Slotless electrical machine with concentrated winding

Abstract

An electrical machine includes a tubular rotor magnetised to have circumferential polar alternations, and a stator including a body that is traversed by a channel having an inner transverse section that substantially corresponds to the outer transverse section of the rotor, the body carrying a plurality of windings, the stator being surrounded by an outer ferromagnetic envelope, the body being extended by three, four or six radial projections made from an electrically insulating material having, in the transverse cross section, a longitudinal core for receiving a winding, the core being extended by a peripheral extension having an outer surface that matches the inner surface of the envelope and covers the wound area. A method for producing such an electrical machine is also provided.

Claims

1. An electrical machine comprising a tubular rotor magnetised so as to have circumferential pole alternations, and a stator comprising a body through which there passes a channel with an inside cross-section corresponding substantially to the outside cross-section of said rotor, said body supporting a plurality of coils, said stator being surrounded by a ferromagnetic external envelope, said body being extended by three, four or six radial protuberances made from an electrically insulating material, having, in cross-section, a longitudinal core for receiving a coil, said core being extended by a peripheral extension having an external surface complementary to the internal surface of said envelope and covering a wound area.

2. An electrical machine according to claim 1, wherein said body comprises three protuberances and said rotor comprises one or two pairs of poles, said body having a central part with a triangular cross-section.

3. An electrical machine according to claim 1, wherein a radius of said rotor is greater than the distance between the longitudinal axis of said channel of said stator, and a plane passing through an internal turn of a winding.

4. An electrical machine according to claim 1, wherein an external radius of said envelope is less than 5 mm.

5. An electrical machine according to claim 1, wherein a space between said envelope and said rotor is at least partially filled with a mixture containing ferromagnetic particles.

6. An electrical machine according to claim 5 wherein said mixture is a plastics material loaded with said ferromagnetic particles.

7. An electrical machine according to claim 1, wherein said body is at least partially produced from a mixture loaded with ferromagnetic particles.

8. An electrical machine according to claim 1, wherein said body forms, with said envelope, a single piece produced from a mixture loaded with ferromagnetic particles.

9. An electrical machine according to claim 1, wherein said external envelope is produced from a plastics material loaded with ferromagnetic particles.

10. An electrical machine according to claim 1, wherein said magnetised rotor is formed by an assembly of magnets in the form of tiles magnetised diametrically in alternating directions.

11. An electrical machine according to claim 1, wherein said magnetised rotor is formed by a sintered single-piece material magnetised in a single direction or alternating directions.

12. An electrical machine according to claim 1, wherein said body has, at one of the ends, metallised surfaces for soldering the winding wire on the one hand and connection with the connection element on the other hand.

13. An electrical machine according to claim 1, wherein said body is produced from an elastically deformable material.

14. An electrical machine according to claim 1, wherein said protuberances are slotted along a radial symmetry plane.

15. An electrical machine according to claim 1, wherein an external radius of said rotor is between 0.4 R and 0.5 R, with R designating the external radius of the rotor.

16. An electrical machine according to claim 1, wherein a mean width L.sub.N of said core is between 0.5 R and 1.2 R.

17. An electrical machine according to claim 1, wherein a maximum width L.sub.P of said peripheral extension is between 1.1 R and 1.8 R and greater than E+L.sub.N, where E designates the thickness of said coil.

18. An electrical machine according to claim 1, wherein said cross-section of said cores is constant.

19. An electrical machine according to claim 1, wherein said cross-section of the cores is restricted in a direction of an outside.

20. An electrical machine according to claim 1, wherein said envelope includes a packet of stacked metal sheets.

21. A method for producing an electrical machine comprising a tubular rotor magnetised so as to have circumferential polar alternations, and a stator comprising a body through which there passes a channel with an internal cross-section corresponding substantially to an external cross-section of said rotor, said body supporting a plurality of coils, said stator being surrounded by a ferromagnetic external envelope, said body being extended by three, four or six radial protuberances made from an electrically insulating material, having, in cross-section, a longitudinal core for receiving a coil, said core being extended by a peripheral extension having an external surface complementary to an internal surface of said envelope and covering a wound area, said method comprising producing said body, winding a conductive wire around each of said cores, and inserting said body thus wound in said envelope.

Description

BRIEF DESCRIPTION OF THE DRAWINGS

(1) The invention will be better understood in the light of the following figures relating to non-limitative example embodiments, where:

(2) FIG. 1a presents a motor according to the invention in a perspective view in a first embodiment;

(3) FIG. 1b presents the motor in FIG. 1a in a cross-sectional view;

(4) FIG. 1c presents the motor in FIG. 1a in an axial-section view passing through the rotation axis;

(5) FIG. 1d presents an isolated view of the coil support in the first embodiment;

(6) FIG. 2a presents a motor according to the invention in a perspective view in a second embodiment;

(7) FIG. 2b presents an exploded view of the motor of FIG. 2a;

(8) FIG. 2c presents the motor of FIG. 2a in a cross-sectional view;

(9) FIG. 3 presents a particular embodiment of a coil support according to the invention;

(10) FIG. 4 presents a particular embodiment of coil connections on a wound support according to the invention;

(11) FIG. 5a presents another particular embodiment of a wound support according to the invention;

(12) FIG. 5b presents the wound support of FIG. 5a in a cross-sectional view; and

(13) FIG. 6 presents a cross-sectional view of the support according to an alternative embodiment.

DETAILED DESCRIPTION

(14) First Example Embodiment

(15) FIG. 1a shows a three-phase slotless electric motor (1) according to a first embodiment. Tubular in shape, it comprises at the stator an external envelope (2) here in the non-limitative form of a packet of metal sheets (10) stacked in the axial direction, that is to say along the rotation axis (3). The movable assembly consists of a rotation shaft (3) and a cylindrical magnetised rotor (7), here having two pairs of magnetised poles (two alternations of north and south poles). In the example described, the magnetised poles are formed by longitudinal magnets (11 to 14), magnetised transversely in order to have circumferential north-south alternations. The external surface of the magnets is in the form of a portion of a cylinder, so that the assembly of the magnets has a tubular external surface, with a circular cross-section that is constant over the entire height of the motor.

(16) The central part (15) consists of a ferromagnetic piece forming a magnetic yoke and providing transmission of the torque to the spindle (3) that passes through it or extends it. The stator assembly, apart from the external envelope (2), also comprises a body (4) depicted in detail in FIG. 1d. This body (4) has a central longitudinal channel (16) as well as three protuberances (17 to 19) forming cores (20 to 22) on which three separate electrical coils (5a, 5b and 5c) are wound, separated each by an angle of 120 in order to form a three-phase excitation assembly.

(17) As can be appreciated in FIG. 1b, the bodies (4) of the coils are distributed over the internal periphery of the external envelope (2) and form grooves or slots in which the coils (5a, 5b and 5c) are wound. The cores (20 to 22) are extended radially by peripheral extensions (30 to 32) having an external surface complementary to the internal surface of the external envelope (2). These peripheral extensions (30 to 32) cover the coiled zone surrounding the cores (20 to 22) in order to provide the electrical insulation of the turns of the windings (5a to 5c).

(18) In this first embodiment, the coils (5a, 5b and 5c) are installed so that they partially surround the magnetised movable part (7), thus producing a compact assembly. In this example, the channel (16) has a radius greater than the distance measured radially between the central longitudinal axis (3) of the motor, and the plane (40) passing through the internal turn of the coils (5a, 5b, 5c). This solution maximises the useful volume of copper in the available space. This solution involves placing the rotor (7) in the channel (16) of the stator, prior to the winding.

(19) For a stator with external radius R, the external radius of the rotor is between 0.4 R and 0.5 R. The mean width L.sub.N of the core is between 0.5 R and 1.2 R. The cross-section of this core (20 to 22) may be constant, or may be restricted in the direction of the outside, as illustrated for example by FIGS. 2a to 2c. The core may also broaden towards the outside, but this solution is less advantageous. The maximum width L.sub.P of the peripheral extension (30 to 32) is between 1.1 R and 1.8 R and in any event greater than E+L.sub.N, where E designates the thickness of the coil (5a, 5b, 5c).

(20) The coil body (4), detailed in FIGS. 1a-d, is formed in a single piece, the central area of which has a circular piercing (8) able to allow the rotation spindle (3) and any guide element (not shown here) to pass. On the periphery of the body (4), three extensions (17 to 19) are provided, delimiting the locations for the windings of the three coils (5a, 5b and 5c). Each of the extensions (17 to 19) is symmetrical with respect to a radial mid-plane.

(21) Each location is characterised by grooves or slots (6) that describe a closed path all around the cores (20 to 22) and thus extending in the axial and transverse direction with respect to the rotation axis (3) of the motor (1). The unicity of the coil body (4) and the presence of the grooves (6) make implementation of the assembly thus coiled easy, precise and sure.

(22) Second Example Embodiment

(23) FIGS. 2a, 2b and 2c depict a second example embodiment. The external envelope (2) is produced from a solid ferromagnetic material. The stator body is produced in a piece moulded from plastics material loaded with ferromagnetic particles. The rotor comprises a cylindrical magnet formed by a pair of poles by assembling a tubular-shaped single-piece magnet, magnetised substantially diametrically in order to have a north pole on a tubular half-perimeter and a south pole on a complementary tubular half-perimeter (12).

(24) The extensions (17 to 19) differ from those described in relation to the first embodiment through the fact that the cores (20 to 22) have a trapezoidal-shaped cross-section, with the large base on the internal side and the large base on the external side, which makes it possible to maximise the filling with copper with respect to the available space. The plane (40) passing through the bottom turns of the coil passes through the rotor, but an axial extension (100) enables the winding not to intersect the plane (40). Thus, since the channel (16) has a constant cross-section, it is possible to introduce the rotor by an axial movement of the wound stator. The peripheral extension (30 to 32) completely covers the windings (5a, 5b, and 5c).

(25) Third Variant Embodiment

(26) FIG. 3 depicts a body, the extensions (17 to 19) of which are split by longitudinal slits (41, 51, 61). In the example described, the protuberances (17 to 19) are formed by flanges (42, 43; 52, 53; 62, 63) symmetrical with respect to the radial plane passing through the corresponding extension. The extensions (17 to 19) are thus elastically deformable.

(27) Fourth Variant Embodiment

(28) FIG. 4 presents a variant embodiment in which some areas of the stator body are metallised in order to form areas (70 to 73) enabling the wires of the windings to be soldered, and extended by metallised tracks in order to end up at second metallised areas (81 to 83) providing the electrical connection.

(29) Fifth Variant Embodiment

(30) FIGS. 5a and 5b present a variant in which the stator body is produced with a ferromagnetic internal part (90), for example a piece made from plastics material loaded with ferromagnetic particles, and an external part (91) made from plastics material. In general terms, for the different variants, the ferromagnetic material advantageously has a relative permeability below 100 and a low coercivity (coercitive field less than 100 A/m) in order to reconcile the satisfactory closure of the field lines and the limitation of the expansion torque and iron losses.

(31) Sixth Variant Embodiment

(32) FIG. 6 describes an alternative where the stator body forms a single piece with the tubular envelope (2), by assembly or overmoulding with the same plastics material loaded with ferromagnetic particles.