Method and device for the impact treatment of transition radii of a crankshaft

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/or transition radii (8) between main bearing journals (6) and the crank webs (7) of the crankshaft (4). In order to apply an impact force (FS) to at least one of the transition radii (8) along the respective transition radius (8) circulating about the crankshaft (4) in an annular manner, a heavily loaded region (BMAX), a lightly loaded region (BMIN), and intermediate regions (BZW) lying therebetween are defined, and an impact treatment is then carried out such that the impact force (FS) introduced into the intermediate regions (BZW) is increased in the direction of the heavily loaded region (BMAX).

Claims

1. A method for the impact hardening of transition radii of a crankshaft, in a particular of transition radii between connecting-rod bearing journals and crank webs and/or transition radii between main bearing journals and the crank webs of the crankshaft for the introduction of an impact force into at least one of the transition radii, wherein a highly loaded region, a lightly loaded region and interposed intermediate regions are defined along the respective transition radius running in annularly encircling fashion around the crankshaft, wherein impact hardening is performed such that the impact force introduced into the intermediate regions is increased in the direction of the highly loaded region, wherein the impact head of the at least one impact tool introduces the impact force into the transition radius at an adjustable impact angle.

2. The method as claimed in claim 1, wherein the impact force introduced into the intermediate regions is increased steadily in the direction of the highly loaded region.

3. The method as claimed in claim 1, wherein the impact force introduced into the intermediate regions is increased in the direction of the highly loaded region.

4. The method as claimed in claim 1, wherein during the impact hardening, no impact force is introduced into the lightly loaded region.

5. The method as claimed in claim 1, wherein during the impact hardening, an impact force higher than or equal to the highest impact force introduced into the intermediate regions is introduced into the highly loaded region.

6. The method as claimed in claim 1, wherein the impact force that is introduced into the highly loaded region during the impact hardening is determined on the basis of the desired fatigue strength of the crankshaft.

7. The method as claimed in claim 1, wherein the impact force that is introduced into the highly loaded region during the impact hardening is constant.

8. The method as claimed in claim 1, wherein along the transition radius running in annularly encircling fashion around the connecting-rod bearing journal, the highly loaded region amounts to at least +/−20° proceeding from a most highly loaded point of the connecting-rod bearing journal.

9. The method as claimed in claim 1, wherein along the transition radius running in annularly encircling fashion around the main bearing journal, the highly loaded region amounts to at least +/−20° proceeding from a most highly loaded point of the main bearing journal.

10. The method as claimed in claim 9, wherein the most highly loaded point of a transition radius of a main bearing journal lies, in the cross section of the crankshaft, at the point of intersection of the transition radius of the main bearing journal with the connecting line of the central points of the main bearing journal and of the connecting-rod bearing journal adjoining the transition radius of the main bearing journal.

11. The method as claimed in claim 1, wherein the impact hardening is performed in such a way that the impressions of an impact head of at least one impact tool overlap in a defined manner along the respective transition radius running in annularly encircling fashion around the crankshaft.

12. The method as claimed in claim 1, wherein, for the impact hardening, an impact device is used which has an impact piston, a deflecting unit and the at least one impact tool, wherein the at least one impact tool is fastened to the deflecting unit, and wherein the impact piston transmits an impulse to the at least one impact tool by means of the deflecting unit, following which the impact head of the at least one impact tool introduces the impact force into the transition radius at the impact angle, and wherein the impact angle is set through adjustment of the spacing between a deflecting point of the deflecting unit and the front end of the impact head of the at least one impact tool.

13. The method as claimed in claim 1, wherein, for the impact hardening, the crankshaft is firstly rotated by means of a drive device along a direction of rotation into an impact position, wherein an arresting device is provided in order to arrest the crankshaft in the impact position, following which the impact force is introduced into at least one transition radius by means of at least one impact tool.

14. The method as claimed in claim 1, wherein the impact force introduced into the intermediate regions is increased uniformly in the direction of the highly loaded region.

15. The method as claimed in claim 1, wherein the impact force introduced into the intermediate regions is increased linearly in the direction of the highly loaded region.

16. The method as claimed in claim 1, wherein during the impact hardening, an impact force lower than or equal to the lowest impact force introduced into the intermediate regions is introduced into the lightly loaded region.

17. The method as claimed in claim 1, wherein the impact force that is introduced into the highly loaded region during the impact hardening is determined on the basis of the desired fatigue strength of portions 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 detail of a crankshaft;

(10) FIG. 6 shows a section through the crankshaft of FIG. 5 in accordance with the section line VI;

(11) FIG. 7 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;

(12) FIG. 8 shows an exemplary distribution of impact forces along a transition radius, running in annularly encircling fashion around a journal, in a first embodiment;

(13) FIG. 9 shows an exemplary distribution of impact forces along a transition radius, running in annularly encircling fashion around a journal, in a second embodiment;

(14) FIG. 10 shows an exemplary distribution of impact forces along a transition radius, running in annularly encircling fashion around a journal, in a third embodiment;

(15) FIG. 11 shows an exemplary distribution of impact forces along a transition radius, running in annularly encircling fashion around a journal, in a fourth embodiment;

(16) FIG. 12 shows an impact device with two telescopic impact tools;

(17) FIG. 13 is an enlarged illustration of a transition radius and of an impact tool with an impact head, wherein the impact tool is aligned at a first impact angle;

(18) FIG. 14 is an enlarged illustration of a transition radius and of an impact tool with an impact head, wherein the impact tool is aligned at a second impact angle;

(19) FIG. 15 shows an impact-hardened transition radius in the case of which impact impressions of an impact head overlap along the annularly encircling transition radius;

(20) FIG. 16 shows an impact-hardened transition radius in the case of which a first impact angle has been used for the impact hardening;

(21) FIG. 17 shows an impact-hardened transition radius in the case of which a second impact angle has been used for the impact hardening;

(22) FIG. 18 shows an impact-hardened transition radius in the case of which the impact angle has been varied during the impact hardening along the annularly encircling transition radius; and

(23) FIG. 19 shows a flow diagram during the use of an arresting device.

DETAILED DESCRIPTION OF THE INVENTION

(24) 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.

(25) 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.

(26) 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 5 and 13 to 18) 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.

(27) 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.

(28) Furthermore, an arresting device 12 may be provided, which engages in the region of an outer circumference of the fastening device 9. This is illustrated by dashed lines in FIG. 1. Basically, the arresting device 12 may be arranged at any desired location within the apparatus in order to apply an arresting force to an output shaft of the drive device 3, or to an input shaft 13, which in the present case is identical to said output shaft, of the fastening device 9, and thus to the crankshaft 4. The arresting device 12 may also engage on multiple locations of the apparatus. By way of example, a second part of the arresting device 12 in engagement with the fastening device 9 in the region of the support 11 is likewise illustrated by dashed lines.

(29) The arresting device 12 is based for example on a non-positive arresting action using a merely schematically illustrated brake shoe arrangement 14.

(30) 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.

(31) 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.

(32) 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.

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

(34) 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.

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

(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) An impact device 1 of FIG. 1 is illustrated in more detail by way of example in FIG. 3. The invention may basically be implemented with any impact device 1. The impact device 1 described below is however particularly suitable. 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 or impact angle α (see FIGS. 12 to 14) 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 head/impact tool” or “an impact device” or “multiple impact heads/impact tools/impact devices”, this may basically mean any number of impact heads/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 an impact force F.sub.S into the transition radii 8 at an impact angle α. Provision may be made here whereby the spacing d (cf. FIG. 12) between the deflection point U.sub.P of the deflecting unit 20 and the front end of the respective impact head 21 of the impact tools 16 is adjustable.

(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. Bore ends can additionally be hardened by means of this tool in a standing position.

(47) This embodiment has proven particularly advantageous for use on non-symmetrical crankshaft segments, such as the end regions and the oil bore ends of the crankshaft 4.

(48) FIG. 5 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.

(49) According to the invention, provision is made whereby, for the introduction of the impact force F.sub.S into at least one of the transition radii 8, a highly loaded region B.sub.MAX, a lightly loaded region B.sub.MIN and interposed intermediate regions B.sub.ZW are defined along the respective transition radius 8 running in annularly encircling fashion (around the connecting-rod bearing journal 5 and/or main bearing journal 6), wherein 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.

(50) Provision may be made here whereby the impact force F.sub.S that is introduced into the highly loaded region B.sub.MAX during the impact hardening 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.

(51) 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. 5 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.

(52) In the case of the crankshaft 4 illustrated in FIG. 5, 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.

(53) For improved illustration of the positions of the dead centers BDC and TDC, FIG. 6 shows a diagrammatic section through the crankshaft 4 along the illustrated section line “VI” in FIG. 5.

(54) 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.

(55) FIG. 7 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.

(56) 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.

(57) 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).

(58) 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.

(59) FIGS. 8 to 11 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. 7.

(60) Here, in FIGS. 8, 10 and 11, the impact force F.sub.S that is introduced into the respective highly loaded region B.sub.MAX during the impact hardening is constant.

(61) 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 during the impact hardening 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).

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

(63) Furthermore, FIGS. 8 and 11 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 during the impact hardening. By contrast, in FIGS. 9 and 10, in the in each case lightly loaded region B.sub.MIN, an impact force F.sub.S is introduced during the impact hardening 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. 10, 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. 9, 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.

(64) In FIG. 8, proceeding from the lightly loaded region B.sub.MIN, in which for example no impact hardening is performed 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.

(65) By contrast, in FIG. 9, 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.

(66) FIG. 10 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. 8. 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. 8, a smoothed curve profile is illustrated.

(67) Finally, FIG. 11 shows a diagram in which the impact forces F.sub.S are varied in the intermediate regions B.sub.ZW in steps.

(68) Finally, any variations and combinations, in particular (but not exclusively) of the profiles illustrated in FIGS. 8 to 11, 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.

(69) Provision may be made whereby the impact head 21 of the at least one impact tool 16 introduces the impact force F.sub.S into the transition radius 8 at an impact angle α, wherein the impact force F.sub.S is adjustable. The impact angle α□may in particular be varied by virtue of the spacing d between the deflection point U.sub.P of the deflecting unit 20 and the front end of the respective impact head 21 of the impact tools 16 being adjustable.

(70) The technical solution for the adjustment of the spacing d is illustrated in schematic form by dashed lines in FIG. 3. For example, a changeover device 30 with a magazine may be provided in order to exchange the at least one impact tool 16 and/or the impact head 21 and/or the deflecting unit 20 and/or the at least one impact device 1 in order to adjust the spacing d between the deflection point U.sub.P of the deflecting unit 20 and the front end of the impact head 21 of the at least one impact tool 16 to a different value. A changeover device 30 for the exchange of impact tools 16 is indicated in FIG. 3. For this purpose, the changeover device 30 comprises a selection of impact tools 16 of in each case different length. By exchanging an impact tool 16, the spacing d and thus the impact angle α can be adjusted.

(71) Provision may also be made whereby the length of the impact tools 16 is adjustable, preferably telescopically. A corresponding construction is illustrated in FIG. 12. Here, FIG. 12 shows a detail of an impact device 1, which may be of substantially identical design to the embodiment of FIG. 3.

(72) In FIG. 12, two telescopic impact tools 16 are schematically illustrated. By means of the adjustable length of the impact tools 16, the spacing d between the deflection point U.sub.P of the deflecting unit 20 and the front end of an impact head 21 is adjustable. In this way, it is thus indirectly also possible for the impact angle α and possibly also the impact position to be influenced.

(73) Provision may also be made, as illustrated in FIG. 1, for multiple impact devices 1 to be used. The respective spacing d between the deflection point U.sub.P and impact heads 21 is then preferably not identical at least in the case of two impact devices 1. This makes it possible for the impact devices 1 to be used in each case for the impact hardening of a transition radius 8 or of a group of transition radii 8, wherein the impact tools 16 of the respective impact device 1 are in each case already adjusted to the preferentially provided impact angle α. Conversion of the impact device 1 is thus not necessary. If the crankshaft 4 has only transition radii 8 with two different advantageous impact angles α, it is thus preferably the case that two correspondingly preset impact devices 1 are sufficient.

(74) Provision may for example be made whereby a first impact device 1 introduces impact forces F.sub.S at a first impact angle α.sub.1 and a second impact device 1 introduces impact forces F.sub.S at a second impact angle α.sub.2. Use may also be made of impact devices 1 in the case of which the spacing d and/or the impact angle α is adjustable in a different way. It is also possible for a conventional impact device to be combined with an impact device 1 with adjustable spacing d.

(75) Provision may be made whereby the impact angle α between the longitudinal axis L.sub.S of the at least one impact tool 16 and a line l.sub.KW perpendicular to the longitudinal axis C.sub.KW of the crankshaft 4 amounts to 5° to 80°, preferably 10° to 70°, more preferably 20° to 60° and particularly preferably 30° to 55°, in particular 35° to 50°.

(76) To illustrate the relationships, FIGS. 13 and 14 illustrate enlarged views which highly schematically illustrate an impact head 21 of an impact tool 16 and an exemplary transition radius 8 of a crankshaft 4. Here, in the example of FIG. 13, impact hardening is performed at a first impact angle α.sub.1, and in FIG. 14, impact hardening is performed at a second impact angle α.sub.2.

(77) Through the corresponding adjustment of the impact angle α by means of the variation of the spacing d between the deflection point U.sub.P of the deflecting unit 20 and the impact head 21 of the impact tool 16, the direction of the impact force F.sub.S can be predefined, whereby the range of greatest effectiveness of the impact hardening can be set in targeted fashion.

(78) Provision may also be made for the impact force F.sub.S to be reduced in targeted fashion or for the direction of action to be varied, for example if reduced cross sections, bores or other geometrical conditions necessitate this.

(79) Preferably, the impact angle α is selected in accordance with the profile of a loading maximum MAX.sub.1, MAX.sub.2 of the transition radius 8, wherein the profile of the loading maximum MAX.sub.1, MAX.sub.2 is determined on the basis of simulations and/or calculations and/or series of tests of the respective crankshaft type.

(80) In FIG. 14, the impact head 21 is positioned at the same position of the transition radius 8 as in FIG. 13. However, the spacing d between the deflection point U.sub.P of the deflecting unit 20 and the impact head 21 is set such that the impact tool 16 is aligned at a different impact angle α than in FIG. 13. It follows from this that the impact is introduced into the transition radius 8 at the angle α.sub.2, even though the impact head 21 is basically applied at the same position as in FIG. 13.

(81) The illustration in FIG. 14 differs to a particularly great extent from the illustration in FIG. 13 for illustrative purposes.

(82) It is basically also possible for the positioning of the impact head 21 in the transition radius 8 to be varied, that is to say the impact head 21 could possibly also be applied at a different position along the circumference of the transition radius 8, wherein, at the same time, the impact angle α may be variable.

(83) The impact head 21 may have a radius r.sub.S of which the magnitude amounts to 75% to 99% of the transition radius 8, preferably 85% to 98% of the transition radius 8 and particularly preferably 85% to 95% of the transition radius 8. The radius r.sub.S of the impact head 21 preferably substantially corresponds to the transition radius 8.

(84) FIG. 15 (and the subsequent FIGS. 16 to 18) illustrate an exemplary transition radius 8 between a main bearing journal 6 and a crank web 7, in the case of which the impact hardening has been performed such that the impact impressions 28 of an impact head 21 of the impact tool 16 overlap along the transition radius 8 running in annularly encircling fashion around a main bearing journal 6.

(85) To achieve this type of impact hardening, highly precise working or operation of the apparatus is necessary.

(86) In particular if the impact spacings are set to be narrow, it is the case during a subsequent impact that the impact head 21 penetrates at least partially into the impact impression 28 of the preceding impact, whereby the impact force can exert a resetting rotational action on the crankshaft 4. The arresting device 12 that has already been illustrated may be provided and designed to prevent such a rotational movement. It may in particular be advantageous for the arresting device 12 to be designed to prevent rotation of the crankshaft 4 counter to the direction of rotation of the drive device 3.

(87) In a particular variant of the invention, provision may thus be made whereby, for the impact hardening, the crankshaft 4 is firstly rotated by the drive device 3 along a direction of rotation into an impact position, wherein the arresting device 12 is provided in order to arrest the crankshaft 4 in the impact position, following which an impact force F.sub.S is introduced into at least one transition radius 8 by means of at least one impact tool 16.

(88) FIGS. 16 and 17 illustrate further exemplary transition radii 8 between a main bearing journal 6 and a crank web 7, in the case of which the impact impressions 28 of an impact head 21 of the impact tool 16 overlap along the transition radius 8 running in annularly encircling fashion around the main bearing journal 6. As already mentioned above, during a subsequent impact, the impact head 21 may at least partially penetrate into the impact impression 28 of a preceding impact, giving rise to the “track” of impact impressions 28 illustrated in the figures. By contrast to the illustration in FIG. 15, the track of the impact impressions 28 is illustrated in simplified form in FIGS. 16 to 18.

(89) In FIGS. 16 and 17, the impact hardening has been performed at different impact angles α. Here, for the purposes of the illustration in the figure, the impact impressions 28 run with a clearly visible offset with respect to one another on the circumference of the transition radius 8.

(90) The deviation is in fact preferably only small, but nevertheless effective. The offset profile may be achieved by means of a changed impact angle α, as illustrated in FIG. 14, and/or by means of a changed point of application of the impact head 21. In the case of the transition radius 8 of FIG. 16, a smaller impact angle α was selected than in the case of the transition radius 8 of FIG. 17, that is to say the spacing d between the deflection point U.sub.P of the deflecting unit 20 and the impact head 21 of the impact tool 16 was set to be greater in the case of the method as per FIG. 16 than in the case of the transition radius 8 of FIG. 17. Accordingly, the impact impressions 28 run higher up, or closer to the crank web 7, in the case of the transition radius 8 illustrated in FIG. 17 than in the case of the transition radius 8 of FIG. 16.

(91) Provision may also be made whereby, during the impact hardening of a transition radius 8, the impact angle α of an impact tool 16 is varied along the respective transition radius 8 running in annularly encircling fashion around the connecting-rod bearing journal 5 and/or main bearing journal 6. This is illustrated in FIG. 18.

(92) Provision may be made whereby all transition radii 8 between connecting-rod bearing journals 5 and the crank webs 7 are impact-hardened with a first impact angle α and all transition radii 8 between the main bearing journals 6 and the crank webs 7 are impact-hardened at a second impact angle α.

(93) Alternatively, provision may be made whereby at least two transition radii 8 between the connecting-rod bearing journals 5 and the crank webs 7 are impact-hardened at a different impact angle α, and/or whereby at least two transition radii 8 between the main bearing journals 6 and the crank webs 7 are impact-hardened at a different impact angle α, and/or whereby at least one transition radius 8 between the connecting-rod bearing journal 5 and the crank webs 7 is impact-hardened at a different impact angle α, than a transition radius 8 between the main bearing journals 6 and the crank webs 7.

(94) FIG. 19 illustrates a method which relates to the particular variant of the invention with the arresting device 12 and which is basically composed of four steps (rotating, arresting, impacting, releasing).

(95) For the operation of the drive device 3, which preferably comprises an electric motor, closed-loop position control may be used in order to rotate the crankshaft 4 into the respective impact position, wherein the crankshaft 4 is rotated preferably in stepped or clocked fashion.

(96) After the crankshaft 4 has been rotated by the drive device 3 into the impact position, the crankshaft 4 is initially arrested in the impact position by the arresting device 12.

(97) Subsequently, an impact force F.sub.S is introduced into at least one transition radius 8 of the crankshaft 4 by means of at least one impact tool 16.

(98) Preferably, the controller of the drive device 3 and the controller of the arresting device 12 are synchronized with one another such that the arresting device 12 arrests the crankshaft 4 only when the crankshaft 4 is at a standstill in the impact position.

(99) Furthermore, it is also possible for the controllers of the arresting device 12 and of the at least one impact tool 16 (or of the at least one impact device 1) to be synchronized such that the at least one impact tool 16 introduces the impact force into the transition radius 8 of the crankshaft 4 only when the crankshaft 4 has been arrested in the impact position. The arresting of the crankshaft 4 is subsequently released again.

(100) The method may subsequently be repeated as often as desired along a transition radius 8, preferably for one complete rotation along the circumference of the transition radius 8 or along the annularly encircling transition radius 8. According to the invention, provision may also be made whereby no impact force F.sub.S is introduced in the lightly loaded region B.sub.MIN. There is no need for a complete rotation to be performed. It is also possible for more than one rotation to be provided, for example 2 or 3 rotations.

(101) After a transition radius 8 has been impact-hardened in the desired manner, the impact tool 16, or the entire impact device 1, can be moved to the next transition radius 8 that is to be hardened, following which the method (rotating, arresting, impacting, releasing) can be repeated along the next transition radius 8 running in annularly encircling fashion around the journal 5, 6.

(102) The at least one impact tool 16 or the at least one impact device 1 may introduce the impact movement or the impact force F.sub.S with a periodicity, for example with a timing of 0.1 Hz to 50 Hz, preferably with a timing of 0.3 Hz to 10 Hz, particularly preferably with a timing of 0.5 Hz to 5 Hz and very particularly preferably with a timing of 0.5 Hz to 3 Hz.

(103) An open-loop and/or closed-loop control device 29, preferably comprising a microprocessor, may be provided for carrying out the method. The open-loop and/or closed-loop control device 29 may for example also comprise or implement and/or synchronize the controllers of the drive device 3, of the arresting device 12 and/or of the at least one impact tool 16.

(104) In particular, a computer program with program code means may be provided in order to carry out the method according to the invention when the program is executed on an open-loop and/or closed-loop control device 29, in particular on a microprocessor.