Method and device for post-processing a crankshaft

Abstract

The invention relates to a method for post-processing a crankshaft (4), in particular in order to correct concentricity errors and/or for a length correction. Sectors (S1,S2,S3,S4,S5,S6) of the crankshaft (4) which produce and/or characterize concentricity errors are detected and/or a length deviation (ΔL1 ΔL2, ΔL3) from a target length (L1,L2, L3) is determined for at least one section of the crankshaft (4). An impact force (Fs) is then introduced into at least one defined transition radius (8) between connecting rod bearing journals (5) and crank webs (7) and/or between main bearing journals (6) and the crank webs (7) of the crankshaft (4) by means of at least one impact tool (16) in order to correct the concentricity errors and/or the length deviation (ΔL1 ΔL2, ΔL3).

Claims

1. A method for the post-processing of a crankshaft for the purposes of correcting concentricity errors and/or for the purposes of length correction, the method comprising the following steps: determining concentricity errors for sectors of the crankshaft and/or determining a length deviation from a setpoint length for at least one portion of the crankshaft; introducing an impact force for correcting the concentricity errors and/or the length deviation into at least one defined transition radius between connecting-rod bearing journals and crank webs and/or between main bearing journals and the crank webs of the crankshaft by means of at least one impact tool; and hardening the transition radii of the crankshaft prior to the determination of the concentricity errors and/or the determination of the length deviation, wherein the portion of the crankshaft in which the length deviation from the setpoint length is determined corresponds to a spacing between two crank webs.

2. The method as claimed in claim 1, wherein the at least one impact tool introduces an impact force for correcting the concentricity errors and/or the length deviation into highly loaded regions of the defined transition radii.

3. The method as claimed in claim 1, wherein the only transition radii situated in the sectors which cause the concentricity errors are selected as defined transition radii.

4. The method as claimed in claim 1, wherein, for the correction of the length deviations, an impact force is introduced into all transition radii of the crankshaft by means of the at least one impact tool.

5. The method as claimed in claim 1, wherein the nature of the concentricity error is determined based on whether a concentricity error in the end sections of the crankshaft is present, wherein the defined transition radii are selected on the basis of the nature of the concentricity error.

6. The method as claimed in claim 1, wherein the defined transition radii are determined on the basis of simulations of a respective crankshaft type.

7. The method as claimed in claim 1, wherein, for at least one further shape and/or position specification, a deviation from a nominal dimension is determined, following which an impact force for correcting the at least one further deviation is introduced into at least one defined transition radius between one of the connecting-rod bearing journals and one of the crank webs and/or between one of the main bearing journals and one of the crank webs of the crankshaft by means of the at least one impact tool.

8. The method as claimed in claim 1, wherein only transition radii either between the connecting-rod bearing journals and the crank webs or between the main bearing journals and the crank webs are selected as defined transition radii.

9. The method as claimed in claim 1, wherein at least two impact tools are used and at least one transition radius between one of the connecting-rod bearing journals and one of the adjoining crank webs and at least one transition radius between one of the main bearing journals and one of the adjoining crank webs are selected as defined transition radii.

10. The method as claimed in claim 1, wherein, for the introduction of the impact force into at least one of the transition radii along the respective transition radius running in annularly encircling fashion around the crankshaft, a highly loaded region, a lightly loaded region and interposed intermediate regions are defined, following which impact hardening is performed such that the impact force introduced into the intermediate regions is increased in the direction of the highly loaded region.

11. The method as claimed in claim 1, wherein the only transition radii situated in the at least one portion that has the length deviations are selected as defined transition radii.

12. The method as claimed in claim 1, wherein the nature of the concentricity error is determined based on whether an arcuate runout of the crankshaft is present, wherein the defined transition radii are selected on the basis of the nature of the concentricity error.

13. The method as claimed in claim 1, wherein the nature of the concentricity error is determined based on whether a zigzag runout of the crankshaft is present, wherein the defined transition radii are selected on the basis of the nature of the concentricity error.

14. The method as claimed in claim 1, wherein the defined transition radii are determined on the basis of calculations of a respective crankshaft type.

15. The method as claimed in claim 1, wherein the defined transition radii are determined on the basis of series of tests of a respective crankshaft type.

16. A method for the post-processing of a crankshaft for the purposes of correcting concentricity errors and/or for the purposes of length correction, the method comprising the following steps: determining concentricity errors for sectors of the crankshaft and/or determining a length deviation from a setpoint length for at least one portion of the crankshaft; introducing an impact force for correcting the concentricity errors and/or the length deviation into at least one defined transition radius between connecting-rod bearing journals and crank webs and/or between main bearing journals and the crank webs of the crankshaft by means of at least one impact tool; and hardening the transition radii of the crankshaft prior to the determination of the concentricity errors and/or the determination of the length deviation, wherein the portion of the crankshaft in which the length deviation from the setpoint length is determined corresponds to a partial length of the crankshaft.

17. A method for the post-processing of a crankshaft for the purposes of correcting concentricity errors and/or for the purposes of length correction, the method comprising the following steps: determining concentricity errors for sectors of the crankshaft and/or determining a length deviation from a setpoint length for at least one portion of the crankshaft; introducing an impact force for correcting the concentricity errors and/or the length deviation into at least one defined transition radius between connecting-rod bearing journals and crank webs and/or between main bearing journals and the crank webs of the crankshaft by means of at least one impact tool; and hardening the transition radii of the crankshaft prior to the determination of the concentricity errors and/or the determination of the length deviation, wherein the portion of the crankshaft in which the length deviation from the setpoint length is determined corresponds to an entire length of the crankshaft.

Description

BRIEF DESCRIPTION OF THE FIGURES

(1) Exemplary embodiments of the invention will be described in more detail below on the basis of the drawing.

(2) The figures each show preferred exemplary embodiments, in which individual features of the present invention are illustrated in combination with one another. Features of an exemplary embodiment are also implementable separately from the other features of the same exemplary embodiment, and may accordingly be readily combined by a person skilled in the art with features of other exemplary embodiments in order to form further meaningful combinations and sub-combinations.

(3) In the figures, functionally identical elements are denoted by the same reference designations.

(4) In the figures, in each case schematically:

(5) FIG. 1 shows an overall view of an apparatus according to the invention for carrying out the method in a first embodiment;

(6) FIG. 2 shows a perspective view of a part of the apparatus according to the invention for carrying out the method in a second embodiment;

(7) FIG. 3 shows an impact device with two impact tools in an enlarged illustration as per the detail “A” from FIG. 1;

(8) FIG. 4 shows an impact device with only one impact tool;

(9) FIG. 5 shows an exemplary crankshaft with exemplary length deviations in exemplary portions of the crankshaft;

(10) FIG. 6 shows an exemplary crankshaft with a concentricity error in the manner of an arcuate runout;

(11) FIG. 7 shows an exemplary crankshaft with a concentricity error in the manner of a zigzag runout;

(12) FIG. 8 shows an exemplary crankshaft with a concentricity error in the end sections of the crankshaft;

(13) FIG. 9 shows an exemplary detail of a further crankshaft;

(14) FIG. 10 shows a section through the crankshaft of FIG. 9 in accordance with the section line X;

(15) FIG. 11 shows an exemplary division of an annularly encircling transition radius into a highly loaded region, a lightly loaded region and interposed intermediate regions of an exemplary journal;

(16) FIG. 12 shows an exemplary distribution of impact forces along a transition radius, running in annularly encircling fashion around a journal, in a first embodiment;

(17) FIG. 13 shows an exemplary distribution of impact forces along a transition radius, running in annularly encircling fashion around a journal, in a second embodiment;

(18) FIG. 14 shows an exemplary distribution of impact forces along a transition radius, running in annularly encircling fashion around a journal, in a third embodiment; and

(19) FIG. 15 shows an exemplary distribution of impact forces along a transition radius, running in annularly encircling fashion around a journal, in a fourth embodiment.

DETAILED DESCRIPTION OF THE INVENTION

(20) The apparatus illustrated in an overall view in FIG. 1 basically corresponds in terms of its construction to the apparatuses as per DE 34 38 742 C2 and EP 1 716 260 B1 with one or more impact devices 1, for which reason only the important parts, and the differences in relation to the prior art, will be discussed in more detail below.

(21) The apparatus has a machine bed 2 and a drive device 3. The drive device 3 is used to move or rotate a crankshaft 4 along a direction of rotation into an impact position.

(22) The crankshaft 4 has connecting-rod bearing journals 5 and main bearing journals 6, between which crank webs 7 are arranged in each case. Transition radii 8 (see FIGS. 3 to 9) are formed between connecting-rod bearing journals 5 and crank webs 7 and between main bearing journals 6 and crank webs 7, or generally between transitions in cross section of the crankshaft 4.

(23) At that side of the crankshaft 4 which faces toward the drive device 3, there is provided a fastening device 9 which has a clamping disk or a fastening flange 10. On that side of the crankshaft 4 which is averted from the drive device 3, a support 11 preferably in the manner of a tailstock is provided, which has a further fastening device 9 for the purposes of rotatably receiving or rotatably fixing the crankshaft 4. Optionally or in addition to the support 11, a back rest may be provided which is positioned at a rotationally symmetrical location.

(24) The drive device 3 is capable of setting the crankshaft 4 in rotation motion along an axis of rotation C. Provision may be made here whereby the main axis of rotation C.sub.KW of the crankshaft 4 is positioned eccentrically from the axis of rotation C of the drive device 3, as illustrated in FIG. 1 and FIG. 2. For this purpose, it is preferably possible for alignment means 17 (see FIG. 2) to be provided in the region of the fastening device 9. Here, provision may be made whereby the alignment means 17 displace a central axis of the journal 5, 6 that is respectively to be hardened such that the central axis of the journal 5, 6 lies on the axis of rotation C.

(25) A direct drive, preferably without a clutch, may be provided for the drive device 3. A motor, preferably an electric motor, of the drive device 3 can thus be coupled without a transmission ratio or transmission to the fastening device 9 or to the crankshaft 4.

(26) The impact devices 1 described in more detail by way of example below are each held adjustably in a displacement and adjustment device 15 in order to adapt them to the position of the connecting-rod bearing journals 5 and of the main bearing journals 6 and to the length of the crankshaft 4.

(27) The support 11 may also be designed to be displaceable, as indicated by the double arrows in FIG. 1.

(28) Two impact devices 1 are illustrated in FIG. 1, though basically any number of impact devices 1 may be provided, for example also only a single impact device 1.

(29) Provision may also be made whereby at least one impact device 1 is designed and configured for introducing impact forces into the transition radii 8 of the main bearing journals 6 and one impact device 1 is designed and configured for introducing impact forces into the transition radii 8 of the connecting-rod bearing journals.

(30) According to the invention, a method for the post-processing of a crankshaft 4 is provided, in particular for the correction of concentricity errors and/or for the length correction of the crankshaft 4.

(31) Here, provision is made whereby sectors S.sub.1, S.sub.2, S.sub.3, S.sub.4, S.sub.5, S.sub.6 (see the following FIGS. 6 to 8) of the crankshaft 4 which characterize the concentricity errors are firstly determined.

(32) Alternatively or in addition, but not illustrated here, sectors which cause the concentricity errors may also be determined. The sectors which respectively characterize and cause the concentricity errors may also coincide, for example in the case of the sectors S.sub.3 and S.sub.4.

(33) Alternatively or in addition, at least one length deviation ΔL.sub.1, ΔL.sub.2, ΔL.sub.3 from a setpoint length L.sub.1, L.sub.2, L.sub.3 (see the following FIG. 5) of at least one portion of the crankshaft 4 is determined. According to the invention, subsequently, an impact force F.sub.S for correcting the concentricity errors and/or the length deviation is introduced into at least one defined transition radius 8 between one of the connecting-rod bearing journals 5 and one of the crank webs 7 and/or into at least one transition radius 8 between one of the main bearing journals 6 and one of the crank webs 7 of the crankshaft 4 by means of at least one impact tool 16.

(34) The apparatus illustrated in FIG. 1, which is basically designed for the impact hardening of a crankshaft 4, may be used for the introduction of the impact force F.sub.S. Here, provision is preferably made whereby the transition radii 8 of the crankshaft 4 are hardened, preferably impact-hardened, prior to the determination of the concentricity error and/or of the length deviation ΔL.sub.1, ΔL.sub.2, ΔL.sub.3. Provision may however also be made whereby the post-processing of the crankshaft 4 is performed simultaneously with the impact hardening of the crankshaft 4.

(35) The invention may also, in addition to the correction of concentricity errors and/or the correction of length deviations, be used for the post-processing of a crankshaft 4 for the correction of further dimensional and position tolerances. For example, provision may be made whereby, for at least one further shape and/or position specification, a deviation from a nominal dimension is determined, following which an impact force F.sub.S for correcting the at least one further deviation is introduced into at least one defined transition radius 8 between one of the connecting-rod bearing journals 5 and one of the crank webs 7 and/or into at least one transition radius 8 between one of the main bearing journals 6 and one of the crank webs 7 of the crankshaft 4 by means of the at least one impact tool 16.

(36) FIG. 2 illustrates, in a perspective view, a detail of a further apparatus for carrying out the method according to the invention but without an impact device. Here, the apparatus of FIG. 2 is substantially identical to the apparatus of FIG. 1, for which reason only the important differences will be referred to in detail below.

(37) A drive device 3 is once again provided. Furthermore, a fastening device 9 is provided which has a fastening flange 10 and, fastened thereto, a face plate with clamping jaws for fixing the crankshaft 4. The face plate with the clamping jaws of the fastening device 9 is arranged on the fastening flange 10 adjustably on an alignment means 17, whereby the longitudinal axis C.sub.KW of the crankshaft 4 can be displaced relative to the axis of rotation C of a drive shaft or of an input shaft 13.

(38) The crankshaft 4 of FIG. 2 has a configuration which deviates from the embodiment illustrated in FIG. 1, but basically likewise comprises connecting-rod bearing journals 5, main bearing journals 6 and crank webs 7.

(39) In FIG. 2 (as in FIG. 1), a further fastening device 9 may be provided at that end of the crankshaft 4 which is averted from the drive device 3, though said further fastening device may also be omitted.

(40) The invention may basically be implemented with any impact device 1. An impact device 1 of FIG. 1 is illustrated in more detail by way of example in FIG. 3. It has a main body 18 which may be provided with a prismatic abutment correspondingly to the radius of the crankshaft segment to be machined, and which preferably has guides 19 which guide two impact tools 16 in their support plane and provide them with a corresponding degree of freedom in terms of the support angle about a deflecting unit 20, which is advantageous for the adaptation to the dimensional conditions of the crankshaft 4. In each case one ball as impact head 21 is arranged at the front ends of the two impact tools 16. An intermediate part 22 produces the connection between an impact piston 23 and the deflecting unit 20, which transmits the impact energy to the impact tools 16. The intermediate part 22 may possibly also be omitted.

(41) To increase the effectiveness of the impact, a clamping prism 24 may be fastened, via springs 25, by means of adjustable clamping bolts 26 with clamping nuts 27 to that side of the journal 5, 6 which is averted from the main body 18. Other structural solutions are also possible here.

(42) It should be understood that, where a part of the description refers to “an impact tool” or “an impact device” or where “multiple impact tools/impact devices” are mentioned, this may basically mean any number of impact tools/impact devices, for example two, three, four, five, six, seven, eight, nine, ten or more. The reference to a plurality or singularity is provided merely for the sake of better readability, and is not limiting.

(43) By means of the arrangement of multiple impact devices 1 over the length of the crankshaft 4 to be machined, it is possible, as required, for all centrally and possibly eccentrically running regions of the crankshaft 4 to be machined simultaneously.

(44) The impact piston 23 transmits an impulse to the impact tools 16 via the deflecting unit 20, whereby the impact heads 21 of the impact tools 16 introduce the impact force F.sub.S into the transition radii 8.

(45) The expression “F.sub.S” and similar expressions in the present description are to be understood merely as placeholders/variables for any impact force that appears appropriate to a person skilled in the art. Here, where the description refers to “the impact force F.sub.S”, this may thus refer in each case to different or else identical impact forces.

(46) FIG. 4 shows an impact device 1 which is equipped with only one impact tool 16. In the exemplary embodiment shown, the impact device 1 is preferably inclined relative to the crankshaft 4, specifically such that the impact tool 16, which is arranged coaxially with respect to the longitudinal axis of the impact device 1, impacts perpendicularly against the region of the crankshaft segment to be machined, in the present case of the transition radius 8 to be machined. In this case, although it is possible for in each case only one crankshaft segment to be machined, the structural design and the transmission of force by the impact device 1 are on the other hand better and simpler.

(47) This embodiment has proven particularly advantageous for use on non-symmetrical crankshaft segments of the crankshaft 4. The embodiment is also suitable for introducing impact forces, for the purposes of correcting concentricity errors and length deviations, only in one of two transition radii 8 adjoining the same journal 5, 6.

(48) FIG. 5 illustrates an exemplary crankshaft 4 with respective transition radii 8 between connecting-rod bearing journals 5 and crank webs 7 and between main bearing journals 6 and crank webs 7, and further cross-sectional transitions with transition radii 8. Here, exemplary portions are illustrated in which the length deviations ΔL.sub.1, ΔL.sub.2, ΔL.sub.3 from a corresponding setpoint length L.sub.1, L.sub.2, L.sub.3 are determined. Such a portion of the crankshaft 4 may in this case also cover the entire length of the crankshaft 4, which is illustrated in the exemplary embodiment as the difference of the length deviation ΔL.sub.1 from the setpoint length L.sub.1. The illustrated crankshaft 4 in FIG. 5 is therefore too short by the length deviation ΔL.sub.1. The portions of the crankshaft 4 in which the length deviations ΔL.sub.1, ΔL.sub.2, ΔL.sub.3 are determined may have any desired length, and the length may for example also correspond to the spacing between two crank webs 7. In the exemplary embodiment of FIG. 5, a length deviation ΔL.sub.2 from a setpoint length L.sub.2 of a so-called crankshaft throw, that is to say the sequence crank web 7/connecting-rod bearing journal 5/crank web 7 is illustrated by way of example. The region of the crankshaft 4 in which the length deviation ΔL.sub.1, ΔL.sub.2, ΔL.sub.3 is determined may also cover any desired partial length of the crankshaft 4. Also illustrated in the exemplary embodiment is a length deviation ΔL.sub.3 from a setpoint length L.sub.3 in the central region of the crankshaft 4, which encompasses, by way of example, three crankshaft throws.

(49) By means of the introduction of the impact force F.sub.s in accordance with the invention into defined transition radii 8 of the crankshaft 4, the length deviations ΔL.sub.1, ΔL.sub.2, ΔL.sub.3 can be advantageously corrected. For this purpose, it is for example possible for transition radii 8 which are situated in portions which cause the length deviations ΔL.sub.1, ΔL.sub.2, ΔL.sub.3 to be selected. Provision may however also be made, in particular for the correction of the length deviation ΔL.sub.1 of the entire crankshaft 4, for an impact force F.sub.S to be introduced into all transition radii 8 of the crankshaft 4 by means of the at least one impact tool 16.

(50) As mentioned in the introduction, the invention is also particularly suitable for the correction of concentricity errors. Various types of concentricity errors are known from practice. It may be advantageous here to firstly determine the nature of the concentricity error, in particular whether an arcuate runout (illustrated in FIG. 6), a zigzag runout (illustrated in FIG. 7) or a concentricity error in the end sections of the crankshaft 4 (illustrated in FIG. 8) is present, wherein the defined transition radii 8 are selected on the basis of the nature of the concentricity error. A crankshaft 4 with a concentricity error in the manner of an arcuate runout is depicted by way of example in FIG. 6. An arcuate runout is characterized substantially by a curved profile of the main axis of rotation C.sub.kw of the crankshaft 4.

(51) For the correction of the concentricity, in the exemplary embodiments, the sectors S.sub.1, S.sub.2, S.sub.3, S.sub.4, S.sub.5, S.sub.6 of the crankshaft 4 which characterize the concentricity error are firstly determined. An arcuate runout may be characterized for example by the illustrated sectors S.sub.1, S.sub.2 at the ends of the crankshaft 4 and possibly a further sector (not illustrated) in the center of the crankshaft 4, which relates to the maximum or the extreme value of the curve profile of the main axis of rotation C.sub.KW of the crankshaft 4.

(52) FIG. 7 illustrates a concentricity error in the manner of a zigzag runout. A zigzag runout is characterized by a curved profile of the main axis of rotation C.sub.KW of the crankshaft 4 with at least two extremes. In addition to the characterizing sectors S.sub.1, S.sub.2 at the ends of the crankshaft 4, the sectors S.sub.3, S.sub.4 of the extremes of the curve profile of the main axis of rotation C.sub.KW of the crankshaft 4 can be taken into consideration. A correction of the concentricity error illustrated in FIG. 7 may be realized for example through the introduction of an impact force F.sub.S into a transition radius 8 close to the sectors S.sub.3, S.sub.4 that describe the extremes of the curve profile of the main axis of rotation C.sub.KW of the crankshaft 4.

(53) Finally, FIG. 8 illustrates a concentricity error in the end sections of the crankshaft 4, which can be characterized for example by the sectors S.sub.5, S.sub.6. Between these characterizing sectors S.sub.5, S.sub.6, the profile of the main axis of rotation C.sub.KW of the crankshaft 4 is substantially linear.

(54) For the correction, it is preferably possible for those transition radii 8 which are situated in the sectors S.sub.3, S.sub.4, S.sub.5, S.sub.6 to be selected. The extent of the concentricity error is at its greatest in the sectors S.sub.3, S.sub.4, S.sub.5, S.sub.6, and it may therefore be expedient for the correction to introduce impact forces into transition radii 8 of these sectors or into transition radii 8 that adjoin these sectors S.sub.3, S.sub.4, S.sub.5, S.sub.6. The impact forces provided according to the invention may also advantageously be introduced into transition radii which are situated in sectors (or adjoin these sectors) which cause the concentricity errors.

(55) The defined transition radii 8 may basically also be determined on the basis of simulations, calculations and/or series of tests of a respective crankshaft type.

(56) In particular if only one impact device 1 and/or one impact tool 16 is to be used, it may be advantageous to select only transition radii 8 either between connecting-rod bearing journals 5 and crank webs 7 or between main bearing journals 6 and crank webs 7 as defined transition radii 8. In this case, a conversion or adjustment of the apparatus during the method can be omitted, and the processing speed can thus be maximized.

(57) It is preferable for only transition radii 8 between main-bearing journals 6 and crank webs 7 to be selected as defined transition radii 8.

(58) Provision may also be made for at least two impact tools 16 to be used, and for at least one transition radius 8 between one of the connecting-rod bearing journals 5 and one of the adjoining crank webs 7 and at least one transition radius 8 between one of the main bearing journals 6 and one of the adjoining crank webs 7 to be selected as defined transition radii 8.

(59) Provision may particularly preferably be made whereby the at least one impact tool 16 introduces the impact force F.sub.S for the correction of the concentricity errors and/or of the length deviation into highly loaded regions of the defined transition radii 8.

(60) FIG. 9 illustrates an exemplary detail of a crankshaft 4 with respective transition radii 8 between connecting-rod bearing journals 5 and crank webs 7 and between main bearing journals 6 and crank webs 7.

(61) Depending on the engine operation or purpose of the crankshaft 4, the transition radii 8 respectively adjoining the journals 5, 6 may have highly loaded regions B.sub.MAX that are situated in each case at different positions. An exemplary loading of the crankshaft 4 is illustrated in FIG. 9 by means of an arrow. The connecting-rod bearing journal 5 is connected along the arrow via a piston (not illustrated) to the engine. That side of the connecting-rod bearing journal 5 to which the arrow points is in this case the so-called pressure side. The so-called bottom dead center BDC of the connecting-rod bearing journal 5 is situated at the side opposite the pressure side, specifically the tension side. From experience, the bending loading of the respective transition radii 8 is at its greatest at the bottom dead center BDC of the connecting-rod bearing journal 5. It is advantageously possible for the highly loaded region B.sub.MAX to be defined as adjoining, preferably symmetrically surrounding, the bottom dead center BDC.

(62) In the case of the crankshaft 4 illustrated in FIG. 9, it is furthermore possible for a most highly loaded point of the main bearing journal 6 adjoining the connecting-rod bearing journal 5 to be a region which corresponds to the pressure side of the adjoining connecting-rod bearing journal 5. For simplicity, said region of a main bearing journal 6 will hereinafter be referred to as “top dead center” TDC.

(63) Provision may thus in particular be made whereby, for the introduction of the impact force F.sub.S for the correction of the concentricity errors and/or length deviation into at least one of the transition radii 8 along the respective transition radius 8 running in annularly encircling fashion (around the connecting-rod bearing journal 5 and/or main bearing journal 6), a highly loaded region B.sub.MAX, a lightly loaded region B.sub.MIN and interposed intermediate regions B.sub.ZW are defined, following which impact hardening is performed such that the impact force F.sub.S introduced into the intermediate regions B.sub.ZW is increased in the direction of the highly loaded region B.sub.MAX.

(64) Here, provision may be made whereby the impact force F.sub.S that is introduced into the highly loaded region B.sub.MAX is determined on the basis of the desired fatigue strength of the crankshaft 4 and/or the desired fatigue strength of portions of the crankshaft 4.

(65) For improved illustration of the positions of the dead centers BDC and TDC, FIG. 10 shows a diagrammatic section through the crankshaft 4 along the illustrated section line “X” in FIG. 9.

(66) It can be seen here that the most highly loaded point or the top dead center TDC of a transition radius 8 of a main bearing journal 6 lies, in the cross section of the crankshaft 4, at the point of intersection of the transition radius 8 of the main bearing journal 6 with the connecting line x of the central points M.sub.H, M.sub.P of the main bearing journal 6 and of the connecting-rod bearing journal 5 adjoining the transition radius 8 of the main bearing journal 6.

(67) FIG. 11 shows a section through an exemplary journal 5, 6 for the purposes of illustrating the possible distribution of the regions B.sub.MAX, B.sub.MIN, B.sub.ZW along the circumference of the journal 5, 6.

(68) In the present case, the most highly loaded point of the journal 5, 6, that is to say the bottom dead center BDC of a connecting-rod bearing journal 5 or the top dead center TDC of a main bearing journal 6, is denoted by 180°. Proceeding from this point, the highly loaded region B.sub.MAX is defined along the transition radius 8 running in annularly encircling fashion around the crankshaft 4. The highly loaded region B.sub.MAX may amount to at least ±20°, preferably at least ±30°, more preferably at least ±40°, particularly preferably at least ±50°, very particularly preferably at least ±60°, for example at least ±70°, at least ±80° or at least ±90° proceeding from this point, preferably symmetrically.

(69) Adjoining the highly loaded region B.sub.MAX, there are defined two intermediate regions B.sub.ZW which separate the highly loaded region B.sub.MAX from the lightly loaded region B.sub.MIN. The intermediate regions B.sub.ZW may encompass any angle segment along the annularly encircling transition radius 8. The same applies to the lightly loaded region B.sub.MIN. The respective angle ranges may be determined by calculations, simulation and/or test series, possibly also from measurements during real-time operation (of the engine).

(70) The impact force F.sub.S introduced into the intermediate regions B.sub.ZW is preferably increased (preferably steadily) in the direction of the highly loaded region B.sub.MAX. The statement that the impact force F.sub.S is increased means that the impact force F.sub.S is preferably progressively increased between successive impacts.

(71) FIGS. 12 to 15 illustrate four exemplary profiles of the impact force F.sub.S along the circumference of a journal 5, 6, for example of the journal 5, 6 from FIG. 11.

(72) Here, in FIGS. 12, 14 and 15, the impact force F.sub.S that is introduced into the respective highly loaded region B.sub.MAX is constant.

(73) In all of the curves illustrated by way of example, the impact force F.sub.S introduced into the highly loaded regions B.sub.MAX is greater than or at least equal to the respective maximum impact force F.sub.S that is introduced into the intermediate regions B.sub.ZW (and self-evidently in each case greater than the impact force F.sub.S that is introduced into the lightly loaded region B.sub.MIN).

(74) The maximum impact force F.sub.MAX is thus introduced in the highly loaded region B.sub.MAX of the transition radius 8.

(75) Furthermore, FIGS. 12 and 15 show an exemplary force distribution in which, in each case, no impact force F.sub.S is introduced into the lightly loaded region B.sub.MIN. By contrast, in FIGS. 13 and 14, in the in each case lightly loaded region B.sub.MIN, an impact force F.sub.S is introduced which is lower than the lowest impact force F.sub.S that is introduced into the intermediate regions B.sub.ZW. Here, in the case of FIG. 14, a minimum impact force F.sub.min is provided, which is kept constant in the lightly loaded region B.sub.MIN. By contrast, in FIG. 13, proceeding from the intermediate regions B.sub.ZW to the position situated opposite the most highly loaded point or the bottom dead center BDC or the top dead center TDC respectively, the impact force F.sub.S is reduced in steadily linear fashion to a minimum value, in the present case 0.

(76) In FIG. 12, proceeding from the lightly loaded region B.sub.MIN, in which for example no impact force is introduced in the present case, the impact force F.sub.S introduced into the intermediate regions B.sub.ZW is increased uniformly and/or linearly to the highly loaded region B.sub.MAX. By contrast, in FIG. 13, the profile of the impact force F.sub.S follows a continuous ramp which, proceeding from a point situated opposite the most highly loaded point or the bottom dead center BDC or the top dead center TDC along the circumference of the crankshaft 4, increases in each case in the direction of the most highly loaded point or the bottom dead center BDC or the top dead center TDC respectively. Here, in the respective regions B.sub.MIN, B.sub.ZW and B.sub.MAX, the profile of the impact force F.sub.S follows a respectively associated ramp function, which collectively form the ramp illustrated.

(77) FIG. 14 illustrates a profile of the impact force F.sub.S which is basically similar to the profile of the impact force F.sub.S of FIG. 12. In the intermediate regions B.sub.ZW, however, by contrast to the linear or ramp-shaped variation of the impact force F.sub.S illustrated in FIG. 12, a smoothed curve profile is illustrated.

(78) Basically, FIG. 15 shows a diagram in which the impact forces F.sub.S are varied in the intermediate regions B.sub.ZW in steps.

(79) Finally, any variations and combinations, in particular (but not exclusively) of the profiles illustrated in FIGS. 12 to 15, may be provided. The invention is not restricted to a particular profile of the impact force F.sub.S. A profile of the impact force F.sub.S along the circumference of the annularly encircling transition radius 8 may also be selected with regard to the engine operation or the purpose of the crankshaft 4.