Method for producing a torsion tube and manufacturing device therefor

Abstract

Method for producing a torsion tube (2, 35) for a roll stabilizer (1) or for a twist beam axle (32), wherein the torsion tube (2, 35) has a first (5) and a second end section (6) and is produced from a hollow cylindrical tube section (9) with a first (10) and a second end region (11), and wherein the two end regions (10, 11) of the tube section (9) are each widened by a mandrel (17) penetrating axially therein, characterized in that the widening of the two end regions (10, 11) of the tube section (17) is carried out with the same mandrel (17), wherein during the penetration of the mandrel (17) the end regions (10, 11) of the tube section (9) are deformed to different degrees over their circumference, and wherein a first circumferential clamping (16) of the tube section (9) from the start of the widening of the first end region (10) is maintained until completion of the expansion of the second end region (11) of the pipe section (9),to ensure identical alignment of the end sections (5, 6) of the torsion tube (2, 35).

Description

[0001] The invention relates to a method for producing a torsion tube and a manufacturing device for producing two widened end sections of a torsion tube according to the preambles of the independent patent claims.

[0002] Roll stabilizers in commercial vehicles counteract the rolling of a vehicle body or a driver's cab, for example, when cornering. Rolling is defined as a rotational movement of the vehicle body or the driver's cab about a longitudinal axis of the commercial vehicle. Roll stabilizers often have a torsion tube extending in the transverse direction of the vehicle and acting as a torsion spring, the end sections of which are flared. Such torsion tubes can also be installed in twist-beam axles. Methods for producing such torsion tubes are generally known. DE 10 2008 046 052 A1 describes such a method, in which a tube section is heated to a temperature between 900 and 1000 °C.000 degrees Celsius and then at least one end region of the pipe section is expanded in a forming tool by axially inserting an upsetting mandrel, wherein the expansion process comprises a first expansion step and a second expansion step with an interruption therebetween and wherein the second expansion step is carried out at a temperature of the end region between 500 and 600 degrees Celsius.

[0003] The object of the invention is to provide a cost-effective method for producing a torsion tube, while also keeping the investment in the necessary production equipment low.

[0004] This object is achieved according to the present invention by a method having the features of independent claim 1 and by a manufacturing device having the features of independent claim 9.

[0005] Preferred embodiments and further developments are the subject of the dependent claims. Further features and details of the invention will become apparent from the description and the drawing figures.

[0006] The invention accordingly provides a method for producing a torsion tube for a roll stabilizer or for a twist-beam axle, wherein the torsion tube has a first and a second end section and is produced from a hollow cylindrical tube section with a first and a second end region. The two end regions of the tube section are each expanded by a mandrel penetrating axially therein. According to the invention, the two end regions of the tube section are expanded using the same mandrel.

[0007] By using only a single mandrel for expanding the two end regions of the tube section, the investment sum for the equipment required for the expansion can be kept low. The torsion tube, manufactured from a hollow cylindrical tube section, is in particular straight and undivided in one piece, i.e. not composed of multiple tube sections. The roll stabilizer is in particular a roll stabilizer for a driver's cab suspension for a commercial vehicle. The driver's cab can, for example, be assigned to a truck, a construction vehicle, or an agricultural vehicle and can be arranged on a substructure of the commercial vehicle in a tiltable or non-tiltable manner. In the context of the present invention, a twist beam axle is understood to be an axle with two trailing arms that are connected by the torsion tube.The mandrel has, at least in some areas, the dimensions of the interior of the two end sections of the torsion tube.

[0008] The end regions of the tube section can be cleaned before expansion to avoid surface defects on the finished end sections of the torsion tube. Cleaning can be done manually with a cleaning cloth or automatically with brushes, for example. The expansion of the two end regions, also known as tufting, preferably takes place at room temperature, i.e., without prior heating, which has a positive effect on the manufacturing costs of the torsion tube. Preferably, the expansion of both end regions of the tube section takes place in a single expansion step, which also has a positive effect on manufacturing costs. Advantageously, the mandrel and / or an inner circumferential surface and / or an outer circumferential surface of the end regions are partially or fully lubricated during the expansion process.Lubrication can be carried out with a suitable grease or oil, although spray lubrication is preferred because it can be easily dosed and applied automatically.

[0009] The hollow cylindrical tube section is hollow cylindrical over its entire longitudinal extent. During the manufacture of the torsion tube, the first and second end regions of the tube section merge into the first and second end sections of the torsion tube. In connection with the manufacturing method underlying the present invention, the end regions of the tube section are referred to as such until they are finally finished, i.e., until they have their final geometry and other properties. When viewed in the longitudinal direction of the tube section, the end regions of the tube section begin at the points where the cross-section of the tube section is no longer circular after the end regions have been expanded.

[0010] During the penetration of the mandrel, the end regions of the pipe section are preferably deformed to varying degrees around their circumference. Such deformation conditions can occur, for example, if the mandrel is non-circular in cross-section along its longitudinal extent, thereby forming the end regions of the pipe section non-circular during the axial penetration of the mandrel. The non-circularity preferably extends consistently in the longitudinal direction of the end regions, so that the end regions experience a longitudinal profiling with a constant cross-section during the expansion. The profiling is preferably designed as a polygonal profiling, for example, a triangular polygonal profiling.Advantageously, the mandrel is tapered so that there is full-circumferential linear contact between its outer circumference and the inner circumference of the pipe section in the area of ​​the end face of the pipe section facing the mandrel, immediately before axial penetration. From this point, the mandrel transitions smoothly and seamlessly into the desired non-circular cross-sectional shape. With a desired triangular-polygonal shape for the end regions of the pipe section, this transition resembles the tapered section of a triangular pencil.

[0011] Advantageously, a first circumferential clamping of the tube section is maintained from the start of the expansion of the first end region until the completion of the expansion of the second end region of the tube section in order to ensure identical alignment of the end sections of the torsion tube. If torsion tubes have non-circular end sections, these must not have any angular offset from one another when viewed from the front of the torsion tube, i.e. they must not be arranged rotated relative to one another. In other words, the non-circular, for example polygonal, end sections would have to be congruent in the circumferential direction of the torsion tube if one were to mentally push them together in the longitudinal direction of the torsion tube. If one wants to expand both end regions of the tube section using the same mandrel, it may seem logical to re-clamp the tube section after expanding the first end region in order to then expand the second end region.However, re-clamping the pipe section after expanding the first end section would entail the risk of the second end section being produced at a skewed angle relative to the first end section. Maintaining the initial circumferential clamping of the pipe section from the beginning of expanding the first end section until the completion of expanding the second end section eliminates this risk.

[0012] After completion of the first end region, the pipe section is expediently pivoted 180 degrees about a rotation axis extending perpendicular to a common longitudinal center axis of the pipe section and the torsion tube. While the pipe section is pivoted 180 degrees, the aforementioned first circumferential clamping of the pipe section remains in place. With this procedure, the end regions of the pipe section to be expanded are preferably fed to the mandrel for processing, which then penetrates axially into the end regions to expand them. Such a system concept is cost-effective because a drive unit can be arranged in a stationary manner for an advancing movement of the mandrel during the expansion of the end regions and for a retracting movement of the mandrel after expansion. A system concept with a mandrel that would have to be fed to each of the two end regions of the pipe section to be expanded would entail considerably higher costs.During axial penetration into the end regions of the tube section, the mandrel moves in the direction of the longitudinal center axis of the tube section. In particular, the longitudinal center axis of the tube section or the torsion tube coincides with a longitudinal center axis of the mandrel. In particular, the axis of rotation runs at least substantially through the center point of the longitudinal center axis of the tube section.

[0013] Preferably, the pipe section is held circumferentially in the immediate vicinity of its end regions during the expansion thereof by a second clamp. The second clamping takes place in a hollow cylindrical region of the pipe section, with this hollow cylindrical region preferably adjacent to the end region of the pipe section to be expanded. In this way, lateral buckling of the pipe section during the expansion of its end regions is prevented. Since the mandrel and the second clamp are arranged relatively close to one another, the forces occurring in both parts of the system during the expansion of the end regions can be favorably supported against each other, for example, via a horizontally arranged C-shaped frame.

[0014] Furthermore, it is preferred if, during the axial penetration of the mandrel into the respective end region of the pipe section, a die enclosing the mandrel and the respective end region moves in advance of the mandrel and at the same time in the same direction as the mandrel. During its movement, the die in particular touches neither the pipe section nor the resulting end region thereof. In this way, the die can be brought in a force-saving manner from the end face of the pipe section facing the mandrel into a position in the region of the transition from the hollow cylindrical region to the end region of the pipe section, which would only be possible with increased expenditure of force after the end region has been expanded. The die in particular moves uniformly at a constant speed of, for example, approximately 2 m / min.

[0015] A further development provides that after the mandrel has penetrated into the respective end region to its final position, the die moves against the axial penetration direction of the mandrel and in the process calibrates the respective end region through tensile-compressive forming. The die moves in particular uniformly, for example at a speed of approximately 2 m / min. In the context of the present invention, calibration is understood to mean that the end regions of the pipe section are brought to a high degree of shape and dimensional accuracy. Tensile-compressive forming in this context is understood to mean forming with simultaneous stress through tensile and compressive loads in different directions. A circumferential annular gap between a die opening and the mandrel is smaller than the wall thickness of the pipe section in its initial state.Therefore, the material of the end section is drawn by the movement of the die against the axial penetration direction of the mandrel towards the end face of the tube section. Since the die inlet is conical, the material of the end section is simultaneously pressed against the now stationary mandrel. Calibration creates an end section with high dimensional accuracy and, at the same time, high surface quality, whereby the material of the end sections of the tube section is simultaneously work hardened by the tensile-compression forming. These effects could not be achieved through pure tensile or compression forming. In a roll stabilizer, the end sections of the torsion tube serve as a comprehensive connection to adjacent components, for example, a lever on each side of the vehicle. In a twist beam axle, the end sections of the torsion tube are connected to the trailing arms in a twist beam axle.Work hardening increases the stability of the end sections of the torsion tube, so that the forces and moments applied by the levers can be safely transferred from one side of the vehicle to the other.

[0016] Furthermore, the pipe section is preferably subjected to end-face finishing, in particular circumferential machining, prior to the production of the end sections. In particular, the end-face finishing comprises facing to produce smooth end faces and at least one chamfering to produce external chamfers, which serve as lead-in bevels for later joining the end sections to the aforementioned levers of the roll stabilizer. In addition, internal chamfers can also be machined in the area of ​​the end faces of the pipe section, for example as lead-in bevels for so-called press plugs. Chamfering and facing at the three aforementioned machining points - end faces, external chamfers, and internal chamfers - can be carried out particularly economically with a single tool and in a single operation, wherein the tool has at least one cutting edge per machining point.By machining the end faces at the beginning of the manufacturing process, the risk of injury during handling during the subsequent manufacturing steps is significantly reduced compared to a pipe section that only has end faces produced by sawing.

[0017] The invention further proposes a manufacturing device for producing two expanded end sections of a torsion tube using a method as described above. The manufacturing device is characterized in that it has a turning device that is linearly displaceable in the direction of the mandrel for pivoting the tube section by 180 degrees about an axis of rotation extending perpendicular to a common longitudinal center axis of the tube section and the torsion tube, and the turning device in turn has a first clamping device for a first circumferential clamping of the tube section. The axis of rotation runs in particular vertically and at least substantially through the center of the longitudinal center axis of the tube section. According to the invention, the two end regions of the tube section are expanded using the same mandrel.The linear displacement of the turning device allows the end section of the tube to be expanded to be fed to the mandrel. The first clamping device ensures the required identical alignment of the end sections of the torsion tube. The first clamping device can be loaded manually or automatically, for example, with a handling robot.

[0018] Preferably, the mandrel is oriented such that, in an effective area involved in the expansion of the end regions of the tube section, it has a cross-sectional area with an axis of symmetry that extends parallel to the axis of rotation. The axis of symmetry thus extends perpendicular to a plane spanned by the longitudinal center axis of the tube section as it rotates about the axis of rotation. The finished end sections of the torsion tube can thereby be pushed onto the mandrel while maintaining the first clamping position. If the previously described axis of symmetry of the mandrel does not extend parallel to the axis of rotation, it is not possible to complete the two end sections of the torsion tube while maintaining the first circumferential clamping of the tube section.

[0019] The invention is explained in more detail below with reference to drawings illustrating only one exemplary embodiment, wherein like reference numerals refer to like, similar, or functionally identical components or elements. In the drawings: Fig. 1 a perspective view of a roll stabilizer for a driver's cab suspension; Fig. 2a in a side view a torsion tube of the roll stabilizer according to Fig. 1; Fig. 2b a sectional view according to the section line B - B from Fig. 2a; Fig. 2c an enlarged detail view of detail X from Fig. 2a; Fig. 3a shows a pipe section in a longitudinal section; Fig. 3b an enlarged detail view of detail Y from Fig. 3a; Fig. 3c a sectional view according to the section line C - C from Fig. 3a; Fig. 4a shows a schematic side view of part of a production facility; Fig. 4b shows an enlarged sectional view of a mandrel according to the section line A - A Fig. 4a; Fig. 5a shows a schematic plan view of a manufacturing facility; Fig. 5b the production facility from Fig. 5a in advanced manufacturing process; Fig. 6a to 6g show schematic plan views of a manufacturing process progressing within a work area; Fig. 7 an enlarged detail view of detail Z from Fig. 6e and Fig. 8 a perspective view of a twist beam axle.

[0020] Fig. 1 shows a roll stabilizer 1 for a driver's cab suspension. The roll stabilizer 1 has a torsion tube 2, to each end of which a lever 3, 4 is connected via a non-circular press connection. The torsion tube has a first 5 and a second polygonal end section 6, which are suitable for receiving press plugs designed as a polygonal profile, also called a constant thickness. Due to their design, the end sections 5, 6 must not have any angular offset from one another when viewed from the front of the torsion tube 2, because in this case the levers 3, 4 would not be aligned with one another, but would be arranged rotated relative to one another. Even a relatively small angular offset would have a relatively strong effect due to the geometric conditions in a driver's cab suspension and render the roll stabilizer unusable.

[0021] In Fig. 2a shows that the two end sections 5, 6 extend perpendicularly to a longitudinal center axis 7 of the torsion tube 2 to different distances. However, with respect to a mirror axis passing through the center point 8 of the longitudinal center axis 7 and extending perpendicularly to the longitudinal center axis 7, the end sections 5, 6 are symmetrical, i.e., without angular offset. Fig. 2b and Fig. As can be seen from Figure 2c, the end sections 5, 6 of the torsion tube 2 are widened compared to the section of the torsion tube 2 arranged between the end sections 5, 6 and have a polygonal cross-section.

[0022] Fig. Figure 3a shows a tube section 9, which represents the starting material for the production of the torsion tube 2, which is why the longitudinal center axis 7 of the tube section 9 is identical to the longitudinal center axis 7 of the torsion tube 2. The same applies to the center point 8. The tube section 9 has a first 10 and a second end region 11 at each end, which become the end sections 5, 6 after the torsion tube 2 has been produced. Fig. As can be seen in Figure 3b, the tube section 9 has an outer chamfer 12 and an inner chamfer 13, as well as a planed end face 14, on each of its end faces, which are produced by circumferential machining in a single operation and with a single tool. These machining operations constitute final end-face machining. The outer chamfer 12, the inner chamfer 13, and the planed end face 14 are not further machined during the production of the torsion tube 2. Fig. Figure 3c shows that the tube section 9 is hollow-cylindrical along its entire length. This design remains unchanged even after the completion of the torsion tube 2 in the section between the two end sections 5, 6.

[0023] Fig. 4a shows part of a manufacturing facility 15 with a first clamping device 16 for a first circumferential clamping of the pipe section 9 from the start of the expansion of the first end region 10 until the completion of the expansion of the second end region 11 of the pipe section 9. The expansion of the two end regions 10, 11 of the pipe section 9 takes place with a single mandrel 17. The manufacturing facility 15 has a turning device 18 that is linearly displaceable in the direction of the mandrel 17 for pivoting the pipe section 9 by 180 degrees. The pivoting of the pipe section 9 takes place after the expansion of the first end region 10 and takes place about a rotation axis 19 extending perpendicular to the common longitudinal center axis 7 of the pipe section 9 and the torsion tube 2. The linear displaceability of the turning device 18 is indicated by a horizontal double arrow shown within the same; the swivel ability is indicated by a corresponding rotation symbol.The first clamping device 16 is fixedly connected to the turning device 18 and is displaced together with it. The longitudinal center axis 7 of the pipe section 9 coincides with a longitudinal center axis 22 of the mandrel 17. The rotation axis 19 runs through the center point 8 of the longitudinal center axis 7 of the pipe section 9, with the rotation axis 19 extending vertically and the longitudinal center axis 7 extending horizontally.

[0024] In Fig. 4b shows that the mandrel 17 is oriented in such a way that, in an effective area 20 involved in the widening of the end areas 10, 11 of the pipe section 9, it has a cross-sectional area with an axis of symmetry 21 that extends parallel to the axis of rotation 19. In Fig. 5a, the production device 15 is shown in full with the first clamping device 16 and the turning device 18. The first clamping device 16 can be loaded with the pipe section 9 manually by a worker 23 or automatically by a handling robot 24. Before inserting the pipe section 9 into the first clamping device 16, the end regions 10, 11 of the pipe section 9 can be cleaned manually or automatically and thus, for example, freed from any chips still present from the final machining of the end faces of the pipe section 9. In Fig. 5b, the turning device 18 with the pipe section 9 clamped in the first clamping device 16 is opposite Fig. 5a is displaced linearly, wherein the first end region 10 of the pipe section 9 is arranged in a working region 25 of a stationary expansion device 26.

[0025] Fig. Figure 6a shows the working area 25 of the indicated expanding device 26 with the first end area 10 of the pipe section 9 arranged therein. The end face of the pipe section 9 is moved linearly against a stop 27 in order to bring the first end area 10 into a defined position. As Fig. As can be seen from Figure 6b, the longitudinal center axis 7 of the pipe section 9 coincides with the longitudinal center axis 22 of the mandrel 17, with both longitudinal center axes 7, 22 extending horizontally. A second clamping device 28 for a second circumferential clamping of the pipe section 9 is closed and encompasses the pipe section 9 adjacent to the first end region 10 in a hollow cylindrical region that will not be formed by the mandrel 17. By means of a schematically illustrated, automated spray lubrication system 29, the mandrel 17, an inner circumferential surface, and an outer circumferential surface of the first end region 10 are wetted with a forming oil.

[0026] Fig. 6c shows the mandrel 17 moving in the penetration direction E toward the first end region 10 of the pipe section 9. The mandrel 17 is designed in the manner of a column with a triangular polygonal cross-section, which is pointed in such a way that there is a full-circumferential line contact between the outer circumference of the mandrel tip and the inner circumference of the pipe section 9. Fig. Figure 6d shows that during an axial penetration of the mandrel 17 in a penetration direction E into the first end region 10 of the tube section 9, a die 30 enclosing the mandrel 17 and the first end region 10 moves in advance of the mandrel 17, also in the penetration direction E. It can be seen that the longitudinal center axis 7 of the tube section 9 and the longitudinal center axis 22 of the mandrel 17 extend in the penetration direction E. In the Fig. At the manufacturing stage shown in Figure 6d, the mandrel 17 has penetrated into the first end region 10 of the pipe section 9 to its final position. At this point, the entire effective area 20 of the mandrel 17 is in contact with the inner peripheral surface of the first end region 10.

[0027] Out of Fig. 6e shows that, as the manufacturing process progresses, after the mandrel 17 has penetrated into the first end region 10 to its final position, the die 30 moves opposite to the axial penetration direction E of the now stationary mandrel 17 and thereby calibrates the first end region 10 by means of a tensile-compression deformation. Fig. 6f, the die 30 has just passed over the first end region 10 of the pipe section 9, thus completely finishing it. The first end region 10 of the pipe section 9 thus becomes, by definition, the first end section 5. In Fig. 6g, the second clamping device 28 is released again, and the mandrel 17 and the die 30 are retracted to their original positions. The pipe section 9 can now be withdrawn from the working area 25 of the expanding device 26 with the aid of the linearly displaceable turning device 18, pivoted 180 degrees, and moved back into the working area 25 with the second end area 11 in order to expand it analogously to the first end area 10.

[0028] Fig. Figure 7 shows the previously described movement of the die 30 with the mandrel 17 stationary in detail. A circumferential annular gap between a die passage 31 and the mandrel 17 is smaller than the wall thickness of the pipe section 9 in the initial state. Therefore, the material of the first end region 10 is drawn by the movement of the die 10 counter to the axial penetration direction E toward the end face of the pipe section 10. Since the die inlet is conical, the material of the first end region 10 is simultaneously pressed against the stationary mandrel 17. Fig. 8 shows a twist beam axle 32 with two longitudinal arms 33, 34 connected by a torsion tube 35. Reference symbol 1 roll stabilizer 2 torsion tube for roll stabilizer 3 levers 4 levers 5 first final section 6 second final section 7 Longitudinal center axis of the pipe section and the torsion tube 8 Center 9 Pipe section 10 first end area 11 second end area 12 External bevel 13 Inner bevel 14 Frontal surface 15 manufacturing facilities 16 first clamping device 17 Thorn 18 Turning device 19 axis of rotation 20 Effective range 21 axis of symmetry 22 Longitudinal central axis of the mandrel 23 workers 24 handling robots 25 Work area 26 Expanding device 27 stop 28 second clamping device 29 Spray lubrication 30 die 31 Die passage 32 Twist beam axle 33 trailing arms 34 trailing arms 35 Torsion tube for twist beam axle E Penetration direction

Claims

[1] Method for producing a torsion tube (2, 35) for a roll stabilizer (1) or for a twist beam axle (32), wherein the torsion tube (2, 35) has a first (5) and a second end section (6) and is produced from a hollow cylindrical tube section (9) with a first (10) and a second end region (11), and wherein the two end regions (10, 11) of the tube section (9) are each widened by a mandrel (17) penetrating axially therein, characterized bythat the widening of the two end regions (10, 11) of the pipe section (17) takes place with the same mandrel (17), wherein during the penetration of the mandrel (17) the end regions (10, 11) of the pipe section (9) are deformed to different degrees over their circumference and wherein a first circumferential clamping (16) of the pipe section (9) is maintained from the start of the widening of the first end region (10) until the end of the widening of the second end region (11) of the pipe section (9) in order to ensure an identical alignment of the end sections (5, 6) of the torsion tube (2, 35). [2] Method according to claim 1, characterized by that the pipe section (9) is pivoted by 180 degrees about a rotation axis (19) extending perpendicular to a common longitudinal center axis (7, 22) of the pipe section (9) and the torsion tube (2, 35) after completion of the first end region (10). [3] Method according to one of the preceding claims, characterized bythat the pipe section (9) is held circumferentially by a second clamping device (22) in the immediate vicinity of its end regions (10, 11) during the expansion of the latter. [4] Method according to one of the preceding claims, characterized by that during the axial penetration of the mandrel (17) into the respective end region (10, 11) of the pipe section (9), a die (30) enclosing the mandrel (17) and the respective end region (10, 11) moves in advance of the mandrel (17) at the same time in the same direction as the mandrel (17). [5] Method according to claim 4, characterized by that the die (30), after the mandrel (17) has penetrated into the respective end region (10, 11) up to its final position, moves counter to the axial penetration direction (E) of the mandrel (17) and in the process calibrates the respective end region (10, 11) by means of a tensile-compression deformation. [6] Method according to one of the preceding claims, characterized bythat the pipe section (9) is subjected to a front-side finishing machining, in particular a circumferential machining finish, before the end sections (5, 6) are produced. [7] Manufacturing device (15) for producing two widened end sections (5, 6) of a torsion tube (2, 35) according to a method according to one of claims 1 to 8, characterized by that the manufacturing device (15) has a turning device (18) which is linearly displaceable in the direction of the mandrel (17) for pivoting the pipe section (9) by 180 degrees about an axis of rotation (19) extending perpendicular to a common longitudinal center axis (7, 22) of the pipe section (9) and the torsion tube (2, 35), and the turning device (18) in turn has a first clamping device (16) for a first circumferential clamping of the pipe section (9). [8] Manufacturing device (15) according to claim 7, characterized bythat the mandrel (17) is aligned such that, in an effective region (20) involved in the widening of the end regions (10, 11) of the pipe section (9), it has a cross-sectional area with an axis of symmetry (21) which extends parallel to the axis of rotation (19).

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