EP1714376A1

EP1714376A1 - Electromagnetic coupler

Info

Publication number: EP1714376A1
Application number: EP05717696A
Authority: EP
Inventors: Alex Romagny; Armando Fonseca
Original assignee: Renault SAS
Current assignee: Renault SAS
Priority date: 2004-01-29
Filing date: 2005-01-31
Publication date: 2006-10-25
Also published as: US20070096574A1; FR2865867A1; FR2865867B1; JP2007520188A; JP4709775B2; US7535143B2; WO2005076443A1

Abstract

The invention relates to an electromagnetic coupler for a motor vehicle. The inventive coupler consists of: a first electric machine having an axis A and comprising a first stator (50) bearing a first coil (52), an input rotor (20) and a first part (23; 157) of an output rotor (30); and a second electric machine comprising a second stator (40) bearing a second coil (100) and a second part (44; 177) of the output rotor (30). The input rotor (20) comprises an inner drum (77) which is spaced apart from the first part (23; 157) of the output rotor (30) and from the first yoke (60), while the second yoke (43) is spaced apart from the second part (44; 177) of the output rotor (30) by a second air gap (98; 106). According to the invention, the first coil (52) is wound onto the yoke (60) of the first stator (50) around axis A.

Description

The present invention relates to an electromagnetic coupler. In the application to a vehicle, an electromagnetic coupler makes it possible, for example, to transmit mechanical power between an internal combustion engine and the wheels of the vehicle, by continuously adjusting the torque and the speed on the latter. It also makes it possible, if necessary, to ensure conversion of driving or generating electromechanical energy in conjunction with means for storing electrical energy. It can thus be particularly useful in transmissions or hybrid electric traction systems of motor vehicles. As shown in FIG. 1, an electromagnetic coupler 10 conventionally comprises - an input shaft 12 intended to be mechanically coupled to a power source - an output shaft 14 intended to be mechanically coupled to at least one element to be driven - a casing 16, - and two electric machines. The first electric machine 1 comprises in this illustration:

an input rotor 20, of axis A, driven in rotation by the input shaft 12 and comprising a first armature 22, and

a crown 23 of internal magnets 24 magnetically coupled with the first armature 22 and carried by an output rotor 30 of axis A rotatably mounted on the casing 16 and in mechanical drive relation with the output shaft 14. The first armature 22 comprises coils 52 installed in its magnetic circuit 60, and electrically connected to a source of electrical energy, conventionally one or more batteries 32, by means of a first electronic unit 34. Conventionally, the first unit electronics 34 is shaped to transform the direct current leaving the battery 32 into a polyphase current whose phases supply the windings of the first armature 22, and vice versa. The coils of the first armature 22 are distributed in a known manner at the periphery of the input rotor 20 so that the polyphase current flowing therein can generate a first rotating electromagnetic field. The first electronic unit 34 is controlled by a control unit 36 designed to allow control of the "slip", that is to say of the difference between the rotational speeds of the input rotor 20 and the output rotor 30 , notably by modifying the frequency of the electric current. Depending on whether the slip is positive or negative, the first armature 22 is generator or receiver, that is to say that the transfer of energy between the output shaft 14 and the battery 32 takes place in the direction of a charging or discharging this battery, respectively. This transfer of energy, additive or subtractive, results in a variation of the speed of rotation of the output shaft 14. At synchronism, that is to say at zero slip speed, the input shafts 12 and output 14 are connected as they would be by direct mechanical coupling, the first armature 22 then receiving only the electric power necessary for magnetization, that is to say a direct current. The second electrical machine M2 comprises - a second machine stator 40, fixed to the casing 16 and carrying a second armature 42 comprising a plurality of coils 100 installed in its magnetic circuit 43, and

- A ring 44 of external magnets 45 of the outlet rotor 30 with which the second armature 42 is magnetically coupled. The coils of the second armature 42 are supplied with polyphase current via a second electronic unit 46 connected to the battery 32 so as to generate a second rotating electromagnetic field. The control unit 36 controls the second electronic unit 46 to control the additive or subtractive torque introduced by the machine M2 on the rotor 30 and therefore the output shaft 14. Conventionally, the magnets of the crowns 23 and 44 can for example be replaced by an asynchronous squirrel cage, or by a reluctant toothing, the design of the first and second corresponding armatures being adapted accordingly. Conventionally, the control unit 36 controls the electronic units

34 and 46 as a function of information on the angular position of the input 20 and output 30 rotors, and instructions for example provided by the driver of the vehicle. Position information can be provided by position encoders, not shown, or derived from other measurements. The two electric machines can cooperate so that the electric power resulting from the sliding of the first machine is used by the second electric machine to produce an additional mechanical torque on the shaft 14. The patent AU 5840173 describes different embodiments of electromagnetic couplers . By acting on the two electrical machines, it is understood that it is thus possible to adapt the transmission in speed and torque as desired and possibly exploit the potential of storing electrical energy. The supply of electrical energy to the first armature 22 conventionally requires sliding electrical contacts 48 between the first fixed electronic unit 34 and the rotating windings of the first armature 22. The sliding contacts 48 represent an integration constraint in terms of topology, in volume, in terms of compatibility with the physical environment and reliability, they also constitute a significant cost item. To avoid such sliding contacts, an electromagnetic coupler is known from US 6,380,653, the first armature 22 of which comprises a stator from the first machine, or “first stator 50” of axis A, fixed, and carrying coils 52 (see FIG. 2) and an input rotor 20 without winding, consisting of a cylindrical suppσrt provided with ferromagnetic peripheral pads. The stator 50, fixed to the casing 16, is concentric with the input rotor 20 and separated radially from the latter by an additional air gap 54. The coils 52 of the first armature 22 are conventionally introduced into longitudinal peripheral notches, that is to say - Say extending along the axis A, formed on the surface of the first stator 50, according to the usual embodiment of the armatures of multi-phase machines. The coupler described in US 6 380658, however, has a large size. In addition, its operation generates high Joule losses. There is therefore a need for an electromagnetic coupler which would not have these drawbacks. There is also a permanent need for an electromagnetic coupler which is simpler and less expensive to manufacture. The object of the invention is to provide an electromagnetic coupler capable of satisfying these needs. According to the invention, this object is achieved by means of an electromagnetic coupler, in particular for a motor vehicle, comprising - a first electric machine comprising a first stator of axis A carrying at least a first coil wound on a first fixed yoke, and being able to be coupled by magnetic induction with a first part of an output rotor movable in rotation along the axis A relative to said first stator, said coupling being carried out through an internal drum, movable in rotation along the axis A relative to said first stator and said first part and radially separated from said first part and said first cylinder head by a first air gap and an additional air gap, respectively - a second electric machine of axis A comprising a second stator carrying at least a second coil wound on a "second yoke" having the form of a second magnetic circuit or a yoke, and can nt be coupled by magnetic induction with a second part of said output rotor via a second air gap, The electromagnetic coupler according to the invention is remarkable in that said first coil is wound on said first yoke around said axis A of said first stator. As will be seen in more detail in the following description, the electromagnetic coupler according to the invention allows good electromagnetic exploitation of space as well as a significant gain on the Joule losses in the winding of the first armature, losses which are a major challenge both thermally and in terms of energy consumption. According to other preferred characteristics of the invention,

- Said first cylinder head is substantially annular with axis A and has a U-shaped cross section, the first and second wings of said first cylinder head ending in first and second surfaces spaced from said inner drum by said additional air gap;

- Said first coil is wound in a groove of said first yoke and does not protrude outside said groove; - Said second annular coil is wound around the axis A, preferably in a groove of said second cylinder head without protruding outside said groove;

- Said second cylinder head is substantially annular with axis A and has a U-shaped cross section whose first and second wings have a regularly crenellated profile;

- or, as a variant, said second cylinder head is substantially annular with axis A and has a U-shaped cross section, the first and second wings of said second cylinder head being extended by first and second sets of claws, respectively, arranged alternately, without contact with each other, facing and separated from said second part of said outlet rotor by said second air gap;

- Said input and output rotors are inserted one inside the other;

- Said input rotor is at least partially covered with a hoop made of a magnetic material of the Fe-17.5Cr-0.5C type; - Said hoop is made by rolling on the field of a sheet metal strip of said magnetic material or by spiral flat winding of a sheet of said magnetic material, the turns of said winding being electrically isolated from each other;

- Said electromagnetic coupler comprises first and second adjacent wafers each comprising at least one first coil wound, around the axis A, on a first fixed yoke, said first yokes of first and second wafers being separated by a magnetic decoupling space;

- Said electromagnetic coupler has first and second adjacent wafers and said output rotor has a magnetic decoupling space disposed between said first and second wafers, in a plane substantially perpendicular to the axis A;

- A cooling circuit is arranged in said decoupling space. - Said second part of said output rotor comprises an outer ring of magnetic studs, facing and separated from said first and second wings of said second cylinder head by said second air gap. According to other preferred characteristics of a first embodiment of the invention,

- Said inner drum comprises first and second coaxial plates of axis A, pierced in their centers by first and second holes delimited by first and second interior surfaces, respectively, and carrying first and second sets of claws extending to ta periphery desdtts first and second plates, respectively, said first and second plates being shaped and arranged relative to each other so that the claws of said first and second plates are arranged alternately, without contact with each other , opposite and spaced from said first part of said outlet rotor, said first and second interior surfaces being opposite and spaced from said first and second wings of said first cylinder head, respectively;

- Said first part of said output rotor comprises a crown of inner magnets, magnetized radially, with alternating polarities, and arranged opposite and spaced from said claws; - Said second part of said outlet rotor comprises a ring of facing external magnets and spaced from said second cylinder head;

- The number of said exterior magnets is equal to the number of said interior magnets, said exterior and interior magnets being arranged with the same direction of magnetization; - Said hoop has, above a zone separating two said adjacent claws, an electromagnetic permeability lower than that which it presents above said adjacent claws;

- Said first cylinder head and / or said first plate and / or said second plate and their claws are made of a composite magnetic material of the "iron powder" type, or in English "Soft Magnetic Composites"; According to other preferred features of a second embodiment of the invention, - Said inner drum comprises first and second toothed rings, coaxial with axis A, pierced in their centers by first and second holes delimited by first and second interior surfaces, respectively, and carrying first and second sets of teeth, respectively , said first and second toothed rings being shaped and arranged with respect to each other so that the teeth of said first and second toothed rings are arranged opposite and separated from said first part of said outlet rotor, said first and second interior surfaces facing and apart from said first and second wings of said first cylinder head, respectively;

- Said first part of said output rotor has an inner ring of facing magnetic pads and spaced from said teeth;

- Said inner ring has as many magnetic studs as said first gear or said second gear has teeth;

- Said magnetic pads extend axially so as to be able to simultaneously cover, at least in part, a tooth of each of said first and second toothed rings. Other characteristics and advantages of the present invention will appear on reading the description which follows and on examining the appended drawing in which

- Figure 1 schematically shows an electromagnetic coupler according to the prior art;

- ^' Figure 2 schematically shows an electromagnetic coupler seton US 6,380,653;

- Figure 3 schematically shows an electromagnetic coupler according to the invention;

- Figures 4 and 5 schematically show, in a two-phase configuration with two wafers, an electromagnetic coupler according to a first embodiment of the invention, in section in the plane of the sheet of Figure 3, and in quarter section along the plane PP of FIG. 4, respectively; - Figure 6 shows an exploded perspective view of part of the electromagnetic coupler shown in Figures 4 and 5;

FIGS. 7 and 8 schematically represent, in a two-phase configuration, an electromagnetic coupler of the type shown in FIG. 3, according to a second embodiment of the invention, in section in the plane of the sheet of FIG. 3, and in quarter section along the plane P'-P 'of Figure 7, respectively;

- Figures 9 and 10 schematically represent two variants of an electromagnetic coupler according to the invention. In the figures, identical references have been used to designate identical or analogous members. Figures 1 and 2 having been described in the introduction, reference is made to Figure 3. The electromagnetic coupler according to the invention shown in Figure 3 comprises for its electrical machine M1 three wafers G1, G2, and G3 that is say three units operating in a similar manner and cooperating with each other as a function of the electric currents supplying the coils of the armatures which they comprise. The wafers G1, G2 and G3 here form a three-phase system; their operation being similar, only the first wafer G1 is described below in detail. The first electric machine 1, of axis A, comprises a first stator

50 of axis A, fixed on the casing 16. According to the invention, a coil 52, called "centralized annular", is wound on a yoke 60 of first stator 50, or "first yoke 60", around the axis A. The cylinder head 60 being fixed on the casing 16, the electrical supply of the coil 52 is advantageously possible without sliding contact. The first cylinder head 60, which is substantially annular, has an annular groove, open radially towards the axis A, with a cross section in the shape of a "U". The groove of the first cylinder head 60 thus delimits a bottom 61 and first and second cylinder head wings, 62 and 64 formed by the two branches of the "U". The wings 62 and 64 extend substantially peφendicular to the axis A and end with first and second substantially cylindrical surfaces 66 and 68, respectively, of axis A (see Figure 6). As shown in Figures 4, 5 and 6, the annular coil 52 is wound in your groove of the first yoke SO, the turns of the coil 52 preferably not protruding outside said groove. The input rotor 20, mounted for rotation about the axis A on the casing 16, comprises a support 70 in the form of a disc, fixed in its center and peφendicular to the axis A on the input shaft 12 (figure 4) and an inner drum 72 of axis A, fixed to the periphery of the support 70. The inner drum 72 is common to the different wafers. It incorporates, for each wafer, first and second claw plates 74 and 76, respectively, of substantially the same shape, as shown in FIG. 6. The first and second plates, 74 and 76 respectively, have the form of discs of axis A, drilled in their respective centers by first and second holes, 80 and 81 respectively, substantially circular. The edges of the holes 80 and 81 delimit first and second interior surfaces, 82 and 83 respectively, cylindrical opposite the first and second cylindrical surfaces, 66 and 68 respectively, first and second wings, 62 and 64 respectively, of the first cylinder head 60. The additional air gap 54 radially separates the first and second interior surfaces, 82 and 83 respectively, on the one hand, and the first and second cylindrical surfaces, 66 and 68 respectively, on the other hand. The first and second plates, 74 and 76 respectively, carry first and second sets of claws comprising the same number of claws. The first and second claws, respectively, are called "first claws 78" and "second claws 84". The claws 78 and 84 extend substantially peφendicular to the plates 74 and 76. The first and second plates, 74 and 76 respectively, are nested one inside the other so that first and second external lateral faces, 88 and 89 respectively, said first and second claws, respectively, extend alternately, but without contact with each other, at the periphery of a cylindrical portion of the inner drum 72 facing the inner magnets 24 carried by the rotor of outlet 30. Preferably, the angular difference between two successive claws is substantially constant. The plates 74 and 76 are held integral with one another and with the support 70 by means of a non-magnetic binder 86, for example a plastic overmolding. The yoke 60 and the plates 74 and 76 are made of a magnetically conductive material, preferably electrically resistive. In fact, in the sliding operating phases of the electromagnetic coupler, the flows circulating in these parts are alternating, and therefore generators of

Foucault. The traditional solution of "lamination" by juxtaposition of magnetic sheets is possible, but not very effective due to the three-dimensional circulation of the magnetic flux in the cylinder head 60 and the plates 74 and 76. This is why, preferably, the cylinder head 60 and your trays 74 and 76 are made of a magnetic composite material of the "iron powder" type, or in English "Soft Magnetic Composites" (SMC), like those offered for example by the companies Hôganâs in Sweden or Québec Métal Powder in Canada. To facilitate manufacturing, in particular in the case of large-scale constructions, the parts made of SMC "iron powder" can be segmented into smaller elements assembled later. Advantageously, the good tolerances obtained in the forming of SMC parts generally avoid the need for resumption of machining. As will be seen in more detail in the following description, the lateral faces 88 and 89 are intended to form, under the effect of the magnetic field generated by the coil 52, magnetic poles of opposite polarities. The low relative sliding speeds between the input and output rotors which often characterize a majority of the coupler operating cases, as well as the use of "iron powders" which allow operation at high frequencies, allow a multiplication the number of poles. Advantageously, the high torque performance of centralized armature structures are therefore well exploited. Preferably, the outer lateral faces 88 and 89 of the claws 78 and 84 are encircled by a hoop 90, which advantageously allows high rotational speeds of the input rotor 20. For this hooping, it is possible to use the solutions already known, for example the solutions implemented for machines with surface magnets where it is necessary to avoid in the air gap both the electrically conductive materials and those capable of inducing short- magnetic circuits (use of 5 carbon fibers ...). However, these solutions have the drawback of significantly increasing the air gap reluctance. Preferably, the hoop 90 is a magnetic material of composition Fe-17.5Cr-0.5C), for example of the type "YEP-FA1" sold by the company Hitachi. This material has a magnetic permeability of the order of 900 which can be reduced to less than 1.01 after local heat treatment. The hoop 90 is preferably produced by rolling "Slinky" (that is to say on the field) of a strip of sheet metal of this material on the outer surface of the inner drum 72 of the input rotor 20. A heat treatment is then applied to the zones whose permeability must be eliminated, in particular to the zones 15 separating a claw 78 and a claw 84 adjacent. Advantageously, such a hoop can have a significant thickness compared to a usual non-magnetic hooping while making it possible to effectively guide the magnetic field lines.

<V. As a variant, the hoop 90 may result from a flat spiral winding of a sheet of "YEP-FA1". To avoid the development of annoying eddy currents, the turns of this winding are electrically isolated from each other and the sheet metal strip is of a small width, suitable for limiting the eddy currents at the frequencies considered. As in the previous arrangement, the bands of the hoop are demagnetized according to the desired pattern. Preferably, a hoop wire with high mechanical strength is wound between the turns of this spiral winding in order to improve the efficiency of the hoop. According to the invention, the first armature 22 therefore comprises at least one fixed annular coil 52 and partly fixed magnetic conduction means, namely the first yoke 60, and partly mobile, namely the plates 74 and 76. 30 Le output rotor 30 includes a disk-shaped support 92, mounted for rotation about the axis A on the input shaft 12 and in drive relation with the output shaft 14 (FIG. 4), and a drum outside 94 of axis A, fixed to the periphery of the support 92. The outside drum 94, common to the different pancakes, is made of a ferromagnetic material preferably electrically resistive or laminated. The inner cylindrical surface 96 of the outer drum 94 carries a crown 23 of interior magnets 24 arranged so as to face the lateral faces 82 and 89 of the claws 78 and 84. The interior magnets 24 follow one another at regular space, the number of inner magnets 24 being equal to the total number of claws of the two plates 74 and 76. A first armature gap 98 or "first gap 98" separates the inner magnets 24 from the lateral faces 82 and 88 of the claws 78 and 84. The geometry of the pancakes is adapted to take account of the electrical phase shift between the electrical phases which supply their respective first armature windings. For example, in an embodiment where each claw of the wafer G1 is axially aligned with a claw of the wafer G2, the two inner magnet rings of these two wafers are angularly offset by an angle corresponding to the electrical phase shift of the two phases. Conversely, in an embodiment where the two inner magnet rings of the wafers G1 and G2 are not offset from each other, each inner magnet of the wafer G1 being axially aligned with an inner magnet of the wafer G2 , the two sets of claws of the two wafers are angularly offset by an angle corresponding to the electrical phase shift of the two phases. The second electrical machine M2 can be produced according to a known architecture. It basically includes a second armature 42, in the form of a second stator 40 fixed on the casing 16, comprising a magnetic αrcuit 43. The magnetic circuit 43 is an annular external yoke carrying notches opening inwards. It can also be designated below by "second cylinder head". The magnetic circuit 43 carries a set of polyphase coils 100. Conventionally, the coils 100 are introduced into axial peripheral notches 102 formed on the inner surface 104 of the magnetic circuit 43, according to the usual embodiment of the armatures of polyphase machines. The magnetic circuit 43 preferably comprises a stack of magnetic sheets. A second air gap 106 separates the internal surface 104 of the magnetic circuit 43 from a ring 44 of external magnets 45, spaced regularly from one another, and disposed on the external surface 108 of the external drum 94. Preferably, a hoop 110 is made, for example in the manner of the hoop 90 of the input rotor 20, to improve the fixing of the external magnets 45 on the external drum 94. The number of external magnets 45 may be the same or different from the number of internal magnets 24. Preferably, the number of exterior magnets 45 is equal to the number of interior magnets 24, the magnets 45 and 24 being placed opposite one another with the same direction of magnetization. The outer drum 94 can then be very reduced in thickness, or even disappear in favor of a simple non-magnetic ring ensuring the maintenance of the fused magnets and housed in recesses formed in this ring. This arrangement of the magnets, known as "through flow", is also possible with an asynchronous rotor with a cage without a cylinder head. It is also directly transposable in the variant of the invention with synchronous variable reluctance in which the outer drum 94 is provided with ferromagnetic studs, as shown in FIGS. 7 and 8, the description of which will be given below. To limit the magnetic couplings parasitic by leaks between neighboring wafers, a decoupling space without ferromagnetic material is preferably provided between two successive wafers at the level of the first U-shaped yokes of the first armature. Preferably, an annular cooling circuit 12 is arranged in this decoupling space. In an embodiment not shown, decoupling can also be carried out at the level of the external drum 94, for example by an annular magnetic break of axis A in a non-ferromagnetic material. A simple thinning of the drum 94, in the form of an annular groove of axis A formed between successive pancakes may also prove to be sufficient Advantageously, if a decoupling is provided at the drum 94, the two cylinder heads 60 of the two pancakes can be attached, without decoupling space, which optimizes the axial size of the electromagnetic coupler. Cooling means 114 can finally be arranged at the outer periphery of the second stator 40, as shown in FIG. 4. The operation with the electromagnetic coupler according to the invention shown in FIGS. 4 and 5 is as follows: The annular coil 52 is supplied with electrical energy via the first electronic unit 34. The circulation of electric current in the coil 52 produces a magnetic field whose field lines substantially follow the following circuit. The field lines are oriented substantially along the axis A in the bottom 61 of the "U" of the first cylinder head 60, then reoriented substantially radially in the wings 62 and 64 of the first cylinder head 60. They then cross substantially the surfaces 66 and 68 and the additional air gap 54, then enter the plates 74 and 76 through the first and second interior surfaces, 82 and 83 respectively. They then regroup in the first and second claws 78 and 84 of the plates 74 and 76, respectively. The field lines then follow the substantially axial direction of the claws 78 and 84, then straighten themselves out, substantially radially, by the external lateral faces. 88 and 89 of these claws. They then pass through the hoop 90, the first air gap 98, the magnets 24, then the outer drum 94. In the outer drum 94, the field lines coming from the two wings 62 and 64 are reoriented substantially tangentially, in a plane peφendicutary to the axis A and meet so as to form loops. The magnetic flux flows along these flanges, in one direction or the other depending on the direction of the electric current flowing in the coil 52. All the outer lateral faces 88 of the first claws are ho opolar. All the outer lateral faces 89 of the second claws are also zero sequence, but of a polarity opposite to that of the outer lateral faces of the first claws. The control unit 36 controls the first electronic unit 34 so as to circulate in the coils 52 an electric current whose frequency is adapted as required. In particular, to achieve synchronism, the control unit 36 supplies the first coil 52 with direct current. The magnetic poles established by the outer faces 88 and 89 of the claws 78 and 84 then rotate about the axis A only due to the rotation of the input rotor 20. When the coil 52 and the corresponding coils of the other wafers are supplied by polyphase alternating currents, their assembly generally forms the equivalent of a rotating field: the speed of this rotating field then corresponds to the sliding speed between the inner drum d inlet and outlet rotor. The product of the torque transmitted by the slip, positive or negative, corresponds to the generation or respectively to the absorption of an electromagnetic power. By adjusting the frequency and phasing of the electric currents flowing in the coils 52, the control unit 36 can therefore electrically modify the direction and the sliding speed of the output rotor 30 relative to that of the input rotor 20. According to the invention, this speed variation is advantageously possible without rotation of the magnetic field source, that is to say of the coils 52. The electrical supply of the coils 52 therefore does not require a sliding contad In addition , the cooling of the coils 52 is facilitated and makes it possible to have recourse to effective means favorable to compactness. If the electromagnetic coupler comprises only a single first coil 52, the torque transmitted to the output shaft 14 will include a significant drawing component.,. !! it is therefore preferable to use at least two wafers whose first coils are supplied with two-phase, the two phases being offset by 90 ° electrical. More preferably, the electromagnetic coupler comprises three wafers, the armatures of which are supplied with a three-phase electric current. The number of pancakes is however not limiting. Field lines following a three-dimensional circuit, the use of materials of the SMC type, in particular for the first cylinder head 60 and the plates 74 and 76, is particularly advantageous. The additional air gap 54 induces a parasitic reluctance, not very sensitive for embodiments with magnets of low permeability. Advantageously, a flared shape of the wings 62 and 64 towards the surfaces 66 and 68 makes it possible to reduce the parasitic reluctance without having to resort to prohibitive radial tolerances. The operation of the second electric machine M2 is conventional, as explained in the preamble. The polyphase supply of the coils 100 makes it possible to generate a rotating magnetic field controlled by the synchronism of the rotor of output 30. The current level and its phasing make it possible to adjust at will the amplitude and the sign of the torque created by the machine M2 on the output rotor 30. Of course, the electric power produced or consumed by the first machine M1 can be balanced with that respectively consumed or produced by the second machine M2 by adjusting the torque of 2. Under these conditions, there is no power exchange with the battery 32: the mechanical power introduced by the input shaft 12 is transmitted to shaft 14, near losses in the coupler. In a variant of the second machine M2, shown diagrammatically in a three-phase version in FIG. 9, the second armature can, like the first armature, include an annular winding of axis A, wound around a second annular yoke 164 with cross section U-shaped, the two substantially radial wings of which extend by first and second sets of claws, respectively arranged alternately, without contact with each other, facing each other and separated from the second part of the output rotor 30 by the second air gap 106. Unlike the claws of the first armature, the claws of the second armature, used to distribute the magnetic flux in the second air gap 106, are fixed. FIGS. 7 and 8 represent a second embodiment of the invention exploiting the principle of your variable reluctance with double salience both for your first electric machine M and for the second machine M2 \ In this second embodiment, the claw plates 74 and 76 of the first electric machine M1 ′ are replaced by first and second toothed rings, 150 and 152 respectively, of axis A, drilled in their centers by first and second holes delimited by first and second interior surfaces, 150 'and 152' respectively, axially aligned with the first and second wings of the first cylinder head 60, respectively 62 and 64. The first and second interior surfaces, 150 'and 152', opposite the first and second wings, respectively, are separated by the additional air gap 54. The toothed rings 150 and 152 are provided with first and second sets of radial teeth, 154 and 155. The teeth of each of the sets, in identical number, are regularly spaced. Crowns 150 and 152 are arranged and held perpendicular to the axis A by a binder 156, so that each tooth of the crown 150 is aligned axially with a tooth of the crown 52. The external drum 94 of the outlet rotor 30 comprises, instead of the crown of inner magnets 24, an inner ring 157 of magnetic studs 158 of iron powder, regularly spaced, in a number equal to the number of teeth of one of the toothed crowns 150 and 152. The teeth of the toothed crowns 150 and 152 are arranged opposite and separated from the inner ring 157 by the first air gap 98. Each stud 158 extends axially so as to be able to cover simultaneously at least in part, a tooth of each ring 150 and 152, then forming a magnetically conductive "arch" between these teeth. Preferably the toothed rings 150 and 152 are constituted by stacks of flat sheets peφendiculaïres with the axis A. In the second embodiment of the invention shown in FIGS. 7 and 8, your lines of the magnetic field generated by the coil 52 follow the following circuit: After having left the wings of the first yoke 60 and having crossed the first air gap 98, the lines of the magnetic field radially cross the teeth of the crowns 150 and 152, then loop axially in the studs 158. The drum interior 94 supporting the magnetic studs 158 therefore no longer necessarily exercises the function of magnetic yoke and can be chosen mainly for its mechanical strength. The second electrical machine M2 ′ comprises an annular coil, or “second coil” 162, of axis A, wound at the bottom of a second yoke 164 having a U-shaped cross section. The second yoke 164 has a bottom 166, preferably made of a composite magnetic material, and first and second breech wings, 168 and 170, respectively formed by the two wings of the "U". Preferably, the wings 168 and 170 are made up of stacks, along the axis A, of sheets extending peφendicular to the axis A. The wings 168 and 170 extend substantially perpendicular to the axis A and have, in section along a plane peφendicular to axis A (Figure 8) a profile regularly crenellated. The slots of the wings 168 and 170 constitute sets of first and second teeth, 172 and 173 respectively, and have the same number of teeth, each first tooth 172 being axially aligned with a second tooth 173. Preferably, the teeth 172 and 173 are provided, at least in part, over the height of the winding 162. Advantageously, the size of the second machine M2 ′ is reduced. The external drum 94 of the output rotor 30 comprises, in place of the ring 44 of external magnets 45, an external ring 177 of magnetic studs 178, preferably of iron powder, regularly spaced, in a number equal to the number of teeth of each of the wings 168 and 170. Each stud 178 extends axially so as to be able to cover simultaneously, at least partially, a tooth 172 of each wing 168 and 170. The second air gap 106 separates the outer crown 177 and the wings 168 and 170. Preferably, a hoop 180, preferably made of a demagnetisable material, is provided for externally encircling the magnetic pads 178. The pads 158 and 178 may consist simply of bundles of sheets. The electromagnetic coupler according to the invention shown in the figures

7 and 8 therefore have a double reluctance variable reluctance configuration with transverse extrusion of the flow by means of an unwound output rotor. Advantageously, such an electromagnetic coupler is less expensive to manufacture than that shown in FIGS. 4 and 5, in particular because the external drum 94 is no longer necessarily made of a magnetically conductive material. The thickness of the outer drum 94 between the pads 58 and 178 can be reduced, or even canceled by bringing these pads into contact, which, advantageously, gives the electromagnetic coupler additional compactness. The operation of the first machine M1 ′ is similar to that of your first machine M1 of the electromagnetic coupler shown in FIGS. 4 and 5. The operation of the second machine M2 ′ is similar to that of the first machine M1 \ The annular winding of the first and / or second coils is favorable to limiting the losses Joules, which represent the main losses of the coupler in its frequent operations in the vicinity of synchronism. This advantage is due in particular to the drcuiaire geometry which reduces the average length of winding of the windings, to a favorable effect of the structures with centralized armature, and also to the possibility of obtaining a high coefficient of filling. The filling coefficient designates the ratio between the volume of copper inside the cylinder head groove and the volume of this groove. Advantageously, limiting the Joule losses also makes it possible to limit the capacity of the means necessary for cooling the electromagnetic coupler. Advantageously, finally, the manufacture and assembly of annular windings are very simple and inexpensive. Of course, the present invention is not limited to the embodiments described and shown, provided by way of illustrative and nonlimiting examples. In particular, the position of the input and output shafts, the downward movement towards the output shaft 14 shown in FIGS. 1, 2 and 3, the shape of the claws or studs, the number of electrical phases, and the number of wafers per phase are not limiting. The relative position of the input and output rotors can be reversed, the input rotor becoming external and the output rotor becoming internal. A combination of the first machine M1 and the second machine

M2 \ or a combination of the second M2 machine and the first machine 1 \ are possible. The centralized armature structure with additional air gap can be used on various known principles. One can for example introduce in place of the crown 23 of magnets 24 an asynchronous cage. The structure of the second electric machine is also non-limiting: asynchronous, variable reluctance, etc. The input 20 and output 30 rotors are not necessarily arranged in the same transverse plane, but can be offset axially. Preferably, however, the inlet 20 and outlet 30 rotors are inserted one inside the other, the outlet rotor 30 being for example arranged around the inlet rotor 20. Advantageously, this arrangement gives the coupler good compactness. electromagnetic. Likewise, your geometry of the air gaps of the electromagnetic couplers shown is not limiting. The air gaps could no longer extend along a cylinder of axis A (so-called “radial” configuration of the air gaps), but in a plane peφendîulaire to the axis A (so-called “axial” configuration of the air gaps), or even according to others. mixed configurations. An axial configuration advantageously makes it possible to obtain air gaps of large surface area, subject to assembly convenience and the balancing of the axial forces. The relative position of the armature with respect to their respective air gaps may also be different from that described. A variant of particular interest is illustrated in FIG. 9. The position of the armatures with respect to their air gaps is reversed with respect to that which Us occupy in the variants represented in FIGS. 1 to 8. The first armature 22 has become external with respect to the first air gap 54, while the second armature 42 is on the contrary internal with respect to the second air gap 106. Consequently, the magnetic circuits corresponding to these air gaps are geometrically dissociated, one inside the machine, l other outside. Advantageously, the first and second stators, 50 and 40 respectively, can thus be joined. Mechanical integration is simplified and I get simplified cooling. Advantageously also, as shown in FIG. 10, this variant allows a movement output positioned on the side opposite to the motor source relative to the electromagnetic coupler. Of course, the application of the invention is not limited to the transmission of power between an engine and the wheels of a motor vehicle. The input shaft drive may or may not be direct. The input and output trees can reverse their roles.

Claims

1. Electromagnetic coupler, in particular for a motor vehicle, comprising - a first electrical machine comprising a first stator (50) of axis A carrying at least a first coil (52) wound on a first fixed cylinder head (60), and which can be coupled by magnetic induction with a first part (23; 157) of an output rotor (30) movable in rotation along the axis A relative to said first stator (50), said coupling being carried out by means of a drum interior (72), movable in rotation along the axis A relative to said first stator (50) and to said first part (23; 157) and spaced from said first part (23; 157) and said first cylinder head (60) by a first air gap (98) and an additional air gap, respectively, - a second electric machine of axis A comprising a second stator (40) carrying at least a second coil (100) wound on a "second cylinder head" (43; 164) having the shape of a second magnetic circuit (43) or of a yoke (164), and being able to be coupled by magnetic induction with a second part (44; 177) of said output rotor (30) via a second air gap (106), - an electronic unit (34) adapted to supply alternating current to said first coil (52) said coupler being characterized in that said first coil (52) is wound on said first yoke (60) around said axis A of said first stator (50 ).

2. Electromagnetic coupler according to claim 1, characterized in that said first cylinder head (60) is substantially annular with axis A and has a cross section in the shape of a "U", first (62) and second (64) wings of said first cylinder head (60) ending in first (66) and second (68) surfaces spaced from said inner drum (72) by said additional air gap (54).

3. Electromagnetic coupler according to any one of claims 1 and 2, characterized in that said second coil (162), annular, is wound around the axis A.

4. Electromagnetic coupler according to claim 3, characterized in that said second yoke (164) is substantially annular with axis A and has a U-shaped cross section whose first and second wings have a regularly crenellated profile.

5. An electromagnetic coupler according to claim 4, characterized in that said second part (177) of said output rotor (30) comprises an outer ring (177) of magnetic studs (178), facing and separated from the first (168) and second (170) wings of said second cylinder head (164) by said second air gap (98).

6. Electromagnetic coupler according to claim 3, characterized in that said second cylinder head (164) is substantially annular with axis A and has a cross section in the shape of "U", the first and second wings of said second cylinder head (164) , extending by first and second sets of claws, respectively, arranged alternately, without contact with each other, ^> facing and separated from said second part of said output rotor (30) by said second air gap (106).

7. Electromagnetic coupler according to any one of the preceding claims, characterized in that said second part of said output rotor (30) comprises a ring (44) of external magnets (45) facing and separated from said second cylinder head (43 ) by said second air gap (106).

8. Electromagnetic coupler according to any one of the preceding claims, characterized in that said input (20) and output (30) rotors are inserted one into the other.

9. Electromagnetic coupler according to any one of the preceding claims, characterized in that said input rotor (20) is at least in part covered with a hoop (90) made of a magnetic material of Fe-17.5Cr- 0.5C type.

10. An electromagnetic coupler according to claim 9, characterized in that said hoop (90) is produced by rolling on a strip of sheet metal of said magnetic material or by spiral flat winding of a sheet of said magnetic material, the turns of said winding being electrically isolated from each other.

11. Electromagnetic coupler according to any one of the preceding claims, characterized in that it comprises first (G1) and second (G2) adjacent wafers each comprising at least one first coil wound, around the axis A, on a first fixed cylinder head, said first cylinder heads of first (G1) and second (G2) wafers being separated by a magnetic decoupling space.

12.Electromagnetic coupler according to any one of the preceding claims, characterized in that it has first (G1) and second (G2) adjacent wafers and in that said output rotor (30) has a magnetic decoupling space arranged between said first (G1) and second (G2) wafers, in a plane substantially perpendicular to the axis A.

13. Electromagnetic coupler according to any one of claims 11 and 12, characterized in that a cooling circuit is arranged in said decoupling space.

14, electromagnetic coupler according to any one of claims 2 to 13, characterized in that said inner drum (72) comprises first (74) and second (76) coaxial plates of axis A, pierced in their centers by first and second holes (80) delimited by first (82) and second (83) interior surfaces, respectively, and carrying first and second sets of claws (78,84) extending at the periphery of said first (74) and second (76) trays, respectively, said first (74) and second (76) trays being shaped and arranged relative to each other so that the claws of said first (74) and second (76) trays are arranged in alternately. without contact with each other, facing and spaced from said first part (23) of said outlet rotor (30), said first (82) and second (83) interior surfaces being opposite and spaced from said first (62) and second (64) wings of said first cylinder head (60), respectively.

15. An electromagnetic coupler according to claim 14, characterized in that said first part (23) of said output rotor (30) comprises a crown of inner magnets (24), radially magnetized, with alternating polarities, and arranged opposite and separated said claws.

16.Electromagnetic coupler according to any one of claims 14 and 15, claim 7 applying, characterized in that the number of said exterior magnets (45) is equal to the number of said interior magnets (24), said exterior magnets (45 ) and interiors (24) being arranged with the same direction of magnetization.

17.Electromagnetic coupler according to any one of claims 14 and 15, claim 9 applying, characterized in that said hoop (90) has, above an area separating two said adjacent claws, a lower electromagnetic permeability to that which it presents above said adjacent claws. ' ^•

18-electromagnetic coupler according to any one of claims 14 to 17, characterized in that said first cylinder head (60) and / or said first plate (74) and / or said second plate (76) are made of a composite magnetic material of type "iron powders", or in English "Soft Magnetîc Composites".

19.Electromagnetic coupler according to any one of claims 2 to 13, characterized in that said inner drum (72) comprises first (150) and second (152) toothed rings, coaxial with axis A, pierced in their centers by first and second holes delimited by first (150 ") and second (152 ') interior surfaces, respectively, and carrying first and second sets of teeth, respectively, said first (150) and second (152) toothed rings being shaped and arranged I with respect to each other so that the teeth of said first and second toothed rings are arranged opposite and spaced from said first part (72) of said outlet rotor (30), said first (150 ') and second (152') interior surfaces being opposite and spaced from said first (62) and second (64) wings of said first yoke (60), respectively.

20. An electromagnetic coupler according to claim 19, characterized in that said first part (72) of said output rotor (30) has an inner ring (157) of magnetic studs (158) facing and spaced from said teeth.

21. An electromagnetic coupler according to any one of claims 19 and 20, characterized in that said inner ring (157) comprises as many magnetic studs (158) as said first toothed ring (150) or said second toothed ring (152) comprises teeth.

22.Electromagnetic coupler according to any one of claims 19 to 21, characterized in that said magnetic pads (158) extend axially so as to be able to simultaneously cover, at least in part, a tooth of each of said first (150) and second (152) toothed crowns.