FR3157975A1 - AXIAL STACK OF METAL PLATES FOR AN ELECTRIC MACHINE ROTOR - Google Patents

Abstract

The invention relates to an axial stack of metal plates (14) along the X axis for an electric machine rotor, said stack comprising axial fixing members (22), said plates (14) being immobilized transversely relative to the X axis by means of said members (22) passing through passages (24) for said members (24) formed in said plates (14), a cross-section of said members (22) having a surface area smaller than a surface area of a cross-section of said passages (24), the cross-section of each passage (24) in at least one of the plates being delimited by a profile (P) configured to immobilize each member (22) transversely in said passage (24), in order to prevent bending of said members (22) through said passages (24). Figure for abstract: Figure 4

Description

AXIAL STACK OF METAL PLATES FOR AN ELECTRIC MACHINE ROTOR Technical field of the invention

The invention relates to an axial stack of metal plates for an electric machine rotor, an electric machine rotor comprising such a stack, and an electric machine comprising such a rotor.

Technical background

An electric motor has a rotor mounted to rotate in a stator. The rotor is generally made in the form of so-called "laminated" sheets, that is to say in the form of an axial stack of plates.

The plates must be held axially against each other within the stack. For this purpose, axial fixing members pass through passages formed in the plates.

For the sake of compactness, and to avoid having additional openings in the plates which might disturb the radial orientation of the magnetic flux lines, the passages are conventionally combined with oblong slots used to guide the flux radially.

As a result, the passages are necessarily of a size significantly larger than that of the fastening members. As a result, during assembly of the rotor and assembly of the metal plates, the axial fastening members are, at best, only retained in the passages radially outwards, but are not retained in these passages either tangentially or radially inwards. Since the fastening members are susceptible to tangential and radial movements towards the inside of the rotor through the passages, there is therefore a high risk of bending of these fastening members through these passages during assembly of the plates and during operation of the rotor.

There is therefore a real need for a stack of metal plates which allows both to provide adequate orientation of the magnetic flux and to ensure optimal support of the fixing members in the passages in the radial and tangential directions.

The invention meets this need by proposing plates having particular passages capable of immobilizing the fixing members in these passages.

For this purpose, the invention proposes an axial stack of X axis of metal plates for an electric machine rotor, said stack further comprising axial fixing members, said plates being immobilized transversely with respect to the X axis by means of the fixing members passing through passages for said members formed in said plates, a cross section of said members having a surface area less than a surface area of a cross section of said passages, the section of each passage in at least one of the plates being delimited by a profile configured to immobilize transversely each member in said passage, in order to avoid bending of said members through said passages.

The use of a specific profile for each passage of at least one of the plates of the stack makes it possible to immobilize transversely - that is to say radially and tangentially - the fixing member in this passage, and thus limits the risk of bending of this member since it is maintained in all transverse directions, at least at the level of this plate of the stack.

The conformation of the passages according to a particular profile makes it possible to dispense with additional holding elements and ensures satisfactory holding of the fixing members solely due to the particular cutting of the passages in the plate(s) chosen for this purpose. In other words, said passages do not only serve to allow said fixing members to pass through but also to hold them, while offering the function(s) linked to their large section, greater than the section of said fixing members, starting with a reduction in the weight of said stack.

According to other characteristics of the invention:

- the section of each passage is delimited by said profile for all the plates,

- the profile of each passage comprises an outer radial end edge matching a first part of an external surface of each member and two intermediate opposite edges, at least one of said intermediate edges comprising a lug projecting towards the inside of the passage and capable of immobilizing a second part of the external surface of each member,

- the outer radial end edge and said at least one lug delimit a first subsection of the passage open between said at least one lug and the opposite intermediate edge,

- each intermediate edge has a said lug, said lugs being tangentially opposite each other.

- each organ is cylindrical,

- walls of the outer radial end edge and the lugs in contact with said member have the same radius of curvature as said member,

- the remainder of the passage determines a second subsection adjoining the first subsection and also open between the two lugs,

- an area of the second subsection is greater than that of the first subsection,

- an inner radial end edge of the second subsection has a radius of curvature greater than the radius of curvature of said member,

- the section of the passage has the shape of an 8,

- each plate has a series of oblong lights of radial orientation distributed angularly in a regular manner around the X axis,

- said lights are configured to radially orient the magnetic flux lines in said rotor,

- each passage consists of one of said oblong lights,

- the oblong lumens forming organ passages alternate angularly with the oblong lumens devoid of organs,

- rectilinear oblong openings of radial orientation distributed angularly in a regular manner around the X axis and forming passages for flow-generating organs alternate angularly with the oblong lights,

- the magnetic flux generating organs are permanent magnets or windings,

- the fixing elements are rivets.

The invention also relates to an X-axis electric machine rotor comprising a stack of plates of the type described above.

Advantageously, an electric machine rotor equipped with such a stack of plates guarantees high operational reliability through the immobilization of the fixing members and optimal efficiency through the function(s) offered by the large section passages.

According to another characteristic of the rotor, the latter comprises two end plates arranged axially on either side of said stack, said plates holding the plates clamped in the stack and being fixed to the ends of the axial fixing members.

The invention finally relates to an electric machine comprising a rotor of the type described above.

Brief description of the figures

Other characteristics and advantages of the invention will appear during the reading of the detailed description which follows for the understanding of which reference will be made to the appended drawings in which:

FIG. 1 There FIG. 1 is a side view of a rotor of an electric machine known from the state of the art;

FIG. 2 There FIG. 2 is a perspective view of an end plate and fixing members of the rotor of a state-of-the-art electric machine;

FIG. 3 There FIG. 3 is a cross-sectional view of a first embodiment of a plate stack for an electric machine rotor according to the invention;

FIG. 4 There FIG. 4 is a cross-sectional view of a second embodiment of a plate stack for an electric machine rotor according to the invention.

Detailed description of the invention

We represented at the FIG. 1 an electric machine rotor 10 according to the invention. The electric machine rotor 10 and its components will be described with reference to the trihedron directions "X", "R", "T", where "X" denotes the axial direction, "R" denotes the radial transverse direction and "T" denotes the tangential transverse direction.

The rotor 10 is intended to cooperate electromagnetically with a stator of an electrical machine (not shown). The rotor 10 is an X-axis rotor comprising a body formed from a stack 12 of metal plates 14. Such a rotor is made up of the stack of metal plates and makes it possible to form a magnetic flux inside while reducing the heating of the magnetic circuit, this heating being caused by eddy current losses. The plates are linked in rotation to an axis 16 of the rotor. The rotor 10 comprises two end flanges 18 which are arranged axially on either side of the stack 12. The flanges 18 keep the plates 14 clamped along the X axis in the stack 12 and they are fixed to ends 20 of axial fixing members 22 which pass through the plates 14. On the FIG. 1 , the axial fixing members 22 which have been shown are screws, the opposite ends 20 of which comprise screw heads and nuts, but it will be understood that this arrangement is not limiting of the invention, and that the fixing members could be other than screws, as will be seen in the remainder of this description. The rotor 10 is fixedly connected to a rotor shaft 16 by shrink fitting.

As illustrated by the FIG. 3 , the axial fixing members 22 pass through passages 24 for these members which are formed in the plates 14.

It may occur, as illustrated in Figures 3 and 4, that a cross-section of the members 22 has a surface area less than a surface area of a cross-section of the passages 24.

This is particularly the case when the passages 24 do not have the sole function of allowing the passage of the members 22, but also have another function, starting with a reduction in weight. In addition, the plates 14 of a stack of plates 12 of a rotor 10 may comprise a series of oblong slots of radial orientation distributed angularly in a regular manner around the axis X. These slots are in particular configured so that the metallic material remaining around these slots makes it possible to radially orient the magnetic flux lines in the rotor 10.

In this respect, it will be understood that any additional cutout made in the plates 14 may modify the orientation of the magnetic flux lines in an undesired manner. This is why, preferably, it is desirable that the axial fixing members 22 do not pass through specific holes but pass through the oblong slots 24, that is to say in other words that at least a part of the oblong slots also forms the passages 24 for the fixing members 22. This makes it possible to avoid modifying the orientation of the flux lines in the plates 14. In the remainder of the description, the slots and the passages will be described under the same reference 24, for simplification.

The shape of the passages 24 here falls within a substantially elongated oval shape which is dictated by compliance with the radial orientation along the direction R of the flow lines in the rotor. As a result, it can only be slightly modified so as not to affect the performance of the rotor.

On the FIG. 3 , the organs 22 are generally immobilized along the radial direction R, from the inside to the outside by a radially external part of the passages.

To the FIG. 2 , fastening members 22 are shown in the form of rivets, initially fixed to two end plates 18 in a state-of-the-art rotor. The rivets 22 are pressed in the axial direction during the riveting process, which leads to a risk of bending of the rivets. The bending of the rivets 22 through the passages 24 led to a breakage of a part of the ends 20 of the fastening members 22 and to the separation of one of the two end plates 18. This configuration is not acceptable because it is synonymous with destruction of the rotor 10 and therefore of the electrical machine equipped therewith.

To overcome this drawback, the invention proposes plates 14 having passages 24 capable of holding the fixing members 22 in these passages 24.

For this purpose, as illustrated in Figures 3 and 4, the section of each passage 24 in at least one of the plates 14 is delimited by a profile P which is configured to immobilize transversely each member 22 in the passage 24. This configuration advantageously makes it possible, by maintaining the members 22 in the passages 24 of this plate 14, to limit the risks of bending of these members 22 through the passages 24.

More particularly, as illustrated in Figures 3 and 4, the profile P of each passage 24 of the plate 14 firstly comprises an outer radial end edge 26 which matches a first part 28 of an external surface of each member 22. This edge 26 makes it possible, as described previously, to radially immobilize the members 22 in the direction R, from the inside to the outside of the plate 14.

The profile P further comprises two intermediate opposite edges 30, 32. At least one of the intermediate opposite edges 30, 32 comprises a lug 34, 36 projecting towards the inside of the passage 24. This lug 34, 36 is capable of immobilizing a second corresponding part 38 of the external surface of each member 22. This lug 34, 36 delimits a first subsection 25 of the passage P which is open between the lug 34, 36 and the opposite intermediate edge 32, 30, and which receives the entire section of the member 22.

In practice, each of the opposite edges 30, 32 has a respective lug 32, 34 projecting towards the inside of the passage 24, the lugs 32, 34 being tangentially opposite. The lugs 34, 36 immobilize a second corresponding part 38 of the external surface of each member 22. The lugs 34, 36 delimit the first subsection 25 of the passage P which is open between the lug 34, 36 and the opposite lug 36, 34.

In this case, the second corresponding part 38 of the external surface of each member 22 comprises more precisely two sub-parts 38a, 38b which are substantially radially opposite to the part 28 of the external surface of the member 22 associated with the outer radial end edge 26 of the passage 24. In this way, the cooperation of the lugs 34, 36 with the two sub-parts 38a, 38b makes it possible to immobilize the member 22 in the radial direction R from the outside to the inside and also in the tangential direction T. As a result, the member 22 is immobilized in all directions by the passage 24 of the plate 14 and therefore generally in all transverse directions relative to the rotor 10.

As has been seen, the members 22 are therefore immobilized by the particular profile of all the passages of the plate 14. Preferably, the section of each passage 24 will thus be delimited for the profile P for all the plates 14 of the rotor 10, in order to ensure that the members 22 are held along the entire length of the rotor. It is also possible to envisage an alternation of plates comprising passages 24 provided with profiles P and plates devoid of this profile, without limitation of the invention.

Advantageously, to allow the passage 24 to play its previously described role of orienting the field lines in the radial direction, each passage 24 is not closed around the member 22.

In the preferred embodiment of the invention, each member 22 is cylindrical. As seen previously with reference to the FIG. 1 the members 22 may be screws. However, preferably, the rotor 10 has end plates 18 and the members 22 are rivets which are riveted at their ends into the plates 18.

Advantageously, walls of the outer radial end edge 26 and the lug(s) 34, 36 in contact with the member 22 have the same radius of curvature as the member 22.

The remainder of the passage 24 determines a second subsection 27 which is contiguous to the first subsection 25 and which is also open between a lug 34, 36 and the opposite edge 32, 30 when the passage 24 only has one lug 34, 36, or between the two lugs 34, 36 when it has two. This allows the metallic material of the plate 14 not to be closed between the lug 34, 36 and the opposite edge 32, 30 when the passage only has one lug 34, 36, or between the lugs 34, 36 when the passage 24 has two, which would significantly modify the orientation of the flow lines.

Furthermore, to generally maintain a surface area of the passage 24 equivalent to that of the passage 24 without lugs 34, 36, a surface area of the second subsection 27 is greater than that of the first subsection 25.

There FIG. 3 illustrates a first embodiment of the invention in which only the parts of the lugs 34, 36 which are in contact with the member 22 have the same radius of curvature as the member 22. This configuration makes it possible to limit to the strict minimum the difference between the section P of the passage 24 according to the invention and a passage 24 of oval shape which is the most optimal for the orientation of the flow lines. However, the conformation of the passage 24 according to this shape requires the use of a punch of a particular shape or a complex cutting process.

There FIG. 4 illustrates a second simplified embodiment of the invention in which the first and second subsections are substantially circular or oval in shape, which makes it much simpler to produce them, whether with a die cutter or by another cutting method. In this particular case, an inner radial end edge 40 of the second subsection 27 has a radius of curvature greater than the radius of curvature of the member 22. As a result, the section of the passage 24 has the shape of an 8.

It is not necessary for each oblong lumen of the plate 14 to act as a passage for a member 22, since a limited number of members 22 makes it possible to ensure that the plates 14 are held together. Also, preferably, as illustrated in FIGS. 3 and 4, the oblong lumens 24 forming passages for members 22 alternate angularly with the oblong lumens 24 without members 22.

Of course, this configuration is not limiting of the invention, and a different angular distribution of the members 22 around the axis X of the plates 14 could lead to a configuration in which two or more oblong slots 24 without members 22 would alternate with oblong slots 24 forming passages for members 22.

Here, the plates 14 also have rectilinear oblong openings 42 of radial orientation distributed angularly in a regular manner around the axis X in order to allow the passage of flux-generating members (not shown), such as windings or magnets.

In the preferred embodiment of the invention, these lights 42 alternate angularly with the oblong lights 24.

The invention therefore makes it possible to advantageously make an electric machine rotor comprising a stack of plates more reliable, and at a lower cost, since it only requires a modification of the cutting of the oblong slots 24 during the manufacture of the plates 14.

Claims (10)

Axial stack (12) of axis X of metal plates (14) for a rotor (10) of an electric machine, said stack further comprising axial fixing members (22), said plates (14) being immobilized transversely relative to the axis X by means of said fixing members (22) passing through passages (24) for said members (24) formed in said plates (14), a cross-section of said members (22) having a surface area smaller than a surface area of a cross-section of said passages (24), the section of each passage (24) in at least one of the plates being delimited by a profile (P) configured to immobilize transversely each member (22) in said passage (24), in order to avoid bending of said members (22) through said passages (24). Stack according to the preceding claim, characterized in that the section of each passage (24) is delimited for said profile (P) for all of the plates (14) Stack (12) of plates (14) according to one of the preceding claims, in which the profile (P) of each passage (24) comprises an outer radial end edge (26) matching a first part (28) of an external surface of each member (22) and two opposite intermediate edges (30, 32), at least one of said intermediate edges comprising a lug (34, 36) projecting towards the inside of the passage (24) and capable of immobilizing a second part (38, 38a, 38b) of the external surface of each member (22), the outer radial end edge (26) and said at least one lug (34, 36) delimiting a first subsection (25) of the passage (P) open between said at least one lug (34, 36) and the opposite intermediate edge (30, 32). Stack (12) of plates (14) according to the preceding claim in which each intermediate edge (30, 32) comprises a said lug (34, 36), said lugs being tangentially opposite each other. Stack (12) of plates (14) according to the preceding claim, in which each member (22) is cylindrical and in which the walls of the outer radial end edge (26) and the lugs (34, 36) in contact with said member (22) have the same radius of curvature as said member (22). Stack (12) of plates (14) according to any one of claims 4 and 5, in which the remainder of the passage (24) determines a second subsection (27) adjoining the first subsection (27) and also open between the two lugs (34, 36), a surface of the second subsection (27) being greater than that of the first subsection (25). Stack (12) of plates (14) according to any one of the preceding claims, in which each plate (24) comprises a series of oblong slots of radial orientation distributed angularly in a regular manner around the X axis, said slots being configured to radially orient the lines of magnetic flux in said rotor (10), each passage (24) being constituted by one of said oblong slots. Stack (12) of plates (14) according to the preceding claim in which the oblong slots forming passages for members (22) alternate angularly with the oblong slots without members (22). Rotor (10) of an X-axis electric machine comprising a stack (12) of plates (14) according to any one of the preceding claims and, optionally, two end flanges (18) arranged axially on either side of said stack (12), said flanges (18) holding the plates (14) clamped in the stack and being fixed to ends of the axial fixing members (22). Electrical machine comprising a rotor (10) according to the preceding claim.