EP0729664A1

EP0729664A1 - Electric motor-wheel with a rotor having a housing enabling an efficient exchange of heat

Info

Publication number: EP0729664A1
Application number: EP94900693A
Authority: EP
Inventors: Pierre Couture
Original assignee: Hydro Quebec
Current assignee: Hydro Quebec
Priority date: 1993-12-06
Filing date: 1993-12-06
Publication date: 1996-09-04
Also published as: NO954981D0; WO1995016300A1; NZ258088A; NO954981L; AU5558494A; FI955760A; BR9307853A; FI955760A0; KR960702693A; JPH09506236A

Abstract

An electric motor-wheel including a hollow shaft capable of receiving leads from outside the motor-wheel, a stator coaxial with and fastened to the shaft, and a rotor coaxial with and rotatable about the stator. The rotor includes a housing with a cylindrical wall having an inner surface provided with a magnetic assembly arranged around the stator and separated therefrom by an air gap, and the housing includes an inner wall on one side of the cylindrical wall, and an outer wall on the other side of the cylindrical wall. The shaft extends through a central portion of the inner wall, and the outer housing wall includes alternately convex and concave sections extending in the circumferential direction thereof so that during rotation of the rotor, air is circulated within said housing by the convex sections, and along outer portions of the concave sections to enable an efficient exchange of heat through the outer wall.

Description

ELECTRIC WHEEL MOTOR HAVING A DND ROTOR OF A HOUSING ALLOWING AN EFFICIENT EXCHANGE OF HEAT

The present invention relates to an electric wheel motor having a rotor provided with a housing allowing efficient heat exchange.

PRIOR ART:

In US Patent No. 4,913,258 to Hiroshi SAKURAI et al., Issued April 3, 1990, there is described a wheel motor having an outer rotor, comprising a joint, a hub engaged coaxially with the joint, a wheel disc rotatably attached to the periphery of the hub, a wheel attached to the periphery of the wheel disc, a rotor mounted on an outer side of the wheel disc, and a stator mounted coaxially with the rotor and separate therefrom by a small air gap, and mounted on the hub. One of the drawbacks with this wheel motor having an external rotor, resides in the fact that a strong current must be injected into the supply wiring which feeds the winding of the core of the armature in order to obtain a powerful wheel motor having a high torque, even if the speed is zero. With this type of external rotor wheel motor, a converter must be provided. This converter is mounted inside the vehicle and can be very bulky. Such high currents flowing in the power _of pro uisent heat lines representing a loss of energy. Furthermore, the supply lines can be passed _b LEMENT heavy. Since the converter is not mounted inside the motor housing, no means have not been provided for efficient heat exchange through the rotor housing.

In US Patent No. 754,802 to Ferdinand PORSCHE et al., Issued March 15, 1904, a combination is described which includes an axle, a wheel, the hollow bearing of the wheel, the end of the axle which extends into to overcome it, and a central connection between the axis and the offset which has its axial projection disposed squarely against the plane of the wheel. Again, to obtain a powerful wheel motor, the current supplied to the brushes, which comes from outside the wheel motor, must be a high current. This high current must be supplied by cables or conductors having a large diameter to reduce energy losses. Since the converter has not been mounted inside the motor housing, no provision has been made for efficient heat exchange through the rotor housing.

In US Patent No. 2,348,053 to JE BOWKER, issued May 2, 1944, improvements to a vehicle with electric motors are described which include a plurality of wheels mounted to be driven, a dynamo motor forming an integral part of each of the wheels, and electrical circuit connections arranged between banks of switches, dynamo-motors and accumulators to control the operation of dynamo¬ motors operating like motors according to the position of a selection switch. Again, the armature windings will have to be supplied with a high current in order to obtain a powerful motor, such high currents will require cables of large diameter to bring the energy from the accumulators of the vehicle to the windings of the frame. Such large diameter cables or conductors are rigid and bulky.

The following US patents describe different wheel motors 638,643; 643,854; 2,506,146; 2,514,460; 2,581,551; 2,608,598; 3,566,165; 3,704,759; 3,792,742; 3,812,928; 3,892,300; 3,897,843; 4,021,690; 4,346,777; 4,389,586; 1,709,255; 2,335,398; and 3,548,965. None of the above-mentioned patents show the means necessary to allow efficient heat exchange through the rotor housing of a wheel motor.

One of the objectives of the present invention is to provide a wheel motor which is provided with means for cooling said wheel motor when the latter is in operation.

SUMMARY OF THE INVENTION

The present invention relates to an electric wheel motor comprising:

- A hollow shaft having one end provided with a first opening, and a second end provided with a second opening, said first opening being capable of receiving conductors from outside of said wheel motor; a stator coaxial with said shaft and fixed to said shaft, said stator being provided with windings, said stator comprising a central part fixed to said shaft, a support provided with openings and extending radially from said central part, and a part peripheral and circular pole, on which said coils are wound, said pole piece being fixed to peripheral ends of said support; and

a rotor coaxial with said stator and mounted so as to be able to rotate around said stator, said rotor comprising a housing having a cylindrical wall having an internal surface provided with a magnetic means surrounding said stator and separated from said stator by an air gap, said housing comprising an inner wall disposed on one side of said cylindrical wall, and an outer wall disposed on the other side of said cylindrical wall, said shaft extending through a central portion of said inner wall, said outer wall of said housing comprising convex and concave sections which are arranged alternately along a circumferential direction of said outer wall, such so that when said rotor rotates, air circulation is produced inside said housing by said convex sections and air circulation is produced along external parts of said concave sections so as to allow efficient heat exchange at through said outer wall.

BRIEF DESCRIPTION OF THE DRAWINGS

Figure 1 is a side view partially in section of an embodiment of the present electric wheel motor, in combination with a rim, a tire and an articulated connecting rod;

Figure 2 is a front view, partially in section of the rotor and the stator of the electric wheel motor shown in Figure 1, including details of embodiment of the central part;

Figure 3 is an enlarged view of part of Figure 1; Figure 4 is a sectional view along line 4-

4 of Figure 3;

Figure 5 is a front view of part of the electric wheel motor shown in Figure 1;

Figure 6 is an enlarged view of part of Figure 1;

Figure 7 is a sectional view along line 7-7 of Figure 5;

Figure 8 is a front view of the rim with the tire shown in Figure 1; Figure 9 is a sectional view along line 9-9 of Figure 8;

Figure 10 is an enlarged view of part of Figure 9; Figure 11 is an enlarged view of part of Figure 9;

Figure 12 is an enlarged view of part of Figure 1;

Figure 13 is a rear view of the elements which are shown in Figure 12;

Figure 14 is a rear view of the articulated connecting rod shown in Figure 1, partially in section;

Figure 15 is a rear view of an element of Figure 1 on which the articulated rod is connected; Figure 16 is a top view partially in section of the rear part of the electric wheel motor shown in Figure 1;

Figure 17 is a rear view of the articulated connecting rod in combination with a disc brake; Figure 18 is a schematic block diagram of an electrical conversion system according to the present invention;

Figure 19 is a side view partially in section of another embodiment of the electric wheel motor according to the present invention;

Figure 20 is a side view partially in section of another embodiment of the electric wheel motor according to the present invention;

Figure 21 is a schematic block diagram of another embodiment of the electrical conversion means according to the present invention;

Figure 22 is a side view partially in section of another embodiment of the electric wheel motor according to the present invention; Figure 23 is a partially sectioned front view of the stator and rotor of the electric wheel motor shown in Figure 22;

Figure 24 is another side view, partially in section of the embodiment of the electric wheel motor shown in Figure 1; and

Figure 25 is an enlarged view of part of Figure 1.

DESCRIPTION DETATT.T.fti ^g nES DRAWINGS

In the various figures of the drawings, the corresponding elements are identified by the same numerical indices. if reference is now made to FIGS. 1 and 2, there is respectively shown a side view partially in section of an embodiment of the electric wheel motor, in combination with a rim 28, a tire 32 and an articulated connecting rod 50; and a partially sectional front view of the rotor 10 and the stator 6 of the electric wheel motor shown in FIG. 1. The electric wheel motor comprises a hollow shaft 2 having a first opening at one of its ends and a second opening. The first opening receives conductors 4 from outside the wheel motor. The stator 6 is coaxial with the shaft 2 and fixed to it, the stator 6 being provided with hollow parts 11 and coils 8.

In Figure 2, only a few winding sections are indicated by No. 8, but it should be understood that there are windings all around the stator 6. The stator 6 is fixed to the shaft 2 but can be removed from this when the wheel motor is not in operation.

The rotor 10 is coaxial with the stator 6 and is mounted so that it can rotate around the stator 6. The stator 6 comprises openings forming the hollow parts 11 between arms 13 to reduce its weight. The wheel motor is also equipped with a conversion system to convert an input electrical current into an alternating and variable electrical current. The conversion system 12 comprises a microprocessor unit 44, a DC / AC converter having power electronics 14, mounted inside the hollow parts 11, input terminals 15 for receiving the input electrical current brought by means of conductors 4 and output terminals 16 to generate alternating and variable electric current. It should be understood that the conversion system can be reversible, so that the electric motor can be used as a generator. The frequency of the alternating and variable electric current is representative of a desired speed of rotation of the rotor 10, the phase angle of the alternating and variable electric current determines whether the wheel motor will operate as a motor or as a generator and the amplitude alternating and variable current is representative of the desired torque. The user of the present wheel motor can use relatively small diameter conductors to bring electrical power inside the wheel motor if such power is produced from a high voltage because the power electronics 14 is inside the wheel motor. Such power electronics 14 will convert the high voltage and low current input signal into a high current signal to supply the windings 8 of the stator with alternating and variable current. Since the power electronics 14 are already inside the wheel motor, large diameter conductors required to bring the electric current from the conversion system 12 to the windings 8 of the stator will be relatively short. Of course, the power electronics 14 includes capacitors, transistors, diodes and other components such as known to those skilled in the art.

To reduce the weight or diameter of the electrical conductors, a high supply voltage can be used according to the following relation: P = IV, where P is the power, I is the current and V is the voltage. If V increases, then I is reduced. At low speed, the power is low, this implies that the current which feeds the converter is also low since the voltage is constant. However, if a high torque is required, the current which feeds the stator windings must also be high. The mounting of the power electronics of the converter inside the housing makes it possible to choose electrical supply conductors relative to a desired motor power while allowing high torque at low speed. In addition, the converter allows the impedance of the motor to be adapted to that of the high voltage power source.

The stator 6 comprises a central part attached to the shaft 2, arms 13 extending radically from the central part, and a circular and peripheral pole piece including metal blades 27 on which coils 8 are wound. The pole piece is fixed to the peripheral ends of the arms 13. The rotor 10 comprises a housing having a cylindrical wall 17 having an internal surface provided with a magnetic means 26 surrounding the stator and separated from the latter by an air gap. Since the air gap is relatively small, it cannot be seen in FIGS. 1 and 2, but its location is indicated in FIG. 25 by means of R _^ The housing comprises an internal wall 18 arranged on one side of the cylindrical wall 17, and another wall 20 disposed on the other side of the cylindrical wall 17. The shaft 2 extends through a central part of the inner wall 18.

The housing which is part of the rotor 10 tightly encloses the shaft 2, the stator 6 and the conversion system 12. A tight seal 123 is provided. The wheel motor comprises a first ball bearing 22 connected to the internal wall 18, and a second ball bearing 24 connected to the external wall 20. The ball bearings 22 and 24 are respectively mounted on either side of the 'shaft 2 so that the rotor 10 can rotate relative to the stator 6 by means of ball bearings 22 and 24. A threaded bolt 23 is provided to fix the stator 6 relative to the shaft 2. A ring d stop 21 is also planned. A compression ring 127 is provided for fixing the ball bearing 22. The stator 6 needs at least two arms arranged between the openings to support the pole piece of the stator 6. Also, the support can comprise three equally spaced arms, extending radially to the peripheral ends of the stator 6. In FIG. 2, it can be seen that the stator 6 comprises four arms 13 also spaced apart. In the embodiment shown in these Figures 1 and 2, the magnetic means of the rotor 6 comprises a series of permanent magnets 26. In Figure 2, only a few magnets are identified by the number 26, but it should be understood that these magnets 26 are provided all around the stator 6. The stator 6 is made in part of a light weight material which can conduct heat. Preferably, this material is an aluminum alloy. The wheel motor further comprises a rim 28 fixed around an external surface of the housing, and a strip 30 made of an elastomer and mounted between the rim 28 and the housing. The rim 28 is adapted to receive the tire 32. The rim 28 is flat-bottomed. The magnets 26 are preferably made of neodymium, iron and boron. The strip 30 prevents penetration of water or dust between the housing and the rim 28 to prevent the wheel from unbalancing.

The peripheral ends of the arms 13 are fixed to the pole piece of the stator 6 by means of a circular member 34 which is an integral part of the peripheral ends of the arms 13. The circular member 34 has its external surface provided with notches 36. The piece pole of the stator 6 has an internal surface provided with protruding tongues 37 of complementary shape which are able to cooperate with the notches 36 to fix the pole piece of the stator 6 on the circular member 34. The circular member 34 has an internal surface provided with parts protrusions 38, thus an efficient heat exchange can be obtained by means of the protruding parts 38 when air circulation is produced inside the housing. Only a few projecting parts are indicated by the number 38 so as not to overload Figure 2. The support of the stator 6 and the circular member 34 are made of an aluminum alloy while the pole piece of the stator 6 is made of steel. It should be noted that the ends of the cross formed by the arms 13 of the stator 6 are aligned with the notches 36 for mechanical reasons. Thus, the projecting parts 38 which are arranged along the circular member 34 are, relative to their longitudinal dimension, preferably out of phase with respect to the motor shaft of the wheel, along the circumferential direction of the member 34 so to reinforce it mechanically.

Referring now to Figures 1, 2 and 25, the air gap is positioned at a predetermined distance R ^ from the central axis 3 of the shaft 2. The rim 28 has a surface 29 for receiving the tire 32 which is positioned at a predetermined distance R ₂ from the central axis 3 of the shaft 2. R _x / R ₂ must be substantially between 0.65 and 0.91 to obtain an efficient wheel motor. The higher the ratio Ri / Rj ,, the better the efficiency of the wheel motor. But, as there are physical limitations, the wheel motor shown in Figures 1, 2 and 25 has a substantially R _ι / R ₂ ratio of 0.91. For an engine with a radial air gap, the torque

T is proportional to L • R ^ • I _B , where L is the width of the pole. Ri is the radius of the air gap and I _B is the winding current. For the design of this wheel-motor, the width L of the pole piece has been maximized. By having several poles, the weight of the pole piece of the magnetic circuit can be reduced, thereby reducing the weight of the rotor and the moment of inertia of the rotor, thereby allowing the presence of a cavity for mounting a means of braking. The present wheel motor increases the torque T by having a large pole piece and by having a high ratio of R _x / R ₂ where the theoretical limit which cannot be reached is 1. The present motor wheel also provides high power because P = T • ω which is proportional to L • Ri ² • I • ω, where ω is the angular frequency of the rotor. The present wheel motor includes a cross-shaped stator to reduce the weight of the wheel motor, to allow cooling of the windings, and to allow space in the hollow parts 11 which will provide space for mounting the conversion system. The cross-shaped stator supports the conversion system and is used as a cooling element.

The wheel motor preferably has thirty-two poles. This wheel motor can operate with sixteen poles but it is preferable to have a high number of poles to reduce the weight of the wheel motor. The conductors 4 are preferably made of a coaxial cable including an optical fiber. This coaxial cable prevents the emission of radiation.

In the following description, the same reference numbers refer to similar elements through the set of drawings.

Referring now to Figures 1, 2 and 18, the conversion system comprises a DC / AC converter having an input 40 for receiving direct current from the input terminals 15, and three outputs 42 for generating three AC phases in the output terminals 16. AC currents are not necessarily three phase currents, polyphase currents can also be used. The conversion system also includes a microprocessor unit 44 connected to the arms 41a, 41b, 41c of the converter to control its operation. The microprocessor unit can be located outside of the wheel motor. The conversion system shown in Figure 18 can be used when the rotor does not have to be supplied with electric current. As can be seen in Figure 2, the stator 6 is in the shape of a cross and has four arms 13. The converter comprises three arms 41a, 41b and 41c which respectively generate the three alternating phase currents, the arms 41a, 41b and 41c being fixed respectively to three of the four arms 13 of the stator 6. These three arms 41a, 41b and 41c form part of the power electronics 14 shown in FIG. 2.

The power electronics shown in Figure 2 includes the arms 41a, 41b, 41c of the converter shown in Figure 18 but also includes the capacitor 43 shown in Figure 18. In this Figure 18, only one capacitor 43 is shown to simplify this figure 18, but in the embodiment shown in Figure 2, the capacitor 43 is distributed in three capacitors respectively disposed on three of the four arms 13 shown in Figure 2. It is not essential that the control amplifiers 91 are inside the housing. Each of the arms 41a, 41b, 41c of the converter includes a switching section and a control section which is formed by the control amplifiers ₉ 1. The microprocessor unit 44 is fixed on the fourth of the arms 13. It should be noted that the microprocessor unit 44 can also be mounted outside of the wheel motor because it does not generate a high current. The wheel motor further comprises two circular distribution and supply buses 48 connected to the arm 41a, 41b, 41c of the converter and to the microprocessor unit 44, thus the direct current brought by the conductors can be distributed to the arm 41a , 41b, 41c of the converter, and to the microprocessor unit 44 by means of the bus 48. Please note that the converter can be a direct current / alternating current converter where a high voltage alternating electric current is brought by the conductors. Referring now to Figures 1, 12, 13, 14 and 15, it can be seen that the shaft 2 is provided with a connection means at its first end by which the wheel motor can be connected to a member of support. This support member is an articulated connecting rod 50. This connection means is made of an annular member 52 having an external edge regularly provided with notches 54 alternating with protruding parts 56 so that the annular member 52 can be engaged and locked with a complementary part 53 of the articulated rod 50.

The protrusions of the outer border have a width which varies in the circumferential direction. The complementary part of the articulated connecting rod 50 also has an annular section 58 having a sufficient diameter so that the annular section 58 can be slid over the outer edge of the shaft 2. The annular section 58 has notches 60 and protruding parts 62 of complementary shape which are adapted to cooperate with projecting parts 56 and the corresponding notches 54 of the outer edge of the annular member 52. The protrusions 62 of the annular section 58 have a width which varies in the circumferential direction so that the annular section 58 can slide on the outer edge and rotate relative to said edge external to be stuck in an assembled position. Also, a key 66 is provided, it has tongues 68 which can be inserted into cavities 55 which are produced when the annular section 58 is turned relative to the outer edge of the shaft 2 to lock the shaft 2 relative to to the articulated rod 50. Holes 63 are provided for fixing a disc brake (shown in Figures 16 and 17).

The articulated connecting rod 50 is provided with an elongated internal slot 70 having a first end adjacent to the annular section 58 and a second end remote from said annular section 58, thus the conductors 4 can be brought to the shaft 2 along said elongated slot 70. The key 66 has an elongated section 72 provided with an elongated internal cavity, the elongated section 72 being able to cooperate with the internal slot 70 of the connecting rod 50 along part of its length to protect the conductors 4. The part of the slot 70 which is not protected by the elongated section 72, is provided with a protective element (not shown) to cover the conductors 4. It should be noted that the lower border of the tongues 68 is slightly biased so as to facilitate the penetration and locking of the tongues 68 in the cavities 55. The holes 65 are provided for fixing the key 66 on the shaft 2. The threaded holes 67 are provided for facilitating th removal of the key 66. Referring now more specifically to FIG. 15, the first end of the shaft has an internal part provided with a cavity 74 having sharp edges 76 taking the form of square corners so that that said cavity can receive a key (not shown in the Figures) to turn the shaft 2.

Referring now more specifically to Figures 1, 18 and 25, a measuring means for measuring the speed of rotation and the position of the rotor 10 relative to the stator 6 is provided, this means comprises an optical fiber 80 having a first end connected to the microprocessor unit 44, and a second end positioned to be adjacent to the rotor 10. The measuring means also comprises a circular light reflector 82 mounted on the rotor 10 so that when said rotor 10 rotates, the reflector passes in front of the second end of the fiber 80, thus the speed of rotation and the position of the rotor 10 relative to the stator 6 can be calculated by means of the microprocessor unit 44. It should be noted that the circular reflector 82 is made of a series of reflectors having different reflection characteristics so that the position of the rotor 10 relative to the stator 6 can be determined at any time s. The optical fiber 80 consists of at least one fiber. Referring now more specifically to Figure 18, the fiber 80 and the reflector 82 form an encoder which is connected to a position decoder 83 of the microprocessor unit 44. The position decoder 83 comprises an optical coupler, a light source, photo-detector and other electronic components. The microprocessor unit 44 also comprises a controller 85 having an input 87 for detecting the currents in the windings 8 of the stator and an output 89 for triggering the arms 41a, 41b, 41c of the converter by means of the control amplifiers 91. The microprocessor unit 44 is also provided with a communication interface 93 for connecting it to another intelligent device. The control amplifiers need not be inside the housing. Referring now to Figures 1, 16 and 17, it can be seen that the inner wall 18 of the housing has an outer surface of concave shape to produce, when the rotor 10 rotates, an air flow towards the periphery of the wall internal 18. The external surface is provided with a series of elongated and parallel blades 90 extending in the direction of the shaft 2. The blades have their free ends which define a space 92 in which part of a means of braking 94 can be mounted, thus an efficient heat exchange can be obtained through the internal wall 18 and the braking means 94 can be cooled by the air circulation produced along the internal wall 18.

Referring now more specifically to Figures 16 and 17, it can be seen that the braking means 94 is a disc brake having a disc 96 bolted to the inner wall 18. As is known in the art, this disc braking comprises a caliper 98 able to cooperate with the disc 96. Shown diagrammatically, one can see the ball joint articulation 100 and the steering arm 102 of the steering system. Each of the blades 90 is provided with threaded cavities 104 serving to mount a drum brake in place of the disc brake 94. Bolts 95 are provided for fixing the disc brake on the internal wall 18. We can see fasteners 106 for fix the disc brake 94 on the connecting rod 50. We can also see bolts 108 to support the caliper, and pistons 110 able to cooperate with bearings 99. From Figures 1, 16 and 17 we can see that the ball joint of the steering system is fairly close to the shaft 2 so that the angle alpha between the axis of rotation of the wheel motor and the axis determined by the connecting rod 50 and the joint d 'ball joint 100 is advantageous. It should be noted that the geometry of the internal wall 18 allows this advantageous position of the ball joint joint 100 relative to the wheel motor.

Referring now to Figures 1, 5, 6 and 7, the outer wall of the housing includes convex and concave sections 112 and 114 which alternate along its circumferential direction, so that, when the rotor turns, circulation air is produced inside the housing by means of the convex section 112 as indicated by the arrows 116, and an air circulation is produced along the external parts of the concave section 114 as indicated by arrows 118, thus an efficient heat exchange can be obtained through the external wall. Note that Figure 6 is a side view partially in section of Figure 5. Openings with plug 113 are provided to allow access to the interior of the housing. Bolts 115 are provided to fix the rim 28.

Referring now to Figures 1, 3 and 4, the wheel motor further includes means for drying including an air hose 120 having one end disposed inside the housing, a chamber 122 disposed at the outer end of the pipe 120 and a desiccant material (not shown) disposed inside the chamber 122, so when the rotor 10 rotates, air circulation is produced inside the pipe 120 and through the chamber 122 to dry the air inside the housing. The chamber 122 is annular, elongated and disposed inside the hollow shaft 2. The chamber 122 is open at each of its ends. The opening of the shaft which is adjacent to the articulated rod 150 is airtight. It can be seen in Figure 1 that one end of the pipe 120 is adjacent to the peripheral part of the stator 6, the pipe 120 is mounted between the external wall 20 and the stator 6 until it reaches the opening of the shaft 2, then it is disposed along the chamber 122 so that its other end 124 is placed at one end of the chamber as shown in Figures 3 and 4. The end 124 of the pipe 120 is arranged between the airtight end of the hollow shaft and the chamber 122 so that the air flowing through the pipe 120 must go through the chamber where it is dried.

The conductors 4 have in their central part an optical fiber 126, a first electrical conductor 128 and a second electrical conductor 130 separated from the first conductor by an insulating material 132. The conductors 4 are protected by an external sheath 134.

Referring now to Figures 8, 9, 10 and 11, one can see a tire 32 which is fixed to the rim 28 permanently when assembling the wheel motor. The wheel motor is provided with a flat-bottom rim 28, a first side flange 142 which can be welded to the rim 28, and a second side flange 144, which is fixed to the rim 28 at the by means of bolts 146 and an L-shaped member 148 welded to the rim 28. The relationship between the rim 28, one of the bolts 146 and the L-shaped member 148, can be seen more easily in Figure 10. The tire 32 can be inflated by means of a valve 150 which allows access to the interior of the tire 32. This valve 150 can be seen in more detail in FIG. 11.

Since the rim 28 is flat-bottomed, the tire 32 cannot be removed from the rim 28. With such a wheel motor, when the tire is worn, the rim 28 and the tire must be replaced.

Referring now to Figure 19, one can see a wheel motor similar to that shown in Figure 1, in which the means for drying is different. This means for drying comprises an air hose 120 having a end disposed inside the housing, and a chamber 121 provided with an inflatable balloon 123 mounted in a housing 127, disposed at the other end 125 of the pipe 120. A desiccant material is disposed inside the chamber 121, thus, when the temperature or the atmospheric pressure change, an air circulation is produced inside the pipe 120 and through the chamber 121 to dry the inside of the case. As can be seen, the chamber 121 is arranged outside the wheel motor. The opening of the shaft 2 which is adjacent to the articulated connecting rod 50 is airtight. Pipe 120 is used as an outlet and as an inlet for chamber 121.

Referring now to Figure 20, we can see an electric wheel motor in which the rotor comprises magnetic means including a pole piece made of metal blades on which is wound a coil 9, the stator is provided with brushes 111 which are connected to an output of the conversion system 12. The rotor is provided with a conductive contact surface arranged so as to be able to cooperate with the brushes 111. The contact surface is connected to the winding 9 of the rotor 10.

Referring now more specifically to Figures 20 and 21, the conversion system 12 comprises a DC / AC converter having four arms 41a, 41b, 41c and 41d, an input for receiving direct current from the terminals. input 40 and four outputs 45 and 43 to generate a direct current for the winding 9 of the rotor 10 and three alternating phase currents for the windings 8 of the stator 6. The conversion system also includes a microprocessor unit 44 connected to the arms 41a, 41b, 41c and 41d, to control its operation. The winding 9 and the blades of the rotor 10 on which the winding 9 is wound can be replaced by a conductive ring. Referring now to Figures 22 and 23, one can see a wheel motor having an induction rotor. The rotor comprises a magnetic means including a pole piece made of metal blades on which the winding 9 is wound, thus an electric current can be induced in the winding 9 of the rotor by means of an electromagnetic field produced by the electric current injected into the windings 8 of the stator 6.

The reference number 8 in Figure 23 represents all the windings which are arranged around the stator even if only part of the windings is indicated. Also, the reference number 9, in Figure 23, represents the winding which is arranged all around the rotor. The conversion system 12 comprises a direct current / alternating current converter having three arms 41a, 41b, 41c, an input for receiving direct current from the input terminals 15 which are connected to the bus 48 and three outputs which generate three currents of phase alternating in the output terminals 16. Also, the conversion system 12 comprises a microprocessor unit 44 connected to the converter to control its operation.

As can be seen in Figure 23, the stator is cross-shaped and has four arms 13. The converter comprises power electronics which is made in part from the three arms of the converter which respectively generate the three alternating phase currents. The converter arms are fixed respectively to three of the four arms 13. The wheel motor further comprises two circular supply and distribution buses connected to the power electronics 14 and to the microprocessor unit 44.

The air gap is positioned at a predetermined distance R _x from the central axis 3 of the shaft 2. The rim 28 has a surface for receiving the tire 32 which is positioned at a predetermined distance R ₂ from the central axis 3 of the shaft 2. The ratio Rχ / R ₂ is of the order of 0.65 to 0.80 in the case where the rotor is fitted with a winding. The higher the ratio, the better the efficiency of the wheel-motor. In the case shown in Figures 22 and 23, the ratio is around 0.80.

If we now refer to Figure 24, we can see that the stator 6 is cylindrical and provided with longitudinal and parallel slots 200 to receive the windings 8 of the stator 6. So as not to overload Figure 24, only a few slots have have been identified by the number 200. The slots are curved with respect to the longitudinal axis 3 of the shaft 2 so that each of the slots 200 has its lower end which is substantially aligned with the upper end of the adjacent slot so as to produce a regular torque when the wheel motor is in operation.

Although the present invention has been described above as preferred embodiments, such preferred embodiments can, of course, be modified at will while remaining within the scope defined by the appended claims without changing or altering the nature or the scope of the present invention.

Claims

1. An electric wheel motor comprising: - a hollow shaft having one end provided with a first opening, and a second end provided with a second opening, said first opening being able to receive conductors from outside of said wheel motor;

a stator coaxial with said shaft and fixed to said shaft, said stator being provided with windings, said stator comprising a central part fixed to said shaft, a support provided with openings and extending radially from said central part, and a part peripheral and circular pole, on which said coils are wound, said pole piece being fixed to peripheral ends of said support; and

a rotor coaxial with said stator and mounted so as to be able to rotate around said stator, said rotor comprising a housing having a cylindrical wall having an internal surface provided with a magnetic means surrounding said stator and separated from said stator by an air gap, said housing comprising an inner wall disposed on one side of said cylindrical wall, and an outer wall disposed on the other side of said cylindrical wall, said shaft extending through a central portion of said inner wall, said outer wall of said housing comprising sections convex and concave which are arranged alternately along a circumferential direction of said outer wall, such that when said rotor rotates, an air circulation is produced inside said housing by said convex sections and a circulation d air is produced along external parts of said concave sections so as to allow exchange effective heat through said outer wall.

2. Wheel motor according to claim 1, comprising a conversion means for converting an electrical input current into an alternating and variable electrical current, said conversion means comprising power electronics, input terminals for receiving said current electrical input and output terminals for generating said alternating and variable electrical current to the stator windings.

The wheel motor according to claim 2, wherein: said peripheral pole piece is made of metal blades;

said stator is provided with a hollow part; and said power electronics are fixed in said hollow part.

4. A wheel motor according to claim 2, in which said casing tightly encloses said shaft, said stator and said conversion means.

5. Wheel motor according to claim 2, comprising a first ball bearing connected to said internal wall, and a second ball bearing connected to said external wall, said ball bearings being mounted respectively on each side of said shaft so that the rotor can rotate relative to said stator by means of ball bearings.

6. Wheel motor according to claim 2, wherein said support comprises at least two arms between said openings. 5/16300

24

7. A wheel motor according to claim 6, wherein said support comprises at least three equally spaced arms extending radially to the peripheral ends of said support.

8. A wheel motor according to claim 7, in which said equally spaced arms comprise four equally spaced arms.

9. A wheel motor according to claim 2, wherein said rotor comprises magnetic means provided with a series of permanent magnets.

10. A wheel motor according to claim 2, wherein said stator comprises a light material capable of conducting heat.

11. Wheel motor according to claim 10, wherein said material is an aluminum alloy.

12. A wheel motor according to claim 1, further comprising a rim fixed around an external surface of said housing, and a strip made of an elastomer, said strip being mounted between said rim and said housing, said rim being adapted for receive a tire.

13. A wheel motor according to claim 12, wherein said rim is flat.

14. A wheel motor according to claim 9, in which said conversion means comprises:

- a direct current / alternating current converter having an input for receiving a direct current from said input terminals, and three outputs for generating three phase alternating currents in said output terminals; and

- a microprocessor unit connected to said converter to control its operation.

15. A wheel motor according to claim 14, in which:

- Said stator is cross-shaped and has four arms;

- Said converter is made of three conversion units which respectively generate said three alternating phase currents, said units being fixed respectively on three of said four arms; and

- said microprocessor unit is fixed to the fourth of said arms; said wheel motor further comprising two circular power distribution buses connected to said conversion and microprocessor units, thus, in operation, said direct current is distributed to said conversion and microprocessor units by means of said buses.

16. A wheel motor according to claim 2, wherein said peripheral ends of said support are fixed on said pole piece of said stator by means of a circular member which is integral with said peripheral ends, said circular member has an external surface provided with notches, said circular pole piece of said stator has an internal surface provided with protruding tongues capable of cooperating with said notches to fix said pole piece of said stator on said circular member, said circular member having an internal surface provided with projecting parts, thus, in operation, an efficient heat exchange is obtained by means of said projecting parts when air circulation is produced inside said housing.

17. A wheel motor according to claim 1, in which said internal wall of said housing has an external surface of concave shape to produce, when said rotor rotates, an air flow towards the periphery of said internal wall, said external surface being provided of a series of parallel and elongated blades extending in the direction of said shaft, said blades having their free surface defining a space in which a braking means can be mounted, thus an efficient heat exchange can be obtained through said internal wall , and said braking means can be cooled by the air circulation produced along the internal wall.

18. A wheel motor according to claim 2, further comprising means for drying including an air hose having one end disposed inside said housing, a chamber disposed at the other end of said hose, and a desiccant material disposed inside said chamber, thus, when said rotor rotates, air circulation is produced inside said pipe and through said chamber to dry the inside of said housing.

19. A wheel motor according to claim 18, in which:

- Said chamber is an elongated annular chamber disposed inside said hollow shaft, said chamber being open at its two ends;

- Said first opening of said shaft is sealed; and

- Said other end of said pipe is disposed between said first opening which is sealed and said chamber so that the air which leaves said other end of the pipe circulates in said chamber.

20. A wheel motor according to claim 18, in which:

said chamber is arranged outside said wheel motor, and

- Said first opening of said shaft is sealed; thus said pipe is used as an outlet and as an inlet of said chamber.