DE102021206348A1 - Universal joint for a steering shaft of a motor vehicle, steering shaft for a motor vehicle steering system, steering system for a motor vehicle and universal joint for a universal joint - Google Patents

Abstract

The present invention relates to a universal joint (2) for a steering shaft (1) of a motor vehicle, comprising a universal joint (3) with two pairs of pins (31) arranged at right angles to one another and two joint forks (21) each with two arms (22 ), in each of which a journal (31) is mounted in a journal bearing (4) so that it can rotate about a journal axis (Z), and the end face of a journal (31) in each case has an axial bearing surface (45) arranged on the arm (21) in a contact area contacted axially, which is smaller than the end-side pin cross-section. In order to optimize the acoustics of one steering shaft, the invention proposes that the contact area (5) be designed in a coaxial, annular manner.

Description

State of the art

The invention relates to a universal joint for a steering shaft of a motor vehicle, comprising a universal joint with two pairs of journals arranged at right angles to one another and two joint yokes, each with two pairs of opposing arms, in each of which a journal is mounted in a journal bearing so that it can rotate about a journal axis, and wherein the end face of a journal makes axial contact in each case with an axial bearing surface arranged on the arm in a contact area which is smaller than the journal cross-section. A steering shaft for a motor vehicle steering system with such a universal joint, a steering system for a motor vehicle and a universal joint for a universal joint are also the subject of the invention.

In a motor vehicle steering system, the steering shaft is used to transmit the steering torque applied to the steering wheel via the steering spindle to the steering gear. To compensate for angular misalignment, at least one, usually two, universal joints are integrated along the course of the steering shaft, usually between the steering spindle and the intermediate shaft and between the intermediate shaft and the steering gear.

In the basic structure, each universal joint has two joint forks which are each attached to one shaft end of a steering shaft part and which each have two arms which extend axially in the direction of the shaft and are opposite one another transversely to the shaft axis. A spider has two pairs of oppositely radially projecting pivot pins, referred to as pins for short, which are arranged on pin axes that cross at right angles. The two journals of a pair of journals are mounted in the mutually opposite arms of a joint yoke in a respective journal bearing so as to be rotatable about their journal axis, which extends transversely to the shaft axis through the arms. The journal bearings are usually designed as radial roller bearings, for example as needle bearings.

In order to realize a play-free, low-noise operation and the highest possible rigidity of the joint arrangement during operation, in the DE 10 2014 116 271 A1 proposed to store and support the pin in each case on the front side against an axial bearing surface on the arm of the joint yoke, and preferably to prestress it in the direction of the pin axis by an axial spring force.

In order to form an end-face axial bearing, it is known that the journal contacts the bearing surface in a defined contact area that serves as a sliding surface and is smaller than the journal cross-section. For this it is from the DE 10 2014 116 271 A1 known to form the end face of the pin convex, or alternatively, as in the DE 692 10 205 T2 proposed to provide on the bearing surface against the pin axially projecting central projection. The known axial bearings have a relatively small, almost punctiform contact area arranged centrally on the journal axis, which is in any case smaller than the journal cross-section or the end face of the journal. In this point contact, the sliding speeds are relatively low and the bearing is smooth. However, there is a tendency towards undesirable noise development during steering operation.

In view of the problems explained above, it is an object of the present invention to optimize the steering shaft acoustically, in particular to reduce the noise generated in the universal joint during operation.

Presentation of the invention

This object is achieved according to the invention by the universal joint for a steering shaft of a motor vehicle having the features of claim 1, a steering shaft according to claim 13 and a steering system for a motor vehicle according to claim 14. Advantageous developments result from the dependent claims.

In a universal joint for a steering shaft of a motor vehicle, comprising a universal joint with two pairs of journals arranged at right angles to one another and two joint yokes, each with two pairs of opposite arms, in each of which a journal is mounted in a journal bearing so that it can rotate about a journal axis, and the end face of a journal axially contacts an axial bearing surface arranged on the arm in a contact area that is smaller than the journal cross-section, the invention provides that the contact area is coaxially annular in shape.

According to the invention, a ring contact is formed between the end face of the pin and the bearing surface, which ring contact has a circular contact area running annularly around the pin axis between the contact projection and the bearing surface. According to the invention, the central area enclosed by the ring contact is contact-free, i.e. there is no contact between the pin and the bearing surface.

The coaxial annular contact area forms an axial sliding surface, the outer diameter of which is preferably smaller than the front trunnion diameter, in other words within the front cross-section of the trunnion.

Preferably, the outer diameter can be larger than the diameter of a central point or area contact as is known in the art. An advantage of this increased outer diameter is an increased bearing radius with respect to rotation about the journal axis, as a result of which a higher sliding speed between the journal and the bearing surface in the contact area occurs at the same rotational speed compared to the prior art. This leads to a more uniform and optimized lubricant distribution of a lubricant introduced into the bearing for lubrication, preferably a lubricating grease. As a result, the axial bearing is already running more smoothly.

A further advantage is that by specifying the inner and outer dimensions of the ring contact according to the invention, the actually effective axial bearing surface can be defined and adapted in a structurally simple manner. An increased radial ring width can increase the axial bearing surface and thus reduce the surface pressure, thereby reducing the axial forces acting in the bearing gap, which can reduce noise, for example during vibrations or load changes. The reduced surface pressure also ensures easier and improved lubrication, which also benefits reduced noise development. Furthermore, this reduces wear compared to the prior art.

To optimize the running properties, the ring width can also be reduced until an almost linear contact area is achieved. This allows the bearing friction to be optimized.

According to the invention, a central area surrounded by the ring-shaped contact area is contact-free within the contact area. The central area, also referred to as the central inner area, lies coaxially within the ring contact in the area of the journal axis. There, the end face and the bearing surface have an axial distance from one another.

It can be provided that a central lubricant pocket is arranged in the journal and/or the bearing surface. This lubricant pocket can be formed in a contact-free area for accommodating a supply of lubricant, for example in the form of a depression arranged within the annular contact area in the journal and/or the bearing surface. Such a lubricant pocket can preferably be formed centrally, axially in the region of the pin axis, and be filled with a lubricant, such as lubricating grease. The lubricant enclosed in the interior of the contact area can reach the bearing gap directly radially outward and ensure continuous lubrication. Only negligibly small centrifugal forces act on the lubricant in the central area of the journal axis, so that it does not escape radially and the lubrication of the contact area is ensured in the long term. Due to the gap that decreases radially outwards from the lubricant pocket to the contact area, i.e. the distance between the journal bearing and the end face of the journal measured in the direction of the journal axis, there is a pumping effect during operation, so that the lubricant is transported into the contact area and thus improved conditions of friction compared to the prior art occur during operation. It was found that, thanks to the invention, it is even possible to leave the area of mixed friction (Stribeck curve), so that the generation of noise is further reduced as a result.

Provision can preferably be made for the contact region to be arranged on a convexly protruding, annular contact projection which is arranged on the end face of the pin and/or the bearing surface. The contact projection, also referred to as a bearing projection, can be designed as an annular projection or annular bead running coaxially around the pin axis and having the annular contact area in its area protruding axially from the pin or the bearing surface at the end. The outside diameter of the contact projection is preferably smaller than the pin diameter. The contact projection can advantageously be implemented with little effort, it being possible for the radial width of the annular contact area to be adjusted.

The contact projection can preferably be formed in one piece with the pin or the bearing surface, for example in a solid forming process such as cold extrusion or the like. As a result, the contact projection can be integrally formed on or in. This enables rational manufacture and assembly.

Provision can be made for the contact projection to have an annular bead with an arcuate annular cross section. For example, the annular bead can have a toroidal configuration in sections. The circumferential contact area lies in an axial tangential surface adjoining the arc of the rounded ring cross-section. The radial hoop width of the contact area can be practically dictated by the local radius of the hoop cross-section, with a smaller radius producing a radially narrower hoop contact and a larger radius producing a wider hoop contact. The arcuate rounding has the advantage that the notch effect of the contact projection can be reduced so that no plastic deformation occurs, which increases the service life and smooth running.

In the aforementioned arcuate ring cross-section, it is advantageous that in a section along the pin axis through a pin that has a contact projection or through a bearing surface that has a contact projection, the axial cut edge has a continuously differentiable profile at each point. The section is made radially through the bearing so that the axis of the journal lies in the plane of the section. Due to the continuously differentiable profile at each point, an arcuately curved cross section of the contact projection and the connection of the contact projection to the respective end face of the pin or the bearing surface is realized, which has no sharp edges. As a result, undesired material stresses and notch effects can be effectively reduced in an advantageous manner.

The ring cross-section preferably has a larger radius radially on the inside, ie on the side facing the pin axis and forming the lubrication pocket, than the radially outer section of the ring cross-section. In other words, the radius decreases from the inside to the outside in the radial direction. The cross-section of the ring is preferably half-tear-shaped. Thanks to this design, a loss of lubricant from the lubricating pocket can be reduced.

Outside of the contact area, or outside of the contact projection, the pin and/or the bearing surface can be designed to be planar or flat at least in sections, at least essentially.

The axial contact surface on the bearing surface or the end face of the journal, which the annular contact area according to the invention of the journal or the bearing surface contacts axially in the bearing contact, can preferably be flat.

The contact projection can preferably be formed in one piece. This allows an integral design to be created with the spigot or bearing surface. The one-piece molding can be done by means of common forming methods, for example by means of plastic forming such as pressing or the like, which enables rational manufacture and assembly.

Provision can preferably be made for the spider and/or the joint fork to be designed as a solid metal formed part. The main body of the spider and the joint forks is preferably made of steel or stainless steel by solid forming, for example by cold forming such as cold extrusion or the like, or by hot forming such as forging or the like from a one-piece blank by plastic forming. This creates a high-strength material structure, which enables a compact design with high resilience. A particular advantage of the invention is that the contact area, in particular a contact projection, can be provided with little effort, with little wear and tear and with dimensional stability.

It is preferably possible for the journal bearing to be in the form of a roller bearing. The rolling bearing is a radial bearing, for example a needle bearing, in which the rolling elements can roll between rolling element raceways on the outside of the journal and on the inside in the bearing bore of the arm. Such roller bearings are smooth-running, have little play and are durable. The rolling bearing can include a cage that accommodates the rolling elements and keeps them at a distance from one another. However, it is also conceivable and possible to use roller bearings without a cage.

The rolling element raceways can be formed directly on the outer surface of a journal and inside the bearing bore of the arm of the yoke.

An advantageous development can provide that the journal bearing has an outer sleeve which is fixed in the joint yoke and has the bearing surface. The outer sleeve can be firmly fixed in a bearing bore in an arm, for example by being pressed in, and preferably has the outer rolling element raceway on its inside. The outer sleeve can be pot-shaped with a hollow-cylindrical sleeve body which is at least partially closed axially on one side by a pot base which has the bearing surface on its inside. As a result, the end face of the pin plunging into the outer sleeve is axially opposite to the bearing surface formed on the inside of the bottom of the pot.

The outer sleeve can be efficiently manufactured as a pressed part, preferably as a pressed molded part, for example as a sheet metal cold pressed part made of steel, preferably of a rolling bearing steel that is well suited for use in the rolling bearing. The outer sleeve can be continuously or partially hardened and pressed into the arm of the joint yoke for fixation.

The bottom of the cup of the outer sleeve can be flat in the area of the bearing surface, which makes axial contact with an annular contact area arranged on the journal in the bearing contact.

An advantageous embodiment can provide that a contact projection is formed in one piece with the outer sleeve. For this purpose, the bearing surface arranged on the inside of the pot base can be shaped accordingly, for example a cone protruding axially inwards into the sleeve body have a tact advantage. The contact projection can preferably be molded in plastically, for example by arching or pressing in the bottom of the pot. If necessary, the outer sleeve can be hardened at least in the area of the contact projection, as a result of which the operating properties can be improved.

It is possible for the outer sleeve to be designed to be axially elastic. The bottom of the pot can preferably be designed to be spring-elastic relative to the sleeve body. As a result, the bearing surface can be elastically prestressed in the axial direction against the end face of the journal, so that the contact area according to the invention is axially prestressed in the bearing contact. The preload ensures that the bearing contact is maintained and that it runs very smoothly. Thanks to the ring contact according to the invention, unwanted noise can be largely avoided.

The inner rolling element raceway can be formed directly on the outside of the journal. It is also possible for an inner sleeve, which has the rolling element raceway, to be attached to the pin. As explained above for the outer sleeve, this can be made of steel, preferably made of roller bearing steel, for example as a pressed molded part, and fixed on the journal by pressing. As a result, the freedom of design of the rolling bearing is expanded and the bearing properties can be optimized.

The annular contact area according to the invention can be formed directly on the pin. It is also possible for an inner sleeve, which has a contact projection, to be attached to a pin. For this purpose, the inner sleeve, similar to that explained above for the outer sleeve, can be pot-shaped and pressed onto the pin with the hollow-cylindrical sleeve body. The contact projection is arranged on the end face of the pot base, directed axially outwards. As also described for the outer sleeve, the contact projection can preferably be molded in or on in one piece plastically, for example by pressing or other forming processes. To improve the operating properties, the inner sleeve can also be hardened, preferably in the area of the rolling body track and the contact area.

To realize an axial preload of the bearing, it is also possible for the inner sleeve to be designed to be axially elastic. As explained above for the outer sleeve, the bottom of the pot can preferably be designed to be axially resilient relative to the sleeve body. As a result, the contact area and the bearing surface can be elastically prestressed against one another in the axial direction in the bearing contact. For example, an annular projection according to the invention formed on the inner sleeve can be prestressed against the corresponding bearing surface on the joint yoke, or vice versa an annular projection arranged on the bearing surface of the joint yoke from the outside against the bottom of the pot. The preload ensures that the bearing contact is maintained and that it runs very smoothly. Thanks to the ring contact according to the invention, unwanted noise can be largely avoided.

The features and configurations described above can be implemented individually or in combination with one another.

A universal joint for a universal joint, with two pairs of pins arranged at right angles to one another, on the front side of which a protruding contact projection is arranged, which has an axial contact area, is designed according to the invention as described above. Such a universal joint makes it possible, in particular, to acoustically optimize existing joint constructions with little structural and manufacturing effort.

In the case of a steering shaft for a motor vehicle steering system, comprising at least two partial shafts which are connected to one another in a torque-locking, articulated manner via a universal joint, it is provided according to the invention that the universal joint is designed as described above.

In a steering system for a motor vehicle comprising a steering column with a rotatably mounted steering spindle which is articulated in a torque-locking manner to a steering shaft via a universal joint, the invention provides that the universal joint be designed as described above.

Due to the fact that the lowest possible noise development under all operating conditions is a decisive criterion for a steering shaft and a steering system of a motor vehicle, the acoustic optimization made possible by the invention is particularly advantageous.

character list

• 1 eine schematische perspektivische Ansicht einer Lenkwelle,
• 2 eine vergrößerte, teilweise auseinander gezogene Ansicht eines erfindungsgemäßen Kreuzgelenks der Lenkwelle gemäß 1,
• 3 einen Schnitt durch das Kreuzgelenk gemäß 2 entlang der Zapfenachsen,
• 4 eine vergrößerte Detaildarstellung von 3 im Bereich eines Zapfenlagers.

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 shaft,
• 2 12 is an enlarged, partially exploded view of a universal joint of the steering shaft according to the invention 1 ,
• 3 according to a section through the universal joint 2 along the pivot axes,
• 4 an enlarged detail view of 3 in the area of a journal bearing.

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 steering shaft 1, specifically an intermediate shaft, which is designed to be variable in length in the direction of its longitudinal axis L, with an inner shaft 11 that dips into an outer shaft 12 in a telescoping manner in the longitudinal direction and in a torque-locking manner.

A universal joint 2 according to the invention, also referred to as joint 2 for short, is attached to each end of the steering shaft 1 . Each joint 2 has two joint forks 21 of identical construction. The attachment of one yoke 21 to the inner shaft 11 or the outer shaft 12 of the shaft 1 is enlarged in 2 shown. The other joint yoke 21 has connecting means 23 for the non-rotatable connection to a further steering shaft, not shown here, for example a further partial shaft, a steering spindle or a steering gear, which is angled relative to the longitudinal axis L of the steering shaft 1 .

A joint yoke 21 attached to the shaft 1 has two arms 22 which extend in the direction of the longitudinal axis L and are radially opposite one another with respect to the longitudinal axis L.

Each joint 2 has a universal joint 3 which has two pairs of pins 31 which are arranged at right angles to one another and which each extend on a pin axis Z. In 3 a section through the universal joint 3 in the sectional plane spanned by the two pin axes Z is shown.

The two pins 31 of a pair of pins formed on the same pin axis Z are rotatably mounted about the pin axis Z in mutually opposite arms 22 of the joint yoke 21 in a bearing bore 24 in a roller bearing designed as a needle bearing 4 .

The needle bearing 4 embodied as a radial bearing comprises a pot-shaped outer sleeve 41 which has a hollow-cylindrical sleeve body 42 which is closed at the end by a pot bottom 43 . The sleeve body 42 is fixed in the bearing bore 24 in the arm 22 . Between the outer sleeve 41 and the pin 3 needles 44 are arranged as rolling elements, which can be rolled coaxially around the pin axis Z circumferentially between rolling element raceways on the inside of the sleeve body 42 and the outside of the pin 31 .

In 2 one outer sleeve 41 is shown schematically exploded in the direction of the pin axis Z, so that the view of the end face of the pin 31 is clear.

The outer sleeve 41 has a planar, i.e. level, bearing surface 45 on its inner side of the pot base 43, which is directed axially toward the pin 31.

On its end face directed axially towards the pot bottom 43, the pin 31 has an annular contact projection 32 according to the invention, which is arranged coaxially with the pin axis Z and protrudes axially in a bead-like manner. According to the invention, the contact projection 32 with an annular contact area 5 running coaxially around the pin axis Z slides axially in bearing contact against the bearing surface 45 of the pot bottom 43 .

The contact projection 32 is toroidal and has an arcuately curved annular cross section, which merges into the end face of the pin 31 with a likewise arcuate cross-sectional contour. In 4 It can be clearly seen that the axial cutting edge over the end face in the area of the contact projection 32 has a profile that can be continuously differentiated at every point.

The pot base 43 can be resiliently connected to the sleeve body 42 in the direction of the pin axis Z via a bead 46 . As a result, the contact projection 23 and the bearing surface 45 in the bearing contact of the contact area 5 can be axially elastically prestressed against one another.

The bearing surface 45 and the end face of the journal 31 are at an axial distance from one another centrally in the area of the journal axis Z, so that a lubricant pocket 6 is formed which is coaxially surrounded by the contact projection 32 and is preferably filled with a supply of lubricant, for example lubricating grease.

Reference List

1

steering shaft

11

inner shaft

12

outer shaft

2

universal joint

21

articulated fork

22

poor

23

contact protrusion

24

bearing bore

3

universal joint

31

cones

32

contact protrusion

4

needle bearing

41

outer sleeve

42

sleeve body

43

pot bottom

44

needle

45

storage area

46

bead

5

contact area

6

lube bag

L

longitudinal axis

Z

pivot axis

QUOTES INCLUDED IN DESCRIPTION

This list of the 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 102014116271 A1 [0004, 0005]
• DE 69210205 T2 [0005]

Claims (15)

Universal joint (2) for a steering shaft (1) of a motor vehicle, comprising a universal joint (3) with two pairs of pins (31) arranged at right angles to one another and two joint forks (21) each with two arms (22) lying opposite one another in pairs, in which a journal (31) is rotatably mounted in a journal bearing (4) about a journal axis (Z), and wherein the end face of a journal (31) makes axial contact with an axial bearing surface (45) arranged on the arm (21) in a contact area, which is smaller than the cross-section of the end face of the pin, characterized in that the contact area (5) is designed to run coaxially in the form of a ring. universal joint after claim 1 , characterized in that a central lubricant pocket (6) is arranged in the journal (31) and/or the bearing surface (45). Universal joint according to one of the preceding claims, characterized in that the contact area (5) is arranged on a convexly projecting, annular contact projection (32) which is arranged on the end face of the journal (32) and/or the bearing surface (45). universal joint after claim 3 , characterized in that the contact projection (32) has an annular bead with an arcuate ring cross-section. Universal joint according to any of the preceding claims 3 or 4 , characterized in that in a section along the pin axis (Z) through a pin (31) having a contact projection (32) or through a bearing surface (45) having a contact projection, the axial cutting edge is continuous at each point has a differentiable course. Universal joint according to any of the preceding claims 3 until 5 , characterized in that the contact projection (32) is integrally formed. Universal joint according to one of the preceding claims, characterized in that the universal joint (3) and/or the joint fork (22) is designed as a solid metal formed part. Universal joint according to one of the preceding claims, characterized in that the pivot bearing (4) is designed as a roller bearing. Universal joint according to one of the preceding claims, characterized in that the journal bearing (4) has an outer sleeve (41) which is fixed in the joint yoke and has the bearing surface (45). universal joint after claim 9 , characterized in that the outer sleeve (41) comprises a pressing part. Universal joint according to any of the preceding claims 9 until 10 , characterized in that a contact projection is formed integrally with the outer sleeve (41). Universal joint according to one of the preceding claims, characterized in that an inner sleeve which has a contact projection (32) is fitted on a pin (31). Steering shaft (1) for a motor vehicle steering system, comprising at least two partial shafts which are connected to one another in a torque-locking manner in an articulated manner via a universal joint (2), characterized in that the universal joint (2) according to one of Claims 1 until 12 is trained. Steering system for a motor vehicle, comprising a steering column with a rotatably mounted steering spindle which is connected in a torque-locking manner to a steering shaft (1) via a universal joint (2), characterized in that the universal joint (2) according to one of Claims 1 until 12 is trained. Universal joint (3) for a universal joint (2), with two pairs of pins (31) arranged at right angles to one another, on the front side of which a protruding contact projection (32) is arranged, which has an axial contact area (5), characterized in that the contact area (5) is formed coaxially annularly circumferentially.

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