Device for forming metal workpieces and method for the production thereof

Abstract

The invention relates to a device for forming a metal workpiece, comprising a mould with an upper mould and a lower mould which are moved relative to one another in the mould stroke range by means of a lifting device, and comprising a fixed clamping device for the force-fitting of a first side leg, the invention relates to a method for forming a bow in a lower die by means of a die stroke such that a second leg approaches a first leg, characterized by a slide that can be moved parallel to the workpiece plane and perpendicular to the longitudinal extension of the legs, said slide being mechanically coupled to a lifting device by means of a curved guide rail and a guide block guided therein, and a forming device provided so that the slider can move in a forward direction corresponding to the approaching direction of the second leg by means of the linear movement of the lifting device, the forming device being provided so as to form the bow part while the first leg is fixed and the second leg is free. The guide rail is shaped in such a way that the slide always bears against the side of the second leg facing away from the first leg in a force-applying manner during the shaping.

Description

Technical Field

[0001] The invention relates to a device for forming a metal workpiece in the shape of two parallel legs, a first leg and a second leg, the legs being connected on one side by a bow, wherein at least the legs extend in a common workpiece plane, the device comprising:

[0002] - a mold with an upper mold and a lower mold, which are movable relative to each other within the mold stroke range by a lifting device, and

[0003] - a fixed clamping device for a non-positive fit of the first leg,

[0004] The forming device is configured to form the bow portion inserted into the lower die through die stroke, resulting in the second leg approaching the first leg.

[0005] The invention also relates to a method for producing such a forming device. Background Art

[0006] Such a forming device is known from document JP 7372398 B1.

[0007] During operation, very high currents flow through the stators of high-power electric motors, such as those used in traction drives of motor vehicles. Therefore, the electrical conductors forming the so-called stator windings must have a large, uniform cross-section over their entire length and be manufactured with high precision. Even minor wiring faults can lead to localized heating, which can directly or indirectly cause malfunctions or even damage due to thermal expansion. These disturbances can manifest themselves in the form of localized variations in the conductor's cross-section and / or localized mechanical stresses in the conductor material. Furthermore, the conductors in the stator must be positioned very closely together, resulting in complex shapes, particularly in so-called "hairpin" areas—i.e., areas where the conductor's direction of extension deflects. These complex shapes often cannot be fully achieved in terms of manufacturing while maintaining the required interference-free performance. Consequently, comprehensive forming methods are required in all cases to meet all requirements.

[0008] Document EP3484029A1 discloses the production of such a hairpin by forming a substantially U-shaped blank. The blank consists of two parallel legs with a substantially rectangular cross-section, connected by a bow of identical cross-section. All forming elements, namely the legs, such as the bow, lie in a common workpiece plane. This document proposes forming the bow and the adjacent leg regions in a bow mold, wherein the bow is bent about a bending axis located centrally between the legs. This inevitably involves lateral movement of the legs toward each other and rotation about their longitudinal axis. This bending of the bow from the workpiece plane occurs in a first method step, namely, the stroke of the bow mold. The stroke of the mold is generally understood to mean the relative movement of the upper and lower dies. In practice, the lower die is typically fixed to the machine base, while the upper die moves vertically relative to the machine base. The specific design of the relative movement of the upper and lower dies, which can optionally be arranged at the same vertical height in a horizontal press, is not important in the context of the present invention. In known forming devices, the bow mold is laterally divided into two parts. In the second method step, the two transverse sections are vertically offset relative to each other in the clamped state, resulting in a bend in the bow region clamped therebetween. This forming step results in a stretching of the shorter material section located between the transverse sections of the bow mold, which is therefore not itself clamped. This is associated with a tapering cross section. Furthermore, stresses are generated in the material. Therefore, the bend required in the hairpin bow region (also known as an S-bend in technical terms) for geometrical reasons provides space for the interference that should be optimally avoided, as described above.

[0009] JP7372398B1, a document of this type mentioned at the outset, discloses a forming device with multiple separate forming stations. As the starting workpiece, a straight metal bar is clamped at its ends and radially aligned in a clamping device on a gradually rotating circular pad. With each rotational step, the workpiece is transferred to a further forming station and thereby first bent into a flat hairpin with parallel legs, the first of which is still clamped at its end on the circular pad. In further rotational steps, this preform is transferred to the die to form the bow. Once the bow is positioned in the lower die, the clamping of the end of the first leg on the circular pad is released, and the auxiliary clamping continues to close around the first leg to maintain the position of the hairpin until the upper die is lowered into the lower die to form the bow. At this point, the auxiliary clamping is released, allowing the two legs to move essentially freely toward each other and simultaneously undergo twisting about their longitudinal axis. This free "wobbling" of the legs leads to difficult-to-reproduce results. Therefore, the hairpin, which is once again only clamped at the end on the round pad, must be transferred to a correction station where the second leg is clamped by a movable clamping device under video monitoring and bent correctly into the desired end position. This approach is obviously very expensive. Summary of the Invention

[0010] The object of the present invention is to reliably and reproducibly form the S-shaped bend of a hairpin with minimal effort.

[0011] The above technical problem is solved in combination with the features of the preamble of claim 1, namely, by a slider that can be moved parallel to the workpiece plane and perpendicular to the longitudinal extension of the leg, the slider being mechanically coupled to the lifting device via a curved guide rail and a guide block guided therein, so that the slider can be moved in a forward direction corresponding to the approach direction of the second leg through the linear movement of the lifting device, wherein the forming device is arranged to form the bow portion inserted into the lower die with a first leg fixed by a clamping device and a free second leg, and wherein the guide rail is formed so that the slider always rests on the side of the second leg facing away from the first leg in a force-applying manner during forming.

[0012] Preferred embodiments of the invention are the subject matter of the dependent claims.

[0013] First, the present invention provides that the bow is formed while the first leg is fixed in a force-fitting manner. Thus, during the forming process, only the second leg remains movable to perform the required approach movement. This eliminates one degree of freedom. The torsion caused by the bow forming can already be taken into account when the first leg is clamped. To this end, the clamping claws forming the clamping device are shaped so that when the clamping device is closed, the first leg is already in its torsional end position and thus fixed. Due to the shape and material elasticity of the hairpin, this creates a preload that presses the bow securely into the lower die. The pressure relief of this preload caused by the clamping device occurs simultaneously within the die stroke during which the bow forming occurs. However, the opposite scenario is also conceivable, where the clamping device fixes the first leg in its initial torsional position, so that torsional stresses build up within the die stroke, with the first leg elastically following these stresses after the bow forming. However, these details of the clamping device for the first leg are not central to the present invention.

[0014] The present invention also includes a mechanical slide that, during the bow forming process, rests externally against the second leg with force applied to support its approach movement toward the first leg and suppress "chatter." However, this approach movement does not occur uniformly, i.e., at a constant speed. Instead, its form depends on the detailed bow forming process. The exact shape can only be determined based on the details of the specific mold. However, according to the present invention, this uneven movement is achieved in each case by a correspondingly shaped curved path, via which the slide is coupled purely mechanically to the (essentially uniform) mold stroke.

[0015] In order to determine the special shape of the curved track or to manufacture a forming device of corresponding equipment, different methods are feasible. In principle, it is conceivable that the motion of the second leg is detected in a sensory manner without the slider according to the present invention and the required curved track shape is determined by corresponding conversion of the actual leg motion. However, this method is disadvantageous here because when detecting the actual leg motion without the slider, its undesirable and non-reproducible "vibration" will also be detected. But this should be suppressed by the slider. As an improvement to this method, it is conceivable that the slider is equipped with a controllable motor and a force control system is set for it. However, this method is obviously very consuming. In addition, once this effort is made, it is possible to abandon the purely mechanical slider control system that is obviously more cost-effective through the guide rail.

[0016] In contrast, it is currently particularly advantageous to determine the course of the second leg's approach movement using an FEM simulation (FEM: Finite Element Method). This simulation allows the calculation of the ideal movement of the second leg imposed by the bow shaping, without causing side effects such as "trembling" that occur in reality. This ideal leg movement is to be mirrored by the slider. The results of the FEM simulation can then be converted into the shape of at least one section of the guide rail. If such pre-set values are present, it is easy for a person skilled in the art to create a guide rail for mechanically coupling the slider to the lifting device, which has at least one center portion corresponding to the thus-shaped guide rail section. This results in a device according to the present invention, whose slider follows the ideal leg movement or forces the actual leg movement into the ideal leg movement through a purely mechanical coupling. This method is a separate invention and is the subject of parallel claim 9.

[0017] Independent of the specific manner in which the shape is determined, a guide rail advantageously results that has a sequence of regions with different slopes, through which the uniform linear motion of the lifting device can be converted into a corresponding sequence of segments of slide motion with different speeds. It is particularly preferred that the guide rail include a central portion having a sequence of regions with different slopes, through which the uniform linear motion of the lifting device between the first contact of the upper die with the bow and the end position of the die stroke can be converted into a corresponding sequence of segments of slide motion in the forward direction with different speeds, which as a whole corresponds to the approach movement of the second leg. The functional section of the guide rail, referred to here as the central portion, corresponds to the implementation of the basic concept according to the present invention described above.

[0018] However, the guide rail need not be limited to the central portion. Therefore, a refinement of the present invention provides for the guide rail to include a guide section with a uniform slope adjacent to the central portion. This guide section converts the uniform linear motion of the lifting mechanism into a section of sliding motion with a uniform speed in the forward direction before the upper die and the bow make their first contact. This allows for the control of manufacturing tolerances in the initial workpiece. Such tolerances could include, for example, non-completely parallel alignment of the legs. For example, the distance between the legs could increase toward their open ends. If the slide is already in its starting position when the workpiece is inserted into the forming device, it could collide with the workpiece, making insertion difficult or impossible. The slide is in this starting position at the start of the active forming process, i.e., when the upper die first contacts the bow. Therefore, the refinement provides for the slide to be positioned backward from the starting position at the beginning of the die stroke to allow for the insertion of imperfect initial workpieces. Within the first stroke section before the initial contact between the upper die and the bow, the slide is brought to the starting position by the guide rail guide section. In the event of an imperfect, upwardly curved workpiece, the second leg is simultaneously forced into the correct initial position.

[0019] Alternatively or additionally, the guide rail may include a trailing section adjacent to the central section (on the other side) with a monotonically increasing slope. This trailing section allows the uniform linear motion of the lifting device to be converted into a section with a monotonically increasing velocity in the forward direction after reaching the end position of the mold stroke. In other words, after the actual bow formation is completed, the slide continues to advance in the forward direction, thereby moving the second leg inward beyond the reached end position, i.e., onto the first leg. This method recognizes that once the slide comes to rest against the second leg with force applied, the material elasticity and form resilience of the formed hairpin will cause the second leg to return outward to a certain extent. This is counteracted by an overbending of the second leg. The trailing section of the guide rail is used to compensate for this overbending. In order to effectively utilize this trailing section of the guide rail by a corresponding trailing movement of the slide, it is obviously necessary for the lifting device to continue its movement even after the mold is finally closed. However, this is already the case in conventional presses in which the upper die is coupled to the lifting device via a spring.

[0020] In a preferred embodiment of the present invention, guide rail forms the two-way guiding of guide block. This means that when the mold is opened, when the lifting device experiences the opposite motion with the mold stroke of shaping, slide block is returned in the initial position by reverse forced guiding.

[0021] In contrast, an alternative embodiment provides for the guide rail to provide only unidirectional guidance for the guide shoe, and the slide is spring-loaded in the opposite direction of its advancement. In this design, the slide is reset independently of the mold opening movement by the force of a spring, which is already tensioned during the advancement of the slide. This design offers greater freedom in selecting the guide rail shape, which then only needs to allow for a "soft" transition between the individual sections in one direction.

[0022] Basically, a combination of the two embodiments in terms of bidirectional forced guidance of the slide with spring assistance during retraction is also conceivable. BRIEF DESCRIPTION OF THE DRAWINGS

[0023] Further features and advantages of the invention will be apparent from the following detailed description and the accompanying drawings.

[0024] in:

[0025] Figure 1 A perspective view showing a preferred embodiment of a workpiece blank,

[0026] Figure 2 shows the workpiece after forming according to the invention,

[0027] Figure 3 A fragmentary view showing a forming device according to the invention,

[0028] Figure 4 Show Figure 3 A detailed schematic diagram of the guide rail / guide shoe coupling of the forming device; and

[0029] Figure 5 A schematic diagram of a coupling block with a guide rail according to the invention is shown. DETAILED DESCRIPTION

[0030] The same reference numbers in the drawings indicate the same or similar elements.

[0031] Figure 1 A preferred embodiment of a workpiece 10 to be formed according to the invention is shown in a perspective view in the blank phase. In this state, the legs 101 and, in the embodiment shown, the adjoining bow 102 lie in a common workpiece plane, which in the embodiment shown is simultaneously the plane of symmetry for the essentially rectangular cross-section of the legs 101 and bow 102.

[0032] Figure 2 A workpiece 10 formed according to the present invention is shown. It can be seen that the bow 102 is deformed perpendicularly to the bow or workpiece plane and, in particular, exhibits a so-called S-shaped bend. Simultaneously, the legs 101 are brought closer together in the transverse direction according to the transverse movement arrows 31. Furthermore, the legs 101 are twisted about their longitudinal axis according to the twisting arrows 32.

[0033] Figure 3 The workpiece 10 is shown in the lower die 22 of the forming device 20, which is only partially shown (i.e. without the corresponding upper die). The workpiece 10 is shown twice here, i.e. once in its blank phase and once in its final formed phase. The forming of the lower die 22 allows Figure 3 The clamping of the first leg 101a shown on the right, on the other hand, allows Figure 3 The second leg 101b shown on the left is moved by the shaping of the bow 102 within the mold stroke. A person skilled in the art is familiar with the basic design (not shown) of the upper mold and the lifting device by which the upper mold can be fed in the direction of the lower mold 22 within the mold stroke.

[0034] Essential to the invention is the slide 24, which can be moved into the recess 221 in the lower die 22. This slide can be moved parallel to the workpiece plane (relative to the workpiece in the blank phase) and perpendicular to the longitudinal extension of the legs. During the movement of the second leg 101b toward the first leg 101a, the slide must permanently bear against the outside of the second leg 101b with force applied to prevent it from "fluttering" during the approach movement caused by the bow forming. To achieve this, the slide 24 must execute a movement that precisely corresponds to the lateral movement of the second leg 101b.

[0035] To achieve this purpose, the slider 24 is fixed on the coupling block 26, as shown in FIG. Figure 4 As shown, the coupling block has a guide rail 261, in which the guide block 281 of the coupling element 28 engages. The coupling element 28 is connected to the lifting device and performs the vertical movement (vertical movement arrow 33) predetermined by it during the mold stroke. By engaging the guide block 281 in the guide rail 261, this vertical movement is converted into a horizontal movement (horizontal movement arrow 34), i.e., the forward movement of the slide 24. Those skilled in the art will appreciate that the illustrated selection of the vertical movement of the coupling element 28 and the horizontal movement of the slide 24 is not mandatory and depends on the basic orientation of the forming device 20. Other conversions other than right-angle conversions can also be achieved by the guide rail / guide block coupling.

[0036] exist Figure 4 The guide rail 261 is shown to be overly simplified and substantially straight, but this is generally not sufficient for the complex lateral movement of the second leg 101b. Figure 5 The preferred shape of the guide rail 261 is shown. It basically has three parts, namely the leading part I, the central part II and the downstream part III. The central part II is important to the present invention; the leading part I and the downstream part III both represent preferred improved designs.

[0037] It can be seen that the central portion II of the guide rail 261 is composed of sections of different inclinations. The guide block 281 guided and forced to move uniformly vertically in the guide rail 261 causes the coupling block 26 and thereby causes the Figure 5 The desired movement can be determined by finite element simulation of the ideal movement of the second leg 101b during the forming process. The required curve trajectory 261 can be easily calculated by a person skilled in the art.

[0038] The guide section 1 has a consistently steep slope and serves to quickly move the slide 24 from a relatively distant preparation position to its starting position at the start of the forming process. The initial distance from the starting position allows the insertion of workpieces 10 even with incorrectly upwardly bent legs 101a, b. At the start of the forming process, the workpiece 10 is bent into the correct starting position as it passes over the guide section 1. However, if the workpiece 10 is already correctly formed when it is inserted, contact only occurs between the slide 24 and the second leg 101b as it passes over the guide section 1.

[0039] Subsequent portion III has a monotonically increasing inclination and is passed after the actual bow portion shaping is finished. Here, the second leg 101b carries out a strong overbending, which has proved helpful in compensating its inherent elasticity.

[0040] Of course, the embodiments discussed in the detailed description and illustrated in the figures are merely illustrative examples of the present invention. Numerous possible variations are within the purview of those skilled in the art based on this disclosure. In particular, the specific shape of guide rail 261 must be selected based on the specific circumstances of the individual application, taking into account the specific S-bend shape and material properties of workpiece 10, such as material type, ductility, elasticity, hardness, temperature, etc. The aforementioned FEM simulation method is applicable for this purpose.

[0041] Reference Signs List

[0042] 10 workpieces

[0043] 101a First Side Leg

[0044] 101b Second Side Leg

[0045] 102 Bow

[0046] 20 forming device

[0047] 22 lower die

[0048] 221 grooves

[0049] 24 Sliders

[0050] 26 coupling blocks

[0051] 261 guide rail

[0052] 28 coupling elements

[0053] 281 guide block

[0054] 31 horizontal movement arrows

[0055] 32 Twisting Arrow

[0056] 33 vertical motion arrows

[0057] 34 horizontal motion arrows

[0058] The pilot unit of I261

[0059] The center of II261

[0060] The sequel to III261

Claims

1. A device (20) for shaping a metal workpiece (10), the metal workpiece (10) having a shape with two parallel legs (101a, b), namely a first leg (101a) and a second leg (101b), connected on one side by a bow (102), wherein: At least the legs (101a, b) extend in a common workpiece plane, the device comprising: - a mold with an upper mold and a lower mold (22), which are movable relative to each other within the mold stroke range by a lifting device, and - a clamping device for the non-positive fixing of the first leg (101a), The forming device (20) is configured to form the bow portion (102) placed in the lower mold (22) through a mold stroke, resulting in the second leg (101b) approaching the first leg (101a). It is characterized by being provided with A slide (24) is movable parallel to the plane of the workpiece and perpendicular to the longitudinal extension of the leg, the slide being mechanically coupled to the lifting device via a curved guide rail (261) and a guide block (281) guided therein, so that the slide can be moved in an advancing direction corresponding to the approach direction of the second leg (101b) by the linear movement of the lifting device, The forming device (20) is configured to form the bow portion (102) inserted into the lower mold (22) with the first leg (101a) fixed by the clamping device and the second leg (101b) free. The guide rail (261) is formed so that the slide (24) always bears against the side of the second leg (101b) facing away from the first leg (101a) in a force-exerting manner during the forming process.

2. The device (20) according to claim 1, characterized in that The guide rail (261) has a sequence of regions with different inclinations, by which the uniform linear motion of the lifting device can be converted into a corresponding sequence of segments of slide motion with different speeds.

3. The device (20) according to one of the preceding claims, characterized in that The guide rail (261) comprises a central portion (II) having a sequence of regions of different inclinations, whereby the uniform linear movement of the lifting device between the first contact of the upper mould with the bow portion (102) and the terminal position of the mould stroke can be converted into a corresponding sequence of sections of the slider movement in the forward direction with different speeds, the slider movement as a whole being equivalent to the approach movement of the second leg (101b).

4. The device (20) according to claim 3, characterized in that The guide rail (261) comprises a leading portion (I) with a uniform slope adjacent to the central portion (II), through which the uniform linear movement of the lifting device before the first contact between the upper mold and the bow portion (102) can be converted into a section of slider movement with a uniform speed in the forward direction.

5. The device (20) according to any one of claims 3 to 4, characterized in that The guide rail (261) comprises a subsequent portion (III) adjacent to the central portion (II) having a monotonically increasing slope, through which the uniform linear movement of the lifting device can be converted into a section with a monotonically increasing speed in the forward direction after reaching the terminal position of the mold stroke.

6. The device (20) according to one of the preceding claims, characterized in that The guide rail (261) forms a two-way guide for the guide block (281).

7. The device (20) according to one of the preceding claims, characterized in that The guide rail (261) only forms a one-way guide for the guide block (281) and the slide (24) is spring-loaded in the opposite direction to its advancing direction.

8. The device (20) according to one of the preceding claims, characterized in that The shape of the guide rail (261) is determined by converting the results of an FEM simulation of the approach movement of the second leg (101b).

9. A method for producing a forming device (20) according to one of the preceding claims, comprising the following steps: - determining the course of the approach movement of the second leg (101b) by means of FEM simulation, - determining the shape of the guideway segment by converting the determined approach movement, - Producing a guide rail (261) having a central portion (II) corresponding to the guide rail section thus determined for mechanically coupling the slide (24) to the lifting device.

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