DE102021209636A1 - Power steering for a motor vehicle - Google Patents

Abstract

The present invention relates to a power steering system (1) for a motor vehicle, comprising a threaded spindle (4) which can be axially displaced in a housing (31) in the direction of its spindle axis (S) and which can be rotated in a bearing arrangement (7 ) mounted spindle nut (62) engages, the bearing arrangement (7) having a bearing ring (71) which is held in a support element (8) which has a radial section (81) which supports the bearing ring (71) on the outside in a radially resilient manner against the housing and an axial section (82) which supports the bearing ring (71) at the end face in an axially resilient manner against the housing (31). In order to enable improved elastic mounting of the bearing ring (71), the invention proposes that the radial section (81) and/or the axial section (82) be designed in a corrugated manner, at least in sections.

Description

The invention relates to a power steering system for a motor vehicle, comprising a threaded spindle which can be displaced axially in a housing in the direction of its spindle axis and which engages in a spindle nut which is rotatably mounted in a bearing arrangement in the housing, the bearing arrangement having a bearing ring which is held in a support element, which has a radial section that supports the bearing ring on the outside in a radially resilient manner against the housing and an axial section that supports the bearing ring on the front side in an axially resilient manner against the housing. A support element for use in a power steering system is also the subject of the invention.

In the case of power steering, in addition to a steering command introduced manually via the steering wheel into the steering shaft, an auxiliary force is generated by an electromotive auxiliary drive and coupled into the steering train to support the steering movement of the steered wheels.

In rack and pinion steering, a steering pinion is attached to the steering shaft, which in a steering gear engages with a rack that is linearly displaceably mounted in a housing and is connected to the tie rods of the steered wheels, so that manual rotation of the steering shaft causes a displacement of the steering wheel Rack causes, and thereby generates a steering angle.

In the prior art it is, for example, from DE 10 2013 006 432 A1 or the JP 2018-111412 A known to provide a motor-driven spindle drive in a rack and pinion steering, with which a linear auxiliary force can be applied to the rack. The threaded spindle of the spindle drive, the spindle axis of which extends axially in the direction of displacement of the rack, is firmly connected to the rack and engages in a spindle nut, which is rotatably supported in the housing and supported axially. Via a gear wheel, which is coaxially non-rotatably connected to the spindle nut, for example in the form of teeth running around the outside of the spindle nut, the spindle nut can be driven in rotation by means of an electric motor in order to linearly move the threaded spindle together with the toothed rack in the housing in the axial direction and in this way to couple an assistant.

The spindle drive can preferably be designed as a ball screw drive (KGT), in which balls can roll around between the spindle nut designed as a ball nut and the thread of the threaded spindle. The spindle nut is mounted in a bearing arrangement which has a bearing ring supported on the housing, for example an outer ring of a roller bearing, the inner ring of which is connected to the spindle nut. In order to avoid tension, it is known from the prior art mentioned to hold the bearing ring elastically in the housing via a support element, so that tension and tilting due to dynamic loads during operation can be compensated for.

That from the mentioned JP 2018-111412 A known support element has a radial section and an axial section. The radial section is formed by a hollow-cylindrical tube section which is conically widened in sections in order to radially and elastically support the bearing ring against the bearing mount in the housing. The axial section adjoins the radial section axially, which is designed as an annular disk section protruding radially inwards into the passage of the radial section and having a conical edge section, similar to a disk spring. The axial section supports the end face of the bearing ring in an axially elastic manner against an axial abutment of the housing. As a result, tilting of the bearing relative to the housing can be compensated for in an elastically yielding manner. A disadvantage, however, is the asymmetrical support and limited spring effect of the conical radial and axial sections.

In view of the problems explained above, it is an object of the present invention to enable improved elastic mounting of the bearing ring.

Presentation of the invention

This object is achieved according to the invention by the power steering system with the features of claim 1 and the support element according to claim 15. Advantageous developments result from the dependent claims.

In a power steering system for a motor vehicle, comprising a threaded spindle which can be displaced axially in a housing in the direction of its spindle axis and which engages in a spindle nut which is rotatably mounted in a bearing arrangement in the housing, the bearing arrangement having a bearing ring which is held in a support element which has a has the bearing ring on the outside radially resiliently against the housing and an axial portion that supports the bearing ring at the end face axially resiliently against the housing, the invention provides that the radial portion and/or the axial portion are at least partially corrugated.

According to the invention, the radial section and/or the axial section have a radial corrugated spring or an axial corrugated spring or are inherently as such trained. Such a corrugated spring has a plurality of waves, which are formed by wave troughs and wave crests that follow one another alternately in the course of the circumferential direction. A major advantage of corrugated springs over conical disc springs or the like is that the majority of the convexly protruding corrugation crests distributed over the circumference form defined contact surfaces between the bearing ring and the housing, which enable better defined support even with relative tilting. A further advantage is that the amplitude of the wave shape means that a greater spring deflection can be provided than would be possible using simple conical disc springs. This can ensure that even under unfavorable operating conditions, for example due to extremely high or rapid load changes, the axial and radial sections have a defined contact with the bearing ring and housing, as a result of which rattling and other undesirable noises can be reliably avoided. In addition, wear can be reduced.

The axial section is arranged on an end face of the support element. The radial section is connected to the axial section on its side facing the latter, and is directed axially away from the axial element on its opposite, remote side.

Provision is preferably made for the radial section to have wave crests which are directed radially alternately inwards and outwards. The radial section can be formed by a tubular section or ring section, which in its basic form is hollow-cylindrical, from which the wave crests with their wave crests protrude alternately in a convex manner radially inwards and outwards. As a result, a plurality of shafts, preferably arranged evenly distributed over the circumference, can be implemented. The wave crests of the wave crests follow one another in the circumferential direction and are alternately supported radially inward against the bearing ring and in the circumferential direction in between radially outward against the housing, preferably against a radial inner surface of the housing cylindrically enclosing the bearing ring. Due to the radially opposite contact areas at the shaft crests, a sequence of three-point bearings distributed over the circumference is implemented in practice. This results in an advantageous radially elastic mounting of the bearing ring, with a greater spring deflection and better defined support than in the prior art being possible.

Provision is preferably made for the axial section to have wave crests directed alternately in and against the axial direction of the spindle axis. The axial section can be formed by an annular disk that is flat in its basic shape, from which the wave crests with their wave crests alternately protrude convexly axially in one axial direction or in the opposite axial direction. As a result, a plurality of shafts, preferably arranged evenly distributed over the circumference, can be implemented. The wave crests of the wave crests follow one another in the circumferential direction and are alternately supported axially against the bearing ring, and in the circumferential direction between them directed axially away from the bearing ring and outwards against the housing, preferably against an axially opposite axial inner surface of the bearing ring on the front side housing. Due to the axially opposing contact areas at the shaft crests, a sequence of three-point bearings distributed over the circumference is practically implemented. This results in an advantageous axially elastic mounting of the bearing ring, with greater spring deflection and better defined support being possible than in the prior art.

Preferably, the corrugations are continuously rounded in an arc shape. As a result, a uniform elastic characteristic of the spring action can be implemented. In addition, potentially harmful high point loads in the contact areas on the bearing ring and on the housing can be safely avoided.

It is particularly advantageous that the radial section and the axial section are both designed in a wavy manner according to the invention. The stated advantages of the corrugated springs mutually reinforce each other in an advantageous manner, so that an optimized support and a particularly smooth running are made possible even under extreme operating conditions.

It is possible for the wave crests to be in the form of knobs. Nub-like means convexly protruding in the direction of the wave crest, preferably with a rounded or flattened crest area. The wave crests can each be produced as a local indentation with a substantially constant wall thickness, for example by pressing in or embossing. It is also possible to produce wave crests by locally thickening the wall of a tubular radial section or a disk-shaped axial section, for example as bead-shaped, axially or radially protruding projections.

The crests of the waves, even if they are designed like nubs, can be designed to be elongated, namely in the axial direction in the radial section and in the radial direction in the axial section. The wave crests can preferably extend over a predominant part of the width, ie the axial width of the radial section; and the radially measured width of the axial section. As a result, an elongated, approximately linear contact surface is realized, which bears against the bearing ring or the housing in a spring-loaded manner. This leads to a clearly defined and secure mounting of the bearing ring.

An advantageous development can provide that the radial section has axial slots. In the preferably tubular basic shape of the radial section, two, three or more axial slots can be spaced apart in the circumferential direction. The axial slots are preferably distributed uniformly over the circumference and extend in the axial direction at least over part of the axial width of the radial section, preferably over a predominant part. A corrugated spring segment extending in the circumferential direction can be formed between two axial slots; in other words, the axial slots divide the radial section into circumferential segments. Each of these corrugated spring segments can be radially resiliently deflected individually and essentially independently of the other corrugated spring segments. This advantageously results in greater flexibility, which enables better elastic adaptation to the bearing ring and the housing, as a result of which the contact reliability is increased and the formation of noise is correspondingly prevented. In addition, assembly is simplified.

The axial slots can be introduced into the radial section from an axial direction, for example from the end face facing away from the axial section, that is to say the open end of a tubular radial section. An advantageous embodiment can be that the axial slots are introduced from different axial directions. Viewed in the circumferential direction, the axial slots are introduced into the radial section alternately in or counter to the axial direction. As a result, a type of zigzag course of the radial section in the axial direction is delimited by the axial slots. The slit openings are alternately open in or against the axial direction, ie starting from the axial section or directed against it. Viewed in the circumferential direction, the open slot cross-sections overlap, so that the added slot lengths can actually extend over the entire width of the radial section or even beyond into the axial section. One advantage of this arrangement is that the radial elasticity is made more uniform over the entire axial length of the radial section.

An advantageous development can provide that circumferential slots are formed between the radial section and the axial section. The circumferential slots each extend in the circumferential direction over a partial circumferential section, along the circumferential edge region between the radial section and the axial section. A plurality of circumferential slits distributed over the circumference are preferably introduced. As a result, the radial section and the axial section are advantageously decoupled from one another in such a way that radial and axial spring movements are made possible practically independently of one another. This increases the contact security and the holding effect, and the noise is further reduced.

A possible advantageous development is that at least one axial slot is connected to a peripheral slot. The combination results in a T- or L-shaped slot progression. As a result, the advantageous effects of axial and circumferential slots mentioned can be combined with one another in such a way that they reinforce each other. In this way, greater flexibility can be achieved, which allows elastic deformation of the support element itself, and at the same time enables optimized decoupling of the corrugated spring segments and improved introduction of the spring force into the bearing ring and the housing. Another advantage is the reduction of punctiform shearing loads on the support element during elastic deformations. As a result, the supporting element can advantageously be made lighter, and long-term stability and operational reliability are increased.

It is also possible for the axial section to have radial slots. These can preferably be distributed over the circumference, preferably evenly. They each extend in a radial direction, for example radially as viewed from the spindle axis, at least over part of the radial width of the axial section. As a result, the axial section can be subdivided into radial segments, which can be designed, for example, as axial corrugated spring segments. This segmentation allows improved flexibility and decoupling of the spring action to be implemented, analogously to a segmented radial section as explained above.

It is possible that a radial slit can also be connected to a circumferential slit in order to realize a T-shaped or L-shaped slit course, as described above for the combination of axial and circumferential slits. It is also conceivable and possible to connect at least one radial slot to an axial slot, or to connect radial and axial slots to a peripheral slot, for example to form Z, double T, meandering or step-shaped or other advantageous shapes of slot profiles . As a result, a locally optimized adjustment of the elastic properties is possible, for example to achieve better retention effect with a simultaneously flatter spring characteristic in a different support area.

The support element can advantageously be designed as a one-piece molded part. It can have a metallic material and/or a plastic. For example, it can be manufactured from a metallic material, for example in one piece as a stamped pressed part made from sheet spring steel. This enables efficient production and a robust and space-saving design. It can also be provided that the support element is cheaply made available as a plastic injection-moulded part made of a thermoplastic polymer. In addition, it is conceivable and possible to at least partially provide a core made of a metallic material with a plastic, for example in the form of a coating, or by overmolding. As a result, an optimized adaptation to special shapes and loads, damping, sliding properties and the like can take place.

Provision can preferably be made for the bearing arrangement to comprise two support elements according to the invention which, in a mirror-inverted manner, form an arrangement which is mirror-symmetrical with respect to a transverse plane. The support elements can be attached to a bearing ring, or to the axially outer end faces of two axially spaced bearing rings. Irrespective of the number of bearing rings, the radial sections point towards one another axially, while the axial sections are arranged on both sides on the end faces of the bearing ring or rings that face away from one another.

As an alternative to the previous arrangement with two support elements, it is possible to use only one support sleeve, which is attached to a bearing ring on only one side. This can reduce overhead if less compensation is required.

The threaded spindle is preferably connected to a rack of a rack and pinion steering gear. As a result, the advantages according to the invention can be used in this special design of a power steering system.

The threaded spindle and the spindle nut preferably form a ball screw drive.

A bearing ring is preferably part of a roller bearing, preferably a bearing outer ring (outer ring), for example of a radial or angular contact ball bearing. The inner ring (bearing inner ring), which is rotatably mounted via the rolling elements arranged between them so that they can roll off, is connected to the spindle nut.

The spindle nut can be driven in rotation by a motor drive unit to generate an auxiliary force. This preferably has an electric motor which is coupled to the spindle nut via a transmission, for example via a drive worm which engages in a gear wheel which is non-rotatably coupled to the spindle nut. The gear wheel is mounted in the housing together with the spindle nut. The spindle nut can also be integrated into the gear wheel.

The invention also relates to a support element comprising a radial section designed to be radially resilient, with a passage running axially through it in the direction of a spindle axis, and an axial section arranged in the passage and designed to be axially resilient, in which it is provided that the radial section and/or the axial section are corrugated at least in sections are trained.

The support element according to the invention can have individual or any combination of the features that are described above in connection with the power steering system according to the invention.

character list

• 1 eine schematische perspektivische Ansicht eines erfindungsgemäßen Lenksystems,
• 2 einen Längsschnitt entlang der Spindelachse durch einen Spindeltrieb des Hilfskraftantriebs des Lenksystems gemäß 2,
• 3 eine Detailansicht aus 2,
• 4 ein erfindungsgemäßes Stützelement in einer schematischen perspektivischen Ansicht,
• 5 das Stützelement gemäß 4 in einer weiteren schematischen perspektivischen Ansicht,
• 6 eine ausschnittweise axiale Teilansicht des Stützelements gemäß 4 oder 5.

Advantageous embodiments of the invention are explained in more detail below with reference to the drawings. Show in detail:

• 1 a schematic perspective view of a steering system according to the invention,
• 2 according to a longitudinal section along the spindle axis through a spindle drive of the power-assisted drive of the steering system 2 ,
• 3 a detailed view 2 ,
• 4 a support element according to the invention in a schematic perspective view,
• 5 the support element according to 4 in another schematic perspective view,
• 6 a sectional axial partial view of the support element according to 4 or 5 .

Embodiments of the invention

In the various figures, the same parts are always provided with the same reference symbols and are therefore usually named or mentioned only once.

1 shows a schematic view of a power steering system 1 of a motor vehicle steering system. This includes a steering shaft 2, which at its rear end facing the driver's position in the vehicle interior, optionally connected to a steering wheel 21 via an intermediate shaft, not shown, and can be rotated to introduce a manual steering command, as indicated by the arrow.

The front end of the steering shaft 2 is rotatably supported in a housing 31 of a steering gear 3 .

In the housing 31 there is a threaded spindle 4 which extends in the direction of a spindle axis S and which is shown in the enlarged sectional view along the spindle axis S in FIG 2 can be seen, in its longitudinal direction, ie in the direction of said spindle axis S, displaceably mounted, as in 1 and 2 is indicated with a double arrow.

With the threaded spindle 4, a rack is connected, which also extends in the direction of the spindle axis. The rack has teeth with which a steering pinion mounted at the front of the steering shaft 2 and concealed within the housing 31 engages, so that a rotation of the steering shaft 2 is converted into a linear movement of the rack together with the threaded spindle 4 in the Housing 31. At its two ends, the toothed rack, and thus also the threaded spindle 4, is connected to the steering knuckles 52 of the steered wheels, not shown here, for the transmission of the steering force via tie rods 5 and rod ends 51.

An auxiliary power drive has an electric motor 32 attached to the housing 31, by which a gear wheel 6 can be driven in rotation about the spindle axis S. For this purpose, the gear wheel 6 is designed as a toothed belt wheel with a toothed ring coaxial to the spindle axis S on the outside, over which a toothed belt 61 runs, which can be driven by a drive wheel (not shown) of the motor 32 as is known from a toothed belt drive.

The gear wheel 6 is connected coaxially to a spindle nut 62 . In the example shown, the spindle nut 62 is designed as a ball nut or recirculating ball nut, with a threaded body 63 with helical circulation channels, between which and the turns of the thread of the threaded spindle 4 balls 64 run, which are fed back externally via a deflection body.

The spindle nut 62, and thus also the gear wheel 6, is rotatably mounted in a bearing arrangement with a bearing 7 designed as a radial roller bearing about the spindle axis S, and is supported axially, in the direction of the spindle axis S, against the housing 31.

The bearing 7 has an outer bearing ring 71, also referred to as the outer bearing ring or outer ring, in which balls 72 can be rolled on the inside. An inner ring 73 (bearing inner ring) rotatably mounted therein is firmly connected to the spindle nut 62 .

A ball screw drive is formed, in which the threaded spindle 4 can be displaced linearly axially in the direction of the spindle axis S by rotating the spindle nut 62 by means of the motor 32 . As a result, an auxiliary force supporting the steering torque introduced manually via the steering shaft 2 can be exerted on the toothed rack.

The bearing ring 71 is held and stored in the housing 31 via two support elements 8 according to the invention, which are in the 4 and 5 in different perspective views, and in 6 are shown in an axial partial view in the direction of the spindle axis S. The installation position results from 3 , which shows an enlarged section through the bearing 7.

In the example shown, the support element 8 is designed as a one-piece molded part, for example as a molded sheet metal part made of spring steel sheet.

The support element 8 has a radial section 81, which in its basic form is designed as a tubular section coaxial with the spindle axis S, and an axial section 82 connected thereto, which in its basic form is designed as a ring disk coaxial with the spindle axis S, which is attached to the end face of the radial section 81 , and projecting radially inwardly into the passage of the radial section.

The radial section 81 is embodied in a wavy manner along the circumference, with a plurality of wave crests 810 distributed evenly over the circumference, each with their wave crests convexly protruding radially outwards, and wave crests 811 arranged in between in the circumferential direction and protruding radially inwards.

The axial section 82 is embodied in a wavy manner over the circumference, with a plurality of wave crests 820 distributed evenly over the circumference, each with their wave crests convex, protruding axially outwards when viewed from the radial section 810, and axially oppositely arranged inwards in the circumferential direction in between Direction towards the radial section 810, protruding crests 821.

The radial section 810 has axial slots 83 and 84 distributed over the circumference. These are elongated axially, with the axial slots 83 being introduced from the free end of the radial section 81 facing away from the axial section 82 , and the axial slots 84 from the end of the radial section 81 at which it is connected to the axial section 82 . 6 shows a view of the free openings of the axial slots 83.

The axial slots 83 and 84 formed from opposite axial directions are so long that they overlap when viewed in the circumferential direction.

Wave crests 810 and 811 are designed as local, bead-like thickenings in the wall of radial section 81, which are convexly curved radially outwards or inwards and have a thickness D that is greater than the wall thickness between wave crests 810, 811.

The axial crests 820 and 821 can also be designed analogously as local, bead-like thickenings of the wall of the axial section 82, which are convexly arched axially outwards or inwards and have a thickness that is greater than the wall thickness between the crests 820, 821.

In the peripheral edge region between the radial section 81 and the axial section 82 , circumferential slots 85 are formed in the circumferential direction over a partial circumferential section. The axial slots 84 introduced from the axial section 82 are each connected to a circumferential slot 85 so that a T-shaped slot profile is formed. Only narrow webs 86 remain in the circumferential direction, via which the corrugated spring segments of the radial section 81, which are delimited between adjacent axial slots 83, 84, are connected to the outer edge of the axial section 82.

As in 3 As can be seen, the bearing ring 71 is accommodated in the radial sections 81 of two mirror-inverted, ie arranged mirror-symmetrically with respect to a transverse plane, and accommodated between the inner radial crests 811 (see 6 ) held. The radially outer crests 810 of the waves are correspondingly resiliently supported radially from the inside against the housing 31 .

The axial sections 82 lie with the inner axial 821 crests (see 6 ) axially from the outside against the bearing ring 71. The axially outer outer crests 820 are correspondingly resiliently supported axially from the inside against the housing 31 .

Reference List

1

power steering

2

steering shaft

21

steering wheel

3

steering gear

31

Housing

32

engine

4

lead screw

5

tie rod

51

rod end

52

steering knuckle

6

gear wheel

61

timing belt

62

spindle nut

63

threaded body

64

balls

7

bearing

71

bearing outer ring

72

balls

73

inner ring

8th

support element

81

radial section

810

wave crest

811

wave crest

82

axial section

820

wave crest

821

wave crest

83

axial slot

84

axial slot

85

perimeter slot

86

web

S

spindle axis

D

thickness

QUOTES INCLUDED IN DESCRIPTION

This list of documents cited by the applicant was generated automatically and is included solely for the better information of the reader. The list is not part of the German patent or utility model application. The DPMA assumes no liability for any errors or omissions.

Patent Literature Cited

• DE 102013006432 A1 [0004]
• JP 2018111412 A [0004, 0006]

Claims (15)

Power steering system (1) for a motor vehicle, comprising a threaded spindle (4) which can be displaced axially in a housing (31) in the direction of its spindle axis (S) and which is fitted in a spindle nut (62 ) engages, the bearing arrangement (7) having a bearing ring (71) which is held in a support element (8), which has a radial section (81) which supports the bearing ring (71) on the outside in a radially resilient manner against the housing and a bearing ring (71 ) has an axial section (82) which supports axially resiliently against the housing (31) on the end face, characterized in that the radial section (81) and/or the axial section (82) are at least partially corrugated. Power steering after claim 1 , characterized in that the radial portion (81) radially alternately inwardly and outwardly directed crests (810, 811). Power steering system according to one of the preceding claims, characterized in that the axial section (82) has crests (820, 821) directed alternately in and against the axial direction of the spindle axis. Power steering according to any of the preceding claims 2 or 3 , characterized in that the wave crests (810, 811, 820, 821) are constructed like knobs. Power steering system according to one of the preceding claims, characterized in that the radial section (81) has axial slots (83, 84). Power steering after claim 5 , characterized in that the axial slots (83, 84) are introduced from different axial directions. Power steering system according to one of the preceding claims, characterized in that circumferential slots (85) are formed between the radial section (81) and the axial section (82). Power steering system according to one of the preceding claims, characterized in that the axial section (82) has radial slots. Power steering according to any of the preceding Claims 5 until 8th , characterized in that at least one axial slot (84) is connected to a peripheral slot (85). Power steering system according to one of the preceding claims, characterized in that the support element (8) is designed as a one-piece molded part. Power steering system according to one of the preceding claims, characterized in that the supporting element (8) has a metallic material and/or a plastic. Power steering system according to one of the preceding claims, characterized in that the bearing arrangement (7) is arranged axially between two support elements (8). Power steering system according to one of the preceding claims, characterized in that the threaded spindle (42) is connected to a rack (4) of a rack and pinion steering gear. Power steering system according to one of the preceding claims, characterized in that the threaded spindle (42) and the spindle nut (62) form a ball screw drive. Supporting element (8), comprising a radial section (81) designed to be radially resilient with an axially continuous passage in the direction of a spindle axis (S), and an axial section (82) arranged in the passage and designed to be axially resilient, characterized in that the radial section (81 ) and/or the axial section (82) are at least partially corrugated.

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