EP2102965A1

EP2102965A1 - Rotating electric machine, in particular for the starter of an automotive vehicle

Info

Publication number: EP2102965A1
Application number: EP07858757A
Authority: EP
Inventors: Jean Sébastien Metral; Nicolas Labbe; Benoit Dupeux; Stéphane PLAIDEAU
Original assignee: Valeo Equipements Electriques Moteur SAS
Current assignee: Valeo Equipements Electriques Moteur SAS
Priority date: 2006-12-15
Filing date: 2007-11-30
Publication date: 2009-09-23
Also published as: US9130418B2; US20160065008A1; US20100127590A1; WO2008074954A1

Abstract

The invention relates to a DC electric rotating machine mainly for the starter of an automotive vehicle, said machine including: a stator having a magnetised structure with permanent magnetisation and extending along the circumference of the stator; a rotor; a set of brushes adapted for the electric supply of the rotor y switching the electric current in sections of the rotor; the machine being characterised in that the magnetised structure (5) of the stator includes at least one sector, between two consecutive magnetic poles (N; S) of said structure, having a magnetisation vector that varies in an essentially sinusoidal manner upon displacement on the stator circumference, and in that the angular deviation of the neutral line is selected so as to improve the switching during the operation of the machine.

Description

Rotating electric machine, particularly for a motor vehicle starter

The present invention relates in particular to a rotating electrical machine, in particular for a motor vehicle starter.

EP-B1 -985 334 discloses a starter comprising a stator provided with a plurality of magnetic poles disposed on an inner circumferential surface of a cylinder head. Each magnetic pole is formed by a permanent ferrite magnet magnetized so that the north and south poles appear radially. Auxiliary magnets may be provided between the aforementioned magnets. These auxiliary magnets are made of ferrite and magnetized so that the north and south poles appear circumferentially. Space is provided between each auxiliary magnet and the cylinder head. Such an arrangement reduces magnetic leakage. It has been found that a strong magnetic reaction of armature in a DC brushed electric machine, in particular in a starter having a magneto-motor force (fmm) of great intensity at very low voltage and in power greater than 1 kW, can cause a decrease in performance of the machine. In some cases, an angular offset of the brushes and / or a compensating winding or switching aid are used to overcome the effects related to the armature reaction. The angular offset of the brushes is optimal only for a predetermined electric current Moreover, the above-mentioned winding is generally bulky.

Furthermore, the article entitled The Application of Halbach Cylinders to Bruhless AC Servo Motors, K. Atallah and D. Howe, IEEE Transactions On Magnetics, Vol. 34, No. 4, July 1998, a 'Brushless' type machine in which the variation of induction with respect to the electric angle in the air gap is sinusoidal. The article 'New concept of permanent magnet excitation for electrical machines. Analytical and numerical computation, M. Marinescu and N. Marinescu, IEEE Transactions On Magnetics, Vol. 28, No. 2, March 1992, deals with to magnetization in a machine of the 'Slotless' type, the magnetic excitation being either on the rotor or on the stator of the machine.

It is known, in a motor vehicle starter, to make a stator, or inductor, by sticking permanent magnets on a stator yoke. Bonding permanent magnets can in some cases be difficult to implement. It is also known to fix permanent magnets on the yoke using staples, each adapted for a single permanent magnet. Patent Application EP 1 035 629 and US Pat. No. 6,465,925 describe examples of staples for holding auxiliary magnets between main magnets. US Patent 4,707,630 teaches maintaining permanent magnets against a cylinder head using a cylinder made of sheet steel bearing against an inner circumference of the permanent magnets.

One of the aims of the invention is to reduce the effects of the armature magnetic reaction. Another object of the invention is to facilitate the attachment of magnets in a starter stator.

The object of the invention is, according to one of its aspects, a rotating electric machine with direct current, in particular for a starter of a motor vehicle, the machine comprising: a stator, or inductor, comprising a magnetized structure with permanent magnetization, extending along a circumference of the stator,

a rotor, or induced,

a group of brushes arranged to allow the electric supply of the rotor by switching the electric current in sections of the rotor, the machine being characterized in that the magnetized structure of the stator comprises at least one sector having a magnetization of direction different from radial and orthoradial directions of the stator.

The invention as defined above allows in particular to achieve the magnetized structure with two or more angular transitions between two consecutive magnetic poles of the machine. The magnetization direction can vary in a relatively progressive way when one moves on the circumference of the magnetized structure.

The applicant has unexpectedly found that such a magnetized structure can increase the torque and the mass power of the machine, as well as reduce or even substantially cancel the displacement of the magnetic neutral line when the armature current increases. , and thus substantially cancel the effects. The magnetic neutral line is defined as the place where the induction vanishes between two consecutive poles of the inductor.

Thanks to the invention, it is thus possible not to resort to a compensating winding and / or switching aid, or an angular offset of the brushes.

The invention may also make it possible to improve the switching and to limit the wear of the brushes and the vibro-acoustic radiation of the machine.

The angular transitions further enhance the mechanical stability of permanent magnets of the magnetized structure.

Although the aforementioned articles Attallah et al and Marinescu et al describe a magnetization with several angular transitions between the magnetic poles, their teaching is limited to the case of machines in which the variation of induction with respect to the electric angle is ideally sinusoidal. . However, in a brush machine, it is generally accepted that the variation of the induction with respect to the electrical angle must be close to a trapezoidal shape with a large plate, so that the induction is maximum on a angular range as wide as possible.

Therefore, there is a prejudice, overcome in the invention, according to which the teaching of the aforementioned articles Attallah et al and Marinescu et al is not suitable for a broom machine.

Preferably, the sector with a magnetization direction different from radial and orthoradial directions extends over an electrical angle greater than 10 °, in particular 20 °, or even 30 ° or 40 °. The electric angle corresponds to an angle actually measured within the machine, also called the mechanical angle, multiplied by the number of pairs of poles of the machine, which amounts to considering any machine as a juxtaposition within the same set of several elementary machines to a single pair of poles.

Advantageously, the direction of magnetization, in the magnetization sector of direction different from radial and orthoradial directions, forms with the orthoradial direction of the stator an angle of, for example, between 5 ° and 85 °, in particular between 10 ° and 80 °, or between 20 ° and 70 ° or between 30 ° and 60 °.

In an exemplary implementation of the invention, the magnetization within the magnetized structure has a non-parallel direction to itself when moving on a tower of the stator.

If desired, the direction of magnetization within the magnetized structure, with respect to a radial direction, varies without angular jump greater than 90 °, in particular without angular jump greater than or equal to 45 °, when moves on the circumference of the stator. The magnetized structure of the stator can be arranged against a yoke and have a magnetization chosen so that the magnetic field generated by the magnetic structure outside thereof, and measured in the absence of the yoke, is more weak that the generated field inside the magnetized structure, the magnetic energy outside the magnetized structure being in particular less than 30% or 20% of the magnetic energy inside the structure, the magnetic energy outside the structure, measured in the absence of the yoke, being notably substantially zero.

Advantageously, between two consecutive magnetic poles of the magnetized structure, the angle between the direction of magnetization of the structure and a radial direction of the stator varies monotonously, that is to say this angle varies in increasing or decreasing manner. when moving from a magnetic pole to a next pole.

This allows in particular to concentrate the magnetic energy to the air gap of the machine. In an exemplary implementation of the invention, the magnetized structure of the stator comprises a plurality of permanent magnets, at least one of the magnets having, in a central region following a circumference of the stator, a magnetization of direction of magnetization different from radial and orthoradial directions.

For example, the magnetized structure of the stator may comprise a plurality of permanent magnets, at least one of the permanent magnets having at all points a magnetization of magnetization direction different from radial and orthoradial directions.

If desired, this permanent magnet has a direction of magnetization which is substantially parallel to itself at any point of the magnet. In an exemplary implementation of the invention, the magnetized structure of the stator comprises at least two permanent magnets defining two consecutive magnetic poles of the magnetized structure and this structure further comprises two permanent magnets interposed between said two magnets defining the poles. The magnetized structure may have, if appropriate, a thickness, measured in a radial direction of the magnetized structure, substantially constant when moving circumferentially from a magnetic pole of the structure to a next pole.

Alternatively, the magnetized structure may have a thickness that varies as one travels circumferentially from a magnetic pole of the structure to a next pole.

The magnetized structure may for example comprise permanent magnets of different thicknesses.

In an exemplary implementation of the invention, the magnetized structure is devoid of interrupted zone having an electric angle opening greater than 1 °, in particular 2 ° or 5 °. The interrupted zone corresponds for example to the presence of a tab of a support of the magnetized structure inserted in a radial slot of this structure. This tongue defines an air gap between two permanent magnets of the magnetized structure. In an exemplary implementation of the invention, the orientation of the magnetization direction within the magnetized structure varies between two poles. consecutive magnetic circuits, substantially discontinuously or, alternatively, continuously.

The machine according to the invention can be of the type two or four poles, or preferably six poles or more. The magnetized structure may comprise a number of permanent magnets strictly greater than the number of poles of the machine, in particular greater than or equal to twice the number of poles.

For example, the machine can be of the six-pole type and the magnetized structure comprise 24 permanent magnets. Alternatively, the magnetized structure comprises a number of permanent magnets less than or equal to the number of poles of the machine, being in particular equal to half the number of poles.

For example, the machine may be six-pole type and the magnetized structure have three permanent magnets each extending at an angle of about 120 °.

Where appropriate, the magnetized structure comprises at least one permanent magnet made of NdFeB, especially sintered. Alternatively, the magnetized structure comprises at least one magnet made of ferrite.

The subject of the invention is also a rotating electric machine with direct current, in particular for a starter of a motor vehicle, the machine comprising:

a stator comprising a magnetized structure with permanent magnetization, extending along a circumference of the stator,

- a rotor, - a group of brushes arranged to allow the power supply of the rotor by switching the electric current in sections of the rotor, the machine being characterized in that the magnetic structure of the stator comprises at least one sector, between two consecutive magnetic poles of this structure, having a magnetization vector varying substantially sinusoidally when moving on the circumference of the stator. The sinusoidal shape of the magnetization makes it possible to obtain a lower sensitivity to the armature reaction and to increase, if necessary, the torque developed by the machine.

Advantageously, the angular offset of the neutral line is chosen so as to improve the switching during operation of the machine, by actively accelerating the current in the rotor during inversion.

The realization of the angular offset, optionally relatively strong, can be better controlled, particularly with respect to the case of a radial direction magnetization, because this angular offset is performed along a substantially linear or locally linear induction law

In an exemplary implementation of the invention, the angular offset of the neutral line may in particular be greater than 15 ° electrical or 20 ° electrical.

The magnetization vector within the magnetized structure may, if desired, vary substantially sinusoidally over the entire circumference of this structure.

As a variant, the magnetized structure comprises at least one sector having a magnetization vector that varies in a non-sinusoidal manner, for example with a radial direction in the sector, this sector extending in particular at an electrical angle greater than 10 °, in particular 20 °.

If necessary, the machine forms a starter motor vehicle with a strong armature reaction.

The electric machine may comprise a gearbox.

The invention makes it possible, thanks to a gain in torque, to reduce the rotational speed of the commutator of the machine, for the same operating point of the torque, which ensures a longer time for switching and consequently a reduction in losses and electrical arcing (sparking) of brushes and collector.

In addition, still thanks to the invention, because of the reduction of the amplitude of the electric arcs, by the improvement of the commutation, it is possible to limit the electromagnetic disturbances conducted and radiated, which is particularly advantageous concerning the electromagnetic compatibility (EMC) of electrical and electronic equipment (on board a vehicle or not) with the electric machine.

The invention also relates, independently or in combination with the foregoing, to a rotating electrical machine, particularly for a motor vehicle starter, of the N magnetic pole type (N being an integer), comprising a stator, or inductor, comprising:

a plurality of permanent magnets, the number of magnets being in particular strictly greater than the number N of poles of the machine, at least one support integrally carrying the permanent magnets.

Thanks to the invention, several magnets can be secured to the support before fixing the assembly thus obtained on the rest of the machine. It is thus possible to previously form a unitary assembly formed by the support and the permanent magnets and then bring this assembly against the stator yoke. The manufacture of the electric machine can thus be simplified.

In addition, if desired, the invention may make it possible to dispose permanent magnets on the support substantially adjacent two by two. Permanent magnets can be in contact two by two, with no space between them. Alternatively, a small gap, or gap, is formed between two consecutive magnets.

In an exemplary implementation of the invention, the support is arranged to maintain the permanent magnets at at least one of their axial ends, for example at their two opposite axial ends.

For example, the support comprises a plurality of tabs arranged to hold the magnets at at least one of their axial ends.

At least one of the legs of the support can in particular be folded, for example by folding, on the permanent magnet to ensure the maintenance thereof.

In an exemplary implementation of the invention, the support is made in one piece. Alternatively, the support comprises at least two separate parts, at least one of which is arranged at one of the axial ends of the permanent magnets.

The support can, if desired, be deformable, in particular to be wound, and arranged to allow the establishment of magnets on the support flat, before winding thereof.

The support comprises, for example, a plurality of parallel branches extending in particular perpendicularly to a circumference of the support, each branch having at its two opposite ends lugs for holding the permanent magnets. These legs do not have to be folded on the magnets to ensure their maintenance. The support may comprise hinge portions having a reduced width. These hinge portions facilitate the winding of the support once the magnets placed on the support.

This support may have cutouts leaving the outer surface of the magnets partially uncovered.

In another exemplary implementation of the invention, the support is preformed so as to have an annular or cylindrical shape before the establishment of permanent magnets.

The support may comprise a plurality of tongues, each interposed between two consecutive permanent magnets, to hold them correctly both radially and angularly. A small air gap is then formed between two consecutive magnets.

The support is made for example at least partially of sheet metal, for example by folding the sheet. The support may for example be formed by a metal strip folded flat to give it an annular shape. This way of making it possible to avoid losses of material for example following a cutting. Alternatively, the support can be made by cutting and stamping a sheet.

When the support comprises a cylindrical wall extending in an axial direction of the stator and against which the permanent magnets come into abutment, this cylindrical wall, for example of sheet metal, can serve as a shell for the passage of the magnetic flux and allow to reduce, if necessary, the thickness of the cylinder head.

In an exemplary implementation of the invention, at least one of the permanent magnets has an orthoradial direction magnetization. At least one of the magnets may have a direction magnetization different from the radial and orthoradial directions of the stator.

If desired, the support carries a plurality of radial magnetization direction main magnets and a plurality of auxiliary magnets each disposed between two consecutive main magnets, and having an orthoradial magnetization direction. Auxiliary magnets may for example have a thickness measured in a radial direction of the stator which is lower than that of the main magnets. These auxiliary magnets are for example separated from the cylinder head by a space corresponding substantially to the difference in thickness between main magnets and auxiliary magnets. The invention also relates to a method for manufacturing a rotating electrical machine as defined above, comprising the steps of setting up a plurality of permanent magnets on a common support and then bringing the assembly thus formed against a cylinder head of the stator.

The method may optionally comprise the steps of first winding the support and then put in place the permanent magnets on the wound support.

Alternatively, the method may include the steps of placing the permanent magnets on the support flat and then winding the support.

When the support comprises magnets holding tabs, these tabs can be folded on the magnets after placing them on the support.

Alternatively, the legs of the support are folded before introduction of permanent magnets on the support, these magnets being for example fixed by snapping on the support elastically deforming the tabs. The fixing of the support in the stator yoke is carried out for example by buttoning. Any other way of attaching the bracket to the cylinder head can be used.

The invention also relates, independently or in combination with the foregoing, to a rotating electrical machine comprising a stator comprising at least one permanent magnet and at least one support of the permanent magnet, the machine being characterized in that the support of the magnet comprises at least one lug and the magnet comprises at least one recessed or raised fixing portion arranged to cooperate with the bracket lug when the magnet is placed on the support.

The legs of the support make it possible in particular to maintain the magnets radially on this support and, where appropriate, in a circumferential direction as well.

The embodiment on the magnet of a recessed mounting portion allows in particular to receive the support leg, which can avoid the undesired presence of radial protuberances that prevent the correct mounting of the rotor in the stator.

The electric machine comprises a rotor, and said at least one permanent magnet has inner and outer faces, the inner face facing the rotor, the fixing portion of the magnet being in particular carried out, in particular entirely, on one of the inner and outer faces of the magnet.

In an exemplary implementation of the invention, the permanent magnet comprises recessed or raised fixing portions on both the inner and outer faces. The attachment portion is formed, if desired, by a notch on one side of the magnet.

The notch opens for example on an axial edge of the magnet.

This notch may have a substantially rectangular shape. Alternatively, the notch may have any other shape, for example substantially trapezoidal or arcuate. Advantageously, the bracket of the bracket has a shape substantially matching that of the notch, the tab being in particular substantially rectangular.

Where appropriate, the fixing portion comprises a bead protruding from one side of the magnet and the bracket lug may be arranged to cooperate with this bead to maintain the magnet on the support.

In an exemplary implementation of the invention, recessed or raised fixing portions are formed on one side only of the magnet, in particular an inner face. At least one of the magnets may comprise, if desired, a notch made on an axial portion of the magnet.

Preferably, the magnet is made by sintering, the fixing portion of the magnet being derived from the sintering.

The tab of the support is for example folded against the recessed portion or in relief of the magnet, this support being in particular made by folding a metal sheet.

The electric machine according to the invention can be arranged to operate at a maximum power of between 500 W and 2000 W, for example.

The invention will be better understood on reading the following detailed description, non-limiting examples of implementation of the invention, and on examining the appended drawing, in which:

- Figure 1 shows, schematically and partially, a motor vehicle starter according to an exemplary implementation of the invention,

- Figures 2 and 3 show, schematically and partially, two magnetized structures according to two examples of implementation of the invention,

FIGS. 4a and 4b are two graphs representing the variation of the vector potential as a function of the angle in the gap, respectively according to the invention and the state of the art,

FIG. 5 illustrates, schematically and partially, another example of a magnetized structure according to the invention, FIG. 6 represents, schematically and partially, a permanent magnet according to an exemplary implementation of the invention,

FIG. 7 schematically and partially shows a support for magnets according to FIG. 6; FIGS. 8 and 9 illustrate, schematically and partially, the placement of the support of FIG. 7 with the permanent magnets in a cylinder head; stator, two stages of assembly,

FIG. 10 represents, schematically and partially, a stator according to another example of implementation of the invention, FIG. 11 is a schematic partial view, in perspective, of a permanent magnet according to another exemplary embodiment. implementation of the invention,

FIG. 12 represents, schematically and partially, a support for magnets according to FIG. 11,

FIG. 13 illustrates, schematically and partially, the support of FIG. 12 with the permanent magnets fixed on it,

FIG. 14 represents, schematically and partially, a stator according to another example of implementation of the invention,

FIG. 15 is a diagrammatic and partial view, in perspective, of a support according to an exemplary implementation of the invention, flat before winding,

FIG. 16 represents, schematically and partially, a permanent magnet according to an exemplary implementation of the invention, to be arranged on the support of FIG.

FIG. 17 illustrates, schematically and partially, the support of FIG. 15, after winding,

FIG. 18 represents, schematically and partially, a support with permanent magnets placed on it, in accordance with another example of implementation of the invention,

FIG. 19 illustrates, schematically and partially, a stator according to another example of implementation of the invention, FIG. 20 represents, schematically and partially, a permanent magnet to be disposed in the stator of FIG. 19,

FIG. 21 illustrates, schematically and partially, the forces exerted on a permanent magnet of the stator of FIG. 19; FIGS. 22 and 23 show, schematically and partially, two other examples of magnets with notches,

FIG. 24 illustrates the sinusoidal magnetization within a magnetized structure according to another example of implementation of the invention,

FIG. 25 schematically represents the variation of the induction as a function of the angle, generated by a known magnetized structure,

FIG. 26 diagrammatically represents the variation of the induction as a function of the angle, generated by the magnetic magnetization structure illustrated in FIG. 24, and

FIGS. 27 and 28 illustrate two types of angular offset of the neutral line, for the magnetic magnetization structure illustrated in FIG. 24.

FIG. 1 shows very schematically a starter 1 for a motor vehicle combustion engine.

This DC starter 1 comprises, on the one hand, a rotor 2, also called an armature, rotatable about an axis X, and on the other hand, a stator 3, also called an inductor, around the rotor 2.

This stator 3 comprises a yoke 4 carrying a magnetized structure 5 with permanent magnetization.

The rotor 2 comprises a rotor body 7 and a coil 8 wound in notches of the rotor body 7. In the illustrated example, the rotating electric machine formed by the starter 1 is of the six-pole type.

The winding 8 forms, on either side of the rotor body 7, a front bun 9 and a rear bun 10.

The rotor 2 is provided, at the rear, with a collector 12 comprising a plurality of contact pieces electrically connected to the conductive elements, formed in the example in question by wires, of the winding 8. A group of brushes 13 and 14 is provided for the electrical supply of the winding 8, one of the brushes 13 being connected to the ground of the starter 1 and another of the brushes 14 being connected to an electrical terminal 15 of a contactor 17 via a wire 16. The brushes are for example four in number. The brushes 13 and 14 rub against the collector 12 when the rotor 2 is rotating, allowing the rotor 2 to be powered by switching the electric current in sections of the rotor 2.

The starter 1 further comprises a launcher assembly 19 slidably mounted on a drive shaft 18 and drivable in rotation about the X axis by the rotor 2.

A gear reduction unit 20 is interposed between the rotor 2 and the drive shaft 18, in a manner known per se.

Alternatively, the starter 1 may be of the 'Direct Drive' type, without a gearbox. The launcher assembly 19 comprises a drive element formed by a pulley 21 and intended to engage on a drive member of the combustion engine, not shown. This drive member is for example a belt.

The pulley 21 may be replaced by a gear element, in particular a gear wheel, for driving the combustion engine.

The launcher assembly 19 further comprises a freewheel 22 and a pulley washer 23 defining between them a groove 24 for receiving the end 25 of a fork 27.

This fork 27 is made for example by molding a plastic material.

The fork 27 is actuated by the switch 17 to move the launcher assembly 19 relative to the drive shaft 18, along the X axis, between a first position in which the launcher assembly 19 drives the combustion engine by through the pulley 21, and a second position in which the launcher assembly 19 is disengaged from the combustion engine. The switch 17 comprises, in addition to the terminal 15 connected to the brush 14, a terminal 29 connected via an electrical connection element, in particular a wire 30, to a power supply of the vehicle, in particular a battery.

FIG. 2 shows an example of a magnetized structure 5 according to a first embodiment of the invention.

In this example, the magnetized structure 5 comprises a number of permanent magnets, this number being equal to 24, strictly greater than the number of poles of the machine, which is equal to six.

Six of the 24 magnets have a radial direction magnetization, parallel to the arrow F1 illustrated in FIG.

These magnets 40a define the six poles of the machine, including three North N poles and three South poles S opposite the interior of the stator.

Between two consecutive magnets 40a are three permanent magnets, of which: a magnet 40b having a substantially orthoradial magnetization direction F2, perpendicular to the direction F1, and on either side of this magnet 40b, two magnets 40c having a direction of magnetization different from radial and orthoradial directions. In the example considered, the direction of magnetization is substantially uniform within each magnet 40c and forms with the radial direction F1 an angle A1 of about 45 °.

The magnets 40c thus each define a sector of the magnetized structure 5 having a direction of magnetization different from radial and orthoradial directions and having an angular aperture A2 of 15 °, which corresponds to an electric angle of 45 °.

As can be seen, the magnets 40c have at all points, in particular in a central region along the circumference F3 of the stator 3, a direction of magnetization different from F1 radial and orthoradial directions F2. The permanent magnets 40a-40c may have, as illustrated in FIG. 2, identical dimensions, so that the magnetized structure 5 has a thickness, measured in the radial direction F1, substantially constant when moving on the circumference F3.

Between two magnetic poles N and S, the magnetization direction of the magnetized structure 5 has four angular breaks, each of 45 °. The magnetization then has a number of angular transitions, between two poles N and S, equal to three.

Between two consecutive magnetic poles N and S of the magnetized structure 5, the angle between the direction of magnetization of the structure and the radial direction F1 varies in a monotonous and discontinuous manner, without angular recoil. This can make it possible to concentrate the magnetic energy towards the air gap, between the rotor 2 and the stator 3, corresponding to a significant reduction in the induction outside the magnetized structure 5 and a significant increase in the induction to inside.

In other words, the magnetic field generated by the magnetized structure outside thereof, and measured in the absence of the yoke 4, is smaller than the field generated inside the magnetized structure 5, the magnetic energy outside the magnetic structure being in particular less than 30% or 20% of the magnetic energy inside the structure, the magnetic energy outside the structure, measured in the absence of the breech, being especially negligible.

It has been found that a sufficient number of angular transitions, for example equal to three, makes it possible to ensure good mechanical stability of the magnets 40a-40c.

FIG. 4a shows the variations of the potential-vector (units: Wb / m) as a function of the angle in the gap, for several values of the current I and a number of angular transitions equal to two. These variations were obtained by finite element analysis.

It may be pointed out that the graph of FIG. 4a is in the form of a conventional two-dimensional representation making it easy to show any shift in the magnetic neutral line. Note in Figure 4a a virtual absence of displacement of the magnetic neutral line, which corresponds to the place where the induction is canceled between two consecutive poles, when the current I varies.

In other words, thanks to a number of angular transitions equal to or greater than two between consecutive magnetic poles, it is possible to substantially cancel the armature reaction, which is advantageous with regard to switching and electromagnetic coupling.

On the contrary, in a case illustrated in Figure 4b where the magnetized structure would be devoid of angular transition, it appears a displacement d of the magnetic neutral line.

It has been found that the invention makes it possible to increase the mass torque and power.

In the example considered, the permanent magnets 40a-40c are anisotropic sintered ferrite magnets. The magnetization of the magnets 40a-40c is carried out for example outside the cylinder head 4.

Alternatively, the permanent magnets 40a-40c may contain rare earth elements, being for example made of NdFeB.

In the example just described, the magnetized structure 5 comprises a number of permanent magnets 40a-40c greater than the number of poles N and S of the machine.

Alternatively, as shown in Figure 3, the structure 5 may include a number of permanent magnets less than the number of poles of the machine.

According to the exemplary implementation illustrated in FIG. 3, the structure 5 comprises three permanent magnets 41 each substantially having a cylindrical shape of a cylinder of revolution of angle A3 equal to 120 °.

These magnets 41 are for example made of NdFeB, with isotropic properties and having a sinusoidally varying directional magnetization when moving on the circumference F2 of the stator 3, along a magnet 41. If desired, it is possible to magnetize the magnets 41 inside the cylinder head 4.

In the example of FIG. 3, the number of angular transitions between two consecutive poles of the machine remains equal to three. Of course, it is not beyond the scope of the present invention when the number of angular transitions is different from three.

This number may, depending on the type of machine, be equal to two or greater than or equal to four. For example, there is shown in Figure 5 a magnetized structure 5 having six angular transitions between two consecutive magnetic poles.

The number of poles may be different from six, especially being greater than six. The machine may comprise for example 8 poles.

Alternatively, the machine may have a number of poles less than six, for example 2 or 4 poles. Various ways of fixing permanent magnets in the stator according to the invention will now be described.

FIGS. 6 to 9 illustrate different elements of a stator 50 according to an exemplary implementation of the invention, for example to equip the starter 1. Among these elements, there is a support 51 and a plurality of permanent magnets 52 intended to be mounted on the support 51.

As illustrated in FIG. 7, the support 51 comprises a cylindrical wall 53 of axis X of circular cross section.

This wall 53 has two opposite end edges 54, on each of which are connected a plurality of tabs 55 projecting towards the inside of the wall 53.

These tabs 55 arranged regularly on the corresponding edge 54 are 24 on each end of the wall 51 so as to allow the establishment of 24 permanent magnets 52. Each tab 55 comprises a first leg 57 perpendicular to the X axis extended by a second end branch 58 perpendicular to the first.

The support 51 is further provided with fasteners 59 arranged to allow fixing the support 51 on an inner surface 60 of a cylinder head 61 by buttoning.

Any other suitable means for fixing the support 51 on the cylinder head 61 may be used.

The support 51 can be made for example by rolling a metal sheet. This sheet may be made of magnetic material, for example steel.

Each permanent magnet 52 has inner 63 and outer 64 faces, as can be seen in Figure 6.

These faces 63 and 64 are defined by cylinder portions of revolution so that when all the magnets 52 are placed on the support 51 the faces 62 and 64 of the set of magnets form two substantially cylindrical concentric surfaces.

Each magnet 52 further comprises two lateral faces 65 converging towards the center of the support 51.

Recessed fixing portions 67 are formed on each face 63 of the permanent magnets 52 in order to allow these magnets to be held on the support 51 by means of the tabs 55.

In the example considered, each fixing portion 67 is formed by a notch opening on an axial edge 69 of the magnet 52.

The notch 67 has a substantially rectangular shape. Alternatively, the notch may have any other suitable shape.

The dimensions and shape of the notches 67 are selected so as to fit the leg 58 of the tabs 55 when the magnets 52 are placed on the support 51.

Thus once the magnets in place on the support 51, each leg 58 engages in a notch 67 of a magnet 52 and each leg 57 is applied against an axial end of the magnet 52. The magnets 52 are then held in the radial and circumferential directions, as illustrated in FIG. 8.

These magnets 52 are placed on the support 51 by snapping, namely by elastic deformation of the tabs 55. Alternatively, the tabs 55 can be folded by folding on the magnets

52, once these in place on the support 51.

The depth of the notches 67 is substantially equal to the thickness of the legs 58 of the tabs 55 so that these branches 58 do not project into the gap of the electric machine. The magnets 52 are made in particular by sintering, and the notches 67 are derived from this sintering. Alternatively, these notches 67 can be made by removal of material.

The solid cylindrical wall 53 can serve as a shell inside the cylinder head 61 to reduce the magnetic saturation and to reduce, if necessary, the thickness of the cylinder head 61.

In the example considered, the magnets 52 are placed on the support 51 in contact two by two. Thus, it avoids the presence of gap between lateral faces 65 of the magnets 52.

Of course, the number of permanent magnets 52 may be different from 24, depending on the needs.

For example, as illustrated in FIG. 10, the stator may comprise 8 permanent magnets 52 fixed on a support 51 provided with 8 pairs of legs 55.

Especially when it is expected to use a relatively small number of magnets, for example less than 8, each magnet then having larger dimensions, it may be advantageous to maintain each magnet using more legs 55. for example, each magnet 55 can be held by four legs.

In the example described above, the permanent magnets have notches. It is not beyond the scope of the present invention when one places on the support one or more permanent magnets devoid of a portion of recessed or raised fixing, in particular without notches 67 as described above.

FIG. 11 to 13 illustrates such an example of implementation of the invention, in which a plurality of identical permanent magnets 70, with no hollow or raised fixing portion, of which there are 24 in each case. described example, are placed on a support 71.

Each magnet 70 has radially inner 74 and outer 75 faces substantially in concentric cylinder portions, as well as lateral faces 76 converging radially inwardly. The support 71 is initially flat to allow the establishment of permanent magnets 70, as shown in Figure 12.

This support 71 comprises a plurality of branches 78 parallel to the axis X each having at opposite ends tabs 79 for holding the magnets 70. The tabs 79 extend perpendicular to the corresponding branch 78 and each have a substantially rectangular shape.

The support 71 is further provided with a plurality of tongues 80, perpendicular to the branches 78, each tab being interposed between two consecutive magnets 70, so as to maintain these magnets angularly and radially.

Due to the presence of these tabs 80, a small air gap separates two consecutive magnets 70. The magnetized structure formed by the magnets 70 is advantageously devoid of interrupted zone, corresponding to the gap, having an electric angle opening greater than 1 °, in particular 2 ° or 5 °. The number, the dimensions and the shape of the tabs 80 are chosen in particular according to the magnets 70 to be maintained.

The support 71 has portions 82 forming a hinge of reduced width and to facilitate the winding of the support 71 once the magnets 70 placed on it. The portions 82 are alternated with the branches 78. The support 71 is for example made by cutting and folding a strip of metal sheet. This support 71 has cutouts 83 leaving the outer face 75 of the magnets 70 partially uncovered.

Arms 85 are provided at one end of the support 71 to maintain the latter in the wound state.

These arms 85 are for example engaged in notches 86 made on tabs 79 at an opposite end of the support 71.

Alternatively, the support 71 can be arranged to be maintained in the wound state only by its implementation in the cylinder head. The example which has just been described may, without departing from the scope of the invention, be adapted to a number of magnets less than 24, for example 12, 8, 6, 4, 3 or 2.

In the examples described above, the support of the magnets is made in one piece, in particular sheet metal cut and folded. FIGS. 14 to 16 show different elements of a stator 90 according to an exemplary implementation of the invention, comprising a support 91 formed by two separate pieces 92.

Each piece 92 is made from a sheet metal strip folded flat to give this piece 92 an annular shape, as shown in FIG. 17.

Of course, the parts 92 may be made of other materials.

The outside diameter of the parts 91 is equal to the inside diameter of the cylinder head 94 in which the support 91 with permanent magnets 95 is put in place. Each piece 92 comprises a plurality of tabs 97 for holding magnets 95. These tabs 97 have, for example, a substantially rectangular shape.

Some of these tabs 97 extend radially and each interpose between two adjacent magnets 95 disposed on a circumference of the corresponding part 92. Other tabs 97 extend substantially along the circumference of the piece 92, facing two by two, to hold the magnets 95 in a radial direction.

The magnets 95 each comprise two pairs of notches 99 of substantially rectangular shape, arranged to receive the tabs 97 of the parts 92 when the magnets 95 are mounted on the parts 92, these being then disposed at the opposite ends of the magnets 95.

Two of the notches 99 are located on an outer face 100 of the magnet and the two other notches 99 on an inner face 101. These notches 99 open on end edges 102 of the magnet 95.

In the example considered, the magnets 95 are of two types. A first group 95a of magnets are called main magnets, which have a radial direction magnetization so as to define alternating north and south poles. A second group 95b of magnets 95 define auxiliary magnets, each being disposed between two main magnets, these auxiliary magnets having a substantially orthoradial directional magnetization.

Such an auxiliary magnet is shown in FIG.

The presence of auxiliary magnets reduces magnetic leakage.

The auxiliary magnets may have the same thickness, measured in the radial direction, as that of the main magnets.

Alternatively, the auxiliary magnets may have a thickness different from that of the main lovers. It is possible to position the auxiliary magnets so as to provide a space between these magnets and the cylinder head 94. In other words the auxiliary magnets are not pressed against this cylinder head 94.

The spacing between the auxiliary magnets and the cylinder head is advantageously determined by the positioning of the tabs 97 which hold these magnets. In a variant not illustrated, the magnets 95 may be arranged to have two or more angular transitions, as described above.

The parts 92 further include tabs 103 for securing these parts 92 to the cylinder head 94 by buttoning. Other suitable means of securing the support 91 may be used.

The parts 92 of the support 91 and the magnets 95 can form an independent assembly before fitting into the cylinder head 94, which can simplify assembly operations.

In the illustrated example, the electric machine has six poles. Possibly the tabs 97 which extend radially can be removed, and the rotation of the magnets 95 is maintained by the cooperation of the tabs 97 circumferential with the notches 99 of the magnets 95.

It is then possible to avoid the presence of gap between the main magnets and the auxiliary magnets, which can improve the efficiency of the electric machine.

In the example just described, the parts 92 are made by cutting and folding.

Alternatively, the parts 92 of the support 91 can be made by cutting and stamping, as illustrated in FIG. 18.

In the exemplary embodiment of FIG. 18, the support 92 carries an alternation of main magnets and auxiliary magnets 95.

The main magnets 95 may be devoid of notches 99, as illustrated in FIGS. 19 to 21. In this case, the maintenance of each main magnet 95 against the yoke 94 is obtained not thanks to circumferential lugs 97 but to the shape of the lateral faces 105 of the magnet 95.

As shown in FIG. 21, the faces 105 each have a flat portion 106 on which a tab 97 oriented substantially radially. The portions 106 and the tabs 97 are arranged so that these tabs 97 exert on the sides of the magnet 95 two stresses T1 giving a resultant stress T2 radial tend to apply the magnet 97 against the cylinder head. As illustrated in FIG. 19, the support 92 includes tabs 97 for holding the auxiliary magnets 95.

Of course, the invention is not limited to the implementation examples which have just been described.

In the case where it is desired to avoid the presence on the magnets of recessed or raised fixing portions, in particular notches, it is possible to provide, on the support of the magnets, tabs for applying solely on a inner side of the magnets, without holding tab applied on the outer face of the magnets. The legs of the support extend over a diameter smaller than the diameter inscribed in the set of magnets mounted on the support. This is to ensure that the rotor can always be mounted correctly in the stator.

Furthermore, at least one of the permanent magnet attachment portions may be formed, if desired, by one or more beads projecting from an inner or outer face of the magnet, the support holding tab being arranged to cooperate with this or these beads to ensure its radial and angular maintenance.

In another example of implementation of the invention, the support 51 mentioned above may be arranged to receive an alternation of main magnets and auxiliary magnets, respectively of radial and orthoradial magnetization directions.

The magnets holding tabs on the support may have a shape other than rectangular, for example trapezoidal.

In the examples illustrated in Figures 22 and 23, the permanent magnets 95 have notches 110 each extending on an axial portion 111 of the magnet.

In the example of FIG. 22, each notch 110 has a substantially rectangular shape, with an inclined slope selected so as to that a holding tab engaged in this notch allows a maintenance both radial and angular.

In the example of Figure 23, each notch 110 has a trapezoidal shape with the large base 112 located on an inner circumference, so as to provide both radial and angular support.

In a variant of Figure 6, it is possible to form notches on the side faces 65 of the magnets.

FIG. 24 shows a magnetized structure 5 according to another exemplary embodiment of the invention, having a magnetization vector within the magnetized structure 5 which varies substantially sinusoidally over the entire circumference of this structure 5.

Alternatively, the magnetization may have a sinusoidal profile only on certain sectors of the structure 5, and not on its entire circumference.

In the example considered, the magnetized structure 5 comprises six magnetic poles N and S.

Figure 26 illustrates the variation, as a function of the angle, of the fields Bn.no- load (vacuum induction), Bn.arm.reac (induction related to the armature reaction) and Bn. resuit (resulting induction of Bn.no-load and Bn.arm.reac), for the magnetized structure 5 illustrated in FIG. 24. The induction Bn. resuit is substantially sinusoidal, and the angular offset of the neutral line (where the induction vanishes) is about 5 °, as best seen in Figure 27.

In comparison, FIG. 25 illustrates these same fields for a magnetized structure with an exclusively radial magnetization. Bn induction. resuit substantially has a trapezoidal profile, and the angular offset of the neutral line is about 30 °, that is to say, much larger than in the invention.

Unlike the case of the exclusively radial magnetization where, under load, an electromotive force is produced in the direction of a degradation of the switching conditions (effect delaying the inversion of the current in the rotor, and therefore an increase of losses by arcs), it is possible, thanks to the invention, to satisfactorily compensate for the low degradation of these switching conditions due to a small angular offset. The invention can make it possible to introduce an additional angular offset so that the inversion of the current is accelerated, without the usual disadvantages of a radial magnetization.

Thanks to the invention, a more localized induction level is used to generate an electromotive force accelerating the inversion of the current, along a linear law associated with the local profile of a sinus, which allows to facilitate a robust definition of the electric machine, without the disadvantage of a significant loss of torque since a smaller angular offset is sufficient to switch centrally around the zero induction region. Furthermore, it is possible to impose a large angular offset to further improve the switching because the magnetized structure 5 according to the invention provides a 'torque reservoir' usable according to the needs of the machine, the invention allowing an increase in torque with the same quality and quantity of magnets. This angular offset can be chosen greater than 10 ° electrical, or 20 ° electric as in the example described (see Figure 28).

The invention further reduces iron losses in the armature because in sinusoidal induction the harmonic disadvantages are mitigated. Magnetic noise can be reduced as well.

Claims

claims

1. DC rotary electric machine, in particular for a starter (1) of a motor vehicle, the machine comprising:

a stator (3) comprising a magnetized structure with permanent magnetization, extending along a circumference of the stator,

a rotor (2),

- a group of brushes (13, 14) arranged to allow the electrical supply of the rotor by switching the electric current in sections of the rotor, the machine being characterized in that the magnetized structure (5) of the stator comprises at least one sector, between two consecutive magnetic poles (N; S) of this structure, having a magnetization vector varying substantially sinusoidally when moving on the circumference of the stator (3), and in that the angular offset the neutral line is chosen to improve the switching during operation of the machine.

2. Machine according to the preceding claim, characterized in that the angular offset of the neutral line is greater than 15 ° electrical or 20 ° electric.

3. Machine according to one of the preceding claims, characterized in that the magnetization vector within the magnetized structure varies substantially sinusoidally throughout the circumference of this structure.

4. Machine according to one of claims 1 and 2, characterized in that the magnetized structure comprises at least one sector having a magnetization vector varying non-sinusoidally, for example with a radial direction in the sector, this sector extending in particular over an electrical angle greater than 10 °, in particular 20 °.

5. Machine according to any one of the preceding claims, forming a starter motor vehicle, characterized in that it has a strong armature reaction.

6. Machine according to any one of the preceding claims, characterized in that it comprises a gearbox.

7. Machine according to any one of the preceding claims, characterized in that it is of the type six poles or more.

8. Machine according to any one of the preceding claims, characterized in that the magnetized structure comprises at least one permanent magnet made of NdFeB, especially sintered.

9. DC rotary electric machine, in particular for a starter (1) of a motor vehicle, the machine comprising:

a stator (3) comprising a magnetized structure with permanent magnetization, extending along a circumference of the stator, - a rotor (2),

- a group of brushes (13, 14) arranged to allow the electrical supply of the rotor by switching the electric current in sections of the rotor, the machine being characterized in that the magnetized structure (5) of the stator comprises at least one sector (40c) having a direction magnetization different from the radial (F1) and orthoradial (F2) directions of the stator.

10. Machine according to claim 9, characterized in that the sector with a magnetization direction different from radial and orthoradial directions extends over an electrical angle greater than 10 °, in particular 20 °.

11. Machine according to one of claims 9 and 10, characterized in that the magnetization direction in said sector (40c) magnetization direction different from radial and orthoradial directions forms with the orthoradial direction of the stator an angle understood by example between 5 ° and 85 °, especially between 10 ° and 80 °.

12. Machine according to any one of claims 9 to 11, characterized in that the magnetization within the magnetized structure (5) has a non-parallel direction to itself when moving on a lathe of stator.

13. Machine according to any one of claims 9 to 12, characterized in that the direction of the magnetization within the magnetized structure, with respect to a radial direction, varies without angular jump greater than 90 °, especially without angular jump greater than or equal to 45 ° when moving on the circumference of the stator.

14. Machine according to any one of claims 9 to 13, characterized in that the magnetized structure (5) of the stator is arranged against a yoke (4) and has a magnetization chosen so that the magnetic field generated by the magnetized structure outside the latter, and measured in the absence of the yoke, is smaller than the field generated inside the magnetized structure, the magnetic energy outside the magnetized structure being in particular less than 20% of the magnetic energy inside the structure.

15. Machine according to any one of claims 9 to 14, characterized in that between two magnetic poles (N; S) consecutive magnetized structure, the angle between the direction of magnetization of the structure and a direction radial stator varies monotonically when moving from a magnetic pole to a next pole.

16. Machine according to any one of claims 9 to 15, characterized in that the magnetized structure of the stator comprises a plurality of permanent magnets, at least one of the magnets (40c) having, in a central region following a circumference of the stator, a magnetization of direction of magnetization different from radial and orthoradial directions.

17. Machine according to any one of claims 9 to 16, characterized in that the magnetized structure of the stator comprises a plurality of permanent magnets, at least one of the permanent magnets (40c) having at any point a magnetization of direction of magnetization different from radial and orthoradial directions.

18. Machine according to any one of claims 9 to 17, characterized in that the magnetized structure of the stator comprises at least two permanent magnets (40a) defining two consecutive magnetic poles of the magnetized structure and in that this structure comprises in addition at least two permanent magnets (40b, 40c) interposed between said two magnets defining the poles.

19. Machine according to any one of claims 9 to 18, characterized in that the magnetized structure has a thickness, measured in a radial direction of the magnetized structure, substantially constant when moving circumferentially of a magnetic pole. from the structure to a next pole.

20. Machine according to any one of claims 9 to 19, characterized in that the magnetized structure (5) is devoid of interrupted zone having an electric angle opening greater than 1 °, in particular 2 ° or 5 °.

21. Machine according to any one of claims 9 to 20, characterized in that it is of the type six poles or more.

22. Machine according to any one of claims 9 to 21, characterized in that the magnetized structure comprises a number of permanent magnets strictly greater than the number of poles of the machine, in particular greater than or equal to twice the number of poles. .

23. Machine according to the preceding claim, being six-pole type, characterized in that the magnetized structure comprises 24 permanent magnets (40a, 40b, 40c).

24. Machine according to any one of claims 9 to 21, characterized in that the magnetized structure comprises a number of permanent magnets (41) less than or equal to the number of poles of the machine, being in particular equal to half the number of poles.

25. Rotating electrical machine, especially for a motor vehicle starter, comprising a rotor and a stator comprising at least one permanent magnet and at least one support of the permanent magnet, the machine being characterized in that the support of the magnet comprises at least one lug (55; 97) and the magnet (52; 95) has at least one recessed or raised fixing portion (67; 99) arranged to cooperate with the bracket lug when the magnet is placed in place on this support, and in that the at least one permanent magnet has inner and outer faces, the inner face facing the rotor, the fixing portion of the magnet being formed, in particular entirely, on the one of the inner (63; 101) and outer (100) faces of the magnet (52; 95).

26. Machine according to the preceding claim, characterized in that the fixing portion is formed by a notch (67, 99) formed on one side of the magnet.

27. Machine according to the preceding claim, characterized in that the notch opens on an axial end edge (69; 102) of the magnet.

28. Machine according to one of claims 26 and 27, characterized in that the notch (67; 99) has a substantially rectangular shape.

29. Machine according to any one of claims 26 to 28, characterized in that the tab (55; 97) of the support has a shape substantially matching that of the notch, the tab being in particular substantially rectangular.

30. Machine according to any one of claims 25 to 29, characterized in that recessed mounting portions or relief are performed on one side only of the magnet, including an inner face.

31. Machine according to any one of claims 25 to 29, characterized in that recessed mounting portions or relief are performed both on inner faces (101) and outer (100) of the magnet.

32. Machine according to any one of claims 25 to 31, characterized in that the magnet is made by sintering, the fixing portion of the magnet being derived from sintering.

33. Machine according to any one of claims 25 to 32, characterized in that the tab (97) of the support is folded against the recessed portion or in relief of the magnet.

34. A rotating electrical machine, in particular for a starter motor vehicle, of the type with N magnetic poles, comprising a stator (3) comprising: a plurality of permanent magnets (52; 70; 95), the number of magnets being strictly greater than the number of poles of the machine;

a support (51; 71; 91) integrally supporting all the permanent magnets of the stator.

35. Machine according to the preceding claim, characterized in that the support (51; 71; 91) is arranged to maintain the permanent magnets at at least one of their axial ends.

36. Machine according to the preceding claim, characterized in that the support comprises a plurality of tabs (55; 79; 97) arranged to hold the magnets at at least one of their axial ends.

37. Machine according to any one of claims 34 to 36, characterized in that at least one of the legs of the support is folded, in particular by folding, on the permanent magnet to maintain it.

38. Machine according to any one of claims 34 to 37, characterized in that the support (51; 71) is made in one piece.

39. Machine according to any one of claims 34 to 37, characterized in that the support (91) comprises at least two separate pieces (92), at least one of which is arranged at one of the axial ends. permanent magnets.

40. Machine according to any one of claims 34 to 39, characterized in that the support (71) is deformable, in particular to be wound, and arranged to allow the introduction of magnets on the support before winding of c it.

41. Machine according to the preceding claim, characterized in that the support (71) comprises a plurality of parallel branches (78) each having at its two opposite ends lugs (79) for holding the permanent magnets.

42. Machine according to any one of claims 34 to 41, characterized in that the support (51) is preformed so as to have a cylindrical shape before the establishment of permanent magnets.

43. Machine according to any one of claims 34 to 42, characterized in that the support comprises a plurality of tabs (80), each being inserted between two consecutive permanent magnets.

44. Machine according to any one of claims 34 to 43, characterized in that the support is made at least partially of sheet metal.