently, in a next step, the pinion shaft 9 is inserted with the fixed bearing 10 placed thereon into the steering housing 3 until the outer ring 10b of the fixed bearing 10 abuts axially against the housing projection 16. In another step, the securing ring 17 is inserted into the inner groove 18 and the outer ring 10b of the fixed bearing 10 is thereby axially fixed. Subsequently, the hub 13 including the worm wheel 14 is pushed axially as a press-fit onto the pinion shaft 9 until the end side of the hub 13 abuts the inner ring 10a of the fixed bearing 10.

LIST OF REFERENCE NUMERALS

(15) 1 Steering system

(16) 2 Steering shaft

(17) 3 Steering housing

(18) 4 Toothed rack

(19) 5 Electric servo motor

(20) 6 Motor shaft longitudinal

(21) 7 Longitudinal axis

(22) 8 Servo housing

(23) 9 Pinion shaft

(24) 10 Fixed bearing

(25) 10a Inner ring

(26) 10b Outer ring

(27) 11 Floating bearing

(28) 12 Pinion shaft projection

(29) 13 Hub

(30) 14 Worm wheel

(31) 15 Screw

(32) 16 Housing projection

(33) 17 Securing ring

(34) 18 Inner groove

(35) 19 Longitudinal axis

(36) 20 Opening

(37) 21 Projection

(38) 22 Securing ring

(39) 23 Sensor system