FR2886481A1 - Stator for e.g. alternator, has teeth cooperating with poles of rotor, and magnetically charged layer connecting two consecutive teeth, where layer is continuous layer connecting assembly of teeth and has preset thickness - Google Patents

Abstract

The stator has teeth (22) linked to yoke (36) and arranged between slots (23) receiving conductive units (21). The teeth cooperate with poles (12, 14) of a rotor, and a magnetically charged layer (39) connects two consecutive teeth, where the layer is a continuous layer connecting an assembly of the teeth and has a preset thickness. An air gap separates an external axial peripheral surface of the rotor from an internal axial peripheral surface of the stator. An independent claim is also included for an electrical rotating machine comprising a stator.

Description

2886481 1

  BACKGROUND OF THE INVENTION The present invention relates to a rotating electrical machine comprising a rotor and a stator.

  The invention relates more particularly to the stator of the rotating electrical machine.

  The invention finds applications in particular in the field of the automotive industry and, in particular, in the field of alternators and alternator-starters.

  State of the art A rotating electrical machine comprises a rotor and a stator on each of which can be realized an electric winding comprising conductive elements.

  The rotating electrical machine may be an alternator that transforms a rotational movement of the rotor into an electric current in the stator. The electric machine can also be a motor that transforms an electric current, passing through the rotor winding, into a rotational movement of the rotor. The machine can finally be reversible by transforming mechanical energy into electrical energy and vice versa.

  A stator of a rotating electrical machine conventionally comprises a body having: - a cylinder head; notches for receiving conductive elements; teeth, attached to the yoke and arranged between the notches, intended to cooperate with the poles of a rotor.

  Gold during its use, the rotating electrical machine creates a 2886481 2 annoying noise for the comfort of the user. Part of this noise comes from the magnetic and mechanical interactions of the rotor with the stator of the machine.

  To avoid these drawbacks, the document US Pat. No. 3,869,629 discloses an electric machine comprising a jacket coming to close notches regularly distributed in the stator. These notches receive conductive elements of the stator winding.

  The liner has a substantially cylindrical shape and is connected to a stator. For this, the liner comprises projecting zones separated by connecting zones.

  The projecting areas are vis-à-vis with the stator teeth. The connecting areas close the notches.

  This jacket allows to smooth the magnetic induction variation and therefore allows to reduce the variation of the magnetic interaction forces of the rotor with the stator and therefore the magnetic noise.

  The stator disclosed in the document of the prior art requires the production of a jacket to fit as closely as the shape of the stator teeth.

  In addition, the jacket must respect a strict coaxiality with the stator but also with the rotor to maintain a constant air gap.

  The production and assembly of such a shirt are thus long and expensive.

  DISCLOSURE OF THE INVENTION Also, a technical problem to be solved by the object of the present invention is to propose a stator which makes it possible: to limit the noise in the rotating electrical machine and in particular the noise resulting from the interactions between the rotor and the stator; to achieve this limitation simply and economically.

  A solution to the technical problem raised is according to a first object of the present invention a stator characterized in that it comprises a magnetically charged layer connecting at least two consecutive teeth of the stator.

  According to preferred non-limiting embodiments, the stator which is the subject of the invention has the additional characteristics, taken alone 2886481 or in combination, set out below.

  The layer connects the teeth over their entire axial length.

  The layer is a continuous layer connecting all the teeth of the stator.

  The layer has a determined thickness.

  The layer is a layer of paint with metal elements.

The layer is stainless.

  The depth of the depressions formed by the layer at the slot openings is reduced.

  According to a second object of the invention, a rotating electrical machine is characterized in that it comprises a stator according to the first object of the invention.

  According to additional features: The rotating electrical machine has a claw rotor.

  The rotating electrical machine has a claw rotor carrying permanent magnets.

Brief description of the figures

  Fig. 1 is an exploded view of a claw rotor of a rotating electric machine; Fig. 2 is a perspective view of a stator surrounding a rotor of a rotating electrical machine; Fig. 3 is a cross-sectional view of a portion of a stator according to the invention.

  DETAILED DESCRIPTION OF EMBODIMENTS OF THE INVENTION

  In the description which follows, a non-limiting example of a rotating electrical machine has been described. It is shown in FIG. 1, a rotor 10 of claw type. In a variant, the claw rotor may comprise permanent magnets at the poles.

  In another variant, the rotor may be of the type with salient poles with or without magnets.

  In the remainder of the description, use will be made of an X-X axial orientation from front to back which corresponds to a left-to-right orientation by considering FIG. 1. The X-X axis is also the axis of rotation of the rotor.

  The rotor 10 has a drive shaft 1 which allows the mounting of said rotor in rotation in a housing (not shown) of the machine. The shaft is rotated with the housing by means of bearings of which only one is shown.

  The drive shaft 1 comprises, on a first end, a threaded portion 19 for fixing a pulley (not shown) and at a second end a portion for fixing slip rings 6 providing the power supply to the coil 7 of the rotor.

  In addition, the drive shaft 1 supports at least a first front polar wheel 2, a magnetic core 3 receiving the coil 7, a second pole wheel 4, and the bearing 5.

  The magnetic core 3 is here a substantially cylindrical element independent of the two pole wheels.

  The rotor coil of the rotating electrical machine is, for its part, made in a coil holder 8, for example made of plastic material that can receive and guide at least one conductive element during its winding. The support is fixed, for example, by press fitting on the magnetic core. In addition, this coil support may have, in axial section, a U shape. Each of the pole wheels 2, 4 comprises an annular plate 11 carrying at its outer periphery claws each comprising a transverse portion 13 rooting extended flange by a tooth or pole 12, 14 of axial orientation. The poles 12, 14 are, here, 6 in each of the pole wheels 2, 4. We can also find wheels with 7 or 8 poles.

  In addition, the poles are regularly angularly distributed around the X-X axis common to the pole wheels 2, 4 and to the drive shaft 1.

  Each of the poles 12, 14 of a pole wheel extends axially towards the pole wheel in facing relation, so that they are nested within each other radially delimiting with the outer cylindrical surface of the core 3 , a space in which the coil 7 is arranged.

  In FIG. 2, there is shown a stator 20 surrounding a rotor 10. Alternatively, the rotor can surround the stator.

  The stator comprises a body in the form of a pack of sheets with notches 23 for receiving conductive elements 21. The stator also includes teeth 22 arranged between the notches 23 intended to cooperate with the poles 12, 14 of the rotor.

  In the case of a simple three-phase electric machine, a pole of the rotor faces three notches. In the case of a three-phase dual machine, a pole of the rotor faces 6 notches.

  The poles 12, 14 of the rotor are alternately magnetized. For example, the poles 12 belonging to the front polar wheel 2 are polarized north, and the poles 14 belonging to the rear polar wheel 4 are south polarized.

  During power supply of the coil 7 of the rotor, flux lines are created between the poles. A line moves from a north pole to a south pole.

  As the rotor 10 rotates inside the stator 20, the flow lines move from a north pole 12, to a south pole 14, through the stator body.

  With the rotation of the rotor, the magnetic induction at the leading edge of the stator teeth abruptly goes from 0 to its maximum value each time a pole 12, 14 of the rotor passes in front of this edge.

  But these brutal variations create a phenomenon of vibration of the teeth. A magnetic noise will then occur between the rotor and the stator. This noise plays an important role, in certain operating speed ranges of the machine, the general noise thereof.

  The invention seeks in particular to limit these magnetic noises.

  Fig. 3 shows a cross sectional view of a portion of the rotor and the stator according to the invention.

  The rotor poles 12, 14, the stator 20 and the gap 38 can be distinguished. The gap is, here, the radial space separating the external axial peripheral surface of the rotor from the inner axial peripheral surface of the stator.

  There is shown a tooth 22 of the stator. This comprises an upper portion 33 attached to the yoke 36, a lateral portion 34 and a lower portion or foot 35. The yoke 36 and the teeth define the notches 23, containing the conductive elements 21.

  In the case where the feet 35 of the teeth are straight, the notch is said to be open. Alternatively, in the case where the foot 35 of the teeth has a flared shape, as shown in FIG. 3, the notch is called semi-open.

  The foot 35 of the tooth 22 has a leading edge 40 where the induction variations at the time of the passage of the leading edges 41 of the poles of the rotor 15 are the strongest.

  Fig. 3 also has shims 37 used to close the notches 23 and thus maintain the conductive elements 21.

  Furthermore, the stator comprises a magnetically charged layer 39 conferring on it magnetic properties greater than those of air. This layer is then able to pass a magnetic flux. It is in particular deposited on the wedge 37, thus connecting two consecutive teeth of the stator.

  The layer may be a paint layer comprising metal particles guiding the flow.

  The layer may also be made stainless, for example by coming to cover it with a further stainless layer protecting the metal particles from any corrosion, for example an email layer. It is thus possible to use the rotating electrical machine in highly saline environments.

  During operation of the machine, the tooth 22 of the stator will receive the leakage flux 32 from a pole 12 of the rotor in the vicinity of the latter well before this pole reaches the right of this tooth. The magnetic portion of the layer will then guide and initiate the passage of the leakage flux 32 of the pole 12 in the tooth.

  Thus, when the pole of the rotor reaches the right of the tooth of the stator considered, the latter is not subject to a sudden change in the magnetic flux from the pole 12 of the rotor.

  Consequently, the tooth of the stator, and in particular its foot 35, will not be caused to vibrate because the slope of the variation of the magnetic flux has been softened, thus limiting the magnetic noise produced between the rotor and the stator.

  It will be noted that the leakage flux 32, produced by the pole 12, vanishes at the level of the tooth 22 once this pole is at the right of this tooth.

  In a preferred embodiment, the layer connects at least two consecutive teeth of the stator over their entire axial length. This allows a flow passage 32 to a larger surface between the teeth.

  The leakage flux 32 is to be distinguished from the useful flux 31. Indeed the useful flux 31, coming from a pole 12, surrounds the notches by creating in the conductive elements 21 an induced voltage which is found at the output of the winding of the stator. The leakage flux 32, on the other hand is path in the stator, does not contribute to the creation of this induced voltage in the conductive elements.

  The presence of a leakage flow 32 is advantageous in the case where the machine operates in motor mode. Indeed, in this particular mode, the idle speed of the machine is inversely proportional to the useful flow 31. By creating a leakage flow 32, the useful flow 31 is reduced and the empty speed of the machine is increased.

  In most cases, however, it is desired to limit the leakage flux 32 in order to attenuate the voltage losses induced in the conductive elements 21 of the stator.

  It will be noted that the intensity of the leakage flux 32 depends on the thickness of the layer. At a determined thickness of the layer then corresponds a value of the intensity of leakage flux 32.

  Thus, when the layer is in a state of magnetic saturation, the intensity of the leakage flux 32 that can pass through the layer is maximum.

  The thickness of the layer can be controlled by a simple and economical method, such as, for example, a method using a paint spray gun or a nozzle whose paint delivery rate is controlled.

  Thus, with this method the entire inner surface of the stator is covered by the layer.

  The layer is therefore continuous and rests on the radial end of the feet of the teeth and on the wedges 37 between two adjacent teeth.

  The width of the air gap is thus reduced by the thickness of the layer and therefore the useful flux is increased. The efficiency (ratio of the useful flux 31 to the leakage flux 32) of the rotating electrical machine is improved.

  In addition, the continuous layer also gives a smoother appearance to the inner surface of the stator. The airflow noise between the rotor and the stator is thus substantially improved. Indeed, the rotation of the rotor creates air vortices in the air gap that will amplify in contact with the notch openings. Now here, the openings are partially filled by the layer 39. The air vortices are thus attenuated.

  The Applicant has thus estimated by experience that the gain of the invention on the magnetic noise is of the order of 3 to 6 dB and of the order of 2 dB on the aeraulic noise of the rotating electrical machine.

  It will be noted that the share of the magnetic noise in the overall noise of the machine is preponderant when the speed of the machine is reduced (less than about 6000 revolutions / minute) and that beyond that it is the part of the aeraulic noise that becomes major.

  Advantageously, it is possible to reduce the magnetic and aeraulic noise by limiting the depth of the recesses 30. It is thus possible to act on the thickness of the flared portions of the feet of the teeth, on which the shims 37 rest, by decreasing it. It is also possible, during the formation of the layer 38, to further fill the recesses 30 with an addition of material at the level of the notch openings greater than the quantity of material deposited on the rest of the stator. This can be done by providing a process that dumps more material at each slot opening. The depth of the depressions 30 formed by the layer at the slot openings is thus reduced.

  In another embodiment where there is no shim 37, there can be provided a layer, such as a resin having magnetic elements, which in hardening will come, in addition to guiding the leakage flow 32, close the notch for holding conductive elements therein 21.

  Thus, by a simple and economical process, the magnetic and aeraulic noise created between the rotor and the stator of a rotating electrical machine are reduced.

  The present description is not limited to the embodiments described above.

  The invention applies to any type of rotating electrical machine such as an alternator, an electromagnetic retarder or an electromagnetic coupler with eddy currents and also to any type of reversible rotating electrical machine such as an alternator-starter.

2886481 10

Claims (10)

  1. Stator (20) of a rotating electrical machine having a body having: - a yoke (36), - notches (23) for receiving conductive elements (21); teeth (22), attached to the yoke and arranged between the notches, intended to cooperate with the poles (12, 14) of a rotor; characterized in that it comprises a magnetically charged layer (39) connecting at least two consecutive teeth of the stator.   2. Stator according to claim 1 characterized in that the layer (39) connects the teeth (22) over their entire axial length.   3. Stator according to any preceding claim characterized in that the layer (39) is a continuous layer connecting all the teeth of the stator.   4. Stator according to any one of the preceding claims characterized in that the layer (39) has a determined thickness.   5. Stator according to any one of the preceding claims characterized in that the layer (39) is a paint layer comprising 25 metal elements.   6. Stator according to any one of the preceding claims characterized in that the layer (39) is stainless.   7. Stator according to any one of the preceding claims characterized in that the depth of the recesses (30) formed by the layer at the slot openings is reduced.   8. Rotating electrical machine characterized in that it comprises a stator (20) according to any one of the preceding claims.   9. Rotating electrical machine according to claim 8 characterized in that the rotor is a claw rotor.   10. Rotating electrical machine according to claim 8, characterized in that the rotor is a claw rotor carrying permanent magnets.