Method and apparatus for manufacturing a lamination stack

Abstract

A method of manufacturing a lamellar stack (1) for an electric motor comprises steps : -blanking lamination pieces (2) and -filling the lamination pieces (2) into a well (130), such that the lamination pieces (2) form said lamellar stack (1), whereby lamination layers (4) being stacked upon each other in an axial direction (X-X). Each lamination (2,4) comprises recesses (42), defining grooves in an outer surface of the lamellar stack (1), preferably grooves with a narrowed access. A side wall (132) of the well (130) comprises retaining elements (133) extending along the axial direction (X-X), preferably being dovetail shaped. Each retaining element (133) of said well (130) is configured to restrict movement between a recess (42) of a lamination piece (2) in the well (130), especially a movement in radial or circumferential direction is avoided.

Description

[0001] METHOD AND APPARATUS FOR MANUFACTURING A LAMINATION STACK

[0002] DESCRIPTION

[0003] Field of the invention

[0004] The present invention belongs to the field of electric motors for automotive applications. In particular, the invention relates to a method and an apparatus for manufacturing a lamellar pack for such an electric motor.

[0005] Background of the invention

[0006] Electric motors are well known to include a stator and a rotor, each comprising a ferromagnetic core which could be manufactured as a lamellar pack, that is a stack of a plurality of lamination layers.

[0007] Apparatuses are known for manufacturing such lamellar packs, with a blanking device that blanks lamination pieces out of a lamination board. The lamination pieces are filled into a well, below the blanking device or in a further apparatus downstream the blanking device. The lamination pieces are so arranged in the well, as to form a plurality of lamination layers stacked on each other. Each lamination layer could be made of just one lamination piece, or as an assembly of plural lamination pieces arranged side by side.

[0008] While the overall shape of each lamination piece could be an annular shape or an annular sector shape, this shape may have additional features requiring a precise vertical alignment of the lamination pieces of different layers. i For example, it is common that each layer may have though slots, which are intended to receive conductive windings and / or permanent magnets after the lamellar pack is completed. The through slots should be properly aligned.

[0009] However, during manufacture, there is a risk that the lamination pieces move inside the well, going out of alignment and / or falling in the central hole of the lamellar pack being formed. Such movements may be caused by the punch or by movements of the well itself, which may be intended to rotate between successive blanking strokes.

[0010] In order to align the lamination pieces as they are filled in the well, and prevent their movement, it is known from IT 202000003602 to provide retaining members inside some of the slots. These retaining members are made from the same material of the lamination layers, which is locally subject to partial blanking. This creates a plate with a relief having a male side and a female side. Thus, the relieves on the different layers may couple to each other like press studs and prevent side movements of the lamination pieces.

[0011] After completion of all the layers, the plates with the relieves are torn away in the axial direction with a proper device.

[0012] Prior art problem

[0013] The Applicant has noted that it would be preferable to avoid joining the lamination layers by coupling relieves. In fact, since the relieves are formed by partial blanking, the progressive wearing of the blanking tools may result in imprecise relieves, and this may cause inaccuracies in the coupling of the layers, creating stresses in the material, and sometimes difficulties in pressing the new pieces against the underlying formed layers.

[0014] Moreover, without proper care, removing the retaining members from inside the slots may be imprecise and / or cause damages to the material around the slots.

[0015] IT 202000003602 only partially tackles the problem of stresses by providing additional slots in the plates, allowing for some deformation.

[0016] Summary of the invention

[0017] An object of the present invention is to ensure alignment of the different layers of the lamellar pack, with the minimum impact on the process and on the final product.

[0018] This and other objects are fulfilled by a method and an apparatus for manufacturing a lamellar pack for an electric motor for automotive applications, as claimed in any of the attached claims.

[0019] The invention provides that the lamination layers are formed with a plurality of recesses formed in a main external outline portion. The well where the stack is formed has a side wall with a plurality of retaining elements, such as notches, extending in an axial direction. The recesses define together a plurality of grooves on the lamellar pack, which receive respective retaining elements. The grooves are retained by the retaining elements, such that the lamination pieces will not move in the well, especially in the radial direction.

[0020] Advantageously, alignment and prevention of movements are obtained by projections without the need of relieves, since the layers are not coupled with one another, but to the well. The recesses of the invention don’t cause stresses in the material and may well serve their purpose even tolerating some inaccuracies in the shape. Moreover, they need not a removal of material from the finished product.

[0021] Brief description of the drawings

[0022] The present invention will now be described in more detail hereinafter with reference to the accompanying drawings, in which embodiments of the invention are shown.

[0023] FIG. 1 is a schematic top view of a lamellar pack according to one embodiment of the invention, inside a well,

[0024] Fig. 2 is a schematic top view of a lamination piece of another embodiment of lamellar pack of the invention, inside a well,

[0025] FIG.s 3 is a schematic perspective view of the lamellar pack of figure 1,

[0026] FIG. 4 is a schematic side view of an apparatus for manufacturing lamellar packs according to one embodiment of the invention,

[0027] FIG. 5 is a schematic perspective partial section view of a well of the apparatus of FIG. 4, and

[0028] FIG.s 6 and 6b are schematic top views of two lamellar packs according to other embodiments of the invention.

[0029] Detailed description

[0030] An object of the invention is a method of manufacturing a lamellar pack 1 for an electric motor for automotive applications.

[0031] It is also an object of the invention an apparatus 100 configured to manufacture the lamellar pack by the mentioned method, mainly shown in figure 4.

[0032] A step of the method is blanking a plurality of ferromagnetic lamination pieces 2 from a lamination board 3.

[0033] In a known manner, the lamination board 3 may be supplied by unwinding from a spool 110 of the apparatus 100. Preferably, one or more adhesive dispensers (not shown) are configured to apply an adhesive on one or more predetermined portions of the lamination board 3, for subsequent bonding of the lamination pieces 2 in the lamellar pack. Then, the apparatus 100 comprises one or more punches 120, configured to blank the lamination pieces 2 from the lamination board 2.

[0034] The lamination pieces 2 are filled into a well 130 of the apparatus 100. In the preferred embodiment, the well 130 is arranged below a punch 120, such that the punch 120 pushes the lamination pieces 2 directly into the well 130. In more detail, a cutting matrix is arranged above the well 130, and the lamination pieces 2 are cut by being pressed through the cutting matrix by the punch 120.

[0035] However, in other embodiments the well 130 could be spaced apart from the punch 120 and receive the lamination pieces 2 by other filling means known to the skilled person.

[0036] The well 130 has a bottom wall 131 and a side wall 132, projecting from the bottom wall 131 in an axial direction X-X. The lamination pieces 2 are progressively received in the well 130 such as to form a plurality of lamination layers 4. Each lamination layer 4 can be formed by just one lamination piece 2, as shown in figures 1 and 3, or by a plurality of lamination pieces 2 arranged side by side, as in figures 2 and 6a-6b. In this case, the proper positioning of the lamination pieces 2 may be obtained by rotating the well 130 between receiving successive lamination pieces 2.

[0037] In a known manner, each lamination layer 4 may have a central aperture 43, extending around a central axis of the lamination layer 4 extending in the axial direction X-X, which will be also the central axis of the lamellar pack. The apertures 43 of the layers 4 may define, when stacked, a through channel, which can be, depending on the use of the lamellar pack, a through stator channel to receive a rotor, or a through rotor channel to receive a shaft. Preferably, the through channel remains empty while the lamellar pack 1 is inside the well 130, and in particular the well 130 is free of alignment elements inside the through channel.

[0038] Moreover, each lamination layer 4 may have a plurality of through slots 44, only shown in figure 2. The slots 44 of the layers 4, when stacked, may receive conductive windings and / or permanent magnets. Preferably, the slots 44 are open toward the central aperture 43. In other embodiments, they may be open toward the main external outline portion 41, or they may be closed between the main external outline portion 41 and the central aperture 43.

[0039] With the repeated and progressive filling of the lamination pieces 2, plural lamination layers 4 are formed and stacked upon each other in the axial direction X-X. When the desired number of lamination layers 4 is completed, a lamellar pack 1 is formed, embodiments of which are shown in figures 1, 3 and 6a-6b. The invention provides that the lamination pieces 2 are given predetermined shapes, such that each lamination layer 4 comprises a main external outline portion 41 and a plurality of recesses 42 formed in the main external outline portion 41. Thus, the punch 120 and matrix should have an appropriate shape to form the recesses 42. Preferably, the main external outline portion 41 is rounded, in particular circular, and the recesses 42 penetrate radially therein, that is they extend toward the central axis.

[0040] In more detail, the recesses 42 of a lamination layer 4 are distributed along a circumferential direction around the central axis of the lamellar pack la.

[0041] In case the lamination layer 4 is formed by plural lamination pieces 2, preferably each lamination piece 2 comprises at least one recess 42, more preferably plural recesses 42. As apparent from the following details, this ensures proper alignment and retaining not only of a lamination layer 4 as a whole, but of all the lamination pieces 2 thereof.

[0042] With the overlaying and alignment of the lamination layers 4, the main external outline portions 41 of the layers 4 define an outer surface of the lamellar pack la. Moreover, the recesses 42 of different layers 4 are aligned and define together, on the outer surface, a plurality of grooves extending in the axial direction X-X.

[0043] The well 130 has a plurality of retaining elements 133 projecting from the side wall 132 and extending along the axial direction X-X, as shown in figure 5. The recesses 42 (preferably all of them) receive respective retaining elements 133.

[0044] Each retaining element 133 is configured to retain a respective groove to prevent movement of the lamination pieces 2 in the well 130, in particular in the radial direction. Thus, the retaining elements 133 and the recesses 42 are shaped such that the retaining elements 133 are irremovable from the grooves in the radial direction. Instead, they can be insertable and removable in the axial direction X-X.

[0045] In order for their coupling, the recesses 42 of the lamination pieces 2 are aligned with the retaining elements 133, while filling the lamination pieces 2 into the well 130.

[0046] Preferably, each retaining element 133 is a notch. In more detail, each retaining element 133 may have a head portion 1332 and a neck portion 1331, best visible in figure 2. The neck portion 1331 connects the head portion 1332 to the side wall 132.

[0047] The head portion 1332 projects circumferentially from the neck portion 1331 on at least one side thereof. Thus, a recess is defined between the head portion 1332 and the side wall 132, penetrating toward the neck portion 1331 in the circumferential direction.

[0048] Preferably, each retaining element 133 has a dovetail shape, and therefore the head portion 1332 circumferentially projects from the neck portion 1331 on both sides, and two opposite recesses are defined between the head portion 1332 and the side wall 132, on opposite sides of the neck portion 1331. Thus, the neck portion 1331 will be thinner than the head portion 1332.

[0049] In these embodiments, each groove is delimited, on at least one side, by a retaining edge, in particular a groove edge, penetrating between the side wall 132 of the well 130 and the head portion 1332 of a respective retaining element 133 defining the respective notch, toward its neck portion 1331. Preferably, each groove 42 has two retaining edges on opposite sides. The one or two retaining edges define a narrowed access to the groove, where the neck portions 1331 are received, while an enlarged bottom of the groove receives the head portions 1332. It is to be noted that the lamellar pack and its layers 4 may comprise its own projections 45. For example, as shown in figure 6, these projections 45 may define ears having holes for fitting the lamellar pack onto rod structures, during use. In some embodiments, the recesses 42 defining the grooves may be formed in these projections 45, namely in the ears.

Claims

CLAIMS1. A method of manufacturing a lamellar pack for an electric motor for automotive applications, comprising:- blanking a plurality of lamination pieces (2) from a lamination board (3),- filling the lamination pieces (2) into a well (130) having a bottom wall (131) and a side wall (132), such that the lamination pieces (2) form in the well (130) a lamellar pack (1) with a plurality of annular lamination layers (4) stacked upon each other in an axial direction (X-X), each lamination layer (4) being made in a single lamination piece (2) or in plural lamination pieces (2) arranged side by side, characterized in that:- each lamination layer (4) comprises a main external outline portion (41) and a plurality of recesses (42) formed in the main external outline portion (41),- the recesses (42) of different lamination layers (4) are aligned in the axial direction (X- X) and define together a plurality of grooves on an outer surface of the lamellar pack (1),- the well (130) has a plurality of retaining elements (133), projecting from the side wall (132) and extending along the axial direction (X-X), each retaining element (133) being configured to retain a respective groove to prevent movement of the lamination pieces (2) in the well (130).

2. The method of claim 1, wherein each retaining element (133) is configured to retain a respective groove in a radial direction extending toward a central axis of the lamellar pack (1).

3. The method of claim 1 or 2, wherein:- each retaining element (133) has a neck portion (1331) and a head portion (1332) projecting circumferentially from the neck portion (1331), preferably each retaining element (133) having a dovetail shape,- each groove (42) is delimited on at least one side by a retaining edge penetrating between the side wall (123) of the well (130) and the head portion (1332) of a respective retaining element (133).

4. The method of any claim 1-3, wherein each groove (42) is a a groove with a narrowed access.

5. The method of any claim 1-4, wherein the recesses (42) of a lamination layer (4) are distributed along a circumferential direction around a central axis of the lamellar pack (1).

6. The method of any claim 1-5, wherein each lamination layer (4) comprises one or more lamination pieces (2), each lamination piece (2) having one or more recess (42).

7. The method of any claim 1-6, wherein filling the lamination pieces (2) into the well (130) comprises aligning the recesses (42) with the retaining elements (133).

8. The method of any claim 1-7, wherein blanking the lamination pieces (2) and filling the lamination pieces (2) into the well (130) comprises repeatedly pressing the lamination board (3) by a punch (120), through a matrix above the well (130), such that the lamination pieces (2) are blanked by the punch (120) and the matrix, and pressed into the well (130) by the punch (120).

9. An apparatus (100) for manufacturing a lamellar pack for an electric motor for automotive applications, comprising:- one or more punches (120) configured to blank a plurality of lamination pieces (2) from a lamination board (3),- a well (130) having a bottom wall (131) and a side wall (132), the well (130) being configured to receive the lamination pieces (2), such that the lamination pieces (2) form in the well (130) a lamellar pack (1) with a plurality of lamination layers (4) stacked upon each other in an axial direction (X-X), characterized in that:- the one or more punches (120) are configured to blank the lamination pieces (2) with predetermined shapes, such that each lamination layer (4) has a main external outline portion (41) and a plurality of recesses (42) formed in the main external outline portion (41),- the side wall (132) of the well (130) has a plurality of retaining elements (133) extending along the axial direction (X-X), each retaining element (133) being configured to retain a respective groove, defined on an outer surface of the lamellar pack (1) byrecesses (42) of different lamination layers (4) aligned in the axial direction (X-X), to prevent movement of the lamination pieces (2) in the well (130).

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