US-12620858-B2 - Electric machine stator with foldable insulating elements, and method for manufacturing such a stator

US12620858B2US 12620858 B2US12620858 B2US 12620858B2US-12620858-B2

Abstract

An electric machine stator has a core of ferromagnetic material, consisting of teeth arranged around a longitudinal axis and defining a plurality of slots; the stator has, for each tooth, an insulating cap fixed to a longitudinal end thereof via an interference coupling and provided with front projections, spaced apart from one another in a radial direction; the windings, which are made of electrically conductive material, extend in the half-slots on opposite sides of each tooth and around the cap, and radially between the front projections; each half-slot carries at least one sheet of foldable insulating material, which has a C-shaped portion, interposed between the first wire portions and the tooth, and at least one flap, longitudinally projecting from the C-shaped portion out of the corresponding half-slot and radially resting on an end portion of one of the front projections.

Inventors

Davide Ferrara
Paolo FAVERZANI
Luca Poggio

Assignees

FERRARI S.P.A.

Dates

Publication Date: 20260505
Application Date: 20230907
Priority Date: 20220912

Claims (13)

1 . An electric machine stator, comprising a core of ferromagnetic material, consisting of a plurality of teeth arranged around a longitudinal axis and defining a plurality of slots between them, along a circumferential direction; the stator comprising, for each tooth: two half-slots, on opposite sides of the tooth along said circumferential direction; two insulating elements, each comprising a) a covering portion longitudinally resting against a corresponding longitudinal end of said tooth, and b) an attachment portion, which is made of a plastic material and is coupled to said longitudinal end in a fixed position; for each half-slot, a respective sheet of foldable insulating material comprising a C-shaped portion housed in the corresponding half-slot; at least one winding, which is made of an electrically conductive material, is wound around said C-shaped portions and around said insulating elements and comprises: c) first wire portions arranged in said half-slots, and d) second wire portions arranged around said insulating elements; wherein each attachment portion is directly coupled to the corresponding longitudinal end of the tooth, without interposition of any part of said sheets, wherein, at said half-slots, said longitudinal ends have side surfaces with recesses, and wherein said attachment portions engage said recesses.
2 . The stator according to claim 1 , wherein said attachment portion is interposed between said C-shaped portions and the longitudinal end of the tooth.
3 . The stator according to claim 2 , wherein said C-shaped portion directly rests on said attachment portion.
4 . The stator according to claim 1 , wherein each attachment portion consists of two connecting walls, which longitudinally project from said covering portion into respective half-slots and are arranged on opposite sides of the corresponding tooth along said circumferential direction.
5 . The stator according to claim 4 , wherein said connecting walls are shaped with the same C-shaped profile as the surface of said half-slots.
6 . The stator according to claim 4 , wherein each connecting wall consist of an intermediate rib and of two wings, which project from respective edges of said intermediate rib.
7 . The stator according to claim 1 , wherein said attachment portions are enclosed in said recesses.
8 . The stator according to claim 7 , wherein each attachment portion is flush with the surface of said half-slots.
9 . The stator according to claim 3 , wherein each insulating element further comprises at least one front projection projecting from said covering portion as a longitudinal extension of a wing of said attachment portion; and wherein each sheet comprises at least one flap, which longitudinally projects from a portion of said C-shaped portion and is radially arranged on said front projection.
10 . The stator according to claim 9 , wherein said flap has a length that is such as to cover the entire longitudinal width of said front projection.
11 . The stator according to claim 9 , wherein the C-shaped portion of each sheet comprises: an intermediate strip arranged in front of a face of the corresponding half-slot, along said circumferential direction, and two strips, which define respective folding lines with said intermediate strip and are arranged, in a radial direction, in front of respective further faces of the corresponding half-slot; said flap defining a longitudinal extension of one of said two strips.
12 . The stator according to claim 9 , wherein each sheet is provided with said flap at its opposite longitudinal ends.
13 . The stator according to claim 9 , wherein each sheet further comprises at least one foldable wing, which separates windings arranged in the same slot and defines a folding line with said C-shaped portion and said flap.

Description

CROSS-REFERENCE TO RELATED APPLICATIONS This patent application claims priority from Italian patent application no. 102022000018504 filed on Sep. 12, 2022, the entire disclosure of which is incorporated herein by reference. TECHNICAL FIELD The invention relates to an electric machine stator provided with insulation sheets arranged around the copper windings in order to insulate them from the iron core. PRIOR ART As it is known, an electric machine stator has an iron core, which can consist of a plurality of teeth, which define, in a circumferential direction, a series of stator slots between them. The copper windings, which extend in the slots around the teeth, must be electrically insulated from the adjacent windings and from the iron of the core. In order to obtain this insulation, a folded sheet made of an insulating paper material, also known as “insulation paper”, is used. In detail, at the slots, the side surfaces of each tooth are covered by respective strips of said insulation papers. The insulation papers directly rest on the tooth and can be directly locked by the winding or they can be fixed by means of two insulating elements, also known as “caps”, coupled to the opposite axial ends of the tooth in fixed positions. At the same time, at the opposite axial ends of the tooth, the windings are arranged around the outer surfaces of the two caps, which, hence, serve as electrical insulation from the iron of the core. In these known solutions, the position and the coupling modes of the insulation papers are scarcely satisfactory, since the caps must be relatively large-sized and have relatively wide tolerances in order to take into account the thickness of the papers to be locked against the respective teeth. On the contrary, the dimensions and the tolerances of the caps should be reduced, even by a few tenths of millimetre, in order to limit the overall size of the caps and make better use of this reduction in size to increase the space available for copper windings, to the full advantage of the efficiency of the electric machine. Furthermore, in known solutions, the operations to be carried out to couple the caps to the axial ends of the teeth must be performed with particular care, in order to prevent the insulation paper from moving relative to the designed position, maybe even creasing and breaking, with consequent possible faults in the insulation of the windings. Therefore, because of these problems, the ways in which the insulation papers and the caps are positioned and/or coupled relative to the teeth should be changed and/or simplified. JP2016036223 discloses plastic material caps arranged on the axial ends of the teeth. Each one of the caps has a pair of axial projections, which radially face part of the tooth so as to define respective slits, which are engaged by an edge of the insulation paper. SUMMARY OF THE INVENTION The object of the invention is to provide an electric machine stator capable of solving the drawbacks discussed above in a simple and economic fashion. According to the present invention, there is provided an electric machine stator as claimed in claim 1. Preferred embodiments of the invention are defined in the appended dependent claims. BRIEF DESCRIPTION OF THE DRAWINGS The invention will now be described with reference to the accompanying drawings showing a non-limiting embodiment, wherein: FIG. 1 is a perspective view of a preferred embodiment of the electric machine stator according to the invention; FIG. 2 shows part of the stator in a cross section; FIG. 3 shows, from a different point of view, a detail of the stator of FIG. 1; FIGS. 4 and 5 show the detail of FIG. 2, with parts removed for greater clarity; FIGS. 6 and 7 show, on a larger scale and from different points of view, two details of the detail of FIGS. 3-5; and FIG. 8 is similar to FIG. 5 and shows a variant of the invention, with an exploded view. DETAILED DESCRIPTION OF PREFERRED EMBODIMENTS OF THE INVENTION In FIG. 1, reference number 1 indicates a stator of an electric machine suited to be used as motor-generator for driving motor vehicles. Anyway, it can be used as generator and/or in other applications. The stator 1 extends along a longitudinal axis A and comprises a core 2 made of a ferromagnetic material, for instance iron. The core 2 consists of a plurality of teeth 3, which are arranged next to one another, with continuity, along a circumferential direction B around the axis A and, as shown in FIG. 2, define a series of slots 4 between them, along said direction B. The slots 4 and the teeth 3 extend parallel to the axis A and have respective cross sections with a constant area and shape along the axis A. Therefore, each tooth 3 defines two half-slots 4a, which are parallel to one another along the direction B, and comprises: a radially outer portion 6, a radially inner portion 7 and an intermediate portion 8, which is narrower along the direction B. In particular, along the direction B, the portio