MACHINE WITH TOROIDAL WINDING

Abstract

An electric machine comprises a yoke supporting N toroidal coils and a central rotor comprising a permanent magnet. The yoke has a plurality of stator modules comprising at least one stator core made from a soft ferromagnetic material supporting at least one coil. The stator cores have, at their front ends, complementary coupling surfaces providing magnetic and mechanical continuity. The machine further comprises—a cylindrical outer casing made from a thermally conductive material, —a plurality of continuous and solid longitudinal ribs extending radially and positioned between the cylindrical outer casing and the stator modules, in order to ensure the mechanical positioning of the yoke relative to the outer casing and promote the thermal conduction of heat from the yoke toward the outer casing.

Claims

1. An electric machine, comprising: a yoke supporting N toroidal coils, the yoke having a plurality of stator modules each having at least one core comprising a soft ferromagnetic material supporting at least one coil of the N toroidal coils, the stator module having, at front ends of the cores, complementary coupling surfaces providing magnetic and mechanical continuity; a central rotor comprising a permanent magnet; a cylindrical outer casing made from a thermally conductive material; and a plurality of continuous and solid longitudinal ribs extending radially and positioned between the cylindrical outer casing and the stator modules to ensure the mechanical positioning of the yoke relative to the cylindrical outer casing and promote thermal conduction of heat from the stator modules toward the cylindrical outer casing.

2. The electric machine of claim 1, wherein the longitudinal ribs radially extend either the cylindrical outer casing or one of the stator modules made from a soft ferromagnetic material, or are in the form of a conductive material placed at the interface between the cylindrical outer casing and the stator modules.

3. The electric machine of claim 2, each coil is in the form of wound turns arranged in planes forming, with a radial plane, an increasing angle on either side of a median transverse plane of the coil, so that the radial thickness of the coil is greater inside than outside of the yoke.

4. The electric machine of claim 3, wherein: the yoke is made up of N/2 stator modules made from a soft ferromagnetic material having two stator cores defining arms; the two arms extending symmetrically with respect to a radial median plane; each of the arms supporting a coil; and the arms having, at their front ends, complementary assembly zones providing magnetic continuity.

5. The electric machine of claim 4, wherein the stator modules made from a soft ferromagnetic material have two stator cores extending on either side of a rib directed toward the side opposite the rotor and coming into contact with the inner surface of the cylindrical outer casing made from a thermally conductive material.

6. The electric machine of claim 4, wherein the cylindrical outer casing made from a thermally conductive material has radially extending ribs, the front end of which comes into contact with the stator cores made from a soft ferromagnetic material, at the intersection of two adjacent stator modules.

7. The electric machine of claim 6, wherein the ribs and/or the front ends have a chamfer to allow a forcible introduction of the yoke into the cylindrical outer casing.

8. The electric machine of claim 6, wherein the ribs are in contact with the lateral ends of two consecutive stator cores to ensure positioning of the stator cores constituting the yoke.

9. The electric machine of claim 1, wherein the yoke is made up of N stator modules each having a stator core made from a soft ferromagnetic material supporting a coil whose turns are arranged in planes forming an increasing angle on either side of a median transverse plane of the coil, and wherein: the stator cores have, at their front ends, complementary assembly zones providing magnetic continuity; and the machine further comprises a cylindrical outer casing having N longitudinal ribs, the inner front surface of which comes into contact with the outer surface of a connection zone of two adjacent stator cores to ensure the mechanical wedging of the yoke with respect to the cylindrical outer casing and thermal conduction of heat from the yoke to the cylindrical outer casing.

10. The electric machine of claim 1, wherein a stack of sheets in the axial direction and made from a non-magnetic material having a thermal conductivity higher than a thermal conductivity of air, is positioned at the interface between the cylindrical outer casing and the coil.

11. The electric machine of claim 1, further comprising a thermally conductive material at the interface between the cylindrical outer casing and the coil.

12. The electric machine of claim 10, wherein the stack of sheets is in contact with the cylindrical outer casing and the coil.

13. The electric machine of claim 11, wherein the thermally conductive material is in contact with the cylindrical outer casing and the coil.

14. The electric machine of claim 1, each coil is in the form of wound turns arranged in planes forming, with a radial plane, an increasing angle on either side of a median transverse plane of the coil, so that the radial thickness of the coil is greater inside than outside of the yoke.

15. The electric machine of claim 1, wherein: the yoke is made up of N/2 stator modules made from a soft ferromagnetic material having two stator cores defining arms; the two arms extending symmetrically with respect to a radial median plane; each of the arms supporting a coil; and the arms having, at their front ends, complementary assembly zones providing magnetic continuity.

16. The electric machine of claim 15, wherein the stator modules made from a soft ferromagnetic material have two stator cores extending on either side of a rib directed toward the side opposite the rotor and coming into contact with the inner surface of the cylindrical outer casing made from a thermally conductive material.

17. The electric machine of claim 15, wherein the cylindrical outer casing made from a thermally conductive material has radially extending ribs, the front end of which comes into contact with the stator cores made from a soft ferromagnetic material, at the intersection of two adjacent stator modules.

18. The electric machine of claim 17, wherein the ribs and/or the front ends have a chamfer to allow a forcible introduction of the yoke into the cylindrical outer casing.

19. The electric machine of claim 17, wherein the ribs are in contact with the lateral ends of two consecutive stator cores to ensure positioning of the stator cores constituting the yoke.

Description

BRIEF DESCRIPTION OF THE DRAWINGS

[0041] The present disclosure will be better understood on reading the detailed description of a non-limiting example of the present disclosure, which follows, with reference to the accompanying drawings, where:

[0042] FIG. 1 shows a cross-sectional view of a first embodiment,

[0043] FIG. 2 shows a cross-sectional view of a first variant embodiment,

[0044] FIG. 3 shows a cross-sectional view of a second variant embodiment,

[0045] FIG. 4 shows a cross-sectional view of a third variant embodiment,

[0046] FIG. 5 shows a cross-sectional view of a fourth variant embodiment,

[0047] FIG. 6 shows a cross-sectional view of a fifth variant embodiment.

[0048] FIG. 7 shows a cross-sectional view of a sixth variant embodiment.

DETAILED DESCRIPTION

[0049] The present disclosure relates to a configuration of a stator comprising a yoke formed by several modules, all identical. Each stator module has at least one stator core (218) extending perpendicular to a radius passing through the middle of this stator core (218), and which is surrounded by a coil (211).

[0050] This stator core (218) is mechanically and thermally coupled to a cylindrical outer casing (200) surrounding the stator via continuous and solid longitudinal connections, of rectangular cross-section, extending over the entire length of the stator between: [0051] a) the inner surface of the cylindrical outer casing (200), and [0052] b) the junction zone of two stator cores (218, 226).

[0053] These longitudinal connections provide a dual function: [0054] mechanical wedging of the stator modules with respect to the cylindrical outer casing (200) [0055] thermal transmission of the heat produced by the coils (211) to the cylindrical outer casing (200). The longitudinal connections are therefore continuous and solid, possibly laminated, so as to maximize the thermal conductivity between the yoke of the stator and the cylindrical outer casing (200). The cylindrical outer casing (200) is then itself associated with a cooled housing, with fins, or directly ensures the discharge of heat to the outside of the motor.

[0056] To this end, the connection between the stator modules and the cylindrical outer casing (200) is made either by continuity of the material, or by a tight fit ensuring direct contact with the ferromagnetic material.

[0057] The following description illustrates different implementation alternatives based on this general principle, where: [0058] the stator modules are formed by a core surrounded by its coil, the longitudinal connections then being monolithic ribs extending the inner surface of the cylindrical outer casing (200), these ribs having a longitudinal groove in which the outer edges fit two consecutive stator cores (218, 226), without play,

[0059] or [0060] the stator modules have a “Y”-shaped cross-section, the foot then forming the longitudinal connection, the front surface of which bears tightly against the inner surface of the cylindrical outer casing (200), and the two arms constituting two stator cores (216, 218) each supporting a coil, the longitudinal front surfaces of the arms of two adjacent stator modules coming into close contact,

[0061] or [0062] the modules have a “U”-shaped cross-section, the two branches of the “U” then forming the continuous and solid longitudinal connection, the front surface of which bears tightly against the inner surface of the cylindrical outer casing (200), and the zone connecting the two branches of the “U” constituting the core (218) supporting a coil, the longitudinal front surfaces of the arms of two adjacent stator modules coming into close contact,

[0063] or [0064] a mix of these two solutions, alternately with a “Y” configuration and a rib formed on the cylindrical outer casing (200)

[0065] and more generally any configuration ensuring: [0066] a) continuity or assembly without play and with ferromagnetic, thermal and mechanical continuity between the longitudinal front ends of the cores (218); [0067] b) continuity or assembly without play and with thermal and mechanical continuity between the longitudinal front junction zones of two consecutive stator cores (218, 226) and the cylindrical outer casing (200).

[0068] The assembly being able to be assembled by longitudinal sliding of the stator modules provided with the coils (211, 261, 227, 231, 241, 251) in the cylindrical outer casing (200), with an assembly without play after positioning of the modules.

[0069] FIG. 1 shows a cross-sectional view of a first embodiment.

[0070] The electric machine comprises a rotor (100) with a diametrically magnetized tubular magnet, covered with a hoop (not visible) to prevent the pulling out of particles under the effect of the centrifugal force for high-speed machines.

[0071] It comprises a metallic cylindrical outer casing (200), manufactured, for example, by molding, foundry or even by profiling, surrounding a stator comprising toroidal coils (211, 261; 227, 231; 241, 251) and a yoke in the form of a set of three longitudinal stator modules (215, 225, 245), having a “Y”-shaped section, with a rib extending on either side of two stator cores, respectively (216, 218; 226, 228; 240, 250), these stator cores being made from a soft ferromagnetic material, preferably a stack of sheets. Each of the stator cores (216, 218, 226, 228, 240, 250) is surrounded by a coil, respectively (211, 261; 227, 231; 241, 251).

[0072] The coils (211, 261, 227, 231, 241, 251) are formed with turns of an electrically conductive material—copper or aluminum, for example, whose inclination varies. The plane (302) formed by the turn at the start of the winding forms an open angle with the radial plane (300). This angle is reduced to become zero for the median turns whose plane coincides with the radial plane (300), then this angle between the plane of the turn and the radial plane (300) increases again—in the opposite direction—up to the end of the winding, where the angle of the turn (303) again has an open angle with respect to the radial plane (300). Furthermore, the section of the winding is not identical inside and outside the stator, on either side of the stator cores (216, 218; 226, 228; 240, 250). Indeed, to optimize the overall volume of the machine, but also to optimize the performance of the motor, the turns outside the stator cores (216, 218; 226, 228; 240, 250) are distributed over the entire length of the formed polygonal side. This configuration allows the copper volume of the winding to be maximized while limiting the outer diameter and the volume of the machine.

[0073] The wedging of the stator modules with respect to the cylindrical outer casing (200) is ensured, in this embodiment, by the external shape of the front surface of the longitudinal ribs (312, 332, 352) forming the foot of the “Y” in cross-section, which come into contact with the cylindrical outer casing (200). The cylindrical outer casing (200) is generally made of a material having good thermal conduction properties, for example, aluminum, which also allows the stator modules (215, 225, 245) to conduct the heat flux produced by the coils (211, 261, 227, 231, 241, 251) during machine operation.

[0074] In the embodiment illustrated in FIG. 2, the wedging of the stator modules with respect to the cylindrical outer casing (200) is ensured firstly by longitudinal ribs (212, 232, 252) extending the inner surface of the cylindrical outer casing (200), and having an inner border configured to receive the outer surface of the connection zone of two adjacent stator modules.

[0075] To this end, the longitudinal ribs (212, 232, 252) have a “V”-shaped groove (213, 233, 253) in which the edge formed by two adjacent stator cores (216, 250; 218, 226; 228, 240) is able to slide longitudinally during assembly, and to ensure the wedging after installation inside the cylindrical outer casing (200).

[0076] Wedging is also ensured by the outer longitudinal surface of the three stator modules (215, 225, 245), having a rounded contact surface, with a radius of curvature corresponding to the radius of curvature of the inner surface of the cylindrical outer casing (200).

[0077] The contact between the three stator modules (215, 225, 245) and the cylindrical outer casing (200) and between the longitudinal ribs (212, 232, 252) and the edges of the stator cores (218, 226, 228, 240, 250, 216) provides mechanical wedging and thermal conduction bridges allowing discharging of the heat produced by the electric coils (211, 261, 227, 231, 241, 251) of the machine.

[0078] FIG. 3 shows a cross-sectional view of an embodiment that differs from the previous ones in that it only comprises longitudinal ribs (212, 312, 232, 332, 252, 352) radially extending the cylindrical outer casing (200), as wedging elements and thermal contact between the cylindrical outer casing (200) and the stator cores (218, 226, 228, 240, 250, 216) that do not have ribs.

[0079] The ends of the ribs (212, 312, 232, 332, 252, 352) advantageously have a chamfer to facilitate relative positioning at the time of assembly.

[0080] In particular, these ribs (212, 312, 232, 332, 252, 352) have “V”-shaped grooves (213, 313, 233, 333, 253, 353) to ensure the wedging of the connection zones of two adjacent stator cores.

[0081] The yoke of the stator may be inserted by axial sliding in the cylindrical outer casing (200), the connection zones of the stator cores (216, 218, 226, 228, 240, 250) sliding in the “V”-shaped grooves (213, 313, 233, 333, 253, 353) of the longitudinal ribs (212, 312, 232, 332, 252, 352).

[0082] Thermal transmission is ensured by these radial elements, which also ensure the mechanical wedging of the yoke with respect to the cylindrical outer casing (200).

[0083] FIGS. 4 to 6 show variant embodiments with the aim of improving the heat dissipation performance of the machine toward the cylindrical outer casing (200). To do this, it is proposed to fill the free space between the machine and the cylindrical outer casing (200) with a thermally conductive but non-magnetic material minimizing the development of induced currents during operation of the machine. In the present example, a stack of aluminum sheets (400, 410, 420, 430, 440, 450, 401) is proposed. Thermal conduction is thus maximized without disturbing the operation of the machine, since stacking the sheets (400, 410, 420, 430, 440, 450, 401) in the axial direction, a direction perpendicular to the majority of the magnetic field lines of the motor, will limit the development of induced currents and therefore losses.

[0084] The shape of these stacks of sheets (400, 410, 420, 430, 440, 450, 401) may vary. In the first example of FIG. 4, the shape hugs the coils (211, 261, 227, 231, 241, 251) and the stator cores (216, 218, 226, 228, 240, 250) as closely as possible. These stacks of sheets (400, 410, 420, 430, 440, 450) have an arcuate blade shape to allow them to be housed between two consecutive ribs, against the inner surface of the cylindrical outer casing (200). The stack of sheets (400) is as close as possible to the coils, the source of the heat dissipation.

[0085] In a second example in FIG. 5, the stack of sheets (401) forms a ring that is housed coaxially inside the cylindrical outer casing (200). This ring of sheets has ribs (212, 312, 232, 332, 252, 352) ensuring the mechanical wedging of the stator and the transmission of heat between the yoke of the stator supporting the coils and the cylindrical outer casing (200).

[0086] In a third example in FIG. 6, the stack of sheets (400, 410, 420, 430, 440, 450) takes the form of longitudinal blades inserted locally between the cylindrical outer casing (200) and the coils. The ribs (212, 312, 232, 332, 252, 352) are, as in the case of the example of FIG. 3, interior extensions of the cylindrical outer casing (200).

[0087] These examples are not limiting, and other variants may be proposed without departing from the present disclosure.

[0088] Indeed, the present disclosure is not limited to the use of aluminum sheets. The stack of sheets may be made from another material, benefiting from better thermal conductive properties than air. Similarly, any solid material may be used as long as it is a better thermal conductor than air and is non-magnetic and electrically insulating, or has poor magnetic and electrical properties relative to iron.

[0089] FIG. 7 shows a cross-sectional view of an embodiment that differs from the previous ones in that the stator cores (218, 226, 228, 240, 250, 216) are extended at each end by an extension (412, 562; 422, 512; 432, 522, 442, 532; 452, 542; 462, 552) giving the stator cores a “U” shape. Pairs of the extensions (412, 512; 422, 522; 432, 532, 442, 542; 452, 552; 462, 562) of two separate stator cores are assembled to form the longitudinal ribs as wedging elements and thermal contact between the cylindrical outer casing (200) and the various stator cores (218, 226, 228, 240, 250, 216).

[0090] The yoke of the stator may be inserted by axial sliding in the casing, the ribs having, at their radial ends, shapes complementary to the cylindrical outer casing (200).

[0091] The extensions (412, 422, 432, 442, 452, 462) and (512, 522, 532, 542, 552, 562) have complementary shapes, such as, for example, a dovetail, cooperating by axial sliding to secure two adjacent stator cores.