EP1527509A1

EP1527509A1 - Electromagnetic retarder for a vehicle provided with a speed increasing unit

Info

Publication number: EP1527509A1
Application number: EP03787847A
Authority: EP
Inventors: Zeng Gang Liu
Original assignee: Telma SA
Current assignee: Telma SA
Priority date: 2002-07-29
Filing date: 2003-07-09
Publication date: 2005-05-04
Also published as: FR2842961A1; WO2004017502A1; FR2842961B1; CN1672312A; US20060226700A1

Abstract

The aim of the invention is to reduce the weight and sizes of an electromagnetic retarder (1) for a vehicle by coaxially offsetting said electromagnetic retarder with respect to the transmission (4) of the vehicle, the retarder being provided with a cooling cavity. In order to coaxially offset the retarder, a speed increasing gear (16) is incorporated between said electromagnetic retarder and transmission.

Description

ELECTROMAGNETIC RETARDER OF A VEHICLE PROVIDED WITH A SPEED MULTIPLIER

Field The invention relates to an electromagnetic retarder of a vehicle provided with a speed multiplier device. The invention aims to increase the performance of such a retarder, to reduce the weight and size of this retarder. The invention is more particularly intended for the field of trucks, coaches and buses, that is to say motor vehicles of the “heavy goods” type, but can also be applied in other fields.

State of the art

An electromagnetic retarder makes it possible to assist a vehicle braking device, in particular for vehicles of the "heavy goods" type. A braking device may include brake pads intended to approach against at least one disc of a hub of a wheel of a vehicle to brake the vehicle. There are several types of electromagnetic retarders. In particular, there are electromagnetic retarders of the axial type, electromagnetic retarders of the "Focal" type (registered trademark) and electromagnetic retarders of the "Hydral" type (registered trademark). An axial type electromagnetic retarder is intended to be placed on the movement transmission line between a bridge and a vehicle gearbox; the transmission shaft then being in two parts for mounting therebetween the retarder. An electromagnetic retarder of the "Focal" type is intended to be placed directly on a drive shaft at the outlet of the gearbox or directly on the vehicle deck. The axle of a vehicle drives at least one wheel shaft, which wheel shaft drives at least one wheel of the same vehicle. An electromagnetic retarder of the "Hydral" type is also provided to be placed directly on a drive shaft at the outlet of the gearbox. This type electromagnetic retarder

"Hydral" is particularly suitable for vehicles with a short shaft line.

Such an electromagnetic retarder of the "Hydral" type, described for example in the document FR A 2 627 913 and its correspondents EP-A-331 559 and US-A-4 864 173, comprises at least one induced stator and at least one inductor rotor. The induced stator may have a hollow circular cylindrical shape allowing the induction rotor, also comprising 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 axial or "Focal" type retarders it is the opposite, the stator then being an inductor stator carrying the coils, while the rotor is an induced rotor.

Generally, electromagnetic retarders have 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 electric wire in 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 direction of winding of the electric wire, which axis of the coil coincides with the axis of the core. In the case of the electromagnetic retarder of the "Hydral" type, the coils, each carried by a protruding core, 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 in the plane of the induced stator.

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

In the case of a retarder of the aforementioned "Hydral" type, this magnetic field is formed by traversing the core of the first coil carried by the induction rotor along an axis of this first coil and then enters the stator, perpendicular to a plane of the stator. The plane of the stator can be formed by the wall of the stator, for example made 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. The magnetic field then joins the core of the second coil, leaving it perpendicularly from the plane of the stator and along an axis of this second coil. Finally, the magnetic field forms a loop by joining the first coil again, passing from the second coil through the rotor. When the electromagnetic field crosses the plane of the stator perpendicularly, an electric current or eddy current is created in the stator due to the displacement of the rotor.

Indeed, in application of Faraday's law, an electric conductor which 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 maximum when the field is perpendicular to the speed. Everything happens as if an electric voltage were produced in places of the rotor where each of the axes of the coils intersects the plane of the stator, whereas between these two places no voltage is produced. Between these places the magnetic field, tangential to the plane of the rotor, is parallel to the direction of movement of the rotor. The eddy currents which arise are located in the places of the stator where the magnetic field crosses the stator.

More particularly, the eddy currents are born in the stator only at the place where there is a perpendicular component of the magnetic field relative 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 speed of rotation of the shaft of the vehicle, the rotor being linked to the transmission shaft, the transmission shaft itself being linked to at least one wheel of the 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 by the perpendicular crossing of the plane of the stator of at least one magnetic field between two coils.

To cool the electromagnetic retarder following an overheating of the stator wall by eddy currents, the stator wall carries a cooling cavity or surface inside which a fluid is intended to infiltrate and circulate to cool the stator.

To increase the performance of such electromagnetic retarders, it is possible to increase the number of coils. By increasing the number of coils, the power of such an electromagnetic retarder can become higher due to the increase in places in the stator where the power of the eddy current is maximum resulting from the increase in the number of pairs of corresponding coils.

It is still possible to increase the number of coils by reducing the size of the coils to make the increasingly bulky retarders even more powerful. In addition, the production of such an electromagnetic retarder with a high number of coils can increase the manufacturing cost of such a retarder.

However, we realized that by increasing the number of coils we increased the weight and size of such a retarder. In addition, this is likely to increase the cost of such a retarder.

Subject of the invention

To reduce the weight and size of these electromagnetic retarders, the invention provides for positioning the electromagnetic retarder offset from the transmission.

To position the electromagnetic retarder offset from the transmission, a speed multiplier can be interposed between the transmission and the electromagnetic retarder. This speed multiplication device integrated into the electromagnetic retarder makes it possible to increase the performance of the electromagnetic retarders. This speed multiplication device can be a gear speed multiplication device, possibly with a bevel gear. This gear speed multiplier is constructed in such a way that the transmission cooperates with the retarder via a first disc and a second disc 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 are inserted between the teeth of the second disc by complementarity and vice versa. So that the rotational speed of the rotor increases, the first disc has a larger size than the second disc.

By positioning the electromagnetic retarder offset from the transmission, it is possible to reduce the size of this retarder by reducing its size. The reduction in the size of the electromagnetic retarder is possible because it is no longer necessary to pass the transmission directly through the electromagnetic retarder.

Since the reduction in the size of the electromagnetic retarder can lead to a decrease in the thermal capacity of the electromagnetic retarder, the invention also provides for extending the cooling surface of the stator. The cooling cavity or cooling surface is then extended by extending the wall of the stator at one end of the stator generally perpendicularly and in the direction of an axis of the stator. The portion of the extended wall is then, for example, hollowed out in continuity with the cooling surface to form a front cooling surface.

In general, the portion of the extended wall carries an extension of the cavity or cooling surface.

Following the increase in the speed of rotation of such an electromagnetic retarder provided with this speed multiplier device, the wall of the stator tends to heat up considerably. The invention then also provides for cooling of the wall of the stator by a fluid, in particular by water. Water is a fluid particularly suitable for cooling such a wall of the stator confronted with such an increase in heat. But another fluid might be suitable.

The subject of the invention is therefore an electromagnetic retarder, in particular for a vehicle, disposed between a brake pedal and between at least one wheel of the vehicle, intended to assist braking of the vehicle by means of a transmission and comprising a stator cooled by circulation of a cooling fluid circulating in at least one cavity carried by said stator, characterized in that it is positioned offset from the transmission.

Brief Description of the Drawings The invention will be better understood on reading the description which follows and examining the accompanying figures. These are presented for information only and in no way limit the invention. The figures show:

- Figure 1: a schematic representation of an electromagnetic retarder of a vehicle, according to the invention; - Figure 2: a perspective representation of an electromagnetic retarder of a vehicle, according to the invention;

- Figure 3: a perspective representation of an electromagnetic retarder of a vehicle, according to a variant of the invention.

Description of preferred embodiments of the invention

FIG. 1 shows an electromagnetic retarder 1, in particular for a vehicle, arranged between a brake pedal 2 and between at least one wheel of the vehicle 3 and intended to assist the braking of the vehicle via a transmission 4, according to l 'invention. The electromagnetic retarder 1 comprises at least one inductor rotor 5, at least one induced stator 6 and at least one coil 7. In the example in FIG. 1, this electromagnetic retarder is an electromagnetic retarder of the "Hydral" type, described for example in the Document FR A 2 627 913 cited above, which may be referred to for more details, but could be an electromagnetic retarder of axial type or of Focal type, as previously mentioned. A Focal type retarder is described, for example, in document FR A 2 577 357 to which reference may be made for more details. In this same example of FIG. 1, the rotor 5 is inserted inside the stator 6 intended to be mounted on a fixed part of the vehicle, here the chassis 11. A slight clearance, called air gap, is present between the rotor 5 and the stator 6 for producing an electromagnetic connection described below.

The stator therefore surrounds the rotor, which both have an annular shape and are coaxial. The axial axes of symmetry 9, 15, respectively of the rotor and the stator, here made of ferromagnetic material, are combined.

The rotor has a wall with a hollow circular cylindrical shape fitting into a wall of the stator also comprising a complementary hollow cylindrical circular shape. The aforementioned walls are therefore of axial orientation considering the axes 9,15. The rotor wall defines an external face 8 remote from the axis 9 of the rotor and an internal face 10 close to the axis of the rotor. The coil 7 is carried by the external face 8 of the wall of the rotor and is intended to form a magnetic field between the rotor 5 and the stator 6. The rotor can carry at least one coil 7 and it is for this reason that the external face 8 is in Figure 1 hollowed out in 29 in a U-shaped section to receive the coil 7 as described below. In an example in FIG. 2, the rotor can carry several coils and have mounting grooves 25 for this purpose. Preferably, the rotor can carry a pair number of coils. The wall of the stator carries at least one cooling cavity or surface 13 inside which is intended to circulate a cooling fluid. This fluid, such as water, is intended to cool the wall of the stator.

Here the stator wall is hollowed out internally to form the cooling cavity. As a variant, as described in document EP-A-331 559, the cavity is formed by means of a pipe extending in a helix around the wall of the stator while being carried by this wall.

This pipeline is terminated by two inlet and outlet fittings. As a variant, the cavity is delimited by the wall and by a cover attached to it.

One of the cover - wall elements has a hollow shape to create the cavity.

As a variant, the wall and the cover have a hollow shape. In general, all the embodiments described in document EP-A-331 559 (US-A-4 864 173) can be envisaged and the coolant is advantageously water with added antifreeze. This coolant is advantageously the coolant of the heat engine, the pump and the heat exchanger of the cooling circuit being advantageously the water pump, and the radiator for cooling the motor vehicle.

The electromagnetic retarder is connected on the one hand to a chassis 11 and on the other hand to the transmission 4 comprising a transmission shaft, the axis of which is shown at 14. The connection of the electromagnetic retarder to the chassis is carried out via at least one connecting means 12. This connecting means 12 is here arranged on the stator to connect the stator to chassis 11. The electromagnetic retarder is linked to the transmission by means of the rotor 5.

According to a characteristic of the invention, the electromagnetic retarder is positioned offset from the transmission 4. The offset position of the electromagnetic retarder from the transmission can be produced coaxially so that an axis of the electromagnetic retarder is offset parallel to an axis 14 of the transmission 4. An axis of the electromagnetic retarder corresponds to the axis 9 of the rotor, itself corresponding to an axis 15 of the stator. The size and therefore the size and weight of the retarder can be reduced.

The offset position of the electromagnetic retarder with respect to the transmission can be achieved by means of a speed multiplier device 16. This speed multiplier device can be a gear device comprising for example two toothed wheels described below. However, this speed multiplier device could be a belt speed multiplier device or else a chain speed multiplier device. Thanks to these provisions, the weight and size of the retarder are further reduced; the heat being released by circulation of the cooling fluid inside the cavity of the induced stator 6.

This gear speed multiplier device comprises a first disc 17 and a second disc 18 each belonging to a toothed wheel. The first disc 17 is interposed in the transmission 4 while being integral with the shaft thereof so that a plane of this first disc is perpendicular to the axis 14 of the transmission. The second disc

18 is carried by the rotor 5 via an arm 19, which arm is fixed to the rotor of the electromagnetic retarder. More specifically, the arm 19 comprises a shaft at one end of which the disc 18 is fixed. The shaft has an axis coincident with the axes 9,15 and enters the rotor. At its other end, the shaft is provided with a transverse orientation plate with respect to the axes 9, 15 for its attachment to at least one transverse prominence 26, described below, which the rotor has internally. The arm

19 is generally in the form of a valve on the free end of which the disc 18 is fixed. This second disc 18 is thus placed so that a plane of this second disc is perpendicular to the axis 9 of the rotor. Thus, the first disc and the second disc both have a plane parallel to each other. The first disc and the second disc are arranged in such a way that they are placed one below the other along a plane perpendicular to the axis 14 of the transmission 4 and to the axis 9.15 of the electromagnetic retarder. .

The first disc and the second disc have at their periphery 20 and 21 respectively a series of teeth so that two toothed wheels are formed. The transmission 4 and the electromagnetic retarder 1 cooperate by the insertion of each of the teeth of the first disc 17 between each of the teeth of the second disc 18 by complementarity and vice versa, FIG. 1. The shape of the teeth is produced in such a way that the teeth can fit in by complementarity. Thus, the teeth can be triangular in shape so that the points extend radially with respect to a center of the first disc and to a center of the second disc. The center of the first disc can correspond to a place on the first disc where the axis of the transmission is likely to cross the first disc. The center of the second disc can correspond to a place on the second disc where the axis of the retarder is likely to cross the second disc. Or the teeth may have a rectangular, trapezoidal shape or advantageously an involute profile in an arc like the conventional gears.

Thus, the transmission communicates a rotational movement to the first disc, which first disc also communicates a rotational movement to the second disc via the teeth. The second rotating disc thus drives the rotation of the inductor rotor via the arm 19.

To increase the speed of rotation of the rotor, the first disc 17 has an external diameter 22 greater than the external diameter 23 of the second disc 18. The increase in the speed of rotation of the rotor is carried out in such a way that the second disc can thus turning on itself several times to travel entirely around the periphery 20 of the first disc 17. The increase in the speed of rotation of the rotor is therefore proportional to the decrease in the diameter 23 of the second disc by compared to the diameter 22 of the first disc. The second disc of size smaller than that of the first disc is therefore a pinion.

As a variant, the discs are perpendicular and the tapered cheek teeth so that the axis of the retarder is perpendicular to that of the transmission. The multiplier device 16 is then with a conical clutch.

An electromagnetic retarder operates as follows. During braking of the vehicle, a magnetic field is created formed by at least one coil carried here by the inductor rotor. This magnetic field passing through the stator is at the origin of the formation of the eddy currents in the induced stator made of magnetic material, advantageously ferromagnetic. Passing through the stator, the magnetic field creates an area of eddy currents at a place in the stator where the magnetic field crosses the plane of the stator perpendicularly. As previously mentioned, the plane of the stator is formed by the wall of the stator. Eddy currents are electric currents which are all the more powerful as the magnetic field forming between the coils tends to be perpendicular to the direction of rotation of the rotor. The direction of rotation of the rotor is a direction perpendicular to the plane of the sheet of the drawing in Figure 1 and is represented by a point 28 in Figure 1. By being perpendicular to the direction of rotation of the rotor, the magnetic field forms eddy currents which tend to oppose the rotational movement of the rotor. By opposing the direction of rotation of the rotor, the eddy currents cause the braking or slowing down of the rotational movement of the rotor indirectly transmitted by the transmission, according to the invention. Braking controlled by the pressing of a driver's foot 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 in the direction of at least one vehicle wheel. Such positioning of the electromagnetic retarder in offset, here transverse, with respect to the transmission, makes it possible to reduce, as mentioned above, the size of the electromagnetic retarder because it is no longer necessary to pass the transmission directly through the interior of the rotor. . The transmission is linked to the retarder indirectly via the arm 19 which can thus have a smaller diameter than a diameter of the transmission. However, decreasing the size of the electromagnetic retarder can result in a decrease in the thermal capacity of the electromagnetic retarder. By thermal capacity is meant the quantity of stator material capable of being heated, in particular by eddy currents. During the operation of the electromagnetic retarder, the stator thus reduced is then rapidly heated following the circulation of the eddy currents in the wall of the stator. Heating the stator can cause a reduction in the performance of the retarder because heat tends to prevent the formation of eddy currents in the stator.

This is why according to the invention, owing to the fact that the transmission is offset with respect to the retarder, that the wall of the stator is extended, here generally transverse with respect to the axis 9.15, in order to increase the cooling surface. . The stator has one end 32 remote from the second disc 18 and one end 33 close to the second disc 18. The wall of the stator is thus extended perpendicularly and in the direction of the axis 9 of the rotor at the end 32 of the stator remote from the second disc. 18. Thus, it is possible to increase the cooling surface of the stator by also extending the cavity 13 of the stator. To extend the stator cavity, a portion of the wall corresponding to the extended wall perpendicular to the axis 9 of the stator can be hollowed out to form a front surface 24 generally of transverse orientation.

As a variant, the wall is extended generally transversely to carry a generally transverse extension of the above-mentioned pipe forming the cavity.

As a variant, the aforementioned cover is extended generally transversely to be carried by the generally transverse extension of the wall and delimit with this extension the extension of the cavity 13. In fact, the wall carries a cavity in the aforementioned manner, for example being dug to form the cavity. The wall could also carry several cavities. Preferably the wall is hollowed out with a single cavity. This cavity is intended to be filled with a fluid allowing the cooling of the stator wall during the increase in rotational speed of the rotor. This fluid circulates in the cavity. The fluid is intended for fill the cavity and cool the stator wall may be water. Water is a fluid particularly well suited to a very strong increase in the heat of the stator wall following an acceleration of the rotational speed of the rotor. But the fluid could also be another liquid. The fluid could also be air. The cavity of the stator could be placed in communication with another device (not shown) outside or forming part of the electromagnetic retarder intended to cool the fluid circulating in the cavity 13 of the stator. This device would allow the fluid to circulate inside the stator and to leave it to be cooled by this same device. For eddy currents to form in the stator, prior excitation of at least one coil is necessary for the formation of a magnetic field. A prior excitation can be obtained by means of an excitation alternator such as that represented in the document FR A 2 627 913 cited above. The alternator, shown diagrammatically in 200 in FIG. 1, comprises an inductor stator with multiple poles surrounding at low clearance, that is to say with the presence of an air gap, an induced rotor of the polyphase type, for example of the three-phase type. The poles are created by a ring of electromagnets with alternating polarities connected to a direct current source, such as the vehicle battery. The electromagnetic connection between the rotor and the stator is made through the air gap between the rotor and the stator of the alternator without mechanical contact. An adjustment circuit is provided to adjust the intensity of the inductor stator as desired. The adjustment circuit includes a manual adjustment member, such as a lever. The adjuster is alternatively associated with the brake pedal. This alternator is started following the pressing of a driver's foot on the brake pedal and / or on a aforementioned lever provided for this purpose. The alternating current collected at the phases of the induced rotor is rectified by a rectifier bridge, for example of the diode type, before being applied to the coil (s) 7 to electrically supply them. For more details, reference is made to FIGS. 1 and 2 of document FR A 2 627 913. The rotor 5 and the stator 6 are therefore in one embodiment extended axially at the level of the end 33 in order to carry the rotor and the alternator stator.

According to the invention, this excitation alternator is therefore placed in the electromagnetic retarder. In particular, this alternator is positioned in partly in the induction rotor and partly in the induced stator.

As a variant, the excitation alternator has the constitution of a mass-produced motor vehicle alternator, such as that with internal ventilation described in document FR A 2 676 873 (US-A-5 270 605) to which reference will be made. more information. More precisely, it suffices to reverse the structures. In other words, the claw and excitation coil rotor of document FR A 2 676 873 becomes via its shaft, integral with the chassis and therefore with the stator 6 of the retarder of the invention, while the two flanges of form hollow of this document FR A 2 676 873, assembled together using screws or any other means to form a casing carrying the polyphase stator as well as the rectifier bridge, become integral with the rotor 5 of the retarder and with the arm 19. This is made possible by the fact that each of the flanges centrally carries a ball bearing intervening between this flange and the axial end concerned of 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 excitation stator or inductor stator. This rotor comprises a body in the form of a packet of grooved sheets for mounting a winding comprising several windings connected to the rectifier bridge for supplying electrical power to the coils 7. The stator comprises two pole claw wheels with presence between them ci of a core carrying an inductor winding. In this case, the regulator mounted inside this mass-produced alternator is removed and the field winding is supplied from the outside. Of course, it is necessary to modify the fixing lugs presented by these flanges so that they are evenly distributed to avoid any imbalance; these tabs being fixed on the internal projections 26 of the rotor 5, while the pulley of document FR A 2 676 273 is replaced by a fixing member, such as a disc, intended to be fixed to the edge of the central opening of the perpendicular extension of the end 32 of the induced stator 6.

It is also necessary to modify the flange carrying the diode rectifier bridge so that this flange carries spacers, for example coming from molding with the latter, used for fixing the arm 19. As a variant, this flange constitutes a cover, as visible for example in FIG. 9 of application PCT / FR 02/01631; the arm 19 attaching to the chimneys that this flange. The rectifier bridge is then electrically connected to the coils 7 to electrically supply the latter. The alternator is in this case located at least in major part inside the inductor rotor 5 of hollow form. This is made possible thanks to the invention. To carry the coils 7, the inductor rotor 5 has on its external face 8 at least one core in the form of a protuberance 25 extending radially and perpendicularly to the axis 9 of the rotor and in the direction opposite to the axis of the rotor, FIG. 2. The protuberance 25 forms a projecting pole and is made of magnetic material, advantageously ferro-magnetic. These axially oblong protrusions form a support around which a coil 7 is formed. The rotor can have an even number of protrusions so that the coils can form a magnetic field per pair of coils. At least one protrusion 26 extending radially in the direction of the axis 9 of the rotor is also disposed on the internal face 10 of the rotor. In one example, the rotor can have four protrusions and these protrusions can be connected together by a ring 27. These protrusions allow the insertion and fixing of the arm 19 carrying the second disc 18 of the speed multiplication device 16. The arm 19 can be inserted into the rotor by being fixed on the ring 27.

A magnetic field can form from one coil to another coil passing through the protuberance of each of these coils. The magnetic field is intended to cross the plane of the stator and the plane of the rotor. By crossing the plane of the stator, the magnetic field firstly crosses the plane of the stator a first time perpendicularly, then in parallel the plane of the stator, and finally a second time perpendicularly the plane of the stator to reach the rotor. Between the two places where the magnetic field crosses the stator perpendicular to the plane of the stator, the magnetic field is parallel to the direction of rotation of the rotor. The direction of rotation of the rotor is represented by an arrow, figure 2. According to the example figure 2, the zones of eddy currents are formed only in the places where the magnetic field crosses perpendicularly the plane of the stator.

To improve the power of such an electromagnetic retarder capable of being supplied by the eddy currents passing through the stator, it is possible to arrange the coils on the rotor according to another variant of the invention, Figure 3. Figure 3 shows in perspective the position of the coils according to this other variant of the invention. According to this other variant, the coils are arranged on the rotor so that the magnetic field formed by these coils has a radial configuration relative to the rotor axis. According to this radial configuration in FIG. 3, the coils can be arranged in such a way that they form a magnetic field passing through the stator always perpendicular to the direction of rotation of the rotor. According to this variant, there is more than a single coil wound around the rotor. It is also in this variant that the electromagnetic retarder of FIG. 1 is represented. According to this radial configuration, the magnetic field formed by this single coil in the stator always crosses perpendicularly then parallel the plane of the stator but circulates at l inside the stator perpendicular to the direction of rotation of the rotor. According to this example in FIG. 3, the eddy currents are at their maximum power during their entire crossing in the stator.

To do this, the rotor is hollowed out in its wall on the side of the external face 8 perpendicularly and in the direction of the axis 9 of the rotor or of the axis 15 of the stator of a cavity 29 all along the rotor. This cavity is intended to accommodate a magnetic coil. This cavity is delimited by one end 34 of the rotor close to the end of the rotor and close to the second disc 18 and by another end 35 close to the end 32 of the stator and distant from the second disc and located opposite the front surface. 24 of the stator. According to this radial configuration, these two ends 34 and 35 of the rotor are hollowed out with at least one window each. At least one window 30 is shown in Figure 3 on the end 34 of the rotor. These windows are formed radially with respect to the axis 9 of the rotor and are hollowed out in the direction of this axis. Between these windows are thus delimited tongues 31 corresponding to a portion of the wall of the rotor. A magnetic field can thus form from a tab on one end to another tab on the other end of the rotor. The magnetic field formed between two tabs is produced in such a way that it always crosses the stator perpendicular to the direction of rotation of the stator. Due to its perpendicular position relative to the direction of rotation of the stator, the field magnetic can thus create an area of eddy currents of a power as high as in the two places where the magnetic field crosses peiculendicular to the plane of the stator. This variant according to the invention in FIG. 3 makes it possible to further increase the performance of such an electromagnetic retarder without the need to increase the weight or the size of the retarder or of the coils.

In Figure 1 the rotor is also extended peφendiculément and this in the direction of the axis 9. This extension of transverse orientation extends opposite the surface 24 of the stator 6 in the vicinity of the end 32 thereof. This extension is hollowed out to form an annular mounting cavity 129 intended to receive a magnetic coil 107 perpendicular to that housed in the annular cavity 29.

Of course, at least one bearing 300 intervening between the shaft of the arm 19 and the chassis is advantageously provided to support the shaft 19 and guarantee the air gap between the stator 6 and the rotor 5.

As a variant, the discs 17 and 18 are replaced by pulleys for receiving a belt intervening between the two pulleys.

Alternatively the two discs are spaced from each other and connected by a chain. All these variants represent various forms of a speed multiplier acting between the transmission 4 and the arm 19 integral with the rotor 5.

Thus, as mentioned above, the discs 17 and 18 can be perpendicular and form a bevel gear. The retarder can therefore be installed peφendicularly with respect to the transmission 4.

As a variant, the front wall 24 could be slightly inclined so that it is generally of transverse orientation.

The wall of the sator, as a variant, is not of constant thickness. As a variant, the retarder is of the axial or Focal type so that the arm 19 is fixed to the induced rotor.

Claims

1 - Electromagnetic retarder (1) for a vehicle disposed between a brake pedal (2) and between at least one wheel (3) of the vehicle, intended to assist braking of the vehicle by means of a transmission (4), and comprising a stator (6) cooled by circulation of a fluid circulating in at least one cavity (13) carried by the stator (6), characterized in that it is positioned offset from the transmission.

2 - Retarder according to claim 1, characterized in that the electromagnetic retarder is positioned offset from the transmission so that an axis of the electromagnetic retarder corresponding to an axis (9) of the rotor and an axis (15) of the stator of this retarder is parallel to an axis (14) of the transmission.

3 - Retarder according to claim 1, characterized in that the electromagnetic retarder is connected to the transmission (4) by a speed multiplier device (16).

4 - Retarder according to claim 3 characterized in that the speed multiplier device (16) comprises a gear device.

5 - Retarder according to claim 4, characterized in that the speed multiplier (16) intervenes between a shaft that has the transmission (4) and an arm (19) integral with a rotor (5) that has the electromagnetic retarder.

6 - Retarder according to claim 1, characterized in that it comprises - an induced stator (6) and an inductor rotor (5), the rotor being inserted in the stator and being intended to turn around an axis ( 15) of the stator, and

a wall of the induced stator carrying at least one cooling cavity (13), which cooling cavity is extended by an extension carried by the wall of the stator which extends at one end (32) of the stator generally peφendicularly in the direction of an axis (9) of the rotor corresponding to the axis (15) of the stator.

7 - Retarder according to claim 6, characterized in that the electromagnetic retarder comprises, on the one hand at least one coil and, on the other hand, an excitation alternator for an electrical supply of the coil (7) of the electromagnetic retarder . 8 - Retarder according to claim 7, characterized in that the alternator is located at least for the most part inside the inductor rotor (5) of hollow shape of the electromagnetic retarder.