WO2008026032A1

WO2008026032A1 - Electric machine with stator equipped with remote-controlled claws and windings

Info

Publication number: WO2008026032A1
Application number: PCT/IB2007/002437
Authority: WO
Inventors: Pierre-Emmanuel Cavarec; Thierry Tollance
Original assignee: Somfy Sas
Priority date: 2006-08-28
Filing date: 2007-08-24
Publication date: 2008-03-06
Also published as: FR2905205A1

Abstract

Electric machine (10) comprising a mobile rotor (40) moving around an axis (22) of the machine and a primary stator sector (20) with primary ferromagnetic claws (29a, 29b, 29c) stretching around the rotor defining a revolution cylinder (C) coaxial to the rotor, with the first part of the stator being active and comprising a plurality of windings (28a, 28b, 28c) making it possible to differently magnetize the primary ferromagnetic claws of the same orientation and consecutive in the direction of the rotation of the rotor, characterized in that it comprises a second part (30) with a passive rotor and comprising secondary ferromagnetic claws (31 a, 31 b, 31c) also delimiting the revolution cylinder, intercalated with the primary ferromagnetic claws and connected to a ferromagnetic base plate (34).

Description

Electric stator machine with claws and remote windings.

The invention relates to the field of tubular type electric machines with wound stator. The invention applies preferentially to synchronous type motors with magnetized rotor, but it can also be applied to step-by-step or asynchronous motors. The invention also applies to alternators of the tubular type.

The machines are called tubular when their length is greater than their diameter.

A problem posed by the realization of tubular motors is obtaining significant power or a large torque in a limited diameter. Indeed, a conventional stator winding solution then leads to reduce the diameter of the rotor, and thus to limit the performance of the engine. This problem radial size engine is crucial in some applications, including some home automation applications where the motor ^is to be mounted in a winding tube of a blind or a roller shutter, such a tube having in general a reduced diameter and a very large length compared to its diameter.

It is known, for stepper motors, to use stator configurations using claw pole poles ("claw-pole stepping motor"), especially in the case of two-phase feed motors. . An exemplary embodiment is given by US patent application 2005/0046305. In this motor, two coils are arranged on either side of the rotor of the motor, the axes of the coils being merged with that of the rotor. Other examples are given by patent applications EP 1 420 507 or JP 2005328647. Patent application JP 2001161054 describes a three-phase configuration.

A disadvantage of these structures lies in the fact that each phase acts on only a portion of the rotor, for example half of the rotor, or even the third of the rotor in the case of the application JP 2001161054. This underutilization of the rotor is detrimental to obtaining a high power or a strong torque in a given diameter. The fact of arranging each winding around the rotor, in this application, forces to reduce the diameter thereof if the total diameter is imposed.

The same type of disadvantage is found in motors comprising a winding tooth, as described for example in US Patent 6,847,149.

GB 960,879 and US Pat. No. 2,582,652 are known from electric motors comprising a rotor with permanent magnets and a stator comprising two claw parts arranged on either side of the rotor and interlocking. These stator parts are each magnetized by means of coils. The structure of such motors is complicated: it is necessary to provide means for supplying windings arranged on either side of the rotor.

DE 43 01 675 discloses an electropump whose motor comprises a rotor provided with magnets and a stator provided with coils of axes perpendicular to the axis of the motor. Magnetic flux conducting parts make it possible to guide the flux created by the stator windings around the rotor. Patent BE 503 926 also discloses a dynamo stator having a similar structure. Such machines present simple structures. However, their performance is not very good.

The object of the invention is to provide an electrical machine overcoming the disadvantages mentioned above and improving the electrical machines known from the prior art. In particular, the invention proposes an electric machine, in particular a motor, having a simple structure minimizing its radial size while affecting as little as possible its mechanical torque and more generally its performance.

The electric machine according to the invention is defined by claim 1.

Different embodiments of a machine according to the invention are defined by the dependent claims 2 to 9.

The appended drawing represents, by way of example, an embodiment of an engine according to the invention.

Figure 1 is an exploded view of an engine according to the invention.

Figure 2 is a sectional view of a first stator portion of the motor according to the invention.

Figure 3 is a perspective view of the first part of the stator.

The motor 10 shown in Figure 1 comprises a rotor 40 and a stator in two parts, a first portion 20, a second portion 30. The axis 22 of the motor around which the rotor rotates is represented by a dashed line. The rotor 40 comprises a shaft 41 and a ferromagnetic hub 42 on which is disposed a cylindrical magnet 43. The cylindrical magnet 43 is sectored and comprises four pairs of alternating poles with radial magnetization in the case of a 50 mm diameter motor. Two sectors are represented in the figure: a first sector 44 whose magnetization is radial centrifugal, and a second sector 45 whose magnetization is centripetal radial. Alternatively, the magnetization of the sectors could be tangential.

The two stator parts are different, the first is active and the second passive. These two parts are nested one inside the other.

The first stator portion 20 comprises three coils, not shown in Figure 1, while the second stator portion 30 serves only to close the magnetic circuit.

In Figure 2, the first stator portion is shown in section along a plane P1 perpendicular to the axis of the motor.

The first stator part comprises three identical subassemblies 21a, 21b and 21c, offset by 120 ° in rotation around the axis of the motor and mounted on a hub 24. The hub comprises a first bore 25 allowing rotation guidance of the rotor by the shaft 41.

The first subassembly 21a comprises a tooth 26a extending radially with respect to the axis of the motor, a magnetic flux collector 27a and a winding 28a. The flux collector is preferably an angular sector of a cylindrical ring whose angular aperture α with respect to the axis of the motor is substantially less than 60 °, for example the angle α is between 45 and 55 °. In each subassembly, an identical electric winding is made around the tooth. The winding 28a thus surrounds the tooth 26a of the subassembly 21a. Preferably, this winding occupies all the space available between the hub and the flux collector, while nevertheless leaving sufficient space for the interlocking of the second stator part in the first part.

Figure 3 shows the first stator portion 20 in perspective. There is shown a plane P2 perpendicular to the axis of the motor and tangential to the right end of the hub 24.

In each subassembly 21a, 21b, 21c, the flux collector 27a, 27b, 27c is extended on its right side by a pole claw 29a, 29b, 29c which preferably extends parallel to the axis 22 to beyond the P2 plane. The shape of the polar claw is preferably identical to that of the flux collector, and the length of the polar claw is preferably slightly smaller than that of the magnet 43 of the rotor 40. Alternatively, the polar claws can extend over the entire length of the claw. length of the rotor magnet.

The sections of the flow collector and the claw may be different. In a variant not shown, the claw has a constant section in the form of an annular portion, whose angular aperture α 'with respect to the axis of the motor is substantially less than 60 °, while the section of the flow collector progressively increases from the left to the right, until presenting a maximum section at the level of the plane P2, section then equal to that of the claw. The sections of the flow collectors and claws may also have a shape other than that of an angular ring sector. The hub, the radial teeth, the flux collectors and the polar claws are made of a magnetic material of high permeability and low losses, for example by sintering of isolated grain iron powder. Preferably, the ferromagnetic portion of the first stator portion is made in one piece. The coils are then made by an automatic "flyer" type of technique, similar to that used for DC rotor motors with three-blade collector.

Preferably, the ends of each tooth have recesses 51a, 51b, 51c, 52a, 52b and 52c so as to facilitate the winding and to prevent it from overflowing from the right or left part of the hub.

The second stator portion 30 has three identical magnetic flux-collecting claws 31a, 31b, 31c, offset 120 ° in rotation about the axis of the motor and connected to a base 34 provided with a second bore for guiding the magnet. rotor shaft. This second part 30 of stator is made of ferromagnetic material.

The flux collecting claws preferably have the same shape as the polar claws and a length substantially equal to that of the magnet 43 of the rotor. They are offset by 60 ° with respect to the latter and are therefore interposed with them once the engine is assembled. For example, the polar claw 29a is surrounded by collecting claws 31a and 31b.

The polar claws and flux collecting claws define a cylinder of revolution C in which the rotor is housed. The radius of this cylinder is equal to the radius of the rotor magnet plus the gap distance between rotor and claw. To avoid magnetic leakage, it is important that a sufficient airgap spacing is provided between the polar claws and the flux-collecting claws, as well as between the polar claws and the base 34. For example, this spacing of The air gap is 5 mm for a 25 mm diameter motor. This spacing is obtained by the fact that the angular opening of the polar claws and collector claws is less than

60 ° and by the fact, that by its mechanical construction, once the engine assembled, the ends of the polar claws are kept at a distance from the base 34.

The second stator portion 30 is preferably made in one piece, by sintering ferromagnetic powder.

The three windings of the first stator part are powered by three-phase. This power supply has the effect of magnetizing the different subassemblies of the stator and creating at the rotor a rotating magnetic field. The structure makes it possible to have a substantially zero resultant flux in the hub 24 which can without a problem be traversed by a solid steel shaft and whose dimensions are therefore not fixed by magnetic stresses. Similarly, the resulting magnetic flux is substantially zero in the central portion of the base 34, the bore may without inconvenience contain a steel ball bearing.

The magnetic flux created by the coils is closed in the second stator part after interacting with the rotor and creating the motor torque.

In the embodiment described above, the axes of the coils are perpendicular to the axis of the motor. However, in Different embodiments of the motor, the axes of the windings can form another angle with the axis of the motor and even be parallel to the axis of the motor.

In a variant not shown, the claws may extend around the rotor helically forming a low helix angle with the axis of the motor. The magnetization sectors of the rotor may themselves have such a helical disposition.

The coils are essentially included inside the cylinder of revolution C. However, an alternative embodiment consists in giving, at least locally, a thickness greater than the polar claw in comparison with the thickness of the flux collector, for example for forming a protuberance as described by reference 14 in US Patent 6,847,149. In this case, a small portion of the windings may protrude radially from the cylinder. Similarly, we see in Figure 2 that a portion of the windings protrudes from the cylinder of revolution C.

By "substantially included", it must therefore be understood that advantageously at least 60% of the volume of the windings is included in the cylinder of revolution C. Preferably, at least 80% of the volume of the windings is included in the cylinder of revolution C. The windings can also be included entirely in the cylinder of revolution C.

The motor structure according to the invention makes it possible, in the same stator part, to magnetize each ferromagnetic claw differently in comparison with the other claws of the same orientation and consecutive in the direction of rotation of the rotor, in particular by means of the coil arranged around the ferromagnetic tooth to which the claw is connected by a flow collector. But the currents flowing in each winding occur in the flow through a claw. In absence of magnetic leaks, the flow in a claw is indeed equal and opposite to the sum of flows in the other two claws. Two consecutive claws can present the same magnetic flux at a particular time, but the third claw then has a double and opposite flow.

By "magnetize differently" is meant that the magnetic state of a claw is at all times different from that of all other claws of the same orientation and consecutive in the direction of rotation of the rotor, but not independent of the magnetic state of these other claws.

The fact of decomposing the stator in two parts nested one inside the other makes it possible to house, in each part, only one out of two of the claws seen by the rotor. The first stator portion therefore has sufficient space to accommodate the windings.

The structure is of three-phase type, and advantageously the fact that the resulting flux is zero in a common part of magnetic circuit.

With a magnetized rotor, the invention allows the realization of a synchronous type motor. The rotor described in the invention is made using a solid cylindrical ring whose magnetization is sectorized, but it is also possible to use a multipolar assembly made from magnets and rotor pole pieces, as described in US Pat. No. 6,847,149. The inner surface of the stator claws may then have recesses or protuberances as represented by reference 14 in this patent, in order to reduce the reluctant torque. One can also use a conductive rotor (eg squirrel cage) to achieve a three-phase induction motor (asynchronous motor). The invention has been described in the case of a motor but also applies to a generator operation (alternator).

The fact of producing an electrical machine with two parts of the stator interlocking and in which a single stator portion is magnetized by means of windings makes it possible to obtain a very powerful machine without complicating its structure, and in particular without complicating the structure of the structure. 'food. Indeed, all the windings to feed are concentrated in one place, on the same side of the rotor. Despite this, the magnetic circuit of the motor is closed in an efficient manner thanks to the claws of the second stator portion connected to the base forming short circuit. This ensures good engine performance by limiting the influence of magnetic leakage. The complete structure of the machine is particularly compact since the second part does not include windings. This second part also avoids the very strong reluctant torque that would be caused by the use of a single portion of the stator.

Preferably, the coils are disposed on one side of a plane perpendicular to the axis of the rotor and cutting the rotor at its elements 44, 45 in magnetic interaction with the stator, and the ferromagnetic base is disposed of other side of this plan. Nevertheless, it is also possible to arrange the coils and the ferromagnetic base on the same side of this plane, in particular by inserting the base between the rotor and the coils. The teeth on which the windings are arranged can then have a common hub with the base. A cylindrical support piece made of non-magnetic material not shown in FIG. 1 may advantageously be used to ensure the rigidity of the two stator parts, to guide the claws during assembly and to guarantee their good spacing. This piece also ensures the holding of the ends of the claws, so as to prevent them from tending to approach the rotor under the effect of magnetic attractions.

The use of a cylindrical support part allows a realization of the first stator part with separate parts, for example the part to the left of the plane P2 being made in a single sintered part, while the polar claws to the right of the plane P2 are independent sintered pieces.

Alternatively, a flux collector and a claw form a single sintered part, which is placed on a tooth 51. The whole of the means and teeth can then be produced by means of a pack of sheets parallel to the plane P2.

The invention is also applicable to the two-phase case, but it is then preferable to use a rotor shaft and / or non-magnetic bearings or bearings.

Claims

Claims:

An electric machine (10) comprising a rotor (40) movable about an axis (22) of the machine and a first stator portion (20) having first ferromagnetic claws (29a, 29b, 29c) extending around rotor defining a cylinder of revolution (C) coaxial with the rotor, the first part of the stator being active and comprising several windings (28a, 28b, 28c) for magnetizing differently the first ferromagnetic claws of the same orientation and consecutive in the direction of rotation of the rotor, characterized in that it comprises a second portion (30) of passive stator and comprising second ferromagnetic claws (31a, 31b, 31c) also delimiting the cylinder of revolution, interposed with the first ferromagnetic claws and connected to a ferromagnetic base (34).

2. Electrical machine according to claim 1, characterized in that the coils are arranged on one side of a plane intersecting the rotor and perpendicular to the axis (22) and in that the ferromagnetic base is disposed of the other side of the plane cutting the rotor and perpendicular to the axis.

3. Electrical machine according to claim 1 or 2, characterized in that the coils are essentially included in the cylinder of revolution.

4. Electrical machine according to one of the preceding claims, characterized in that the first stator part comprises three first claws and three coils and in that the second stator part comprises three second claws.

5. Electrical machine according to one of the preceding claims, characterized in that the axes of the windings are arranged orthogonally to the axis of the machine.

6. Electrical machine according to one of the preceding claims, characterized in that each first ferromagnetic claw is disposed in extension of a flux collector located at the first end of a ferromagnetic tooth connected to a ferromagnetic hub by its second end.

7. Electrical machine according to claim 6, characterized in that a first ferromagnetic claw and a flux collector form a single piece.

8. Electrical machine according to one of the preceding claims, characterized in that the ferromagnetic claws are held in position in at least one cylindrical non-magnetic piece.

9. Electrical machine according to one of the preceding claims, characterized in that the rotor comprises sectors (44, 45) radially magnetized or orthoradially magnetized sectors or short-circuiting conductive parts.