Portal axle for a rail vehicle and method for manufacturing such a portal axle

Description

[0001] The invention relates to a portal axle for a rail vehicle, comprising an axle center section extending along a longitudinal axis and two axle journals, one of which is located on a first end section of the axle center section and the other on a second end section of the axle center section opposite the first end section. The axle journals are oriented outwards away from the axle center section and, in use, form a pivot axis for a rail wheel rotatably mounted on the respective axle journal. The axle center section and the axle journals thus constitute the basic elements of the portal axle and are therefore referred to as the "form components" of the portal axle, regardless of whether the portal axle is manufactured in one piece or assembled from individual prefabricated components.

[0002] A portal axle to which the present invention relates may include additional form components. These include cheeks provided for supporting the axle journals on the axle center section, or support or support sections and the like, which may be provided for fastening or attaching functional components, such as components of a suspension system of the respective rail vehicle.

[0003] Portal axles of the type discussed here are used in particular as "inverted portal axles" for low-floor vehicles, such as trams or light rail vehicles.

[0004] In "inverted portal axles," the axle center section does not form a yoke from which the axle journals are suspended during use or which is supported on the axle journals. Rather, in inverted portal axles, the axle journals sit on the axle center section, so that the axle center section represents a beam on whose end sections the axle journals are supported. Examples of such portal axles are shown in EP 1 258 410 B1 and on the applicant's website at the URL https: / / www.bochumer-verein.de / die-bvv-niederflurradsaetze-mit-losradlagerung / (accessed November 9, 2021).

[0005] Due to their special design, in wheelsets with inverted portal axles, the space between the axle journals above the top of the axle center section in the operating position can be added to the height of a superstructure, particularly the passenger cabin, of the respective rail vehicle. This allows, for example, the floor height of the car body above the wheelset of low-floor rail vehicles to be lowered, thus offering passengers not only a low boarding height but also level passageways throughout the vehicle.

[0006] A particular challenge in the design of inverted portal axles for low-floor vehicles is that, on the one hand, the portal axles are subjected to high loads in use, but on the other hand, they should have the lowest possible weight in order to minimize the need for drive energy and achieve optimized driving behavior of the rail vehicle equipped with them.

[0007] Document EP 3 490 867 B1 describes a portal axle for a low-floor rail vehicle. Document EP 2 229 461 B1 describes an axle for rail vehicles forged from a seamless steel tube. Document CZ 20 920 U1 describes an axle for a rail vehicle. Document JP 2012 121505 A also describes an axle for a rail vehicle.

[0008] Based on the state of the art explained above, the task arose to specify a portal axis of the type described at the beginning, which has optimized performance characteristics with minimized weight.

[0009] Likewise, a method for manufacturing such a portal axis should be mentioned.

[0010] A portal axis solving this problem according to the invention has at least the features specified in claim 1.

[0011] A method that solves the aforementioned problem according to the invention is named in claim 11.

[0012] Advantageous embodiments of the invention are specified in the dependent claims and, like the general concept of the invention, are explained in detail below.

[0013] In accordance with the prior art explained above, a portal axle according to the invention for a rail vehicle thus has the following shape components: an axle center section extending along a longitudinal axis, and two axle journals, one of which is located on a first end section of the axle center section and a second of which is located on a second end section of the axle center section opposite the first end section, wherein the axle journals are oriented outwards away from the axle center section and in use form a pivot axis for a rail wheel rotatably mounted on the respective axle journal.

[0014] According to the invention, a longitudinal opening extending in the longitudinal direction of the portal axis is formed in at least one of the form components, i.e. at least in the axle center part and / or at least in one of the axle journals.

[0015] In accordance with the inventive design of a portal axis, an inventive method for manufacturing a portal axis designed according to one of the preceding claims comprises the following steps: a) Providing a portal axle blank comprising the mold components "axle center part" and "axle journal"; b) Creating a longitudinal opening in at least one of the mold components; c) Optionally treating the surface layer of the portal axle in the area of ​​an inner surface of the longitudinal opening and / or in the area of ​​an outer surface of the portal axle; d) Optionally oxidizing at least the inner surface of the longitudinal opening and / or in the area of ​​an outer surface of the portal axle.

[0016] The longitudinal opening formed in the central part of the portal axle and / or the axle journals of a portal axle according to the invention reduces the weight of the portal axle.

[0017] Secondly, the longitudinal opening provided according to the invention can be used for inspecting the portal axis. For example, the respective longitudinal opening allows a measuring device to be inserted into the interior of the respective molded component "axle journal" or "axle center part" for checking for cracks and similar damage originating from the component surface, thus enabling a targeted examination without having to remove the rail wheels mounted on the portal axis or perform other complex disassembly and assembly work.

[0018] The longitudinal opening provided according to the invention can be readily arranged in the respective mold component of the portal axle in such a way that there is no weakening of the stability of the individual mold component or of the portal axle as a whole. Rather, the longitudinal openings can be positioned in such a way that the section modulus of the axle center section and axle journal is increased by appropriately shaping the outer contours.

[0019] With a view to weight savings and the possibility of easy inspection from the inside of the respective mold component, it proves to be particularly advantageous if at least one longitudinal opening is molded into each of the mold components "axle journal" and "axle center part" of a portal axle according to the invention.

[0020] Weight savings and accessibility for inspection purposes can be optimized by designing the respective longitudinal opening as a through-hole that passes through the respective mold component.

[0021] Regarding the testability of a portal axis according to the invention, the advantage of the longitudinal openings provided in the portal axis according to the invention lies in the fact that the volume of the portal axis, which is subjected to bending during operation, can be inspected with high accuracy for cracks that have formed transversely to the direction of stress when installed. For this purpose, ultrasonic probes with an angle of incidence of 40° to 75° are typically used. When moved axially through the longitudinal openings, these probes can reliably detect crack formations that may originate from the outer surfaces of the axis, even in the assembled state.With conventional low-floor wheelsets, this would require a complex dismantling of the rail wheels and their loose wheel bearings in order to check, for example, the radius transitions from the axle journal to the associated cheek of the portal axle, which is particularly susceptible to cracking due to the notch effect, using a conventional surface crack test.

[0022] In cases where each axle journal has a longitudinal opening designed as a through-hole, weight savings can be maximized by having the longitudinal opening comprise a first section extending longitudinally from its opening associated with the axle's central section, and a second section extending to the free end face of the axle journal, the diameter of which is smaller than that of the first section. Such a stepped design of the longitudinal opening can also improve the reliability of crack detection using an ultrasonic measuring device inserted into the longitudinal opening, by positioning the larger-diameter section in an area where the axle journal, or the optionally supporting flange, has a larger volume.The larger diameter of the longitudinal opening section provided in this area allows the measuring device used for crack detection to be brought closer to the zone potentially susceptible to crack formation, even in a large volume area of ​​the cheek or axle journal.

[0023] The weight savings achieved in the axle center section can be maximized by forming at least two longitudinal openings into the axle center section, preferably extending parallel to each other and parallel to the longitudinal axis of the axle center section. In this design, the longitudinal openings are also advantageously configured as through-openings, leading from the side of the axle center section associated with one axle journal to the side associated with the other axle journal, in order to maximize weight savings and optimize accessibility. The diameters of two or more longitudinal openings in the axle center section can differ if this is necessary for static or space reasons.For example, a centrally located longitudinal opening of larger diameter, relative to a cross-section oriented transversely to the longitudinal axis of the axle's central section, can be combined with one or two longitudinal openings of smaller diameter arranged to either side of it. Preferably, the number of longitudinal openings formed in the axle's central section is limited to a maximum of three. This applies particularly when the longitudinal openings are designed as through-holes.

[0024] A portal axle according to the invention is particularly intended to be used as an "inverted portal axle" for a low-floor wheelset. The use of an inverted portal axle ensures that both wheels of the respective wheelset run on the same central axis, thereby avoiding track and camber deviations that, when using independent wheel suspensions, can negatively affect the tracking behavior of the rail vehicle on the track.

[0025] In the case that a portal axle according to the invention is used as an "inverted portal axle" for low-floor wheelsets, the axle center section has a top surface that, in use, is associated with a superstructure of the rail vehicle, on which the axle journals are located. The axle journals can be supported by cheeks that stand on the end section of the axle center section associated with the respective axle journal, and from which the axle journals project laterally outwards away from the axle center section. The cheeks supporting the outwardly projecting axle journals allow the axle center section to be lowered relative to the axis of rotation defined by the axle journals, thus maximizing the space available for positioning the chassis or superstructure of the rail vehicle above the axle center section of the portal axle.At the same time, the cheeks can be used, for example in the case of internally mounted wheelsets, to support the primary suspension, via which the wheelset equipped with the portal axle in question is supported on the chassis.

[0026] In principle, it is conceivable to assemble a portal axis of the type according to the invention from individually prefabricated mold components.

[0027] Given that a portal axle according to the invention must reliably transmit all stresses occurring during operation between the track and the vehicle throughout the entire service life of the rail vehicle, it has proven advantageous for the portal axle according to the invention, including its components, to be manufactured in one piece from a single steel material. For this purpose, forging and / or casting the blank from a suitable steel material is appropriate.

[0028] Due to the mechanical properties achievable through forging, the axle center section, including the optionally formed webs of the portal axle, is preferably forged in one piece. The axle journals can be forged in one piece onto the axle center section or, in particular, onto the optional webs. Alternatively, the axle journals can also be pressed, shrunk-fitted, or adhesive-shrink-fitted into appropriately provided openings in the optional webs or the axle center section. Suitable steel materials for the forging of a portal axle according to the invention include, in particular, the heat-treatable steels specified in DIN EN ISO 683. Preferably, the steel grades 30CrNiMo8, 34CrNiMo6, 42CrMo4, 25CrMo4, or C45 are used.

[0029] After forging, the resulting portal axle blank can be subjected to heat treatment to impart the mechanical properties required by standards or other regulations. This heat treatment typically includes stress-relief annealing, which prevents distortion that could otherwise occur during subsequent machining processes due to released residual stresses. Such heat treatment, particularly stress-relief annealing, can also be performed as an intermediate or additional step between individual machining steps of the portal axle after forging, if required.

[0030] The longitudinal openings can be formed into the axle journals and / or the axle center section in any manner known from the prior art. In particular, known drilling or comparable machining processes are suitable for this purpose.

[0031] In order to avoid damage to the portal axis caused by corrosive attacks in the area of ​​its respective longitudinal opening provided according to the invention and to ensure optimal coupling of the measuring device to the area to be examined during crack testing, the longitudinal opening can be treated with corrosion protection at least on its inner surface.

[0032] In principle, it would be conceivable to apply a conventional corrosion protection agent, such as a paint coating, to the corrosion-prone area for this purpose. However, coating longitudinal openings is complex, and the quality of the result can only be verified with considerable effort. Furthermore, such an additional coating would have to be removed every time a crack is inspected, especially if this is to be done using ultrasound.

[0033] According to a particularly relevant embodiment for practical purposes, the invention therefore proposes to subject the longitudinal opening provided according to the invention to a chemical / thermal heat treatment process after the mechanical processing has been carried out, which achieves not only a significant increase in the component strength but also a high resistance to corrosion attack.

[0034] The surface layer treatment is preferably carried out as a chemical / thermal surface layer treatment, in which, in a known manner, the surface layer is hardened by diffusion of, for example, nitrogen and / or carbon atoms into the surface layer, initiated and supported by heat input. The methods available for this purpose are known from the prior art (see, for example, the German Steel Information Centre (Stein) 447 "Heat Treatment of Steel - Nitriding and Nitrocarburizing", 2005 edition, ISSN 0175-2006, published by the Steel Information Centre, Düsseldorf, Germany) and, in connection with the field of technology under discussion here, are described, for example, in EP 1 769 940 B1, which relates to a surface-hardened wheel axle for railway vehicles. Preferably, the surface layer treatment is carried out as gas, bath, or plasma nitriding.

[0035] Here it has been shown that corrosion protection can be achieved particularly effectively by a thermal / chemical surface layer treatment, as a result of which the portal axis according to the invention has a hardness in a surface layer bordering the respective inner surface of the longitudinal opening, at least in the area of ​​the inner surface of the respective longitudinal opening, which is increased compared to the hardness that the portal axis has in a core area outside the surface layer.

[0036] The surface layer treatment optionally carried out according to step c) of the inventive method is limited, according to a first variant of the inventive method, only to the respective longitudinal opening.

[0037] Alternatively, the surface treatment carried out in step c) can also cover an outer surface of the portal axis that is exposed to particular corrosive or mechanical stresses during use. The surface treatment can be limited to a specific section of the portal axis, but preferably it should be carried out so that the entire outer surface of the portal axis is treated.

[0038] A particular advantage of the optional surface layer treatment provided according to the invention is achieved when, after step b) of the inventive method, not only the longitudinal openings of the portal axis are treated with this surface layer in step c), but the entire portal axis. By treating the entire portal axis with a surface layer, the fatigue strength of the portal axis can be increased by 10 to 40%, especially in the more heavily notched areas, such as in the area of ​​the transition from the axis center section to the cheeks or, in the case of a forged axle journal, in the area of ​​the transition from the axle journal to the cheek supporting it.The increase in strength achievable through the surface layer treatment provided according to the invention is particularly advantageous for portal axles that, due to the limited available installation space, have small transition radii and are therefore highly susceptible to cracking caused by notch effects. Specifically in the area of ​​the bearing seats of the axle journals, a fatigue strength increase of up to approximately 60% can be achieved by combining the surface layer treatment of the axle journals with a subsequent coating of the bearing seats with a molybdenum spray layer. In portal axles with joined axle journals, in addition to the portal axle itself, the axle journals, which have stress-increasing depressions and steps on their surface due to the bearing and sealing seats, are also expediently subjected to a corresponding surface layer treatment.

[0039] By applying an edge layer treatment of the type described above to the entire portal axle, a significantly increased fatigue strength can be achieved compared to portal axles without such treatment. This allows a portal axle according to the invention to have considerably smaller cross-sections while maintaining the same load-bearing capacity. This also effectively reduces the installation space required for the portal axle itself in the area between the wheels. The space gained for the design of the chassis or the superstructure of the rail vehicle can be used in low-floor vehicles used as trams or light rail vehicles for wider passageways in the car body, thus increasing customer satisfaction.

[0040] Simultaneously, if a surface layer treatment carried out as described above also covers the outer surfaces of the portal axle, as is the case with a surface layer treatment that covers the entire portal axle, a high level of corrosion resistance is also achieved in the area of ​​these outer surfaces. Practical experience shows that the corrosion resistance achieved in this way is sufficient to forgo additional corrosion protection coatings for the portal axle. At the same time, the hardness achieved by the surface layer treatment in the area of ​​the surface layer, and consequently the resistance on the exposed surfaces of the portal axle, is so high that the portal axle is adequately protected against external mechanical attacks, such as stone impacts caused by flying ballast.In conventional, untreated portal axles, damage caused by such attacks results in highly stress-increasing notches that promote crack formation if they are not regularly repaired at short intervals. The optional surface treatment proposed according to the invention allows inspection intervals to be significantly extended, resulting in considerable cost savings.

[0041] Additionally, corrosion protection in the area of ​​the longitudinal opening provided according to the invention can be optimized if at least the inner surface of the longitudinal opening is provided with an oxide layer. Similarly, corrosion resistance can also be enhanced in the area of ​​at least one outer surface of the portal axis by the targeted formation of an oxide layer. The respective oxide layer can be generated, for example, by targeted oxidation of the compound layer that forms on the component surface during the surface treatment of the mold components. For this purpose, it has proven effective to oxidize the compound layer after the surface treatment of the mold components with the addition of oxygen at temperatures between 350 °C and 570 °C.In this process, the free iron molecules and iron nitrides react with the introduced oxygen to form stable iron oxide, which is deposited as a thin oxide layer on the surface of the component. Any pores in the compound layer are filled with oxide. This layer is extremely chemically resistant and gives the molded components particularly high corrosion resistance. Wheelsets equipped with portal axles designed according to the invention are lighter than wheelsets with conventional portal axles. Low wheelset weights mean lower unsprung mass and therefore less vibration when, for example, a tram equipped with such a wheelset travels through a residential area. At the same time, the reduced weight lowers the consumption of drive energy and minimizes wear on the vehicle and track.

[0042] A wheelset formed using a portal axle according to the invention, which in use is particularly employed in an inverted arrangement, for use in rail vehicles in which the connection of the portal axle to the chassis is made inside, i.e. between the wheels, therefore comprises an inverted portal axle designed according to the invention and two rail wheels which are typically mounted on the two axle journals of the portal axle by means of tapered roller bearing units.

[0043] In the case of wheelsets with braked rail wheels, brake caliper hubs can additionally be provided on the portal axle according to the invention. These hubs secure the bearings against axial displacement and each has a brake caliper mounted on it, attached to a braking device for braking the rail wheels. Brake discs are attached to the rail wheels, and the braking device acts on these discs during braking.

[0044] In the case of driving wheelsets, i.e., wheelsets with driven rail wheels, drive couplings are provided instead of brake discs and brake caliper hubs. These couplings connect the respective rail wheel to the drive system of the rail vehicle. The bearing fixation of each driven rail wheel can be achieved similarly to brake caliper hubs, either via a longitudinal or transverse press fit with a hub or by means of a bearing retainer cap that is bolted to the axle journal. This axial fixation can be accomplished using either a central bolting connection or a direct bolting connection.The advantage of retaining the brake caliper seat on the axle journal for bearing fixation is that the portal axles for the drive and running wheel sets of a vehicle can be designed identically; the disadvantage is that the brake caliper hub seats require additional clearance and, when using the bolted solution, more space remains within the vehicle's clearance profile for the drives.

[0045] Furthermore, to standardize the bearing fixing, particularly for unbraked wheelsets, it is conceivable to use appropriately designed bearing locking caps, as with the driving wheelsets. For braked wheelsets, the brake calipers could also be mounted on the chassis frame. However, this would have the disadvantage that the primary suspension between the chassis and the low-floor wheelset would affect the contact surface between the brake pad and friction ring.

[0046] Alternatively, the bearing retaining caps could be designed to also accommodate the brake calipers. In this case, the bearing retaining caps must be connected to the axle journals in such a way that the high torques resulting from the braking forces are transmitted without rotation. This rotational resistance can be achieved either through a face or longitudinal spline connection between the axle journals and bearing retaining caps, designed to accommodate brake calipers, or, depending on the torques to be transmitted, through solutions using dowel pins or heavy-duty clamping sleeves.

[0047] Braking and drive devices of the type mentioned here, as well as their individual components, operation, and assembly, are known to those skilled in the art from the prior art. It is not necessary for both rail wheels mounted on a portal axle according to the invention to be braked or driven. Rather, in the case of unbraked wheelsets, the brake discs and devices for mounting brake calipers can be omitted. In the case of wheelsets braked on only one side, a brake caliper hub and, optionally, a hub for axial bearing fixation can be provided for only one rail wheel. Similarly, it is possible to couple a single-sided driven drive wheelset of only one of the rail wheels mounted on the portal axle according to the invention to the drive of the rail vehicle via a suitable coupling device, while the other rail wheel mounted on the portal axle rotates freely without brakes or drive during operation.Alternatively, in a single-sided driven driving wheelset, one rail wheel mounted on the portal axle can be driven, and a brake disc and brake caliper hub can be provided for the other rail wheel in order to be able to brake it in use by means of a suitable braking device.

[0048] For low-floor wheelsets that have external bearings due to the track width or vehicle design, the design is limited to wheelsets with and without brake discs. In these cases, the axle journal is extended outwards beyond the seat for receiving the brake caliper hub, or, optionally in the case of unbraked loose wheels, the hub for axial fixation of the bearing without a mounting device for brake caliper hubs, in order to provide an additional seat for receiving the axle bearing.

[0049] The rail wheels of wheelsets equipped with portal axles according to the invention can be designed as rubber-sprung wheels, as described for example in DE 33 28 321 C2, or, preferably, as hybrid wheels, as shown in WO 2018 / 046745 A1.

[0050] The invention will now be explained in more detail with reference to a drawing illustrating an exemplary embodiment. The drawing schematically shows: Fig. 1 a portal axle for a wheelset of a low-floor rail vehicle; Fig. 2 a section of the portal axle in a cross-section along the Fig. 1 the longitudinal axis LL of the portal axis is shown; Fig. 3 shows a section of an alternative design of the portal axis in one of the Fig. 2 corresponding sectional view; Fig. 4 the portal axis in a frontal view; Fig. 5 the portal axis in a longitudinal section along the in Fig. 4 drawn section line AA.

[0051] The portal axle 1 is forged in one piece from a suitable heat-treated steel composed according to DIN EN ISO 683. The portal axle 1 has an axle center section 2, which has the basic shape of a flat cuboid with a length L extending along a longitudinal axis LL, which is greater than the width B of the axle center section 2.

[0052] The axle center section 2 has a top surface 3, which in use is assigned to a chassis of a low-floor rail vehicle (not shown here), also not shown here. In the end sections 6, 7 of the axle center section 2, which adjoin the narrow sides 4, 5 of the axle center section 2, there is a cheek 8, 9, which is formed in one piece with the axle center section 2. In the longitudinal side view ( Fig. 5 ) the portal axis thus has the basic shape of a "U", the legs of which are formed by the cheeks 8,9 and the base of which is formed by the axis middle part 2.

[0053] In an initial embodiment, whose longitudinal section in Fig. 2 and 5 As shown, an axle journal 10, 11, pointing outwards away from the axle center section 2, is integrally forged onto each of the cheeks 8, 9. The longitudinal axes L10, L11 of the axle journals 10, 11 are coaxial with each other and aligned parallel to the central longitudinal axis LL of the axle center section 2.

[0054] The axle journals 10,11, the cheeks 8,9 and the axle center part 2 form components that together form the portal axle 1.

[0055] During the Figure 1 , 2 , 4 and 5 In the embodiments shown, a longitudinal opening 12,13 is drilled into each of the axle journals 10,11, which leads as a through-opening with constant opening cross-section from the free end face 14,15 of the respective axle journal 10,11 to the side surface 16,17 of the cheek 8,9 supporting the respective axle journal 10,11 which faces the axle center part 2.

[0056] In addition, two longitudinal openings 18, 19 are drilled into the axle center section 2, starting from its narrow side 4, which is associated, for example, with the cheek 8. These through-holes extend from the narrow side 4 to the opposite narrow side 5 of the axle center section 2 and are aligned parallel to each other and to the longitudinal axis LL of the axle center section 2, such that they are equidistant from their nearest adjacent longitudinal side 20, 21 of the axle center section 2. The diameter of the longitudinal openings 18, 19 is dimensioned such that there is a minimum wall thickness WDmin between the upper surface 3 and the opposite lower surface 23 of the axle center section 2, which corresponds to 0.1 to 0.25 times the distance AB between the upper surface 3 and the lower surface 23 (0.1 x AB ≤ WDmin ≤ 0.25 AB). For example, in practice the wall thickness WD is equal to 0.125 times the distance AB between top 3 and bottom 23 (WD = 0.125 x AB).

[0057] Following the forging of the portal axle 1 in the usual manner, a heat treatment carried out in the same known manner to adjust the mechanical properties, a stress-relief annealing also carried out conventionally, the drilling of the longitudinal openings 12, 13, 18, 19 and the mechanical finishing of the entire outer contour of the portal axle except for the seats for bearings, seals and brake caliper hubs, which were then coated with molybdenum, the portal axle 1 was subjected to a surface coating treatment.

[0058] In this surface layer treatment, portal axis 1 was nitrided for a duration of 84 h at a temperature of 520 °C under an atmosphere consisting of ammonia gas. Subsequently, the portal axis was subjected to a conventional oxidation process.

[0059] After the surface treatment, the portal axis 1, including the inner surfaces of the longitudinal openings 12, 13, 18, 19, exhibited a Vickers hardness of 790 HV, higher than that of the base material (340 HV). The total thickness of the surface layer was approximately 0.7 mm.

[0060] The surfaces were subsequently subjected to various corrosion tests and impact tests with ballast to verify their impact resistance. Compared to conventional portal axles, the surface-treated axle showed no signs of corrosion in either salt spray tests or after being exposed to extreme conditions in an acidic atmosphere for three months. The impact tests were conducted with track ballast at speeds of up to 360 km / h. The component surfaces remained undamaged afterward.

[0061] The in Fig. 3The alternative design of a portal axis shown here relies on the one in the Figure 1 , 2 , 4 and 5 The portal axis 1 shown. The cheeks 8' of the alternatively designed portal axis each carry a separately prefabricated axle journal 10', which is shrunk into an opening 22' provided in the respective cheek 8' in a manner known per se or is fixed in another suitable manner. How the axle journal 10 is attached in the Fig. 2 In the illustrated embodiment, the axle pin 10' also has a longitudinal opening 12', which leads from the free end face 14' to the side surface 16' of the cheek 8', which is assigned to the axle center part 2' of the portal axle.

[0062] In contrast to the longitudinal opening 12, 13 of the axle journals 10, 11 with its constant opening diameter, the longitudinal opening 12' of the axle journal 10' has, starting from the side surface 16' of the cheek 8' associated with the axle center section 2', a first section 12a' which transitions via a conically tapered shoulder into a second section 12b', which extends to the free end face 14a' of the axle journal 12'. The first section 12a' has a larger diameter than the second section 12b' and extends in the area of ​​the axle journal 10' where the axle journal 10' has its largest volume.

[0063] For the sake of clarity, the alternative configuration with the prefabricated axle journal 8', which is shrunk into the opening 22' of the cheek 8', is shown here only for the first end section 6' of the portal axle in question, the shape and construction of which otherwise corresponds to portal axle 1. Naturally, a correspondingly designed arrangement of cheek and axle journal is located at the other end section 7 of portal axle 1. Here, too, the cheeks 8' and the corresponding cheek on the other side of the axle center section 2' (not shown here) are each formed by forging in one piece with the axle center section 2'. REFERENCE MARK

[0064] Figure 1 , 2 , 4, 5 : 1 Portal axis 2 Axle center section 3 Top of axle center section 2 4,5 Narrow sides of axle center section 2 6,7 End sections of axle center section 2 8,9 Cheeks 10,11 Axle journals 12,13 Longitudinal openings of the axle journals 10,11 14,15 Free end faces of the axle journals 10,11 16,17 Side surfaces of the cheeks 8,9 18,19 Longitudinal openings 20,21 Longitudinal sides of axle center section 2 23 Bottom of axle center section 2 B Width of axle center section 2 L Length of axle center section 2 L Longitudinal axis of axle center section 2 L10,L11 Longitudinal axes of the axle journals 10,11

[0065] Fig. 3 : 2'Center section of axle 6'End section of axle center section 2' 8'Side of the alternatively designed portal axle 10'Axle journal of the alternatively designed portal axle 12'Longitudinal opening of the axle journal 10' 12a'First section of the longitudinal opening 12' 12b'Second section of the longitudinal opening 12' 14'Free end face of the axle journal 10' 16'Side surface of the side 8' 22'Opening of the side 8'

Claims

1. Portal axle for a rail vehicle, with the following moulded components: - an axle centre part (2) extending along a longitudinal axis (L-L), and - two kingpins (10, 11, 10'), one of which sits on a first end section (6) of the axle centre part (2) and a second on a second end section (7) of the axle centre part (2) formed opposite to the first end section (6), wherein the kingpins (10, 11) are oriented away from the axle centre part (2) and form an axis of rotation in use for a rail wheel rotatably mounted on the respective kingpin (10, 11), - wherein the axle centre part (2) has an upper side (3) assigned to a body of the rail vehicle in use and wherein the kingpins (10, 11) are positioned on the upper side (3) of the axle centre part (2) and - wherein a longitudinal opening (12, 13, 18, 19, 12') extending in the longitudinal direction of the portal axle (1) is formed in at least one of the mould components (2, 10, 11, 10'), characterized in that at least one longitudinal opening (12, 13, 18, 19, 12') is moulded into the mould components (2, 10, 11, 10') and in that the longitudinal opening (12, 13, 18, 19, 12') is designed as a through-opening that passes through the respective mould component (2, 10, 11, 10').

2. Portal axle according to claim 1, characterised in that the kingpins (10') each have a longitudinal opening (12') formed as a through-opening and in that the longitudinal opening (12') has a first section (12a') extending in the longitudinal direction of the longitudinal opening (12') and a second section (12b') extending up to the free end face of the kingpin originating from its outlet assigned to the axle centre part (2), the diameter of which is smaller than the diameter of the first section (12a')3. Portal axle according to any one of the preceding claims, characterised in that at least two longitudinal openings (18, 19) are moulded into the axle centre part (2).

4. Portal axle according to any one of the preceding claims, characterised in that it is manufactured from a steel material with its moulded components (2, 8, 9, 10, 11, 10') in one piece.

5. Portal axle according to claim 4, characterised in that the longitudinal opening (12, 13, 12') is treated with corrosion protection at least on its inner surface.

6. Portal axle according to either claim 4 or claim 5, characterised in that it has a hardness at least in the region of the inner surface of the longitudinal opening (12, 13, 18, 19, 12') in an edge layer adjacent to the respective inner surface of the longitudinal opening (12, 13, 18, 19, 12') which is increased as a result of a chemical / thermal edge layer treatment compared to the hardness that the portal axle (1) has in a core region present outside the edge layer.

7. Portal axle according to any one of claim 4 to claim 6, characterised in that at least the inner surface of the longitudinal opening (12, 13, 18, 19, 12') is provided with an oxide layer.

8. A method for producing a portal axle (1) according to any one of the preceding claims, comprising the following work steps: a) provision of a portal axle blank comprising the "axle centre part" and "kingpin" moulded components; b) introduction of a longitudinal opening in at least one of the mould components (2, 10, 11, 10'); c) optional edge layer treatment of the portal axle (1) in the region of an inner surface of the longitudinal opening (12, 13, 18, 19, 12') and / or in the region of an outer surface of the portal axle (1); d) optional oxidation of an inner surface of the longitudinal opening (12,13,18,19,12') and / or an outer surface of the portal axle (1).

9. Method according to claim 8, characterised in that the portal axle (1) is subjected to edge layer treatment throughout after the longitudinal opening (12, 13, 18, 19, 12') has been introduced.

10. Method according to either claim 8 or claim 9, characterised in that work step c) is carried out as chemical / thermal edge layer treatment.

11. Method according to claim 10, characterised in that the edge layer treatment increases the N and / or C content at least in the region of the inner surface of the longitudinal opening (12, 13, 18, 19, 12') in an edge layer adjacent to the respective inner surface of the longitudinal opening (12, 13, 18, 19, 12').

12. Method according to claim 8 to claim 11, characterised in that the provision of the portal axle blank (work step a)) comprises forging and / or casting the blank from a steel material.