EP3345694B1 - Method and device for locally thickening a hollow body - Google Patents

Description

The invention relates to a method according to the preamble of patent claim 1 for thickening, in particular in sections, a plastically deformable hollow body wall of a hollow body, wherein the hollow body wall runs in an axial direction along a cavity axis of a cavity of the hollow body delimited by the hollow body wall.

The invention also relates to a device according to the preamble of claim 10 for thickening, in particular in sections, a plastically deformable hollow body wall of a hollow body, wherein the hollow body wall runs in an axial direction along a cavity axis of a cavity of the hollow body delimited by the hollow body wall.

The invention further relates to a manufacturing method for producing a hollow body, in the context of which use is made of the above method, and to a machine for producing a hollow body, which has a device of the above type.

The need to thicken a hollow body wall of a hollow body exists, for example, in cases where the hollow body wall must have increased rigidity in at least one partial area and/or in cases where a certain area of the hollow body wall is to be provided with special functional devices, such as a gear or a thread. Hollow bodies of this type are, for example, hollow shafts, such as those used in automotive engineering as drive shafts and, among other things, as side shafts.

State of the art in this field is disclosed in EN 10 2005 050 946 A1 . This publication discloses a method for forming a tube and/or rod element. In the context of the previously known method, a tube element is axially compressed and provided with a flange at the end. For this purpose, the tube element is arranged in a die element which, with a first section of an axially extending die opening, surrounds it with a precise fit. In a second section following the first section, the die opening is radially expanded compared to the first section, forming a recess. During the forming process, the pipe element sits precisely on a mandrel. For forming, the pipe element is subjected to axial pressure using a pressing tool. Due to the pressure from the pressing tool, plasticized material from the pipe element flows into the recess of the die element, forming the end flange. As a result of an axial movement carried out by the die element relative to the pipe element at the same time as the axial pressure is applied to the pipe element, the flange created on the pipe element is extended in the axial direction.

Further state of the art is known from JP-S57-165155-A and JP 2012 045565 A .

JP-S57-165155-A discloses a method and a device for forming a flange onto an axial end of a hollow cylindrical workpiece. The workpiece to be formed sits on a mandrel and is arranged together with the mandrel in a receptacle of an outer mold for processing purposes. The receptacle of the outer mold has an upper axial section of larger diameter and a lower axial section of smaller diameter concentric therewith. The smaller diameter of the receptacle of the outer mold corresponds to the outer diameter of the undeformed workpiece. At the transition between the upper axial section and the lower axial section of the receptacle of the outer mold, an annular shoulder is formed due to the different diameters. To create the flange, with the outer mold stationary in the axial direction, a hollow punch concentric with the mandrel, the inner diameter of which corresponds to the outer diameter of the mandrel and the outer diameter of which corresponds to the diameter of the upper axial section of the receptacle of the outer mold, plunges into the upper axial section of the receptacle on the outer mold and presses the upper end of the workpiece in the axial direction. As a result, material of the workpiece flows into the space formed at the upper axial section of the outer mold holder, forming the flange at the upper end of the workpiece, which in turn is limited by the leading face of the hollow punch, the inner wall the upper axial section of the outer mold holder and the annular shoulder at the transition between the upper axial section and the lower axial section of the outer mold holder.

JP 2012 045565 A relates to a method and a device for thickening an axial end section of a pipe. The pipe to be formed is pushed onto a mandrel and secured there in the axial direction. Four segments of an outer shape are then fed in the radial direction of the pipe from a position far from the pipe to a position close to the pipe. The segments of the outer shape are stepped on their side facing the pipe. Over a partial length running in the axial direction of the pipe at the end of the pipe to be thickened, the segments of the outer shape recede relative to an axial remaining length of the segments in the radial direction of the pipe. At the transition between the receding partial length and the axial remaining length of the segments, a shoulder running in a ring around the pipe is formed. In the position of the segments of the outer shape close to the pipe, the receding partial length of the segments, the outer wall of the pipe and the shoulder at the transition between the receding partial length and the axial remaining length of the segments delimit a hollow cylindrical space concentrically enclosing the pipe. The remaining axial length of the segments rests against the outer wall of the pipe. To thicken the axial end section of the pipe, it is first heated using a heating device housed inside the mandrel. A hollow punch is then moved in the axial direction of the pipe against the end face of the axial end section of the pipe to be thickened. The hollow punch is immersed in the hollow cylindrical space formed on the outside of the pipe between the pipe wall and the segments of the outer mold. Due to the impact of the hollow punch on the pipe, material from the pipe flows into this space, forming the desired thickening of the pipe wall. The outer mold with its segments is stationary in the axial direction of the pipe during the forming process.

Currently in use are also methods and devices by means of which axial sections with different wall thicknesses are produced on hollow shafts by reducing the thickness of the wall of a shaft blank in one axial section, while in another axial section of the shaft blank the original wall thickness is retained. In particular, cold forming processes, such as rotary swaging, can be used.

The object of the present invention, based on the generic prior art, is to provide methods and devices for thickening a plastically deformable hollow body wall of a hollow body, in particular in sections, and for producing a hollow body with a hollow body wall that is thickened in particular in sections, which make it possible to produce thickenings of high quality with variable axial length.

According to the invention, this object is achieved by the methods according to independent patent claims 1 and 8 and by the devices according to independent patent claims 10 and 13.

According to the independent patent claims, material is deliberately accumulated on a hollow body wall. For this purpose, the hollow body in question is arranged with the still unthickened hollow body wall in a receptacle of an outer mold. The receptacle of the outer mold has a receptacle wall that runs in the axial direction on the outside of the hollow body wall arranged in the receptacle. A first partial length of the receptacle wall extends close to the hollow body wall parallel to it and forms an outer support surface for the unthickened hollow body wall. A second partial length of the receptacle wall is offset radially outwards compared to the first partial length of the receptacle wall, expanding the receptacle, and delimits an escape space of the outer mold formed due to the offset. An inner support body is arranged on the inside of the unthickened hollow body wall in such a way that it forms an inner support surface for the hollow body wall with a support body surface running on the inside of the hollow body wall in the axial direction and in particular parallel to the hollow body wall. The inner support body and the inner support surface provided on it are located in the axial direction both at the height of the outer support surface and at the height of the escape space of the outer form. In the resulting mutual arrangement of the hollow body or the hollow body wall on the one hand and the outer form and the inner support body on the other hand, the hollow body is actuated by means of two loading elements at loading points in the axial A compressive force is applied to the loading elements in the axial direction by moving them towards each other in a compression movement.

The loading points on the hollow body are spaced apart from one another in the axial direction and the escape space of the outer shape is arranged between the loading points. Under the effect of the compression movement of the loading elements, material of the hollow body wall between the loading points in the area of the escape space of the outer shape is plasticized and plasticized material of the hollow body wall flows into the escape space of the outer shape, thickening the hollow body wall. A continuous compression movement is generated by appropriately controlling the motor drive of the loading elements. A continuous compression movement is associated with a continuous flow of material into the escape space of the outer shape. At the same time, the inner support body preferably ensures that the cross-section of the cavity delimited by the hollow body wall remains essentially unchanged, in particular at the level of the escape space of the outer shape.

The hollow body is acted upon in the axial direction by an actuating element which protrudes radially outward from the outside of the hollow body wall and limits the escape space of the outer shape in the axial direction. As a result, the axial extent of the escape space can be increased.

According to the invention, it is provided for this purpose that, in addition to the continuous compression movement of the loading elements, an axial relative movement of the loading elements carrying out the continuous compression movement on the one hand and the outer shape on the other hand is carried out in the axial direction by superimposing a movement carried out by the outer shape in the axial direction on the continuous compression movement of the loading elements carrying out the continuous compression movement. The axial extent of the thickening produced on the hollow body wall can be defined by the amount of the axial relative movement of the loading elements and the outer shape. Material of the hollow body wall flows into the escape space of the outer mold, which is constantly increasing due to the axial relative movement of the loading elements carrying out the continuous compression movement on the one hand and the outer mold on the other hand, where the thickening of the hollow body wall can consequently build up continuously over the desired axial length.

According to the invention, the compression movement of the loading elements is force-controlled.

The basis for the force control of the compression movement is the amount of the forming force that is introduced into the hollow body wall to be formed by means of the loading elements. When a limit value of the forming force is reached, which indicates that the escape space of the outer shape is completely filled with plasticized material of the hollow body wall, an increase in the escape space is initiated, thereby creating the conditions for further plasticized wall material to flow into the escape space. The limit value of the forming force in the force control of the forming process can be determined empirically.

The axial relative movement of the loading elements and the outer mold is carried out by means of a controlled motor drive.

The method according to the invention can be designed in particular as a cold forming method. Hollow bodies made of any plastically deformable materials are formed, in particular hollow bodies which have at least walls made of plastically deformable metal.

A mandrel, for example, can be used as an internal support body, and stamps can be used as the loading elements. A controllable hydraulic drive can be used as the motor drive to generate the compression movement of the loading elements. However, other controllable drive types are also conceivable.

Preferably, the motor drive of the loading elements comprises two drive units, each of which is assigned to one of the loading elements and which are controlled in a coordinated manner, for example, by means of a numerical control system. The numerical control system for the loading elements can be integrated into a higher-level device or tool control system or into a higher-level machine control system.

The hollow body to be formed is preferably open in the axial direction at at least one end. Depending on the position which the escape space of the outer mold assumes in the axial direction relative to the hollow body wall to be thickened, different axial sections of the hollow body wall can be thickened in the manner described.

Particular embodiments of the methods and devices according to the independent patent claims arise from the dependent patent claims 2 to 7, 9, 11 and 12.

According to claim 2, according to the invention, various possibilities for generating the compression movement of the loading elements are used in a complementary or alternative manner. In detail, it is provided that by appropriate control of the motor drive of the loading elements, one of the loading elements is moved in the direction of the other loading element that is stationary in the axial direction and/or that both loading elements are moved simultaneously and in opposite directions in the axial direction and/or that both loading elements are moved simultaneously and in the same direction and at different speeds in the axial direction. In any case, the distance between the loading elements in the axial direction is reduced and the hollow body wall is subjected to pressure and plasticized in an area arranged between the loading points. The plasticized material of the hollow body wall is prevented from escaping into the interior of the cavity by the inner support body and consequently flows into the escape space of the outer mold arranged on the outside of the hollow body wall, thickening the hollow body wall.

In principle, it is possible to provide the hollow body with opposing According to the invention, according to claim 3, pressure is preferably applied to the hollow body on at least one of the end radial faces of the hollow body, in particular the hollow body wall, which are easily accessible for the forming device.

In the interest of a construction of the device according to the invention for thickening the hollow body wall that is as compact as possible, it is provided that the hollow body is subjected to a compressive force in the axial direction by an application element formed integrally with the inner support body (patent claim 4).

If one of the loading elements is designed as a hollow organ and is provided with an organ cavity running in the axial direction, the inner support body can run into the organ cavity of the loading element in question during the compression movement of the loading elements. If the cross section of the organ cavity and the cross section of the inner support body are coordinated with one another and the loading element that interacts with the hollow organ is designed as one piece with the inner support body, the two loading elements are guided relative to one another in the axial direction during the compression movement by the inner support body accommodated in the organ cavity (patent claim 5).

After completion of the forming of the hollow body wall, in a preferred embodiment of the invention, the thickened hollow body wall or the hollow body and the outer shape are separated from one another by a relative movement carried out by the thickened hollow body wall or the hollow body and the outer shape in the axial direction (patent claim 6).

In addition or as an alternative, the invention provides that the thickened hollow body wall or the hollow body is removed from the outer mold by moving outer mold parts formed by dividing the outer mold in the axial direction relative to one another in the radial direction while opening the outer mold (claim 7). The latter procedure is chosen in particular when the geometry of the formed Hollow body does not allow removal of the hollow body from the outer mold solely by movement in the axial direction.

For cases of the latter type, the device according to the invention has the outer mold divided in the axial direction. The outer mold parts formed by the division of the outer mold can be moved relative to one another in the radial direction, preferably by means of a controllable motor drive (claim 11). The outer mold can be opened or closed as desired by relative movements of the outer mold parts in the radial direction. In a further preferred embodiment of the device according to the invention, as shown in claim 12, a first axial outer mold part formed by dividing the outer mold in the radial direction is divided in the axial direction into outer mold parts which can be moved relative to one another in the radial direction, preferably by means of a controllable motor drive. The first axial outer mold part has the first, cross-sectionally reduced partial length of the receptacle for the hollow body wall provided on the outer mold. In addition to the first axial outer mold part, a second axial outer mold part results due to the radial division of the outer mold. The second axial outer mold part is formed in one piece and provided with the escape space of the outer mold, wherein the escape space on the second axial outer mold part opens out to the first axial outer mold part and the wall of the escape space runs in the axial direction such that the second axial outer mold part and the thickening of the hollow body wall formed in the escape space are movable relative to one another in the axial direction while the thickening of the hollow body wall emerges from the second axial outer mold part. The two axial outer mold parts are adjacent to one another in the axial direction. Inside the two axial outer mold parts, the first partial length of the receiving wall and the escape space complement each other to form the entire receiving space provided for the hollow body wall or the hollow body. Due to its one-piece design, the second axial outer mold part is free of parting lines. This circumstance is advantageous in that when thickening a hollow body wall, due to the lack of parting lines, no parting lines are undesirably formed on the thickening of the hollow body wall created in the escape space of the outer mold. Since the receptacle of the outer mold intended for receiving the hollow body wall on the second If only the escape space is provided for the axial outer mold part, i.e. that part of the receptacle which is not reduced in cross-section compared to a thickening of the hollow body wall created in the escape space of the outer mold, the formed hollow body can be removed from the second axial outer mold part by a movement in the axial direction.

Figuren 1A bis 4B

den Ablauf eines nicht erfindungsgemäßen Verfahrens zum abschnittweisen Verdicken einer Wand einer Hohlwelle und

Figuren 5A bis 8B

den Ablauf einer ersten Variante eines erfindungsgemäßen Verfahrens zum abschnittweisen Verdicken der Wand einer Hohlwelle.

The invention is explained in more detail below using exemplary schematic representations. They show:

Figures 1A to 4B

the sequence of a method not according to the invention for sectionally thickening a wall of a hollow shaft and

Figures 5A to 8B

the sequence of a first variant of a method according to the invention for section-wise thickening of the wall of a hollow shaft.

According to Figure 1A a machine shown in outline and designed as a forming machine 1 has a first tool holder 2 and a second tool holder 3. A punch 4 is fixed in the first tool holder 2, the second tool holder 3 holds a processing unit 5, which in turn consists of a pressure piece 6 and a mandrel 7 formed in one piece with the pressure piece 6 and having a reduced cross-section compared to the pressure piece 6. The mandrel 7, like the pressure piece 6, has a circular cross-section. Due to the reduced cross-section of the mandrel 7 compared to the pressure piece 6, the pressure piece 6 forms a circumferential shoulder 8.

The stamp 4 and the pressure piece 6 of the processing unit 5 form loading elements, whereby the stamp 4 is designed as a hollow element and has a stamp cavity 9 as the cavity of the element. The stamp cavity 9 has a circular cross-section, just like the mandrel 7. The cross-sectional size of the stamp cavity 9 minimally exceeds the cross-sectional size of the mandrel 7.

By means of a motor drive unit 10, the stamp 4 can be moved along a movement axis 11. In a corresponding manner, a motor drive unit 12 serves to move the processing unit 5 along the movement axis 11. Both the motor drive unit 10 and In the example shown, the motor drive unit 12 is a hydraulic drive of conventional design. Together, the motor drive units 10, 12 form a motor drive 13 for the punch 4 and the processing unit 5 and thus for the pressure piece 6 and the mandrel 7. A programmable numerical control 14 of the motor drive 13 or the motor drive units 10, 12 is in Figure 1A shown in a suggestive manner.

Together with a reinforcement 15 provided as an outer form, the punch 4 and the processing unit 5 form a forming tool 16. The forming tool 16 is in all of the Figures 1A to 8B shown, while the remaining parts of the forming machine 1 are shown for the sake of simplicity only in Figure 1A are shown.

The reinforcement 15 has a receptacle 17 with a receptacle wall 18. The receptacle wall 18 runs parallel to the movement axis 11 of the punch 4 and the processing unit 5 and comprises a first partial length 19 and a second partial length 20 which adjoins the first partial length 19 along the movement axis 11 and is offset radially outwards relative to the first partial length 19, expanding the receptacle 17. The second partial length 20 of the receptacle wall 18 delimits an escape space 21 of the reinforcement 15. The relevant drawing detail "A" of Figure 1A is in Figure 1B shown enlarged.

The forming tool 16 serves as a device for section-by-section thickening of a plastically deformable hollow body wall of a hollow body, in the example case shown for section-by-section thickening of a wall 22 of a hollow shaft 23 consisting of plastically deformable steel. The wall 22 delimits a hollow space of the hollow shaft 23 that is circular in cross-section. The movement axis 11 coincides with the cavity axis of the cavity and defines an axial direction with its course.

The Figures 1A to 4B illustrate the sequence of a method which can be implemented by means of the forming machine 1 or by means of the forming tool 16 and is not according to the invention for section-wise thickening of the wall 22 of the Hollow shaft 23. Modified methods compared to these methods are based on the Figures 5A to 8B explained. The different process stages are each shown with an overall view of the forming tool 16 as well as with an enlarged drawing detail "A". The numbering of the overall views has the suffix A, the numbering of the enlarged drawing details has the suffix B.

In the case of the procedural variants according to the Figures 1A to 4B and 5A to 8B First, the hollow shaft 23, which is in the undeformed state, is pushed from the side of the punch 4 in the axial direction (along the movement axis 11) into the holder 17 of the reinforcement 15 and thereby onto the mandrel 7 of the processing unit 5, which is already arranged inside the holder 17. At this point, the punch 4 is set back in the axial direction relative to the reinforcement 15. The processing unit 5 takes up the Figures 1A , 5A Enter the position shown.

In the example shown, the wall 22 of the hollow shaft 23 has a circular cross-section. The outer diameter of the wall 22 corresponds to the diameter of the holder 17 on the reinforcement 15 and matches the diameter of the pressure piece 6 of the processing unit 5. The inner diameter of the wall 22 corresponds to the diameter of the mandrel 7 of the processing unit 5. The hollow shaft 23 pushed into the holder 17 of the reinforcement 15 therefore sits on the mandrel 7 without play in the radial direction. On the outside, the wall 22 of the hollow shaft 23 is closely adjacent to the holder wall 18 of the holder 17. In the axial direction, the hollow shaft 23 rests with a radial end face 24 of the wall 22 on the shoulder 8 of the pressure piece 6 which runs around the movement axis 11.

Based on these conditions, the punch 4 is advanced in the axial direction towards the hollow shaft 23 by means of the motor drive 13 or the motor drive unit 10 until a radial end face 25 of the punch 4 comes to rest on a radial end face 26 of the wall 22 of the hollow shaft 23 and the hollow shaft 23 is consequently moved with a small amount of force between the pressure piece 6 or the shoulder 8 of the processing unit 5 on the one hand and the punch 4 on the other hand in the axial direction. When the punch 4 moves, the mandrel 7 runs with its end remote from the pressure piece 6 in the axial direction into the punch cavity 9.

The feed movement of the punch 4 carried out by means of the motor drive 13 or the motor drive unit 10 can be both path-controlled and force-controlled by the numerical control 14. In the case of a path-dependent control, the punch 4 is moved from its starting position over a defined path length in the axial direction. In a force-dependent control, the increase in force in the drive train of the punch 4, which occurs when the punch 4 runs with the radial end face 25 onto the radial end face 26 of the wall 22 of the hollow shaft 23, marks the end of the feed movement.

The described delivery movement of the stamp 4 is also carried out within the framework of the procedure according to the Figures 1A to 4B and in the context of the procedure under the Figures 5A to 8B The conditions resulting at the end of the feed movement of the punch 4 are shown in the Figures 1A, 1B and in the Figures 5A, 5B The subsequent procedures are different from each other.

In the context of the non-inventive method according to the Figures 1A to 4B is based on the conditions according to the Figures 1A, 1B a compression movement is carried out in the axial direction by the punch 4 and the pressure piece 6, in that the pressure piece 6 is moved in the axial direction towards the punch 4, which is stationary in the axial direction. Due to the compression movement, material of the wall 22 of the hollow shaft 23 is plasticized between the impact points on the wall 22, i.e. between the radial end faces 24, 26 of the wall 22, and plasticized material of the wall 22 flows into the escape space 21 of the reinforcement 15 arranged between the impact points or the radial end faces 24, 26 of the wall 22. Any other material flow is prevented on the inside of the wall 22 by the mandrel 7, which acts as an inner support body for the wall 22 of the hollow shaft 23 and which, with its axially parallel lateral surface, forms a support body surface or a forms an inner support surface for the wall 22 and uses this surface to support the wall 22 of the hollow shaft 23 in the radial direction. The first partial length 19 of the receiving wall 18 acts accordingly on the outside of the wall 22. The first partial length 19 of the receiving wall 18 forms an outer support surface for the wall 22 running parallel to the wall 22 and accordingly also supports the wall 22 of the hollow shaft 23 in the radial direction.

The compression movement, i.e. the movement carried out by the pressure piece 6 relative to the stationary punch 4 of the forming tool 16 in the axial direction, ends as soon as the escape space 21 of the reinforcement 15 is filled with plasticized material of the wall 22, forming a thickening 27 of the wall 22, and thus the process stage according to the Figures 2A, 2B is reached.

Both a path control and a force control are also conceivable for the described compression movement of the punch 4 and the pressure piece 6. For path control, a travel length of the pressure piece 6, determined empirically for example, must be stored in the numerical control 14 of the motor drive 13. As soon as the pressure piece 6 has moved in the axial direction over the specified path length, the motor drive unit 12 used to move the pressure piece 6 is stopped.

In the case of a force control of the compression movement, the motor drive unit 12 for the pressure piece 6 is switched off as soon as the increase in the motor drive force is detected by means of a corresponding sensor on the motor drive unit 12, which occurs when the escape space 21 of the reinforcement 15 is filled with plasticized material of the wall 22 and a further advance of the hollow shaft 23 in the axial direction is consequently blocked.

Starting from the stage of the procedure according to the Figures 2A, 2B the punch 4 is moved back in the axial direction relative to the radial end face 26 of the wall 22 of the hollow shaft 23 by means of the motor drive unit 10 by the distance over which the thickening 27 of the wall 22 is to be extended in the axial direction in the subsequent forming process.

Once the punch 4 has reached its target position in the axial direction, the motor drive unit 10 is stopped and a new compression movement of the type described above is carried out by means of the motor drive unit 12. In this case, the pressure piece 6 is again moved away or force-controlled in the axial direction relative to the punch 4, which is stationary in this direction, by means of the motor drive unit 12, until the escape space 21 of the reinforcement 15, which has been enlarged due to the previous retraction movement of the punch 4, is again completely filled with plasticized material of the wall 22 of the hollow shaft 23 and the conditions are thus in accordance with the Figures 3A, 3B have resulted.

The process described is repeated until the thickening 27 produced on the wall 22 of the hollow shaft 23 has the desired length in the axial direction. During the entire intermittently executed upsetting movement, the pressure piece 6 is guided in the axial direction over the mandrel 7 inside the punch cavity 9. In the example shown, a thickening 27 is built up in the escape space 21 of the reinforcement 15 on the wall 22 of the hollow shaft 23, which runs in a wave-like manner on the outside in the axial direction. With each of the upsetting strokes of the upsetting movement carried out by the punch 4 and the pressure piece 6, one of the axial wave sections of the thickening 27 is produced. By post-processing the thickening 27 following the forming process, the wave shape can be leveled if necessary.

Based on the Figures 4A, 4B illustrated conditions at the end of the forming process, the punch 4 is moved in the axial direction relative to the reinforcement 15 at rapid traverse to the starting position that it had assumed before the beginning of the forming process. At the same time or after the movement of the punch 4, the processing unit 5 is advanced in the axial direction together with the hollow shaft 23 sitting on the mandrel 7 by actuating the motor drive unit 12 until the hollow shaft 23 is arranged at least partially outside the reinforcement 15 and is thus accessible for removal from the forming tool 16.

The removal of the formed hollow shaft 23 can also be carried out mechanically. For this purpose, clamping shells 28, 29 can be used, as shown in Figure 4A are shown very schematically. By means of a corresponding numerically controlled drive, the clamping shells 28, 29 can be moved in the radial direction of the formed hollow shaft 23 in the direction of Figure 4a shown double arrows.

If the formed hollow shaft 23 is pushed sufficiently far out of the reinforcement 15 in the axial direction by means of the motor drive unit 12, the clamping shells 28, 29 are moved against each other in the radial direction of the hollow shaft 23 until they clamp the hollow shaft 23 behind the thickening 27. Now, by actuating the motor drive unit 12, the processing unit 5 is moved back in the axial direction and the mandrel 7 is thereby pulled out of the interior of the hollow shaft 23. Once the mandrel 7 has left the cavity of the hollow shaft 23, the formed hollow shaft 23 can be removed from the forming machine 1 by means of the clamping shells 28, 29. For this purpose, the clamping shells 28, 29 can be movable and/or pivotable in the axial direction. With a corresponding movement of the clamping shells 28, 29 in the opposite direction, a still undeformed hollow shaft can then be inserted into the forming machine 1 or the forming tool 16 to initiate a further forming process of the type described above.

In the context of the inventive method according to the Figures 5A to 8B is based on the conditions according to the Figures 5A, 5B First, a compression movement is carried out by moving the pressure piece 6 in the axial direction relative to the stamp 4, which is stationary in the axial direction, by means of the motor drive unit 12. If, as a result of the relative movement of the pressure piece 6 and the stamp 4, the escape space 21 of the reinforcement 15 has filled with plasticized material from the wall 22 of the hollow shaft 23, forming the thickening 27, the motor drive unit 12 is not stopped and the stamp 4 is retracted relative to the radial end face 26 of the wall 22 of the hollow shaft 23.

Instead, as soon as the escape space 21 of the reinforcement 15 is first filled with plasticized material of the wall 22 and accordingly the process stage according to the Figures 6A, 6B is reached, a movement of the punch 4 in the axial direction is initiated in addition to the movement of the pressure piece 6 already in progress. The additional movement of the punch 4 is triggered in a force-controlled manner as soon as the escape space 21 of the reinforcement 15 is filled with plasticized material of the wall 22 and consequently an increase in the forming force applied by means of the motor drive unit 12 is recorded.

The joint movement of the punch 4 and the pressure piece 6 follows seamlessly on from the first movement phase, in which only the pressure piece 6 is moved in the axial direction.

In the phase of the compression movement in which the punch 4 and the pressure piece 6 move together in the axial direction, the punch 4 and the pressure piece 6 move in the same direction, but the pressure piece 6 moves at a higher speed than the punch 4. As a result of the speed difference, a compressive force is exerted on the wall 22 of the hollow shaft 23 in the axial direction by means of the punch 4 and the pressure piece 6, as a result of which the material of the wall 22 is plasticized. Since the punch 4 and the pressure piece 6 move together in the axial direction and since this movement is carried out relative to the reinforcement 15, the escape space 21 of the reinforcement 15 delimited by the punch 4 increases in the course of the compression movement. The extent of the escape space 21 increases in the axial direction. Plasticized material of the wall 22 flows continuously into the escape space 21. In this way, the thickening 27 is created over the desired axial length at the relevant axial end of the wall 22 of the hollow shaft 23. The wall 22 is supported in the radial direction on its inside by the mandrel 7 and on its outside by the first partial length 19 of the receiving wall 18.

Deviating from the invention, the joint movement of the punch 4 and the pressure piece 5 is carried out relative to the reinforcement 15 which is stationary in the axial direction.

The relative movement of the punch 4 and the pressure piece 6, which is carried out as a continuous compression movement, as well as the relative movement carried out simultaneously with the compression movement between the punch 4 and the pressure piece 6 on the one hand and the reinforcement 15, which is stationary in the axial direction, on the other hand, are controlled in such a way that the escape space 21 of the reinforcement 15, which lengthens in the axial direction during the forming process, is permanently completely filled with plasticized material of the wall 22. As a result, the thickening 27 is created over its entire axial length with an axially parallel outer surface that is flat in the axial direction and exactly reproduces the wall of the escape space 21.

In the Figures 7A, 7B the thickening 27 on the wall 22 of the hollow body 23 is smaller than the ratios according to the Figures 6A, 6B extended in the axial direction, but the final length of the thickening 27 is not yet reached. With its final axial length, the thickening 27 is at the relevant axial end of the wall 22 of the hollow shaft 23 in the Figures 8A, 8B shown.

Upon reaching the stage of the procedure according to the Figures 8A, 8B the speed of the punch 4 is increased by appropriate control of the motor drive unit 10 such that the speed of the punch 4 exceeds the speed of the pressure piece 6. As a result, the punch 4 lifts off the radial face 25 of the radial face 26 of the wall 22 and moves in rapid traverse to its starting position, which is away from the reinforcement 15 in the axial direction. At the same time, the formed hollow shaft 23 is pushed out of the reinforcement 15 by the processing unit 5, which continues its movement in the axial direction unchanged. The hollow shaft 23 arranged outside the reinforcement 15 can be moved in the manner described above by means of the Figures 8A, 8B clamping shells 28, 29 (not shown) and removed from the forming tool 16 or from the forming machine 1. A hollow shaft 23 to be machined can then be fed to the forming tool 16 by means of the clamping shells 28, 29.

According to the invention, the compression movement carried out by the punch 4 and the pressure piece 6 is offset by the reinforcement 15 in the axial direction relative to to the punch 4 and the pressure piece 6 is superimposed. With appropriate control of the axial movement of the reinforcement 15, the extent of the escape space 21 on the reinforcement 15 increases in the axial direction and the thickening 27 on the wall 22 of the hollow shaft 23, which builds up in the escape space 21 due to the compression movement of the punch 4 and the pressure piece 6, can lengthen in the axial direction.

The formed hollow shaft 23 can be subjected to post-processing as part of a manufacturing process. In particular, it is conceivable that special functional devices, such as a thread or gear teeth, are created on the thickening 27 of the wall 22 of the hollow shaft 23.

Claims (13)

1. Method for thickening, in particular in sections, a plastically deformable hollow member wall (22) of a hollow member (23), wherein the hollow member wall (22) extends in an axial direction along a hollow space axis of a hollow space, which is delimited by the hollow member wall (22), of the hollow member (23),

   • wherein the hollow member (23) is arranged with the non-thickened hollow member wall (22) in a receiving member (17), which is provided with a receiving member wall (18), of an outer mould (15, 31) in such a manner that the receiving member wall (18) extends at the outer side of the hollow member wall (22) in the axial direction and with a first part-length (19) which extends in the axial direction forms an outer support face which extends parallel with the hollow member wall (22) for the non-thickened hollow member wall (22) and with a second part-length (20) which extends in the axial direction delimits an evasion space (21) of the outer mould (15, 31), wherein the second part-length (20) of the receiving member wall (18) with the evasion space (21) being formed is offset in a radially outward direction with respect to the first part-length (19) of the receiving member wall (18) with the receiving space (17) being expanded,

   • wherein at the inner side of the non-thickened hollow member wall (22) an inner support member (7) is arranged in such a manner that the inner support member (7) forms with a support member face which extends in the axial direction at the inner side of the hollow member wall (22) an inner support face for the hollow member wall (22), wherein the inner support face of the inner support member (7) is arranged in the axial direction at the level of the outer support face and also at the level of the evasion space (21) of the outer mould (15, 31),

   • wherein, with an active radial support of the non-thickened hollow member wall (22) on the outer support face of the outer mould (15, 31) and with an active radial support of the hollow member wall (22) on the inner support face of the inner support member (7), the hollow member (23) is acted on by means of two application members (4, 6) at application locations with a pressure force in each case in the axial direction by the application members (4, 6) being moved towards each other in the axial direction with a continuous compression movement, wherein the application locations are spaced apart from each other on the hollow member (23) in the axial direction, wherein the evasion space (21) of the outer mould (15, 31) is arranged between the application locations and wherein an application member (4, 6) protrudes radially outwards with respect to the outer side of the hollow member wall (22) and delimits the evasion space (21) of the outer mould (15, 31) in the axial direction, and

   • wherein, as a result of the compression movement of the application members (4, 6), material of the hollow member wall (22) is plasticised between the application members in the region of the evasion space (21) of the outer mould (15, 31) and plasticised material of the hollow member wall (22) flows into the evasion space (21) of the outer mould (15, 31) with the hollow member wall (22) being thickened, and

   • wherein, in addition to the continuous compression movement of the application members (4, 6), an axial relative movement of the application members (4, 6) which carry out the continuous compression movement, on the one hand, and the outer mould (15, 31), on the other hand, is carried out in the axial direction by a movement which is carried out by the outer mould (15, 31) in the axial direction being superimposed on the continuous compression movement of the application members (4, 6) which carry out the continuous compression movement, wherein, as a result of the axial relative movement of the application members (4, 6) which carry out the continuous compression movement, on the one hand, and the outer mould (15, 31), on the other hand, the extent of the evasion space (21) of the outer mould (15, 31) in the axial direction increases,

   characterised in that

   • the compression movement of the application members (4, 6) is force-controlled, and

   • in that an increase of the extent of the evasion space (21) of the outer mould (15, 31) in the axial direction is introduced as soon as the value of a forming force which is introduced by the application members (4, 6) into the hollow member wall (22) which is intended to be formed reaches a limit value which indicates a complete filling of the evasion space (21) of the outer mould (15, 31) with plasticised material of the hollow member wall (22) .
2. Method according to claim, 1 characterised in that the application members (4, 6) are moved towards each other with the compression movement in the axial direction,

   • by one of the application members (4, 6) being moved in the direction towards the other application member (4, 6) which is stationary in the axial direction or

   • by the two application members (4, 6) being moved at the same time and in opposite directions in the axial direction or

   • by the two application members (4, 6) being moved at the same time and in the same direction and at different speeds in the axial direction.
3. Method according to either one of the preceding claims, characterised in that the hollow member (23) is acted on with a pressure force in the axial direction by means of at least one of the application members (4, 6) at an application location on a radial end face (24, 26) of the hollow member (23) .
4. Method according to any one of the preceding claims, characterised in that the hollow member (23) is acted on with a pressure force in the axial direction by means of an application member (6) which is formed integrally with the inner support member (7).
5. Method according to any one of the preceding claims, characterised in that the hollow member (23) is acted on with a pressure force in the axial direction by means of an application member (4) which is in the form of a hollow member and which is provided with a member hollow space (9) which extends in the axial direction and which is open at least with respect to the inner support member (7) and which is constructed to receive the inner support member (7).
6. Method according to any one of the preceding claims, characterised in that the thickened hollow member wall (22) is removed from the outer mould (15, 31) by means of a relative movement which is carried out by the thickened hollow member wall (22) and the outer mould (15, 31) in the axial direction.
7. Method according to any one of the preceding claims, characterised in that the thickened hollow member wall (22) is removed from the outer mould (31) in that, by outer mould portions (34, 35), formed by dividing the outer mould (31)in the axial direction, are moved relative to each other in the radial direction with the outer mould (31) being opened thereby.
8. Production method for producing a hollow member (23) having a hollow member wall (22) which delimits a hollow space and which extends along a hollow space axis of the hollow space in an axial direction, in particular for producing a steering shaft which is in the form of a hollow shaft, characterised in that the hollow member wall (22) is in particular partially thickened using the method according to any one of the preceding claims and is thereby provided over a length which extends in the axial direction with a thickened portion (27).
9. Production method according to claim 8, characterised in that the thickened portion (27) of the hollow member wall (22) is provided with at least one functional device, for example, with a tooth arrangement and/or with a thread.
10. Apparatus for thickening, in particular in sections, a plastically deformable hollow member wall (22) of a hollow member (23), wherein the hollow member wall (22) extends along a hollow space axis of a hollow space, which is delimited by the hollow member wall (22), of the hollow member (23) in an axial direction, wherein the apparatus comprises:

    • an outer mould (15, 31) having a receiving member (17) which is provided for the hollow member wall (22) and which has a receiving member wall (18) which is associated with the outer side of the hollow member wall (22) and which forms with a first part-length (19) which extends in the axial direction an outer support face for the non-thickened hollow member wall (22) and with a second part-length (20) which extends in the axial direction an evasion space (21) of the outer mould (15, 31), wherein the second part-length (20) of the receiving member wall (18) with the evasion space (21) being formed is offset in a radially outward direction with respect to the first part-length (19) of the receiving member wall (18) with the receiving space (17) being expanded,

    • an inner support member (7) which is associated with the inner side of the hollow member wall (22) and which forms with a support member face which is associated with the inner side of the hollow member wall (22) and which extends in the axial direction an inner support face for the hollow member wall (22), wherein the inner support face of the inner support member (7) can be arranged in the axial direction at the level of the outer support face and also at the level of the evasion space (21) of the outer mould (15, 31),

    • two application members (4, 6) and a controllable motorised drive (13) for the application members (4, 6), wherein the hollow member (23) with an active radial support of the non-thickened hollow member wall (22) on the outer support face of the outer mould (15, 16) and with active radial support of the hollow member wall (22) on the inner support face of the inner support member (7) can be acted on by means of the application members (4, 6)with a pressure force in each case in the axial direction at application locations by the application members (4, 6) being able to be moved towards each other in the axial direction by means of the motorised drive (13) with a continuous compression movement, wherein the application locations on the hollow member (23) are spaced apart from each other in the axial direction, wherein the evasion space (21) of the outer mould (15, 31) is arranged between the application locations, wherein an application member (4, 6) protrudes radially outwards with respect to the outer side of the hollow member wall (22) and delimits the evasion space (21) of the outer mould (15, 31) in the axial direction and wherein, as a result of the compression movement of the application members (4, 6), material of the hollow member wall (22) can be plasticised between the application locations in the region of the evasion space (21) of the outer mould (15, 31) and plasticised material of the hollow member wall (22) flows into the evasion space (21) of the outer mould (15, 31) with the hollow member wall (22) being thickened, and

    • wherein there is provided a controlled motorised drive which produces an axial relative movement, which is carried out in the axial direction in addition to the continuous compression movement of the application members (4, 6), of the application members (4, 6) which carry out the continuous compression movement, on the one hand, and the outer mould (15, 31), on the other hand, by the controlled motorised drive superimposing a movement which is carried out by the outer mould (15, 31) in the axial direction on the continuous compression movement of the application members (4, 6) which carry out the continuous compression movement, wherein, as a result of the axial relative movement of the application members (4, 6) which carry out the continuous compression movement, on the one hand, and the outer mould (15, 31), on the other hand, the extent of the evasion space (21) of the outer mould (15, 31) in the axal direction increases,

    characterised in that

    • the application members (4, 6) can be moved towards each other by means of the motorised drive (13) with a force-controlled continuous compression movement in the axial direction, and

    • in that by means of the motorised drive which is provided to produce the axial relative movement of the application members (4, 6) which carry out the continuous compression movement, on the one hand, and the outer mould (15, 31), on the other hand, an increase of the extent of the evasion space (21) of the outer mould (15, 31) in the axial direction can be introduced as soon as the value of a forming force which is introduced by means of the application members (4, 6) into the hollow member wall (22) which is intended to be formed reaches a limit value which indicates a complete filling of the evasion space (21) of the outer mould (15, 31) with plasticised material of the hollow member wall (22).
11. Apparatus according to claim 10, characterised in that the outer mould (31) is divided in the axial direction with a plurality of outer mould portions (34, 35) being formed, and in that the outer mould portions (34, 35), preferably by means of a controllable motorised drive, can be moved relative to each other in the radial direction with the outer mould (31) being opened thereby.
12. Apparatus according to claim 10, characterised in that the outer mould (31) is divided in the radial direction with a first axial outer mould portion (32) and a second axial outer mould portion (33) being formed, wherein the first part-length (19) of the receiving member wall (18) which forms an outer support face for the non-thickened hollow member wall (22) is provided on the first axial outer mould portion (32) and the evasion space (21) of the outer mould (31) is provided on the second axial outer mould portion (33) and in that the first axial outer mould portion (32) is divided in the axial direction with a plurality of outer mould portions (34, 35) being formed, and the outer mould portions (34, 35) of the first axial outer mould portion (32), preferably by means of a controllable motorised drive, can be moved relative to each other in the radial direction with the first axial outer mould portion (32) being opened thereby.
13. Machine for producing a hollow member (23) having a hollow member wall (22) which delimits a hollow space and which extends in an axial direction along a hollow space axis of the hollow space, in particular for producing a steering shaft which is in the form of a hollow shaft, characterised by the apparatus according to any one of claims 10 to 12.

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