WO2012110066A1

WO2012110066A1 - Method for the production of an assembled camshaft and a method for the production of a cam element for an assembled camshaft

Info

Publication number: WO2012110066A1
Application number: PCT/EP2011/005037
Authority: WO
Inventors: Sven Burmester; Dirk Even; Bernd Schietinger; Olaf Walter
Original assignee: Daimler Ag
Priority date: 2011-02-17
Filing date: 2011-10-08
Publication date: 2012-08-23
Also published as: DE102011011501A1

Abstract

The invention relates to a method for producing a camshaft (14) that has a shaft section (12) and at least one cam element (10), particularly for an internal combustion engine, in which method the cam element (10) is designed separately from the shaft section (12) and is joined thereto in a joining region (18) on an outer peripheral side of said shaft section (12). Prior to being joined, the cam element (10) is provided with at least one alignment marker (22) for aligning the angle of the cam element (10) in relation to the shaft section (12).

Description

Daimler AG

A method of manufacturing a built camshaft and method of making a camshaft cam member

The invention relates to a method for producing a cam element for a built camshaft in an internal combustion engine of a motor vehicle. Furthermore, the invention relates to a method for producing a shaft part and at least one cam part having camshaft.

Internal combustion engines for motor vehicles often use so-called built-up camshafts. Such a built camshaft consists of a (hollow or solid) carrier shaft, to which several attachments (cam elements,

Thrust washer, drive wheel, impulse wheels ...) are joined. Built camshafts have the advantage that the materials of the individual components can be adapted very precisely to the functional requirements of these components, so that compared to a conventional one-piece (for example, produced by forging)

Camshaft both weight and material and / or manufacturing costs can be saved. Furthermore, the design of the individual components leaves much room for maneuver for a design cost-optimized design of the individual components

Manufacturing process chain and its individual sections.

The production of the cam elements is usually carried out in a three-stage process, in which initially a cam blank is forged or thermoformed from a suitable steel material, then machined and finally annealed and / or cured in a heat treatment. Such methods are known for example from DE 197 16 554 C1, DE 100 48 234 A1 and DE 101 13 952 A1. In order to meet the high loads in the operation of the camshaft, these cam blanks are often made of the bearing material 100Cr6 and then cured and tempered. However, this process is associated with high costs, since the material 100Cr6 to improve the microstructure and the machinability after the Forging heat treated (eg GKZ-annealed) must be. After machining, the material is then increased by means of hardening (for example by heating with subsequent quenching in a salt or oil bath) and subsequent tempering

Wear resistance (resistance to abrasion, rolling resistance) given for later use in the engine. In addition, the cam element must be blasted and washed several times during the manufacturing process. The described process chain is complex and prone to component quality

Edge decarburization, cracking and distortion. These quality risks can only be counteracted by a complex process management of the individual processes and additionally by a cost-intensive 100% inspection with increased scrap quantities.

To solve this problem is proposed in the generic DE 10 2007 023 087 A1, as a cam material, a curable steel material with a

Carbon content between 0.3 wt .-% and 0.8 wt .-% to use. This

Cam material is characterized by a high metallurgical robustness. For the production of the cam, a semi-finished product from this material for forming a cam blank is formed and this cam blank then a

Subjected to heat treatment. The cam described in DE 10 2007 023 087 A1 can - due to the targeted machining of the Rohnockens in the bore and on the track - are manufactured with a much higher accuracy than conventional cam; this has the consequence that this cam must be provided with a smaller grinding allowance compared to conventional cams, which leads to a reduction of the machining workings of the finished joined parts

Camshaft, leads to quality improvement and cost reduction.

The invention is based on the finding that the potential described in DE 10 2007 023 087 A1 can be further expanded in order to further reduce the costs for producing a built-up camshaft.

It is therefore an object of the present invention to provide a method for producing a camshaft, in particular for an internal combustion engine of a motor vehicle, which is cheaper to carry out. Furthermore, a method for producing a cam member for such a camshaft is to be provided. This object is achieved by methods having the features of patent claim 1 and a method having the features of patent claim 11. advantageous Embodiments with expedient and non-trivial developments of the invention are specified in the remaining claims.

In the method for producing the cam element, a cam blank is first formed from a hardenable steel material by means of a forming process and subjected to a heat treatment. Before the heat treatment, the cam blank is advantageously machined on the inner bore and on the later cam track. According to the invention, the cam blank or the cam member is additionally provided with an alignment mark, which can be used when joining the cam member to a shaft part for angular alignment of the cam member relative to this shaft part.

The cam material used is a hardenable steel material having a carbon content of between 0.3% by weight and 0.8% by weight, preferably Cf53, C55E or C56E2, if appropriate with respect to DIN 17212 or DIN EN ISO 683-17

limited or modified chemical composition to achieve improved formability, machinability and / or hardenability. It is also possible to use case-hardenable or carbonitrisable steels. Alternatively, a steel material with a carbon content of substantially 0.8 wt .-% to 1, 2 wt .-% and a chromium content of 0.2 wt .-% to 2.5 wt .-%, for example, the cam material 100Cr6 with about 1 wt .-% C and 1, 5 wt .-% Cr) are used.

Hardenable steel materials with a carbon content between 0.3 wt .-% and 0.8 wt .-% have the advantage over conventional cam materials that they are cold formable. During cold forming, thermally induced damage to the cam surface (edge decarburization, etc.) is avoided. From this and the higher dimensional stability associated with cold forming, the grinding allowance can be significantly reduced. Similar advantages can also be applied to warm forging (at

Temperatures up to 400 ° C or 500 ° C, depending on the actual material

Composition) can be achieved. Even hot forging (at about 1100 ° C) provides with these materials (e.g., Cf53 or C56E2) with proper tuning of the

Overall process chain significant starting points for quality improvement and

Cost reduction. Cam elements made of these materials are further characterized by a high metallurgical robustness, eg a lower sensitivity to touch. The starting material for the production of the cam member is rod material, from which in a first process step a slit is cut to length, from the one

Cam blank is formed. This transformation is preferably carried out by means of

Cold forming, in particular by cold extrusion. In order to facilitate the forming process, the rod material or the cam disk may optionally be heated to a temperature of up to 400 ° C.-500 ° C. prior to forming (depending on the material), so that the forming takes place as warm forging. Such a temperature increase naturally increases the deformability. The temperature is chosen in such a way that the forming takes place without microstructure impairment and no scaling occurs. Alternatively, the shaping of the cam blank can also be carried out by hot forging or hot extrusion, wherein the cam blank is cooled after the hot forming controlled from the forming heat to specifically defined hardness values

adjust. When forming by hot forging, in particular Cf53 or C56E2 offer the possibility of the usual subsequent isothermal

Heat treatment process by a cost-effective controlled cooling process from the forge heat substitute.

Subsequent to cold, warm or hot forming, the cam blank may be subjected to a cold and / or hot calibration process to achieve a highly accurate cam shape. Depending on the achievable accuracy of the

This can be necessary to reshape

to achieve the smallest possible oversize on the running surface of the cam element and thus to minimize the effort required for machining in a later process step, and

If necessary, reduce or avoid machining operations such as turning / grinding the end faces or the bore.

To reduce the so-called Schleifmaßmaß, the cam blank

advantageously subsequently or alternatively machined. In this way, an allowance to be removed later is reduced to a minimum even in the soft state of the cam element; This saves cycle time in subsequent process steps and thus

Machine capacity and investment costs. A machining pre-processing (eg milling) of the cam blanks after forming also offers the advantage that thereby the variety of variants of the semifinished product and / or the tools can be reduced. The cutting Processing of the cam blanks is preferably carried out in Einzelaufspanung. Alternatively, the processing can also be in a package setup on a common

Mandrel done. In this case, a plurality of cam blanks are received on a common mandrel and the outer contour removed circumferentially to a remaining Bearbeitungsaufmaß (about 0.4 mm) by cutting. It is particularly advantageous first to machine the cam bore and then to high precision

Orientation to edit the later cam surface. In the course of this machining of the cam member is advantageously also the generation and optionally the fine machining of the alignment mark, by means of which the finished cam element can be aligned with high precision on a shaft part.

Subsequently, the cold or half warm or hot formed and possibly

calibrated and / or machined cam blanks subjected to a heat treatment for the purpose of curing the cam surface. Preferably, the

Cam blanks inductive surface hardened. Alternatively, the cam blanks can also initially inductive short-term tempered and then surface hardened inductively, preferably then with a suitable multi-frequency technology. Alternatively, at least local hardening of the cam blanks in the area of the cam running surface can take place. The surface hardening or the at least local hardening of

Cam running surface is preferably in such a manner that in a region of the later cam surface, a surface hardness of at least 50 HRC is achieved.

In inductive surface hardening of the cam blank is at least locally austenitized, quenched and then tempered. The parameters of this hardening process are chosen so that the hardening depth of the cam elements in the ready-to-install state on the cam track is at least 0.3 mm. By the

Residual stress distribution in the cam element between the hard layer produced in the case of inductive surface hardening in the region of the cam track and the unchanged soft core results in the possibility of increased

Wälzbeständigkeit / wear resistance. Such an inherent stress characteristic of surface hardened cam elements is particularly favorable in terms of operating stress. Subsequently, the hardened cam blanks are suitably tempered. This tempering can be achieved by inductive short-term tempering, by conventional

Tempering in the furnace (typically about 2 hours at about 160 ° C) or by tempering from the residual heat of the previous process step. The aim is to produce a surface hardness of 50 HRC and 64 HRC in the area of the later cam surface. Optionally, tempering may be performed at e.g. Cf53 and C56E2 cam elements completely eliminated.

As an alternative to the above-described heat treatment of the cam blanks in the form of inductive surface hardening and subsequent tempering are also

Variations of this heat treatment process possible:

Thus, an upstream inductive short-term compensation may be necessary, e.g. if a defined core strength is required, different from that of the

Starting material is different.

- The pre-coating before the inductive surface hardening can also be done in the curing oven with subsequent quenching in the oil or salt bath.

Instead of inductive surface hardening, the cam blanks can also be prepared by austenitizing in a hardening furnace under a defined atmosphere and

hardened or quenched in a salt or oil bath.

- Furthermore, can be dispensed with the surface hardening, so that the

Heat treatment of the cam blanks includes only a short-term inductive and a subsequent tempering.

Optionally, the annealing step can be omitted, so that the heat treatment of the cam blanks comprises only inductive hardening, if necessary, an inductive or conventional annealing step (in tempering furnace with subsequent

Quenching in the oil or salt bath) upstream.

Furthermore, with a suitable material selection, the cam blanks

case hardened or carbonitrided and then tempered in the oven.

If an inductive hardening is carried out as a heat treatment, this takes place primarily in single clamping. Alternatively, the cam blanks may also be heat treated in package clamping; This has the advantage that it can take over the clamping of the previous machining. After the heat treatment, the cam geometry in further

Processing steps are changed further. So can on the one hand by the

Heat treatment process may be corrected distorted bore, whereby an increase in accuracy of the single cam is achieved, which leads to a higher accuracy of joining the camshaft blanks. Additionally or alternatively, the raceway of the cam can be ground to final contour. These processing steps can be carried out in single clamping or in package clamping. In the course of this machining step, a (further)

Fine machining (or generation) of the alignment mark, by means of which the finished cam element can be aligned with high precision on a shaft part.

Furthermore, if necessary, the cam element can be provided with a coating that can be applied, for example, by CVD (chemical vapor deposition) and / or by PVD (physical vapor deposition). At this time, the entire cam member or selected portions (e.g., the cam race surface) may be coated. The functional layer produced in this way can be a single layer or else a layer composite of a plurality of individual layers; the total thickness of the functional layer is

advantageously less than 60 μΐτι. The functional layer can be a diamond-like layer, for example a DLC coating (DLC - diamond like carbon), or a chromium nitride layer. As a result, the cam element, in particular its career, a very high wear resistance and / or a very low friction on what the functional performance safety and low fuel consumption and thus the low C0 ₂ emissions of

Internal combustion engine benefits. Furthermore, it can be provided that the functional layer composite contains fractions of a diamond-like layer (DLC coating) and / or fractions of a chromium nitride layer.

A method for producing a built-up camshaft having a shaft part and at least one cam element, in particular for an internal combustion engine of a motor vehicle, comprises a step in which the cam element formed separately from the shaft part in an outer peripheral joining region of

Wellenteils is joined with this. In this case, the cam member and the shaft part rotatably connected to each other. The cam element and the shaft part are preferably finished in time prior to the joining, in particular with regard to a machining of the cam element and the shaft part. In this case, for example, at least one cam seat surface and / or sliding bearing points and / or rolling bearing points of the particular tubular shaft part is finished. The cam seat surface is a

Outer peripheral side surface of the shaft part, in particular in the joining region, in which the cam member is joined to the shaft part. At the sliding and / or Wälzlagerstellen the camshaft is rotatably mounted in its installed state with the internal combustion engine about a rotation axis.

By this finishing of the cam member and the shaft part as a respective item in time before joining the cam member and the shaft part can be aligned with the alignment of the provided on the cam member alignment with particular precision with respect to a rotational position and thus an angle relative to each other, wherein the Joining preferably no further processing steps of the finished camshaft connect more. This is especially the case, since the shaft member and the cam member are joined together with minimal distortion due to a possible additional fixation of the shaft part, wherein also the cam member to be joined is fixed.

The alignment mark according to the invention allows a highly accurate

Angle alignment between cam element and shaft part, so that on a

Abrasive allowance for later correction of angular inaccuracies of the joined shaft can optionally be dispensed with. As described above, the cam element can thus be finished before the joining with the shaft part (including heat treatment, coating, etc.), so that the (machining) finishing of the finished camshaft can be omitted (or reduced to a minimum). The invention

Method thus allows a particularly timely and cost-effective production of built camshafts and represents another module for modularization of the drive technology for motor vehicles. The omission (or greatly reduced scope) of

Finishing steps of the camshaft leads to a time and cost reduction in the production of camshafts. This in turn leads to low costs for the internal combustion engine and thus for the entire car. Namely, the shaft part and the cam element can be processed more easily and inexpensively as individual parts (that is, before joining), in particular finished, than in their joined-together state. Furthermore, the method according to the invention enables a parallelization of working circumferences, wherein the particular tubular Shaft part can be processed temporally parallel to the cam member. In this case, a plurality of cam elements, which are to be added to the shaft part, be processed as a package. This can save further costs.

Preferably, the alignment mark is in such a manner on the

Cam member attached to at least one end face of the

Cam element is located, which extends at least substantially perpendicular to the axis of rotation of the shaft part and thus the camshaft. Likewise, it can be provided that the cam element on a first end face and on a further, opposite this end face of the cam member, each having at least one

Alignment mark is provided, which allows a particularly precise angular alignment of the cam member and the shaft part relative to each other in the joining and avoids reworking steps or keeps the effort to perform post-processing steps in a small frame. The alignment mark represents a highly accurate reference on or on the cam member

Angular alignment of the shaft member relative to the cam member may be accurate to a fraction of a degree based on the alignment mark (s), thereby reducing or even eliminating an angular error in receiving the cam member. Thus, a conventionally necessary step of reworking, in particular a regrind grinding, of the finished camshaft for compensating the angular error can be dispensed with.

The alignment mark can also serve to the shaft part and the

Align cam member relative to each other in the axial direction of the shaft part and in particular to position highly accurately. As a result of the very precise alignment of the shaft part and the cam element relative to one another, running surfaces of the shaft part can be dispensed with, in particular machining on the joined camshaft for producing a required final geometry and / or end topography, which considerably reduces the production costs.

The alignment mark may be a mark which can be detected tactilely and / or optically by means of a corresponding detection device. For example, the alignment mark may be a hole or a blind hole, which may be arranged in particular in a region of a tip of the cam element. Likewise, the alignment mark may be formed by a groove on a base circle of the cam member, which is advantageous in that the cam member in the region of the base circle in an operation of the camshaft and the Internal combustion engine is less loaded compared to other areas of the cam member.

Preferably, the at least one alignment mark is formed on the cam part such that it is detectable in the angular fine alignment of the cam element relative to the shaft part continuously, ie from both sides. In other words, the alignment mark is formed as a passage opening through the cam member which extends continuously from one end face to the other end face. Alternatively or additionally, the alignment mark may be formed as at least one recess of an end face of the cam member.

Furthermore, it can be provided that the at least one alignment mark for the angular fine alignment during joining at least substantially parallel to one

Side surface, in particular a lateral surface, of the cam member is arranged and has a maximum depth of half a wall thickness of the cam member. An angular orientation with respect to the tip of the cam element can be arbitrary.

The alignment mark can also be one or more color markings, which can be recognized, for example, by means of optical measurement technology and used to align the cam element relative to the shaft part.

For aligning the cam member with respect to the shaft portion which is performed prior to joining the joining partners, mechanical stops may be provided which engage the alignment mark of the cam member. This allows a highly accurate angular orientation of the cam member relative to the shaft part.

In a further advantageous embodiment of the invention, the at least one alignment mark is used before and / or during and / or after the joining by a mechanical and / or optical engagement for the angular fine alignment of the cam member to be joined on the shaft part relative to this. In other words, the alignment mark is optically and / or mechanically, ie by means of a touch, detected and used to position the cam member relative to the shaft part in particular with respect to a relative rotational position of the cam member to the shaft part and / or an alignment in the axial direction of the shaft part , Preferably, the joining region of the shaft part, in which the cam member is rotatably connected to the shaft part, machined, so as to ensure a firm and durable connection of the cam member with the shaft part.

Before joining, the shaft part can be finished at bearing points for sliding bearing and / or for roller bearing of the camshaft on the internal combustion engine, in particular for mounting on a cylinder head. It can at the

Camshaft both bodies for pure plain bearing as well as for a roller bearing are present in order to store the camshaft particularly friction and thus loss, resulting in low fuel consumption and low C0 ₂ emissions of the internal combustion engine result.

In an advantageous embodiment of the invention, the cam element is joined to the shaft part by hydroforming and / or by gluing and / or by a thermal shrinkage composite and / or by a mechanically generated composite and thus rotatably connected to the shaft part.

During joining by hydroforming, the tubular shaft part can be located on one side, in particular directly next to the cam element or on both sides

be kept stationary in particular directly next to the cam member by a holding device.

In the manufacture of the camshaft, a plurality of

Cam elements with the shaft part joined, so that by means of the camshaft in its installed state with the rest of the internal combustion engine a plurality of

corresponding gas exchange valves of the example designed as a reciprocating engine internal combustion engine can be operated. In this case, the plurality of cam elements are added, for example, sequentially in a respective joining region with the shaft part, in the course of sequential joining of the cam elements and rolling bearings or rolling bearing parts (inner rings) are joined in corresponding joining regions of the shaft part with this.

As a shaft part, for example, a uniform in particular in terms of its diameter and / or its wall thickness tube and a uniform clamping cover is used with free pipe ends. The alignment mark is preferably a uniform alignment mark on the cam member. A variance in the The method according to the invention is preferably and only given by the positioning of the cam element relative to the shaft part in the axial direction thereof and / or by an angular orientation of the cam element relative to the shaft part and by a length of the tubular shaft part and by a number of cam elements connected to the shaft part to add. As a cam member, a so-called flat cam is preferably used, which keeps the cost of producing the built-camshaft low.

Further advantages, features and details of the invention will become apparent from the following description of a preferred embodiment and from the drawing. The features mentioned above in the description and

Feature combinations as well as the features and feature combinations mentioned below in the description of the figures and / or shown alone in the figures are not only in the respectively indicated combination but also in others

Combinations or alone, without departing from the scope of the invention.

The drawing shows in:

Fig. 1 is a perspective view of a built camshaft;

Fig. 2 is a schematic longitudinal sectional view of a built camshaft for a trained as a reciprocating engine internal combustion engine of a motor vehicle, in particular a passenger car, with a

Plurality of cam elements;

3 shows a schematic longitudinal sectional view of the camshaft according to FIG. 2 with further elements joined to the shaft part;

Fig. 4 shows a detail of a schematic and sectioned perspective view of the camshaft according to FIGS. 2 and 3, in some areas on soft

Flange is pressed on;

5 shows a detail of a schematic and sectional perspective view of the camshaft according to FIG. 4 with one connected to the camshaft

Camshaft adjuster;

Fig. 6 is a schematic perspective view of an embodiment of a

Cam member; 7 is a schematic perspective view of another embodiment of the invention

Cam element according to FIG. 6;

8 is a schematic perspective view of another embodiment of the invention

Cam element according to FIGS. 6 and 7;

9 is a schematic representation of the process steps of a

inventive method for producing a cam member.

Figure 1 shows a built-up camshaft 14 with cam elements 10 which are mounted on a shaft part 12 by means of a joining process (e.g., hydroforming, thermal joining) together with other attachments (thrust washer, drive wheel, impulses ...). FIG. 2 shows a sectional illustration of this camshaft 14.

In Figures 6 to 8 various embodiments of the cam member 10 are shown, which is joined with a tubular shaft portion 12 to the built-up camshaft 14 shown in Figure 1 for an internal combustion engine

Motor vehicle, especially a passenger car to produce.

FIG. 9 shows in a schematic flowchart selected process steps of a method 200 for producing a cam element 10 and subsequent ones

Manufacture of a camshaft 14 using this cam member 10th

Advantageously, the cam member 10 is thereby finished (step 250) temporally prior to the joining with the shaft part 12 (step 280) such that, after the joining with the shaft part 12, a machining and / or a coating of the cam element 10 (FIG. Step 290) can be omitted (or that this post-machining 290 can be reduced to a minimum).

Starting point of the method 200 is a rod material made of a curable

Steel material, for example C56E2, in the shelled or unpeeled state, from which a slug is first cut to length, from which a cam blank 10 'is produced by a hot forming process 220, in particular by forging or by hot extrusion at about 1100 ° C., essentially already has the shape shown in Figure 6. The cam blank 10 'is advantageously cooled directly after the hot forming in a targeted manner in order to set a suitable structure as a basis for subsequent steps, ie for the subsequent cam processing in the soft state (step 230). During cam processing 230, in a (optional, ie, not necessarily continuous) first step 232, a bore 16 of the cam blank 10 'can be turned out and / or milled and / or ground. This machined bore 16 of the cam blank 10 'is penetrated in the joined state with the shaft part 12 of this. In other words, the cam element 10 produced from the cam blank 10 'is arranged via the bore 16 in an outer peripheral joining region 18 of the shaft part 12 and joined via the bore 16 in the joining region 18 with the shaft part 12 and thereby rotatably connected.

In a further machining step 234, an outer contour 20 of the cam blank 10 'is machined, in particular milled; furthermore one can

The alignment mark 22 is, for example, a bore (see the embodiment of Figure 6) or a groove (see Figure 7), by means of which the finished cam member 10 at Joining with the shaft portion 12, in particular with respect to an angular orientation of the cam member 10 relative to the shaft portion 12 can be aligned particularly precisely. In other words, it allows the

Alignment mark 22, the cam member 10 and the shaft member 12 with respect to a relative rotational position to each other about a rotational axis 24 of the shaft member 12, the cam member 10 and the camshaft 14 highly accurately aligned, so that in particular machining Nachbearbeitungs- or finishing steps 290 for correcting angular inaccuracies, such as Grinding the camshaft 14, not provided and not required. Thus, the camshaft 14 can be made particularly time-consuming and inexpensive. In the embodiments of Figures 6 to 8, the cam member 10 is provided on one of its end faces 23 with a machined alignment mark 22. It can be different

Embodiments of this alignment mark 22 give (for example, colored markers, etc.).

The introduction of the alignment mark 22 can take place in process step 230; However, the alignment mark 22 may also be generated at a later time, for example after the heat treatment following the soft working 230 (step 240) or after any coating of the cam element (step 260) to be performed. A fine machining of the alignment mark after the Heat treatment 240 has the advantage that no further thermal distortions caused by heat treatments occur at this stage. A variant is also, in the course of soft machining 230 preprocessing of

Alignment mark 22 in the soft cam blank 10 'perform and at a later date, preferably after processes with thermal distortion, the fine machining of the alignment mark 22 make.

Subsequent to the soft machining 230, the cam blank 10 'is heat-treated at least in sections (step 240). In this case, the cam blank 10 'is subjected, for example, to an inductive surface layer hardening process and thus hardened, at least in a marginal layer region 26 indicated schematically in FIG. 9. This hardening can comprise the entire cam running surface 28 or selected regions of the cam running surface which are particularly heavily loaded during operation be limited. In this way, the cam member 10 receives a

Outer circumferential side cam surface 28, 28 ', over which the cam member 10 during rotation of the camshaft 14 about the rotation axis 24 particularly wear and

Frictioniestarm a corresponding gas exchange valve of the

Can press internal combustion engine. It is also possible to completely harden or temper the cam blank 10 'by a heat treatment carried out in the furnace Atmosphere and

followed by quenching in a salt or oil bath.

The machining of the cam blanks (step 230) and the heat treatment (step 240) by means of induction hardening can be carried out in a package clamping in which a plurality of cam blanks 10 'by means of a tensioning device, e.g. using a mandrel or an outer chuck, are interconnected and cured together in this state.

After the heat treatment 240, the cam member 10 is optionally subjected to another machining process (step 250). This is the

Cam element 10 advantageously finished in such a way that its final contour is reached, so that after joining the cam member 10 to the shaft member 12 in process step 280 no further machining 290 required is. In the course of the finishing step 250, the bore 16, which is also referred to as an internal bore, can be finished (step 252). Furthermore, the outer contour 20 can undergo a so-called finish grinding and thus

finished (step 254). In the course of the process steps 252 or 254, the finishing of the alignment mark 22 may optionally also take place.

Subsequent to the heat treatment 240 and the optional machining (step 250), the cam member 10 may be provided with a functional layer 25 (step 260) which may advantageously be provided on the entire cam surface 28 or in particularly heavily loaded portions 28 "of the cam surface 28 (see FIG The functional layer 25 may be, for example, a diamond-like layer or a chromium nitride layer and applied by CVD or PVD.

Thereafter, a quality assurance of the cam member 10 is suitably carried out in a suitable test severity (process step 270).

The thus produced cam element 10 or a plurality of such cam elements can now be used e.g. be joined to the shaft part 12 by hydroforming (step IHU) (step 280). 2, the cam elements 10 are in respective outer peripheral joining regions 18 of

Shaft part 12 is fixed and thus rotatable about the axis of rotation 24 of the shaft part 12. If necessary, the cam members 10 may be brought to final contour by grinding after joining with the shaft member 12 (step 290). If, however, a finishing of the cam element 10 has already taken place in the process step 250, and if the alignment of the cam element 10 on the shaft part 12 is achieved during joining 280, the finishing of the camshaft 14 (step 290) can be omitted.

The alignment mark 22 may allow not only the relative angular orientation but also alignment of the respective cam member 10 relative to the shaft member 12 in the axial direction of the shaft member 12 according to a directional arrow 30 (see FIG. 4).

An extension of the cam elements 10 in the axial direction, which is referred to as the cam width, is typically at least 6 mm. As can be seen from FIG. 2, the shaft part 12 is designed as a tubular hollow profile and has a hollow cross-section 32 continuous in the axial direction 24. In this case, a wall thickness of the shaft part 12 for use in a car engine is typically 3 mm, whereby a low weight of the camshaft 14 is achieved. In Fig. 2 are not shown standardized rolling bearings, with which the camshaft 14 can be stored in a cylinder head of the internal combustion engine with little loss.

FIG. 3 shows a completely assembled camshaft 14 after the joining of the cam elements 10 with the shaft part 12. In the hollow cross section 32 of the camshaft 14, a sealing and support stopper 34 was introduced for a flange press fit. Furthermore, a pump cam 36 was pressed onto the shaft part 12 and finished.

As can be seen from FIG. 4, furthermore, a press-on flange 38 can be pressed onto the shaft part 12. In addition, the camshaft 14 can be rotatably connected according to FIG. 5 with a camshaft actuator 40. The camshaft divider 40 makes it possible to adjust the timing of the gas exchange valves by the

Camshaft 14 relative to a crankshaft of the internal combustion engine, with which the camshaft 14, for example via a traction means, in particular a chain or a belt, drive-connected, phased.

Figures 6 to 8 show different embodiments of the cam member 10 with different alignment marks 22. In the embodiment of Figure 6, the alignment mark 22 is in the region of a tip 42 of

Cam element 10 and is formed as a blind hole or through hole in the axial direction according to the direction arrow 30 of the cam member 10. The

Alignment mark 22 allows a direction-free and post-processing free joining of the cam member 10 and the cam members 10 with the shaft member 12 and the use of a so-called centerless ground pipe as the shaft member 12 and the use of so-called flat cams as the cam elements 10, which finished before joining become. Further, the cam elements 10 are optionally provided with a coating, in particular a DLC coating (DLC - diamond like carbon) before joining, whereby the cam elements 10 have a high wear resistance and low friction losses. So they can also be used at not quite optimal lubrication conditions.

The production of the camshaft 14 as a built camshaft 14 from the

Cam elements 10 and the shaft member 12 as respective items allows the Representation of high modularity and thus the production of built

Camshafts such as the camshaft 14 in a particularly short time and at very low cost.

In the embodiment of the cam member 10 shown in Fig. 7 is the

Alignment mark 22 as at least substantially in the radial direction according to a direction arrow 44 of the cam member 10 extending groove, groove and / or groove formed, which is arranged in the region of the tip 42.

FIG. 8 shows an embodiment of the cam element 10 with an alignment mark 22 formed as a groove. The alignment mark 22 according to FIG. 8 is arranged in the region of a base circle of the cam element 10, in which the cam element 10 during operation of the camshaft 14 in comparison to otherwise loaded areas of the cam member 10 is less.

Claims

Daimler AG claims

1. A method for producing a cam member (10) for a camshaft (14), in particular for use in an internal combustion engine of a

Motor vehicle, with the following process steps:

Providing a semifinished product made of a hardenable steel material; Forming the semifinished product to produce a cam blank (10 ') (step 220);

Heat treatment of the cam blank (10 ') (step 240);

characterized in that the cam blank (10 ') or the cam member (10) is provided with at least one alignment mark (22) for angular alignment of the cam member (10) relative to a shaft member (12).

2. The method according to claim 1,

characterized in that as a cam material, a steel with a

Carbon content of substantially 0.3 wt.% To 0.8 wt.% Is used, in particular one of the steels Cf53, C55E or C56E2.

3. The method according to claim 1,

characterized in that as a cam material, a steel with a

Carbon content between substantially 0.8 wt .-% and 1, 2 wt .-% and a chromium content between 0.2 wt .-% and 2.5 wt .-% is used.

4. The method according to any one of the preceding claims,

characterized in that at least one cam bore (16) and / or one cam race surface (28) of the cam blank (10 ') is machined prior to the heat treatment (240) (step 230).

5. The method according to any one of the preceding claims,

characterized in that

the heat treatment (step 240) includes surface hardening or at least local hardening of at least a portion (28 ') of the cam raceway surface (28).

6. The method according to any one of the preceding claims,

characterized in that

the heat treatment (step 240) is carried out by austenitizing in a hardening furnace under a defined atmosphere and subsequent quenching in a salt or oil bath.

7. The method according to claim 5 or 6,

characterized in that

the heat treatment of the cam blank (10 ') takes place in the region of the cam running surface (28) in such a manner that at least in regions

Surface hardness of at least 50 HRC is achieved.

8. The method according to any one of the preceding claims,

characterized in that

the cam blank (10 ') after the heat treatment (step 240) is provided with a functional layer (25) at least in a region (28 ") of the cam running surface (28) (step 260).

9. The method according to claim 8,

characterized in that

the functional layer (25) is applied using a CVD and / or a PVD method.

10. The method according to claim 8 or 9,

characterized in that

in the course of applying the functional layer (25) (step 260), a diamond-like layer or a chromium nitride layer is applied.

1 1. A method for producing a shaft part (12) and at least one

Cam element (10) having camshaft (14), in particular for an internal combustion engine, wherein the cam member (10) by a method according to one of claims 1 to 10 separately from the shaft part (12) is produced and in an outer peripheral joining region (18) of Wellenteils (12) with which this is added.

12. The method according to claim 11,

characterized in that

the cam element (10) and / or the shaft part (12) are finished in time before the joining, in particular with regard to a machining operation (step 250).

13. The method according to claim 11 or 12,

characterized in that

the cam element (10) is aligned relative to the shaft part (12) in the circumferential direction of the shaft part (12) on the basis of the alignment mark (22), wherein at least one detection device with the

Alignment mark (22) acts tactile and / or optical

14. The method according to any one of claims 1 1 to 13,

characterized in that

the cam element (10) is joined to the shaft part (12) by hydroforming and / or by gluing and / or by a thermal shrinkage composite and / or by a mechanically generated composite.