EP1723316A1

EP1723316A1 - Camshaft and method for producing a camshaft

Info

Publication number: EP1723316A1
Application number: EP05715761A
Authority: EP
Inventors: Alois Schmid
Original assignee: DaimlerChrysler AG
Current assignee: Mercedes Benz Group AG
Priority date: 2004-03-11
Filing date: 2005-03-05
Publication date: 2006-11-22
Anticipated expiration: 2025-03-05
Also published as: US20070006834A1; US7290515B2; WO2005088082A1; DE102004011815A1; DE502005001066D1; EP1723316B1

Abstract

The invention relates to a camshaft (1) for an internal combustion engine comprising a cam plate supporting shaft (2) on which a number of cam plates (3) and a drive wheel (4) are mounted. The outer radius of the cam plate supporting shaft (2) continuously varies in the sections in which the cam plates (3) are mounted. The cam plates (3) have a borehole (5) whose inner radius continuously varies. The cam plate supporting shaft (2) is, in the sections (2a) in which the cam plates (3) are mounted, alternately provided with elevations (7) and recesses (8) that, over the periphery of the section (2a) of the cam plate supporting shaft (2), form a wedge-shaped arc profile (9). The elevations (7) continuously enlarge the outer radius of the cam plate supporting shaft (2). The borehole (5) of the cam plates (3) is adapted to the enlargement of the outer radius of the cam plate supporting shaft (2), and exactly one wedge-shaped arc profile (9) is provided around the periphery of the cam plate supporting shaft (2) and of the borehole (5) of the cam plates (3).

Description

Camshaft and method of manufacturing a camshaft

The invention relates to a camshaft for an internal combustion engine with a cam disk carrier shaft, on which a plurality of cam disks and a drive wheel are attached, according to the type defined in the preamble of claim 1. The invention further relates to a method for producing a camshaft, in which on a cam disk carrier shaft several cam disks and at least one drive wheel are attached.

Such camshafts, which consist of several assembled parts and are used in internal combustion engines to control the valve opening times, are referred to as built-up camshafts.

In the generic DE 42 09 153 C2 a profile for a releasable shaft-hub connection is described, in which the shaft on the one hand and the hub on the other hand consist of more than one curved wedge according to a logarithmic spiral function and have a micro-toothing on the circumference. This multi-wedge profile has the disadvantage that non-contacting peripheral regions are established and the radial profile expansion is very small. The slope of the ^'logarithmic spiral is chosen so that the shaft-hub connection keeps substantially by friction. In the camshaft described in DE 41 21 951 CI, the cam disks are produced by forging and can have an opening that deviates from the circular shape. The wave profile is deformed by means of rollers and has elevations and depressions that lead to circumferential and thus circular cross-sectional changes on the shaft. By rolling or rolling, circumferential grooves are machined into the shaft, which due to material displacement raise circumferential beads. The radial elevations extend in a ring shape in the axial direction of the cam disk carrier shaft and have a radial oversize compared to the openings in the cam disks. When joining, the cam disks are individually pressed onto the carrier shaft in the axial direction between two profiling processes, similar to a longitudinal press fit. To do this, the cam discs must have a chamfer on the edge so that they do not tilt when pressed onto the shaft. The disadvantage here is that when a cam disk is pressed onto the carrier shaft, the shaft beads are partially smoothed and lose their excess due to wear during joining. For this reason, the cam disks are cleared in a complex manner in the described method for the purpose of introducing a rotationally symmetrical micro toothing.

The so-called hydroforming process is often used in the production of other camshafts, which can result in considerable cost savings. The main advantage of the built camshaft using the hydroforming process compared to conventional solutions is the reduction in material costs. A relatively inexpensive, untreated steel material is used for the actual shaft, which is also referred to as the cam disk support tube, and a high-quality, alloyed, hardenable ball bearing steel for the cam disks. The carrier tube is compressed at the end to which the camshaft drive wheel is attached for the purpose of increasing the wall thickness. At the ends and on the circumference there is a machining. The cam disks are forged, machined and heat treated. After joining by means of internal high pressure forming, the cam forms and the camshaft bearing seats are ground in different workpiece clamps on the assembled camshaft.

Unlike camshafts for cars, camshafts for commercial vehicles must be able to transmit significantly higher torques. The reasons for this are the higher gas exchange forces due to the larger displacement. There are also ^'for commercial vehicle engines requirements of special applications to power on the camshaft, if necessary auxiliary equipment, such as the drive of hydraulic units in agricultural machinery on the camshaft.

In this context, the internal high-pressure forming process has a considerable limitation: it requires a hollow camshaft or a tube for accommodating the cam disks, the wall thickness of which, moreover, must not be ^" too large so that the required expansion pressures remain manageable In the relevant diameter ranges, the seamless drawn or the longitudinally welded pipe is more expensive than the rolled round material .. - It must be taken into account that the pipe must be formed at one end for strength reasons and a sealing cover on one side A further aspect is that the tube has a lower moment of resistance to torsion and bending stress compared to the solid shaft, which under certain circumstances may require larger dimensions for the shaft tube with a comparable load.

Another problem is that the internal high pressure forming technology ties up a relatively high investment in the plant. On the one hand, this is related to the hydraulic unit required to generate pressure, on the other hand, due to the very high operating pressures of 2500 to 3000 bar safety requirements that influence the system costs. Another negative cost aspect of the hydroforming process is the running operating costs. The seals that seal the internal high-pressure forming lance against the camshaft tube are subject to considerable wear and must be replaced regularly, which in turn limits the system efficiency. Due to the non-positive transmission of the operating forces, the hydroforming technology can only be a reliable, non-positive shaft-hub connection for commercial vehicle camshafts to a limited extent.

In order that it is even possible to join the cam disks to the carrier tube on known built cam shafts, the respective cam disk bore must be pre-machined. Again, this can only be done in the unclaimed state. To give the cams their final hardness to ^', is a mostly inductive heating followed by quenching in Wasserbzw. Oil bath required.

A method for producing a built-up camshaft and a built-up camshaft from a shaft tube and pushed-on elements using the internal high pressure forming are known from EP 0 265 663 B2. The shaft is expanded hydraulically, which means that the shaft-hub connection is created by frictional connection.

In the case of the built shaft according to EP 0 328 009 Bl or EP 0 328 010 Bl, a tube is expanded by means of internal high-pressure forming, the cam disks being fastened on two tubes which are placed one above the other in order to increase the rigidity. Torques are transmitted non-positively. Due to the large number of components required, this is a relatively expensive solution. EP 0 374 389 B1 describes a method for pretreating components of a built-up camshaft. There, heat treatment measures for a tube are described, which should make it possible that the tube can either be expanded better by internal high-pressure forming, or that the bearing points become more hard.

In the built shaft according to EP 0 374 394 B1, the cam disk support tube is preformed with different cross sections so that only the tube sections which receive the cam disks are plastically deformed during subsequent expansion by means of internal high pressure forming. The pipe sections between the individual cam disks are only expanded elastically.

In the method for producing a camshaft described in EP 0 313 565 B1, tubes are used as supports for the cam disks. The cam disks are converted together with the carrier tube on the ^basis' of the circular cross-section in a die, so that a built-up camshaft results. Disadvantageously, no hardened cam disks can be formed at room temperature, otherwise they break apart or at least form cracks. Therefore, a separate heat treatment process is required in the method described there.

A method for producing a built-up camshaft using internal high pressure forming and a built-up camshaft made of a shaft tube and pushed-on elements are described in EP 0 265 663 AI. The cam disks can have inner profiles in their openings so that, in addition to the frictional connection, there is also a positive connection, the tube forming the shaft being plastically deformed while the cam disks are being elastically expanded. A composite camshaft is known from EP 0 516 946 B1, in which a hollow shaft is machined by means of internal high pressure forming. The cam disks attached to the shaft have a circular cross-section and a groove running in the axial direction, which is at least partially filled with the material of the shaft by plastic deformation during hydroforming, so that a positive rotary connection is established.

EP 0 730 705 B1 describes a method for producing a one-piece hollow camshaft, in which a tube is expanded in the die by internal high-pressure forming in such a way that a hollow camshaft results. It is advantageous that no separate cam disks have to be produced. On the other hand, it is disadvantageous that heat treatment of the camshaft is required. In addition, the wall thickness of the camshaft is particularly strongly reduced in the areas of the cam tip, which means that the strength requirements for a commercial vehicle camshaft can hardly be met with this technology.

A camshaft and a method for producing the same are described in EP 0 970 293 B1. Thin cam disks are punched out of a metal sheet or sheet metal strip. A majority of these flat materials are assembled into sheet metal stacks above or next to one another. Accordingly, a cam disc consists of several parts that are ultimately joined to a tube by internal high-pressure forming. The cam discs can have a toothing or a notch-like profile on the circumference, which serves for orientation in the rotational position.

The built-up camshaft known from EP 0 856 642 AI is based on a longitudinal press dressing, the joining partners being coated at the joining points. The coating can be a Phosphate layer, but also be adhesive. A profiling option that is not specified in more detail is also addressed.

EP 0 839 990 B1 is based on a cam disk carrier shaft produced by casting. This shaft can be profiled at the points where the cam discs are attached. The non-rotationally symmetrical profile is cast on for the purpose of balancing and thus serves for better mass distribution of the shaft. Cold forming of cast iron components is generally considered problematic because of the brittleness of the material.

In the very similar method according to DE 37 17 190 C2, the profiling is carried out using rolling rods which have longitudinal grooves. The course of a groove in the rolling tool essentially follows the direction of movement of the rolling rod, which has the same profile in every cross section transverse to the direction of movement. In the case of optionally provided thread-like, bead-like enlargement of the cam disk support shaft, the recess does not extend exactly in the direction of movement of the roller bar, ^• but is inclined to the thread pitch angle. The cross sections of a rolling rod are then not completely the same over the length. However, in the side view - each roll bar appears as a rectangle. The longitudinal boundary lines of the side view of a rolling rod are parallel to the direction of movement. The polygon mentioned here as an example for the profile of the carrier wave deviating from the circular shape has only the aim of approximating a circular shape.

The composite camshaft described in DE 195 20 306 CI is an indirect positive connection. A corrugated adapter sleeve is used, which engages in a rotationally symmetrical shaft toothing and in a likewise rotationally symmetrical inner toothing on the cam disk opening. The disadvantage here is however, the handling of the adapter sleeve as a separate component.

EP 0 580 200 B1 relates to the configuration of the cam disk for the purpose of lightweight construction, for which purpose it is made from a thin sheet. However, this construction is unlikely to meet the strength requirements for a camshaft.

The formation of the axial transition zone between two cam elevations located close to one another is known from EP 0 459 466 B1. This is only important for one-piece, but not for built camshafts.

In the method proposed in EP 0 650 550 B1, a cam disk support tube is mechanically widened by a punch that is pierced or drawn through. This requires that the cam disk support tube has different wall thicknesses before joining. The joining surface can have recesses, pockets or a toothing. If a toothing is provided for the profile of the joining surface, this is on both joining partners, that is. to be attached to the camshaft and the cam discs.

In the very similar method according to EP 0 663 248 B1, different wall thicknesses are worked into a tube by means of a step-shaped mandrel.

Another built crankshaft and a method for producing the same are described in DE 100 61 042 C2. A conical bogie wedge is used here. A maximum of two crank webs can be attached to a crank pin by rotating them against each other. The joining surfaces have to be machined due to the high tolerance requirements. When joining, the shaft is essentially elastically deformed, the connection being releasable. All of the methods described are therefore not able to meet the requirements placed on a highly stressed camshaft in the sense of a simple and inexpensive solution.

It is therefore an object of the present invention to provide a camshaft that meets high strength requirements and a method for producing a camshaft that can be carried out with relatively little effort and thus low costs.

According to the invention, this object is achieved by the features mentioned in claim 1.

According to the present invention, a single wedge-shaped arch profile formed from alternating elevations and depressions is provided on the circumference of those sections of the cam disk carrier shaft in which the cam disks are attached. In contrast to known solutions, it is therefore not a question of rotationally symmetrical or circumferential grooves or beads, but of a non-circular profile for each cam disk attachment. The cam disks are connected to the cam disk carrier shaft by means of a cross-compression bandage, in which no special coating of the contact surfaces is required, by continuously increasing the radius of the cam disk carrier shaft. As a result, both in the radial and in the axial direction of the cam disk support shaft, a fixing ^'of the cam plates without additional material or the need for further process steps given.

Because, according to the invention, exactly one wedge-shaped arc profile is provided around the circumference of the cam disk carrier shaft and the bore of the cam disks, on the one hand a larger one is obtained with the same slope of the wedge-shaped arc profile Diameter difference and thus a higher strength of the connection can be achieved. On the other hand, the inevitable loss zone, i.e. the area in which the cam disks are not in contact with the cam disk support shaft, is smaller, so that the cross-section of the connection is better utilized regardless of the initial play.

It can be assumed that the strength of the connection between the cam disk support shaft and the cam disks according to the present invention is significantly higher than in the case of solutions according to the prior art. In addition, it is possible with the camshaft according to the invention to connect unprocessed cam disks to the cam disk support shaft, which represents a considerable time and thus cost saving.

When the inner profile of the bore of the cam disks mirrored in an advantageous development of the invention adapted to the inner profile of the bore of the ^'drive wheel, the mounting of the cam disks and the at least one drive wheel to the cam disk support shaft in a particularly simple manner can be effected in that the drive wheel is rotated while the cam discs are held in a rigid position. The device required for this can be constructed in a particularly simple manner and the described method is very easy to master.

In addition, this procedure leads to the fact that the direction of rotation of the camshaft under operating conditions of the internal combustion engine is directly related to the profile geometry, which further increases the strength of the camshaft according to the invention. If all the cam disks are joined at the same time with the camshaft drive wheel, the expensive broaching process is also part of the Machining of the cam disks is not necessary, since any dimensional deviations that may exist are compensated for.

A particularly high strength of the camshaft according to the invention is obtained if the camshaft carrier shaft is designed as a solid shaft. Alternatively, however, it is also possible for the cam disk carrier shaft to be designed as a hollow shaft. In this case, however, it should be provided that a mandrel is inserted into the hollow shaft for machining the cam disk carrier shaft.

A particularly simple reshaping of the cam disk carrier shaft is possible if the depth of the depressions increases continuously with the increase in the elevations.

A procedural solution results ^• ■ from the features of the claim. 8

The method according to the invention allows such large manufacturing tolerances that the _. There is no need for soft machining of the bore of the cam disks, and cost savings can thus be achieved. In addition, it is only necessary in the present invention to transform the outer profile of the cam disk support shaft and not at the same time ^_', and the cams. This has the advantage that the contacting joining surface is larger and that no other aids such as, for example, preparatory shrinking of the cam disks onto the cam disk carrier shaft or subsequent widening of the cam disk carrier shaft or even soldering of the joining surfaces is required.

According to the invention, the cam disks are pushed onto the cam disk support shaft with play and fixed by a rotary movement. As a result, as well as around the geometry according to the invention, the question of centering advantageously plays the joining partner hardly plays a role, as a result of which the outlay for the method according to the invention is relatively low.

In an advantageous development of the method according to the invention, it can be provided that when the cam disks and the at least one drive wheel are attached to the cam disk support shaft, the cam disk support shaft is plastically deformed, the cam disks and the at least one drive wheel being elastically expanded. After the indentations and elevations have been introduced into the wave profile in order to form an arc wedge profile through the envelope curve surrounding the widenings, the profile of the cam disk support shaft can be partially smoothed out again during the joining by this plastic deformation. The connection between the cam disk carrier shaft and the cam disks is essentially maintained in this way by the plastic deformation of the shaft during joining and by the elastic expansion of the hub. This is also advantageous if the individual cam disks have certain dimensional deviations, since these are compensated for by the plastic deformation.

When the elevations and depressions are introduced ^'by means of cold working in the cam disk support ^shaft', so a further increase in the strength of the camshaft results. A special heat treatment ^' or another special measure to increase strength is not necessary.

In this connection it can be provided that the elevations and depressions are introduced into the cam disk carrier shaft by means of two rod-shaped rolling tools that move relative to one another. Depending on the requirements for the elevations and depressions of the toothing, considerable cost savings are possible compared to ^• conventional processes such as hobbing or gear shaping. Compared to one gearing produced by machining advantageously the gearing formed at room temperature has a higher strength.

In an advantageous development of the method according to the invention, the profile of the cam disk bore can be produced by forging in the required final quality, which leads to a further simplification of the production of the camshaft according to the invention.

Further advantageous refinements and developments of the invention result from the remaining subclaims. In the following, exemplary embodiments of the invention are shown in principle with reference to the drawing.

Show:

Figure 1 is a side view of the camshaft according to the invention.

2 shows a first embodiment of the introduction of elevations and depressions into the cam disk support shaft according to the inventive method in a first state;

3 shows the method from FIG. 2 in a second state;

FIG. 4 shows the method from FIG. 2 in a third state;

5 shows the method from FIG. 2 in a fourth state;

FIG. 6 shows a modification of the method from FIG. 2;

7 shows a second embodiment of the introduction of elevations and depressions into the cam disk carrier shaft according to the method according to the invention in a first state; 8 shows the method from FIG. 7 in a second state;

FIG. 9 shows the method from FIG. 7 in a third state;

10 shows the attachment of the drive wheel to the cam disk support shaft according to the method according to the invention in a first state;

11 shows the attachment of a cam disk to the cam disk support shaft according to the method according to the invention in a first state;

FIG. 12 shows the method from FIG. 10 in a second state;

13 shows the method from FIG. 11 in a second state;

FIG. 14 shows the method from FIG. 10 in a third state;

15 shows the method from FIG. 11 in a third state;

16 shows the method from FIG. 10 in a fourth state; and

FIG. 17 shows the method from FIG. 11 in a fourth state.

1 shows a built-up camshaft 1, which has a camshaft carrier shaft 2, on which, in the assembled state, a plurality of camshafts 3 and a camshaft drive wheel or drive wheel 4 are attached in a rotationally fixed manner to respective sections 2a thereof. The camshaft 1 is used in a known manner to control the valve opening times in an internal combustion engine, not shown. The cam disks 3, the number of which depends on the internal combustion engine, each have a bore 5 for mounting the same on the sections 2a of the cam disk support shaft 2 and are generally offset from each other by a certain angle.

The camshaft 1 also has a plurality of bearing points 6, in which it is supported under operating conditions in a crankcase of the internal combustion engine. In Fig. 1, the camshaft 1 is shown in its unassembled state, the cam disks 3 and the drive wheel 4 each having play sl, s2 and s3 with respect to the cam disk support shaft 2. It can be seen that the axial distance a between two adjacent cam discs 3 is greater than the width b of a cam disc 3.

A round material made of steel, which can be hot-rolled, for example, is preferably used as the starting material for the cam disk carrier shaft 2. The requirements for the material of the cam disk support shaft 2 are a certain cold formability and toughness. A special heat treatment by tempering or a particularly high wear resistance is not necessary. However, drawn round materials with a circular starting cross section can also be used as semi-finished products for the cam disk support shaft 2. Hollow bodies such as pipes can also be used, as a result of which the entire camshaft 1 'would have a lower mass and a deep hole for supplying lubrication points could be dispensed with. In this case, however, a mandrel should be inserted into the hollow shaft for machining the cam disk carrier shaft 2 described later.

As described below with reference to FIGS. 2 to 5, a tooth-like profile with several local elevations 7 and a corresponding number of local depressions 8, which are arranged alternately to one another, is introduced into the cam disk support shaft 2. Through the targeted introduction of the depressions 8 into the upper surface of the camshaft carrier shaft 2 is a wedge-shaped arc profile 9 is generated by material displacement as an envelope of all ridges 7, the outer contour of the sections 2a is similar to a toothing with interrupted wings. The depressions 8 made in the shaft do not represent micro-toothing to increase the frictional engagement. At best, they can be understood as macro-toothing.

For processing the cam disk carrier shaft 2, two rod-shaped rolling tools are provided, which are referred to below for the sake of simplicity as rolling rods 10 and 11 and are provided on their respective mutually facing sides with profiles which are provided with alternating gaps and projections and with a relative movement the two rolling racks l ^'O and the elevations 7 and depressions 8 contribute 11 by cold forming in the cam disk support shaft. 2 For processing, the cam disk carrier shaft 2 is preferably clamped between tips, not shown, whereupon the rolling rods 10 and 11 move in the direction of V ₁₀ and Vo. set the arrows in motion synchronously and at the same speed. As a result, the cam disk carrier shaft 2 is rotated according to the arrow V ₂ and moves several times around its own axis during processing. The length of the two roller bars 10 and 11 therefore corresponds to a multiple of the diameter or the circumference of the cam disk carrier shaft 2. During the translational movement of the roller bars 10 and 11, these exert a radial pressure on the cam disk carrier shaft 2 and shape it. It can be seen from FIGS. 2 to 5 that the profile depth of the rolling rods 10 and 11 increases over the length thereof, as a result of which the required forming forces change.

The entire rolling process shown in FIGS. 2 to 5 can be completed after a few seconds, after which move the rolling rods 10 and 11 back to their starting position. The cam disk carrier shaft 2 can then be displaced along its longitudinal axis to the next section 2a to be shaped, whereupon the introduction of the elevations 7 and the depressions 8 to form the wedge-shaped curved profile 9 is repeated.

During the forming process, each gap of the profile of the rolling rods 10 and 11 which runs transversely to the direction of movement of the rolling rods 10 and 11 forms an elevation 7 and each projection which also extends transversely to the direction of movement of the rolling rods 10 and 11 forms a recess 8 on the cam disk carrier shaft 2. For the illustrated embodiment, the profile of the roll bars 10 and 11 it is clear that the elevations 7 ^• continuously increase the radius of the cam disk support shaft 2, since each subsequent gap of the profile is lower than the respective preceding. In the present case, this also means that the higher the protrusions of the profile of the rolling rods 10 and 11, the deeper the gap behind it, which facilitates material penetration during the forming process.

In the present case, the wedge-shaped arch profile 9 resulting from the reshaping, that is to say the envelope around the elevations 7, is designed as an Archimedean or logarithmic spiral. In addition to an Archimedean or logarithmic spiral, higher-order mathematical functions such as the Fermat, Galilean or hyperbolic spiral ^" , sinus spiral, lemniscate, quadratrix or others would also be considered for the wedge-shaped arch profile 9, the function itself being of subordinate importance The only important thing is that the wedge-shaped arc profile 9 is an opening function which expands in polar coordinates with the angle of rotation, .sich. And deviates from the circular shape. The center of this function does not necessarily have to be with the axis of rotation of the Cam disk carrier shaft 2 collapse, so that eccentric spirals are also possible.

The geometric relationships are simplified if an Archimedean spiral with the gradient tanα is selected as the envelope profile for the connection of the cam disks 3 to the cam disk support shaft 2. In this case, the deepest points of all the gaps in the profile of the rolling rods 10 and 11 lie on a straight line which, with the direction of movement io and n of the rolling rods 10 and 11, includes the pitch angle α. However, it may also be provided that the deepest points of all the gaps in the profile of the rolling rods 10 and 11 lie on a curved path. This also applies to the highest points of all the highest points of the projections of the profile of the rolling rods 10 and 11.

When machining a projection, two rolling rods 10 and 11 are provided in order to support the cam disk support shaft 2 during the rolling process and to derive the rolling forces. The rolling rods 10 and 11 are preferably geometrically identical and are arranged with an offset to one another which corresponds to half the central circumference of the cam disk carrier shaft 2. The rolling rods 10 and 11 can be optimized in such a way that the forming work required for introducing the wedge-shaped curved profile 9 into the cam disk carrier shaft 2 is distributed uniformly over both rolling rods 10 and 11. The cam disk support shaft 2 can be driven indirectly by the rolling rods 10 and 11 by the same. However, it is also possible to drive the cam disk carrier shaft 2 during rolling via its own regulated rotary drive, for which purpose the cam disk carrier shaft 2 must be tensioned in a suitable holding device, such as a jaw chuck or a collet. The rolling rods 10 and 11 are preferably made of hardened steel and have the width b of the cam disks 3. The depressions can be introduced into the rolling rods 10 and 11 by known machining techniques, which include, for example, surface grinding and deep grinding with a correspondingly profiled grinding wheel. The grinding wheel profile, in turn, can be worked into the grinding wheel, for example, using CNC-controlled dressing using a diamond tile.

For each section 2a to which ^■ a cam disk 3 is attached to the cam disk support shaft 2, as indicated above, a separate, successive shaping process is provided, for which purpose the cam disk support shaft 2 remains tensioned. Between the forming processes, however, the cam disk carrier shaft 2 must be repositioned in its rotational position in accordance with the required angular displacement of the cam disks 3 and, if necessary, including the rotary drive, axially shifted accordingly, the distance a + b of the adjacent cam disks 3.

As shown in FIG. 6, it is also possible to form all sections 2a for the cam disks 3 in a single rolling step. For this purpose, two rolling rods 10, 10 'and 11, 11' or a number of pairs of rolling rods 10 and 11, 10 'and 11', ... corresponding to the number of cam discs 3 must be provided at a distance a for each section 2a of the cam disc carrier shaft 2 be, which increases the productivity of the rolling process significantly ^' . All of the lower rolling rods 11 and 11 'are fastened to a lower slide 12 which can be displaced transversely to the axis of rotation of the cam disk carrier shaft 2, so that ^' the lower rolling rods 11 and 11 'can be moved synchronously with the rotation of the cam disk carrier shaft 2. Not shown is an upper slide which receives all of the upper rolling rods 10, 10 ', ... and moves in the opposite direction to the lower slide 12. ^' FIGS. 7, 8 and 9 show an 'alternative forming method for forming the wedge-shaped arch profile 9 in the sections 2a of the cam disk support shaft 2. For this purpose, a die 13 is provided which, in the present case, has three die parts 13a, 13b and 13c which can be moved relative to one another, each with a profile which forms the elevations 7 and the depressions 8. In the die 13, the illustrated closing and opening movement of the die parts 13a, 13b and 13c reshapes the cam disk support shaft 2 with swelling or pulsating pressurization, for example by hammering. The die parts 13a, 13b and 13c each have the width b of the cam disks 3. During machining, the die parts 13a, 13b and 13c execute a radial movement relative to the cam disk carrier shaft 2, the force being introduced for the shaping of the material with the aid of a known, linearly guided actuator hydraulically, pneumatically, or electromechanically.

Similar to the roll profiling described above, the individual profile cross sections of the cam disk support shaft 2, that is to say the sections 2a to be formed, are formed one after the other, for which purpose the cam disk support shaft 2 is brought into a new angle of rotation before the forming. Alternatively, it is of course also possible to arrange a plurality of dies 13 in the longitudinal direction of the cam disk carrier shaft 2 and to provide all sections 2a of the cam disk carrier shaft 2 with the wedge-shaped curved profile 9 at the same time.

In an embodiment that is not shown, it would also be possible to cast the cam disk support shaft 2, for which purpose the corresponding casting mold could be at least 'similar to the die 13 on the sections 2a.

The manufacture of the cam disks. 3 is not shown in the figures shown. These can be forged, for example, the forged contour advantageously being close to the end contour of the cam disks 3. It is then only necessary to machine the outer functional surface of the cam disks 3 for valve control. This is also true for the Lagerstelϊ ^'en 6- .the cam disk support shaft 2 by the process described in the following the assembly of the cam shaft 1. Also, a production of the cams 3 by casting or sintering is possible. As can be seen in FIGS. 10 to 17, the inner profile of the bores 5 of the cam disks 3 is adapted to the elevations 7 and thus to the increase in the outer radius of the cam disk support shaft 2 and thus to the wedge-shaped curved profile 9.

The manufacturing technology described with reference to FIGS. 2 to 6 and 7 to 9 for the forming of the sections 2a of the cam disk carrier shaft 2 for receiving the cam disks 3 can also be adopted in an identical manner for the shaft profile for receiving a bore 14 of the drive wheel 4 , For the reasons explained below, the only difference is that the winding or Opening orientations -des wedge-shaped curve profile 9 of the wavy profile for receiving the ^'drive wheel 4 in mirror image to the wedge-shaped sheet profiles 9 are for receiving the cam discs. 3 For assembly reasons, the slope of the wedge-shaped arch profile 9 of the shaft profile for receiving the drive wheel 4 will generally be greater than that for receiving the cam disks 3.

The bore 14 of the drive wheel 4 also essentially corresponds to the bore 5 of the cam disks 3. However, the inner profile of the bore 5 of the cam disks 3 is mirror-inverted to the inner profile of the bore 14 of the drive wheel 4.

Figures 10 and 11, 12 and 13, 14 each show in pairs and 15, as well as 16 and 17, the 7Λblauf in a possible embodiment of the attachment of the cam disks 3 and the drive wheel 4 on the cam disk support shaft 2. In FIG. 10 it is shown that the drive wheel 4 is clamped by means of three clamping elements 15. The clamping elements 15 are part of a rotating device, not shown in its entirety, which has a rotary drive, which is preferably regulated and has monitoring of the angular position of the clamping elements 15 and thus of the drive wheel 4. In contrast, the cam disks 3, as can be seen in FIG. 11, are clamped in a rotationally fixed manner by means of two clamping elements 16 and fixed in their position. If, as shown in FIGS. 12 and 13, the drive wheel 4 is rotated by the angle l against the fixed cam disks 3, the initial joint play sl of the drive wheel 4 against the cam disk support shaft 2 decreases to 0. However, the cam disk carrier shaft 2 is not rotated relative to the cam disks 3.

In the further rotation of the drive wheel 4 against the fixed cam disks 3 by the angle 2 shown in FIGS. 14 and 15, the cam disk support shaft 2 is also set in rotation by the angle φ2 by positive entrainment. As a result of this rotational driving of the cam disk carrier shaft 2 with respect to the cam disks 3 by the angle φ2, the initial joint play s2 also decreases to 0, which can be seen in FIG. 15. Due to the dimensional tolerances, the reduction of the initial joint play s2 on each cam disk 3 is achieved at a different point in time or at a different angle of rotation of the drive wheel 4.

When the drive wheel 4 is further rotated by the angle φ3, as shown in FIG. 16, the plastic deformability of the cam disk support shaft 2 and in particular of the wedge-shaped arc profile 9 thereof is utilized. By the torque, which for rotating the drive wheel 4 around Angle 3 is required and acts on the cam disk carrier shaft 2 via the rotating device of the drive wheel 4, reaction forces acting in the radial direction are formed, among other things. These act from the cam disks 3 on the cam disk support shaft 2, ^" as a result of which the width of the elevations 7 of the wedge-shaped arch profile 9 is deformed from an initial width d1, as shown in FIG. 15, to a width d2, as shown in FIG. 17. In this way, all the wedge-shaped arch profiles 9 of the cam disk support shaft 2 are compressed, the material being displaced into the recesses 8. While the cam disk support shaft 2 is plastically deformed in the joint surfaces within the areas wrapped by the bores 5 of the cam disks 3, effect the joining forces a substantially elastic expansion ^'of the cam plates 3. in this way, between each cam 3 and the portions 2a of the cam disk support shaft 2, a press fit, a.

At the same time, the torque introduced into the cam disk carrier shaft 2 during the joining by the drive wheel 4 causes a plastic deformation of that wave profile which is wrapped around by the drive wheel 4. Here, under the radial pressing pressure, the initial width of the elevations dl according to FIG. 14, like for the cam disks 3, also increases to the width d2 according to FIG. 16. In analogy to the widening of the cam disks 3, the bore 14 of the drive wheel 4 is also enlarged by the assembly torque elastically expanded. As already mentioned, the bore 14 of the drive wheel 4 generally has a greater radial expansion than the bores 5 of the cam disks 3. By means of the appropriate configuration of the geometry parameters, it is achieved that all non-circular shaft profiles deform at the same time during the assembly rotation movement through the angle 03. Appropriate measures should be taken to prevent the drive wheel 4 when joining under the action of the joining forces above the cam disk carrier. gerwelle 2 slipped.

After the predetermined angle of rotation 3 has been reached, the rotary control of the rotary device switches off the rotary movement of the drive wheel 4, as a result of which the assembly torque drops to zero. The cam disks 3 and the drive wheel 4 spring back in the radial direction and partially reduce their elastic expansion. They exert a permanent radial pressure on the plastically deformed camshaft carrier shaft 2, which releases the. individual joint connections of the cam disks 3 against the cam disk support shaft 2 and the drive wheel 4 against the cam disk support shaft 2 prevented. At the same time, the non-positive axial displacement locks are set for the cam disks 3 and the drive wheel 4.

The finished camshaft 1 is produced by the above-described joining machining, the bearing points 6 and the outer functional surfaces being able to be machined by known fine machining methods, for example by centerless cylindrical grinding for the bearing points 6 and by cam shape grinding for the outer contour of the joined cam disks 3.

In the state installed in the internal combustion engine, the camshaft 1 preferably has the same direction of rotation as the drive wheel 4 when it is mounted on the camshaft carrier shaft 2 under operating conditions. Accordingly, the transmission of the camshaft drive torque from the drive wheel 4 via the cam disk support shaft 2 to the cam disks 3 takes place in a form-fitting manner.

Alternatively to the described joining process, in which the drive wheel 4 is rotated relative to the cam disk support shaft 2, it would also be possible, any ^'cam to rotate. 3 Furthermore, the drive wheel could 4 and the cam disks 3 are connected individually to the cam disk support shaft 2, with monitoring of the applied torque being sensible in this context.

For clarification and for better understanding, the parameters in the figures, in particular the slope of the wedge-shaped arch profile 9, the division of the elevations 7 and the depressions 8, and the design of the tooth shapes have been chosen extremely. In practice, the deviation of the wedge-shaped arch profile 9 from the circular shape will be less, with a smaller difference of the largest radius of the sections 2a from the smallest radius, that is to say a smaller slope of the wedge-shaped arch profile 9, leading to better self-locking. However, the angle of rotation 03 can reach the size of 180 ° and more.

Claims

claims

Camshaft for an internal combustion engine with a cam disk support shaft on which a plurality of cam disks and a drive wheel are attached, the outer radius of the cam disk support shaft continuously changing in those sections in which the cam disks are attached, and the cam disks have a bore whose inner radius is continuous changed, characterized in that the cam disk support shaft (2) in those sections (2a), in which the ^• cam disks (3) are attached, is alternately provided with elevations (7) and depressions (8) over the circumference of the section ( 2a) of the cam disk support shaft (2) form a wedge-shaped curved profile (9), the elevations (7) continuously increasing the outer radius of the cam disk support shaft (2), that the bore (5) of the cam disks (3) corresponds to the enlargement of the outer radius of the cam disk support shaft ( 2) is adjusted, and that around the order catch the cam disc carrier shaft (2) and the bore (5) of the cam discs (3) exactly a wedge-shaped arc profile (9) is provided.

Camshaft according to claim .1, characterized in that the axial distance (a) of two adjacent cam Discs (3) is larger than the width (b) of a cam disc (3).

3. Camshaft according to claim 1 or 2, characterized in that the inner profile of the bore (5) of the cam discs (3) is mirror-inverted to the inner profile of a bore (14) of the drive wheel (4).

4. Camshaft according to claim 1, 2 or 3, characterized in that the cam disk carrier shaft (2) is designed as a solid shaft.

5. Camshaft according to claim 1, 2 or 3, characterized in that the cam disk carrier shaft (2) is designed as a hollow shaft, a mandrel being inserted into the hollow shaft for machining the cam disk carrier shaft (2).

6. Camshaft according to one of claims 1 to 5, characterized in that the depth of the recesses (8) increases continuously with the increase in the elevations (7).

7. Camshaft according to one of claims 1 to 6, characterized in that the wedge-shaped arc profile (9) is designed as an Archimedean or logarithmic spiral.

8. A method for producing a camshaft, in which a plurality of cam disks and at least one drive wheel are attached to a cam disk carrier shaft, characterized in that in those sections (2a) of the cam disk carrier gerwelle (2), on which the cam disks (3) are attached, alternately elevations (7) and depressions (8) are introduced in such a way that the circumference of / section (2a) of the cam disk support shaft (2) and the outer radius of the cam disk support shaft (2 ) continuously increasing wedge-shaped arc profile (9) as an envelope curve forms a hole (5) adapted to the enlargement of the outer radius of the ^" cam disk support shaft (2) in the cam disks (3), and that the cam disks (3) and the at least one Drive wheel (4) are attached to the cam disk carrier shaft (2) by mutual rotation, the cam disks (3) and the at least one drive wheel (4) and / or the cam disk carrier shaft _ (2) being elastically deformed.

9. The method according to claim 8> characterized in that when the ^• cam disks (3) and the at least one drive wheel (4) are attached to the cam disk support shaft (2), the cam disk support shaft (2) is plastically deformed, the cam disks (3) and the at least one drive wheel (4) is elastically expanded.

10. The method according to claim 8 or 9, characterized in that for the attachment of the cam disks (3) and the at least one drive wheel (4) ^" on the cam disk support shaft (2), the drive wheel (4) is rotated while the cam disks (3) in be held in a rigid position.

11. The method according to claim 8, 9 or 10, characterized in that the elevations (7) and the depressions (8) by means Cold forming can be introduced into the cam disc carrier shaft (2).

12. The method according to claim 11, characterized in that the elevations (7) and the depressions (8) are introduced into the cam disk carrier shaft (2) by means of two rod-shaped rolling tools (10, 11) which move relative to one another.

13. The method according to claim 11, characterized in that the elevations (7) and the depressions (8) by means of hammering in a die (13) are introduced into the cam disk support shaft (2).

14. The method according to any one of claims 8 to 13, characterized in that the cam discs (3). be made by forging.