WO2011015374A1

WO2011015374A1 - Power steering system having preloaded, split bearing ring

Info

Publication number: WO2011015374A1
Application number: PCT/EP2010/004841
Authority: WO
Inventors: Helmut Bareis; Rainer SCHÄNZEL; Gerd Speidel; Alexander VÄHNING; Andreas Lay
Original assignee: Zf Lenksysteme Gmbh
Priority date: 2009-08-06
Filing date: 2010-08-06
Publication date: 2011-02-10

Abstract

The invention relates to a power steering system (1), particularly an electrical power-assisted steering system for a vehicle, comprising a leading screw (3) that is driven by a servo motor (2) and made of a nut (5) mounted in an axially substantially immobile manner in a frame (4) and an axially displaceable component (6), the thread (7) of which engages in a nut thread (8) of the nut (5), and further comprising a rolling bearing (9) for axially and radially mounting of the nut (5) in the frame (4). In order to provide a power steering system having minimized operating noise and operating play that is always within a predetermined range, according to the invention at least the inner ring (10) or the outer ring (26) of the rolling bearing (9) is split along a parting plane (11) running approximately perpendicular to the axially displaceable component (6) into two ring parts (12, 13), and the ring parts (12, 13) are installed in the frame (4) with axial spacing (a) from one another and spring-loaded with respect to one another by at least one spring element (14).

Description

POWER STEERING WITH PRE-TENSIONED, DIVIDED BEARING RING

The invention relates to a power steering, in particular an electrical

Power steering system for a vehicle, with a, driven by a servomotor motor screw from a substantially axially immovably mounted in a frame nut, according to the preamble of claim 1.

The DE 103 10 492 A1 shows and describes an electric power steering wherein a servo motor drives an axially displaceable component that with his

Ball screw is in engagement with a nut thread of an axially fixed in a frame mounted nut. The nut is connected to a pulley of a traction mechanism between the servomotor and the thus formed

Motion screw rotatably connected. The nut is supported and mounted on the frame via a radial bearing. The radial bearing is formed as a rolling bearing and in particular as a four-point bearing, since in particular axial forces are to be absorbed.

However, occurring during operation of such power steering, rapidly changing axial forces on the bearing rings of a pertinent bearing cause

in particular by different heating of the bearing rings of the bearing

Start of operation of the power steering Tolerances in the rolling bearing. Through this

Tolerances may occasionally cause rattling noises at the beginning of a power steering operation, until a steady state blow is achieved

Heating the components of the bearing ultimately sets the design specified operating clearance. At low operating temperatures, the bearing clearance is unfavorably small in relation to the bearing friction. In addition, with the rolling bearing can not always sufficiently offset on a shaft mounted therewith bending moments by a misalignment so that a low pivoting moment results and jamming of the shaft is avoided.

The known rolling bearing types are not always able to prevent noise in the specific operating range in a power steering system.

The invention has for its object to provide a power steering, the operating noise is minimized, in particular their bearings a radial play and

BESTATIGUNGSKOPIE Axial play does not rise above the operating clearance under the influence of ambient temperatures of the rolling bearing.

The object is achieved with a power steering system with the features of claim 1.

Characterized in that at least one bearing ring - the inner ring or the outer ring - of the rolling bearing along an approximately perpendicular to the shaft separating plane in two ring parts, preferably divided into two ring halves and the ring halves with axial distance from each other with at least one spring element against each other springing in the steering system are installed, a power steering is provided, which is able to adjust the bearing clearance in the rolling bearing to the current operating temperature, or to allow a constant bearing clearance over the operating temperature. The inner ring or the outer ring or both bearing rings of the bearing are radially biased in a defined manner, preferably by dividing the inner ring and the ring halves of the inner ring are axially clamped against each other. This can be compensated by the sequence of heating of the outer ring first and then warming up of the inner ring and a cage and the rolling elements in a over the respective operating time of the power steering and in particular of the rolling bearing operating play to the effect that the increasing axial bearing clearance compensated by the heating of the outer ring can be. The ring halves or parts of the inner ring are pressed by the spring element against each other and the rolling elements pressed slightly radially to the outer ring, or with the desired operating clearance between the

Inner ring parts or inner ring halves held. A perfect compensation of thermal expansion of the bearing rings and a constant operating clearance of the bearing is effected. Disturbing operating noise does not occur.

Preferred embodiments emerge from the subclaims.

In one embodiment, the inner ring of the rolling bearing is divided into two ring halves and spring-loaded against each other by a plurality of axially acting on both ring halves spring elements. In one embodiment, the outer ring of the rolling bearing is divided into two ring halves and spring-loaded against each other by a plurality of spring elements axially acting on both ring halves The spring elements or the spring element may be formed of an elastomeric material or of a metallic material such as spring steel. The

Spring elements may be, for example helical compression springs, which are arranged at intervals to each other around the circumference of the ring halves, between the component, which acts as a frame for the shaft to be supported, and the end faces of the

Support ring halves. The helical compression springs spring the ring halves of the

Inner or outer ring against each other.

In another embodiment, one or more spring elements may be provided which engage or pass through axially guided openings in the ring halves or are otherwise secured to the ring halves in a suitable manner so that they are spring-loaded against each other by the tensile force of the spring elements. This embodiment of the rolling bearing has the advantage that the respective ring halves are fixed to the other components of the bearing and the rolling bearing is easy to handle and assemble.

Unlike known oblique bearings, the respective ring halves of the inner or outer ring are preferably constructed symmetrically with respect to the parting plane. Preferably, the rolling elements of the rolling bearing are formed as balls and form a deep groove ball bearing or a four-point bearing. The ring halves are axially sprung in a particularly preferred embodiment with the aid of one or two disc springs. The disc springs may be slotted radially over a portion of their width to define the spring rate. In particular, radially guided slots may be guided from their inner peripheral edge over part of their width. It is expedient to bring about an application of the spring force on axially outer end faces of the respective inner or outer ring to adapt the disc springs in their radial dimensions to the respective sprung bearing ring or ring part or half. It may also be expedient to choose the disk springs in their radial dimensions so that they pass into a radial region of sealing disks of the rolling bearing. The disc springs can thus partially or completely take over the task of bearing washers. The installation tolerances of the ring parts or halves together with disc springs and the axial gap between the ring parts or - halves can be chosen so that in a cold state in which the power steering is not in operation, the disc springs almost block on the ring halves or - share and axial stops come to rest. The rims of the split inner or outer ring may be higher than the undivided ring. In addition, the rolling bearing can receive a larger pressure angle.

The invention will now be described in more detail with reference to an embodiment and reproduced with reference to the drawing. In the drawing show:

Fig. 1 is a partial longitudinal section through a steering gear of a

Power steering according to the invention, Fig. 2 is an enlarged view of an embodiment of a

inventive rolling bearing in a power steering,

3 is a perspective view of a spring element for the axial springing of ring halves of the rolling bearing in FIGS. 1 and 2.

Fig. 4 is an illustration of only the storage area of an embodiment with

shared external warehouse

In Fig. 1 a partial longitudinal section through a power steering system formed as an electric power steering system 1 for a passenger car is shown. basics

Components of the power steering 1 are formed as a closed steering gear housing 22 frame 4 made of die-cast aluminum. The steering gear housing 22 has a radial flange on which an electric servomotor 2 is screwed by means of bolts. The electric servomotor 2 serves to provide a

Steering assistance force on a threaded portion 23 of a rack 24. The rack

24 shows an axially displaceable component 6 in the steering gear housing 22. At not shown axial ends of the rack 24 articulated tie rods are set, which are used with wheel steering steered wheels of the passenger car for steering angle adjustment of the wheels at an axial displacement of the rack 24. The threaded portion 23 of the rack 24 is with its thread 7 with a female thread 8 of a nut 5 in engagement. The nut 5 is formed as a ball nut 25 or ball nut. A driven by the electric servomotor 2 motion screw 3 is formed. The ball nut 25 is around the

Threaded portion 23 rotatably mounted in the frame 4, but arranged axially largely immovable. The ball nut 25 is axially and radially mounted on a bearing ring formed as an inner ring 10 and a bearing ring formed as an outer ring 26 of a rolling bearing 9 in the frame 4 or steering gear housing 22. The rolling bearing 9 is formed as a deep groove ball bearing 21. The outer ring 26 of the rolling bearing 9 is between two axial stops forming bearing plates 27, 28 in one

Housing cover 29 of the steering gear housing 22 set. The electric

Servomotor 2 is operatively connected via a traction mechanism with the nut 5, wherein a belt formed as a toothed belt 30 runs on a pulley 31 on the nut 5. The pulley 31 is formed in the manner of a stepped cylindrical sleeve. It is with its, the rolling bearing 9 facing end 32 to a peripheral bead

33 of the mother 5 abutting. The peripheral bead 33 in turn forms a stop for the inner ring 10 and the ring portion 13 of the inner ring 10. A nut 34 which is turned on an outer peripheral surface of the ball nut 25, forms a stop 33 opposite the stop 34 for the inner ring, whose construction in Described in more detail below. The belt 30 also runs on one

Pulley 36 which is rotatably connected to a motor shaft of the electric servomotor 2, from.

The servo motor 2 is driven by a control and / or regulating device, not shown, in accordance with sensor signals which represent a desired steering angle and a wheel steering angle. It can be operated with pulse width modulation. As a result, the ball nut 25 is rotated in one direction or the other and the rack 24 is displaced in one or the other direction. On the ball nut 25, on the other hand, axial forces derived from the wheel reaction forces are introduced. In addition, resulting in steering movements on a steering handle in one or the other direction changing axial forces on the ball nut 25, which act on the rolling bearing 9. At the beginning of operation, the outer ring 26 of the heated

Rolling bearing 9 first, since heat usually from an engine room in which the steering gear housing 22 is mounted, first from the outside to the

Steering gear housing 22 and the housing cover 29 is blasted. As shown in Figures 1 and 2, the inner ring 10 is divided along a centrally extending in the radial direction of the rolling bearing 9 dividing plane 11 in two symmetrically to this parting plane 11 formed ring parts or ring halves 12,13. In each case, the facing on the parting plane 11 end faces 37,38 of

Ring halves 12,13 parallel to each other and arranged at an axial distance a to each other so that the ring halves 12,13 axially on the parting plane 11 can be pushed to and away.

The ring halves 12,13 are spring-loaded against each other by spring elements 14 formed as disc springs 17. For this purpose, the plate springs 17, of which only an exemplary embodiment in FIG. 3 is shown in a perspective view, between the peripheral bead 33 on the ball nut 25 and an end face 15 of the ring member 13 and the other, formed by the nut 34 stop 35 and another end face 16 of the ring member 12 from. The disc springs 17 in the embodiments in Figures 1 to 3 are in the cold state

Power steering 1 built almost block and have a spring force of about 100 N to 200 N, with each of which they each spring the ring halves 12,13 against each other. The axial distance a of the ring halves 12, 13 remains, as shown in particular in FIG. 2, approximately at its maximum dimension. The disc springs 17 have one

Inner radius of its inner peripheral edge 18, which is about the inner radius of the

Inner ring 10 corresponds. The outer radius r, however, is larger than the largest

Outer radius of the inner ring 10, so that the disc springs 17 radially at least partially each project beyond an outer surface of sealing disks 39 on both sides of the rolling elements of the rolling bearing 9. The disk springs 17 protrude radially into a sealing disk region 20.

The plate spring 17 in the embodiment shown in FIG. 3 has from its inner peripheral edge 18 radially star-shaped around the entire circumference of the respective plate spring 17 slots 19, which protrude over half the width of the plate spring 17 and formed against notch effect, semicircular ends 40 have.

The ring halves 12,13 of the inner ring 10 each form a partial track for balls 41 of the rolling bearing 9 and are at the axial distance shown a to the balls. Upon heating of the outer ring 26 and subsequent heating of the inner ring 10 results in a widening of the shoulders of the outer ring 26 connected to the need for the consequent axial play on a

Reduce operating play again. For this purpose, the inner ring 10 is like described split and the ring parts or in the embodiment shown, the ring halves 12,13 are axially spring-loaded. This makes it possible that when the outer ring 26 heats up, the inner ring halves 12, 13 can axially move towards one another and the distance dimension a is slightly reduced. The balls 41 are thereby guided without play, at least by the inner ring 10, until both rings 10,26 of the rolling bearing 9 have approximately the same temperature and the constructive provided tolerance position of the two rings 10, 26 is taken. The distance a is again increased slightly. By the use of disc springs 17 as spring elements for the ring halves

12,13 results in a space-saving, structurally simple solution that

Operating clearance of the rolling bearing 9 always keep in a desired range regardless of current temperatures of the components of the rolling bearing 9. The disc springs 17 may come to rest in circumferential notches on the nut 5, so that a simple mounting option and a cohesion of the ring halves 12,13 may result during assembly on the nut 5.

Figure 4 shows a deep groove ball bearing 21, which is supported with an outer ring 26 on a frame 4, a housing wall of the steering gear housing. The outer ring 26 is held in an inner circumferential groove 4 'with a rectangular, U-shaped cross-section. The

Inner circumferential groove 4 'has approximately a depth corresponding to the thickness of the outer ring 26. The inner circumferential groove 4 'is wider than the roller bearing 9 and its outer ring 26. As shown in FIG. 4, the outer ring 26 of the rolling bearing 9 is symmetrical to a parting plane 11 arranged at an angle of 90 ° to a longitudinal axis of the rolling bearing 9 in two ring parts 12, 13 shared. The ring parts 12, 13 each form one

Partial raceway for the balls 41 of the rolling bearing 9 and lie with axial

Distance a at their inner end faces to each other on the balls 41 at. The ring parts 12, 13 are provided with spring elements 14 which are shown in FIG

Embodiment as helical compression springs 14 'are formed and spaced from each other about the outer end faces 15, 16 of the outer ring 26 are pressed against each other, without the distance a, however, could reduce to a zero dimension. Due to the mutual springing of the ring halves 12, 13 there is the possibility that the outer ring 26 always interacts independently of thermal expansion of all components of the rolling bearing 9 with almost the same operating clearance with the balls 41. The inner ring 10 is axially immovable by suitable securing elements, such as snap rings 42 at its two end faces the shaft 6 or ball nut 25 is held.

In order to effect a limited desired tiltability of the rolling bearing 9, for example, to better control bending moments in the shaft to be supported and their clamping action on the rolling bearing 9, in a particularly preferred embodiment of the rolling bearing 9, a ring with spherical or convex outer contour to placed the outer ring 26 or the inner ring 10 of the rolling bearing 9. With the help of the ring, the roller bearing 9 is supported on the respective component of the steering system, such as a ball nut 25 and can tilt relative to the ball nut 25 under the influence of bending moments about on a cross-ball nut 25 spindle without jamming in any way ,

Due to the design of the rolling bearing 9 according to the invention is always

consistent clearance allows and increased wear in the bearing

9 avoided, since during operation occurring thermal expansions of the

Rolling 9 have no effect on the tolerances of the bearing 9, since they are balanced.

LIST OF REFERENCE NUMBERS

1 power steering

2 servomotor

3 motion screw

4 frame

4 ¹ inner circumferential groove

5 mother

6 component, axially displaceable

7 threads

8 female thread

9 rolling bearings

10 inner ring

11 parting plane

12 ring part

13 ring part

14 spring element

14 "helical compression spring

15 face

16 face

17 plate spring

18 peripheral edge

19 slot

20 sealing disc area

21 deep groove ball bearings

22 steering gear housing

23 threaded section

24 rack

25 ball nut

26 outer ring

27 bearing washer

28 bearing disc

29 housing cover

30 straps

31 Pulley, to 5

32 front side 33 circumferential bead

34 mother

35 stop

36 Pulley

37 face

38 face

39 sealing washer

40 end, v. 19

41 ball

42 snap ring

a distance, axial r outer radius, v. 17

Claims

1. Power steering, in particular electric power steering for a vehicle, with a, of a servo motor (2) driven movement screw (3) from a substantially axially immovable in a frame (4) mounted nut (5) and an axially displaceable component (6) whose thread (7) is in engagement with a nut thread (8) of the nut (5) and with a roller bearing (9) for axially and radially supporting the nut (5) in the frame (4), characterized in that at least the Inner ring (10) or the outer ring (26) of the rolling bearing (9) along an approximately perpendicular to the axially displaceable component (6) extending parting plane (11) is divided into two ring parts (12,13), wherein the ring parts (12,13 ) at an axial distance (a) from each other and with at least one spring element (14) spring-loaded against each other in the frame (4) are installed.

2. Power steering system according to claim 1, characterized in that the ring parts

(12,13) are spring-loaded with oppositely acting spring elements (14).

3. Power steering system according to claim 1 or 2, characterized in that the

Spring elements (14) are formed from an elastomeric or metallic material.

4. Power steering system according to one of claims 1 to 3, characterized in that the spring elements (14) are helical compression springs at intervals around each other around the end faces (15,16) of the ring parts (12,13) between the frame (4) Power steering (1) and the end faces (15,6) are supported.

5. Power steering system according to one of claims 1 to 3, characterized in that the spring element (14) or a plurality of spring elements (14) pass through the ring members (12,13) axially or overlap and a tensile force, the ring parts (12,13 ) pulls against each other, applies.

6. Power steering system according to one of claims 1 to 3, characterized in that the spring element (14) is a plate spring (17).

7. Power steering system according to claim 6, characterized in that the plate spring

(17) or a plurality of disc springs (14) has a slotted peripheral edge (18).

8. Power steering system according to claim 7, characterized in that the peripheral edge

(18) has radially inwardly directed slots (19).

9. Power steering system according to one of claims 6 to 8, characterized in that the plate spring (17) or a plurality of disc springs (17) have approximately the same radial dimensions as the sprung ring parts (12,13).

10. Power steering system according to one of claims 6 to 8, characterized in that the plate spring (17) or a plurality of disc springs (17) radially in a sealing disc region (20) of the rolling bearing (9) protrudes.

11. Power steering system according to one of claims 6 to 10, characterized in that the plate spring (17) or a plurality of disc springs (17) outside the operation of the power steering (1) are mounted approximately block.

12. Power steering system according to one of claims 1 to 11, characterized in that rolling elements of the rolling bearing (9) balls (41).

13. Power steering system according to one of claims 1 to 12, characterized in that the rolling bearing (9) is a deep groove ball bearing (21) or a four-point bearing or the

Rolling elements of the rolling bearing (9) are tons.

14. Power steering system according to one of claims 1 to 13, characterized in that the inner ring (10) and the outer ring (26) of the rolling bearing (9) has a

have symmetrical cross-section relative to the parting plane (11).

15. Power steering system according to one of claims 1 to 14, characterized in that between the rolling bearing (9) and the shaft (6) with a convex

Cross-sectional profile of the rolling bearing (9) facing, annular component is arranged, wherein the component allows a tilting movement of the rolling bearing (9).

16. Power steering system according to one of claims 1 to 11, characterized in that between the rolling bearing (9) and the frame (4) of the steering system with a convex cross-sectional profile of the rolling bearing (9) facing annular component is arranged, wherein the component is a Tilting movement of the rolling bearing (9) allows