A method and an apparatus for manufacturing a lamellar pack

Abstract

A method of manufacturing a lamellar pack for an electric motor for automotive applications comprises blanking lamination pieces (2) and filling the lamination pieces (2) into a well (130), such that the lamination pieces (2) form a semi-finished lamellar pack (1) with lamination layers (4) stacked upon each other in an axial direction (X-X) The lamination layers (4) comprise projections (42), defining together notches on an outer surface of the semi-finished lamellar pack (1), preferably being dovetail shaped. A side wall (132) of the well (130) has retaining elements (133) extending along the axial direction (X-X), such as grooves with a narrowed access. Each retaining element (133) is configured to retain a respective notch to prevent movement of the lamination pieces (2) in the well (130), especially in a radial direction, to prevent their fall in the middle of the well (130). The notches are then removed from the semi-finished lamellar pack (1).

Description

[0001] Title: “A method and an apparatus for manufacturing a lamellar pack”

[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. of the invention

[0005] 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.

[0006] 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.

[0007] 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. 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.

[0008] 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.

[0009] 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.

[0010] After completion of all the layers, the plates with the relieves are torn away in the axial direction with a proper device.

[0011] Prior art problem

[0012] 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.

[0013] 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.

[0014] IT 202000003602 only partially tackles the problem of stresses by providing additional slots in the plates, allowing for some deformation.

[0015] Summary of the invention

[0016] 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.

[0017] 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.

[0018] The invention provides that the lamination layers are formed with a plurality of projections projecting from a main external outline portion. The well where the stack is formed has a side wall with a plurality of retaining elements, such as grooves, extending in an axial direction. The projections define together a plurality of notches on the semifinished lamellar pack, which are received along respective retaining elements. The notches are retained by the retaining elements, such that the lamination pieces will not move in the well, especially in the radial direction. After completion of the lamination layers, the notches are removed, such as by severing neck portions of the projections.

[0019] 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 projections of the invention don’t cause stresses in the material and may well serve their purpose even tolerating some inaccuracies in the shape. Moreover, the projections are formed in a position where removal is easy, and the finished product will be free of excess parts serving only the purpose of alignment.

[0020] 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.

[0021] FIG. 1 is a schematic top view of a semi-finished lamellar pack according to one embodiment of the invention, inside a well,

[0022] Fig. 2 is a schematic top view of a lamination piece of another embodiment of semi-finished lamellar pack of the invention, inside a well,

[0023] FIG.s 3 a and 3 b are schematic perspective views of the semi-finished lamellar pack of figure 1 , while removing its notches in two alternative manners,

[0024] FIG. 4 is a schematic side view of an apparatus for manufacturing lamellar packs according to one embodiment of the invention,

[0025] FIG. 5 is a schematic perspective partial section view of a well of the apparatus of FIG. 4,

[0026] FIG.s 6 and 6b are schematic top views of two semi-finished lamellar packs according to other embodiments of the invention, and FIG. 7 is a schematic top view of a lamination piece for another embodiment of a semi-finished lamellar pack according to the invention.

[0027] Detailed description

[0028] An object of the invention is a method of manufacturing a lamellar pack for an electric motor for automotive applications. In the drawings, a semi-finished lamellar pack 1 is mainly represented, having some features that is going to be removed to obtain the final lamellar pack.

[0029] 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.

[0030] A step of the method is blanking a plurality of ferromagnetic lamination pieces 2 from a lamination board 3.

[0031] 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.

[0032] 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.

[0033] 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.

[0034] 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 3a-3b, 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.

[0035] 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 semi-finished lamellar pack 1 is inside the well 130, and in particular the well 130 is free of alignment elements inside the through channel.

[0036] 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.

[0037] 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 semi-finished lamellar pack 1 is formed, embodiments of which are shown in figures 1, 3a-3b and 6a-6b.

[0038] 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 projections 42 projecting from the main external outline portion 41. Thus, the punch 120 and matrix should have an appropriate shape to form the projections 42. Preferably, the main external outline portion 41 is rounded, in particular circular, and the projections 42 project radially therefrom, that is they project away from the central axis.

[0039] In more detail, the projections 42 of a lamination layer 4 are distributed along a circumferential direction around the central axis of the semi-finished lamellar pack 1.

[0040] In case the lamination layer 4 is formed by plural lamination pieces 2, preferably each lamination piece 2 comprises at least one projection 42, more preferably plural projections 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.

[0041] 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 semi-finished stack 1. Moreover, the projections 42 of different layers 4 are aligned and define together, on the outer surface, a plurality of notches extending in the axial direction X-X.

[0042] The side wall 132 of the well 130 has a plurality of retaining elements 133 extending along the axial direction X-X, as shown in figure 5. The projections 42 (preferably all of them) are received along respective retaining elements 133, preferably within the retaining elements 133.

[0043] Each retaining element 133 is configured to retain a respective notch 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 projections 42 are shaped such that the notches are irremovable from the retaining elements 133 in the radial direction. Instead, they can be insertable and removable in the axial direction X-X.

[0044] In order for their coupling, the projections 42 of the lamination pieces 2 are aligned with the retaining elements 133, while filling the lamination pieces 2 into the well 130.

[0045] In detail, each projection 42 may have a head portion 421 and a neck portion 422, best visible in figure 2. The neck portion 422 connects the head portion 421 to the main external outline portion 41.

[0046] The head portion 421 projects circumferentially from the neck portion 422 on at least one side thereof. Thus, a recess is defined between the head portion 421 and the main external outline portion 41, penetrating toward the neck portion 422 in the circumferential direction. Preferably, each projection 421 has a dovetail shape, and therefore the head portion 42 circumferentially projects from the neck portion 422 on both sides, and two opposite recesses are defined between the head portion 421 and the main external outline portion 41, on opposite sides of the neck portion 422. Thus, the neck portion 422 will be thinner than the head portion 421.

[0047] In these embodiments, each retaining element 133 has a retaining edge, in particular a groove edge, penetrating between the main external outline portion 41 and the head portions 421 of the projections 42 defining the respective notch, toward the neck portions 422. Preferably, each retaining element 133 has two retaining edges on opposite sides of the projections 42. The one or two retaining edges define a narrowed access to the groove, where the neck portions 422 are received, while an enlarged bottom of the groove receives the head portions 421.

[0048] The method comprises obtaining the finished lamellar pack by removing the notches from the semi-finished lamellar pack 1. Preferably, removing the notches comprises severing each notch along the neck portions 422 of the projections 42 that form the notch. This severing can be performed by any suitable removing means of the apparatus 100.

[0049] Preferably, the removing means comprise one or more removing blocks 140, which are arranged along the outer surface of the semi-finished lamellar pack 1 in at least one use condition. Moreover, the removing means comprise moving means (not shown) connected to each block 140 and / or to the semi-finished lamellar pack 1 and / or to the well 130. The moving means are configured to impart a relative movement between the one or more removing blocks 140 and the outer surface of the semi-finished lamellar pack 1, along each other. In particular, the moving means may move the one or more removing blocks 140 along the outer surface, while the lamellar pack 1 is kept fixed, or vice-versa.

[0050] In one embodiment, as shown in figure 3 a, each removing block 140 can be a blade. Each bade 140 is preferably sloped to the axial direction X-X, to progressively cut the notch while moving along the outer surface. For example, the blade 140 may be movable in the axial direction X-X, or may be movable in the circumferential direction.

[0051] Each blade 140 can be a planar blade or a curved blade, with a curved profile matching the outer surface.

[0052] In another embodiment, shown in figure 3b, each removing block 140 may be a block free of blades. The block may extend along the axial direction X-X to bear against a corresponding notch throughout its length, in particular against the neck portions 422 of the projections 42. The block may be movable in the circumferential direction relative to the outer surface (or the other way round) to press the relative notch, cause its deformation along the neck portions 422, and finally tear it off. Thus, the notches will bend and detach when an elongation of their neck portions 422 reaches an elongation at break value.

[0053] Severing the notches may cause a small amount of material of the notch to remain as a small irregularity on the outer surface. In order to prevent that such irregularities project beyond the overall shape of the outer surface, in some embodiments, like for the lamination piece 2 of figure 7, each lamination layer 4 may comprise recesses 46, penetrating toward the central axis on the sides of the projections 42, in particular on the sides of the neck portions 422. Preferably, the recesses 46 delimit a thinnest part of the neck portions 422. Thus, the neck portions 422 will tear between the recesses 46, and any remaining irregularity will not project radially beyond an access of the recesses 46.

[0054] It is to be noted that, in some embodiments, the removing blocks 140 need not be in the same number as the notches. For example, a single removing block 140 could be moved along the outer surface (of vice-versa) while successively reaching and severing distinct notches, as shown in figure 3b.

[0055] Each removing block 140 can be arranged inside or outside the well 130. In case the removing block 140 is inside the well 130 and the well 130 is below the punch 120, a circumferential movement of each removing block 140 is preferred, to comply with the small space requirements.

[0056] It is to be noted that, further to the described projections 42 provided for alignment and retainment, the lamellar pack and its layers 4 may comprise further projections 45, intended for different purposes, which are not removed but remains in the finished lamellar pack. For example, as shown in figure 6, the further projections 45 may define ears having holes for fitting the lamellar pack onto rod structures, during use. In some embodiments, the projections 42 defining the notches may project from the further projections 45, namely from 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 semi-finished lamellar pack (1) with a plurality of lamination layers (4) stacked upon each other in an axial direction (X-X), characterized in that:- each lamination layer (4) comprises a main external outline portion (41) and a plurality of projections (42) projecting from the main external outline portion (41),- the projections (42) of different lamination layers (4) are aligned in the axial direction (X-X) and define together a plurality of notches on an outer surface of the semi-finished lamellar pack (1),- 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 notch to prevent movement of the lamination pieces (2) in the well (130),- the method comprises removing the notches from the semi-finished lamellar pack (1).

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

3. The method of claim 1 or 2, wherein:- each projection (42) has a neck portion (422) and a head portion (421) projecting circumferentially from the neck portion (422), preferably each projection (42) having a dovetail shape,- each retaining element (133) has a retaining edge penetrating between the main external outline portion (41) and the head portions (421) of the projections (42) defining the respective notch.

4. The method of claim 3, wherein removing the notches comprises severing each notch along the neck portions (422) of the projections (42) thereof.

5. The method of any claim 1-4, wherein each retaining element (133) is a groove formed in a thickness of the side wall (132), preferably a groove with a narrowed access.

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

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

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 semi-finished 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 projections (42) projecting from 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 notch, defined on an outer surface of the semi-finished lamellar pack (1) by projections (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), - removing means configured to remove the notches from the semi-finished lamellar pack (1).

10. An apparatus (100) as claimed in claim 9, wherein the removing means comprise one or more removing blocks (140), and moving means configured to impart a relative movement between the one or more removing blocks (140) and the outer surface of the semi-finished lamellar pack (1) along each other, optionally the removing blocks (140) comprising sloped blades.

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