EP2094559A1

EP2094559A1 - Bicycle drive assistance motor

Info

Publication number: EP2094559A1
Application number: EP06824249A
Authority: EP
Inventors: Jan Roelf De Vries
Original assignee: Individual
Current assignee: Individual
Priority date: 2006-11-07
Filing date: 2006-11-07
Publication date: 2009-09-02
Also published as: WO2008056973A1

Abstract

A stationary part (3, 23) and a rotary part (2; 22) of a bicycle drive assistance motor extend circumferentially in coaxial ring shaped areas leaving an opening (4; 24) centrally within the ring-shaped areas for accommodating at least a portion of a hub (12; 32) of a bicycle wheel (11; 31) or at least a portion of a pedal drive gear mechanism inside a hub of a bicycle wheel. Combinations of such a motor and an internal multi-gear drive mechanism in a hub of a bicycle wheel are also described.

Description

TITLE: Bicycle drive assistance motor

TECHNICAL FIELD AND BACKGROUND ART

This invention relates to a bicycle drive assistance motor. Bicycles provided with a drive assistance motor for providing driving power principally in addition to a cyclist's pedaling power are known in various forms. Generally, such motors provide drive assistance as a function of the driving power exerted by the pedaling cyclist, and automatically shuts down when the cyclist stops pedaling, or when the brake is used.

A common solution is to arrange the motor in the hub of the rear wheel. However, the space available inside the hub is limited, in particular if also a drive mechanism allowing switching between different gears of the pedal drive train is to be accommodated inside the hub. It is known to combine pedal drive assist motors with derailer gearing systems, which are exposed to soiling and therefore need relatively intensive maintenance. Also, derailer gearing systems do not allow gears to be switched when the bike is stationary, which makes such systems less suitable for use in city traffic with many stops.

It is also known to integrate the pedal drive gear system with the motor. However, such an integrated system is technically complicated and expensive. Also, such an integrated solution is particularly costly if it is intended to provide an existing, not power assisted bicycle with a motorized drive assistance, because the original hub needs to be replaced by a new hub.

SUMMARY OF THE INVENTION

It is an object of the invention to provide a solution which facilitates combining a drive assistance motor for driving a bicycle wheel with a hub of a bicycle wheel and/or with an in-hub pedal drive gear mechanism. According to the present invention, this object is achieved by providing a motor according to claim 1. The arrangement of the rotary part and the stationary part provides that a relatively large motor can be arranged together with a hub of a bicycle wheel and/or with an in-hub pedal drive gear mechanism in the limited space available between the arms of the fork of the bicycle. Thus, a motor according to the invention is very suitable to be fitted as an addition to a bicycle wheel hub with or without an internal pedal drive gear mechanism. A motor according to the invention is also very suitable to be mounted inside a hub together with a pedal drive gear mechanism that allows switching between different pedal drive gear ratios. Room for at least a portion of the hub and/or of the pedal drive gear mechanism is left inside the rotary and stationary parts of the motor.

Particular embodiments of the invention are set forth in the dependent claims.

Further aspects, effects and details of the invention are set forth in the detailed description with reference to examples of which some are shown in the schematic drawings.

BRIEF DESCRIPTION OF THE DRAWINGS

Fig. 1 is a cross sectional view of an example of an electric motor according to the invention; Fig. 2 is a cross sectional view of the motor shown in Fig. 1 mounted to a bicycle wheel;

Fig. 3 is a perspective, cross sectional view of an alternative example of an electric motor according to the invention;

Fig. 4 is a cross sectional view of the motor according to Fig. 3 mounted to a bicycle wheel;

Fig. 5 is a side view of a motor according to Figs. 3 and 4 mounted in a rear fork of a bicycle; and

Fig. 6 is a side view of a bicycle fitted with a motor and a power supply.

MODES FOR CARRYING OUT THE INVENTION

The invention is first discussed with reference to the example shown in Figs. 1 and 2. A motor 1 has a stationary part 3 equipped with a stator 10 and a rotary part 2 equipped with a rotor 9. The stationary part 3 and the rotary part 2 extend circumferentially in coaxial ring shaped areas leaving an opening 4 centrally within the ring-shaped areas. When the motor 1 is mounted to a bicycle wheel 11, as is snown in Fig. 2, the central opening 4 accommodates a portion of the hub 12 of the bicycle wheel 11.

The rotary part 2 includes a housing that is fixed against rotation relative to the rotor 9 and the stationary part 3 includes a housing fixed against rotation relative to the stator 10. The stationary part 3 is fixable to a bicycle frame against rotation relative to the bicycle frame via a bracket that can be bolted to the stationary part 3 via bolts 6. In the present embodiment, the rotary part 2 and the stationary part 3 are rotatably mounted to each other. This allows the motor 1 to be preassembled and to be mounted to a wheel 11 as one subassembly, so that it can easily be fitted to a bicycle. Thus, a motor according to the invention facilitates modular production, in which the same wheel hub 12 can be used for bicycles with and without the bicycle drive assistance motor.

A bearing 17 keeps the stationary part 3 centered relative to the rotary part 2 and ensures low resistance rotation of the rotary part 2 in relation to the stationary part 3. The stationary part 3 is anchored to the bicycle frame against rotation about the axis of rotation of the wheel, the other degrees of movability being left sufficiently free to allow the stationary part 3 to accommodate its position to the position of the rotary part 2 which is fixed to the hub 12 of the bicycle wheel 11.

The rotary part 2, and the stationary part 3 also leave the central opening 4 free. The rotary part 2, and the stationary part 3 may be of non- circular shape, the rotary part 2 can for instance include one or more spokes carrying the rotor 9. In the present example, the motor 1 is a brushless electric motor, however other types of electric motors may also be employed. The rotor 9 is part of the rotatable part 2 of the motor 1 and is formed by circumferentially distributed permanent magnets. The rotatable part 2 has a flange 18 in which holes (not shown) have been provided for mounting the motor 1 to a wheel 11. In use, the rotatable part 2 rotates along with the wheel 11 to which it is mounted.

The stator 10 of the motor 1 according to the present example is a rotationally fixed part of the stationary part 3 of the motor 1 and formed by stator coils. In use, the stationary part 3 remains stationary relative to the bicycle frame and drives rotation of the rotatable part 2.

Fig. 2 shows the motor 1 mounted on a wheel 11. Because the motor 1 extends around the hub 12 of the wheel 11, it can be mounted in combination with a hub 12 of usual width, which hub 12 may for instance contain a pedal drive gear mechanism and/or a brake mechanism, yet be accommodated between conventionally designed arms of a rear fork of a bicycle.

The driven part 2 of the motor is directly connected to the wheel 11. By directly connecting the rotor to the wheel 11 no separate mechanism is needed to transfer the power from the motor 1 to the wheel 11 and the motor 1 can be fitted to many types of wheels 11. Also, because the motor 1 does not interfere with the internal hub gears, a minimum of moving parts is needed and the direct drive provided by the motor, in parallel to (i.e. not through) the pedal drive gear train is advantageous for obtaining a high driving efficiency and for reducing wear of the pedal drive gear train.

The rotary part of the motor 1 can be mounted to the hub of a bicycle wheel. In the present example,, the rotary part 2 of the housing shown in Figs. 1 and 2 is adapted to be mounted to a brake disc support 13 portion of the hub 12 by bolts 6, which are shown in exploded view mode. The brake disc support 13 forms a rigid part of the hub 12 that is rotationally fixed to and rotates with the wheel 11 when in use and is typically dimensioned to withstand high loads. Therefore, the brake disc support 13 is particularly suitable for carrying the rotatable part 2, of the motor 1. The braking function may for instance be provided, instead of by a disc brake, by rim brakes with brake pads engaging flanges of the rim of the wheel 11.

However, in the present example, a brake disc 8 is mounted to the rotatable part 2 of the motor 1. The rotatable part 2 has a flange 7 to which the brake disc 8 is attached. In this manner the wheel 11 can be provided with a brake disc 8 while the original support for the brake disc 8 is used for mounting the motor 1. In an alternative embodiment, the brake disc can for example be an integral part of the motor housing.

In the present example, the motor 1 is part of a motor unit having a housing that is to be attached to the housing of a hub of a bicycle wheel. However, as an alternative within the framework of the present invention, the motor 1 may be arranged in a hub housing that also contains a pedal drive gear mechanism. The hub is then designed to include both the gear drive mechanism and the motor, the motor extending around at least a portion of the gear drive mechanism. An alternative example of a motor 21 according to the invention is shown in Figs. 3 and 4. In this example, the motor 21 has a larger width in axial direction of the hub 32 of the wheel 31 while still being suitable to be mounted in a fork of a bicycle without interfering with the arms of the fork. The rotatable part 22 of the motor unit 21 has a flange 20 extending circumferentially about the axis of rotation of the motor unit 21. The flange 20 is adapted for attaching spokes 34 thereto. By connecting the spokes 34 to the rotatable part 22 of the motor 21 unit instead of to the hub 32, the motor 21 can extend axially inwardly into an area that is normally intersected by the spokes extending in a conical plane between the flange 35 of the hub and the rim 36 of the wheel 31, and can be more robust, with a larger stator 30 and rotor 29, capable of delivering more power to the wheel 31. The stator 30 of the motor 21 according to the present example is a rotationally fixed part of the stationary part 23 of the motor 21 and formed by stator coils. The rotor 29 formed by permanent magnets attached to the inside of the housing of the rotatable part 22 extends on the outside around the stator 30. The stationary part 23 is bearing-mounted around a portion of the rotary part 22 that is located radially inside the stationary part 23 to be mounted against a rotary- portion of the hub 32 (which in turn is bearing mounted to a portion of the hub 32 that is fixed to the bicycle frame when in mounted condition). Threaded bores 47 are provided in the stationary part 23 for mounting a torque transfer arm 43 thereto, for supporting the stationary part 23 against rotation relative to a bicycle frame. This is required, because the stationary part 23, being bearing-mounted around a portion of the rotary part 22, is not fixed to a stationary part of the hub 32. The bearings 37, 38 maintain the stationary part 23 centered relative to the rotary part 22.

When mounting a motor 21 according to the present example to an existing, spoked wheel 31, the spokes connecting to the flange 35 of the hub 32 on the side to which the motor 21 is to be attached are removed. Then, the rotatable part 22 of motor 21 is mounted to the hub 32 of the wheel 31, preferably to the brake disc support as according to the previous example, and then new, shorter spokes 34 are mounted between the rim 36 of the wheel 31 and the flange 20 of the electric motor 21. When manufacturing a new wheel 31, the motor 21 and the hub 32 are preferably mounted to each other before any the spokes is mounted. Also the present example illustrates that a motor according to the invention allows to manufacture bicycles with and without an electric drive assist motor using the same bicycle wheel hub, with or without an integrated multi-gear pedal drive gear system.

A brake disc 39 is bolted to a flange 40 extending circumferentially on the outside of the rotary part 22, so that a brake disk is still available for performing the braking function.

Replacement of the spokes on one side of a wheel can be carried out in a conventional bicycle repair shop. Thus, the motor 21 can be mounted as an accessory to many existing used and new bicycles available on the market, as a routine workshop job.

Fig. 5 shows an example an anchoring of the stationary part 23 of the motor 21 to a bicycle frame 42 against rotation relative to the bicycle frame. A torque transfer arm 43 projects from a mounting foot 46 that is bolted to the stationary part 23 of the motor 21 by bolts 26. The bolts 26 are screwed into threaded bores 47 (see Fig. 3).

The bicycle frame 42 is equipped with a brake caliper mounting bracket 41. The torque transfer arm 43 is connected to the brake caliper mounting bracket 41 via pins 44 engaged in holes in the brake caliper mounting bracket 41. To accommodate for manufacturing and mounting tolerances, the connection between the torque transfer arm 43 and the brake caliper mounting bracket 41 preferably allows at least a limited amount of movability of the torque transfer arm 43 relative to the brake caliper mounting bracket 41 in as far as degrees of freedom of movability other than rotation about the axis of the wheel are concerned. To this end, for example, the holes in the brake caliper mounting bracket 41 may be provided with rubber bushings for flexibly containing the pins 44 with which the torque transfer arm 43 is connected to the brake pad holder. Alternatively, the pins 44 may be guided in grooves extending radially in relation to the axis of rotation of the motor 1. The torque transfer arm 43 is equipped with bores in a pattern identical to the pattern of the bores in the brake caliper mounting bracket 41. Thus, torque transfer arm 43 also forms a replication of the brake caliper mounting bracket 41 and allows a brake caliper to be mounted thereto for co- operation with the brake disc 39.

Fig. 6 shows a bicycle 15 equipped with a motor 1 according to the invention. Because the motor 1 extends mainly radially on the outside of the hub, closely along the spokes 14 of the wheel 11, a wheel 11 equipped with such a motor 1 can be fitted to a bicycle without requiring additional room between the legs of the fork of the bicycle. Thus, substantial modifications to the frame of the bicycle, or to the wheel 11, are not necessary.

The bicycle 15 is further provided with a rechargeable battery 16 for supplying the motor 1 with power. The battery can be attached to the frame or may for example be arranged in a bicycle bag which can be hung to the luggage carrier of the bicycle 15.

The motor 1 can for example be controlled by a control device mounted to the steering bar of the bicycle 15. The control panel can be connected to the motor 1 through wires running along the frame of the bicycle 15. However, the control panel and the motor control can also be arranged for control of the motor by the control device via wireless communication.

From the foregoing, it will be clear to the skilled person, that within the framework of invention as set forth in the claims also many variations other than the examples described above are conceivable. For instance, the motor can be fitted to a wheel without an internal pedal drive gear mechanism, to a wheel provided with drum brakes and/or to another part of the wheel, such as to the spokes (e.g. wire spokes or other spokes, such as cast or forged metal spokes, or composite material or molded spokes) or to a flange of the hub normally used for attaching spokes to the hub. Instead of to a rear wheel, the motor can also be attached to a front wheel of a bicycle. Also, both the front wheel and rear wheel can be provided with an electric motor according to the invention.

Claims

1. A bicycle drive assistance motor, comprising a stationary part (3; 23) and a rotary part (2; 22), wherein the stationary part (3; 23) and the rotary part (2; 22) extend circumferentially in coaxial ring shaped areas leaving an opening (4; 24) centrally within said ring-shaped areas for accommodating at least a portion of a hub (12; 32) of a bicycle wheel (11; 31) or at least a portion of a pedal drive gear mechanism inside a hub of a bicycle wheel.

2. A motor according to claim 1, wherein the rotary part (2, 22) is adapted to be mounted to the hub (12, 32) of the bicycle wheel (11; 31), and the stationary part (3; 23) is fixable to a bicycle frame against rotation relative to the bicycle frame.

3. A motor according to claim 2, wherein the rotary part (2, 22) is adapted to be mounted to a brake disc support portion (13) of the hub (12; 32).

4. A motor according to claim 2 or 3, wherein the rotatable part (2; 22) and the stationary part (3; 23) are ring-shaped.

5. A motor according to any one of the claims 2-4, wherein the rotatable part (2; 22) of the motor (1; 21) is adapted for mounting a brake disc (8; 39) thereto.

6. A motor according to any one of the claims 2-5, wherein the rotatable part (22) of the motor (21) comprises a flange (20) for attaching spokes (34) thereto.

7. A motor according to any one of the preceding claims, wherein the stationary part (3; 23) is bearing-mounted around at least a portion of the rotary part (2, 22) radially inside the stationary part (3; 23) and comprises a torque transfer arm (43) for supporting the stationary part (3; 23) against rotation relative to a bicycle frame.

8. A bicycle wheel comprising a hub and a motor according to any^¬ one of the preceding claims, the stationary part (3; 23) and the rotary part (2, 22) extending around at least a portion of a pedal drive gear mechanism inside the hub or a at least a portion of the hub.

9. A bicycle wheel comprising a brake disc support (13; 33) and a motor according to any one of the claims 1-7, mounted to said brake disc support (13; 33).

10. A bicycle comprising a bicycle frame and a wheel (11; 31) according to claim 8 or 9, wherein the stationary part (3; 23) is bearing- mounted around at least a portion of the rotary part (2, 22) mounted against the hub radially inside the stationary part (3; 23) and is fixed against rotation relative to the bicycle frame via a torque transfer arm (43).