Tripod star for a tripod joint

Abstract

A tripod star (10) for a tripod joint comprises an annular body (11) with an axis of rotation (A), and pins (14) which project radially from the annular body (11) and each have a running surface (15) for supporting a respective tripod roller. The running surfaces (15) of the pins (14) each have, partially, namely in a partial region (18) of the respective running surface (15), a surface structuring (17) consisting of a plurality of raised contact regions (17a) and recessed lubricant regions (17b) located between the plurality of raised contact regions (17a). The height between the raised contact regions (17a) and the recessed lubricant regions (17b) is many times greater than the surface roughness of the running surface (15) in the remaining region without said surface structuring (17).Furthermore, a tripod star is proposed, the ring body (11) of which is hardened in the region of the transition to the pins (14) only locally on partial sections (19) pointing in the circumferential direction around the axis of rotation (A) of the ring body (11) asymmetrically to the plane of symmetry of the pin axes (Z).

Description

The invention relates to a tripod ester for a tripod joint, comprising an annular body having an axis of rotation, and pins which project radially from the annular body and each have a running surface for mounting a tripod roller in each case.Tripod esters are conventionally initially produced from a steel insert by forming, wherein the pins are generally fully formed up to a machining allowance. Subsequently, an internal toothing is produced in a cutting manner on the annular body, sometimes also referred to as hub. The entire component is then case-hardened. Because of the hardness distortions occurring during case hardening, hard machining must generally be carried out subsequently at locations with high accuracy requirements, such as, for example, at the running surfaces of the journals and at the internal toothing.Furthermore, it is common to produce tripod esters from heat-treated steel and inductively cure them. These tripod esters, too, must be hard-machined at least in the region of the pins.In practice, however, the aforementioned production from insert steel predominates.The curing of the whole tripod ester in the initial charge results in high costs. On the one hand, the energy input per tripod ester is high, since the entire mass of tripod ester has to be brought to curing temperature. In addition, case hardening requires a high handling outlay, since this cannot be integrated into flow production. Severe distortions and the carburizing of the tooth root region of the internal toothing lead to a weakening of the internal toothing. Moreover, distortions impair the assembly capability and the load-bearing behavior. However, the complete hardening of the component is advantageous with regard to the load potential and the service life.Induction hardening, in contrast to case hardening, allows shorter process times, since this can be integrated into a flow production. Moreover, fewer edge oxidations occur in this case. The energy input can also be lower than in case of case curing. The problem of hardness distortions remains, however, and must be compensated for by corresponding post-processing.Nevertheless, both methods of production are common in practice, since these are proven and robust methods.A tripod ester of the type mentioned at the beginning is known from DE 10 2009 037 383 A1. To avoid the problems explained above, it is proposed there, contrary to conventional production methods, to cure the tripod ester only partially in the region of the running surfaces by a local heat input limited to this region. By only locally introducing heat into the tripod esters, namely in the region of the running surfaces, the energy requirement in the production is significantly reduced. Induction hardening and laser hardening are mentioned as particularly suitable methods. This would integrate completely into continuous flow production and would require no additional handling complexity with regard to curing. Since the annular body is not hardened in the region of its internal toothing, any hardness distortion is eliminated there, as a result of which the hard finishing effort can be limited to the running surfaces of the journals.All the above-described manufacturing methods have in common that the studs in the region of the running surfaces are generally subjected to a final hard machining in order to correct any hardness distortions, whereby at the same time a high surface quality is achieved.However, practical tests have shown that, with regard to efficiency and service life, not only dimensional deviations due to hardness distortions but also inadequate lubricant supply in the region of the running surfaces can be problematic.A tripod ester having the features of the preamble of claim 1 is known from US 7 357 723 B2. To improve the lubricant supply, it is proposed there to provide the laser-bearing region of the journal with a pattern of flat surfaces or dimples in the direction of rotation of the tripod ester.Furthermore, U.S. Pat. No. 5,791,995 A discloses flattening a spherical running surface of a journal in a circumferential manner, providing the flattened region with an uneven surface by shot peening or providing a helical groove or linear grooves parallel to the journal axis there. The aforementioned surface structures can also be provided in this region without a previous flattening.The object of the invention is to further improve the production of a tripod ester with respect to the avoidance of hardness distortions taking into account the lubricant supply.For this purpose, a tripod joint having the features of patent claim 1 is proposed. This is characterized in particular in that the running surfaces of the journals each have a surface structuring of a multiplicity of raised contact regions and recessed lubricant regions lying between the multiplicity of raised contact regions partially, namely in a partial region of the respective running surface, wherein the height between the raised contact regions and the recessed lubricant regions is many times greater than the surface roughness of the running surface in the remaining region without said surface structuring.In comparison with DE 10 2009 037 383 A1, in the present case, a main load region can be divided at the journals, for example, into a multiplicity of smaller partial contact surfaces. As a result, lubricant can circulate better, namely in the recessed lubricant regions around the raised contact regions, as a result of which, in addition, heat can be dissipated more quickly. The improved circulation of lubricant makes it possible to avoid inadequate lubrication, which ultimately has an advantageous effect on efficiency and service life.The raised contact areas are raised by local martensite formation with respect to the recessed lubricant areas. Such raised contact regions can be obtained by suitably locally restricted curing, in particular by induction curing, laser beam curing or electron beam curing. The martensite formation results in an increase in volume. This effect is used in the present case to lift the raised contact regions out of relation to the lubricant regions. In addition, this achieves an increase in strength in the main load range of the running surface. Since the hardening in this case is limited to very small ranges, hardening distortions relevant to the function of the tripod ester can be excluded, so that hard reworking is not required in this case. The process can be integrated into a flow production.Particular embodiments of the invention are the subject of further claims.The surface structuring is preferably limited to an arc segment region of the running surface which points in the circumferential direction about the axis of rotation of the annular body and is limited to an angular range of 30 to 120° with respect to a longitudinal axis Z of the respective journal. By limiting to the most heavily stressed regions of the tripod ester, the additional production effort for improving service life and efficiency remains minimal.In particular, on a pin, two partial regions with said surface structuring can be opposite each other in the direction of rotation about the axis of rotation of the annular body. This is advantageous above all in the case of recuperation vehicles, since this covers the two main loading directions on the tripod ester.According to a particular embodiment of the invention, the length of said surface structuring in the direction of the longitudinal axis of the pin is limited to 20 to 60% of the total length of the pin in the direction of the longitudinal axis of the pin. Here too, the consideration is based on limiting the production outlay to the most heavily stressed regions in order to achieve component optimization which is particularly appropriate for loading.Furthermore, the development of the region with said surface structuring can be made diamond-shaped in order to make an even better adaptation to the most heavily stressed regions.The tripod roller can comprise an inner ring, an outer ring and rolling elements arranged between them and be mounted with the inner ring on the running surface. In such a construction, the running surface is usually curved spherically, so that the greatest load usually occurs in the region of the greatest diameter of the running surface. Here, a diamond-shaped contour of the partial region with said surface structuring is particularly advantageous.According to another particular embodiment of the invention, the length of said surface structuring in the direction of the longitudinal axis Z of the pin is limited to 50 to 90% of the total length of the pin in the direction of the longitudinal axis Z of the pin. In this case, the development of the region with said surface structuring is preferably triangular. Such a configuration is suitable in particular for so-called single tripods, in which a tripod roller comprises an outer ring and rolling bodies and the outer ring is mounted on the running surface of the journal via the rolling bodies. Usually, the pin can be cylindrical, while the rolling bodies are needles.According to a further particular embodiment of the invention, the subregion overlaps the pitch circle radius PCR of the pins, wherein the minimum length h of the subregion in the direction of the longitudinal axis Z of the pins is equal to or greater than PCR / 9.8.According to a further particular embodiment of the invention, the raised contact regions are linear and / or punctiform. As already mentioned above, a plurality of such linear and / or punctiform contact regions are present in the partial region with said surface structuring. These linear and / or punctiform contact regions can be arranged in different patterns.Lines are understood to mean structures whose length is a multiple of their width. The term punctiform is understood here to mean not only circular geometries but also polygons of any shape. In particular, geometries can be considered to be punctiform in which the ratio of the greatest to the smallest width lies in the range from 0.5 to 2.0.Linear raised contact regions preferably have a length of less than 20 mm, less than 10 mm or less than 5 mm. Preferably, the length is greater than 1 mm, 2 mm, 3 mm or 4 mm. The width is preferably less than 3 mm, less than 2 mm or less than 1 mm. Preferably, the width is greater than 0.5 mm, 1 mm, 2 mm, 3 mm or 4 mm.Punctiform raised contact regions preferably have an area of less than 5 mm 2, 4 mm 2, 3 mm 2, 2 mm 2 or 1 mm 2. Preferably, the area is greater than 0.5 mm 2, 1 mm 2, 2 mm 2, 3 mm or 4 mm 2.The recessed lubricant areas form the intermediate spaces between the raised contact areas and can be larger in their spatial extent than the raised contact areas.Preferably, a plurality or all of the recessed lubricant regions are structures connected to one another, which can also be understood as a comprehensive lubricant region surrounding a plurality of raised contact regions.Furthermore, a tripod ester according to claim 10 is proposed in the present case. In this case, the annular body is hardened only locally at partial sections pointing in the circumferential direction about the axis of rotation of the annular body in the region of the transition into the pins, wherein, with respect to a plane of symmetry of the tripod ester perpendicular to the axis of rotation of the annular body, the area proportion of the hardened partial section is greater on the load-bearing side than on the opposite side facing away from the load and preferably the annular body is otherwise uncured. In these subsection, increased component stresses likewise occur during operation, which can be met locally in a very targeted manner in this way. This makes it possible to dispense with complete hardening of the annular body. Local curing can be carried out, as explained above, in turn by induction curing, laser curing or electron beam curing. Accordingly, the annular body can be manufactured from a tempered steel. It is thus possible to integrate this process into a flow production process as well.The hardening of the running surface and neck of the stud can optionally take place on a machine in a working sequence and a component clamping / alignment.The asymmetrical configuration of the hardened segments takes into account the fact that a tripod ester is generally connected to a drive shaft and the greater loads occur on the side of the drive shaft.Here, hardening of the connection region for the drive shaft, generally in the form of an internal toothing, is preferably avoided, since the correction of hardness distortions is particularly complicated there.In particular, the partial sections can be limited to outer circumferential sections of the annular body which adjoin the pins.The local curing operations on the tripod ester presented above can also be integrated in combination in a flow production and avoid relevant hardness distortions, so that ultimately hard finishing of the tripod ester after curing can be omitted, while at the same time the energy input for curing and the outlay for component handling remain minimal. Moreover, the load-appropriate optimization further improves the service life and efficiency of the tripod ester.Ways of carrying out the invention will be explained in more detail below with reference to exemplary embodiments shown in the drawing and further modifications. The drawing shows in: FIG. 1 is a front view of a first embodiment of a tripod ester according to the invention, FIG. 2 shows a side view of the tripod ester from FIG. 1, FIG. 3 is a front view of a second embodiment of a tripod ester according to the invention, FIG. 4 shows a side view of the tripod ester from FIG. 3, FIG. 5 shows various patterns of surface structures, FIG. 6 shows further patterns of surface structures, and FIG. 7 is a side view of a third embodiment of a tripod ester according to the invention.The exemplary embodiments in FIGS. 1 to 4 and 7 each show a tripod ester 10 for a tripod joint, which can be used, for example, in a drive shaft of a passenger motor vehicle.The tripod ester 10 has an annular body 11 with an axis of rotation A. For connection to a drive shaft, a through opening 12 concentric to the axis of rotation A and preferably continuous internal toothing 13 can be provided on the annular body 11.Furthermore, the tripod ester 10 preferably has three pins 14 which project radially from the annular body 11. The pins 14 each have a longitudinal axis Z. Preferably, the longitudinal axes Z of all pins 14 intersect at a common point on the axis of rotation A of the annular body 11.Each of the journals 14 has a running surface 15 for a tripod roller, which is not illustrated in more detail but is known per se and is formed concentrically with respect to the longitudinal axis Z.The first exemplary embodiment illustrated in FIGS. 1 and 2 shows a tripod ester 10 for a so-called double-roller tripod joint. In such a roller, the tripod roller comprises an outer ring, an inner ring and roller bearings, by means of which the outer ring is rotatably mounted on the inner ring. The inner ring is in turn rotatably and pivotably mounted on the journal 14. For this purpose, the running surface 15 in the first exemplary embodiment has a spherical profile which has its largest diameter approximately in the middle of the length of the running surface 15 in the direction of the longitudinal axis Z of the pin 14.FIGS. 3 and 4 show, within the scope of a second exemplary embodiment, by way of example a tripod ester 10 for a so-called single tripod joint. In this case, the tripod roller comprises only one outer ring and also rolling bodies, by means of which the outer ring is rotatably mounted on the running surface 15. The running surface 15 is cylindrical here. As rolling bodies, for example, needles are used which have a linear contact with the running surface 15.In the tripod esters 10 of both exemplary embodiments, during operation the greatest loads occur on the journals 14, namely at those points which point in the rotational direction about the axis of rotation A of the annular body 11. In FIGS. 2 and 4, these main load ranges are each schematically delimited and identified by the reference symbol 16.To improve the lubricant supply in these regions, the running surfaces 15 are provided with a special surface structuring 17, which is explained in more detail below.In particular, the running surfaces 15 of the journals 14 each have a surface structuring 17 made of a multiplicity of raised contact regions 17 aand recessed lubricant regions 17 blocated between the multiplicity of raised contact regions 17 ain part of the respective running surface 15.The height between the raised contact regions 17 aand the recessed lubricant regions 17 bis many times greater than the surface roughness of the running surface in the remaining region 19 without said surface structuring 17.It has been found that even small height values from 50 μm are effective, which corresponds to approximately five times the averaged roughness depth Rz in the non-surface-structured region of the tread 15. In cut structures, the elevation can also be extended into ranges of a maximum of 1 to 1.5 mm. In general, height values of 50 to 1500 μm and preferably of 80 to 1000 μm are recommended.In the exemplary embodiments shown in FIGS. 1 to 4, the surface structuring is limited to an arcuate segment region of the running surface 15 on the respective journal 14. The relevant arc segment region extends about the longitudinal axis Z of the respective pin 14 over an angular range 30 to 140°. In the case of double tripod joints, this angular range is generally greater than in the case of single tripod joints.The relevant arc segment region preferably points in the circumferential direction about the axis of rotation A of the annular body 11, since the greatest loads generally occur in this direction. As shown in FIGS. 2 and 4, the pins 14 may be symmetrical to a plane perpendicular to the axis of rotation A of the annular body 11. The longitudinal axes Z of the pins 14 extend in this plane and meet at a common point on the axis of rotation A. The arc segment region can likewise be embodied symmetrically with respect to this plane of symmetry.In one embodiment variant, two partial regions 18 with said surface structuring 17 are arranged on a pin 14 opposite one another in the rotational direction about the rotational axis A of the annular body 11. This is advantageous in particular in the case of recuperation vehicles, in which considerable torques have to be transmitted in both rotational directions.In the first embodiment, the length h of said surface structuring 17 in the direction of the longitudinal axis Z of the pin 14 is limited to 20 to 60% of the total length of the pin 14 in the direction of the longitudinal axis of the pin. More preferably, the length h may be limited to a range of 25 to 45% of the total length.Furthermore, the surface structuring 17 on the spherical running surface 15 in FIG. 2 can be arranged in such a way that it extends over the region of the largest diameter of the running surface 15. Preferably, the center of the extension of the surface structuring 17 in the direction of the longitudinal axis Z of the pin 15 can coincide with the largest diameter of the running surface 15.Furthermore, it is possible to implement the surface structuring 17 in the aforementioned arc segment region with a diamond-shaped development. The height of the diamond shape of the partial region 18 with surface structuring and 17 in the longitudinal direction Z of the pin 15 can be smaller than its width in the circumferential direction about the longitudinal axis Z.The surface structuring 17 of the partial region 18 in FIG. 2 is illustrated in more detail in FIG. 5 with a multiplicity of variants a to i, without the invention being restricted to the variants specifically illustrated. As already explained above, the surface structuring 17 has a plurality of raised contact regions 17 a. In addition, at least one lubricant region 17 brecessed relative to the raised contact regions 17 ais provided, which directly adjoins the raised contact regions 17 a. The recessed lubricant regions 17 bmay be embodied as pockets which are independent of one another, for example, but may also be connected to one another and form a surrounding recessed lubricant region 17 bwhich surrounds a plurality or all of the raised contact regions 17 a.In this case, the area proportion of the raised contact regions 17 aon the partial region 18 with surface structuring 17 ais preferably smaller than the area proportion of the recessed lubricant regions 17 b. In particular, the surface proportion of the recessed lubricant regions 17 brelative to the entire partial region 18 can be in a range from 70 to 90%, in order to provide as much lubricant as possible.The raised contact regions 17 acan be linear and / or punctiform, as is illustrated by way of example in FIG. 5. These linear and / or punctiform raised contact regions 17a can be composed of a multiplicity of individual elements, in particular linear elements and / or point elements, which are arranged in different patterns.Line elements are understood to mean structures whose length is a multiple of their width. A point element is understood to mean not only circular geometries, but also polygons of any desired shape. In particular, geometries can be considered to be punctiform in which the ratio of the greatest to the smallest width lies in the range from 0.5 to 2.0.Linear raised contact regions (for short: line elements) preferably have a length of less than 20 mm, less than 10 mm or less than 5 mm. Preferably, the length is greater than 1 mm, 2 mm, 3 mm or 4 mm. The width is preferably less than 3 mm, less than 2 mm or less than 1 mm. Preferably, the width is greater than 0.5 mm, 1 mm, 2 mm, 3 mm or 4 mm.Punctiform raised contact regions (for short: point elements) preferably have an area of less than 5 mm 2, 4 mm 2, 3 mm 2, 2 mm 2 or 1 mm 2. Preferably, the area is greater than 0.5 mm 2, 1 mm 2, 2 mm 2, 3 mm or 4 mm 2.As shown in FIG. 5 by way of example in some variants, a plurality of line elements can be provided, which run parallel to one another. Furthermore, line elements may be provided which do not run parallel to one another.Individual line elements can be arranged parallel to the boundary of the diamond shape. Individual line elements can extend in the circumferential direction about the longitudinal axis Z of the pin 14. Individual line elements can also run parallel to the longitudinal axis Z of the pin 14.Individual line elements can each be free of intersections. However, it is also possible to cross individual line elements with one another.Moreover, arcuate line elements may be provided. If necessary, a plurality of arcuate line elements can be arranged concentrically with respect to one another.Dot elements may be arranged in regular patterns. Dot elements may also be arranged in irregular patterns.The dot members may be arranged so as to be adjacent to each other, respectively, so that a plurality of unbonded recessed lubricant portions 17b are formed therebetween. However, it is also possible to design the point elements such that the recessed lubricant regions 17 bare connected between the corresponding elevations, i.e. transfer channels for lubricant are formed through between the point elements to a certain extent. This also applies analogously to the line elements explained above.As shown in FIG. 5, variant i, by way of example, individual line elements can also extend beyond the subregion 18 with surface structuring 17. In particular, such line elements can be continued as far as a transition of the pin 14 into the annular body 11. Instead of line elements, a series of point elements or a pattern of point elements and / or line elements can also be continued out of the sub-region 18.The second exemplary embodiment in FIGS. 3 and 4 is directed to a single tripod joint in which a tripod roller is mounted via rolling bodies on the running surface 15 of a pin 14.In this case, it is recommended to choose the length h of said surface structuring 17 in the direction of the longitudinal axis Z of the pin to be in a range from 50 to 90% of the total length of the pin 14 in the direction of the longitudinal axis Z of the pin 14. Preferably, the developed view of the partial region 18 with surface structuring 17 can be triangular.FIG. 4 shows a triangular shape which has a greater extension in the direction of the longitudinal axis Z of the pin 14 than in the circumferential direction around the longitudinal axis Z. In particular, the triangular shape may be symmetrical with respect to the above-mentioned plane of symmetry. Further preferably, the triangular shape has its broad base towards the annular body 11, whereas an opposite tip of the triangular shape points away from the annular body 11.FIG. 6 illustrates by way of example various variants for the surface structuring 17 within the now triangular subregion 18, without the invention being restricted to these variants.Here too, the raised contact regions 17 acan be formed by a multiplicity of punctiform and / or linear individual elements which can be configured as already explained above in connection with FIG. 5.The raised contact regions 17 aof all exemplary embodiments are produced by local curing, in particular induction curing, laser beam curing or electron beam curing. The recessed lubricant portions 17 b, on the other hand, remain uncured. In this case, it is used that, in the aforementioned hardening methods, a volume increase in the microstructure of the material occurs as a result of martensite formation, as a result of which the raised contact regions 17 aprotrude with respect to the recessed lubricant regions 17 b.In addition, this achieves an increase in strength in the main load range of the running surface 15. Since the hardening in this case is limited to very small regions, namely preferably to said point elements and line elements, hardening distortions relevant to the function of the tripod ester 10 can be excluded. Hard finishing is therefore not required. In addition, the mass of the stud 14 may already be sufficient to dissipate the heat input sufficiently quickly after a local heat treatment in order to achieve the cooling rate required for the hardening. The process can be integrated into a flow production of a tripod ester 10.In a modification thereof, however, the surface structuring 17 explained above could also be produced by forming or by machining, followed by hardening, if appropriate only limited to the machined region, for example analogously to DE 10 2009 037 383 A1. However, any hardness distortions may have to be corrected subsequently here.In the exemplary embodiments shown in FIGS. 1 to 4, functional hardness distortions can be kept low due to the very local heat input or, as explained above, can be avoided practically completely. In particular, there is no longer any risk of impacts on the accuracy of the internal toothing 13, so that it has to be produced uncured and also no longer has to be remachined after any hardening process on the journal 14.The third exemplary embodiment in FIG. 7 shows a possibility in which the annular body 11 is hardened only locally at partial sections 19 pointing in the circumferential direction about the axis of rotation A of the annular body 11 in the region of the transition into the journals 14. These partial sections 19 are preferably limited to outer circumferential sections of the annular body 11 which adjoin the pins 14.With respect to the above-mentioned plane of symmetry perpendicular to the axis of rotation A of the annular body, the surface portion 19 aof the hardened partial sections 19 is larger on the load-bearing side than on the side 19 bfacing away from the load. Preferably, the degree of asymmetry is such that the ratio of the area fraction of one side to the area fraction of the other side is greater than 1:1.25, 1:1.3, or 1:1.5, and optionally less than 1:10, 1:8, or 1:5.The remaining annular body 11 preferably remains uncured.During operation of a tripod joint, increased component stresses occur in the subsection 19, which can be counteracted locally in a very targeted manner in this way.This makes it possible to dispense with complete hardening of the annular body 11. Local curing can, as explained above in connection with the first and second exemplary embodiments, be carried out again by induction curing, laser curing or electron beam curing.Accordingly, the annular body 11 can in turn be manufactured from a tempered steel. It is thus possible to integrate the process of curing the partial sections 19 into a flow production process.The asymmetrical configuration of the hardened segments takes into account the fact that a tripod ester 10 is generally connected to a drive shaft 20 and the greater loads occur on the side of the drive shaft 20.Here, hardening of the connection region for the drive shaft 20 is preferably avoided, usually in the form of the internal toothing 13 illustrated here by way of example, since the correction of hardness distortions is particularly complicated there.The local hardenings on the tripod ester 10 presented above can also be integrated in combination in a flow production and avoid relevant hardening distortions, so that ultimately hard finishing of the tripod ester 10 after hardening can be omitted, while at the same time the energy input for hardening and the outlay for component handling remain minimal. By optimizing in accordance with the load, moreover, the service life and efficiency of the tripod ester 10 can be further improved.The invention has been explained in more detail above with reference to exemplary embodiments and further modifications. In particular, technical individual features which have been explained above in the context of further individual features can be realized independently of these and in combination with further individual features, even if this is not expressly described, as long as this is technically possible. The invention is therefore expressly not restricted to the described exemplary embodiments and modifications, but rather comprises all the configurations defined by the patent claims.List of reference characters10 Tripod ester 11 Annular body 12 Through-opening 13 Internal toothing 14 Journal 15 Running surface 16 Main load region 17 Surface structuring 17 a Erhabene contact region 17 b Zurückgesetzt lubricant region 18 Partial region with surface structuring 19 Partial section h Length A Axis of rotation of the annular body 11 Z Longitudinal axis of the journal 14

Claims

Tripod ester (10) for a tripod joint, comprising an annular body (11) having an axis of rotation (A), and pins (14) which project radially from the annular body (11) and each have a running surface (15) for mounting a tripod roller in each case, wherein the running surfaces (15) of the pins (14) each have, partially, namely in a partial region (18) of the respective running surface (15), a surface structuring (17) comprising a multiplicity of raised contact regions (17a) and recessed lubricant regions (17b) lying between the multiplicity of raised contact regions (17a), and wherein the height between the raised contact regions (17a) and the recessed lubricant regions (17b) is many times greater than the surface roughness of the running surface (15) in the remaining region without said surface structuring (17), characterized in that, the raised contact areas (17a) are raised by local martensite formation with respect to the recessed lubricant areas (17b).Tripod ester (10) according to claim 1, characterised in that the surface structuring (17) is limited to an arcuate segment region of the running surface (15) which points in the circumferential direction about the axis of rotation (A) of the annular body (11) and is limited to an angular range of 30 to 120° with respect to a longitudinal axis (Z) of the respective journal (14).Tripod ester (10) according to claim 1, characterised in thaton a pin (14) two partial regions (18) with said surface structuring (17) are opposite each other in the direction of rotation about the axis of rotation (A) of the annular body (11).Tripod ester (10) according to claim 1 to 3, characterised in that the length of said surface structuring in the direction of the longitudinal axis Z of the pin is limited to 20 to 60% of the total length of the pin in the direction of the longitudinal axis of the pin, and / or the development of the partial region (18) with said surface structuring (17) is diamond-shaped.Tripod ester (10) according to claim 4, characterised in that the tripod roller comprises an inner ring, an outer ring and rolling elements arranged between them and is mounted with the inner ring on the running surface (15).Tripod ester (10) according to claim 1 to 3, characterised in that the length (h) of said surface structuring (17) in the direction of the longitudinal axis (Z) of the journal (14) is limited to 50 to 90% of the total length of the journal (14) in the direction of the longitudinal axis (Z) of the journal (14) and / or the development of the sub-region (18) with said surface structuring (17) is triangular, wherein, preferably, the tripod roller comprises an outer ring and rolling elements and the outer ring is mounted on the running surface (15) via the rolling elements.Tripod ester (10) according to one of claims 2 to 6, characterised in that the sub-region (18) covers the pitch circle radius PCR of the pins (15) and preferably its minimum length h ≥ PCR / 9.8.Tripod ester (10) according to one of Patent Claims 1 to 7, characterized in that the raised contact regions (17a) are of linear and / or punctiform design.Tripod ester (10) according to one of Patent Claims 1 to 8, characterized in that, in the region of the transition into the pins (14), the annular body (11) is hardened only locally at subsections (19) which point in the circumferential direction about the axis of rotation (A) of the annular body (11), wherein, with respect to a plane of symmetry of the pins (14) perpendicular to the axis of rotation (A) of the annular body (11), the proportion by area of the hardened subsection is greater on the load-bearing side than on the side facing away from the load and preferably the annular body (11) is otherwise uncured.Tripod ester (10) for a tripod joint, comprising an annular body (11) having an axis of rotation (A) and pins (14) which project radially from the annular body (11) and each have a running surface (15) for mounting a tripod roller, characterized in that the annular body (11) is hardened in the region of the transition into the pins (14) only locally at subsection (19) which point in the circumferential direction about the axis of rotation (A) of the annular body (11), wherein, with respect to a plane of symmetry of the pins (14) perpendicular to the axis of rotation (A) of the annular body (11), the area proportion of the hardened subsection is greater on the load-bearing side than on the side facing away from the load.

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