EP3223977A1

EP3223977A1 - Method for producing a profiled hollow shaft for a telescopic steering shaft and telescopic steering shaft

Info

Publication number: EP3223977A1
Application number: EP15771894.1A
Authority: EP
Inventors: Herbert Müntener; Werner GSTACH
Original assignee: ThyssenKrupp AG; ThyssenKrupp Presta AG
Current assignee: ThyssenKrupp AG; ThyssenKrupp Presta AG
Priority date: 2014-11-26
Filing date: 2015-09-22
Publication date: 2017-10-04
Also published as: US10634184B2; CN107000014A; WO2016082969A1; DE102014017407A1; US20170328400A1

Abstract

The present invention relates to a method for producing a profiled hollow shaft (20, 30) for a telescopic steering shaft (10) of a motor vehicle, said method comprising the provision of a hollow shaft to be machined and of a roller forming head (50, 501) comprising at least one roller (52, 521), wherein a groove (22, 32) is produced in the hollow shaft (20, 30) by moving the hollow shaft (20, 30) in relation to the roller forming head (50, 501). In order to provide an improved and less expensive method for producing a profiled hollow shaft for a telescopic steering shaft of a motor vehicle, it is proposed according to the invention that, to form a groove (22, 32), the hollow shaft (20, 30) is moved in relation to the roller forming head (50, 501) exclusively in the direction of the longitudinal axis of the hollow shaft (20, 30). The invention likewise relates to a steering shaft (10) having rolling body raceways (22, 32) produced according to the invention.

Description

Method for producing a profiled hollow shaft for a telescopic steering shaft and telescopic steering shaft

State of the art

The invention relates to a method for producing a profiled hollow shaft for a telescopic steering shaft of a motor vehicle, comprising providing a hollow shaft to be machined and at least one roller having rolling head, wherein the hollow shaft is moved relative to the rolling head to produce a groove in the hollow shaft , according to the preamble of claim 1. Furthermore, the invention relates to a steering shaft for a motor vehicle according to the preamble of claim 9. Telescopic steering shafts in motor vehicles allow adjustability

the steering column, wherein the steering wheel position can be adjusted in the longitudinal direction of the steering shaft. In addition, the steering shaft in the event of a crash can be pushed together, thereby effectively preventing the steering column penetrates further into the interior of the passenger compartment and leads to injury to the occupants. This is generally achieved by the provision of two mutually telescopable shafts or hollow shafts, which together form a steering shaft which can be correspondingly shortened or extended by telescoping relative movement of the shafts.

US 8,460,116 discloses a roller thrust shaft consisting of an inner and outer shaft between which linear ball guides are arranged. To provide the outer raceways, the outer shaft of the roller thrust shaft is formed from circular ring segments. This results in a relatively complicated structure of a plurality of individual components. DE 10 2008 041 155 A1 proposes an outer tube for a telescopic steering shaft, which surrounds an inner shaft as the outer shaft. In the radial gap between the waves balls are arranged. These balls roll during telescoping parallel to the longitudinal axis of the steering shaft on the outside of the inner shaft and the inside of the outer shaft and thereby ensure a smooth adjustment. In the outer tube for this purpose axially extending in the longitudinal direction, groove-like ball raceways are formed with a part-circular cross-section. To form the ball tracks, the outer tube has a circumferentially varying wall thickness, whereby a relatively high production order wall for generating the Außenrohrquerschnittsgeometrie arises.

A similarly designed telescopic steering shaft is described in EP 1 693 579 A2. This likewise has balls which are arranged between the relatively telescopable shafts and which can be rolled in the direction of the longitudinal axis. In this embodiment, the inner and the outer shaft are provided with radially opposite, corresponding ball raceways. The inner shaft is formed as a solid forging and the outer shaft has a complex cross-sectional geometry similar to the above-mentioned DE 10 2008 041 155 A1.

For the production of a profiled hollow shaft, a method is known from CH 579 427 A5, in which a hollow shaft is rotated about a longitudinal axis during processing by a rolling head with annularly profiled rollers or rollers so that successive single rolling operations on one helical zone of the hollow shaft surface can be juxtaposed. As a result, profiled hollow shafts can be manufactured with high precision. However, the required rotational feed motion and thereby rapidly following, sudden single rolling operations make the known method technically complex, time-consuming and correspondingly costly and thus not suitable for the production of steering shafts.

A disadvantage of the known in the art telescopic steering shafts is the relatively high production costs for the formation of serving as ball or Wälzkörperlaufbahnen grooves. Starting from the known prior art, it is an object of the present invention to provide an improved and cheaper method for producing a profiled hollow shaft for a telescopic steering shaft of a motor vehicle.

This object is achieved by a method having the features of claim 1. Advantageous developments emerge from the subclaims.

Accordingly, a method for producing a profiled hollow shaft for a telescopic steering shaft of a motor vehicle is proposed, comprising providing a hollow shaft to be machined and a roller having at least one roller head, wherein for producing a groove in the hollow shaft, the hollow shaft is moved relative to the rolling head, wherein is provided according to the invention that for forming a groove a Be movement of the hollow shaft relative to the rolling head exclusively in the direction of the longitudinal axis of the hollow shaft.

A special feature of the method according to the invention is that it completely dispenses with a complicated rotational movement during the rolling process. A hollow shaft to be machined is moved by a rolling head in a purely linear feed movement, wherein at least one roller, preferably a plurality of rollers, acts mechanically on the outer jacket surface of the hollow shaft. By a roller thereby in each case a longitudinal direction parallel to the longitudinal axis of the hollow shaft extending groove-like recess is formed.

An advantage of the invention is that there is no need for a combined rotational feed movement of the workpiece as compared to the forming methods known in the prior art for producing profiled hollow shafts, whereby the production equipment can be less complex. In addition, significantly reduced cycle times are achieved, which allows a particularly efficient production. Only the resulting high productivity makes the use of a rolling process in the production of telescopic steering shafts for the automotive industry economically suitable.

When creating a groove, material is displaced from a peripheral region having an output radius to a peripheral region having a smaller radius than the starting radius. The formed groove serves as a form element for torque transmission of a rotary movement of the telescopic steering shaft.

To form a telescopic steering shaft, an outer hollow shaft and an inner hollow shaft arranged telescopically therein with mutually corresponding grooves is arranged. In this case, the groove in the inner jacket surface of an outer hollow shaft is formed by the region of the hollow shaft which is not displaced inward by means of the method according to the invention. In contrast, the groove is formed in an outer shell surface of an inner hollow shaft by the inwardly displaced during rolling of the hollow shaft.

The base surface of the groove or groove base surface is understood to be the surface region spanned by the edge of the groove which, in the case of the inner hollow shaft, has not been displaced during the forming and correspondingly forms the largest radius region on both sides of the respective groove. In other words, it is the area of the free opening cross section of the groove. In the case of the outer hollow shaft, the base surface of the groove is clamped by the edge of the groove, which is formed by the smallest radius region on both sides of the respective groove. The core of a production plant for carrying out the method according to the invention is the burnishing head, which has at least one, as a rule, a plurality of rollers. The rollers are mounted on axes of rotation transversely to the machining direction, in which a hollow shaft to be machined is moved in the direction of its longitudinal axis linearly past the rollers. With their outer circumference, the rollers in a roller burnishing head according to the invention can roll on the outer jacket surface of a hollow shaft introduced into the rolling head exclusively in the direction of the longitudinal axis. With their designed as a rolling profile outer circumference, the rollers are radially in the open cross-section of a processing passage. If a hollow-shaft blank in the form of a pipe section-for example a round or polygonal pipe-is linearly fed longitudinally into the machining passage, then rollers roll with their rolling profile exclusively in the direction of the longitudinal axis on the hollow shaft. The radial feed of the rollers, which indicates how far the roller burnishing profile protrudes into the machining passage, determines how deep according to the invention in the longitudinal direction grooves are formed when passing the rollers from the outside into the hollow shaft.

The grooves are formed in the method according to the invention by means of the rolling head in a cold deformation in the hollow shaft. In contrast to the prior art, in which a groove is formed by a plurality of sudden single rolling operations in the radial and axial directions, according to the invention, a continuous rolling process takes place exclusively in the longitudinal direction. Depending on the material and the material thickness of the hollow shaft and the radial depth of the profiling, ie the grooves, it is conceivable that the nominal size of the hollow shaft profile is achieved in a single pass through the rolling head, for example, in a forward stroke in the longitudinal direction. As a result, particularly short cycle times can be realized. It is also possible to achieve the final dimension of the profiling in several passes, wherein between the individual passes in each case a radial delivery of the rollers takes place. For example, the profiling can be brought in a counter to the longitudinal direction to the final dimension in a following on the said advance stroke return stroke of the hollow shaft. Preferably, the rollers with a fixed axis of rotation whose distance is not variable, arranged in the rolling head. As a result, the system costs are significantly reduced, since no complicated delivery and adjustment movement of the roller axes must be displayed. In the case that the representation of the hollow shaft is to be made with several steps with different delivery of the rollers, several different rolling heads can be used, each with fixed mutually different, but per rolling head set, center distances of the axes of rotation of the rollers. It is also conceivable and possible to provide different roller contours in the different rolling heads for the formation of the grooves in order to influence the forming targeted. The method preferably provides that the generation of the at least one groove with a length on the hollow shaft is effected by a forward stroke of the hollow shaft passing along the length relative to the rolling head, wherein the roller of the rolling head unwinds continuously in the longitudinal direction on the hollow shaft. With a continuous stroke movement a linear movement in a stroke direction without reversal of movement is called, preferably without movement interruption. Accordingly, the formation of an entire groove in an uninterrupted linear motion relative to the rollers over the entire length of the groove. The linear movement can be done at a constant speed or with a given velocity profile. In contrast to the prior art, which provides several discontinuous individual movements, according to the invention a groove can be formed in a single, continuous linear movement. The delivery of the rollers in the burnishing head can be carried out beforehand correspondingly to a final dimension, wherein the cross section of the processing passage set before the first preliminary stroke when the hollow shaft is inserted corresponds to the desired profiling. Preferably, the delivery of the rollers in the burnishing head is fixed, that is, the rolling head has no adjustment mechanism, with the aid of the distance of the roller axes can be changed. In the simplest case, the axes on which the rollers are mounted, embedded in recesses in the rolling head.

It is preferably provided that after a Vorhubbewegung the hollow shaft is retracted by a continuous return stroke relative to the rolling head. The grooves extend in hollow shafts for use in steering shafts from one end over a predetermined groove length which is smaller than the wavelength, i. the respective total length of the inner or outer hollow shaft. The therefore required after a Vorhubbewegung for removing a hollow shaft from the rolling head Rückhub- or retraction movement is like the Vorhubbewegung also preferably carried out in a continuous continuous linear motion. If the final dimension of the profiling has already been set in the preliminary stroke, the rollers remain in their radial infeed position, so that during the return stroke due to the elastic springback of the hollow shaft in the radial direction, a rolling with low infeed is performed, whereby the dimensional accuracy and the surface quality of the rolling th grooves is improved.

The indentation of a groove in a continuous working stroke - for example, the forward or return stroke - has the advantage that particularly short cycle times can be realized, which benefits a rational production of steering columns. In addition, due to the exclusively continuous longitudinal processing, a micro- Skopische surface structure are generated, which is optimally adapted to the relative longitudinal displacement of inner and outer shaft when telescoping a steering column. For example, the groove surface in the longitudinal direction is particularly smooth, which improves the sliding behavior of the shafts during adjustment and at the minimum displacements occurring during vehicle operation due to the elasticities of the motor vehicle.

The linear relative movement between the hollow shaft and the roller burnishing head can be realized with little effort in terms of manufacturing technology. It is possible, for example, to clamp a hollow-shaft blank onto a motor-driven linear feed unit which, in the longitudinal direction, pushes the hollow shaft through the rollers in a feed stroke into the machining passage of the roller burnishing head. By moving the feed unit counter to the longitudinal direction, a return stroke movement takes place with which the hollow shaft is pulled out of the roller burnishing head. Alternatively or additionally, it is possible to rotatably drive the rollers of the roller burnishing head. When inserted into the machining passage, a hollow shaft is caught by the rotating rollers and - when the direction of rotation corresponds to a circumferential movement in the longitudinal direction of the hollow shaft - conveyed in a Vorhubbewegung between the rollers. The formed on the outer circumference of the rollers profile cross-section is formed in the outer periphery of the hollow shaft. By reversing the direction of rotation against the longitudinal direction, the already completely or partially profiled hollow shaft can be conveyed out of the roller burnishing head in a return stroke movement.

A possible embodiment of the method according to the invention provides that a profile mandrel is inserted into the hollow shaft and is moved together with the hollow shaft relative to the rolling head during the movement of the hollow shaft. The profile mandrel forms an abutment with respect to the forces acting on the hollow shaft from the outside by the rollers in the formation of the grooves. Due to the joint movement of the hollow shaft and profile mandrel, no relative movement takes place in the longitudinal direction between the hollow shaft and profile mandrel during the indentation of the grooves through the rolling head, whereby friction losses are minimized.

On its outer circumference of the profile mandrel is formed with a cross-sectional contour, which serves as a negative counter-mold or die for the grooved during radially radially from the outside into the wall of the hollow shaft groove profile. In the production of an outer hollow shaft, the material is rolled into the outer profile of the profile mandrel, so that the inside of the outer hollow shaft is cold-deformed according to the groove geometry predetermined by the profile mandrel and receives a groove profile for positive reception of an inner hollow shaft. The groove profile formed on the outside of an inner shaft is predetermined by the working profile on the outer circumference of the rollers. By cold deformation, the groove profile is introduced as an impression of the roller profile in the longitudinal direction in the outside of the hollow profile.

An alternative embodiment of the method according to the invention provides that a hollow shaft for generating at least one groove is passed empty by the rolling head on the rollers. In this context, by "empty" is meant that in the open passage cross section of a hollow shaft to be profiled no mandrel or other body is arranged, which would be suitable for supporting the wall of the hollow shaft during the cold forming in the production of the grooves or the formation of the grooves It has surprisingly been found that both the production of grooves in the outer surface of an inner hollow shaft and in the inner surface of an outer hollow shaft with the required properties can take place without using a profile mandrel Way in hollow sections are introduced with a diameter smaller than 30 mm, based on the outer diameter of an inner hollow profile or the inner diameter of an outer hollow profile.

A particularly preferred embodiment of the method according to the invention provides that the steering shaft is linearly roller-mounted in the direction of the longitudinal axis, wherein a groove is formed in a hollow shaft as Wälzkörperlaufbahn for receiving at least one rollable rolling element. A linearly roller-mounted steering shaft is understood to mean a design in which rolling bodies, for example balls, are arranged between the inner and outer hollow shafts, which roll on the mutually guided hollow shafts in the case of a telescopic movement on the peripheral surfaces facing each other. Examples of such roller bearing mounted steering shafts are mentioned in the prior art described above, for example in EP 1 693 579 A2 or DE 10 2008 041 155 A1.

For formation as a rolling body raceway, the groove is shaped in such a way that a rolling body, for example a cylindrical roller or a ball, can be inserted, which can roll in the groove along the longitudinal axis, more than one-eighth of the largest diameter of the rolling element protrudes beyond the Nutbasisfläche, ie from the surface of the free slot opening. Especially preferably, the groove is produced such that it is designed as a raceway for a rolling element in the form of a sphere. This means that the groove is shaped so that a ball can be inserted along the

Rolling longitudinal axis in the groove can move out and more than one-eighth of the ball diameter protrudes beyond the Nutbasisfläche. Preferably, the rolling element protrudes - cylin- roller or ball - with more than half of the largest diameter out of Nutbasisfläche out, in other words by more than half out of the groove.

In linearly roller-mounted steering shafts serve on the inner surface of the outer hollow shaft and / or the outer surface of the inner hollow shaft longitudinally extending grooves as Wälzkörperlaufbahnen, hereinafter also synonymous referred to as ball races, in which roll the balls or other rolling elements during telescoping. High demands are placed on the accuracy and surface quality of the profile geometry of such ball races as well as of the cross-sectional geometry of the telescoping shafts that can be telescoped into one steering column. At the same time, a rational and cost-efficient production method is required. Thanks to the method according to the invention for the first time grooves can be introduced into hollow shafts, which are suitable as ball raceways and optimally meet the aforementioned requirements. It is particularly noteworthy that the Wälzkörperlaufbahnen can be realized in the above-described embodiment of the method NEN, which provides the rolling of an empty hollow shaft, without the use of an inserted into the hollow shaft profile mandrel. In particular for the manufacture of roller-mounted steering columns with a smaller diameter, it brings production engineering, functional and economic advantages to produce the inner and the outer hollow shaft according to this embodiment of the method according to the invention.

Preferably, a hollow shaft is formed as an inner hollow shaft and has on its outer circumference at least one Wälzkörperlaufbahn, which is introduced from the outside of a rolling head, the rollers having a convex rolling profile corresponding to the negative Wälzkörperlaufbahnquerschnitt. Due to the rolling profile of the rollers, which is formed during rolling in direct contact with the surface of the hollow shaft, the cross-sectional geometry of the rolling body groove forming groove can be produced with high precision.

A further preferred embodiment of the invention provides that a hollow shaft is formed as an outer shaft and has on its inner circumference at least one Wälzkörperlaufbahn which is introduced from the outside of a rolling head, the rollers having a concave Rollierprofil following the Wälzkörperlaufbahnquerschnitt. The generation of the grooves serving as ball tracks in the inner surface of the outer hollow profile takes place by the wall being deformed radially inwards by the edges of the concave rolling profile of the roller pressed from the outside against the hollow shaft. As a result, the lying on the inside ball track is formed from the outside of the hollow shaft indirectly, without the role in the machining direct contact with the surface of the Ball track has. It has been found that, taking into account the predetermined parameters such as diameter, wall thickness, cross-sectional shape and material of the hollow shaft, the cross-sectional geometry of a ball track can also be rationally and precisely realized by the method according to the invention in the indirect molding.

It is particularly advantageous that at least one roller has a Gothic profile in cross-section. A Gothic profile, also referred to as pointed arch profile, is characterized by two arcuate sections which are inclined relative to each other at an angle, so that a tip or a kink is formed. This is achieved in that the first center point of the first arcuate section is offset relative to the second center point of the second arcuate section by a predetermined distance in the direction of the opposite arcuate section. The gothic profile is mirror-symmetrical to a mirror axis passing through the top of the cross-section; Correspondingly, the abovementioned first and second center points are mirror-symmetrical, each with its half distance on both sides to said mirror axis. In the case of a convex profile cross-section, the tip lies on the outermost circumference of the roller, and in the case of a groove formed by the roller directly into a surface of an (inner) hollow shaft corresponding to the lowest point of the groove. In a concave profile cross section of the roller, the tip is in the innermost circumference of the roller cross section, which transforms the wall of an (outer) hollow shaft, so that on the inside of the hollow shaft, which faces away from the roller, a Wälzkörperlaufbahn is formed with gothic profile cross-section. The fact that the radius of the arches of the gothic profile is dimensioned larger than the diameter of the balls, creates a point contact between the ball track and a ball in two places. As a result, particularly good running properties are achieved with precise guidance, uniform load distribution and high rigidity.

It is preferably provided that the generation of the total number of a plurality of grooves present in the hollow shaft takes place in a common working step with a continuous forward stroke movement. The total number means all grooves that are formed in a hollow shaft.

Preferably, a separate roller in the rolling head is provided for each groove in the hollow shaft, wherein the rollers for generating the grooves roll on the hollow shaft simultaneously. In this way it is possible to produce a plurality of grooves in the direction of the longitudinal axis of the hollow shaft in the hollow shaft in one operation. In this way, by means of an axial relative movement of the hollow shaft relative to the rollers of the rolling head, the entire forming process for producing the grooves in the hollow shaft can be performed. This results in a significant time savings, so compared to conventional manufacturing processes significantly shorter cycle times for profiling the hollow shaft or for forming the grooves in the hollow shaft are possible.

In addition, a simultaneous formation of the grooves to be produced in the hollow shaft with a symmetrical arrangement of the grooves in the hollow shaft lead to a substantially symmetrical force of the rollers of the rolling head in the radial direction of the hollow shaft. This is particularly advantageous for the design of the rolling head. A symmetrical distribution of forces leads to lower demands on the supporting effect of the individual components of the roller burnishing head. In addition, the symmetrical force curve significantly reduces the torques arising in a bearing of the roller burnishing head, which can lead to a reduction in the design and manufacturing costs of the rolling head.

Furthermore, a symmetrical force also has a positive effect on the properties of the profiled hollow shaft. Thus, the hollow shaft undergoes uniform bending operations during cold forming, so that uniform grooves are formed on the hollow shaft. The result is a symmetrical rotation body with a homogeneous material distribution.

The provision of a separate roller in the rolling head for each groove to be produced in the hollow shaft thus makes a new angular positioning of the hollow shaft relative to the rolling head superfluous. As a result, on the one hand, the processing time for producing a profiled hollow shaft and, on the other hand, the complexity of the method for producing the profiled hollow shaft can be reduced. The object of the present invention is also achieved by a steering shaft with the features of claim 9. Advantageous developments emerge from the dependent claims.

Accordingly, a steering shaft for a motor vehicle is proposed, comprising an inner hollow shaft and an outer hollow shaft, which are arranged coaxially to each other and telescopically telescoped, wherein the inner hollow shaft and the outer hollow shaft in the direction of the longitudinal axis extending rolling body tracks, each radially between lie opposite the waves, wherein between the inner hollow shaft and the outer hollow shaft at least one rolling element is arranged, which rolls on the radially opposite Wälzkörperlaufbahnen, wherein at least one of the two shafts of the steering shaft is produced by the method described above.

This makes it possible, a linear roller bearing mounted steering shaft for a motor vehicle with lower production costs and shorter cycle times, and thus more cost-effective than in the state to produce the technique. In this case, the hollow shafts with rolling body raceways produced by the method according to the invention are distinguished by properties that are particularly advantageous for telescoping, which are described above. Particularly preferably, at least one of the rolling element raceways of the inner hollow shaft and / or the outer hollow shaft seen in cross section on a Gothic profile. This form, which is also known as an ogival profile, has two arches, preferably circular arcs, which merge into one another at an angled tip. Due to the fact that the radius of the arches of the Gothic profile is greater than the diameter of the balls used as rolling elements, there is a point contact between the ball track (rolling element track) and a ball at two points. As a result, particularly good running properties are achieved with precise guidance, uniform load distribution and high rigidity. By means of the method according to the invention, rolling element raceways can be formed both into the outer surface of an inner hollow shaft and into the inner surface of an outer hollow shaft.

A preferred embodiment of the invention provides that at least one rolling element is a ball, which is in contact with at least one of the rolling element rolling tracks at two circumferential points, at a pressure angle φ which lies in the range between 70 and 110 °.

Due to the configuration of the profile of the rolling body raceway, for example as gothic profile as described above, a ball is only in two points in contact with the surface of the respective rolling body raceway. As a result, the rolling friction is minimized, which benefits easy adjustment when telescoping the steering column. In addition, so the wear is minimized. The specification of the pressure angle in the specified range is particularly favorable with regard to the distribution of the introduction of force into the rolling body raceway.

It is advantageous that a sleeve is arranged between the inner hollow shaft and the outer hollow shaft, wherein this sleeve receives the at least one rolling element. The sleeve forms a cage for the rolling elements, preferably a ball cage, in which one, usually a plurality of rolling elements, freely rotatable, but are held relative to the sleeve and each other in a defined position. This Wälzkörperkäfig ensures that the rolling elements are held captive between the hollow shafts. In addition, a plurality of rolling elements for a plurality of Wälzkörperlaufbahnen can be performed in the same position in the longitudinal direction, and a plurality of rolling elements are held within a Wälzkörperlaufbahn at a constant distance from one another in the longitudinal direction. The taking place by means of the sleeve positioning of the rolling elements relative to each other and to the Wälzkörperlaufbahnen ensures a optimal arrangement of the rolling elements at any time, with regard to the stability of the steering column, the introduction of force into the bearing and low friction.

In cross-section, the hollow shafts are preferably rotationally symmetrical, both with regard to their basic cross-sectional shape, and - particularly adapted to this cross-sectional basic shape - with respect to the arrangement of serving as Wälzkörperlaufbahnen grooves. For example, the hollow shafts may have a quadrangular, preferably square, cross-section, wherein four rolling element raceways may be arranged symmetrically on all four sides, or else two rolling element tracks symmetrically on opposite sides. Correspondingly, hollow shafts having a triangular basic shape can have three rolling body raceways; in a hexagonal basic shape, it is conceivable to provide two, three, four or six rolling element raceways in a mirror-symmetrical or rotationally symmetrical arrangement. Description of the drawings

Advantageous embodiments of the invention are explained in more detail below with reference to the drawings. 1 shows a schematic perspective view of a steering shaft,

FIG. 2 shows a part of a steering shaft according to FIG. 1 in disassembled state;

3 shows a cross-sectional view of a steering shaft according to the preceding figures,

FIG. 4 shows a detailed view of the sectional representation according to FIG. 3 in the region of a rolling body,

FIG. 5 shows a further detail view of the sectional view according to FIG. 3 with the rolling element taken out,

6 shows a schematic perspective view of a roller burnishing head, FIG. 7 shows a schematic perspective view of a roller burnishing head in a second embodiment,

Figure 8 is a schematic perspective view of the roller assembly of

Rolling head according to Figure 7,

FIG. 9 shows a cross-sectional view of the roller arrangement according to FIG. 7 in the area of the roller,

Figure 10 is a schematic perspective view of the roller assembly of

Rolling head according to Figure 6, FIG. 11 is a cross-sectional view of the roller arrangement according to FIG. 10 in the region of the rollers;

FIG. 12 shows a schematic view of a longitudinal section along the longitudinal axis of a roller burnishing head during a rolling process,

13 shows a cross-sectional view of a steering shaft in a second embodiment,

FIG. 14 shows a schematic sectional view of a roller burnishing head when inserting a hollow shaft,

FIG. 15 shows a schematic sectional view of the roller burnishing head according to FIG. 14 during a rolling process with a hollow shaft located therein during the preliminary stroke,

FIG. 16 shows a schematic sectional view of the roller burnishing head according to FIG. 15 during a rolling operation with a hollow shaft located therein during the return stroke.

Description of preferred embodiments

In the figures, preferred embodiments of the invention are shown, wherein subsequently the same parts always provided with the same reference numerals and therefore usually named or mentioned only once in each case.

FIG. 1 shows a perspective view of a schematically illustrated steering shaft 10, which has an outer hollow shaft 20 and an inner hollow shaft 30 which can be telescoped relative to one another in the direction of the longitudinal axis, that is to say in the longitudinal direction indicated by the double arrow.

The outer hollow shaft 20 has at its free end, which is remote with respect to the inner shaft 30 in the longitudinal direction, a fork 21, which forms part of a universal joint, with which the steering shaft 10 is connected in a torque-locking manner with the steering line. Accordingly, the inner hollow shaft 30 at its free end, which is remote with respect to the outer shaft 20 in the longitudinal direction, a fork 31, which forms part of another universal joint with which the steering shaft 10 is connected to the torque arm torque-fit. The hollow shafts 20 and 30 are preferably made of good cold-formable steel.

Figure 2 shows a part of the steering shaft 1 according to Figure 1 in an exploded view, in which the individual components are shown in disassembled state. representation it can be seen that the outer shaft 20 in its inner shaft 30 facing region, in which the inner hollow shaft 30 is telescopically inserted in the longitudinal direction, is profiled. The profiling of the outer shaft 20 includes grooves 22 which extend in the inner circumferential surface 23 of the outer shaft 20 in the longitudinal direction over a length A. The length A extends from the inner shaft 30 facing end over a portion of the outer shaft 20 which is smaller than the total length. The grooves 22 are formed with respect to the wall of the hollow shaft 20 outside opposite convex protruding bead-like formations 24 in the outer jacket surface 25. These formations 24 are bounded on both sides in the circumferential direction by regions 26 formed in a groove-like manner from the outside. In the illustrated embodiment, four grooves 22 are distributed uniformly over the circumference of the hollow shaft 20. The grooves 22 are formed as Wälzkörperlaufbahnen, or more specifically as ball raceways, as will be explained below.

The end portion of the inner hollow shaft 30, which faces the outer hollow shaft 20 and telescoping in this, as shown in Figure 1, is also profiled. The profiling comprises grooves 32 which extend from the insertable into the outer hollow shaft 20 in the outer end outer surface 33 of the hollow shaft 30 in the longitudinal direction over a length L. The length L extends over the portion of the inner hollow shaft 30 which is inserted in the outer hollow shaft 20 in the longitudinal direction.

From FIG. 2, in conjunction with the cross-sectional illustration in FIG. 3, it is readily apparent how rolling elements, namely balls 40, are arranged radially between the grooves 22 and 32. In each case a plurality of balls 40 are arranged in the longitudinal direction with one behind the other in the grooves 22 and 32. They are freely rotatable in a sleeve 80 designed as a ball cage 80 and held at a defined distance relative to one another. At the same time, the sleeve 80 ensures that circumferentially adjacent balls 40 each remain in the same position relative to the longitudinal direction.

The embodiment shown in Figure 3 shows a quadrangular, specifically a square base cross-section of the hollow shafts 20 and 30. The grooves 22 and 32 are arranged symmetrically in each case centrally in one side of the square.

A similar second embodiment is shown in FIG. 13 as shown in FIG. In contrast to the first embodiment, this only has a total of two rows of balls 40, which roll between an outer hollow shaft 201 and an inner hollow shaft 301 in grooves 22 and 32, which are symmetrically located on two opposite sides of the square. In FIGS. 4 and 5, a respective groove 22 and 32 from FIG. 3 are shown enlarged again. It can be seen that the grooves 22 and 32 each have a Gothic profile. This is formed by two circular arc sections 27 and 37, which meet at the groove bottom 28 and 38 at an angle, ie forming a peak analogous to a Gothic pointed arch.

The circular arc sections 27 and 37 each have a radius K1 and K2, where K1 = K2. The center radii M1 of K1 and M2 of K2 have a distance G from each other, wherein they are arranged mirror-symmetrically to a passing through the tip 28 mirror axis S. The amount of K1 and K2 is greater than the radius R of a ball 40 inserted between the grooves 22 and 32. As a result, each ball 40 abuts at exactly two contact points P1 and P2 at a groove 22 or 32, as shown in FIG. In this case, the amount of the pressure angle φ, which is included between the contact points P1 and P2 with respect to the ball center with radius R, preferably in the range between 70 to 1 10 °.

The groove 22 has a groove base surface 29, the groove 32 has a groove base surface 39. As clearly shown in Fig. 4, a ball 40 projects more than half of its diameter 2 * R across the respective groove base surface 29 and 32, respectively. Thus, for the grooves 22 and 32, the above definition of a rolling element raceway is fulfilled, i. they form ball raceways for the balls 40.

FIG. 6 shows a roller burnishing head 50 for producing an inner hollow shaft 30 described above. The rolling head 50 has four rollers 52, which are arranged rotationally symmetrically around a machining passage 51. The rollers 52 are each arranged at an angle of 90 °. Each roller 52 is rotatably mounted on a frame 56 of the roller burnishing head 50. The rolling head 501 shown in FIG. 7 for producing the outer hollow shaft 20 described above has an analogous construction to the rolling head 50 for producing the inner hollow shaft 30, with a machining passage 51 1, rollers 521 and a frame 561. FIGS. 7, 8 and 9 show a profile mandrel 60, which is arranged in the machining passage 51 1 of a roller burnishing head 501 in the middle of the four rollers 521. Between the profile mandrel 60 and the rollers 521, a gap is provided, so that the profile mandrel 60 along the Rollierachse, ie the longitudinal axis passing through the processing passage 51 1 longitudinal axis can be moved without the rollers 521 roll on the profile mandrel 60.

Figure 9 is an enlarged view of the profile mandrel 60 to take with projections 62, wherein between the profile mandrel 60 and the rollers 521, a gap is provided, which corresponds approximately to the profile of a hollow shaft to be produced by means of the Rollierkopfes 501.

FIG. 12 shows a section along the longitudinal axis of the machining situation illustrated in FIG. 10, wherein a hollow profile 30 for producing a groove 32 of length L is inserted between the rollers 52 by the amount of this length L.

Alternatively, the roller burnishing head 50 or 501 may also have one, two, three, six or more rollers 52 and 521, respectively, which are spaced apart from each other at a corresponding angle.

Figures 9 and 1 1 it can be seen that the rollers 52, 521 are profiled and have a roller center profile 53, 531 and a roll edge profile 54, 541.

To form a ball track, the roller center profile 53 has the shape of a convex Gothic profile. The diameter of the roller center profile 53 is greater than the diameter of the roller edge profile 54.

In the rollers 521, the roller center profile 531 is formed in the shape of a concave Gothic profile. The rollers 521 and the profiled mandrel 60 are arranged relative to one another such that a roller center profile 531 corresponds to a projection 62 of the profiled mandrel 60.

FIG. 9 shows a cross-section of a detailed view of a roller burnishing head 501, wherein the rollers 521 are in contact with an outer hollow shaft 20, which is pushed onto the profile mandrel 60. In this case, the outer hollow shaft 20 is cold rolled, so that the outer shaft 20 assumes the profile of the profile mandrel 60 on its inner circumferential surface and is formed on its outer circumferential surface 25 by the rollers 521 and in particular the roller profile.

Since the roller center profile 531 corresponds in cross section to the projection 62 of the profile mandrel 60, the material of the outer hollow shaft 20 is pressed by the roller center profile 531 onto the projection 62 of the profile mandrel 60. Accordingly, an inner hollow shaft 30 of a steering shaft 10 can be manufactured by means of a rolling head 50. A difference of the burnishing head 50 to the rolling head 501 is that the machining of a hollow profile, for example an inner hollow profile 30, can take place without the use of a profiled mandrel. For this purpose, a hollow profile 30 is empty, that is, without a counter tool is in the free passage, introduced into the processing passage 51 of the rolling head 50. For clarity, this is shown schematically in Figure 10, wherein only the rollers 52 are shown, and the remaining elements of the roller burnishing head 50 are omitted. The hollow profile 30 is pushed in the direction of arrow between the rollers 52, wherein the outer lateral surface 33 is cold-formed by the profile cross section of the rollers 52 to form grooves 32. The situation is again shown in cross-section in FIG.

An alternative embodiment of the method described with reference to the roller burnishing head 501 in FIGS. 7, 8 and 9 provides that no profile mandrel 60 is used. This means that an outer hollow profile 20 is cold cold-formed, as described above for the preparation of an inner hollow profile 30 when using a burnishing head 50. Especially with a relatively small hollow profile cross-section, it is possible to form suitable Wälzkörperlaufbahnen 22 in the inner shell surface by rolling from the outside Figures 14 to 16 show the sequence of movements of a Doppelhubbewegung for profiling an outer hollow shaft 20 by means of a Rollierkopfes 501st These are cross-sectional views, each showing two opposing rollers 521, wherein between the rollers 521, a profile mandrel 60 is arranged on soft an outer hollow shaft 20 is pushed.

FIG. 14 shows a forward stroke movement of an outer hollow shaft 20 together with the profile mandrel 60. The outer hollow shaft 20 is moved with the profile mandrel 60 relative to the rollers 521. There is no contact between the profile mandrel 60 and the rollers 521, so that the rollers 521 rest in a rest position. The pushed onto the profile mandrel 60 outer hollow shaft 20 is not yet in Figure 14 with the rollers 521 in contact.

In Figure 15, the outer hollow shaft 20 together with the profile mandrel 60 is still in the Vorhubbewegung, with the difference that now the outer hollow shaft 20 is in contact with the rollers 521. The gap between the profile mandrel 60 and the rollers 521 is now filled by the outer shaft 20. By the Vorhubbewegung the outer shaft 20 together with the profile mandrel 60, the rollers 521 are rotated. They roll on the outer peripheral surface of the outer shaft 20, whereby the outer hollow shaft 20, the top described profiling undergoes because the rollers 521 in the roller center profile 531 have a small distance from the profile mandrel 60 as the not yet formed outer hollow shaft 20th

Once the desired length of the profiling and the associated groove length A of the outer shaft 20 have been reached, the return stroke movement shown in FIG. 16 begins. The outer hollow shaft 20 and the profile mandrel 60 move together in relation to the Vorhubbe- movement in the opposite direction. There is still contact between the outer shaft 20 and the rollers 521, so that during the return stroke movement the rollers 521 also rotate in the opposite direction. The return stroke movement can be maintained until the outer hollow shaft 20 and the profile mandrel 60 have left the roller burnishing head 501. Alternatively, a renewed Vorhubbewegung may follow the return stroke, for example, to improve the quality of the profiling of the outer shaft 20.

The method illustrated in FIGS. 14, 15 and 16 can also be used to manufacture hollow shafts 20, 30 without the use of a profile mandrel 60. In this case, the hollow shafts are inserted empty between the rollers 52, 521 of a rolling head 50, 501.

To improve the rolling of the rollers 521 on the shaft to be profiled and to minimize seizure in the contact surfaces, it is conceivable and possible to wet the rollers or the shaft on the corresponding contact surface with a lubricant.

Where applicable, all individual features illustrated in the individual embodiments may be combined and / or interchanged without departing from the scope of the invention.

LIST OF REFERENCE NUMBERS

10 steering shaft 40 ball

20, 201 outer hollow shaft 50, 501 Rolling head

5 21 Fork 51, 51 1 machining pass

22 groove 52, 521 roll

23 Inner surface 25 53, 531 Roller center profile

24 formations 54, 541 Roll edge profile

25 outer shell surface 56, 561 frame

10 26 molded areas 60 profile mandrel

27 circular arc section 80 sleeve

28 groove bottom (tip) 30 A length of a groove 22

29 Nutbasisfläche L length of a groove 32 30, 301 inner hollow shaft G distance

15 31 fork K1. K2 radius

32 slot M1, M2 center

33 outer jacket surface 35 P1. P2 contact point

37 circular arc section S mirror axis

38 groove bottom (tip) φ pressure angle

20 39 groove base surface

Claims

1 . Method for producing a profiled hollow shaft (20, 30) for a telescopic steering shaft (10) of a motor vehicle, comprising providing a hollow shaft to be machined and a roller burnishing head (50, 501) having at least one roller (52, 521), wherein Producing a groove (22, 32) in the hollow shaft (20, 30), the hollow shaft (20, 30) relative to the rolling head (50, 501) is moved,

characterized,

in that, in order to form a groove (22, 32), the hollow shaft (20, 30) moves relative to the rolling head (50, 501) exclusively in the direction of the longitudinal axis of the hollow shaft (20, 30).

2. The method according to claim 1, characterized in that the steering shaft (10) is linearly roller-mounted in the direction of the longitudinal axis, wherein a groove (22, 32) in a hollow shaft (20, 30) as Wälzkörperlaufbahn for receiving at least one rollable rolling element (40 ) is trained.

3. The method according to any one of the preceding claims, characterized in that a hollow shaft is formed as an inner hollow shaft (30) and on its outer periphery (33) has at least one Wälzkörperlaufbahn (32) which is introduced from the outside of the Rollierkopf (50), whose roller (52) has a convex rolling profile corresponding to the negative Wälzkörperlaufbahnquerschnitt.

4. The method according to any one of the preceding claims, characterized in that a hollow shaft is formed as an outer hollow shaft (20) and on its inner circumference (23) at least one Wälzkörperlaufbahn (22), which is introduced from the outside of a rolling head (501), whose roller (521) has a concave rolling profile.

5. The method according to any one of the preceding claims, characterized in that at least one roller (52, 521) has a Gothic profile in cross section.

6. The method according to any one of the preceding claims, characterized in that the generation of the at least one groove (22, 32) having a length (A, L) on the hollow shaft (20, 30) by a along the length (A, L) continuous Vorhubbewe- movement of the hollow shaft (20, 30) relative to the Rollierkopf (50, 501) takes place, wherein the Roller (52, 521) of the rolling head (50, 501) on the hollow shaft (20, 30) rolls continuously in the longitudinal direction.

7. The method according to any one of the preceding claims, characterized in that after a Vorhubbewegung the hollow shaft (20, 30) by a continuous return stroke relative to the Rollierkopf (50, 501) is withdrawn.

8. The method according to any one of the preceding claims, characterized in that the generation of the total number of a plurality of in the hollow shaft (20, 30) existing grooves (22, 32) takes place in a joint step with a continuous Vorhubbewegung.

9. steering shaft (10) for a motor vehicle, comprising an inner hollow shaft (30) and an outer hollow shaft (20), which are arranged coaxially to one another and telescopically te-, wherein the inner hollow shaft (30) and the outer hollow shaft (20) in the direction of the longitudinal axis extending rolling body raceways (22, 32), each radially between the shafts (20, 30) facing each other, wherein between the inner hollow shaft (30) and the outer hollow shaft (20) at least one rolling body (40) is arranged rolling on the radially opposite rolling body raceways (22, 32),

characterized,

in that at least one of the two shafts (20, 30) of the steering shaft (10) is produced by a method according to one of the preceding claims.

10. Steering shaft according to claim 9, characterized in that the at least one of the Wälzkörperlaufbahnen (22, 32) of the inner shaft (30) and / or the outer shaft (20) seen in cross-section has a Gothic profile.

1, steering shaft (10) according to any one of claims 9 to 10, characterized in that at least one rolling element is a ball (40) with at least one of the Wälzkörperlaufbahnen (22, 32) at two circumferential points (P1, P2) in contact stands, under a pressure angle (φ), which is in the range between 70 to 1 10 °.

12. Steering shaft according to one of claims 9 to 1 1, characterized in that between the inner hollow shaft (30) and the outer hollow shaft (20) has a sleeve (80) is arranged, said sleeve (80) the at least one rolling body (40 ).