METHOD FOR MANUFACTURING AN AXLE BODY OF A VEHICLE AXLE AND AXLE BODY OF A VEHICLE AXLE

Description

[0001] The invention relates to a method for producing an axle body of a vehicle axle by materially connecting an axle tube to a steering knuckle arranged on the longitudinal axis of the axle tube, which steering knuckle is provided with bearing surfaces for supporting a vehicle wheel and has a tube cross-section facing the axle tube which is substantially equal to the tube cross-section of the axle tube.

[0002] Furthermore, the invention relates to an axle body of a vehicle axle, which can preferably be produced by such a method, consisting of an axle tube and a steering knuckle provided with bearing surfaces for the mounting of the respective vehicle wheel, which has a tube cross-section facing the axle tube which is substantially equal to the tube cross-section of the axle tube, and wherein the two tube cross-sections are placed against one another and connected to one another in a materially bonded manner via a weld seam.

[0003] An axle beam produced by welding is described in EP 2 133 164 B1 as one possible embodiment. Wheel-receiving sections, also generally referred to as steering knuckles, are attached to both ends of a central axle tube. The tube cross-sections of the wheel-receiving sections are identical to the tube cross-sections of the central axle tube in the connection area. The connection is made by a welding process, with EP 2 133 164 B1 primarily mentioning a friction welding process. However, it is also prior art to use a conventional arc welding process for the integral connection of the steering knuckle. US 2004 / 185946 A1 also discloses a method for producing an axle beam of a vehicle axle by welding an axle tube to a steering knuckle arranged on the longitudinal axis of the axle tube.

[0004] Axle beams, especially when used as commercial vehicle axles, are subject to strong dynamic bending loads as well as braking-related torsional loads. The load condition prevailing in the axle beam is different on the top side of the axle beam, where compressive loads prevail, than on the underside of the axle beam, where tensile loads primarily act. Conventional welding methods, as well as friction welding, do not take these different load conditions into account. This disadvantage is only partially offset by the fact that such an axle beam can be installed in any rotational position in the axle structure, i.e. without distinguishing which circumferential section of the axle beam is at the bottom in the area of ​​primarily tensile loads and which circumferential section is at the top in the area of ​​primarily compressive loads.However, this advantage is only an apparent one, since in many axle bodies the rotational position is already determined by add-on parts such as brake carriers and must be taken into account during axle assembly.

[0005] Based on this situation, the invention is based on Task The aim is to develop a welding process optimized for the production of an axle beam from an axle tube and an attached steering knuckle, with respect to the dynamic driving loads to which the axle beam is typically exposed during operation. Furthermore, a corresponding axle beam is to be created, particularly suitable for a commercial vehicle axle.

[0006] To achieve this object, a manufacturing method having the features specified at the outset is proposed, which is characterized by the features of claim 1.

[0007] Furthermore, an axle body of a vehicle axle, such as can be produced by this method, is proposed. Such an axle body consists of an axle tube and at least one steering knuckle provided with bearing surfaces for supporting the respective vehicle wheel, which has a tube cross-section facing the axle tube that is essentially equal to the tube cross-section of the axle tube.The two pipe cross-sections are placed against each other and joined together by a weld seam, wherein the weld seam extends from the outside of the pipe cross-sections to a weld seam root arranged on the inside of the pipe cross-sections, and the weld seam extends over the entire circumference of the axle body with a first weld seam section running over approximately half of the circumference and a second weld seam section running over the rest of the circumference, and wherein the weld seam root on the inside of the pipe has a burr of molten material protruding towards the inside of the pipe along the first weld seam section, and a comparatively smooth seam along the second weld seam section.

[0008] A key aspect of the invention is the use of a dual welding process by combining a conventional arc welding device with a parallel, i.e., simultaneously operated laser welding device. Furthermore, both welding devices operate from the outside on approximately the same circumferential section of the axle body. The beam direction of the laser beam is such that the laser beam is perpendicular to the longitudinal extension of the axle tube, thus striking the outer side of the tube at a right angle. Preferably, it intersects the longitudinal axis of the axle tube.

[0009] Another special feature is that, although a weld seam is drawn across the entire circumference, the remaining secondary energy of the laser beam is only used on a partial circumference, which amounts to approximately half the total circumference, to rework the weld seam, which is prone to significant root formation on the inside of the pipe. The energy (secondary energy) of the laser beam still impinging on the inside of the pipe is used to remove, smooth, and even out the burr of molten material that has formed in the area of ​​the weld seam root. This smooths the weld seam root here, which further improves the material bond between the two pipe ends on this circumferential segment and reduces notch effects, thus enabling particularly good resistance to tensile loads.

[0010] As a result, after the welding process has been completed, which occurs once a circumferential angle of between 360° and 370° has been reached, a first partial circumference will be present on the inside of the pipe. This is characterized by a clearly visible burr of molten material at the weld root, as well as a second partial circumference on which the inside of the pipe is comparatively smoother. Tests have shown that the quality of the weld is further improved on the second circumferential segment, i.e. the circumferential segment on the inside of the pipe smoothed using the laser beam. Therefore, the axle beam is installed in the chassis, and in particular in the commercial vehicle chassis, such that the second circumferential segment is at the bottom during driving operation, thus being located where the critical tensile loads primarily occur.

[0011] Overall, therefore, a welding process is achieved that is optimized for the production of an axle body from an axle tube and a steering knuckle attached to it with regard to the typical driving dynamic loads to which the axle body is exposed during driving.

[0012] To ensure a load-optimized installation position during subsequent assembly of the axle beam in the commercial vehicle chassis, the axle beam can be provided with at least one marking on the outside, which is clearly assigned to the partial circumference on which the first, unsmoothed weld seam section is located and / or the partial circumference on which the second, smoothed weld seam section is located. For example, such a marking, in words or symbols, can stand for "top" and / or "bottom," thus providing the installer with clear installation instructions during axle assembly. Further advantages and details are explained below using an example. Reference is made to the drawings. These show: Fig. 1 in a greatly shortened view of an axle body as used in a non-driven commercial vehicle axle of a commercial vehicle trailer; Fig. 2in a highly simplified overview representation of a dual-operated welding arrangement for the production of the axle body, with the individual objects shown in the welding plane; Fig. 2a the items after Fig. 2 with further details; Fig. 3a - 3c in the welding plane, individual stages of the welding process, and Fig. 4 a section through the axle body along its longitudinal extent, here in

[0013] Area of ​​the welded joint between the axle tube and the steering knuckle. Fig. 1The axle beam shown, designed here as a continuous axle beam for a non-driven commercial vehicle axle, consists of a total of three longitudinal sections. The central longitudinal section is formed by a steel axle tube 1. A steering knuckle 2 is attached to each of the two open ends of the axle tube 1 by means of a welding process described in more detail below. Each steering knuckle 2 is preferably made of steel and is provided with bearing surfaces 3 for bearing components, for example for the rolling bearings of the respective vehicle wheel and / or for the bearing of a brake drum or a brake disc of a disc brake. Furthermore, a brake carrier of a drum brake or disc brake can be attached to the steering knuckle 2.

[0014] Axle tube 1 is cut to its length by sawing. The saw cut is perpendicular to the longitudinal extension of the axle tube. This results in a sawn butt joint, which is suitable for the subsequent welding process without further treatment.

[0015] In addition, the axle tube 1 is provided with a hole 4, preferably 4 to 10 mm in diameter, to prepare for welding. Hole 4 connects the interior of the axle tube to the environment. It serves as a vent for generated welding gases during the welding process.

[0016] Hole 4 will no longer be needed in the finished product. It will therefore be sealed later to prevent moisture and dirt from entering the axle tube. The hole or vent opening 4 can also be installed in the steering knuckle 2 instead of the axle tube 1.

[0017] Each steering knuckle 2 also has a tubular cross-section at its end facing the axle tube 1. This tubular cross-section is essentially the same as the tubular cross-section of the axle tube 1 and is arranged on the same longitudinal axis L. Since the steering knuckle 2 is a cast or forged part, the open tubular cross-section of the steering knuckle 2 is prepared by a machining process, such as overturning. The annular end face of the steering knuckle 2 is therefore a surface prepared by a machining process.

[0018] Before the welding process, the steering knuckle 2 is provided with holes for the subsequent attachment of an ABS holder. If, as shown, the two tube cross-sections are round, the inner diameter Dsi of the tube cross-section on the steering knuckle 2 is approximately equal to the inner diameter DR of the axle tube 1. Likewise, the outer diameter Ds a of the tube cross-section on the steering knuckle 2 is approximately equal to the outer diameter DR 3 of the axle tube 1.

[0019] In the connection area 5, the material connection of the pipe cross-sections involved takes place, thus permanently fastening the steering knuckle 2 to the respective end of the axle tube 1. The connection is carried out using a dual welding process. To carry out this process, the welding arrangement 10 used has a Fig. 2not illustrated workpiece holder, in which the axle tube end and the steering knuckle 2 can be fixed in coaxial alignment on the longitudinal axis L, furthermore via an arc welding device 11 and finally via a parallel, ie simultaneously operable laser welding device 12. Preferably, the two welding devices 11 and 12 are fastened to a common tool carrier, relative to which the workpiece holder is rotatable about the longitudinal axis L of the axle body.

[0020] First, the axle tube end and the steering knuckle 2 are tacked together in their coaxial alignment at the joint surfaces involved. The tack is performed at at least three tack points distributed around the circumference, and preferably at six tack points.

[0021] According to Fig. 2The arc welding device 11 and the laser welding device 12 are directed at approximately the same welding position on the outside of the opposing butt surfaces of the two pipe cross-sections to be joined. However, the two working axes are preferably aligned such that the processing location of the arc welding device 11 leads the location at which the laser beam S simultaneously strikes the pipe outer surface 14, with the lead V preferably being no more than 5 mm, and particularly preferably no more than 3 mm.

[0022] The energy beam S of the laser welding device strikes the outer side 14 of the tube cross-sections at a right angle. The beam direction of the laser beam S is such that the laser beam S is perpendicular to the longitudinal extent of the axle tube 1, and thus according to Fig. 4 meets the longitudinal extension of the pipe outer side 14 at right angles.

[0023] The working axis of the arc welding device 11 forms an angle W with the axis S of the laser energy beam, which is 25° to 30°, and preferably 27°. However, both axes, i.e., the working axis of the arc welding device 11 and the axis S of the laser energy beam, are located in the welding plane 17 defined by the butt surfaces of the pipe ends ( Fig. 4 ). Preferably, the axis S of the laser beam intersects the longitudinal axis L of the axle tube 1 at right angles.

[0024] The arc welding device 11 is designed, for example, to perform a MAG welding process (metal active gas welding) and preferably operates with an electronically controlled pulsed current source. The welding device generates an arc between the preferably nickel-containing welding wire fed from the outside and the outer side 14 of the connecting area 5. The arc welds the butt surfaces at the pipe ends and the fed welding wire, creating the weld seam 20. This process is only approximately 4 mm deep. During the welding process, a wire feeder continuously feeds the welding wire through the welding torch to the welding point. Furthermore, the welding torch supplies the weld seam 20 with the metal active gas involved in the welding process.

[0025] The welding wire should be nickel alloyed, with a nickel content of 1.5% to 5% and preferably 2% to 3% by volume.

[0026] However, the arc welding device 11 can also be configured for other welding processes that consume welding wire.

[0027] The laser welding device 12 is preferably a fiber laser. However, the joining process can also be performed using a diode laser with pulsed diodes. The laser welding device operates with a high-energy-density energy beam focused on a specific focal point. This focal point F is preferably located between the tube outer surface 14 and one-third of the wall thickness D of the axle tube 1. Therefore, the focal point F is preferably located at a location that is closer to the tube outer surface 14 than to the tube inner surface.

[0028] The width of the laser beam initially tapers from the exit of the laser welding device 12 to the focal point F. From the focal point F, the laser beam widens again so that on the opposite inner side of the pipe, energy from the laser beam impinges on a surface A. The melting energy thus available on the opposite inner side of the pipe in zone A is of great importance within the process described here. Fig. 3a shows the situation in the first part of the process. By parallel, i.e. simultaneous operation of both welding devices 11, 12, the weld seam is Fig. 3aalready drawn over a partial circumference, which amounts to approximately one-third of the total circumference. Reference numeral 25 indicates the starting position of the welding process, i.e., the beginning of the weld seam 20 already drawn. Arrow R indicates the direction of rotation of the workpiece, consisting of axle tube 1 and steering knuckle 2, relative to the welding equipment. A zero-gap sensor is used to ensure the accuracy of the process. This sensor guides and positions the welding processes.

[0029] In the radial direction, as the longitudinal section Fig. 4As shown in the upper part, the weld seam 20 is formed continuously. The molten material thus extends from the outside 14 of the pipe to the weld root on the inside. The laser energy supports the formation of the weld seam 20. At the same time, a portion of the laser energy reaches the opposite zone A as secondary energy. This zone is therefore already preheated, which has a positive effect on the microstructure and, in particular, the hardness progression.

[0030] However, the drawing of the weld seam 20 results in material bulging on the inside of the pipe. A weld seam root forms in the form of a burr 21 of molten material, which protrudes significantly into the pipe interior 15 like an irregularly shaped rib.

[0031] The dual welding process is responsible for the formation of weld seam 20. The weld seam is formed using the arc process, but this is supported by the energy introduced via the laser beam (primary energy of the laser beam). This energy leads to a homogenization and improves the structure of the weld seam overall. In particular, it achieves a clean, flat seam surface on the outside of the pipe. Fig. 3b shows a more advanced stage of the process, in which the weld seam 20 already extends over a circumferential segment which is approximately two thirds of the total circumference.

[0032] As soon as the weld seam has been drawn over a circumferential angle of 180°, as in Fig. 3bAs shown below, the burr 21, consisting of molten material from the root, enters the area A covered by the energy of the laser beam S beyond its focal point F, i.e., by the secondary energy of the laser beam. The energy density in zone A is still sufficient to melt and reduce the burr 21 and to even out the zone surrounding the burr, creating a smoothed root 22. The advantage of the thus smoothed weld root 22 is an improvement in the material structure and thus in the quality of this section of the weld.

[0033] Finally, Fig. 3c The situation at the end of the welding process. The weld seam 20 is drawn over 360° to 370° and preferably over a circumferential angle of 365°. This process takes about 15 seconds. Two approximately equal-sized circumferential segments or partial circumferences have been created. The circumferential segment welded later, which is in Fig. 3cThe first welded part shown on the right has the inwardly projecting burr 21 at the weld root. Fig. 3c The circumferential segment shown on the left, however, experienced later smoothing of the burr due to the energy density of the laser beam. The circumferential length welded later extends over a partial circumference of 170° to 180°, and the circumferential length welded first extends over a partial circumference of 180° to 190°.

[0034] The gases generated during gas shielded welding, which could otherwise lead to overpressure, can escape from the interior of the pipe through the previously described vent opening 4. This is then later closed with a closure element.

[0035] In later practical use, the axle body is installed in the vehicle axle, and in particular the commercial vehicle axle, in such a way that the partial circumference with the smoothed weld root 22 is at the bottom, and is thus exposed to the particularly critical tensile loads during driving. Fig. 4 This rotational position of the axle body, which must be ensured during subsequent axle assembly, is shown in longitudinal section.

[0036] For correct axle assembly, the finished axle body can be marked externally with at least one marking that can be clearly assigned to the two circumferential sections or segments, i.e., either the first circumferential section or segment and / or the second circumferential section or segment. The marking should represent "top" or "bottom," either in word or symbol. For this purpose, the marking can be attached to the outside of the axle body or permanently engraved into its material. Alternatively, the end crater remaining after the welding process is completed can serve as the marking. Overall, an axle body is created that can be manufactured relatively quickly and with few production steps. Dual welding only occurs over a total angle of 360° or slightly more than 360°, results in a clean, flat weld surface on the outside of the tube ends, and is performed in a single pass.Nevertheless, two different circumferential sections are created, which differ in the weld root formation on the inside of the connected pipe ends.

[0037] This method allows both steering knuckles 2 to be welded to both axle tube ends simultaneously, provided the welding assembly 10 is present twice. This saves processing time. Alternatively, using only one welding assembly 10, first one steering knuckle 2 is connected to the axle tube 1, followed by the other.

[0038] The described welding process is therefore optimized for the typical dynamic driving loads to which an axle beam is exposed during operation. It takes into account the fact that, during operation, the load conditions prevailing in an axle beam vary between the upper half of the axle beam, where compressive loads predominate, and the lower half, where tensile loads predominate. List of reference symbols 10 Welding arrangement 1 axle tube 11 Arc welding device 2 Steering knuckle 12 Laser welding device 3 Storage space 14 Pipe outside 4 Hole, vent opening 17 Welding level 5 Connection area 20 Weld seam 21 Burr from molten material D Si inner diameter 22 smoothed weld root F Focus point 25 initial welding position L Longitudinal axis of the axle body A Area, zone R Direction of rotation D Wall thickness S laser beam D Ra Outer diameter V Advance DR I inner diameter W Angle between the welding devices Dsa Outer diameter

Claims

1. Method for producing an axle casing of a vehicle axle by integrally connecting an axle tube (1) to a steering knuckle (2) arranged on the longitudinal axis (L) of the axle tube, which steering knuckle is provided with mounting surfaces (3) for mounting a vehicle wheel and has, facing the axle tube (1), a tube cross-section which is substantially equal to the tube cross-section of the axle tube, comprising the steps of: - arranging the axle tube (1) and the steering knuckle (2) so as to have abutting surfaces of the tube cross-sections thereof, which surfaces are positioned coaxially opposite one another, in a workpiece holder of a welding arrangement (10), wherein the welding arrangement (10) also comprises an arc welding device (11) and a laser welding device (12) operated in parallel, - continuously drawing a welded seam (20) in the circumferential direction of the tube cross-sections, wherein the two welding devices (11, 12) are actively directed from the outside onto substantially the same circumferential portion of the abutting surfaces, and wherein the laser beam (S) strikes the outside (14) of the tube at a right angle and preferably intersects the longitudinal axis (L) of the axle tube (1), wherein, during the drawing of the welded seam (20), material is built up on the inside of the tube and a welded seam root in the form of a ridge (21) of molten material is formed, wherein the energy of the laser beam assists the formation of the welded seam (20) and at the same time part of the laser energy reaches an opposite zone A of the inside of the tube as secondary energy, wherein, as soon as the welded seam has been drawn over a circumferential angle of 180°, the energy density in zone A is still sufficient to melt and break down the existing ridge 21 and to homogenize the zone around the ridge, so that the welded seam root, on the inside of the tube, has a ridge of molten material projecting toward the tube interior along a first welded seam portion extending over approximately half the circumference, and a comparatively smoothed seam along the second welded seam portion, - completing the drawing of the welded seam (20) after it has been guided over a circumferential angle of at least 360°.

2. Method according to claim 1, characterized in that the focal point (F) of the laser beam (S) is situated at a location between the outside (14) of the tube and one third of the wall thickness (D) of the axle tube (1).

3. Method according to claim 1 or 2, characterized in that the treatment location of the arc welding device (11) is in advance of the location at which the laser beam (S) areikwa the outside (14) of the tube, wherein the advance (V) is preferably not more than 5 mm.

4. Method according to any of the preceding claims, characterized in that the arc welding is carried out using a welding wire that is alloyed with nickel.

5. Method according to any of claims 1 - 4, characterized in that during the drawing of the welded seam (20), the workpiece holder is rotated about the longitudinal axis (L) of the axle casing.

6. Method according to any of claims 1 - 4, characterized in that during the drawing of the welded seam (20), the two welding devices (11, 12) are moved synchronously on a circular path around the longitudinal axis (L) of the axle casing.

7. Method according to any of the preceding claims, characterized in that a zero gap sensor is used to guide or position the welding processes.

8. Method according to any of the preceding claims, characterized in that the abutting surface of the axle tube (1) is created by sawing the axle tube.

9. Method according to any of the preceding claims, characterized in that, for welding preparation, the axle tube (1) is provided with a vent opening (4) through which opening gases can escape from the tube interior.

10. Method according to any of the preceding claims, characterized in that, for welding preparation, the axle tube (1) and the steering knuckle (2) are temporarily connected and aligned to one another in the region of the abutting surfaces thereof by placing tacking points.

11. Axle casing of a vehicle axle, consisting of an axle tube (1) and a steering knuckle (2) provided with mounting surfaces (3) for mounting the relevant vehicle wheel, which steering knuckle has, facing the axle tube (1), a tube cross-section which is substantially equal to the tube cross-section of the axle tube (1), wherein the two tube cross-sections are placed against one another and are integrally connected to one another by a welded seam (20), wherein the welded seam (20) reaches from the outside of the tube cross-sections to a welded seam root arranged on the inside of the tube cross-sections and extends over the entire circumference of the axle casing with a first welded seam portion extending over approximately half of the circumference and a second welded seam portion extending over the remainder of the circumference, and wherein the welded root, on the inside of the tube, has a ridge (21) of molten material projecting toward the tube interior along the first welded seam portion, and has a comparatively smoothed seam (22) along the second welded seam portion.

12. Axle casing according to claim 11, characterized in that the first welded seam portion extends over a circumferential length of 170° to 180°, and the second welded seam portion extends over a circumferential length of 180° to 190°.

13. Axle casing according to any of claims 11 - 12, characterized in that it is provided with a vent opening (4) for the welding process.

14. Axle casing according to claim 16, characterized in that the vent opening (4) is closed by a closure element.