BE1030972B1 - Method for establishing a connection between a shaft and a joint fork of a steering system for a motor vehicle and steering system for a motor vehicle - Google Patents

Abstract

The present invention relates to a method for producing a connection between a shaft (5) and a joint fork (7) of a steering system (1) for a motor vehicle, comprising the steps of: - providing a tubular shaft (5) extending axially in the direction of a longitudinal axis (Z), - plastically deforming the shaft (5) to form a connecting profile (53) which has a non-circular outer cross section and which extends from an axial end face (52), - producing an axial stop (54) which projects radially over the outer cross section of the connecting profile (53) to limit the axial length (A) of a connecting section (55), - providing a joint fork (7) with a fork base (71) which has a joint side from which two fork arms (73) extend axially opposite one another with respect to the longitudinal axis (Z), and which has a connecting opening (72) which runs axially through from the joint side to a shaft side opposite this and which has a connecting opening adapted to the non-circular outer cross section of the connecting section (55). has a non-circular inner cross-section, - introducing the connecting section (55) into the connecting opening (72) until the axial stop (54) axially abuts the shaft side of the fork base (71), - caulking the end face of the connecting section (55) protruding over the joint side for axially positive support against the joint side, wherein a radially protruding material projection is produced within the connecting profile (53) by plastic deformation, which has the axial stop (54). In order to enable a less complex and more flexible design of the connection, the invention proposes that the material projection extends over one or more circumferential sections.

Description

tBE2022/5843

Method for producing a connection between a shaft and a joint fork of a

Steering system for a motor vehicle and steering system for a motor vehicle

State of the art

The invention relates to a method for producing a connection between a shaft and a joint fork of a steering system for a motor vehicle, comprising the steps: — providing a tubular shaft extending axially in the direction of a longitudinal axis

Shaft, — plastic deformation of the shaft to form a connecting profile which has a non-circular outer cross-section and which extends from an axial end face, — creation of an axial stop which projects radially beyond the outer cross-section of the connecting profile to limit the axial length of a connecting section, — provision of a joint fork with a fork base which has a joint side from which two opposite sides with respect to the longitudinal axis extend.

Fork arms extend axially and which has a connecting opening which runs axially from the joint side to a shaft side opposite this and which has a non-circular inner cross-section adapted to the non-circular outer cross-section of the connecting section, - inserting the connecting section into the connecting opening until the axial stop axially abuts the shaft side of the fork base, - caulking the end face of the connecting section which protrudes over the joint side for axially positive support against the joint side, whereby a radially protruding material projection which has the axial stop is produced by plastic deformation within the connecting profile.

A steering system of a motor vehicle has a steering column with a rotatably mounted steering spindle, which is connected to a steering gear via a cardan shaft arrangement. The

The universal joint arrangement comprises shafts and at least two universal joints. Each of the universal joints has two fork heads which are connected to one another via a universal joint, with a universal joint fork being connected to the end of each of the shafts.

To create a torque-locking connection, it is possible, for example, to

DE 689 07 617 T2, a connecting section on a tubular shaft is provided by a

? BE2022/5843 to produce a non-circular connection profile, preferably by plastic deformation of an originally hollow cylindrical shaft cross-section. The connection section is inserted into a connection opening through the fork base of the joint fork, which has a non-circular inner cross-section corresponding to the outer cross-section of the shaft profile, so that a positive connection is produced with respect to rotation about the longitudinal axis of the shaft.

An axial stop is provided on the shaft at an axial distance from the front face, which is

The outer cross-section of the connecting profile and the inner cross-section of the connecting opening protrude radially outwards. To assemble the joint fork, the connecting section is inserted into the

The connecting hole is inserted until the shaft side of the joint fork facing the shaft hits this axial stop. This is then fixed, for example by plastic deformation of the front end area of the connecting section, which is

protrudes from the joint side of the connection opening facing the joint.

In order to enable secure fixation through plastic deformation, it is essential that the front side of the connecting section protrudes far enough beyond the joint side of the connection opening, but not too far, which could impair the connection. For this purpose, it is known to adapt the length of the connecting section, which corresponds to the axial distance between the front side and the axial stop, to the length of the connection opening between the shaft and fork side, so that the connecting section is positioned in an axially defined manner to the joint fork.

In the prior art, it is known to create the axial stop by reducing the cross-section of the connecting profile or by enlarging the adjacent shaft cross-section in order to form a step or a shoulder between the connecting profile and the shaft cross-section. The disadvantage of this is the relatively high manufacturing effort for

Forming of the pipe cross-section, and that the length of the connecting section is already predetermined by the length of the connecting profile during the manufacture of the shaft.

This makes adjusting the joint fork complex and inflexible.

A method of the type mentioned above is known from JP 2007 040420 A. However, this is relatively complex. A similar hollow shaft connection is described in DE 10 2017 201709 A1.

In view of the problems explained above, it is an object of the present invention to enable a less complex and more flexible design of the connection.

> BE2022/5843

Description of the invention

This object is achieved according to the invention by the method having the features of claim 1 and the steering system according to claim 9. Advantageous further developments emerge from the subclaims.

In a method for producing a connection between a shaft and a joint fork of a steering system for a motor vehicle, comprising the steps of: — providing a tubular shaft extending axially in the direction of a longitudinal axis

Shaft, — plastic deformation of the shaft to form a connecting profile which has a non-circular outer cross-section and which extends from an axial end face, — creation of an axial stop which projects radially beyond the outer cross-section of the connecting profile to limit the axial length of a connecting section, — provision of a joint fork with a fork base which has a joint side from which two opposite sides with respect to the longitudinal axis extend.

Fork arms extend axially, and which has a connecting opening which runs axially from the joint side to a shaft side opposite this, which has a non-circular inner cross-section adapted to the non-circular outer cross-section of the connecting section, - inserting the connecting section into the connecting opening until the axial stop axially abuts the shaft side of the fork base, - caulking the end face of the connecting section which protrudes over the joint side for axially positive support against the joint side, wherein a radially protruding material projection which has the axial stop is produced by plastic deformation within the connecting profile, the invention provides that the material projection extends over one or more circumferential sections.

The shaft can preferably be provided as a pipe section with a round cross-section, which is designed as a hollow cylinder at least in one end section, preferably continuously over the entire length. At least one tubular end section of the shaft, which extends from an axial end face to one end, or alternatively over the entire tubular shaft, is formed by plastic deformation into a connecting profile, which

* BE2022/5843

Length has a preferably constant, non-circular external cross-section. For example, groove- or channel-shaped indentations distributed over the circumference and running longitudinally over the connecting profile can be pressed in, preferably by means of cold forming, preferably into a hollow shaft made of steel. In this way, for example, a cloverleaf-shaped cross-sectional profile or the like can be produced.

A joint fork to be connected to the shaft has a fork base with a connection opening that runs axially from the joint side, on which the fork arms are arranged, to the outer shaft side. The inner cross section of this connection opening is adapted in terms of cross-sectional shape and dimensions to the outer cross section of the connection profile, so that the latter can be axially inserted into it from the shaft side, whereby the non-circular cross section provides a rotationally locked connection with respect to rotation around the longitudinal axis.

positive engagement is generated.

Within the length, in other words in the longitudinal extension of the non-circularly shaped connecting profile, a material build-up is generated which has the axial stop. The material build-up is generated by material in the area of an outer layer on the surface of the connecting profile being plastically displaced preferably in the axial direction, or alternatively or additionally in the circumferential direction. Material flows in the area close to the surface and essentially no deformation of the inner cross-section occurs. The displaced material is dammed up transversely to the direction of the plastic displacement and deviates from the outer

surface outwards, so that a radially outwardly projecting accumulation of material is created, which forms the material pile. The cross section of this material pile protrudes radially outwards beyond the inner cross section of the connection opening. Accordingly, the

Material projection has an axial surface that projects radially outward from the connecting profile, which forms an axial stop. This creates a connecting section with a length that corresponds to the axial distance between the front side at the free end of the connecting profile to the

Axial area of the material throw-up.

According to the invention, the material is raised over one or more circumferential sections. One or more caulkings or the like distributed over the circumference can be provided. This makes it possible to achieve advantageous support similar to a two-, three- or multi-point bearing. In the case of a wave-shaped

Cross-section, which can, for example, have four convex-arched bulges like a

Cloverleaf profile, it can also be advantageous that only in the radially outer areas

Material piles are arranged. This can be particularly advantageous from a manufacturing point of view.

Because the material can be raised at any position at a distance from the front, regardless of the length of the connecting profile, it is possible to define the length of the connecting section with relatively little manufacturing effort. Accordingly, an optimized adjustment for fixing with the joint fork, or also on joint forks with different lengths of connecting sections, can be made in a flexible and simple manner.

openings occur.

For assembly, the connecting section is inserted into the connecting opening from the shaft side until the material projection with its axial surface hits the fork base. This clearly defines the axial positioning relative to the joint fork. The length of the connecting section is specified so that the connecting section on the fork side protrudes from the connecting opening as far as is necessary for the subsequent plastic caulking of the front side to create an axially effective positive connection with the fork side of the fork base. The caulking can include any type of plastic deformation in the area of the front side that is suitable for creating a deformation of the connecting profile that is supported against the joint side. For example, the connecting section can be axially compressed on the front side by a press stamp to create a pipe or hollow rivet-like connection.

Preferably, it can be provided that the material is thrown up by a

The plastic deformation can in particular comprise a caulking as previously explained. By means of a forming tool which preferably acts axially or obliquely from the outside against the outer surface of the connecting profile, an outward-directed material flow can be generated locally, whereby the plastically displaced material forms the material throw-up. The

The internal cross-section of the connecting profile can remain unchanged.

It can be provided that the material is thrown up all the way around the circumference. This creates a radial projection that allows a defined stop over the entire circumference. It is advantageous that a relatively small radial projection already provides a relatively large axial stop surface that offers a high axial support effect.

An advantageous further development can provide that the material throw-up is sawtooth-shaped in cross-section. The sawtooth is wedge-shaped in cross-section and has a flank that rises more gently relative to the longitudinal axis and a steeper sloping flank on the other side.

° BE2022/5843 The flatter flank can have a correspondingly conical axial stop surface that converges towards the front end. One advantage of this is that when it hits the shaft side, a more uniform force introduction can be achieved over the circumference in the edge area of the connection opening. In addition, the wedge effect can support an optimized radial fixation of the connection section in the connection opening.

It is possible that the non-circular outer cross-section of the connecting profile is smaller than the

Shaft cross-section of the shaft. The connection profile can be rationally achieved by a radial

Reduction in the cross-section of the shaft.

It is advantageous that the non-circular outer cross-section follows a continuously differentiable curve. The outer contour of the connecting profile is formed from rounded, preferably wave-shaped, curve sections that merge into one another. The uniform

Power transmission largely without local load or voltage peaks.

A non-circular outer cross-section can be designed, for example, in a cloverleaf shape or wave-shaped. Preferably, a plurality of recesses and convex bulges with a concave cross-section can be provided, which are preferably evenly distributed over the circumference, so that a wave shape is realized, which is also known as a "flower-shaped

cross-section”.

In a steering system for a motor vehicle, comprising a shaft having a non-circular, hollow

Connecting section and an axial stop, wherein the connecting section is connected to a joint fork of a universal joint, it is provided according to the invention that the connection of the shaft to the joint fork is formed according to one of the previously described embodiments according to the method according to the invention. Individual features of the described or combinations thereof can be implemented.

The key point here is that the axial stop is formed on a material projection that is arranged within the axial extension of the connecting profile. The material projection is formed as a plastic deformation within the length of the connecting profile, which is greater than the length of the connecting section. One advantage of this is that the length of the connecting section can be easily and flexibly adjusted. The plastic deformation enables high strength and correspondingly higher load-bearing capacity than with a projection produced by machining.

Description of the drawings

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

Figure 1 shows a steering system for a motor vehicle in a schematic perspective view,

Figure 2 shows a shaft according to the invention of the steering system according to Figure 1,

Figure 3 is an exploded view of the shaft according to Figure 2,

Figure 4a,b a first manufacturing state of the shaft according to Figure 2,

Figure 5a,b a second manufacturing state of the shaft according to Figure 2,

Figure 6 a third manufacturing state of the shaft according to Figure 2,

Figure 7 a fourth manufacturing stage of the shaft according to Figure 2,

Figure 8 the fully assembled final state of the shaft according to Figure 2,

Figure 9 is an enlarged detailed view of the connecting section from Figure 6.

Embodiments of the invention

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

Fig. 1 shows a motor vehicle steering system 1 in a schematic perspective

Representation. It comprises a steering column 2 with a support unit 21, which can be attached to a vehicle body (not shown).

In the steering column 2, a steering spindle 3, which forms a first steering shaft part, is mounted so as to be rotatable about a longitudinal axis L. A steering wheel 22 is attached to the steering spindle 3 at the rear, driver-side end with respect to the direction of travel.

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At the front end, the steering spindle 3 is connected via a universal joint 4 to a shaft 5, which forms an intermediate shaft. This shaft 5 has a longitudinal axis Z, which is

Longitudinal axis L of the steering spindle 3 is angled.

At the front end, the shaft 5 is connected via a further universal joint 4, which in principle can be identical in construction to the first-mentioned universal joint 4 on the input side of the shaft 5, to an end shaft 6, which can be coupled in a manner known per se to a steering gear not shown here.

The universal joint 4 has two joint forks 7 which are constructed in the same way and which are connected to one another in a manner known per se via a universal joint (not shown here).

In the following, the invention is illustrated in Figures 2 to 9 by way of example using the connection of the

Joint fork 7 with the shaft 5 designed as a hollow shaft is explained.

Figures 2 and 8 show the shaft 5 with the fully assembled joint fork 7, and Figures 3 to 8 show the respective state in individual steps of the method according to the invention.

In a first step, the shaft 5 is provided in a prefabricated state, on which a hollow cylindrical tube section 51 is formed, which has an axial end face 52 on the joint side. This state is shown in cross section in Figure 4a and in side view in Figure 4b.

In the following step, which is shown in the same view in Figure 5a in cross section and in Figure 5b in side view, a non-circular

Connecting profile 53 is created. In the example shown, this has a cloverleaf-shaped cross-section with rounded recesses formed continuously in the longitudinal direction of the Z axis.

The connecting profile 53 has a length V measured from the front side 52.

In the next step, a material projection is created within the length V of the connecting profile 53 by means of a plastic forming operation, which forms an axial stop 54, so that the ready-to-assemble state of the shaft 5 shown in Figures 6 and 9 is created.

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In the enlarged view of Figure 9, a forming tool 8 is shown schematically, which engages in the connecting profile 53 in the forming direction indicated by the arrow and produces a material projection having the axial stop 54 by plastic deformation of the outer surface.

The axial stop 54 is sawtooth-shaped in cross section and has a stop surface 56 that converges conically towards the front side 52, as can be seen in Figure 9.

According to the invention, the axial stop 54 has an axial

Distance A, which is smaller than the length V of the connecting profile 53. As a result, a connecting section 55 is formed between the end face 52 and the stop surface 56 of the axial stop 54, the length of which corresponds to the distance A. According to the invention, the axial stop 54 is arranged within the longitudinal extension of the connecting profile 53.

The joint fork 7 has a fork base 71, which has an axially continuous connection opening 72, as can be seen from Figure 3. This connection opening 72 extends from the shaft side, which is axially facing the shaft 5, to the axially opposite fork side through the fork base 71. The connection opening 72 has a non-circular

Internal cross-section that corresponds to the non-circular external cross-section of the connecting profile 53, in the example shown cloverleaf-shaped. This allows the connecting section 55 to be accommodated in a rotationally locking manner.

From the fork base 71 extend axially from the fork side two mutually

Axis Z opposite fork arms 73, which in a conventional manner each have bearing bores opposite one another transversely to the longitudinal axis Z for the rotatable mounting of a

pin pair of a universal joint not shown here.

For assembly, as indicated by the arrows in Figure 3, the connecting section 55 is inserted axially into the connecting opening 72 until the axial stop 54 with its stop surface 56 strikes the shaft side of the fork base 71 from the outside, as shown in Figure 7. The front side 52 is axially in the insertion direction on the inside, over the joint side of the

Fork base 71 forward, in Figure 7 to the left (shown in dashed lines). Then a forming tool, for example a forming punch 9 indicated in Figure 7, is pressed against the protruding end face 52 of the connecting section 55, whereby the end face of the connecting section 55 is

Caulking 57 is plastically deformed and thereby axially compressed and radially expanded.

The caulking 57 rests axially against the fork side of the fork base 71, so that a tubular or hollow rivet-like, axially positive connection with the fork base 71 is created.

As a result, the connecting section 55 is firmly and non-detachably connected to the joint fork 7 in an axially positive-locking manner in the connecting opening 72 between the axial stop 54 and the rivet-like formation on the front side formed by the caulking 57.

List of reference symbols 1 Steering system 2 Steering column 21 Support unit 22 Steering wheel 3 Steering spindle 4 Universal joint 5 Shaft 51 Pipe section 52 Front face 53 Connecting profile 54 Axial stop 55 Connecting section 56 Stop surface 57 Caulking 6 End shaft 7 Joint fork 71 Fork base 72 Connection opening 73 Fork arm 8 Forming tool 9 Forming die

L Longitudinal axis

Z Longitudinal axis

V length of 53

A Distance

Claims (9)

PATENT CLAIMS 1. Method for producing a connection between a shaft (5) and a joint fork (7) of a steering system (1) for a motor vehicle, comprising the steps: - providing a tubular shaft (5) extending axially in the direction of a longitudinal axis (Z), - plastically forming the shaft (5) to form a connecting profile (53) which has a non-circular outer cross section and which extends from an axial end face (52), - producing an axial stop (54) which projects radially over the outer cross section of the connecting profile (53) to limit the axial length (A) of a connecting section (55), - providing a joint fork (7) with a fork base (71) which has a joint side from which two fork arms (73) opposite one another with respect to the longitudinal axis (Z) extend axially, and which has a connecting opening (72) which runs axially from the joint side to a shaft side opposite thereto and which has a non-circular External cross-section of the connecting section (55) has a non-circular internal cross-section adapted to the outer cross-section of the connecting section (55), - inserting the connecting section (55) into the connecting opening (72) until the axial stop (54) axially abuts the shaft side of the fork base (71), - caulking the end face of the connecting section (55) protruding beyond the joint side for axially positive support against the joint side, wherein a radially protruding material projection is produced by plastic deformation within the connecting profile (53), which has the axial stop (54), characterized in that the material projection extends over one or more circumferential sections. 2. Method according to claim 1, characterized in that the material is thrown up by a plastic deformation introduced from the outside into the outer circumference of the connecting profile (53). 3. Method according to one of the preceding claims, characterized in that the material build-up is generated continuously around the circumference. 4. Method according to one of the preceding claims, characterized in that the material pile is sawtooth-shaped in cross section. 5. Method according to one of the preceding claims, characterized in that the non-circular outer cross section of the connecting profile (53) is smaller than the shaft cross section of the shaft (5). 6. Method according to one of the preceding claims, characterized in that the non-circular outer cross section of the connecting profile (53) follows a continuously differentiable curve. 7. Method according to one of the preceding claims, characterized in that the non-circular outer cross section of the connecting profile (53) is rounded in a cloverleaf shape or a wave shape. 8. Steering system (1) for a motor vehicle, comprising a shaft (5) which has a non-circular, hollow connecting section (53) and an axial stop (54), wherein the connecting section (53) is connected to a joint fork (7) of a universal joint (4), characterized in that the connection of the shaft (5) to the joint fork (7) is formed according to a method according to one of claims 1 to 7. 9. Steering system according to claim 8, characterized in that the axial stop (54) is formed on a material projection which is arranged within the axial extension of a non-circular connecting profile (53).