WO2018228797A1 - Method and device for the impact treatment of transition radii of a crankshaft - Google Patents

Abstract

The invention relates to a method for the impact treatment of transition radii (8) of a crankshaft (4), in particular transition radii (8) between connecting rod bearing journals (5) and crank webs (7) and transition radii (8) between main bearing journals (6) and the crank webs (7) of the crankshaft (4). At least two impact tools (16) are used for the impact treatment. At least one of the impact tools (16) impact treats the transition radii (8) adjoining the connecting rod bearing journals (5), and at least one additional impact tool (16) impact treats the transition radii (8) adjoining the main bearing journals (6), wherein a sequence for the impact treatment of the transition radii (8) is designed such that concentricity errors of the crankshaft (4) are compensated for and/or are minimized.

Description

 Method and device for impact hardening Überqangsradien a crankshaft

The invention relates to a method for impact hardening of transition radii of a crankshaft, in particular of transition radii between connecting rod journal and crank webs and / or transitional radii between the main journal and the crank webs of the crankshaft according to the preamble of claim 1.

The invention also relates to an apparatus for carrying out the method for impact hardening of transition radii of a crankshaft.

The invention also relates to a crankshaft.

Due to the steadily progressing development and increase in the output of internal combustion engines and the strict emission requirements imposed on them, today's engines are increasingly being demanded as a result. For this reason, the engine industry, among other things high demands on the high-load and important for the function of an internal combustion engine crankshaft in terms of strength. In terms of design, there is often the requirement that the crankshaft should be light and the space requirement should be low. For the design of the crankshaft, this means that an increase in the load capacity should not be achieved by increasing the cross section, ie via the moment of resistance of the crankshaft, but if possible via local compressive residual stress states. For this reason, modern crankshafts are manufactured using a variety of machining and heat treatment processes, so that the crankshafts can be exposed to increasingly higher engine power. Examples of such processes are thermal treatments, such as induction hardening and case hardening, laser hardening or nitriding, as well as strain hardening processes such as deep rolling, shot peening or impact hardening. These are common and largely mature processes that are suitable for a variety of purposes. With regard to examples of such methods, reference is made to the following publications: EP 1 479 480 A1, EP 0 788 419 B1, EP 1 612 290 A1, DE 10 2007 028 888 A1 and EP 1 034 314 B1.

In particular, the impact hardening is an advantageous method for increasing the fatigue strength, in particular the bending fatigue strength and torsional fatigue, of crankshafts. The increase in fatigue strength is achieved in that impact forces are introduced into the claimed areas in cross-sectional transitions and changes in cross section by cold forming, preferably hammering by means of special impact tools in the crankshaft. As an example of such a method, reference is made to DE 34 38 742 C2 and EP 1 716 260 B1. In order to avoid an adverse introduction of concentricity errors by hammering, strict control procedures and highly qualified personnel are required to carry out the process. Further, a follow-up with corrective measures may be required to slightly correct the concentricity of the crankshaft after impact hardening if necessary. Although an optimal concentricity of the finished crankshaft can be basically guaranteed by the long-standing proven procedures, the mechanical and human effort to achieve this goal are relatively large. It would therefore be desirable to provide a method for impact hardening in which concentricity errors can be avoided with less effort. The object of the present invention is therefore to further develop the methods and devices for impact hardening in order to further improve the fatigue strength of crankshafts, in particular while avoiding concentricity errors.

This object is achieved for the method by the features listed in claim 1 and for the device for carrying out the method by the features listed in claim 12.

Finally, the invention is also based on the object of providing an improved crankshaft, in particular with respect to its fatigue strength and concentricity. With respect to the crankshaft, the object is achieved by the features listed in claim 13.

The dependent claims and the features described below relate to advantageous embodiments and variants of the invention. In the method according to the invention for impact hardening, it is provided that transition radii of a crankshaft, in particular transition radii between connecting rod journal and crank webs and / or transition radii, are impact-bonded between main bearing journal and the crank webs of the crankshaft. The connecting rod journal and the main journals are hereinafter referred to in part as "pin" for simplicity. The term journal may mean both the connecting rod journal and the main bearing journals, as well as only the connecting rod journal or only the main journals. Insofar as this is not explicitly stated otherwise, here all three variants are encompassed by the term pin. The invention is particularly preferably suitable for increasing the fatigue strength of, for example, crankshafts having a length of 0.2 to 8 m or more and / or main and connecting rod journal diameters of 30 to 500 mm or more. However, the invention is particularly suitable for increasing the fatigue strength of large crankshafts of 1, 5 to 8 m in length or more and / or main and connecting rod journal diameter of 100 to 500 mm or more. The crankshaft may have various types of transition radii, for example, fillets, for example, in a basket arch shape, or also undercut radii or radii with transitions. The transition radii can, for example, pass tangentially into the journal positions or running surfaces of the main and connecting rod journal.

This also applies to transitions to flanges, cones and other geometric cross-sectional changes - both tangent and deposited radii.

The crankshaft usually has transition radii at all transitions or cross-sectional changes. This is especially true for cross-sectional changes between journals and crank webs. For this purpose, the invention is particularly suitable. But transition radii can also for any other cross-sectional changes, in particular for changes in cross section at the end portions of the crankshaft, z. B. at a transition to a flange, a disc or a shaft, etc., may be provided. A transition radius, the fatigue strength of which is to be improved by the method according to the invention or the device according to the invention, does not necessarily have to be present between a connecting rod journal and a crank web or a main journal and a crank web, but can be arranged at any point of the crankshaft. The terms "connecting rod journal", "main journal", "flange", "pin" and / or "crank arm" can accordingly be reinterpreted by a person skilled in the art.

In the following, the invention will be described essentially on the basis of the hardening of transition radii between connecting rod journal and crank web and / or main journal and crank web. However, this is not restrictive and should only serve the better understanding or better readability. Insofar as reference is made to a transition radius in the context of the invention, this can basically be an arbitrary transition radius at any point of the crankshaft.

According to the invention, at least two impact tools are used for impact hardening. It is envisaged that at least one of the percussion tools impact-bonded the transition radii adjacent to the connecting rod journal and at least one other percussive impact-hardened the transition radii adjacent to the main journal, wherein a sequence for the impact hardening of the transition radii is determined such that concentricity error of the crankshaft balanced and / or minimized become. A sequence is to be understood as meaning the time sequence of impact hardening of the individual transition radii. It can be provided, for example, that all transition radii of the crankshaft are successively impact-solidified. It can, for. However, it may also be provided that two transition radii of the crankshaft are simultaneously impact-hardened, after which the next (for example two) transition radii of the crankshaft are impact-hardened or three transition radii of the crankshaft are simultaneously impact-hardened, after which the next transition radii of the crankshaft Thus, within the sequence, any number of transition radii can be impact-solidified simultaneously or sequentially-in any desired combinations-with the sequence being selected such that concentricity errors of the crankshaft are compensated and / or minimized.

The striking tools, which are used for impact hardening, bring a striking force into the respective transition radius during impact hardening.

The introduction of an impact force can be understood to mean that a striking head of a striking tool or a so-called "striker" of a striking device strikes against the region of the crankshaft to be consolidated, in the present case a transition radius. The impact takes place purposefully to the desired impact position along the annular radius around the pin circumferential transition radius.

The methods and devices according to the prior art provide that in the Schlagverfes- tion of the transition radii of the crankshaft basically all the transition radii successively, starting from a first end of the crankshaft toward a second end of the crankshaft, are impact-solidified, either only a single percussion tool is used or two striking tools, which, however, are only intended to simultaneously impact-strengthen two transition radii adjoining the same pin.

It has been found that this type of impact hardening is limited with respect to the maximum compressible compressive residual stress, since a deformation of the crankshaft, which leads to concentricity errors after compression, can be set if the respective impact forces are chosen too high. For this reason, the impact force is usually limited to ensure that little or no concentricity error occurs.

The inventors have realized that sufficient impact flexibility is provided by the use of at least two striking tools, wherein at least one of the striking tools for impact bonding of the connecting rod journal adjacent transition radii and at least one other impact tool for impact hardening of the main journal adjacent transition radii is used can be, whereby the sequence, with the impact-hardened, individually tuned to the respective crankshaft or the respective type of crankshaft that concentricity error of the crankshaft in the optimal case completely excluded and thus the cost of a later concentricity correction is minimized.

Due to the invention results from the reduction of processing steps and a cost-effective processing. In particular, a less machining for a compensation of the concentricity errors in the subsequent processing can be realized. The inventors have recognized that an improvement in the concentricity can occur in particular in that the compressive residual stresses are introduced in a flexible time sequence (eg "chaotic") distributed over the crankshaft. Finally, even higher compressive residual stresses or impact forces can be introduced into each individual transition radius than is possible with the known state of the art, since concentricity errors can be compensated for and / or minimized by a suitable sequence.

Finally, the process speed for the production of the crankshaft can be maximized, since concentricity errors are already avoided by a suitable sequence for the impact hardening of the transition radii, before they can even arise. The method according to the invention or the device according to the invention is thus particularly efficient and economical. At the same time crankshafts can be made with at least the same quality or robustness, as with the known methods of the prior art. The method according to the invention or the device according to the invention can also be used or used in crankshafts which have been previously processed to increase their fatigue properties by other methods. Thus, for example, a crankshaft which has been hardened by induction hardening can be subsequently improved with respect to its bending and torsional fatigue strength by introducing compressive residual stresses according to the method according to the invention or with the device according to the invention.

In one development of the invention, it can be provided that the sequence is determined on the basis of simulations, calculations and / or test series of the respective type of crankshaft. For example, an optimization of the sequence or of the method for impact hardening can take place by firstly producing a crankshaft of a specific type of crankshaft, after which the deformation or concentricity of the crankshaft is measured. In the course of producing a further crankshaft of this type of crankshaft, the sequence of impact hardening of the transition radii can then be varied, wherein after the production of this crankshaft, this is likewise measured with respect to deformation or concentricity. By comparing the crankshafts, the sequence for a crankshaft type can then be continuously optimized for concentricity errors on this basis.

If experiences, for example by simulations, calculations and / or test series, have already been collected with a crankshaft type, algorithms or calculations for transmitting the results to another type of crankshaft, in particular a similar crankshaft type, can also be provided. The sequence for optimum impact hardening to avoid concentricity error may also be the same or similar for crankshaft types of the same or similar configuration. In a further development of the invention, it can be provided that the sequence has a connecting rod bearing subsequence after which the transition radii of the connecting rod journal are first impact-hardened, after which the transition radii of the main journal are impact-hardened in a main bearing subsequence.

In an alternative development, it can be provided that the sequence has a main bearing subsequence, after which the transition radii of the main bearing journals are first impact-hardened, after which the transition radii of the connecting-rod journals are impact-hardened in a connecting-rod bearing subsequence.

Thus, a subsequence may be provided for each transition radius type. In principle, more than two subsequences can also be provided if there are more than two types of transition radii in the crankshaft which are to be impact-solidified successively. The order which type of transition radius is first impact-hardened can under certain circumstances sufficiently compensate for and / or minimize the problem of concentricity errors.

In one development of the invention, it may further be provided that the impact hardening according to the subsequences takes place in each case according to a fixed pattern, preferably according to one of the following schemes, according to which the respective transition radii of the crankshaft

 from a first end of the crankshaft toward a second end of the crankshaft or from the center of the crankshaft to the ends thereof or

 from the ends of the crankshaft to the center thereof

impact hardening, according to which the impact hardening according to the connecting rod bearing subsequence takes place according to another scheme than the impact hardening according to the main bearing subsequence.

It may therefore be provided, for example, all the radial radii of the connecting rod journal starting from the first end of the crankshaft in the direction of the second end of the crankshaft and all transition radii of the main journal, from the second end of the crankshaft to the first end of the crankshaft schlagzuverf estigen. This principle can also be transferred to any type of transition radii, in particular to transitions to flanges, pins and other geometric cross-sectional changes - both tangent and deposited radii.

For example, if the transition radii of a first type of transition radii, starting from the first end of the crankshaft to the second end of the crankshaft, are successively impact-solidified and the transition radii of another type of transition radii are impact-solidified successively along the opposite direction of the crankshaft, then possibly Compensate for deformation of the crankshaft advantageous, which can lead to a low concentricity error of the crankshaft. In a further development of the invention, however, provision can also be made for impact hardening to provide for at least one of the subsequences a scheme in which, at least in one case after impact hardening, a transition radius of at least one of the adjacent transition radii is skipped and, initially, a more distant transition radius is impact-hardened.

Such a "chaotic" scheme may be particularly advantageous in order to avoid concentricity errors of the crankshaft by targeted impact forces are introduced so that concentricity errors are compensated. Preferably, initially all transition radii of the connecting rod journal are chaotically impact-hardened and subsequently all the transition radii of the main bearing journal are chaotically impact-hardened - or vice versa.

In a further development of the invention, it can be provided that the sequence has at least one partial sequence which provides that one or more transition radii of the main bearing journals are impact-hardened, after which one or more transition radii of the connecting-rod journals are then impact-hardened and then again one or more transition radii of the Main bearing pins are impact-hardened. In a development of the invention it can also be provided that the sequences have at least one partial sequence which provides that one or more transition radii of the connecting rod journal are impact-hardened, after which one or more transition radii of the main journal are then impact-hardened and subsequently one or more transition radii of the connecting rod journal are impact strengthened.

A transition-type overlapping chaotic impact hardening is also possible. This also applies to transitions to flanges, cones and other geometric cross-sectional changes - both for tangent and deposited radii alike. In a preferred development of the invention, a sequence can be provided in which at least two transition radii are simultaneously impact-solidified.

Preferably, two transition radii adjoining the same pin are simultaneously impact-strengthened.

For example, when using the subsequences, it can be provided that, within a subsequence, several transition radii, in particular transition radii adjoining the same cones, are simultaneously impact-solidified. The subsequences can therefore also refer to groups of transitional radii. Even with a chaotic impact hardening it can be provided that at least two transition radii adjoining the same pin are simultaneously impact-hardened, after which one or more transition radii are subsequently skipped or become. In a further development, it may further be provided that three, four or more impact tools are used for impact hardening.

In principle, even more striking tools can be provided, for example five, six, seven, eight, nine, ten or even more striking tools.

It may be provided that a striking device is used for impact hardening, comprising a percussion piston, a deflection unit and at least one impact tool, wherein the at least one impact tool is attached to the deflection and wherein the percussion piston transmits a force impulse to the at least one impact tool via the deflection according to which the impact head of the at least one impact tool introduces the impact force into the transition radius.

Preferably, a beating device may be used which has two striking tools which are fastened to a common deflection unit. In particular, when using such a beater two adjacent to the same pin transition radii can be simultaneously impact strengthened.

Preferably, a plurality of such impact devices may be provided, in particular a striker for each type of transition radius, and most preferably a striker for impact hardening of transition radii adjacent to the connecting rod trunnions and another striker for impact hardening of transition radii adjacent to the main journal. For example, three, four, five or more impact devices may be provided, wherein the impact devices used also different configurations, eg. B. may have a different number of striking tools.

For example, a beating device can be provided with two striking tools as well as a further beating device with only one striking tool.

In particular, a percussion piston can be used which transmits a strong impulse or a force impulse (eg pneumatically, hydraulically and / or electrically generated) to the impact head.

Depending on the impact force, visible impact impressions of the impact head occur at the respective impact positions. The depth of the impact impressions and the quality or the depth effect of the inherent compressive residual stress depend on the selected impact force. The tool and the pro- Zessparameter are preferably matched to the respective crankshaft and thereby possibly to partial geometric changes (cross-sectional changes) exactly.

In a particular variant of the invention, provision can be made for different large impact forces to be introduced in at least two transitional radii during impact hardening.

By applying differently large impact forces in at least two transition radii, it is preferably understood that the difference between the impact forces is at least greater than a tolerance range which is typically present in the introduction of the impact forces in the prior art. The differently introduced impact forces preferably differ significantly. It can be provided, for example, that the impact forces which are introduced into the at least two transition radii differ by at least 2%, preferably by at least 5%, more preferably by at least 10% and most preferably by at least 30%.

The methods and devices according to the prior art provide that in the Schlagverfestigung the transition radii of the crankshaft in all transition radii, in particular in the transition radii between connecting rod journal and crank webs and the transition radii between main journals and crank webs, the same impact force is introduced. The impact force is chosen such that it is sufficient to bring sufficient compressive residual stresses in all to be solidified transition radii of the crankshaft.

With a uniform introduction of residual compressive stresses in all transition radii of the crankshaft no longer tolerable concentricity errors can be determined in the individual case after compression, if the impact force is set too high. Also for this reason, the impact force is often limited to ensure that no irreparable or undesirable concentricity errors occur.

The inventors have recognized on the basis of simulations and test series that the robustness or fatigue strength of the crankshaft can be achieved in a consistent - and sometimes even better - quality advantageous even when the impact forces are varied individually for different transition radii. As a result, critical concentricity errors can be completely excluded in the optimum case and thus the effort for a later concentricity correction can be minimized.

The inventors have recognized that an improvement of the concentricity does not occur exclusively because in now critical for the concentricity portions of the crankshaft or in transition radii of the crankshaft compared to other sections now also reduced impact force can be introduced, but in particular also because The residual compressive stresses can now be distributed differently over the crankshaft, but in each case the minimum required residual compressive stresses are introduced in each transition radius. Very particularly advantageous concentricity errors of the crankshaft can be compensated and / or minimized if the sequence and the impact forces to be introduced into the individual transition radii are each adapted or determined jointly for the corresponding type of crankshaft. In a variant of the invention can be provided that the same impact force is introduced in two adjacent to the same connecting rod journal transition radii.

Alternatively or additionally, it can also be provided in a variant of the invention that the same impact force is introduced in two transition radii adjoining the same main journal.

Finally, it may alternatively or additionally be provided that in two adjacent or adjacent transition radii regarding transitions to flanges, cones and other geometric cross-sectional changes - both tangential and deposited radii - the same impact force is introduced.

In particular, it may thus be advantageous if the impact force between two adjacent to the same pin transition radii is not varied.

It can be defined groups of transition radii, in which the same impact force is introduced. For example, two transition radii adjoining the same pin can each form a group.

In this way, residual compressive stresses can be symmetrically introduced into the transition radii of certain cones, while viewed via the crankshaft, however, the impact forces introduced into the transition radii can be varied. This has proven to be particularly advantageous.

In one embodiment of the variant may also be provided that in the transition radii of at least two main journals, preferably in the transition radii of all main journals, the same impact force is introduced.

In an alternative or additional embodiment of the variant of the invention may finally be provided that in the transition radii of at least two connecting rod journal, preferably in the transition radii of all connecting rod journal, the same impact force is introduced.

This also applies to transitions to flanges, cones and other geometric cross-sectional changes - both tangent and deposited radii.

One possibility for forming groups of transition radii, in which the same impact force is introduced, can thus also result from the fact that the transition radii of all main journals a Form a group. The transition radii of all connecting rod trunnions may optionally form a group.

The inventors have recognized that in order to avoid concentricity errors, it may be advantageous to introduce the same impact force in all transition radii of the main journal and in all transition radii of the connecting rod journal, wherein the impact force which is introduced into the transition radii of the main journal, in this case of the impact force, which is introduced into the transition radii of the connecting rod journal, differs.

In a variant of the invention, however, can also be provided that in the transition radii of a first connecting rod journal a first impact force and in the transition radii of a second connecting rod journal a second (deviating from the first impact) impact force is introduced. Optionally, an individual impact force can be introduced into the transition radii of each connecting rod journal.

Alternatively or additionally, in one embodiment, it may also be provided that a first impact force is introduced into the transition radii of a first main journal and a second impact force (deviating from the first impact force) is introduced into the transition radii of a second main journal. Optionally, an individual impact force can be introduced into the transition radii of each main journal.

This also applies to transitions to flanges, cones and other geometric cross-sectional changes - both tangent and deposited radii.

In particular based on calculations, simulations and / or test series of the corresponding crankshaft type, the impact forces can thus be determined individually for each transition radius. In this case, optimally suitable impact forces and impact patterns can result for each transition radius or at least for different groups of transition radii, wherein concentricity errors can be further suppressed or compensated. Furthermore, the fatigue strength of the crankshaft by this measure even exceed the requirements. This is especially true because at the same time the sequence can be optimized for impact hardening.

In one embodiment of the invention may be provided in particular that a base value for the forces to be introduced into the transition radii impact forces is determined based on the desired fatigue strength of the Kur- shaft and / or based on the desired fatigue strength of portions of the crankshaft.

For example, a base value for the entire crankshaft, which may be a minimum impact force, may be determined at which time the desired fatigue strength is achieved in all Sections of the crankshaft is still guaranteed, or preferably with the addition of a safety margin.

However, it can also be provided that the basic value is determined individually for different sections of the crankshaft, such that the desired fatigue strength of the crankshaft is ensured in the respective sections, preferably with the addition of a safety margin. For example, a base value for end portions or end portions of the crankshaft, a base value for a central portion of the crankshaft, a base value for all main journals, a base value for all connecting rod journals and / or a base value for other portions of the crankshaft can be determined. In particular, a plurality of base values may also be provided.

The base value can also be chosen such that it is a defined percentage, for example 10% to 50%, preferably 20% to 40%, greater than the minimum impact force necessary for the crankshaft or the crankshaft range, so that the base value decreases can be adjusted up and down to impact hardening the transition radii.

In an embodiment of the variant, it can be provided that the base value is varied by an equalization value in order to compensate, avoid and / or minimize concentricity errors of the crankshaft. If a baseline value higher than a minimum value is determined for the impact forces to be introduced into the transition radii (for example by adding at least one margin of safety), the base value can be individually varied by particular compensation values for individual transition radii, in particular increased the minimum value of the impact force to reach the desired fatigue strength at a transition radius is not exceeded. The compensation value can therefore be used specifically to avoid or compensate for concentricity errors.

Thus, the fatigue strength of the crankshaft and the concentricity of the crankshaft can be adjusted almost independently. It can be provided, for example, that all transition radii of the connecting rod journals are impact-bonded to the base value, and all transition radii of the main journals are impact-hardened with the base value varied by the compensation value, for example a 1 10% value or 90% value based on the base value , Alternatively, it can also be provided that all main bearing journals are impact-hardened with the base value and all connecting rod journals are impact-hardened with the base value varied by the compensation value.

In one embodiment of the invention can also be provided that the compensation value for several, preferably for each transition radius, is determined individually to compensate for runout of the crankshaft, to avoid and / or minimize. In one embodiment of the invention, provision can be made in particular for the compensation value to be at most 30%, preferably at most 15%, particularly preferably at most 5%, of the base value. It may also be provided that the equalization value is a maximum of 30%, but not less than 20%, not more than 20%, but not less than 15%, not more than 15%, but not less than 10%, or not more than 10%, but not less than 5% of the underlying.

A position control can be used to rotate the crankshaft step by step from one stroke position to the next stroke position. In the simplest case, a PTP control or point control can be provided for this purpose.

To rotate the crankshaft, a drive device may be provided which comprises a motor, in particular an electric motor. In principle, the electric motor can be any electric motor, for example a three-phase motor (in particular a three-phase asynchronous machine), an AC motor, a DC motor or a universal motor.

Preferably, a stepper motor can be used.

It may also be provided a two-part drive means, in which, for example, an engine is provided at each end of the crankshaft, d. H. a synchronous drive or double-sided drive of the crankshaft. Usually, the crankshaft is rotatably fixed for the processing thereof via a fastening device on a drive shaft.

It may also be provided a support in the manner of a tailstock to rotatably support or fix the crankshaft at its end remote from the drive means end.

It can be provided that the striking tools with a periodicity, preferably with a beat frequency of 0.5 Hz to 30 Hz, more preferably with a clock of 0.5 Hz to 5 Hz and most preferably with a clock of 0 , 5 Hz to 3 Hz, perform a flapping motion or bring in the impact force.

Of course, other timings, for example, beat frequencies between 0.1 Hz and 50 Hz, may be provided, but the above values are particularly suitable. The impact pressures, which are converted by the percussion piston to the impact force, depending on the operation - between 10 and 300 bar, preferably between 30 and 180 bar, and more preferably between 50 and 130 bar, amount. The impact force can therefore be specified by setting a corresponding impact pressure (the percussion piston). In the sense of the variant of the invention, it can thus also be provided that a different impact pressure is used for impact hardening of at least two transition radii. Thus, for example, at least one base value and at least one compensation value related to the impact pressure may also be provided.

The temperature in the region of the crankshaft segment or transition radius to be machined should preferably not be higher than 65 ° C; values between 12 ° C and 25 ° C are preferred.

Experience has shown that after dynamic loading in the engine or on the test bench crankshafts can get non-propagating microcracks on the surfaces. These microcracks have no effect on the fatigue properties, but they can disturb the visual appearance.

Since the introduction of compressive residual stress can preferably take place to a depth of 15 mm, but even deeper, this means that in the surface region of the crankshaft, a removal of a few millimeters, for example from 0.1 to 3 mm, preferably 0.5 mm , without the flexural and torsional fatigue or the fatigue strength of the crankshaft suffers.

Investigations have shown that such measures can even slightly increase fatigue strength, for example by up to 5%.

The removal of the surface can be done in various ways, such as by grinding, turning, milling, turn milling, peeling or polishing. The invention also relates to a device for carrying out a method described above for impact hardening of transition radii of a crankshaft, in particular of transition radii between connecting rod journal and crank webs and / or transition radii between the main journal and the crank webs of the crankshaft. The device is also suitable for impact hardening of transitions to flanges, cones and other geometrical cross-sectional changes - both tangent and deposited radii.

Features that have already been described in connection with the method according to the invention are of course also advantageous for the device according to the invention implemented - and vice versa. Furthermore, advantages which have already been achieved in connection with the method according to the invention can be achieved. were called, are also based on the device according to the invention understood - and vice versa.

In principle, some of the components of the device according to the invention may correspond in their construction to the device according to EP 1 716 260 B1, for which reason the disclosure content of EP 1 716 260 B1 is completely integrated into the present disclosure by referencing.

The invention also relates to a computer program with program code means in order to carry out the method according to the invention when the program is executed on a control and / or regulating device, in particular on a microprocessor.

The invention also relates to a crankshaft manufactured according to a method described above. The crankshaft according to the invention differs from conventional crankshafts in particular in that during the impact hardening a specific sequence or sequence was used when introducing the internal compressive stresses into the transition radii. As a result, a characteristic hardening of the transition radii of the crankshaft and a characteristic deformation or a characteristic concentricity of the crankshaft can result overall. Furthermore, the crankshaft may differ from conventional crankshafts in that different strengths of impact force have been introduced into at least two transition radii for their solidification according to a variant of the invention.

Embodiments of the invention will be described in more detail with reference to the drawing.

The figures each show preferred embodiments in which individual features of the present invention are illustrated in combination with each other. Features of an exemplary embodiment can also be implemented independently of the other features of the same exemplary embodiment and can accordingly be easily connected by a person skilled in the art to further meaningful combinations and subcombinations with features of other exemplary embodiments.

In the figures, functionally identical elements are provided with the same reference numerals.

They show schematically:

1 shows an overall view of a device according to the invention for carrying out the method of a first embodiment;

FIG. 2 shows a perspective view of a part of the device according to the invention for carrying out the method in a second embodiment; FIG. 3 shows a striking device with two impact tools in an enlarged view according to detail "A" of Fig. 1.

4 a striking device with only one impact tool;

5 shows an exemplary crankshaft and its striking hardening with two impact devices;

 and

6 shows an exemplary detail of a crankshaft and a force diagram.

The device shown in Figure 1 in an overall view basically corresponds in its structure to the devices according to DE 34 38 742 C2 and EP 1 716 260 B1 with one or more impact devices 1, which is why hereinafter only on the essential parts and on the differences to the prior Technology is discussed in more detail.

The device has a machine bed 2 and a drive device 3. The drive device 3 is used to bring or rotate a crankshaft 4 along a direction of rotation in an impact position.

The crankshaft 4 has connecting rod journal 5 and main journal 6, between which each crank webs 7 are arranged on. Transverse radii 8 (cf., FIGS. 3 to 6) are formed between connecting rod journal 5 and crank webs 7 and between main bearing journal 6 and crank webs 7 or generally between cross-sectional transitions of crankshaft 4.

On the side facing the drive device 3 side of the crankshaft 4, a fastening device 9 is provided, which has a clamping disk or a mounting flange 10. On the side facing away from the drive device 3 side of the crankshaft 4, a support 1 1 is preferably provided in the manner of a tailstock, which has a further fastening means 9 to receive the crankshaft 4 rotatable bar or rotatable set. Optionally or in addition to the support 1 1, a Lü- nice, which is positioned at a rotationally symmetrical location, may be provided.

The drive device 3 is able to set the crankshaft 4 along a rotation axis C in a rotational movement. It can be provided that the main axis of rotation C _K w of the crankshaft 4 is positioned off-center of the axis of rotation C of the drive device 3, as shown in Figure 1 and Figure 2.

For this purpose, alignment means 17 (cf., FIG. 2) may preferably be provided in the region of the fastening device 9. It can be provided that the alignment means 17 a center axis of each to be solidified pin 5, 6 shift so that the central axis of the pin 5, 6 is located on the axis of rotation C. For the drive device 3, a direct drive, preferably without a clutch, can be provided. An engine, preferably an electric motor, of the drive device 3 can thus be mechanically coupled without transmission or transmission to the fastening device 9 or to the crankshaft 4. The impact devices 1 described in more detail below by way of example are each held adjustably in a displacement and adjusting device 15 in order to adapt them to the position of the connecting rod journal 5 and the main bearing journal 6 and to the length of the crankshaft 4.

The support 1 1 can also be arranged to be displaceable, as indicated by the double arrows in FIG.

In the method according to the invention for impact hardening it is provided that at least two impact tools 16 are used, wherein at least one of the impact tools 16 impact-bonded the transition radii 8 adjacent to the connecting rod journal 5 and at least one further impact tool 16 impact-solidifies the transition radii 8 adjacent to the main journal 6, wherein a Sequence for the impact hardening of the transition radii 8 is determined such that concentricity errors of the crankshaft 4 are compensated and / or minimized.

It is also possible to use more than two impact tools 16, for example three, four or more impact tools 16 for impact hardening.

In the figure 1, two impact devices 1 are shown, but in principle any number of impact devices 1 may be provided, according to the invention at least one impact tool 16 for impact hardening of the transition radii 8 of the main bearing pin 6 and a percussion tool 16 for impact hardening of the transition radii 8 of the connecting rod journal 5 is provided ,

It can be provided in particular that at least one impact device 1 is designed and set up for impact hardening of the transition radii 8 of the main bearing journals 6 and a

Impact device 1 for impact hardening of the transition radii 8 of the connecting rod journal 5 is formed and arranged, as shown in Figure 1.

In a variant of the invention it can be provided that in at least two transition radii 8 different impact forces F _{s are} introduced. The inventors have recognized that especially when an optimized sequence and simultaneously different impact forces F _s are used, concentricity errors of the crankshaft 4 can be avoided or compensated.

FIG. 2 is a fragmentary perspective view of a further device for carrying out the method according to the invention, but without a beating device. The device of FIG. 2 is essentially identical to the device of FIG. 1, for which reason reference will be made below only to the essential differences in detail. Again, a drive device 3 is provided. Further, a fastening device 9 is provided which has a mounting flange 10 and an attached face plate with clamping jaws for fixing the crankshaft 4. The face plate with the clamping jaws of the fastening device 9 is adjustably arranged on the mounting flange 10 on an alignment means 17, whereby the longitudinal axis C _K w of the crankshaft 4 can be displaced relative to the axis of rotation C of a drive shaft or an input shaft 13.

The crankshaft 4 of FIG. 2 has a configuration differing from that shown in FIG. 1, but basically also includes connecting rod journal 5, main bearing journal 6 and crank webs 7.

In Figure 2 (as well as in Figure 1) can be provided at the end remote from the drive means 3 end of the crankshaft 4, a further fastening means 9, but this can also be omitted.

FIG. 3 shows, by way of example, a beating device 1 of FIG. 1 in greater detail. The invention can in principle be implemented with any impactor 1. However, the impact device 1 described below is particularly suitable. It has a base body 18 which can be provided with a prismatic system according to the radius of the crankshaft segment to be machined and preferably has guides 19 which guide two striking tools 16 in their support plane and give them a corresponding freedom about a deflection unit 20 for adaptation to the dimensional conditions of the crankshaft 4 is advantageous. At the front ends of the two impact tools 16 each have a ball is arranged as a striking head 21. An intermediate part 22 establishes the connection between a percussion piston 23 and the deflection unit 20, which transmits the impact energy to the impact tools 16. The intermediate part 22 may optionally be omitted.

It can be provided that in two adjacent to the same connecting rod journal 5 transition radii 8, the same impact force F _{s is} introduced. Alternatively or additionally, it may be provided that the same impact force F _{s is} introduced in two transition radii 8 adjoining the same main journal 6. But it can also be provided in principle that in all transition radii 8, the same impact force F _{s is} introduced.

A beating device 1 shown in FIG. 3 is particularly suitable for this purpose. It can also be provided that a beating device 1 with two impact tools 16 is configured such that the impact tools 16 introduce a respective different impact force F _s into the transition radii 8 adjoining the same journal 5, 6. To increase the effectiveness of the impact, a clamping prism 24 can be fastened by means of springs 25 with adjustable clamping bolts 26 with clamping nuts 27 on the side of the journal 5, 6 facing away from the main body 18. Here are also other constructive solutions possible. It should be understood that should part of the description "impact tool" or "a

Basically any number of striking tools, for example two, three, four, five, six, seven, eight, nine, ten or more may be meant or singular is for readability only and not restrictive.

By arranging a plurality of impactors 1 or striking tools 16 over the length of the crankshaft 4 to be machined, all centric and optionally eccentrically extending portions of the crankshaft 4 can be machined simultaneously if required. The percussion piston 23 transmits a force impulse to the percussion tools 16 via the deflecting unit 20, whereafter the striking heads 21 of the percussion tools 16 introduce the striking force F _s into the transition radii 8.

The term "F _s " and similar expressions in the present specification are to be construed only as placeholders / variables for any impact force deemed appropriate by the skilled person. If reference is made in the description to "the striking force F _s ", it can thus be in each case different or even identical impact forces.

FIG. 4 shows a striking device 1, which is provided with only one striking tool 16. In the illustrated embodiment, the impactor 1 is preferably inclined to the crankshaft 4, in such a way that the impact tool 16 which is arranged coaxially to the longitudinal axis of the impactor 1, perpendicular to the region of the crankshaft segment to be machined, in this case the transition radius to be machined 8, incident. Although only one crankshaft segment can be machined in this case, on the other hand the structural design and the power transmission of the impact device 1 are better and simpler for this purpose. In addition, bore ends can be solidified with this tool standing.

This embodiment proves to be particularly advantageous for use on non-symmetrical crankshaft segments, such as the end regions and the oil bore ends of the crankshaft 4.

The design of the beating device 1 shown in Figure 4 with only a percussion tool 16 is also particularly suitable when the same pin 5, 6 adjacent transition radii 8 are to be impact-solidified with different degrees of impact F _s . The striking devices 1 shown in FIG. 1 or basically the beating devices 1 used for the invention may be a beating device 1 according to FIG. 3 or according to FIG. 4 or any other beating device 1 in any combination. According to the invention, it is important that at least one impact tool 16 is used for impact hardening of the transition radii 8 adjoining the connecting rod journal 5 and at least one further impact tool 16 for impact hardening of the transition radii 8 adjoining the main bearing journal 6.

It can be provided that the sequence for impact hardening is determined on the basis of simulations, calculations and / or test series of the respective type of crankshaft.

It can be provided in particular that at least two transition radii 8 are simultaneously impact-solidified, for example with a beating device 1 with two striking tools 16 according to FIG. 3.

FIG. 5 shows an exemplary crankshaft 4 with respective transition radii 8 between connecting rod journal 5 and crank web 7 or main journal 6 and crank web 7 and further cross-sectional transitions with transition radii 8. Two impact devices 1 in a configuration with two striking tools 16 according to FIG. 3 are indicated schematically by way of example. The crankshaft 4 has a first end Ei and a second end E ₂ .

It may be provided that the sequence for impact hardening has a connecting rod bearing subsequence A, after which first the transition radii 8 of the connecting rod journal 5 are impact-hardened, after which the transition radii 8 of the main bearing pins 6 are impact-strengthened in a main bearing subsequence B. This is shown in Figure 5 by corresponding arrows. According to this development, the conrod bearing pin 5 associated impact device 1 (in the top left of Figure 5) along the length of the crankshaft 4 is moved from left to right to successively schlagzuverfestigen all connecting rod journal 5. Within the connecting rod bearing subsequence A, it can be provided in principle that all transition radii 8 of the connecting rod journal 5 are simultaneously impact-hardened, for example by a striking device 1 with a correspondingly large number of impact tools 16 or by a correspondingly large number of individual impact devices 1, each with one or more striking tools 16. Within the connecting rod bearing subsequence A, any number of transition radii 8 of the connecting rod journal 5 can be impact-solidified simultaneously and / or sequentially.

After a striking hardening according to the first connecting rod bearing subsequence A, the transition radii 8 of the main bearing journals 6 can then be impact-hardened in accordance with the second main bearing subsequence B. For this purpose, the impact device 1, which is assigned to the transition radii 8 of the main bearing journals 6 (in FIG. 5, the impact device 1 at the bottom right), can be moved from right to left of main bearing journals 6 are moved to main journal 6 to successively beat each two transition radii 8 of the main journals 6. Of course, in the second main bearing subsequence B, any number of transition radii 8 of the main bearing journals 6 can be impact-strengthened simultaneously and / or successively with any number of impact devices 1 and / or impact tools 16.

The order described above may also be reversed. That is, the subsequence provided first would be the main stock subsequence B, as shown in FIG. 5, and the subsequence provided below is the conrod subsequence A.

In particular, it can be provided that the impact hardening according to the subsequences A, B takes place in each case according to a defined scheme, preferably according to one of the following schemes described. For example, from the first end Ei of the crankshaft 4 toward the second end E _{2 of} the crankshaft 4 or from the center M of the crankshaft 4 to the ends E _1: E ₂ or from the ends E _1: E _{2 of} the crankshaft 4 to whose center M are impact-strengthened, after which the impact hardening according to the connecting rod bearing subsequence A takes place according to a different scheme than the impact hardening according to the main bearing subsequence B.

As shown by way of example in FIG. 5, a scheme is provided for the connecting rod bearing subsequence A, according to which the crankshaft 4 is impact-hardened by the first end Ei of the crankshaft 4 in the direction of the second end E ₂ , whereas the main bearing subsequence B is designed is to schlagzuverfestigen of the second end E _{2 of} the crankshaft 4 in the direction of the first end Ei of the crankshaft 4.

For clarification, positions P 1 to P _{14 of} the crankshaft 4 are marked in FIG. Thus, the percussion device 1 of the transitional radii 8 at the positions P ^ and P ₂ may, for example, in a scheme of connecting rod bearing subsequence A subsequent to the transition radii 8 at positions P ₅ and P _6, subsequently to the transition radii 8 at positions P ₉ or P ₁₀ and finally to the transition radii 8 of the positions P ₁₃ and P _{14 are} moved. In the scheme of the main bearing sub-sequence B, it may be provided, for example, that the impactor 1 of the transition radii 8 at the positions P and P ₁₂ following the transition radii 8 at the positions P ₇ and P ₈ and finally to the transition radii 8 the positions P ₃ and P _{4 is} moved.

It can also be provided that the striking hardening according to at least one of the subsequences A, B provides a scheme in which at least in one case after impact hardening of a transition radius 8 at least one of the adjacent transition radii 8 is skipped and initially a further away transition radius 8 is impact-strengthened. For example, regarding the connecting rod bearing subsequence A, the transition radii 8 at the positions P and P _{2 could be} simultaneously simultaneously or successively impact-hardened, after which the transition radii 8 are simultaneously impact-hardened at the positions P ₁₃ and P ₁₄ , after which the transition radii 8 of the middle Pleuellagerzapfen 5 at the positions P ₅ and P ₆ or P ₉ and P _{10 are} simultaneously or successively impact-solidified. Such a "chaotic" impact hardening can also be provided analogously for main bearing subsequence B during impact hardening of the transition radii 8 of the main bearing journals 6.

It can also be provided that the sequence has at least one partial sequence which provides that one or more transition radii 8 of the main bearing journals 6 are impact-hardened, after which one or more transition radii 8 of the connecting rod journals 5 are subsequently impact-hardened and then again one or more transition radii 8 Main bearing pin 6 impact-strengthened.

It can also be provided that the sequence has at least one partial sequence which provides that one or more transition radii 8 of the connecting rod journals 5 are impact-hardened, after which one or more transition radii 8 of the main bearing journals 6 are subsequently impact-strengthened and then again one or more transition radii 8 of the connecting rod journal 5 are impact-strengthened.

The temporal sequence in the course of the subsequences A, B can thus also overlap or interleave. For example, the impactor 1, which is assigned to the connecting rod journal 5, are first used to schlagzuverf the transition radii 8 at the positions or P ₂ , after which the impactor 1, which is associated with the main journal 6 is used to the transition radii eighth at the positions P ₃ and P ₄ impact, after which the impactor 1, which is assigned to the connecting rod journal 5, is subsequently used again to schlagzuverfestigen one or more transition radii 8 of the connecting rod journal 5, etc.

It is understood that the subsequences A, B or subsequences, etc., which are designated in the course of the description of FIG. 5, are to be understood as purely exemplary. Any desired sequences of impact hardening of the transition radii 8 can be provided with any desired number of impact devices 1 or striking tools 16 in order to compensate and / or minimize concentricity errors of the crankshaft 4. The corresponding sequence can be determined in accordance with the type of crankshaft to be consolidated.

FIG. 6 shows an exemplary detail of a crankshaft 4 with respective transition radii 8 between connecting rod journal 5 and crank webs 7 and main journal 6 and crank webs 7.

It can be provided that the same impact force F _{s is} introduced into the transition radii 8 of at least two main bearing journals 6, preferably into the transition radii 8 of all main bearing journals 6. Alternatively or additionally, it may be provided that the same impact force F _{s is} introduced into the transition radii 8 of at least two connecting rod journal 5, preferably into the transition radii 8 of all connecting rod journal 5. Finally, it can also be provided that in the transition radii 8 of a first connecting rod journal 5, a first impact force F _s and in the transition radii 8 of a second connecting rod journal 5, a second impact force F _{s is} introduced. Optionally, an individual impact force F _{s is} introduced into the transition radii 8 of each connecting rod journal 5.

Alternatively or additionally, it may be provided that in the transition radii 8 of a first main journal 6, a first impact force F _s and in the transition radii 8 of a second main journal 6, a second impact force F _{s is} introduced. Optionally, an individual impact force F _{s is} introduced into the transition radii 8 of each main bearing journal 6.

It can be provided that an underlying value F ₀ for the impact forces F _s to be introduced into the transition radii 8 is determined on the basis of the desired fatigue strength of the crankshaft 4 and / or on the basis of the desired fatigue strength of sections of the crankshaft 4.

It may further be provided that the base value F ₀ is varied by a compensation value F _{A in} order to compensate, avoid and / or minimize concentricity errors of the crankshaft 4.

FIG. 6 schematically shows a force diagram for this purpose. It can be seen that the impact force F _{s is} based on a base value F _0, on the basis of which the compensation value F _A effects an additive or subtractive modification. The base value F ₀ and the compensation value F _A are selected such that a minimum impact force F _min , which is required at the respective transition radius 8, is not exceeded. Preferably, a safety margin is additionally provided. It can be provided that the compensation value F _{A is} determined individually for a plurality (preferably for each) transition radius 8 in order to compensate, avoid and / or minimize concentricity errors of the crankshaft 4. FIG. 6 shows the situation or the force diagram only as an example for a transition radius 8. However, this is not meant to be limiting. In particular, it can be provided that the compensation value F _{A is} at most 30%, preferably at most 15%, particularly preferably at most 5% of the base value F ₀ .

It may further be provided that the compensation value F _{A is} at most 30%, but at least 20%, at most 20%, but at least 15%, at most 15%, but at least 10%, or at most 10%, but at least 5%, of the underlying F ₀ is.

Claims

 P a n t a n s p r e c h e Method for impact hardening of transition radii (8) of a crankshaft (4), in particular of transition radii (8) between connecting rod journal (5) and crank webs (7) and transition radii (8) between main bearing journal (6) and the crank webs (7) of the crankshaft (4 ), characterized in that at least two impact tools (16) are used for impact hardening, wherein at least one of the impact tools (16) impact-bonded the transition radii (8) adjacent to the connecting rod journal (5) and at least one further impact tool (16) the transition radii (B) adjacent the main bearing journal (6). 8), wherein a sequence for the impact hardening of the transition radii (8) is determined such that concentricity errors of the crankshaft (4) are compensated and / or minimized. Method according to claim 1, d a d u r c h e c e n c i n e s that the sequence is determined on the basis of simulations, calculations and / or test series of the respective crankshaft type. Method according to claim 1 or 2, d a d u r c h e c e n c i n e s that the sequence comprises a connecting rod bearing subsequence (A), after which first the transition radii (8) of the connecting rod journal (5) are impact-hardened, after which the transition radii (8) of the main bearing pins (6) are impact-hardened in a main bearing subsequence (B). Method according to claim 1 or 2, d a d u r c h e c e n c i n e s that the sequence comprises a main bearing subsequence (B), after which first the transition radii (8) of the main bearing journals (6) are impact hardened, after which the transition radii (8) of the connecting rod journals (5) are impact hardened in a connecting rod bearing subsequence (A). Method according to claim 3 or 4, d a d u r c h e c e n c i n e s that the impact hardening according to the subsequences (A, B) takes place in each case according to a fixed pattern, preferably according to one of the following diagrams, according to which the respective transition radii (8) of the crankshaft (4) from a first end (E 1) of the crankshaft (4) towards a second end (E ₂ ) of the crankshaft (4) or from the center (M) of the crankshaft (4) to its ends (E _1: E ₂ ) or from the ends (E _1: E ₂ ) of the crankshaft (4) to its center (M) impact hardening, according to which the impact hardening according to the connecting rod bearing subsequence takes place according to a different scheme than the impact hardening according to the main bearing subsequence (B). Method according to claim 3 or 4,  d a d u r c h e c e n c i n e s that  the impact hardening according to at least one of the subsequences (A, B) provides a scheme in which, at least in one case after impact hardening, a transition radius (8) of at least one of the adjacent transition radii (8) is skipped and at first a more distant transition radius (8) is impact-hardened , Method according to one of claims 1 to 6,  d a d u r c h e c e n c i n e s that  the sequence comprises at least one subsequence, which provides that one or more transition radii (8) of the main bearing journals (6) are impact-hardened, after which one or more transition radii (8) of the connecting-rod journals (5) are impact-hardened and then again one or more transition radii ( 8) of the main bearing journals (6) are impact-hardened. Method according to one of claims 1 to 6,  d a d u r c h e c e n c i n e s that  the sequence comprises at least one subsequence, which provides that one or more transition radii (8) of the connecting rod journals (5) are impact-hardened, after which one or more transition radii (8) of the main journals (6) are impact-hardened and then again one or more transition radii ( 8) of the connecting rod journal (5) are impact-hardened. Method according to one of claims 1 to 8,  d a d u r c h e c e n c i n e s that  the sequence provides that at least two transition radii (8) are simultaneously impact-solidified. 10. The method according to any one of claims 1 to 9,  d a d u r c h e c e n c i n e s that  three, four or more impact tools (16) are used for impact hardening. 11. The method according to any one of claims 1 to 10,  d a d u r c h e c e n c i n e s that in at least two transition radii (8) impact strengths (F _s ) of different sizes are introduced during impact hardening. Device for carrying out the method for impact hardening of transition radii (8) of a crankshaft (4), in particular of transition radii (8) between connecting rod journal (5) and crank webs (7) and transition radii (8) between main bearing journal (6) and the crank webs (7) the crankshaft (4), according to one of claims 1 to 1 1. Crankshaft (4), produced by a method according to one of claims 1 to 1 1.