FR2859325A1 - Water cooled electromagnetic brake for heavy road vehicle such as lorry or bus, includes fluid filled coolant chambers both inside and outside stator assembly - Google Patents

Abstract

The electromagnetic brake (1) comprises an armature stator (6) and an inductor rotor (5). The stator has at least one external cooling chamber (64) which surrounds at least a part of the coil (7) on the rotor (5), and at least one internal cooling chamber (65). Coolant fluid passes through these chambers. The electromagnetic brake (1) comprises an armature stator (6) and an inductor rotor (5) mounted coaxially with the stator. The rotor (5) has at least one coil (7) mounted on a core (67), and preferably has a number of such coils. The core forms a section of the rotor is inserted within the stator (6). The stator is configured to provide at least one external cooling chamber (64) which surrounds at least a part of the coil (7) on the rotor (5). The stator is also configured to provide at least one internal cooling chamber (65) which itself is surrounded in part by the coil of the rotor (5). A distribution valve determines the percentage of coolant which flows into the external and internal cooling chambers.

Description

Electromagnetic retarder of a motor vehicle

the invention

  The invention relates to an electromagnetic retarder of a motor vehicle with water cooling. The invention aims to increase the performance of such a retarder. The invention also aims to reduce the weight and bulk of this retarder. The invention is more particularly intended for the field of the truck, bus and bus, that is to say motor vehicles of the heavy truck type but can also be applied in other fields.

  An electromagnetic retarder makes it possible to assist a braking device of a vehicle, in particular for vehicles of the "heavy goods vehicle" type. A braking device may comprise brake pads intended to come closer against at least one disk of a hub of a wheel of a vehicle to brake the vehicle. There are several types of electromagnetic retarders. In particular, there exist axial-type electromagnetic retarders, "Focal" type electromagnetic retarders and "Hydral" (trademark) type electromagnetic retarders. An axial-type electromagnetic retarder is intended to be placed on the motion transmission line between a bridge and a vehicle gearbox; the transmission shaft then being in two parts for mounting between them of the retarder. An electromagnetic retarder type "Focal" is intended to be placed directly on a transmission shaft at the output of the gearbox or directly on the vehicle deck. The bridge of a vehicle drives at least one wheel shaft, which wheel shaft drives at least one wheel of the same vehicle. An electromagnetic retarder type "Hydral" is also provided to be directly placed on a transmission shaft at the output of the gearbox. This electromagnetic retarder type "Hydral" adapts particularly well to short-shaft vehicles.

  Such an electromagnetic retarder of the "Hydral" type, described for example in document FR A 2 627 913, comprises at least one induced stator and at least one inductor rotor mounted coaxially. The induced stator may comprise a hollow circular cylindrical shape allowing the inductor rotor, also having a smaller hollow circular cylindrical shape, to be inserted inside the stator with the presence of an air gap. The rotor is intended to rotate about an axis of the stator due to the transmission of a rotational movement to the rotor by the transmission shaft of the vehicle. The rotor, in one embodiment, carries at least one magnetic coil. Thus, the induced stator is provided to ensure the passage of a magnetic field produced by the coils. In the axial type of retarders or "Focal" it is the opposite, the stator then being an inductor stator carrying the coils, while the rotor is an induced rotor.

  STATE OF THE ART Generally, electromagnetic retarders comprise an even number of coils of alternating polarity. A coil has a hollow circular cylindrical shape. The shape can, of course, be different from a circular shape and be, for example, square, elliptical or other. A coil is formed by winding an electrical wire into a circular cylindrical shape. The coil is carried by a core, which core is fixed to the stator along an axis of the core perpendicular to the plane of the stator and coaxial with an axis of the retarder. In one example, the coils are formed by a copper wire. The winding of the copper wire makes it possible to define an axis of the coil perpendicular to the winding direction of the electric wire, which axis of the coil coincides with the axis of the core. In the case of the "Hydral" type electromagnetic retarder, the coils can be distributed uniformly and radially with respect to an axis of the rotor, with their coil axis perpendicular to the plane of the inductor rotor and to the plane of the induced stator.

  Preferably, the coils operate in pairs. Each of the pairs of coils is intended to form a magnetic field which closes from one to the other passing through the rotor and into the stator. This magnetic field is created when you want to slow down the rotor which rotates around a stator axis.

  In the case of a retarder of the "Hydral" type mentioned above, this magnetic field is formed by traversing the first coil carried by the inductor rotor in a core of the first coil and then enters the stator, perpendicular to a plane of the stator. The plane of the stator may be formed by the wall of the stator for example of ferromagnetic material. Then the magnetic field propagates in the stator parallel to the plane of the stator and parallel to a direction of rotation of the rotor. Then the magnetic field joins the core of the second coil exiting perpendicularly from the plane of the stator and along an axis of this second coil. Finally, the magnetic field forms a loop by rejoining the first coil passing from the second coil by the rotor. When the electromagnetic field crosses perpendicularly the plane of the stator, an electric current or eddy current is created in the stator because of the displacement of the rotor.

  Indeed, in application of the law of Faraday, an electrical conductor that moves in a field produces at its terminals a voltage which is the vector product of this field by the speed of displacement. This vector product is maximal when the field is perpendicular to the speed. Everything happens as if an electric voltage was produced in places of the rotor where each axis of the coils intersects the plane of the stator, while between these two places no voltage is produced. Between these locations the magnetic field, tangential to the plane of the rotor, is parallel to the direction of movement of the rotor. The eddy currents that are born are located in the locations of the stator where the magnetic field passes through the stator.

  More particularly, the eddy currents are born in the stator only where there is a perpendicular component of the magnetic field with respect to the direction of rotation of the rotor. Such an electric current or eddy current is intended to oppose the speed of rotation of the rotor. It is this eddy current which is used to slow down the rotational speed of the vehicle shaft, the rotor being connected to the transmission shaft, the transmission shaft being itself linked to at least one wheel of the vehicle. vehicle. It thus appears in the current system that the electromagnetic retarders cause the braking of the vehicle following an opposition to the rotational movement of the rotor through the perpendicular crossing of the stator plane of at least one magnetic field between two coils.

  To cool the electromagnetic retarder following a heating of the stator wall by the eddy currents, the stator wall is hollowed out of a cavity or cooling surface inside which a fluid is intended to infiltrate to cool the stator.

  This type of retarder is satisfactory, however it is desirable to further increase the cooling capabilities of the electromagnetic retarder to increase its performance.

  OBJECT OF THE INVENTION The object of the present invention is to respond to this desire simply and economically.

  According to the invention a retarder of the above-mentioned type comprising an annular-shaped stator and an annular-shaped inductor rotor coaxially mounted with respect to the stator and provided with at least one coil mounted on a core, in which the rotor is inserted in the stator and in which the stator is configured to have at least one outer cooling chamber, which at least partially surrounds the rotor coil is characterized in that the stator is configured to also have at least one inner cooling chamber which is surrounded at least in part by the rotor coil.

  Thanks to the invention the stator is multi-chamber and increases the cooling capacity and therefore the performance of the retarder More precisely the retarder can release more thermal energy following the presence of eddy currents so that its power is increased .

  The rooms are carried by the stator.

  In one embodiment the chambers are carried by inner and outer walls of the stator, the outer wall surrounding at least the major part of the inner wall.

  The invention uses the inner and outer walls to increase the induced area of the stator, which allows more heat to be generated in combination with the presence of the chambers.

  In one embodiment the rotor has a plurality of separate cores carrying the excitation coils for reducing the radial bulk and weight of the rotor. Voids exist between two consecutive nuclei.

  These cores are fixed on a generally transversely oriented carrier element, such as a flange or a web, and extend axially cantilever with respect to this carrier element.

  At least one ring with a high elastic limit is mounted for example at the free end of the cores to hold them well and obtain a gap as constant as possible between the rotor and the stator.

  The ring and the flange or the veil are non-magnetic material to channel the magnetic flux to the stator when the coil or coils are activated.

  Alternatively the cores are interconnected by an inner sleeve.

  In one embodiment, the inner and outer walls are connected transversely by a bottom for forming a space, such as a blind annular cavity, and the cores equipped with their coils penetrate into said space.

  Adjusting means, such as a distribution valve or distribution circuits, are advantageously provided for regulating the flow rates in the internal and external chambers in order to standardize the temperatures in the stator.

  The invention makes it possible to reduce the size of the retarder.

  Thus, to reduce the weight and bulk of these electromagnetic retarders, the electromagnetic retarder is positioned at an offset from the vehicle's motion transmission.

  This is made possible by the presence of the multi-chamber stator according to the invention for increasing the cooling surface in the armature and the heat-generating capabilities.

  To position the electromagnetic retarder offset relative to this transmission, a speed multiplication device can be interposed between the transmission and the electromagnetic retarder. This speed multiplication device integrated in the electromagnetic retarder makes it possible to increase the performance of the electromagnetic retarders. This speed multiplication device may be a gear speed multiplication device. This gear speed multiplication device is constructed in such a way that the transmission cooperates with the retarder via a first disk and a second disk respectively. The first disc and the second disc each have at their periphery teeth made in such a way that the teeth of the first disc fit between the teeth of the second disc by complementarity and vice versa. For the rotational speed of the rotor to increase, the first disk has a larger size than the second disk.

  By positioning the electromagnetic retarder offset relative to the transmission, it is possible to reduce the size of this retarder by decreasing its size. The reduction of the size of the electromagnetic retarder is possible because it is no longer necessary to pass the transmission directly into the electromagnetic retarder.

  The reduction in the size of the electromagnetic retarder does not lead to a reduction in the thermal capacity of the electromagnetic retarder thanks to the multi-chamber stator.

  The invention makes it possible to keep the same cooling surface in the armature of the machine.

  The invention also provides for extending at least one of the cooling chambers of the stator. The cooling chamber of the stator is then extended by extending this chamber in the bottom of the stator.

  Alternatively a single chamber is provided, the latter being in an embodiment dug in the walls and the bottom of the stator or made by an added wall, which surrounds the walls and the bottom.

Brief description of the drawings

  The invention will be better understood on reading the description which follows and on examining the drawings which accompany it. These are only indicative and in no way limitative of the invention.

  The drawings show: FIG. 1: a schematic representation of a speed multiplier device intervening between the electromagnetic retarder shaft according to the invention and the motion transmission shaft of a vehicle, according to the invention; - Figure 2: a schematic half-view in axial section of an electromagnetic retarder of a vehicle according to the invention; - Figure 3: a partial sectional view along the line 3-3 of Figure 2 with modification of the retaining ring of the coils; - Figure 4: a view similar to Figure 2 for a second embodiment of the invention; - Figure 5: a perspective view of the implantation of the electromagnetic retarder for a third embodiment of the invention; - Figures 6 and 7 are views similar to Figure 1 for other embodiments of the speed multiplier device.

  DESCRIPTION OF PREFERRED EMBODIMENTS OF THE INVENTION In these figures, the common elements will be assigned the same reference signs.

  In order to increase the heat-generating capacity and thus to increase the power and the performances of an electromagnetic retarder with an induced stator and an inductor rotor, mounted coaxially and referenced respectively to 1, 6 and 5 in Figure 2, it is proposed in the embodiments of the invention to provide the stator 6 with several cooling chambers.

  This retarder is in an embodiment traversed by a motion transmission of the heat engine to at least one wheel of the motor vehicle, which as we know comprises a transmission shaft, such as the aforementioned shaft intervening between the box of speed and the bridge of the motor vehicle driving at least one wheel shaft of the vehicle, for the purpose of reducing the weight, bulk, cost of manufacture, through the increase of the heat release capacity of the electromagnetic retarder 1 , it is proposed that the retarder, on the one hand, is positioned offset from said transmission of motion and, on the other hand, to provide the stator 6 with several cooling chamber. advantageously to keep at least the same cooling surface in the induced stator 6 compared to a conventional retarder.

  As is known, the rotor 5 is integral in rotation with a shaft, said retarder shaft.

  In this case the transmission shaft is separate from the retarder shaft and as a result the retarder is not traversed by the motion transmission.

  The retarder shaft is in an embodiment integral with a secondary transmission shaft that has the gearbox for example intervention of a hydrodynamic retarder comprising a movable turbine wheel coupler and fixed impeller wheel.

  In one embodiment (FIG. 1) this offset is achieved by means of a speed multiplier device 16, the retarder shaft 19 being parallel to the motion transmission shaft 4 or alternatively parallel to said secondary shaft. transmission which further reduces the size and weight of the retarder while having the ability to release heat required.

  The retarder shaft is thus positioned offset from the transmission shaft, which is not cut. Axes of axial symmetry of these trees are thus offset and therefore distinct.

  The speed multiplier device of FIG. 1 may be a gear device comprising, for example, two gears described hereinafter. However, this speed multiplier device could be a belt speed multiplier or a chain speed multiplier. Thanks to these provisions by multiplying the speed, the weight and the size of the retarder are reduced; the heat being released by circulation of the cooling fluid inside the stator chambers described below.

  As is known and as visible in FIG. 2, the retarder shaft 19 has an axis of axial symmetry, which corresponds to the axial axis of symmetry 9 of the rotor 5, itself corresponding to an axis of symmetry. axial 15 of the stator 6, knowing that the rotor 5 and the stator 6 are ring-shaped and coaxial.

  The gear speed multiplier device 16 of FIG. 1 includes a first disk 17 and a second disk 18 each belonging to a gear wheel. The first disc 17 is interposed in the motion transmission being secured to the shaft 4 thereof so that a plane of the first disc is perpendicular to the axis of axial symmetry 14 of the transmission. The second disk 18 is carried by the rotor 5 by means of the retarder shaft 19.

  More precisely, the disc 18 is fixed to one end of the shaft 19 having an axial axis of symmetry coinciding with the axes 9,15. At its other end, as shown in dashed lines in FIG. 2, the shaft is provided with an annular plate 119 of transverse orientation with respect to the axes 9, 15 for its attachment to a generally transverse orientation bearing element, here in the form of a flange 21 transverse, that presents the rotor.

  Alternatively the flange is shorter and the carrier element consists of a web as described below.

  The second disk 18 is thus placed in such a way that a plane of this second disk is perpendicular to the axis 9 of the rotor. Thus, the first disk and the second disk both have a plane parallel to each other. The first disk and the second disk are arranged in such a way that they are placed one below the other in a plane perpendicular to the axis 14 of the transmission 4 and to the axis 9, 15 of the electromagnetic retarder .

  The first disk and the second disk each have at their outer periphery a series of teeth so that two toothed wheels are formed. The transmission 4 and the electromagnetic retarder 1 cooperate by inserting each of the teeth of the first disk 17 between each of the teeth of the second disk 18 by complementarity and vice versa.

  The shape of the teeth is made in such a way that the teeth can be inserted by complementarity. Thus, the teeth may be triangular in shape such that tips extend radially from a center of the first disc and a center of the second disc. The center of the first disk may correspond to a location on the first disk where the axis of the transmission is likely to pass through the first disk. The center of the second disk may correspond to a location on the second disk where the retarder axis is likely to pass through the second disk. Or the teeth may have a rectangular shape, trapezoidal or advantageously an involute profile arcuate like conventional gears.

  Thus, the transmission imparts rotational movement to the first disc, which first disc also imparts rotational movement to the second disc through the teeth. The second rotating disc thus causes rotation of the inductor rotor via the shaft 19 and the plate 119.

  To increase the rotational speed of the rotor, the first disc 17 has an outer diameter greater than the outer diameter of the second disc 18. The increase in the speed of rotation of the rotor is performed in such a way that the second disc can thus rotate on itself several times to completely traverse the outer periphery of the first disk 17. The increase in the rotational speed of the rotor is proportional to the decrease in the diameter of the second disk relative to the diameter of the first disk. The second disc, smaller than the first disc, is a pinion.

  FIG. 2 shows an electromagnetic retarder 1, in particular for a motor vehicle, disposed here between the gearbox and between at least one wheel of the vehicle. This retarder 1 is intended to assist the braking of the vehicle via the aforesaid drive shaft transmission 4.

  The electromagnetic retarder 1 comprises at least one inductor rotor 5, at least one induced stator 6 and at least one coil 7 mounted on a core 67. Preferably at least two coils 7 and two cores are provided. 67.

  In the example of this FIG. 2, this electromagnetic retarder is an electromagnetic retarder of the "Hydral" type, described for example in the document FR A 2 627 913 corresponding to the document EP 0 331 559 to which reference may be made for more details. In this same example of Figure 2, the rotor 5 is inserted inside the stator 6 to be mounted on a fixed part of the vehicle, here on the housing of the gearbox.

  A small clearance, called gap, is present between the rotor 5 and the stator 6 coaxial to achieve an electromagnetic connection described below.

  The inductive rotor, as in the aforementioned documents, comprises a plurality of coils or winding of electrically wire 7 distributed circumferentially in a regular manner, which conduct the electric current of excitation of the retarder and which, with radial cores 67 of magnetic material, they surround, define a ring of inductive poles with alternating polarities step by step.

  The axes of the coils 7 and cores 67, of oblong shape, extend radially around the axis 9,15 of the retarder.

  The coils 7 are electrically powered by a current generator in the form of an alternator of the polyphase type, comprising a stator 31 inductor, integral with the stator 6, surrounding a rotor 32 induced integral rotor 5. An air gap exists between the stator 31 exciter and the generator rotor 32, which each comprise a plurality of electric wire coils, respectively 33 and 35, wound around radial cores with end retaining openings, respectively 34 and 36, of magnetic material. The inductor stator 31 is multi-pole, its coils 34 being connected to a direct current source, here the battery of the vehicle, via a manually controlled adjustment circuit, the alternating current collected at the terminals of the rotor 32 induced by being rectified by a suitable DC rectifier rectifying device before being sent to the coils 7. For more details we refer to the aforementioned documents.

  In a variant, the current generator comprises brushes mounted in cages carried by the stator 6 in order to rub against rings electrically insulated by the rotor under the action of springs mounted in the cages. The rings are electrically insulated by the flange 22.

  In this case we do not have to rectify the current to feed the coils 7.

  Here the stator 6, and the cores 67, 34, 36 are advantageously made of ferromagnetic material and the coils 7, 33, 34 are here wound copper wire and coated with an insulator.

  In this FIG. 2, the annular stator 6 is, according to the invention, configured to have at least one external cooling chamber 64, which at least partly surrounds the coil 7 of the annular rotor 5, and at least one chamber internal cooling device 65, which is surrounded at least in part by the coil 7 of the rotor 5.

  The retarder also comprises parts made of non-magnetic material, namely the flange 21 of transverse orientation relative to the axis 9, 15, a retaining ring 37 of orientation transverse to the axis 9, 15 and a flange annular 22 axially oriented relative to the axis 9,15. These parts are for example stainless steel or titanium.

  The rim 22 is secured, for example by screw-welding and / or bonding, of the flange 21 in the form of a disk connected centrally to the shaft 19. In a variant, the rim 22 is integral with the flange 21 while being integral with it. this. The flange 22 carries at its outer periphery the rotor 32 of the alternator. This rotor 32 is surrounded by the stator 31 of the alternator carried by the inner periphery of an annular rim of axial orientation 66 integral with the stator 6.

  The flange 66 axially extends a cylindrical wall of axial orientation 61 that the stator 6 has at its outer periphery. Its thickness is less than this outer wall 61.

  The wall 61 is connected at its other axial end to a bottom 62 of transverse orientation with respect to the axis 9, 15. The bottom 62 is open centrally in Figure 2 and is therefore in the form of a washer.

  According to one characteristic, an internal annular wall 63 of axial orientation with respect to the axis 9, 15 is connected to the bottom 62. This internal wall 63 is surrounded by the outer wall 61 by being in FIG. for passing the flange 21 adjacent the edge of the wall 63 and the inner periphery of the wall 61.

  The bottom 62 delimits with the walls 61, 63, here of tubular form, a space in the form of a blind annular cavity 60 inside which penetrates, according to a characteristic, the inductor portion of the rotor 5 comprising the coils 7 and the nuclei 67.

  A gap, here constant, exists between the cores 67 and the wall 61 and between the cores 67 and the wall 63.

  The stator 6 thus has an annular U-shaped section and is open centrally.

  The walls 61, 62 and 63 can be in one piece.

  Alternatively the bottom 62 is attached to the walls 61, 63 tubular by

example by welding.

  One of the walls is alternately secured to the bottom and the other attached to the bottom for example by welding.

  All combinations are possible so that the bottom 62 can completely close the stator and be disk-shaped as can be seen in FIG. 5, the bottom bearing the reference 162. This closed bottom 162 therefore centrally comprises an extension of the bottom 62 on which can be fixed, as described below, a claw inductor stator.

  The inductor portion 67, 7 of the rotor 5 is fixed via its cores 67 to the flange 21 for example by welding or screwing the cores 67 on the flange 21. The flange 22 extends axially projecting from the other side of the flange 21 so that the inductor portion and the alternator extend on either side of the flange 21.

  This flange serves to channel the magnetic flux towards the stator 6 when the coils 7 are activated.

  The flange 22 is implanted globally on the same diameter as the inner periphery its cores 67.

  Advantageously, the cores 67 each have a groove 68 (FIG. 3) for retaining their associated coil 7. The flange 21 is in a feature partially dug to create a reception clearance of the coil heads 7 and maintain them.

  The cores 67, of oblong shape, extend in axial projection relative to the flange 21 so that it is desirable to ensure good radial strength of the cores mounted at the outer periphery of the flange 21 on the face thereof. This is achieved by means of the retaining ring, which also makes it possible to guarantee the gap between the stator 6 and the rotor 5.

  To do this, the aforesaid retaining ring 37 is engaged within deep grooves 168 of the grooves 68, said enlargements 168 being made locally each at the free axial end of a groove 68 facing the bottom 62. These local enlargements are obtained by extending the edges of the grooves 68 towards the bottom 62. Of course some cores 67 may be devoid of such enlargements 168. For better mechanical strength and better balance all the cores have at their free end an enlargement 168, whose depth depends on the thickness of the ring 37 and the coils 7.

  The enlargements 168 are obtained by means of local axial extensions in the form of the respective external and internal openings 51, 52, of each respective core 67, and this axially in the direction of the bottom 62 for the formation of extensions extending the axial edges. grooves 168. The openings 51, 52 are therefore made at the free axial end of the cores; other blooms, not referenced, being made at the other axial ends of the cores for maintaining coils in cooperation with the recesses of the flange 21.

  The heads of the coils 7 are interposed between the bottom of the enlargements 168 and the ring 37 advantageously fixed by any means - such as by screwing, engagement by force, embedding, bonding or welding - on the cores 67. The ring 37 closes the opening enlargements 168 and interconnects the cores 67 which are well maintained mechanically. The inductor rotor thus has a good resistance to centrifugal force thanks to the ring 37, which also ensures the balance in the axial direction relative to the flange 21. The ring 37 ensures radial rigidity and balance axial rotor in combination with the flange 21.

  Advantageously, the ring 37 has a high elastic limit, which makes it possible to ensure even better radial rigidity and better axial equilibrium of the rotor 5.

  The ring 37 is of rectangular section in FIG. 2. As a variant it is of round, square section ...

  Thanks to the invention the rotor is radially compact and lightweight Alternatively (Figure 3) there are two rings with high elastic limit closing the outer and inner periphery of the opening of the grooves 168. The rings 137, 237 partially cover the heads coils and are fixed directly, for example by gluing or welding on the edge of the axial free end of the shoes 51, 52 cores 67, 68 as visible in FIG.

  Alternatively the ring 37, 137, 237, of rectangular shape is in contact by its smallest side with the cores. It extends in contact with the edge of the openings 51, 52 of the cores 67 without interfering with the coils 7 and is then of axial orientation.

  Alternatively the shoes 51, 52 are shorter and the ring 37 extends in contact with the edge of the free axial end of the openings 51, 52 of the cores to close the openings of extensions 168 then shortened.

  Fixing the ring is simple and is performed for example by screwing or welding.

  In all cases the weight and bulk of the inductor rotor 5 are reduced since the cores 67 are distinct from each other without being interconnected by an inner sleeve.

  Of course, in a variant, such a sleeve is provided.

  The chambers 64, 65 above are intended to be traversed by a cooling liquid advantageously consisting of water containing antifreeze. Of course, other coolants can be used.

  In this Figure 2 is schematized by arrows the inlet and outlet pipes.

  The cooling circuit further comprises a drive pump and advantageously a finned radiator for dissipating outwardly the calories carried by the cooling fluid in circulation.

  As described in document FR A 2 627 913 or its corresponding EP 0 331 559, the pump and the heat exchanger are advantageously the water pump and the radiator, which form part of the cooling circuit of the engine of the motor vehicle, the retarder being advantageously implanted in the aforementioned manner in the vicinity of the gearbox near the circuit.

  As can be seen in FIG. 2, the chambers 64, 65 are made in the respectively outer 61 and inner 63 walls and are therefore annular with axial orientation. To do this the walls 61 and 63 are dug.

  In a variant, at least one of the chambers 64, 65 is obtained obtained by means of an additional hollow wall attached to the wall 61, 63, which is not hollowed out.

  In a variant, the chambers 64 and 65 are extended in the bottom 62 as shown in dashed lines in FIG. 2 (references 167 and 166).

  Of course, at least one of the chambers 64, 65 can be replaced by two or more chambers one after the other.

  In a variant, as described in document EP A 0 331 559, one of the chambers may be replaced by a pipe wound in a helix on the outer periphery of the wall 61 or on the inner periphery of the wall 63, which are then not dug.

  In all cases the chambers 64, 65 are carried by their associated wall 16.

  The wall 63 and the chamber 65 may be axially shorter. The chamber 64 extends over the entire length of the inductor portion 67,7 of the rotor.

  In a variant, it is shorter as is the chamber 65.

  Advantageously, the chambers 64 and 65 extend over at least 50% of the length of the inductor portion 67, 7 of the rotor.

  In Figure 2 the upper chamber 64 extends over the entire length of the cores 67 and coils 7 and surrounds them. The chamber 64 partially affects the bottom 62 and is longer than the inductive portion 7, 67.

  The chamber 65 also affects the bottom 62 and is axially offset relative to the inductor portion 7, 67 of the rotor 5 because of the presence of the flange 21. The chamber 65 is surrounded for the most part by the cores 67 and the coils 7.

  Each wall may be in two parts as shown in Figure 3 of EP A 0331 559, a cover, or generally an additional wall added, being attached to the wall to form the chamber. To improve exchanges can be provided hollows or reliefs in the walls as shown in Figure 2 of this document EP A 0331 559.

  It can be seen in the light of FIG. 3 of this document that the flange 21 can be replaced by a sail attached to a plate integral with the output shaft of the gearbox, belonging to the aforementioned transmission of movement, and that the lower chamber 65 and the inner wall 63 may be shortened to come closer to the sail so that the retarder is traversed by said transmission. In this case the cores 67 are interconnected by an inner sleeve. Alternatively the cores are distinct and maintained by the retaining ring and the veil as in Figure 2.

  Fixing the retarder 1 according to the invention can be achieved using tabs from the rim 62 and fixed on a bell itself attached to the gearbox.

  Such a fixed plate of the gearbox is visible at 40 in FIG. 5 showing at 14 'the axis of a secondary output shaft or secondary transmission shaft of the gearbox intended for the intervention of a hydrodynamic retarder supra, bearing the reference 200 in Figure 5. This retarder is more bulky than the retarder according to the invention 1 which is seen at 9, 15 axis. In this case a speed multiplier device of the type of FIG. 1 occurs between the parallel axes 14'-9.15, more precisely between the retarder shaft and the secondary transmission element constituted by the secondary output shaft.

  This device 16 is alternatively angular gear as shown in Figures 6 and 7 so that the retarder 1 according to the invention is implanted horizontally (Figure 6) or vertically (Figure 7) relative to the gearbox 100 with output shaft or secondary transmission element 4 'of axis 14' perpendicular to the axis 9.15 of the retarder 1 according to the invention.

  The toothed discs 17, 18 of FIG. 1 are then replaced by bevel gears 17 ', 18', the external diameter of the pinion 18 'associated with the retarder being less than the pinion 17' associated with the shaft 4 '. Of course this also applies to the embodiment of Figure 1, the shaft 4 'being then replaced by the shaft 1.

  Of course, as an alternative, the extensions 166, 167 of the chambers 64, 65 meet as shown in FIG. 4 to form a single chamber 268 with a U-shaped half section. The chamber 268 therefore extends into the walls 61, 63 and the bottom 62. In this case there are two inlet and outlet pipes represented by arrows in FIG. 4 and in 170 and 171 in FIG.

  The magnetic field generated by the coils 7 is here radial. The circuit for adjusting the excitation of the coils 7 comprises in the aforementioned manner a manual adjustment member, such as a joystick. The adjustment member is alternatively associated with the brake pedal.

  When at least two of the coils are energized during a braking of the vehicle, as represented by the arrows of FIG. 3, a magnetic field can be formed from one coil 7 to another coil 7 while passing through the core 67 of each of these coils. The magnetic field is intended to pass through the plane of the walls 61, 63 of the stator and the plane of the rotor. Crossing the plane of the stator, the magnetic field first crosses perpendicularly first the plane of the wall 61 of the stator and then parallel to the plane of the stator, then a second time perpendicularly to the plane of the wall 61 to join the core. the second coil 67 and the rotor and cross a first time perpendicular to the plane of the inner wall 63, then parallel to the plane of the wall 63 and then a second time perpendicularly to the plane of the wall 63 to join the core 67 of the first coil 7 and the rotor. Foucault current zones are only formed in places where the magnetic field crosses the plane of the stator perpendicularly.

  These eddy currents oppose the rotational movement of the rotor. By opposing the direction of rotation of the rotor, the eddy currents cause braking or slowing of the rotational movement of the rotor transmitted indirectly by the device 16 or directly to the transmission. The braking commanded by the support of a foot of a driver on the brake pedal is then assisted by such an electromagnetic retarder following the slowing down or stopping of the rotational movement of the transmission towards at least one vehicle wheel.

  It will be appreciated that the decrease in the size of the electromagnetic retarder via the device 16 does not result in a decrease in the thermal capacity of the electromagnetic retarder. Heat capacity means the amount of stator material that can be heated, in particular by eddy currents. During the operation of the electromagnetic retarder, the stator is rapidly heated following the circulation of the eddy currents in the walls 61, 63 of the stator while being well cooled by the multiplication of the chambers 64, 65 making it possible to increase the cooling surface of the stator. stator without a decrease in performance.

  It will be appreciated that the embodiment of FIG. 2 is advantageous since it makes it possible to regulate the flow rates in the chambers 64, 65 differently by means of adjustment means, such as a distribution valve or distribution circuits. . Indeed it is found that the outer wall 61 is more stressed during operation of the retarder. Having more flow in the upper chamber 64 balances the temperatures in the walls which reduces the mechanical tension. Good results were obtained by having 85% of the flow rate in the upper chamber 64 and 15% of the flow rate in the lower chamber 65. for a power distribution of 70% (at the outer wall) and 30% (at the of the inner wall).

  The invention is not limited to the described embodiments.

  Thus, in a variant, the flange 62 connecting the walls 61 and 63 transversely is alternatively frustoconical in shape.

  In all cases the inner wall is surrounded at least in part by the coils 7.

  The thickness of the walls 61, 63 and the bottom 62 is alternatively non-constant.

  Alternatively, the excitation alternator can be mounted inside the inner wall 63 and use the bottom 162 of FIG. 5, more precisely the central extension of the edge 62, and the carrier element, such as the flange 21. to fix the stator and rotor of the alternator.

  This excitation alternator advantageously has the constitution of a motor vehicle alternator of large series, such as the one with internal ventilation described in document FR A 2 676 873 to which reference will be made for more details. More precisely, it is enough to reverse the structures. In other words, the rotor with claws and excitation coil of the document FR A 2 676 873 becomes, via its shaft, secured to the central extension of the edge 62 of the stator 6 of the retarder of the invention, while the two hollow form flanges of this document FR A 2 676 873, assembled together by means of screws or any other means to form a housing bearing the polyphase stator and the rectifier bridge, become integral with the carrier element 21. This is made possible because each of the flanges centrally carries a ball bearing intervening between the flange and the axial end concerned the rotor shaft. The rotor of this document FR A 2 676 873 becomes a claw excitation stator while the polyphase stator of this document FR A 2 676 873 becomes an induced rotor surrounding the driving stator or inducing stator. This induced rotor comprises a body in the form of a bundle of grooved plates for mounting a winding having a plurality of windings connected to the electric supply rectifier bridge of the coils 7. The inductor stator comprises two pole wheels with claws with presence between these of a core carrying an inductor winding. In this case we remove the regulator mounted inside of this generator of large series and is supplied from outside the inductor coil.

  Of course it is necessary to modify the brackets that these flanges present so that they are distributed evenly to avoid unbalance; these tabs being fixed on the carrier element 21 of the rotor 5, while the pulley of the document FR A 2 676 273 is replaced by a fastener, such as a disc such as the bottom 162 of FIG.

  Alternatively (Figure 4), the plate is fixed on the other side of the flange 21, the shaft 19 then passing inside the inner wall 63.

  The flange 21 as a variant locally has a portion axially offset in the direction opposite to the inner wall 63 for creating a cavity 122 for receiving the free end of the wall 63 so that the internal chamber 65, 268 is extended and is at least as long as the upper chamber 64.

  The flange 21 is therefore generally transverse orientation.

Claims (13)

21 CLAIMS,   1 - Electromagnetic retarder (1), in particular for a motor vehicle, comprising an annular-shaped stator (6) and an annular-shaped inductor rotor (5) mounted coaxially with respect to the stator (6) and provided with at least one coil (7) mounted on a core (67), wherein the rotor (5) is inserted into the stator (6) and wherein the stator (6) is configured to have at least one outer cooling chamber (64) ), which at least partly surrounds the coil (7) of the rotor (5), characterized in that the stator (6) is configured to also have at least one inner cooling chamber (65), which is surrounded at least by part by the coil (7) of the rotor (5).   2 retarder according to claim 1, characterized in that the stator (6) has, on the one hand, at its outer periphery an outer wall (61) and, on the other hand, an inner wall (63) surrounded at least by most of the outer wall (61) and in that said outer and inner chambers are respectively carried by the outer walls (61) and inner (63) of the stator (6).   3 retarder according to claim 2, characterized in that the outer walls (61) and inner (63) are connected transversely by a bottom (62) and in that the core (67) and the coil (7) penetrate into the space delimited by the two walls (61, 63).   4 retarder according to claim 3, characterized in that the inner walls (63) and outer (61) define a blind annular cavity within which penetrate the core (67) and the coil (7).   A retarder according to claim 3 or 4, characterized in that the rotor (5) comprises a plurality of separate cores (67) of oblong shape carrying the coils (7).   6 retarder according to claim 5, the cores (67) are fixed to a carrier element (21) generally transverse orientation, such as a flange or a veil, and extend axially cantilevered relative to this carrier element (21).   7. A retarder according to claim 6, characterized in that at least one retaining ring (37) is mounted at the free axial end of the cores (67) to properly hold them.   8 retarder according to claim 6 or 7, characterized in that the retaining ring (37) and the carrier element (21) are non-magnetic material, while the stator (6) and the cores (67) are in magnetic material.   9 retarder according to any one of the preceding claims, characterized in that adjustment means, such as a distribution valve, are provided to adjust the percentage of flow rates in the inner chamber (65) and outer (64).     Retarder according to any one of claims 1 to 8 taken in combination with claim 3, characterized in that at least one of the inner (65) and outer (64) chambers extends into the bottom (62).   A retarder according to claim 10, characterized in that the two chambers (64, 65) are extended in the bottom to meet and form a single chamber.   12 retarder according to any preceding claim, characterized in that it is positioned offset from a transmission of motion to at least one wheel of the motor vehicle.   13 _ A retarder according to claim 12, characterized in that it is mounted on a secondary output shaft of the gearbox of the motor vehicle.   14 - retarder according to claim 12 or 13 characterized in that the electromagnetic retarder is positioned offset relative to one of the transmission element secondary output shaft movement of the gearbox, said transmission element, in such a way an axis of the electromagnetic retarder corresponding to an axis (9) of the rotor and to an axis (15) of the stator of this retarder is parallel to an axis (14, 14 ') of said element.   15 - retarder according to claim 14, characterized in that the electromagnetic retarder is connected to said transmission element by a speed multiplier device (16).   16 - retarder according to claim 15 characterized in that the speed multiplier device (16) comprises a gear device.   17 retarder according to claim 15 or 16, characterized in that the speed multiplier (16) intervenes between a shaft that has the said transmission element (4, 4 ') and a shaft (19) integral with a rotor (5). ) that presents the electromagnetic retarder.   18 - retarder according to one of the preceding claims taken in combination with claim 6, characterized in that it comprises a current generator for supplying the coil (7) and in that the coil (7) and the current generator are arranged on either side of the carrier element (21).   19 retarder according to claim 18, characterized in that the current generator comprises brushes mounted in cages carried by the stator (6) to rub against rings carried by an annular rim of axial orientation integral with the carrier member. (21).     Retarder according to Claim 18, characterized in that the current generator consists of an alternator comprising an inductor stator carried by the stator (6) and an induced rotor (32) carried by an annular rim of axial orientation integral with the element. carrier (21).   21 retarder according to claim 18, characterized in that the alternator is provided, on the one hand, with a claw inductor stator fixing on an extension of the connection bottom (62) of the induced stator (6) of the electromagnetic retarder and, on the other hand, a polyphase-type induced rotor that attaches to the carrier element (21).