Method for manufacturing thin sheets for laminates

Abstract

The invention relates to a method for producing stacks, i.e. laminations, for example laminations (20) for transformer cores or rotor or stator cores of electric machines from sheet metal (30). According to the invention, in a first production step (A), the individual laminations (20) are only partially detached from the sheet material (30), while the connection tabs (32) remain between the laminations (20) and the remaining frame part (31) of the sheet material (30). As a result, advantageously, the laminations (20) can be further processed (SP) separately, without the need to handle them individually and / or directly. Only afterwards, in a second production step (B) according to the invention, the laminations (20) are completely detached from the frame part (31) of the sheet material (30) by cutting said connection tabs (32) between the laminations (20).

Description

[Technical field]

[0001] The present invention relates to a method for producing stacks, i.e. laminations, e.g. laminations for transformer cores or rotor or stator cores of electric machines from sheet material, in particular metal, e.g. electromagnetic steel sheets. In the latter case, the laminations are typically (although not necessarily) either disk-shaped (rotor core) or ring-shaped (stator core). At least in the latter electrical applications of lamination stacks, the individual laminations of the lamination stack typically have a small thickness compared to their other dimensions, often with absolute thickness values ​​in the range of 0.05-0.5 mm. The present invention particularly relates to laminations having a maximum dimension at least 500 times and at most 2500 times the thickness dimension.

[0002] The laminations of the laminate stack are obtained individually by stamping, i.e. punching, from the sheet material. This process step of blanking is typically preceded by one or more successive punching, i.e. perforation, steps, in which holes for accommodating shafts, bolts, magnets or wire windings and / or holes for weight reduction or cooling are formed in the sheet material. These individually blanked laminations are stacked on top of each other in the desired amount to form a stack of laminations. In this latter respect, it is a known technique to form a laminate stack, i.e. to stack them on top of each other as part of the process step of blanking, i.e. punching the laminations successively from a continuously supplied strip of sheet material, the subsequently blanked laminations being stacked on top of the previously blanked laminations by the action of the same punch punch that cuts them from the sheet material. JP 2005-191031 A shows an example of such a known implementation, which has the advantage that the blanked laminations do not have to be handled individually (and delicately). Nevertheless, a clear disadvantage of JP 2005-191031 A is the inability to process the thin plates separately, in particular the inability to locally process the individual main faces of the thin plate (i.e. the upper and lower faces).

[0003] Against the above-mentioned known technical background, it is an object of the present invention to provide a method for producing a laminate stack, which on the one hand allows processing of the main faces of the sheets of the laminate stack and on the other hand avoids problems with individual handling of the sheets.

[0004] According to the invention, in a first step of the novel manufacturing method, the individual sheets are only partially detached from the sheet material, while connecting tabs, i.e. bridges, remain between the sheets and the remaining frame part of the sheet material (or between two directly adjacent sheets, i.e. no sheet material remains between such directly adjacent sheets). By means of these bridges, the sheets remain connected to such frame parts, in particular remain integral. As a result, the sheets, in particular their main faces, can advantageously be further processed separately, without the need to handle the sheets individually and / or directly. Instead, the sheets are advantageously handled indirectly via said frame part of the sheet material. For example, the frame part can be suitably pulled (or simultaneously pushed and pulled) to transport the sheets to, from or in a subsequent process step. Furthermore, in order to make such transportation, further processing easier and / or more economical or to allow storage and / or buffering, the frame part with the partially cut sheets can be suitably wound up in the form of a coil.

[0005] In particular, according to the invention, the lamella is partially separated from the sheet material by perforating the sheet material along the outer contour of the lamella and between said connecting bridges, whereby a number of spaced apart slots are formed in the sheet material along the outer contour of the lamella, the sheet material remaining between such slots thus forming said connecting bridges between the lamella and said frame part of the sheet material or between two directly adjacent lamellas.

[0006] It is noted that said first step of the novel manufacturing method may in principle be carried out simultaneously with said one or more successive drilling steps for forming holes in the body of the sheet (i.e. inside the outer contour of the sheet). Nevertheless, these latter drilling steps are preferably completed before said first step of the novel manufacturing method is carried out. Moreover, said first step itself may be carried out in several, i.e. separate successive drilling (sub) steps.

[0007] Furthermore, according to the invention, four or more bridges are left between each lamina and the frame part of the sheet material, which bridges are preferably arranged substantially equally spaced along the outer contour of the lamina. Moreover, at least four of the bridges are preferably at least partially oriented between the lamina and said frame part (or a directly adjacent lamina) in the direction in which the sheet material is fed, two bridges being located on either side of the lamina as viewed in such feeding direction. These features advantageously make it possible to avoid deformations of the lamina that may occur when the frame part is pulled and / or pressed to transport the lamina in said feeding direction. For the same reason, the bridges are preferably arranged mirror-symmetrically with respect to an imaginary center line of the lamina oriented in said feeding direction, and possibly also mirror-symmetrically with respect to an imaginary center line of the lamina oriented perpendicular to said feeding direction.

[0008] The number of bridges per lamina is preferably limited to facilitate bridge removal in post-fabrication processes of the laminate stack, and in this latter respect it has been found that applying more than 20 bridges per lamina typically adds no advantage.

[0009] Specifically, in the case of a substantially circular thin plate having a diameter D and a thickness in the range of 0.05 to 0.5 mm, the number of bridges NB is preferably: (π·D) / 85mm <NB<(π·D) / 45mm (1) [However, within the above constraints of at least 4 and at most 20 bridges] The range is selected from the range defined by:

[0010] Alternatively, if the design of the lamella exhibits R-fold rotational symmetry, the number of bridges NB is preferably set to ½, 1 or 2 times R, preferably also within the above constraints of at least 4 and at most 20 bridges.

[0011] At some point after said first step of the novel manufacturing method, in particular after the subsequent processing of the lamina in the frame part is completed (i.e. while the lamina is connected to the frame part via said bridges), the lamina is separated from the frame part of the sheet material in a second step of the novel manufacturing method by shearing or cutting the bridges at the outer contour of the lamina, i.e. completely cut off. For example, a laser cutting process or a mechanical cutting process may be applied for this purpose. In particular, the lamina may be separated by such known punching. However, in this case only the bridges need to be cut, and not the entire contour of the lamina, so that the required cutting forces are advantageously lower compared to conventional punching. By punching, a high cutting precision can be achieved, and furthermore, successively punched lamina can be advantageously stacked on top of each other by known techniques.

[0012] Preferably, the bridges coincide with, i.e. connect to, each sheet at the location of the recesses around its overall periphery, so that, after the sheets are separated, any part of the bridge that would disadvantageously remain connected to the sheet due to an imprecise cut or burrs left after the cut, etc., advantageously does not immediately protrude beyond the overall periphery of the sheet.

[0013] In the following, the method for producing a laminate stack according to the invention will be explained in more detail by means of an embodiment example with reference to the drawings. [Brief description of the drawings]

[0014] [Figure 1]FIG. 1 shows two typical examples of known laminations: a stator ring for a lamination stack of a stator core of an electric motor and a rotor disk for a lamination stack of a rotor core. [Diagram 2] FIG. 1 shows a schematic diagram of the basic configuration of currently relevant parts of the known lamination stack manufacturing method. [Diagram 3] FIG. 2 shows a schematic diagram of a first detail of the manufacturing method of the novel laminate stack according to the invention. [Figure 4] 1A-1D are schematic diagrams illustrating two particular embodiments of the manufacturing method of the novel laminate stack according to the present invention. [Diagram 5] FIG. 2 shows a schematic diagram of a second detail of the manufacturing method of the novel laminate stack according to the invention. [Figure 6] FIG. 2 shows a schematic diagram of a third detail of the manufacturing method of the novel laminate stack according to the invention.

[0015] FIG. 1 shows two examples of sheets 1 which can be suitably manufactured by the method for manufacturing a metal sheet stack described herein.

[0016] In the example shown on the left side of FIG. 1, the lamination 1 is in the form of a stator ring 10 for an electric motor, where a number of such stator rings 10 are axially stacked to form a lamination stack of a stator core. In the non-limiting example of the stator ring 10 shown, inside its circular outer contour, it is shown to include a number of holes 11 equally spaced around the circumference of the stator ring 10, which serve, for example, to accommodate assembly bolts or to conduct a cooling fluid. Furthermore, the inner contour of the stator ring 10 is shaped by a number of pole teeth 12 extending radially inwards and an equal number of radial slots 13 between the pole teeth 12, which serve to accommodate the windings of the electric motor's electrical wires.

[0017] In another example, shown on the right side of FIG. 1, the lamella 1 is in the form of a rotor disk 20 of an electric motor, in which a number of rotor disks 20 are stacked to form a rotor core lamination stack. In the non-limiting example of the rotor disk 20 shown, it is shown to include a central hole 21, which defines the inner contour of the rotor disk 20 and serves to accommodate a rotor shaft, which extends axially through the entire rotor core lamination stack, in which the rotor shaft is fixed in the electric motor. Furthermore, within the circular outer contour of the rotor disk 20, eight sets of four holes 22 are provided, which serve to accommodate permanent magnets in the electric motor. Each set of four magnet holes 22 is equally spaced along the circumference of the rotor disk 20, i.e. two such adjacent sets are arranged at an angle of 45° to each other.

[0018] In Figure 2 the basic arrangement of the relevant parts of the known lamination stack manufacturing process is illustrated diagrammatically in plan view of a strip of sheet material 30 in relation to the rotor disk 20 shown in Figure 1. In this Figure 2 and the following figures one or more portions of the sheet material 30 are shaded which are cut and removed from the sheet material 30 at each process step, i.e. punched or stamped. The sheet material 30 is fed in the direction of the arrow S, i.e. from left to right in Figure 2, typically in the form of a continuous strip drawn from a coil, to a so-called progressive stamping machine (not shown).

[0019] In a first step I of the known method, a set of pilot holes 40 are punched on both sides of the sheet material 30 by a punching punch and die pair of a progressive stamping machine. These pilot holes 40 are later used to accommodate positioning pins (not shown) in the progressive stamping machine (i.e. towards the right in FIG. 2) and serve to align the sheet material 30 in the machine. In a second step II of the known method, further (sets of) holes 21, 22 are punched in the sheet material 30 by a further punching punch and die pair, these further holes 21, 22 corresponding to the shaft holes 21 and magnet holes 22 of the rotor disk 20 that have not yet been cut. It is noted that typically, depending on the geometrical complexity of the sheet 1, said first step I and said second step II of the known lamination stack manufacturing method can be integrated into a single process step, divided into several process steps or combined. For example, in this regard, the drilling of pilot holes 40 may be combined with the drilling of shaft holes 21 in a first step, with magnet holes 22 being drilled in a second step.

[0020] In a third step III of the known method, the rotor disk 20 is cut from the sheet material 30 by a punch and die pair of a progressive stamping apparatus in a known manner. The punched rotor disk 20 exits the progressive stamping apparatus as indicated diagrammatically by arrow E, whereby it is either placed directly onto a laminated stack of rotor disks or is transported separately for further processing as indicated diagrammatically by arrow SP, before such lamination is carried out. In a fourth step IV of the known method, the remaining frame portion 31 of the sheet material 30 exits the progressive stamping apparatus.

[0021] The present invention aims to improve known lamination stack manufacturing methods. According to the invention, such improvement is realized by a novel lamination stack manufacturing method, the first detail of which is shown diagrammatically in FIG.

[0022] The first and second steps II shown in Fig. 3 correspond to those shown in Fig. 2. However, then, in a first step A of the novel method, a number of mutually spaced apart slots 23 are punched in the sheet material 30 along the outer contour of the rotor disk 20, so that the rotor disk 20 remains an integral part of the sheet material 30. In other words, in this first novel step A, connecting bridges 32 are left between the rotor disk 20 and the frame part 31 of the sheet material 30, which connecting bridges 32 are defined by and between said slots 23. After such a first novel step A, the rotor disk 20 leaves the progressive stamping device while still being connected to the frame part 31 of the sheet material 30 via said bridges 32 for a suitable transport T and further processing SP of the rotor disk 20. Such subsequent processing SP may include annealing heat treatment of rotor disc 20, applying an adhesive to rotor disc 20, and / or applying a coating to rotor disc 20, such as an electrically insulating coating (not shown).

[0023] In the embodiment of the invention shown in FIG. 3, four bridges 32 are left between each rotor disk 20 and the frame part 31 of the sheet material 30. In this embodiment, the number of bridges is preferably equal to 1 / 2R, since the rotor disk 20 has an 8-fold rotational symmetry R. Moreover, in this embodiment, the four bridges 32 are equally spaced along the outer contour of the rotor disk 20, two bridges 32 likewise preferably present on either side of the rotor disk 20 with mirror symmetry both with respect to the feed direction S and with respect to the perpendicular direction thereto. Additionally, the four bridges 32 are advantageously oriented at least partially in the feed direction S of the sheet material 30 between the rotor disk 20 and said frame part 31, rather than (exclusively) perpendicular to it. The particular arrangement of the bridges 32 advantageously makes it possible to avoid deformations of the rotor disk 20 that may occur when said frame part 31 is pulled in the feed direction S for transporting the sheet material 30, in particular for winding it up.

[0024] At some point after said first step A of the novel manufacturing method, in particular after said further processing SP thereof, the rotor disks 20 in the frame part 31 are conveyed T to a cutting device and separated from each other in a second step B of the novel manufacturing method. In such second step B, the rotor disk 20 is thus completely separated from the frame part 31 of the sheet material 30 by shearing or cutting the bridges 32. In the illustrated embodiment, the rotor disk 20 is separated, i.e. the bridges 32 are cut from the outer contour of the rotor disk 20 by punching. After being separated, the rotor disk 20 is preferably placed P directly on the laminated stack of rotor disks. And after the rotor disk 20 has been separated, the remaining frame part 31 of the sheet material 30 leaves the cutting device, corresponding to said fourth step IV of the known method.

[0025] It should be noted that, as shown on the left side of FIG. 4 for two adjacent rotor disks 20-1 and 20-2, some of the slots 23-1 and 23-2 along the respective contours may in principle at least partially overlap. Such overlap may be in the feed direction S or may be perpendicular to the feed direction S if two or more parallel rows of rotor disks 20 are cut simultaneously from a sufficiently wide sheet material 30. In this case, the sheet material 30 is used very efficiently, since the size of the frame portion 31 is reduced. In particular, as shown on the right side of FIG. 4, the slots 23-1 and 23-2 on both sides of each bridge 32 may be arranged to overlap, so that each such bridge 32 directly connects the two adjacent rotor disks 20-1 and 20-2 without the frame portion 31 in between.

[0026] Obviously, these latter two specific aspects of the invention are independent of any particular sheet geometry and therefore may be applied within the context of the invention generally, and not just with respect to rotor disk 20.

[0027] A second detail of the manufacturing method of the novel lamination stack according to the invention is shown diagrammatically in FIG. 5. This second detail is particularly suitable for simultaneously manufacturing both stator laminations and rotor laminations of an electric motor. In particular, in this second detail, each rotor disk 20 is cut from the sheet material 30 concentrically inside the inner contour of each stator ring 10, which is (supposed to be) cut from the sheet material 30 as well. This results in an efficient use of the sheet material 30, since the material radially inside the stator ring 10 is not completely scrapped, but is instead largely used for the manufacture of the rotor disks 20. This second detail of the manufacturing method of the novel lamination stack according to the invention also starts from the sheet material 30 prepared with the necessary stator holes 14 and rotor holes 24, the arrangement of which is determined by said mutually concentric arrangement of the stator rings 10 and rotor disks 20 to be cut.

[0028] In a first step A of the embodiment of the invention shown in FIG. 5, two sets of eight mutually spaced apart slots 15, 25 are punched in the sheet material 30. The first set of holes 15 follows the outer contour of the stator ring 10 to be cut, and the second set of holes 25 follows both the inner circumference of the stator ring 10 and the outer contour of the rotor disk 20. Eight bridges 32 are thus left between each set of slots 15, 25, respectively connecting the stator ring 10 to the frame part 31 of the sheet material 30 and connecting the rotor disk 20 to the stator ring 10. After such a first novel step A, the stator ring 10 and the rotor disk 20 leave the progressive stamping device while still being connected to the frame part 31 of the sheet material 30 via said bridges 32 for suitable transport T and further processing SP of the stator ring 10 and the rotor disk 20.

[0029] At some point after said first step A of the novel manufacturing method, in particular after said further processing SP thereof, the stator ring 10 and the rotor disks 20 in the frame part 31 are conveyed T to a cutting device and separated from each other in a second step B of the novel manufacturing method. Thus, in such second step B, the stator ring 10 and the rotor disks 20 are completely separated from the frame part 31 of the sheet material 30 and from each other by shearing or cutting the bridges 32. In the embodiment of the invention shown in Figure 5, this second step B comprises three stages B1, B2 and B3.

[0030] In a first stage B1 of the second step B, the rotor disk 20 is completely detached from the stator ring 10 by cutting the first set of bridges 32-1 at the outer contour of the rotor disk 20. After being detached, the rotor disk 20 is preferably placed directly on the rotor disk lamination stack as indicated diagrammatically by the arrow P20. In a second stage B2 of the second step B, the same first set of bridges 32-1 is cut from the inner circumference of the stator ring 10, thereby completing the inner contour shape of the stator ring 10, while said first set of bridges 32-1 is discharged as scrap from the cutting device. In a third and final stage B3 of the second step B, the stator ring 10 is completely detached from the frame portion 31 of the sheet material 30 by cutting the second set of bridges 32-2 at the outer contour. After being detached, the stator ring 10 is preferably placed directly on the stator ring lamination stack as indicated diagrammatically by the arrow P10. Also, after the stator ring 10 has been cut off, the remaining frame portion 31 of the sheet material 30 leaves the cutting device, corresponding to the aforementioned fourth step IV of the known method.

[0031] According to the invention, the positioning and cutting of the first set of bridges 32-1 is particularly important in terms of the operational performance of the final electric motor, in particular its optimal reluctance. Therefore, preferably, the cutting in said first stage B1 and second stage B2 of the second step B is performed with high precision, in particular with high precision compared to the cutting of the second set of bridges 32-2. Ideally, the first set of bridges 32-1 between the outer contour of the rotor disc 20 and the inner circumference of the stator ring 10 is cut by a pair of blanking punch and die. Furthermore, the positioning of said first set of bridges 32-1 is preferably performed in accordance with the following two features, as shown in detail in the enlarged inset of FIG. 5: - the bridge 32-1 is connected to the rotor disc 20 at a recess in the outer contour of the rotor disc 20, so that the outer periphery of the rotor disc 20 to be cut is locally deviated radially inwards from the imaginary circle; - a bridge 32-1 is connected to the stator ring 10 between two pole teeth 12, i.e. along a radial slot 13 between the two pole teeth 12, so that each of said pole teeth 12 is tangentially connected to each other by a respective bridge 32-1. Ideally, at this point, each bridge 32-1 is only tangentially connected to each of the pole teeth 12, and not radially (inwardly), so that the radially inner surface of the pole teeth 12 is (completely) cut off in said first step A of the novel manufacturing method; Either or both of the following are satisfied.

[0032] The placement of these bridges may, for example, ensure that rotor / stator interference is avoided in an end product electric motor and / or may maximize reluctance in such end product electric motor.

[0033] Additionally, each bridge 32-1 of the first set is preferably connected to rotor disk 20 such that each magnet hole 22 is close to the outer contour (not shown) of rotor disk 20 to improve the mechanical strength of rotor disk 20 through work hardening when cutting bridge 32-1.

[0034] A third detail of the manufacturing method of the novel lamination stack according to the invention is shown diagrammatically in Fig. 6. This third detail is similar to the second detail described above, with the difference that in the first step A of the third detail, only one set of eight spaced apart slots 15, i.e. holes 15 following the outer contour of the stator ring 10 to be cut, are drilled in the sheet material 30. Thus, in this third detail, the stator ring 10 and the rotor disk 20 remain as one piece 50 after the first step A of the novel manufacturing method.

[0035] Then, in a first stage B1 of this second step B of the third detail, the rotor disk 20 is punched out of the sheet material 30 in the conventional manner, i.e. cut along the entire outer contour of the rotor disk 20. This has the advantage that such an outer contour can be formed with high precision by said work hardening, which affects it along its entirety. Then, in a second stage B2 of this second step B, a thin ring is cut 30 from the inside of the inner circumference of the stator ring 10, whereby an opening occurs up to the radial slots 13 preformed as stator holes 14 in the first step I or in the second step II of the conventional process, thus completing the inner contour of the stator ring 10. The ring thus cut is discharged as scrap from the cutting device. Finally, in a third stage B3 of the second step B, the stator ring 10 is completely detached from the frame part 31 of the sheet material 30 by cutting the bridges 32 defined in the outer contour of the stator ring 10 between said slots 15.

Claims

1. A method for manufacturing pairs of lamellas (10, 20; 50) consisting of a stator ring (10) and a rotor disk (20) intended for the stator lamination and rotor lamination of an electric motor, respectively, from a sheet material (30), in a first process step (A), the stator ring (10) of at least each pair of lamellas (10, 20; 50) is cut from the sheet material (30) by drilling a number of slots (15) along its outer contour. a second process step (B) in which the stator ring (10) is partially cut away from the stator ring (10) while a corresponding number of connecting bridges (32; 32-2) are left between each pair of lamellas (10, 20; 50) and the frame portion (31) of the sheet material (30) or the adjacent lamellas (1; 10; 20; 50), and in which in a second process step (B) the bridges (32; 32-2) are cut along the outer contour of the stator ring (10).

2. 2. A method for manufacturing pairs of laminations (10, 20; 50) according to claim 1, characterized in that, before cutting the bridges (32; 32-2) along the outer contour of the stator ring (10) in the second process step (B), first the rotor disks (20) are cut from the sheet material (30), and subsequently a ring of scrap material is also cut from the sheet material (30) at the inner contour of the stator ring (10).

3. In the first process step (A), the rotor disk (20) of each pair of laminations (10, 20; 50) is also partially separated from the sheet material (30) by drilling a number of slots (15) along its outer contour, while a corresponding number of connecting bridges (32; 32-1) are left between the rotor disk (20) of each pair of laminations (10, 20; 50) and the stator ring (10), 2. A method for manufacturing pairs of laminations (10, 20; 50) according to claim 1, characterized in that, before cutting the bridges (32; 32-2) along the outer contour of the stator ring (10) in the second process step (B), the bridges (32; 32-1) are first cut along the outer contour of the rotor disc (20), and then these same bridges (32; 32-1) are also cut along the inner contour of the stator ring (10).

4. 4. A method for manufacturing a pair of laminations (10, 20; 50) according to claim 3, characterized in that the bridges between the rotor disk (20) and the stator ring (10) are connected to the stator ring (10) only at the locations of slots (13) extending radially outward in the inner contour of the stator ring (10).

5. 3. A method for manufacturing a lamella (1; 10; 20; 50) or a pair of lamellas (10, 20; 50) according to claim 1 or 2, characterized in that the bridges (32) connect each lamella (1; 10; 20; 50) at the location of a recess around its entire periphery.

6. 3. A method for producing a sheet (1; 10; 20; 50) or a pair of sheets (10, 20; 50) according to claim 1 or 2, characterized in that between the first process step (A) and the second process step (B), the sheet (1; 10; 20; 50) is treated, in particular subjected to a heat treatment and / or provided with a coating or adhesive.

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