Electrical assistance device for a bicycle and electrically assisted bicycle provided with such a device

1. An electrical assist device for a bicycle, the device comprising:

an electric machine that includes a rotor;

a drive pinion structured to be driven by the rotor of the electric machine, the drive pinion including helicoidal teeth;

a fastener structured to include a first portion that articulatingly carries the electric machine and a second portion that is fastened to the bicycle in a fixed position in a vicinity of a tire of a wheel of the bicycle, the first portion being arranged to pivot about a pivot axis with respect to the second portion; and

a source of electrical energy for powering the electric machine,

wherein the helicoidal teeth of the drive pinion are structured to mesh tangentially with complementary teeth attached to the tire, and

wherein an axis of the electric machine is at an inclined angle relative to a plane of the wheel of the bicycle when the electric machine is in a working position.

2. The electrical assist device according to claim 1 , wherein the helicoidal teeth of the drive pinion are asymmetrical teeth that include driving faces and non-driving faces, and wherein an aperture angle of the driving faces is smaller than an aperture angle of the non-driving faces.

3. The electrical assist device according to claim 2 , wherein the drive pinion is driven by the electric machine via a freewheel so that the tire does not drive the electric machine when the bicycle is moving forward.

4. The electrical assist device according to claim 1 , further comprising a display and control interface that enables a cyclist to interact with a controller that controls the electric machine.

5. The electrical assist device according claim 4 , further comprising a pedalling sensor connected to the controller.

6. The electrical assist device according claim 1 , wherein the fastener includes an oscillating arm, corresponding to the first portion, articulated to a support portion corresponding to the second portion, the oscillating arm being arranged to pivot about the pivot axis with respect to the support portion, and the support portion and the oscillating arm being arranged so that a drive force transmitted to the tire by the drive pinion generates a radial pressure in gears of the drive pinion.

7. The electrical assist device according to claim 6 , wherein an elastic spring prestresses an orientation of the oscillating arm so that, in an absence of the drive force, the drive pinion presses radially against the tire with a non-zero bearing force.

8. The electrical assist device according claim 1 , wherein the fastener defines at least two positions of the electric machine relative to the tire, the at least two positions including the working position, at which the drive pinion meshes with the teeth of the tire, and a folded position, at which the drive pinion is held away from the tire.

9. An electrical assist kit for a bicycle, the kit comprising:

a pneumatic tire having teeth attached thereto; and

an electrical assist device for the bicycle, the device including:

an electric machine that includes a rotor,

a drive pinion structured to be driven by the rotor of the electric machine, the drive pinion including helicoidal teeth,

a fastener structured to include a first portion that articulatingly carries the electric machine and a second portion that is fastened to the bicycle in a fixed position in a vicinity of a tire of a wheel of the bicycle, the first portion being arranged to pivot about a pivot axis with respect to the second portion, and

a source of electrical energy for powering the electric machine,

wherein the helicoidal teeth of the drive pinion are structured to complement the teeth attached to the tire, and the helicoidal teeth of the drive pinion are structured to mesh tangentially with the teeth attached to the tire, and

wherein an axis of the electric machine is at an inclined angle relative to a plane of the wheel of the bicycle when the electric machine is in a working position.

10. The electrical assist kit according to claim 9 , wherein the teeth attached to the tire are positioned on a flank of the tire.

11. The electrical assist kit according to claim 10 , wherein the teeth attached to the tire are asymmetric teeth that include driving faces and non-driving faces, and wherein an aperture angle of the driving faces is smaller than an aperture angle of the non-driving faces.

12. The electrical assist kit according to claim 9 , wherein a pitch of the teeth attached to the tire is between 1.8 mm and 5.5 mm, with between 1.8 mm and 2.5 mm being preferable for the pitch.

13. A bicycle comprising:

a pneumatic tire having teeth attached thereto; and

an electrical assist device for the bicycle, the device including:

an electric machine that includes a rotor,

a drive pinion structured to be driven by the rotor of the electric machine, the drive pinion including helicoidal teeth,

a fastener structured to include a first portion that articulatingly carries the electric machine and a second portion that is fastened to the bicycle in a fixed position in a vicinity of a tire of a wheel of the bicycle, the first portion being arranged to pivot about a pivot axis with respect to the second portion, and

a source of electrical energy for powering the electric machine,

wherein the helicoidal teeth of the drive pinion are structured to complement the teeth attached to the tire, and the helicoidal teeth of the drive pinion are structured to mesh tangentially with the teeth attached to the tire, and

wherein an axis of the electric machine is at an inclined angle relative to a plane of the wheel of the bicycle when the electric machine is in a working position.

14. The bicycle according to claim 13 , wherein the tire is mounted on a rear wheel of the bicycle.