In-wheel motor wheel and wheeled vehicle provided with such a wheel

Abstract

The invention relates to an in-wheel motor wheel (3) comprising a hollow body (4) having a hub (5) defining an axis of rotation (XX') of the wheel, wherein the hollow body (4) defines a cavity (6) housing an electric motor (7) with a rotor (8) capable of rotating about a motor axis (YY') and a transmission system (9) for transmitting the rotational movement of the rotor (8) to the body (4) in order to rotate the body (4) about the axis of rotation (XX') of the wheel (3), wherein the motor axis (YY'), which does not intersect the axis of rotation (XX'), extends in a plane perpendicular to the axis of rotation (XX') of the wheel (3), and wherein the rotating body (4) comprises a circular toothing fixed in rotation with the body (4), the toothing having its centre arranged on the axis of rotation (XX') of the wheel (3). The transmission system (9) comprises an endless screw (11) that is fixed in rotation with the rotor (8) and meshes with the toothing (10).

Description

Description Title of the invention: Electric wheel and rolling machine equipped with such a wheel

[0001] The present invention relates to an electric wheel and a rolling machine equipped with such a wheel.

[0002] It relates in particular to an electric wheel comprising a hollow body having a hub suitable for mounting on a shaft and defining an axis of rotation of the wheel, said hollow body delimiting a cavity inside which are housed an electric motor with a rotor capable of rotating around a motor shaft and a system for transmitting the rotational movement of the rotor to the body to rotate the body around the axis of rotation of the wheel, the motor shaft which does not intersect the axis of rotation extending in a plane substantially perpendicular, that is to say perpendicular to within 10°, to the axis of rotation of the wheel and the rotating body comprising teeth fixed in rotation to said body, these teeth being circular teeth with a circle whose center is located on the axis of rotation of the wheel.

[0003] Motorized electric wheels that integrate a motor inside the wheel are known. Most electric wheels have a central motor coaxial with the wheel's axis of rotation. This results in a bulky and heavy wheel due to the motor's diameter and thickness. Other electric wheels incorporate a motor whose motor shaft is not parallel to the wheel's axis of rotation. The solutions adopted for transmitting the rotor's rotational motion to the wheel body are complex and / or bulky and / or noisy and / or demanding in terms of positioning.

[0004] One aim of the invention is to propose an electric wheel of the aforementioned type whose design allows a reduction in the size of said wheel without harming its performance and its simplicity of manufacture.

[0005] To this end, the invention relates to an electric wheel comprising a hollow body having a hub defining an axis of rotation of the wheel, said hollow body delimiting a cavity inside which are housed an electric motor with a rotor capable of rotating around a motor axis and a a system for transmitting the rotational movement of the rotor to the body to rotate the body around the axis of rotation of the wheel, the drive shaft which does not intersect the axis of rotation extending in a plane substantially perpendicular to the axis of rotation of the wheel and the rotating body comprising teeth fixed in rotation to said body, these teeth being circular teeth of a circle whose center is located on the axis of rotation of the wheel, characterized in that the transmission system comprises a worm screw fixed in rotation to the rotor and meshed with the teeth.

[0006] The position of the motor shaft relative to the wheel's rotation axis, combined with a worm gear drive system, offers numerous advantages. Direct engagement of the worm gear with circular teeth in the aforementioned motor position reduces the overall size. This is achieved by combining a small motor with large-diameter circular teeth, resulting in a high reduction ratio while allowing at least partial positioning of the motor within the tooth profile. The worm gear, in conjunction with the teeth, thus provides a high reduction ratio, low noise, and a relatively large degree of spatial freedom for positioning, facilitating the mounting and operation of the wheel.

[0007] According to one embodiment of the invention, the worm gear and the drive shaft are coaxial. This results in simpler design and assembly, as well as a reduced footprint.

[0008] According to one embodiment of the invention, the worm screw extends in a plane substantially perpendicular to the axis of rotation of the wheel. By substantially perpendicular, we mean perpendicular to within ±10°.

[0009] According to one embodiment of the invention, the teeth comprise axial teeth that project from a plane perpendicular to the axis of rotation of the wheel. This results in a simplified manufacturing process for the teeth.

[0010] According to one embodiment of the invention, the body comprises two facing walls forming the sides or sails of the wheel and a peripheral wall circumferential, connecting said opposing walls to each other and forming the rim of the wheel, in that the teeth project from one of the two opposing walls towards the other of said opposing walls, in that the motor is disposed inside a virtual cylinder whose axis coincides with the axis of rotation of the wheel and whose diameter is equal to the largest diameter of the circular teeth. Preferably, the motor is disposed inside a virtual cylinder, that is to say, an imaginary or virtual cylinder, whose axis coincides with the axis of rotation of the wheel and whose diameter is equal to the smallest diameter of the circular teeth.Preferably, the axis of rotation of the worm is offset from a plane parallel to the axis of rotation of the worm and passing through the axis of rotation of the wheel by a distance less than the largest radius of the circular teeth, this distance expressed in millimeters being preferably less than or equal to half the maximum diameter of the teeth expressed in millimeters minus 30. This design allows a reduced footprint of the motor which can be entirely positioned within the maximum diameter of the teeth.

[0011] According to one embodiment of the invention, the teeth and at least part of the body are made from a single piece.

[0012] According to one embodiment of the invention, the wheel comprises a shaft, called the wheel shaft, around which the hub is mounted. This wheel shaft carries a motor support disposed within the body cavity, the motor being coupled directly or indirectly to said motor support. The fact that the motor shaft does not intersect the wheel's axis of rotation allows the use of a simple wheel shaft that does not have to go around the motor, thus making such a wheel shaft more rigid.

[0013] According to one embodiment of the invention, the motor support comprises a housing within which the worm gear is freely mounted for rotation. This worm gear is couplingable to the motor rotor. A portion of the motor, other than the rotor, is positioned in contact with a portion of the motor support, forming a stop to prevent rotation of said portion of the motor. Again, this results in ease of implementation.

[0014] According to one embodiment of the invention, the body comprises, disposed inside the body cavity and rotationally fixed to the body, at least one A circular track, centered on the wheel's axis of rotation, extends coaxially with the gear teeth. The motor support is equipped, for each track, with one or more guide elements. Each guide element, such as a bearing or a pad, is designed to make rolling or sliding contact with the track. The presence of one or more guide elements ensures proper engagement, even in the case of geometric imperfections in the components, which may be produced by molding. It should be noted that the torque transmitted by the motor generates forces in the gear teeth. These forces act in the direction of a separation between the gear teeth and the worm gear. The guide elements ensure proper engagement even under these conditions.

[0015] According to one embodiment of the invention, the motor support being for the or at least one of the tracks equipped with several guide elements, said guide elements extend on either side of a radial plane to the track passing through the gripping area by worm gear / tooth meshing.

[0016] According to one embodiment of the invention, the body comprises two facing walls forming the sides or rims of the wheel and a circumferential peripheral wall connecting said facing walls and forming the rim of the wheel. At least two circular tracks are arranged facing each other on the facing walls of said body. Preferably, the teeth are surrounded by one or at least one of the tracks. Thus, in the case of two facing tracks, the position of the tracks close to the rim allows control of the distance between the two tracks, since this distance is primarily determined by the thickness of the rim.

[0017] According to one embodiment of the invention, the motor support is mounted with clearance on the wheel shaft so that it can oscillate about an axis orthogonal to the axis of rotation of the wheel. This arrangement allows for the transmission of motion in both directions of rotation of the worm gear or the teeth.

[0018] The invention also relates to a rolling machine characterized in that it is equipped with at least one electric wheel conforming to that described above.

[0019] Preferably, the wheeled machine, which includes at least one electric wheel of the aforementioned type, is a mowing machine including at least one mowing element, such as a rotating cutting blade.

[0020] Brief description of the drawings

[0021] The invention will be better understood upon reading the following description of exemplary embodiments, with reference to the attached drawings in which:

[0022] [Fig. 1] represents an exploded perspective view of the constituent elements of an electric wheel according to the invention;

[0023] [Fig. 2] represents a perspective view of an electric wheel according to the invention in the assembled state;

[0024] [Fig. 3] represents a schematic view of an electric wheel according to the invention to illustrate the concept of an imaginary or fictitious cylinder;

[0025] [Fig. 4] represents a partial cross-sectional view of an electric wheel according to the invention;

[0026] [Fig. 5] represents a partial cross-sectional view of an electric wheel according to the invention;

[0027] [Fig. 6] represents a partial longitudinal cross-sectional view of an electric wheel according to the invention;

[0028] [Fig. 7] represents a partial view of an electric wheel according to the invention in the state electrically connected to a power supply;

[0029] [Fig. 8] represents two schematic partial cross-sectional views of an electric wheel according to the invention to illustrate the oscillation of the motor support;

[0030] [Fig. 9] represents a perspective view of the motor support of the worm gear motor and wheel shaft in exploded view of said elements;

[0031] [Fig. 10] represents, in schematic form, different examples of guiding elements;

[0032] [Fig. 11] represents a partial cross-sectional view of an electric wheel according to the invention associated with two detail views;

[0033] [Fig. 12] represents a perspective view of a rolling machine equipped with an electric wheel according to the invention;

[0034] [Fig. 13] represents, in the form of two views, one in the assembled state, the other in the unassembled state, the immobilization in rotation of a part of the motor by stop with the motor support;

[0035] [Fig. 14] represents a partial perspective view of the inside of an electric wheel according to the invention;

[0036] [Fig. 15] represents a partial exploded view of some of the elements in figure 14;

[0037] [Fig. 16] represents a partial schematic view of a worm gear associated with a triangle to illustrate the helix angle.

[0038] As mentioned above, the invention relates to an electric wheel 3 of the type shown in Figures 1 and 2. This electric wheel 3 is suitable for equipping a rolling machine 1, as illustrated in Figure 12. This rolling machine 1 is here a mowing machine which includes at least one mowing element 2 formed, for example, by a rotating blade and at least two electric drive wheels 3.

[0039] This mowing machine 1 can be an autonomous machine of the robot type, i.e., without a driver as illustrated, or a mowing machine with a driver walking behind it, such as a lawnmower, or a mowing machine with an onboard driver, such as a riding mower. Obviously, other applications of the electric wheel, which will be described later, can be considered without departing from the scope of the invention.

[0040] One or more of the electric wheels 3 suitable for equipping such a rolling machine is a drive wheel. This electric wheel 3 comprises a hollow body 4 with a hub 5 suitable for mounting on a shaft 14, called the wheel shaft. This hub 5 forms a circular recess. This hub 5 defines an axis XX' of rotation for the wheel 3. The hollow body 4 delimits a cavity 6 inside which are housed an electric motor 7 with a rotor 8 capable of rotating around a motor shaft YY' and a system 9 for transmitting the rotational motion of the rotor 8 to the body 4 to rotate the body 4 around the axis XX' of rotation of the wheel 3.

[0041] By "rotor of the electric motor 7", we mean here the rotating elements of said motor, these rotating elements including the motor shaft, when such a shaft is present.

[0042] Motor 7 also includes a stator which here groups together all the static elements of motor 7.

[0043] To minimize the width (i.e., thickness) of the electric drive wheel 3 without hindering its operation, the motor shaft YY' and the rotation axis XX' of wheel 3 are non-coaxial and non-parallel. Furthermore, the motor shaft YY' and the rotation axis XX' of wheel 3 do not intersect.

[0044] In practice, the motor shaft YY' extends in a plane P that is substantially perpendicular, that is, perpendicular to within ±10°, to the axis XX' of rotation of the electric wheel 3. The motor shaft YY' and the axis XX' of rotation of the wheel 3 are orthogonal to each other, as can be seen in Figure 3, which reduces the width of the electric wheel 3.

[0045] Motor 7 is an electric motor of the smallest possible size. Ideally, motor 7 has an overall diameter of less than 40 mm for a robot, 50 mm for a lawnmower, 70 mm for a snowplow, and 120 mm for a tractor. Such a motor 7 rotates at high speed. It is therefore essential that the system 9 for transmitting the rotational motion from the rotor 8 of motor 7 to the wheel body 4 of wheel 3 incorporates a speed reducer. This speed reduction is achieved through the design of the gear that transmits the motion.

[0046] As can be seen in figure 4, the system 9 for transmitting the rotational movement of the rotor 8 to the body 4 comprises a driven element in the form of a toothed gear 10 fixed in rotation to the body 4 and a driving element, in the form of a worm gear 11 suitable for being driven in rotation by the motor 7.

[0047] This worm gear 11 can therefore be rotationally coupled to the rotor 8 of the motor 7, that is, configured to be driven in rotation by the rotor. This worm gear 11 engages directly with the teeth 10. This worm gear 11 and the motor shaft YY' can be coaxial. Thus, the worm gear can directly engage with the rotor 8 of the motor 7. This connection is either permanent or made in a switchable / disconnectable manner. In the example shown, the rotor incorporates a motor shaft along the extension of which the worm gear is located. Alternatively, the worm gear can be connected to indirectly via, for example, a gear engaged with the rotor 8 of the motor 7.

[0048] This worm screw 11 extends in a plane P substantially perpendicular to the axis of rotation XX' of the wheel, that is to say perpendicular to within 10° of said axis of rotation XX' as illustrated in figure 6.

[0049] The tooth 10 is a circular tooth with a circle centered on the axis XX' of rotation of the wheel 3 and the worm 11 comes into direct contact by meshing with the tooth 10.

[0050] As shown in Figure 6, the toothing 10 includes teeth 12, called axial teeth, which extend outward from a plane P2 perpendicular to the axis XX' of rotation of the wheel 3. Ideally, the toothing 10 and at least part of the body 4 are made in one piece, for example in synthetic material.

[0051] In the example shown in Figure 7, the body 4 comprises two facing walls 19 forming the sides or rims of the wheel 3 and a circumferential peripheral wall 20 connecting said facing walls 19 to each other and forming the rim of the wheel 3. The circumferential peripheral wall may incorporate a tread or this tread may be attached.

[0052] In the example shown in Figure 11, the tread, represented as 200, is attached. A portion of this tread 200, which is made of elastic material, is sandwiched between a portion of the circumferential peripheral wall 20 and a portion of one of the walls 19 forming a flank of the wheel 3 in the coupled state of the peripheral wall 20 and the wall 19 forming a flank of the wheel 3. This sandwiching ensures the sealing of the cavity 6 delimited by the body 4 at this point. The coupling is achieved, in the example shown, by means of screws 27.

[0053] The facing walls and the circumferential wall can be made of a synthetic material, and the teeth are formed in one piece with one of the two facing walls 19. Thus, the teeth project from the face of said wall towards the facing wall. It is therefore understood that the rotation of the worm gear engaged with the motor rotor drives, by meshing of the worm gear with said teeth, the rotation of the wheel body.

[0054] The worm screw 11 has at least one helical thread 111 with at least one turn, i.e., at least one revolution. Each thread 111 is formed of two opposing flanks 112 joined by a vertex 113, as illustrated in Figure 16. Ideally, the single-threaded worm screw comprises only one thread. This thread 111 is preferably trapezoidal. The flanks 112 are preferably shown in cross-section and, as illustrated in Figure 16, symmetrical with respect to a plane intersecting the axis of rotation of the worm screw. Ideally, the thread 111 of the worm screw has a helix angle p greater than 10°, preferably greater than 15°, and a thread pressure angle α corresponding to the angle formed by one of the thread flanks with a plane orthogonal to the axis of rotation of the worm screw, preferably greater than 25°. The helix angle value allows for good worm gear / wheel reversibility and better gear efficiency.The tangent of this helix angle is equal to the pitch p of the thread divided by the product fl x dp with dp corresponding to the pitch diameter of the worm gear, as illustrated by the triangle in Figure 16.

[0055] The worm 11 is, at least in its meshing zone with the teeth 10, a worm with a cylindrical profile, meaning that it has at least a constant diameter or outer radius measured at the tip of the thread. This provides a greater degree of freedom in terms of position along the longitudinal axis of the worm. The pitch diameter dp and the module of the worm 11 in this meshing zone are constant.

[0056] Similarly, the inner diameter di of the worm, corresponding to the diameter of the cylindrical body of the worm carrying the helical thread, is constant. This helical thread of the worm forms a helical rib around the cylindrical body of the worm. This cylindrical body of the worm defines a cylindrical bearing surface carrying said thread. Ideally, the flanks 112 of the thread 111 are selectively in contact with the teeth according to the direction of the forces corresponding to the driving or driven state of the worm and / or the direction of rotation of the driving / driven element. Ideally, the axis of rotation of the worm 11 is offset from a plane parallel to the axis of rotation of the worm and passing through the axis XX' of rotation of the wheel 3 by a distance less than the largest radius of the circular teeth 10, this distance being expressed in millimeters. being preferably less than or equal to half the maximum diameter of the teeth expressed in millimeters minus 30.

[0057] To optimize the position of the motor 7, as illustrated in Figure 3, the motor 7 is arranged inside a fictitious cylinder 13, that is, an imaginary or virtual cylinder, whose axis coincides with the axis XX' of rotation of the wheel 3 and whose diameter is equal to the largest diameter of the circular teeth 10. Ideally, the motor 7 is arranged inside a fictitious cylinder 13, that is, an imaginary or virtual cylinder, whose axis coincides with the axis XX' of rotation of the wheel 3 and whose diameter is equal to the smallest diameter of the circular teeth 10.

[0058] To enable the wheel body 4 to rotate around the axis XX' of rotation of the wheel 3, the wheel 3 includes a shaft called the wheel shaft 14, around which the hub 5 is mounted. A seal, shown as 23 in Figure 11, provides a seal between the wheel shaft 14 and the hub 5. The cavity defined by the body is therefore, in the assembled state of the electric wheel 3, a closed cavity. The shaft 14 carries a motor support 15, which is at least partially located inside the cavity of the body 4. The hub 5 is formed by a simple circular opening inside at least one of the walls 19 facing the wheel body 4, into which a portion of the wheel shaft 14 is inserted. This wheel shaft 14 carries the motor support 15, to which the motor 7 is coupled directly or indirectly. The wheel shaft 14 / motor support 15 assembly forms a fixed rotating assembly around which the wheel body 4 rotates.An example of motor mount 15 is provided in figure 9.

[0059] As can be seen in Figure 8, the motor support 15 includes a through-hole so that it can be threaded onto the wheel shaft 14, forming a fixed assembly with it during movement. For this purpose, the housing may have grooves into which axial ribs of the wheel shaft 14 fit. This motor support 15 is preferably made of a synthetic material. Alternatively, this motor support 15 may be made of metal, in particular an aluminum alloy. This motor support 15 is generally triangular in shape, but its shape may vary. This motor support 15 is housed at least partially inside the cavity 6 of the body 4.

[0060] To allow the body 4 to rotate around the wheel shaft 14, bearing elements are provided. These bearing elements are visible in Figure 8.

[0061] The motor support 15 includes a housing 16, visible in figure 1, with an axis orthogonal to the axis of the through housing for receiving the wheel shaft 14. This housing 16 serves to receive the worm gear 11, which is mounted to rotate freely via at least one bearing 22 inside the housing 16. This bearing or these bearings 22 allow, in addition to the rotation of the worm gear 11 relative to the motor support 15, the coupling of the worm gear 11 to the motor support 15 by means of an external circumferential shoulder of the worm gear 11, visible in Figure 4. The associated bearing 22 is axially immobilized in the housing 16 by means of a locking member, such as a clip 26, visible in particular in Figures 1 and 5. A part of the motor, other than the rotor 8 and represented as 71 in Figure 13, is positioned in contact with a portion 151 of the motor support 15, which acts as a stop to prevent the rotation of said part of the motor.Thus, the part of the motor not to rotate is immobilized in rotation by simple contact of pressure on the motor support 15. The motor 7 extends in cantilever relative to the worm screw 11.

[0062] To allow meshing, even when the wheel body 3 is deformed (4), the wheel body 4 includes, located inside the cavity 6 of the wheel body 4 and rotationally fixed to the wheel body 4, at least one circular track 17 with its center located on the axis XX' of rotation of the wheel 3, extending coaxially with the teeth 10. In practice, preferably, the track 17 surrounds the teeth 10. The track 17 is thus located as close as possible to the rim. The spacing between two opposing tracks is therefore better controlled. The motor support 15 is equipped, for each track, with one or more guide elements 18. Each guide element 18, such as a bearing or a slide, is capable of making rolling or sliding contact with said track 17.

[0063] In the example shown in Figures 4 and 5, two guide members 18 are provided, each formed by a bearing. Each bearing is screwed to the motor support 15. To ensure optimal guidance without having to multiply the guide members 18, the guide members 18 extend on both sides from a radial plane P1 to track 17 and passing through the area of ​​engagement of the worm gear 11 and the teeth 10.

[0064] Examples of guide elements 18 are provided in Figure 10. Each guide element 18 can be a rolling or sliding guide element and may or may not be rotary. Each guide element 18 can be made in one piece with another guide element, as illustrated in Figure 10. The guide elements can be mounted in a separate manner on a common support.

[0065] Each circular track 17 is arranged opposite another circular track. The circular tracks 17 are thus arranged opposite each other on the walls 19 opposite the body 4 for the confinement of the guide elements 18 between said tracks.

[0066] As can be seen in Figure 8, the motor support 15 is mounted with clearance on the wheel shaft 14 to allow it to oscillate around an axis orthogonal to the axis XX' of rotation of the wheel 3. This clearance is present at the through-hole of the motor support 15, allowing the motor support 15 to be threaded onto the wheel shaft 14. Thus, even in the event of deformation of the wheel 3, the guide elements 18 can bear against the body of the wheel 3 at the level of the tracks 17. The guide elements 18 therefore simultaneously ensure, by bearing contact with the tracks 17, guidance guaranteeing the possibility of coupling by meshing between the teeth 10 and the worm gear 11.

[0067] To supply power to the motor 7, an electrical wiring harness 21 is provided. This wiring harness 21, visible in Figures 7 and 15, passes through the wheel shaft and the hub. This wiring harness 21 allows connection to the power supply battery when the motor's power supply battery is located outside the body 4. This electrical wiring harness 21 allows recharging of the power supply battery when the wheel motor's power supply battery 210 is housed inside the cavity 6 of the body 4. Obviously, a single wheel can include one or more electric motors. The control of the motor(s) 7 is achieved using a control unit 25, visible in Figures 14 and 15. This control unit 25 is in the form of a system Electronics and computer science, which includes, for example, a microprocessor and working memory. Depending on one aspect, the control unit may take the form of a programmable logic controller (PLC). In other words, the functions and steps described can be implemented as a computer program or via hardware components (e.g., programmable gate networks).In particular, the functions and steps performed by the control unit or its modules can be carried out by instruction sets or computer modules implemented in a processor or controller, or by dedicated electronic components, or by components such as field-programmable gate arrays (FPGAs), or application-specific integrated circuits (ASICs). It is also possible to combine computer and electronic components.When it is specified that the unit or means or modules of said unit are configured to perform a given operation, this means that the unit includes computer instructions and the corresponding means of execution which enable said operation to be performed and / or that the unit includes corresponding electronic components.

[0068] The control unit 25 and the battery 210 are, when arranged inside the cavity 6 of the body 4, fixed to the motor support 15.

[0069] The operation of such a wheel is simple. The supply of electricity to the motor 7 causes a rotation of the rotor 8 which in turn drives the worm gear 11 which meshes with the teeth 10 which are fixed in rotation to the body 4 of the wheel 3. The guide members 18 ensure in parallel, by contact with the tracks 17, a guidance guaranteeing a possibility of coupling by meshing between the worm gear and the teeth.

Claims

Demands

1. Electric wheel (3) comprising a hollow body (4) having a hub (5) defining an axis of rotation (XX') of the wheel, said hollow body (4) delimiting a cavity (6) inside which are housed an electric motor (7) with a rotor (8) capable of rotating about a motor shaft (YY') and a system (9) for transmitting the rotational motion of the rotor (8) to the body (4) to rotate the body (4) about the axis of rotation (XX') of the wheel (3), the motor shaft (YY') which does not intersect the axis of rotation (XX') extending in a plane (P) substantially perpendicular to the axis of rotation (XX') of the wheel (3) and the rotating body (4) comprising teeth fixed in rotation to said body (4), these teeth (10) being circular teeth with a circle whose center is disposed on the axis of rotation (XX') of the wheel (3),characterized in that the transmission system (9) comprises a worm screw (11) that can be rotationally locked to the rotor (8) and meshed with the teeth (10).

2. Electric wheel (3) according to claim 1, characterized in that the worm gear (11) and the motor shaft (YY') are coaxial.

3. Electric wheel (3) according to any one of claims 1 or 2, characterized in that the worm gear (11) extends in a plane (P) substantially perpendicular to the axis of rotation (XX') of the wheel (3).

4. Electric wheel (3) according to any one of claims 1 to 3, characterized in that the teeth (10) comprise axial teeth (12) which extend in projection from a plane (P2) perpendicular to the axis of rotation (XX') of the wheel (3).

5. Electric wheel (3) according to any one of claims 1 to 4, characterized in that the body (4) comprises two facing walls (19) forming the sides or webs of the wheel and a circumferential peripheral wall (20) connecting said facing walls (19) to each other and forming the rim of the wheel, in that the teeth (10) project out of one of the two facing walls (19) in the direction of the other of said facing walls (19), in that the motor (7) is arranged inside a fictitious cylinder whose axis coincides with the axis of rotation (XX') of the wheel (3) and whose diameter is equal to the largest diameter of the circular teeth (10).

6. Electric wheel (3) according to any one of claims 1 to 5, characterized in that the teeth (10) and at least a part of the body (4) are made of a single piece.

7. Electric wheel (3) according to any one of claims 1 to 6, characterized in that the wheel (3) comprises a shaft (14), called wheel shaft, around which the hub (5) is mounted, this wheel shaft (14) carrying a motor support (15) disposed inside the cavity (6) of the body (4), the motor (7) being coupled directly or indirectly to said motor support (15).

8. Electric wheel (3) according to claim 7, characterized in that the motor support (15) comprises a housing (16) inside which the worm gear (11) is mounted freely for rotation, this worm gear (11) being couplingable to the rotor (8) of the motor (7), a part of the motor (7) other than the rotor (8) being positioned in contact with a part of the motor support (15) forming a stop for immobilizing said part of the motor (7) in rotation.

9. Electric wheel (3) according to any one of claims 7 or 8, characterized in that the body (4) comprises, disposed inside the cavity (6) of the body (4) and rotationally fixed to the body, at least one circular track (17) of circle center disposed on the axis of rotation (XX') of the wheel (3) to extend coaxially with the teeth (10), and in that the motor support (15) is equipped, by track (17), with one or more guide elements (18), each guide element (18), such as a bearing or a pad, being able to come into rolling or sliding contact with said track (17).

10. Electric wheel (3) according to claim 9, characterized in that the motor support (15) being for the or at least one of the tracks (17) equipped with several guide members (18), said guide members (18) extend on either side of a plane (P1) radial to the track (17) passing through the worm gear (11) / tooth (10) engagement zone.

11. Electric wheel (3) according to claim 9 or 10, characterized in that the body (4) comprises two facing walls (19) forming the flanks or sails of the wheel (3) and a circumferential peripheral wall (20) connecting said facing walls (19) to each other and forming the rim of the wheel (3), the circular tracks (17) are at least two in number and are arranged opposite each other on the walls (19) opposite said body (4).

12. Electric wheel (3) according to any one of claims 7 to 11, characterized in that the motor support (15) is mounted with clearance on said wheel shaft (14) so ​​as to be able to oscillate about an axis orthogonal to the axis of rotation (XX') of the wheel (3).

13. Electric wheel (3) according to any one of claims 1 to 12, characterized in that the worm (11) has at least one helical thread (111) with at least one turn, in that the thread or each thread (111) is formed of two opposite flanks (112) joined by a vertex (113) and in that the worm (11) is at least in its area of ​​engagement with the teeth a worm with a cylindrical profile.

14. Electric wheel (3) according to claim 13, characterized in that the single-threaded worm (11) comprises a single helical thread (111) and in that the thread (111) of the worm (11) has a helix angle (0) greater than 10°, preferably greater than 15°, and a thread pressure angle (a) corresponding to the angle formed by one of the flanks (112) of the thread with a plane orthogonal to the axis of rotation of the worm (11) preferably greater than 25°.

15. Rolling machine (1) characterized in that it is equipped with at least one electric wheel (3) conforming to one of claims 1 to 14.

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