Driving wheel unit for an electric traction vehicle

Abstract: A driving wheel unit suitable for an electric traction vehicle. The unit consists of a stub axle joined to a vehicle wheel suspension, a wheel hub mounted idle on the axle and capable of being fitted angularly and integrally with a wheel of the vehicle, a first enclosing element fixed angularly and integrally to the hub, peripherally projecting from it in a radial direction, at least one permanent magnet supported peripherally by the first enclosing element so as to define therewith a rotor of an electric motor, and a stator of an electric motor joined integrally with the stub axle and composed of at least one coil connectable to a source of electric power and of a second enclosing element coaxial with and facing the first and supporting peripherally said coil.

Description: The present invention refers to a driving wheel unit suitable for an electric traction vehicle. For the propulsion of electric traction vehicles it is known to be advantageous to use, instead of a single motor attached by a mechanical transmission to the driving wheels, several motors mounted directly on the driving wheels. From European patent application number 0345123, for example, one technical solution is known in which all four wheels of a vehicle are each provided with a respective independent propulsion unit. Each unit is suspended from two swinging suspension arms in an articulated quadrilateral arrangement, and has an output shaft; the respective wheel of the vehicle is fitted directly to the output shaft. From EP-A-0337032, corresponding to the preambles of Claims 1 and 5, and EP-A-0464929 are known solutions similar as that above, but wherein the motor components are partly integrated in the wheel support unit structure Anyway, t he solution described in these European patent applications are still not free from inconveniences: in particular, they requires the use of specially produced wheels and there are serious problems in accommodating and supporting the braking devices; finally it results in a relatively complex, heavy structure. An aim of the invention is to produce a driving wheel unit for propelling an electric traction vehicle which has a simple and light structure, on which the wheels normally on sale for vehicles with endothermic engines currently in circulation can be mounted, and which is compact. To this end, a driving wheel in accordance with the present invention is characterized by the features specified in the characterizing parts of Claims 1 and 5 . For a better understanding of the invention, a non-limitative description is now given of one embodiment thereof, with reference to the appended drawings, in which: figure 1 illustrates a vehicle suspension fitted with a driving wheel unit produced according to the invention; and figure 2 illustrates on an enlarged scale the driving wheel unit of figure 1. With reference to figures 1 and 2, there is indicated as a whole by 1 a driving wheel unit suitable for an electric traction vehicle otherwise known and not illustrated for simplicity, provided on board with a suitable electric power supply also of a known type and not illustrated for simplicity, for example batteries. The unit 1 comprises a stub axle 2 and a hub 3, both of a known type, on which, according to the invention, are fitted respectively a stator 4 and a rotor 5 of an electric motor 6, of a generally known type. The stub axle 2 is joined in a known manner to a suspension 7 of the vehicle, which in the non-limitative example illustrated is of the rigid axle type, and comprises an axle 8 which has stub axle 2 joined integrally to it, and a shock absorber 9 joined to the body 10 of the vehicle and to the axle 8. It is obvious that, according to a possible variant not illustrated, the wheel unit 1 can also be supported by an independent type wheel suspension, for example the "McPherson" type, by simply joining the stub axle 2 in a known manner directly to the suspension upright, in turn joined to a typical shock absorber 9. The stub axle 2 supports the hub 3 idle in a known manner, for example by a roller bearing 11 fastened axially against a shoulder 12 of stub axle 2 by a nut 13. The hub 3 in turn supports, in a known manner, a wheel 14 of any known type commonly used on road vehicles. In particular, the wheel 14 is fixed by means of bolts 15 and a flange 16 to the hub 3, which is provided as part, and on the outside periphery, of a known brake drum 18. Integral with stub axle 2 is mounted a brake support bracket 20, which is positioned facing flange 16 of hub 3 and supports in a known manner respective known brake shoes 21 (only one of which is visible in figure 2) capable in use of entering into frictional contact with the drum 18 to brake the rotation of the wheel 14 with respect the stub axle 2, and a known hydraulic control device 22 for the brake shoes 21, attachable in a known manner not illustrated for simplicity to the brake circuit of the vehicle. In the example, the bracket 20 is connected to the axle 8 by means of bolts 23. If the suspension 7 is substituted by an independent type wheel suspension, the bracket 20 is then connected to the suspension upright or is integral thereto. According to the invention, the unit 1 further comprises a first enclosing element 25 of electric motor 6 fixed angularly and integrally to hub 3 projecting peripherally from it in a radial direction, at least one permanent magnet 26 (in the example several permanent magnets 26 arranged in a ring) supported peripherally by enclosing element 25 which, together with the magnet(s) 26, therefore defines the rotor 5, a second enclosing element 28 positioned coaxially with and facing element 25 and connected integrally with the stub axle 2, and at least one coil 29 of a known type (in the example several coils 29 arranged in a ring) connectable in a known manner not illustrated for simplicity with the said electric power supply and supported integrally by element 28 which, together with the coil(s) 29, thus defines the stator 4. Elements 25,28 are both cup-shaped, positioned with the concavities facing each other, and each comprises a respective radially external front peripheral edge, indicated respectively by 31 and 32. These edges 31,32 cooperate with each other without touching to define between elements 25,28 which, in use are in relative rotation, a labyrinth seal to protect the motor 6. In particular element 25 comprises a semi-toroidal element 33 of pressed sheet metal joined integrally to wheel hub 3 on brake drum 18, and an annular element 34 supporting the magnets 26 and positioned inside the semi-toroidal element 33 partially projecting outside it in an axial direction with a portion 35 thereof of smaller diameter joined to a lateral wall 36 radially external to semi-torioidal element 33. One end of the lateral wall 36 is provided radially outwards with a rim 40 which, together with projecting part 35 of element 34, separated from the rest of element 34 by an annular channel 41, delimits the said edge 31 of semi-enclosure 25, which thus has an overall shape conjugate with that of edge 32, which in radial section is substantially Z-shaped and faces rim 40 radially external thereto and to projecting portion 35 of element 34, thus creating a sinuous labyrinth seal between elements 25,28. Enclosing element 28 is in radial section substantially J-shaped in a position parallel with the wheel axle and, in the example, is obtained as part of brake support bracket 20 on the external periphery thereof. The stator 4 and rotor 5 are dimensioned with maximum external diameters which enable them to be housed entirely inside the wheel 14. Consequently, in use, the unit 1 can be fitted with a standard wheel and perform all the functions of a normal driving wheel unit, including that of braking the wheel 14, in the example by means of a braking device with a known drum already in general use. When current is supplied to the coil(s) 29, a rotating magnetic field is produced which acts on magnets 26 rotating the rotor 5 with respect to the stator 4. Motion is thus also transmitted to the hub 3 driving the wheel 14 without the need for mechanical transmission. From what has been described, the advantages of the invention are evident. An integrated driving wheel unit of compact dimensions and great simplicity is obtained. It can be produced largely with standard components and is also fitted with braking devices. In particular, the cost of such a unit can be very low, since the electric motor 6 is integrated into the wheel unit simply by attaching to the periphery of otherwise standard parts, such as hub 3 and brake support bracket 20, two semi-enclosures one of which supports the elements of the stator and the other those of the rotor.

Claims: A driving wheel unit (1), suitable for an electric traction vehicle, of the type comprising a stub axle (2) joined to a wheel suspension (7) of the vehicle; a wheel hub (3) mounted idle on the stub axle (2) for receiving a vehicle wheel (14), the wheel (14) being mountable angularly rigid with said hub (3) for rotating therewith; and an electric motor (6) comprising a stator (4) supported in a fixed manner by said stub axle (2) and comprising at least one coil (29) connectable with a source of electric power, and a rotor (5) connected angularly with said hub (3) for rotating therewith; said driving wheel unit (1) further comprising: a first enclosing element (25) for the electric motor, which first element (25) is fixed angularly rigid with said hub (3) for rotation therewith and peripherally projects from the hub (3) in a radial direction, at least one permanent magnet (26) being supported peripherally by said first enclosing element (25) in such a manner as to define thereby said rotor (5); characterized in that said driving wheel unit (1) further comprises a second enclosing element (28) for the electric motor, mounted fixed on the stub axle (2) coaxial with and facing to said first enclosing element (25), said second enclosing element (28) supporting peripherally said at least one coil (29) so as to define thereby said stator (4); said first enclosing element extenting outwards from said hub (3), and said first and second enclosing elements (25,28) being both cup-shaped and positioned with their concavities facing each other; said at least one coil (29) being supported by said second enclosing element (28) inside the concavity thereof. A driving wheel unit (1) according to Claim 1, wherein each of said cup-shaped enclosing elements (25,28) has a respective radially external front peripheral edge (31,32); said edges (31,32) cooperate with each other to define, between said first and second enclosing elements (25,28), a labyrinth seal. A driving wheel unit (1) according to claim 2, characterised in that said first enclosing element (25) comprises a semi-toroidal element (33) of pressed sheet metal joined integrally to said wheel hub (3), on a brake drum (18) thereof, and an annular element (34) supporting said permanent magnet (26) and positioned inside the semi-toroidal element (33), with a portion thereof (35) of smaller diameter partially projecting from it in an axial direction, joined to a lateral wall (36) radially external to the semi-toroidal element (33); one end of said lateral wall (36) of the latter, being provided with a rim 40) and said projecting portion of smaller diameter (35) of said annular element (34) being separated from the rest of the element by a annular channel (41) defining said peripheral front edge (31) of said first enclosing element (25). A driving wheel unit (1) according to claim 3, characterised in that said second enclosing element (28) is, in radial section, substantially J-shaped in a position parallel with the wheel axle, and is obtained as part, and on the external periphery, of a brake support bracket (20) integral with the stub axle (2); said peripheral front edge (32) of the second enclosing element (28) being in radial section substantially Z-shaped and being positioned radially facing the exterior of said rim (40) of the edge of the lateral wall (36) of said semi-toroidal element (33) and said projecting portion of smaller diameter (35) of said annular element (34). A driving wheel unit (1) suitable for an electric traction vehicle, of the type comprising a wheel hub (3) means of braking (18,20,21,22), and an electric motor (6) comprising in turn a stator (4) supporting respective coils (29) of the electric motor (6), and a rotor (5) supporting respective permanent magnets (26) of the electric motor (6); characterized in that the means of braking include a brake drum (18) and means (20,21,22) capable of cooperating with the brake drum (18); and in that said stator (4) directly supports said means (20,21,22) for cooperating with the brake drum (18), which means are mounted rigid with the strator; said hub (3) being comprised of the rotor (5) of the electric motor (6), said rotor (5) being obtained as an integral part of the brake drum (18), which is in turn provided integral in one piece with the vehicle hub (3).

Inventors: GANDIGLIO ROMOLO, GANDIGLIO, ROMOLO
Applicants: FIAT AUTO SPA, FIAT AUTO S.P.A.
Application year: 1991
Main classification: B60K7
IPC codes: B60K7