WO2008012043A1

WO2008012043A1 - Method and device for producing a shaft-hub connection

Info

Publication number: WO2008012043A1
Application number: PCT/EP2007/006509
Authority: WO
Inventors: Alexander Kirchhoffer; Wilfrid Polley; Alois Schmid
Original assignee: Daimler Ag
Priority date: 2006-07-28
Filing date: 2007-07-21
Publication date: 2008-01-31
Also published as: JP2009544887A; DE102006035082A1

Abstract

The invention relates to a method for producing a shaft-hub connection (50), in particular a camshaft (100) or a transmission shaft of an internal combustion engine, in which attachment parts (26, 28) are fitted on a supporting shaft tube (34), wherein a wedge-shaped arcuate profile (42) is respectively introduced into the attachment parts (26, 28) before they are fitted on, and wherein those portions (44) of the supporting shaft tube (34) in which the attachment parts (26, 28) are fitted form in their circumference a wedge-shaped arcuate profile (46) that continuously increases the outer radius of the supporting shaft tube (34), and wherein the attachment parts (26, 28) are connected by turning the supporting shaft tube (34) and the attachment parts (26, 28) with respect to each other. In a tool (10), the supporting shaft tube (34) is locally widened in the portions (44) on which the attachment parts (26, 28) are fitted; in the same tool (10), the supporting shaft tube (34) is joined to at least two attachment parts (26, 28), in that relative turning between the supporting shaft tube (34) and the at least two attachment parts (26, 28) is performed until there is a form fit between the supporting shaft tube (34) and the at least two attachment parts (26, 28).

Description

Method and device for producing a shaft-hub connection

The invention relates to a method for producing a shaft-hub connection, in particular in a camshaft or a gear shaft of an internal combustion engine, and to an apparatus for carrying out the method according to the preambles of the independent claims.

In internal combustion engines, the camshaft has the task to open the valves for gas exchange operations as smooth as possible and close. The pursuit of lightweight construction to reduce vehicle weight, the so-called built camshaft with a hollow carrier shaft is very accommodating. As a built-up camshafts, such camshafts are referred to, which consist of several composite parts, namely a carrier shaft and attachments in the form of cams and drive wheel.

Built camshafts have the advantage that the functional division in total material costs can be saved: While the support shaft tube transmits the rotary motion to the cams arranged thereon and essentially assumes storage functions, the linear movements of the valve drive for engine control are derived from the highly loaded cams. Therefore, that can Carrier shaft tube are made of a low cost ferrous material, while the cams are made of a tool or ball bearing steel. Several known production methods are available for optimizing the geometry of built-up camshafts and for their production, of which a number are described in detail in DE 10 2004 011 815 A1 by way of example. For the production of camshafts with a hollow carrier shaft in particular the hydroforming process is generally known.

Unlike camshafts for cars, camshafts for commercial vehicles must be able to transmit much larger torques than those. Reasons for this are the higher gas exchange forces due to the larger displacement. In addition, for commercial vehicle engines, there are specific requirements for special applications to propel auxiliary equipment via the camshaft, as required. the drive of hydraulic power units in agricultural machinery via the camshaft.

In this context, has the well-known

Hydroforming process a limitation. It requires a hollow camshaft or a tube for receiving the cams, whose wall thickness also may not be too large, so that the required expander pressures remain manageable. Thus, disadvantages in the starting material for the carrier shaft tube are predetermined. In the relevant diameter ranges, seamless or longitudinally welded pipes are more expensive than a rolled all-round material. It must be taken into account that the tube must be formed at one end for reasons of strength and on one side a cap against oil leakage is required. Another aspect is that the tube compared to the solid shaft has a lower resistance torque against torsional and bending load, which may be at comparable load larger sizes required in the carrier shaft tube.

The hydroforming technology is subject to technical limitations, since the degree of deformation can not be arbitrarily high. It has to be axially displaced during hydroforming in the radial direction. The axial Nachschieben counteract frictional forces that dictate the limits of hydroforming.

Furthermore, it is problematic that the known hydroforming technology binds a relatively high capital investment. On the one hand, this depends on the hydraulic unit required to generate the pressure; on the other hand, due to the very high operating pressures of 2500 to 3000 bar, there are safety requirements which influence the investment costs. Another negative cost aspect of the hydroforming process is the ongoing operating costs. The seals, which seal the usual hydroforming lance against the support shaft tube, are subject to considerable wear and must be replaced regularly, which in turn limits the equipment utilization. Due to the non-positive transmission of operating forces can

Hydroforming technology also only to a limited extent a reliable non-positive WeIIe-hub connection for commercial vehicle camshafts.

In order to be able to join the cam disks to the carrier pipe at known built-up camshafts, the respective cam disk bore must be preprocessed. This in turn can be done economically only in the unmolded state. To give the cams their final hardness is a mostly inductive heating of the whole built Camshaft with subsequent quenching in water or oil bath required.

From the generic DE 10 2004 011 815 Al a method for producing a camshaft is known in which a plurality of cams and at least one drive wheel are mounted on a carrier shaft for cams. In those portions of the support shaft to which the cams are attached, elevations and depressions are alternately introduced such that the circumference of the portion of the cam support shaft forms a wedge-shaped arc profile continuously increasing the outer radius of the support shaft as an envelope. In the cams a matched to the increase of the outer radius of the carrier shaft bore is introduced. The cams and the at least one drive wheel are mounted by mutual rotation on the carrier shaft, wherein the cams and the drive wheel and / or the carrier shaft are elastically deformed.

In order to properly deform those portions of the support shaft to which the cams are to be mounted, the support shaft is brought into a tool and sequentially provided such a portion after the other with the desired contour. When using a carrier shaft tube instead of a solid carrier shaft, a corresponding mandrel for support during processing is necessary.

It is an object of the present invention to provide a method for producing a WeIIe hub connection that meets high strength requirements, the method should be feasible with relatively little effort and thus low cost. Furthermore, it is the task of Invention to provide an apparatus for carrying out the method.

According to the invention the object is solved by the features of the independent claims. Advantageous embodiments are mentioned in the further claims.

The inventive method for producing a shaft-hub connection is particularly suitable for a camshaft of an internal combustion engine or a transmission shaft. According to the invention, a carrier shaft tube is locally plastified in a tool in sections to which add-on parts are attached and joined in the same tool with at least two attachments.

The attachments each have a bore with a wedge-shaped arc profile, also called circular wedge profile on. The attachments are formed in a camshaft, for example, as cams and drive wheel in a transmission shaft, for example, as gears. Advantageously, all attachments to be joined are joined simultaneously to the carrier shaft tube. The joining operation includes a relative rotation between the carrier shaft tube and the at least two attachments until the positive connection between the carrier shaft tube and the at least two attachments.

Between the attachments bearings are arranged on the support shaft tube, which are not deformed. In the first process step, the carrier shaft tube is preferably preformed at all sections provided with attachment parts and then joined to the attachment parts at these sections. This is done in the same tool with preferably unchanged clamping position. This results in a significant reduction in production time compared to the stand of the technique. Furthermore, the method is insensitive to manufacturing tolerances of the joining partner carrier shaft tube and attachments. A machining of the joining surfaces can be avoided, and there is a good material utilization, since the joining surfaces are not interrupted by depressions.

The carrier shaft tube is merely preformed in a tool in a first step, preferably by known pulse, gas or hydro methods such as hydroforming (IHU) or hot metal gas forming (HMGF). Attachments already surround the corresponding sections of the carrier shaft tube. The support shaft tube is expanded by pressure from the inside and attaches to the inner profile of each attachment, without the attachments are deformed. The inner contour of the attachments acts at this point as a tool contour. The positive and non-positive shaft-hub connection is not achieved by acting in the radial direction elastic spring back serving as joining components attachments on the support shaft tube, but by the rotation of the support shaft tube against the attachments. As a material for the support shaft tube, a plastically good formable material is suitable, for example, a structural steel such as St52-3. The attachments, preferably in their configuration as cams, are preferably formed from a high strength, suitably tempered steel, such as 100Cr6. An attachment designed as a drive wheel is also favorably made of steel, for example 25MoCr4, preferably in a heat-treated state.

In addition to an Archimedean or logarithmic spiral, the wedge-shaped arc profile also has mathematical functions of a higher order, such as the Fermat, Galilean or hyperbolic spiral. Sinus spiral, lemniscate, quadratrix or others, the function itself being of lesser importance. All that matters is that the wedge-shaped arch profile is an opening function widening in polar coordinates with the angle of rotation and correspondingly deviating from the circular shape. The center of this function does not necessarily coincide with the axis of rotation of the carrier tube, so that eccentric spirals are possible.

Conveniently, an inner profile of the bore of an attachment which forms, for example, a cam disc, mirror-inverted to the inner profile of the bore of an attachment, which serves as a drive wheel. In this way, the attachment of the cams and the drive wheel to the support shaft tube can be effected in a particularly simple manner by rotating the drive wheel while holding the cams in a fixed position. The device required for this purpose is particularly simple and the method described is very easy to master. In addition, this procedure leads to the fact that the direction of rotation of the carrier shaft is in direct contact with the profile geometry under operating conditions of the internal combustion engine, whereby the strength of a preferred camshaft increases even further. In addition, if all the cams are joined simultaneously with the camshaft drive wheel, a more expensive broaching operation is not required in the machining of the cams, since any existing deviations are compensated. Of course, however, another method for relative rotation of the carrier shaft tube with respect to the attachments without drive wheel is conceivable.

The attachments are after twisting through the continuous enlargement of the radius of the support shaft tube connected to the carrier shaft tube by means of a cross-press dressing, in which no special coating of the contact surfaces (joining surfaces) is required. As a result, both in the radial and in the axial direction of the carrier shaft tube, a fixation of the attachments without additional material or the need for further process steps is given.

The following steps are preferably carried out in succession:

- The attachments are placed correctly in a lower tool part, with holes of the attachments aligned with each other so that a support shaft tube can be pushed in the axial direction.

- The carrier shaft tube is pushed through the bores of the add-on parts inserted in the tool. The carrier shaft tube advantageously has a circular ring cross section, so that the threading through the wedge-shaped arc profiles of the bores of the attachments is particularly simple. Shorter process times are achievable.

- When the tool is closed, the carrier shaft tube is subjected to an internal pressure in its interior. The support shaft tube is widened in the sections by the internal pressure in which the attachments sit until a contact of the support shaft tube is made with the internally circumferential wedge-shaped arc profile of the attachments.

- When mounting parts are fixed in the tool, the carrier shaft tube is rotated against the add-on parts until a positive connection between the carrier shaft tube and add-on parts is established. Different geometric parameters of the joining surfaces on the support shaft tube with different pitches, wedge numbers and the like, can be easily realized on the tool used, because each attachment can have an inner profile, the other way is formed as in an adjacent attachment. The carrier shaft tube can automatically adapt to the local inner profile. The joining surfaces do not have to be machined. Compared to the prior art, there is a better utilization of material, since the joining surfaces on the support shaft tube are not weakened by depressions. The contact zones of the joining partners are longer overall.

When installed, the preferred built shaft of carrier shaft tube and attachments, which may be a camshaft by way of example, preferably under operating conditions the same direction of rotation as the drive wheel during assembly to the carrier shaft tube. Accordingly, the transmission of the camshaft drive torque from the drive wheel via the carrier shaft tube on the cam discs takes place positively.

Conveniently, before the twisting of the carrier shaft tube, the internal pressure prevailing within the expansion and local plasticizing of the carrier shaft tube is reduced. Since the support shaft tube is only preformed, this jumps back slightly due to the elastic properties of the support shaft tube, forming a gap between the carrier shaft tube and the inner profile of the attachments. The gap allows the relative rotation between the carrier shaft tube and attachments.

The support shaft tube can be acted on at one or both of its ends during expansion in the axial direction with an acting along a longitudinal axis of the support shaft tube compression pressure. As a result, material can be re-fed during plasticizing, so that in the widening sections, ie in the areas in which add-on parts are arranged around the support shaft tube, the wall thickness of the support shaft tube does not decrease excessively.

Preferably, the carrier tube can be expanded with a hydroforming process. It is also conceivable that the carrier wave is heated prior to forming and expanded in a heated state or a pulse-like expansion, e.g. by electrodynamic pulse transformation, takes place. The first process step corresponds to the simultaneous preforming process of all wedge-shaped arch profiles of the carrier shaft tube in the corresponding sections in which add-on parts are to be arranged. Advantageously, a combined forming tool is used, which advantageously also forms part of the joining device.

For joining, advantageously, the attachment forming a drive wheel for rotating the carrier shaft tube can be subjected to a torque. For this purpose, a drive is attached to the carrier shaft tube.

The carrier shaft tube may be provided as tubing, or even before insertion into the tool, from a flat sheet metal strip which has been rolled, rolled into the tube, and welded.

Locally different wall thicknesses can be rolled transversely or longitudinally in the sheet metal strip that forms the future carrier shaft tube. The metal strip can be cut particularly easily to a desired axial length, for example by shearing the sheet material. For a pipe, post-processing steps are necessary during shearing, which are eliminated with the metal strip. It can be rolled in each case a metal strip with the width corresponding to the circumference of the support shaft tube, wherein the rolling direction preferably along the tube longitudinal axis. Likewise, metal strips with a width of a multiple of the circumference, preferably at least two, of the support shaft tube can be rolled, wherein advantageously the rolling direction is transverse to the tube axis. After cutting, the metal strip is then formed into a tube and closed with a weld.

The device according to the invention for carrying out the method provides a tool lower part with an engraving corresponding to distances of add-on parts on a carrier shaft tube, which can be closed with a tool upper part with a corresponding engraving. To insert the attachments, the upper part of the tool can be lifted off the tool base or tilted away. Likewise, a rotary drive can be tilted away in this state. The tool on the one hand forms a forming tool and on the other hand is part of a joining device. The carrier shaft tube and the add-on parts do not have to be inserted between the two process steps in another tool. The tool preferably comprises two dies, one being designed as a holding and fixing device for an attachment designed as a drive wheel, and the other constituting the holding and fixing device for the other attachments, for example cams or gears and other parts.

On the front side, recesses can be formed in the upper part of the tool and the lower part of the tool which, when closed, form openings through which a support shaft tube can be passed. Threading through the carrier shaft tube by the attachments inserted in the tool as well as the application of internal pressure for forming as well as the application of an upset pressure during forming is therefore very easy to accomplish. Advantageously, stops and centerings can be provided in the engraving in order to insert and fix attachments correctly. Thus, cams are arranged as attachments generally with an angular offset in their rotational position alignment to each other on the camshaft. The engraving of the tool provides the appropriate positional orientations.

The upper tool part can be formed from two parts placed longitudinally against each other. As a result, the two dies can be opened separately and different axial regions of the carrier shaft tube are exposed.

The lower tool part can be formed from two parts placed in the longitudinal direction one another or also formed in one piece.

For torque application in the second process step of joining by means of rotation, it is advantageous if the individual parts of the upper tool part are individually detachable from the lower tool part.

Furthermore, it is favorable to provide at least one hydraulic ram on the end face of the tool with which an upsetting pressure can additionally be exerted on the carrier shaft tube during expansion of the carrier shaft tube. Preferably, hydraulic punches are provided on both end faces.

For rotation, a drive unit can be provided which can be brought into operative connection with the installed carrier shaft tube on one end face. This drive unit can be swung away or pulled away when it is not needed. With long, thin-walled carrier tube tubes and a large number of attachments, it may happen that the torque to be introduced via the drive wheel and required for rotary joining exceeds the torsional strength of the carrier shaft tube. Therefore, in an alternative embodiment of the invention, it is provided to integrate the drive unit required for the respective rotary joining into the die in such a way that each individual attachment or attachment paired in groups is separately twisted or tightened. This results in the advantage that the torque required for joining each individual attachment or each group of attachments can be electronically monitored and documented. This allows a better resolution or a more sensitive quality control during the joining process. Another advantage is the fact that not the entire joining torque needs to be introduced via the drive wheel in the carrier shaft tube. Therefore, in this embodiment, the number of attachable parts to be attached to the support shaft tube plays a subordinate role, since the respectively required joining torque is locally introduced at the respective joint and the carrier shaft tube is subjected to locally lower loads.

Conveniently, the carrier shaft tube can be rotated in operative connection with the drive unit relative to the attachment parts fixed in the tool until the positive connection.

Further advantages and details of the invention are explained below with reference to preferred embodiments described in the drawing, without being limited to these embodiments.

Showing: Fig. 1 ac; a preferred tool before inserting attachments (a), closed with attached attachments (b) and threaded carrier shaft tube (c);

FIG. 2 shows a detailed view of a carrier shaft tube according to FIG. 1, which is made by two attachments; FIG.

FIG. 3 shows a carrier shaft tube in a preferred tool after a first method step with preforming of the carrier shaft tube with front side hydraulic punches according to FIG. 1; FIG.

Fig. 4 a, b; a carrier shaft tube in a preferred tool according to Figure 1 in a second method step with a relative rotation of the support shaft tube relative to fixed in the tool attachments (a) and in the removal stage after the second method step with fixed shaft hub connections (b).

5 shows a side view of an alternative rotation arrangement in a preferred tool;

Fig. 6 a-f; different shaft-hub connections before a first method step with carrier shaft tube (a, d) threaded in add-on parts, after preforming (b, e) and after a second method step with twisted carrier shaft (c, f); Fig. 7 shows an alternative manufacturing method for a

Carrier shaft tube with different wall thickness; Fig. 8 is a made of a metal strip

Carrier shaft tube with variable wall thickness:

Fig. 8a: perspective view of the rolled and longitudinally welded tube;

Fig. 8b: perspective sectional view of the tube of Fig. 8a _; FIG. 8c: shaped support shaft with variable wall thickness and circular spline profile; FIG. and

8d: perspective sectional view of

Carrier shaft of Fig. 8c; Fig. 9a, b; schematic representation of a

Rolling device (a) and an endless belt (b), can be made from the camshaft tubes.

In the following drawings, the same reference numerals are used for the sake of clarity for functionally identical or equivalent components. In that regard, reference is made to the respective preceding description.

The inventive method provides two focal points: a support shaft tube is preformed in a tool, wherein the circumferential profile at the same time specified in sections where attachments are attached by the inner profile of the attachments, and a fixed shaft hub connection is formed by the carrier shaft tube in same tool is rotated against the attachments.

In the figures Ia-Ic preparatory steps for performing the preforming of a carrier shaft tube 34 are outlined.

A preferred multi-part tool 10 consists of a lower tool part 12 and a tool upper part 16. The lower tool part 12 and the upper tool part 16 are formed in this example from two adjacent longitudinally 48 parts 12a, 12b and 16a, 16b. The longitudinal direction 48 is also that of the carrier shaft tube 34. The parts 12a and 16a form a first die Gl, the parts 12b and 16b a second die G2 of the tool 10th As can be seen with reference to the opened tool 10 in FIG. 1a, engravings 20 and 22 with recesses, stops, centering aids and the like are respectively introduced on the respective contact surfaces 14, 18 of the tool lower part 12 and of the tool upper part 16. In the engraving 20 of the lower tool part 12 add-on parts 26, 28 can be inserted correctly, ie they can already be inserted in an angular position and at intervals to each other, which corresponds to their later relative position to each other on the support shaft tube 34. The engravings 20, 22 indicate the relative angular positions of the attachments 26.

The add-on parts 26, of which only a few are numbered for clarity, are exemplified as cams, while the attachment 28 is a drive wheel, which preferably has an external toothing represents. The carrier shaft tube 34 then forms a cam carrier shaft of a camshaft. While the carrier shaft tube 34 transmits the rotational movement to the mounted thereon, designed as cams attachments 26 and essentially assumes storage functions, derived from the highly loaded cams, the linear movements of the valve train for engine control.

The die G1 forms a holding and fixing device for the attachment 28 formed as a drive wheel in the closed state, the die G2 forms a holding and fixing device for the attachments 26, ie cams and the like.

In addition to the two-part design of the lower tool part 12, it is also possible that the parts 12a, 12b are materially connected to each other and form a component. FIG. 1 b shows the state in which the attachment parts 26, 28 are inserted and the tool upper part 16 and lower tool part 12 are closed and braced against one another. The tool 10 now forms a closed die and centers all attachments 26, 28 to be joined.

Between the upper tool part 16 and the lower tool part 12, a tubular cavity 24 is provided, which is provided for receiving the support shaft tube 34. Furthermore, a preferably circular opening 30 or 32 is provided on both end faces of the tool 10, through which the support shaft tube 34 can be inserted into the tool 10.

The closed tool 10 with inserted attachments 26, 28 and inserted carrier shaft tube 34 is shown in Figure Ic. The attachments 26, 28 have inner bores which are aligned with the openings 30, 32 so that the carrier shaft tube 34 can be threaded through. The support shaft tube 34 projects beyond both sides and projects out of the openings 30, 32. Subsequently, at the ends of the support shaft tube 34 corresponding to the known hydroforming (IHU), possibly also with hot carrier tube 34 (HMGF, hot metal gas forming), a pressure medium necessary for forming for internal expansion of the carrier shaft tube 34 is supplied.

Before the joining operation and also before the preforming of the support shaft tube 34, the support shaft tube 34 are in the form of a tubular section with a circular cross-section and the prefabricated components to be joined, to be joined, with their suitable inner bores with wedge-shaped arch profiles. This can be seen from FIG. 2 on the basis of a detailed illustration, in which a carrier shaft tube 34 with a circular cross-section is made through two attachments 26 with a wedge-shaped arc profile 42 in one direction 36, corresponding to the situation in FIG. Between the surface 38 of the carrier shaft tube 34 and the wedge-shaped arc profile 42 of the attachments 26 a game 40 is present, so that the carrier shaft tube 34 is easy to push through the attachments 26.

Figure 3 shows the tool 10 of the figures Ia-Ic, in which the support shaft tube 34 is inserted. At the ends of the carrier shaft tube 34 not only the pressure medium for internal expansion is supplied, but also by means of hydraulic rams 52 from the ends of the support shaft tube 34 material in the forming a die tool 10. Thus, during reshaping with local radial expansion at portions 44 where attachments 26, 28 are placed, carrier tube 34 simultaneously undergoes length shortening.

The working pressures required for the process depend inter alia on the material properties of the carrier shaft tube 34 and its wall thickness and are typically between 2000 and 4000 bar. By this first process, the preforming of the carrier shaft tube 34 and the formation of the respective wedge-shaped arc profile 46 (or circular wedge profile) takes place at those axial positions or sections 44, which are located within the inner bores of the attachments 26, 28. Of the sections 44 are numbered for clarity, only a few with reference numerals. The profile of the particular arc profile to be formed at the joints (sections 44) of the carrier shaft tube 34 is determined by the individual profile of the inner bore of the respective attachment 26, 28. Therefore, the attachments 26, 28 have already been provided in their manufacturing process with the corresponding inner contour.

As is known from DE 10 2004 011 815 A1, this can preferably be achieved directly during forging without significant additional expenditure for the punch, which deviates from the circular cross-section. According to the invention, a deformation takes place only in the sections 44 of the carrier shaft tube 34, in which the attachment parts 26, 28 are finally fixed in the second process step. Otherwise prevents the engraving 20, 22 in the tool 10 a significant deformation at the arranged between the attachments 26, 28 bearings or other carrier shaft sections.

After the wedge-shaped arc profiles 46 are preformed on the support shaft tube 34 in the first process step, the carrier shaft tube 34 remains, as can be seen, still in the tool 10. After lowering and a withdrawal of the internal pressure necessary for preforming, the carrier tube 34 deforms by its elastic portion in radial direction back. Between the add-on parts 26, 28 and the carrier shaft tube 34, a slight radial clearance arises. Thus, unlike other known shaft-hub connections by now

Hydroforming does not yet form a frictional connection.

The die G 1 of the tool 10, which during the forming of the carrier shaft tube 34 is essentially a driving wheel forming attachment 28 had been fixed in position, is now opened. In contrast, the die G2 of the tool 10 remains closed.

This is shown in FIGS. 4a and 4b. A lateral access 56 for a drive unit 54 to the attachment formed as a drive wheel 28 is now released.

As is known from DE 10 2004 011 815 A1, the orientation of the wedge-shaped arch profile 42 on the attachment 28 designed as a drive wheel is arranged opposite to that on the remaining attachments 26. The drive unit 54 has an electric or hydraulic rotary drive with an integrated angle decoder. The drive unit 54 is connected to a control, not shown in the drawing, which allows analogous to known screw controls a programmed rotational movement or an angular suit in preset size. The drive unit 54 is now positioned in such a way on the attachment 28 designed as a drive wheel, that the latter can be rotated by positive engagement, preferably via its toothing on the outer circumference or via openings, which are incorporated into the attachment 28 designed as a drive wheel for weight reduction , As a result, all attachments 26, including the attachment 28 designed as a drive wheel, are added to the carrier shaft tube 34 via the fixed rotational movement of the attachment 28 designed as a drive wheel.

The preformed on the support shaft tube 34 in the first process step wedge-shaped arc profiles 46 now form after this rotational movement of the attachment formed as a drive member 28 against the fixed position other attachments 26 with all attachments, including the drive wheel designed as an attachment 28, shaft-hub connections 50 (FIG 4b). The attachments 26, 28 to be joined are provided with a single turning movement has been attached to the support shaft tube 34. In the direction of rotation, which represents the later operating direction of rotation in the internal combustion engine for the exemplary camshaft, the geometry of the wedge-shaped arc profiles 44, 46 is set such that the shaft-hub connections 50 act positively.

At the end of the second process step, the die G2 of the tool 10 is opened and the assembled shaft 100 can be removed.

5, a tool 10 is sketched, which uses only a single die with a tool lower part 12 and a tool upper part 16. This die has for end position positioning of the attachments 26, 28 necessary engravings 20, 22 (Fig. Ib) with centering and the like, in which the attachments 26, 28 are positioned in their final position. The carrier shaft tube 34 is inserted into the closed die as described above, threaded through the attachments 26, 28 in the tool 10, and preformed at the corresponding sections 44 by means of hydro, gas or impulse methods as described above.

A trained as a drive wheel attachment 28 is in this case with a rotating device, which includes an outer turntable 64, rolling elements 62, and an inner turntable 66 with gear recording and a drawing drive, not shown, set in rotation. Trained as a drive wheel attachment 28 is taken against rotation with its outer teeth on the inner turntable 66. To remove the finished shaft 100, the upper tool 16 is lifted off the tool base 12 or tilted away. During the reforming of the carrier shaft tube 34, the rotating device is held in a locked position. After preforming the local wedge-shaped arc profiles 46 on the carrier shaft tube 34, the rotating device is released and a drive unit 54 (Figure 4a) for introducing the necessary torque for joining with openings 60 of the rotating device engaged. About the openings 60, the inner ring gear 66 and the rotational drive on the outer toothing of the drive wheel formed as an attachment 28, the torque is transmitted to the support shaft tube 34th

Optionally, an additional torque can be effected via a further drive, which acts on the carrier shaft tube 34. The wedge-shaped arc profile 42 of the attachment 28 is in turn aligned opposite to those of the attachments 26. Thus, the carrier shaft tube 34 is joined with a defined rotational movement of the inner turntable 66.

FIGS. 6a-6f again illustrate the sequence of the method on the basis of cross-sections of a carrier shaft tube 34 with an attachment 26. The attachment 26 has an inner bore with a wedge-shaped arc profile 42. The circular support shaft tube 34 is guided by the attachment 26 (Figures 6a, 6d). The support shaft tube 34 is widened as described and adapts in the sections 44 to the wedge-shaped arc profile 42 of the attachment 26, by forming there a wedge-shaped arc profile 46 as an impression of the wedge-shaped arc profile 42. After removal of the internal deformation pressure, a small clearance between the wedge-shaped arc profile 46 of the

Carrier shaft tube 34 and the wedge-shaped arc profile 42 of the attachment 26. By rotating the support shaft tube 34, the form-fitting WeIIe hub connection 50 is made. It It can be seen that the wedge-shaped arcuate profile 42 can be formed quite differently and, for example, different pitches and / or different numbers of wedges may have, for example, a wedge number of 2 in Figures 6a-6c and a wedge number of 3 in Figures 6d-6f.

A further advantageous development of a built shaft 100 is possible in terms of its weight, if the carrier shaft tube 34 is made of a precision steel tube with non-uniform wall thickness.

By rolling a sheet metal blank or sheet metal strip 68 to be deformed, the future carrier shaft tube 34 can be "designed" by its wall thickness to the corresponding loads and stresses of the built shaft, using a rolling tool 80 with upper and lower rollers 82, 84. 7 and 10. Depending on the delivery (indicated by double arrows) of the rollers 82, 84, the minimum and maximum wall thickness 72, 74 of the starting material, for example sheet, and thus the wall thickness 72, 74 of the future carrier shaft 34 can be influenced. Advantageously, the width 86 of the metal strip 68 corresponds to the circumference of the future carrier shaft tube 34.

FIGS. 9a and 9b show a further variant of a carrier shaft tube 34 produced by rolling and welding. Flexible rolling of a sheet metal strip 68 takes place in such a way that a carrier shaft tube 34 having a defined length L is produced, which is at one end, for example in the region of an attachment formed as a drive wheel 28 has a greater wall thickness 74, as in the areas of the cam plates designed as attachments 26 and the bearings. A preferred process sequence in the production of semi-finished products is: flexible rolling, cutting to length, forming into tubes, butt welding. The cutting to length immediately after rolling is advantageous, since a flat material is much easier to separate by shearing, as a pipe, for example by sawing or flame cutting. Shearing can not be applied to pipes due to the concomitant compression of the section at the point of separation.

Furthermore, it is possible to produce very long sheet metal plates with variable plate thickness with a greater length 86. As a result, the roll stand is better utilized, as can be seen in FIG. 9b. From a sheet-metal blank which corresponds approximately to the axial length L of the finished carrier shaft tube in its width, a plurality of carrier tube tubes can be produced in the longitudinal direction after the further strip-shaped blank of this metal sheet, for example five carrier shaft tubes 34 in FIG. 9b.

Although the handling effort is possibly increased over a serial production of the metal strip 68 (Figure 7). However, this is simplified by the fact that metal strips can be rolled in such a way that the upper roller 82 in the rolling tool 80 is designed to be stepped in accordance with the desired wall thickness change (FIG. 9a). This results in the change in wall thickness of the sheet transverse to the rolling direction, while in the rolling direction, the sheet thickness does not change. Sheet metal strips 68 of variable thickness can be shaped like sheet metal strip 68 with constant wall thickness by known forming methods, for example by bending over mandrel or curling, to the tube, which is then welded in a known manner to the longitudinal abutting surface (Figure 8a). Thus, it is possible to provide a higher wall thickness in areas of the carrier shaft tube 34 in which a designed as a drive wheel attachment 28, as at the other axial zones on the support shaft tube 34, in which the attachments 26, bearings, spaces and are located. Depending on the delivery of the rollers 82, 84 different design variants of the blank of the starting material (sheet) are possible. If the distance to one another is changed equally on two opposing rollers 82, 84, a change in wall thickness results on both sides transversely to the longitudinal direction 48. The traversing movement of only one roller 82 or 84 running transversely to the rolling direction, on the other hand, only leads to a one-sided movement

Wall thickness change. The respective other roller 84 or 82 assumes a support function.

The metal strip 68 to be formed is usually wound up by a supplier into a so-called coil and made available in this form.

The metal strips 68 for carrier wave tube production can be transformed sequentially in succession. A subsequent shearing process cuts the desired sheet metal blanks as a metal strip 68 with a suitable length L for the production of the carrier shaft tube 34. The finish rolled sheet strip 68 is joined to a welded precision steel tube via a precision weld 70 by, for example, laser beam welding, DC welding, or the use of medium frequency welding, which forms the support tube 34 and is preformed and joined in the manner described above. In this case, the carrier shaft tube 34 still has a circular outer circumference, and the thickenings protrude inwards, as can be seen from FIG. 8b. Figures 8c and 8d show for comparison an arrangement in which the material thickening both inwardly and outwardly (circular spline) have (variable wall thickness).

Due to the possibility of wall thickness design and the possibility of providing different wedge-shaped curved profiles 42 along the carrier shaft tube for different attachments 26, 28, a built shaft 100 can be made to measure.

Claims

claims

1. A method for producing a shaft-hub connection (50), in particular a camshaft (100) of an internal combustion engine or a transmission shaft, wherein on a support shaft tube (34) attachments (26, 28) are mounted, wherein in the attachments (26 , 28) a wedge-shaped arch profile (42) is introduced prior to attachment, wherein those portions (44) of the support shaft tube (34) on which the attachments (16, 28) are mounted, in its circumference a the outer radius of the support shaft tube (34 ) continuously wedge-shaped arch profile (46) form, and wherein the attachments (26, 28) by mutual rotation of the carrier shaft tube (34) and the attachments (26, 28) are connected, characterized

- that in a tool (10) the carrier shaft tube (34) in those sections (44) to which the attachments (26, 28) are attached, is locally widened,

- And that in the same tool (10) the carrier shaft tube (34) with at least two attachments (26, 28) is joined by a relative rotation between the support shaft tube (34) and the at least two attachments (26, 28) to the positive connection between the carrier shaft tube (34) and the at least two attachment parts (26, 28) takes place.

2. The method according to claim 1, characterized in that at the local expansion of the carrier shaft tube (34) all sections (44) of the carrier shaft tube (34) to which the attachments (26, 28) are mounted, are widened simultaneously.

3. The method according to claim 1 or 2, characterized in that at the relative rotation between the carrier shaft tube (34) and the attachments (26,28) all add-on parts (26,28) are joined simultaneously to the carrier shaft tube (34).

4. The method according to any one of claims 1 to 3, characterized by the following steps: the add-on parts (26, 28) are placed in the correct position in the tool (10), wherein bores of the attachments (26, 28) are aligned with each other so that a support shaft tube ( 34) in the axial direction (36) can be pushed through, the carrier shaft tube (34) is pushed through the holes of the tool (10) inserted add-on parts (26, 28), with closed tool (10) is the carrier shaft tube (34) in his Inside of an internal pressure, the carrier shaft tube (34) in the sections (44) in which the attachments (26, 28) sit, expanded by the internal pressure until contact of the carrier shaft tube (34) with the inner circumference wedge-shaped arch profile (42) of the add-on parts (26, 28) is produced, in the tool (10) fixed in position attachments (26), the carrier shaft tube (34) relative to the attachments (26, 28) is rotated until a positive connection between the carrier shaft tube (34 ) and attachments (26, 28) is made.

5. The method according to any one of the preceding claims, characterized in that before the rotation of the carrier shaft tube (34) within the carrier shaft tube (34) prevailing internal pressure is reduced.

6. The method according to any one of the preceding claims, characterized in that the carrier shaft tube (34) is acted upon at one or both of its ends during expansion in the axial direction with an along a longitudinal axis (48) of the carrier shaft tube (34) acting compression pressure.

7. The method according to any one of the preceding claims, characterized in that the carrier shaft tube (34) is widened with a hydroforming process.

8. The method according to any one of the preceding claims, characterized in that the carrier shaft tube (34) is heated prior to forming and expanded in a heated state.

9. The method according to any one of the preceding claims, characterized in that the drive wheel forming attachment (28) for Rotating the carrier shaft tube (34) is acted upon by a torque.

10. The method according to any one of the preceding claims, characterized in that the carrier shaft tube (34) before insertion into the tool (10) from a formed flat sheet metal strip (68) is produced.

11. The method according to claim 10, characterized in that locally different wall thicknesses in the metal strip (68) of the support shaft tube (34) are rolled, the sheet metal strip (68) is cut to a desired axial length, formed into a tube and with a weld (70 ) is closed.

12. The method according to claim 10 or 11, characterized in that the metal strip (68) in a transverse direction to the longitudinal axis (48) having a width (86) is formed, which corresponds to the circumference of at least two carrier shaft tubes (34).

13. A device for carrying out the method according to any one of the preceding claims, characterized in that the device comprises a tool (10), in which

- Both the carrier shaft tube (34) is locally expandable and

- As well as the carrier shaft tube (34) by a relative rotation relative to those in the tool (10) inserted add-on parts (26,28) with these attachments (26,28) is available.

14. The apparatus according to claim 13, characterized in that the tool (10) comprises a tool lower part (12) with a the intervals of the attachments (26,28) corresponding engraving (20) with an upper tool part (16) with corresponding engraving ( 22) is closable.

15. The apparatus according to claim 14, characterized in that front side in the upper tool part (16) and lower tool part (12) each recesses are formed, which in the closed state of the tool (10) openings (32, 30) through which a support shaft tube (34 ) and by the inserted add-on parts (26, 28) is durchfädelbar.

16. The apparatus of claim 14 or 15, characterized in that in the engraving (20, 22) stops and centerings are provided in order to use attachments (26, 28) correct position and to fix.

17. Device according to one of claims 14 to 16, characterized in that the upper tool part (16) consists of two in the longitudinal direction (36) juxtaposed parts (16a, 16b) is formed.

18. Device according to one of claims 14 to 17, characterized in that the lower tool part (12) consists of two in the longitudinal direction (36) juxtaposed parts (12a, 12b) is formed

19. Device according to one of claims 14 to 18, characterized in that the tool lower part (12) is integrally formed.

20. Device according to one of claims 14 to 19, characterized in that the individual parts (lβa, 16b) of the upper tool part (16) individually from the lower tool part (12) are detachable.

21. Device according to one of claims 14 to 20, characterized in that the front side at least one hydraulic ram (52) is provided, with which the built-in support shaft tube (34) can be acted upon with an upsetting pressure.

22. Device according to one of claims 14 to 21, characterized in that on a front side a drive unit (54) in operative connection with the built-in support shaft tube (34) can be brought.

23. The apparatus according to claim 22, characterized in that the carrier shaft tube (34) in operative connection with the drive unit (54) relative to the in the tool (10) fixed attachments (26, 28) is rotatable to form fit.

24. The device according to claim 14, characterized in that the drive unit required for joining is integrated in such a manner in the tool (10) that each individual attachment (26, 28) separately rotatable relative to the rotationally fixed carrier shaft tube (34).