The present invention relates to an auxiliary motor arrangement for a human powered vehicle, particularly to an auxiliary motor transmission arrangement for a bicycle.

For cyclists covering longer distances or those who may be less physically able, electrically-powered bicycles are used to reduce the manual effort required.

Electric bicycles have been increasing in popularity over recent years and a significant number of makes and models are available to the consumer.

However, electric bicycles are usually a bespoke construction and therefore are often expensive. Many existing cyclists may wish to consider electrical assistance but are deterred by the need to purchase a new bicycle, i.e. potentially making an existing bicycle redundant. Additionally, if a user wishes to use the bicycle in a conventional, non-powered fashion, the heavier construction and motor increases the effort required by the user. Therefore, a regular cyclist may have both an electric bicycle and a conventional bicycle.

An example of a power assisted electric bicycle can be found in US Patent No. 7963357, in which a bespoke rocker assembly is implemented for the drive wheel and gearwheel driven by the motor. This provides just one example of the complex and costly construction of dedicated electric bicycles.

It is an aim of the present invention to overcome or ameliorate one or more of the above problems.

The invention concerns an auxiliary drive arrangement mountable to a pedal- powered vehicle/bicycle, comprising a sprocket and chain assembly arranged to adapt a conventional bike sprocket/drivetrain assembly for receiving torque from an electric motor. According to a first aspect of the invention, there is provided: an auxiliary drive arrangement for a pedal-powered vehicle having a drivetrain comprising a pedal- driven sprocket and chain for connecting pedals to a driven wheel, the auxiliary drive arrangement comprising: an electric motor arranged to be mounted to the vehicle; a power source for the electric motor; a sprocket member comprising first and second sprockets, the sprocket member configured to be selectively attachable via an attachment formation to the drive train of the vehicle, the first sprocket of the sprocket member configured to operatively connected to the electric motor and the second sprocket of the sprocket member configured to be operatively connected to the pedal-driven sprocket of the vehicle to provide a drive path from the electric motor to the pedal-driven sprocket via the sprocket member.

Optionally, the drivetrain of the vehicle comprises a pair of pedal-driven sprockets and the sprocket member is configured to be mounted to one of the pedal-driven sprockets via the attachment formation.

Optionally, the attachment formation comprises a plurality of members selectively displaceable in a radial direction.

Optionally, the attachment formation is configured to engage teeth of the pedal- driven sprocket of the drivetrain.

Optionally, the attachment formation is configured to engage teeth on opposing sides of the pedal driven sprocket.

Optionally, the attachment formation is configured to engage a mounting structure for a chain guard.

Optionally, the attachment formation comprises a fastener received within an aperture on the sprocket member, the fastener selectively engageable with the aperture to prevent relative movement there-between.

Optionally, the aperture is elongate in the form of a slot and the fastener is movable along the aperture such that the attachment formation is range-taking. Optionally, the sprocket arrangement comprises a central portion, a radially-outer portion and a plurality of spokes extending therebetween.

Optionally, the aperture extends along one of the spokes.

Optionally, the central portion comprises an aperture configured to permit a pedal of the vehicle to pass therethrough.

Optionally, the attachment formation is common to both the first sprocket and the second sprocket for common mounting of the first and second sprockets to the vehicle.

Optionally, the first and second sprocket are provided in side-by-side or coaxial arrangement on the sprocket member

Optionally, the first and/or second sprocket are rotatably mounted to the attachment formation of the sprocket member.

Optionally, the first and/or second sprocket is mounted to the attachment formation via a ratchet device configured to allow relative movement therebetween in a first direction and prevent relative movement therebetween in an opposing direction.

Optionally, the motor comprises a motor sprocket, the motor sprocket being connected to an output shaft of the motor via a ratchet device.

Optionally, the power source comprises a rechargeable battery and a battery housing arranged to be mounted to the vehicle, the rechargeable battery being removably connected to the housing by a release mechanism.

Optionally, the arrangement comprises user controls arranged to control the level of power supplied to the motor from the power source and/or the speed of the motor. The arrangement may be provided in the form of a kit of parts for retrofit to an existing pedal-powered vehicle, the kit of parts comprising: the electric motor; the power source; and the sprocket member.

According to a second aspect of the invention, there is provided: a non-powered vehicle or pushbike (e.g. bicycle, tricycle etc.) comprising the auxiliary drive arrangement of the first aspect of the invention.

Optionally, the auxiliary drive arrangement is retrofit onto the non-powered vehicle or pushbike

According to a third aspect of the invention, there is provided: a sprocket member for a pedal-powered vehicle having a pedal assembly comprising pedals mounted for rotation about a pedal axis, the sprocket member comprising first and second sprockets, and a common attachment formation for common mounting of both the first and second sprockets to the pedal assembly about the pedal axis, where the sprocket member comprises a ratchet mechanism between the common attachment formation and at least one of the first and/or second sprockets.

Practicable embodiments of the invention are described in further detail below, by way of example only, with reference to the accompanying drawings, of which:

Figure 1 shows a side view of an auxiliary motor arrangement mounted to a bicycle;

Figure 2 shows a plan view of a sprocket member;

Figure 3 shows a side view of the sprocket member.

Figure 1 shows an auxiliary motor arrangement 2 mounted to a human powered vehicle 4, such as a pedal-powered vehicle. In the present embodiment, the vehicle 4 comprises a bicycle. However, it can be appreciated that the motor arrangement 2 may be used on other such human/pedal powered vehicles such as, unicycles, tricycles, pedal powered karts (i.e. with four wheels) etc.

The motor arrangement 2 comprises a motor 6 configured to provide mechanical power to propel the vehicle 4, along with an associated transmission system. The motor 6 comprises an electric motor, such as DC motor.

The motor 6 is attached to the frame 8 of the bicycle in use. In the present embodiment, the motor 6 is attached to seat tube 10, however, it can be appreciated that the motor 6 may be attached at any convenient location on the vehicle. The motor 6 is removably attached to vehicle 4, for example, using a bracket 12. The bracket may clamp onto the relevant frame member. The bracket 12 may comprise a single fixing screw, e.g. to allow easy attachment/detachment.

The motor 6 is therefore retrofittable to the vehicle 2.

The motor 6 comprises a sprocket 7 rotatably connected thereto. The sprocket 7 may be attached to and/or driven by the motor via a ratchet or other unidirectional drive arrangement. Thus the sprocket 7 is driven by the motor 6 in a first direction of rotation but may freewheel in the opposing direction. That is to say an output shaft of the motor 6 rotates in unison with the sprocket 7 in the first direction but relative rotation is permitted in the opposing direction.

The motor 6 is powered by a portable power supply 14. The power supply 14 comprises a battery system. The battery system comprises one or more removable battery supported within a battery housing 16. The battery is selectively removable from the housing to allow replacement thereof. This allows a fully or partially discharged battery to be replaced with a fully charged battery, thus mitigating the requirement for the user to wait for battery charging etc. The battery comprises a rechargeable battery, for example: a lattice structure ion transfer battery (e.g. lithium ion battery); advance lattice structured, high surface-flow batteries; Nickel-cadmium; Nickel-Metal Hydride; Lead-Oxide; or other conventional battery. The power supply 14 is mounted to the frame 8, for example, behind a seat 18. The power supply 14 may be mounted to a conventional luggage rack or the like. The power supply 14 could be mounted to one or more support arm depending radially outward from a portion of the frame or axle supporting the rear wheel. Alternatively, the power supply 14 could be mounted to the frame by a bracket in a manner similar to the bracket 12 described above.

The power supply is electrically connected to the motor 6.

The power supply 14 and/or motor 6 is operatively connected to a manual controller 20 in the form of a throttle. The throttle 20 allows selective actuation of the power supplied to the motor 6, thereby activating or deactivating the motor 6. In one example, the manual controller could provide a simple switch to turn on/off the motor 6. However the throttle 20 will typically allow for variable control of the speed at which the motor 6 operates, i.e. by varying the supply of power thereto from the power supply 14. The throttle 20 is provided on the handle bars 22, however, it can be appreciated that the throttle may be provided on any suitable location preferred by the user. The throttle may comprise a rotatable handle portion, a lever, one or more button/switch, or similar. The power supply 14 comprises electronic control circuitry to control power to the motor, for example, in response to the position of the throttle. The control circuitry may comprise voltage and/or current regulation., as will be understood by the person skilled in the art. As shown in figures 2 and 3, the transmission system of the auxiliary motor arrangement 2 comprises a sprocket member 24 (i.e. as may otherwise be referred to as a toothed wheel, gear wheel or cog member). The sprocket member 24 is configured to be selectively attached to a conventional sprocket forming part of the drivetrain of the bicycle, i.e. the main sprocket driven by the pedals of a conventional bicycle.

The sprocket member 24 comprises a plurality of spokes 26 extending between a central/hub portion 28 and outer annular portion 30 thereof. The spokes 26 comprise an elongate slot 32 extending along the axial length thereof.

The elongate slot 32 is configured to movably receive a fastener 33 (e.g. a nut and bolt) therein. Whilst only one fastener 33 is shown in figure 2, it will be appreciated that each slot 32 will typically have its own fastener.

The sprocket member 24 is configured to be larger than a conventional bicycle sprocket, such that the fasteners 33 mounted within the respective slots 26 can engage an outer edge of the bicycle sprocket and be mounted within respective teeth thereon. That is to say the fasteners 33 can engage the teeth of a conventional bicycle sprocket.

Alternatively, the fasteners 33 may engage apertures on the bicycle sprocket configured to allow attachment of a chain guard (i.e. the sprocket may replace the chain guard). For example, the fasteners 33 may be screwed into apertures provided on spokes of the bicycle sprocket.

The sprocket member 24 is thus clamped on the bicycle sprocket via the fasteners and the sprocket member 24 can rotate with the existing bicycle sprocket when mounted thereto. The sprocket member 24 thus provides a bespoke sprocket attachment for an existing bicycle sprocket to adapt it for use with the motor 6. The sprocket member provides at least one sprocket, i.e. an annular array of gear teeth, disposed radially outside of the existing sprocket teeth.

The fastener 33 is selectively engageable with the spoke 26 (i.e. the nut is tightened against the bolt to clamp the spoke 26 therebetween), such that its position along the elongate slot 32 may be varied. The fasteners 33 can therefore be adjusted in position along the slot 32 to accommodate varying sizes of bicycle sprocket.

In the present embodiment, the sprocket member 24 is attached to the bicycle sprocket comprising a manual actuator (i.e. the pedals 34). The central portion 28 of the sprocket member 24 comprises an aperture 36 therein of size and shape sufficient to receive the pedal 34. This allows the sprocket member 24 to be mounted to the existing bicycle sprocket without removing the pedals, i.e. by moving the aperture 36 over the pedal and then affixing member 24 to the existing sprocket.

As shown most clearly in figure 3, the sprocket member 24 comprises a first sprocket 24A and a second sprocket 24B. The first and second sprocket are provided in a side-by-side arrangement and are aligned with one another (e.g. are coaxial). A gap 39 is provided between the sprockets 24A and 24B, e.g. a lateral gap or clearance sufficient to accommodate a different chain on each sprocket.

The first sprocket 24A is configured to be operatively connected to the motor 6 in use. The first sprocket 24A is connected to the motor 6 via a chain or the like attached around the motor sprocket 7, i.e. forming a loop around sprockets 24A and 7.

The second sprocket 24B is configured to be operatively connected to a drive train of the bicycle. In the present embodiment, the second sprocket 24B is connected to rear wheel sprocket 38 via a chain or the like, i.e. forming a loop around sprockets 24B and 38.

Whilst the first 24A and second 24B sprocket are shown as being of the same diameter, they could be of differing diameters in other examples. They could have the same or different numbers of teeth. The chains used are conventional in form and will not be described for brevity. The first and second sprocket may be provided as a single/fixed structure. The first and second sprocket are mounted using a common mounting/hub structure (e.g. the spokes 26, central portion 28 and outer portion 30).

The sprocket arrangement 24 comprises a rachet arrangement 40. The ratchet arrangement 40 allows rotation of the first 24A and/or second 24B sprocket (i.e. the sprocket teeth 42) relative to the outer portion 30 of the sprocket member 24 in a first direction, but prevents relative rotation in a second direction. The sprocket teeth 42 are therefore attached to the hub structure (e.g. the outer potion 30) via the ratchet mechanism 24

Taking figure 2 as an example, this allows transmission of power from the pedals when rotated in the clockwise direction (i.e. when pedalled forward) as the rachet is engaged, causing the hub and sprocket to rotate in unison. However the ratchet allows the pedals to be moved clockwise or remain idle as the rachet is disengaged in the opposing direction. This prevents the pedals from being driven when the user is idle or if the pedals are being rotated slower than driven rotation of the sprocket 24 by the motor 6, thereby reducing the likelihood of injury to the user.

A ratchet arrangement 40 is interposed between the outer portion 30 and the first and second teeth. The ratchet arrangement 40 is substantially annular.

The auxiliary motor arrangement 2 provides power to the drive train of the bicycle. This reduces the effort required by the user to drive the vehicle. The auxiliary motor arrangement 2 may be used on conjunction with the user’s power input (i.e. pedalling) or may be used to provide all of the driving power. Additionally, the system allows the user to operate the bicycle in a conventional fashion, by using human power only.

The ratchet arrangement described herein means that the user does not pedal against the resistance of the motor when it is inactive. The rear wheel sprocket 38 may also comprise a ratchet.

The power supply 14 may vary the power supplied to the motor 6 according to the user control input via the control interface 20. Various modes of control and associated sensors could be used. For example, electric power to the motor could be cut when the brakes are applied. Additionally or alternatively, the auxiliary motor arrangement 2 may be configured to provide a fixed speed of the vehicle 2 or a fixed torque output.

The vehicle 2 may comprise a speed or torque sensor, and the power to the motor 6 is therefore adjusted to provide the correct speed or torque output. The power to the motor 6 could compensate for the user power input, for example, if the user power decreases, then motor power increase to maintain the correct speed/torque. The system could therefore balance the power provided by the motor 6 and the user, to provide a consistent torque/speed at the driven wheel. In other examples, the electrical motor could be driven to provide a constant, low level electrical assistance. Various implementations of differing control complexity are available using the auxiliary motor arrangement 2 described herein.

In some embodiments, the power supply 14 comprises a flow battery. The flow battery comprises a reservoir to supply an electrolyte to an electrochemical cell to provide electrical power. At least a portion of the flow battery is detachable from the auxiliary motor arrangement 2 to allow recharging and/or replacement of the electrolyte. In some embodiments, the reservoir may be detachable (i.e. the cell remains fixed to the motor arrangement 2). In other embodiments, both the reservoir and the cell may be detachable as a single unit. Different embodiments of rechargeable/replaceable power supply may be used, e.g. comprising more conventional rechargeable cells.

A charging station (not shown) may be provided to provide charging the battery. The charging station may charge two or more batteries simultaneously. The charging station may comprise a rack to accommodate the plurality of batteries. Rapid swapping of batteries on the bike may be available to minimise waiting/charging time. Where a flow battery is used, the charging station may be configured to replace or recharge the electrolyte in the reservoir/cell.

A quick release mechanism may connect interchangeable batteries/cells to the battery housing 16. This provides a “plug and play” type arrangement.

The present invention allows retrofitting of an auxiliary motor arrangement to a conventional bicycle without any underlying modification thereof. The arrangement therefore converts a conventional bicycle into a power-assisted bicycle. The auxiliary motor arrangement may be easily removed and installed, thus providing a flexible system that can be implemented by the end user at will. This mitigates the need for a user to have a separate electric bicycle and a conventional bicycle. It also allows users to repurpose an existing bicycle to try out electric assistance without needing to invest significant cost.

Additionally, the invention could allow the manufacturer of a bicycle to produce a conventional bicycle and an electrically powered bicycle using the same base bicycle model, thus saving costs. Consumers can be given the option of electric or non-electric versions of the same bike model.

The sprocket arrangement can be attached to the bicycle sprocket easily and quickly, using conventional tools and without specialist skills.

Once installed, this retrofit solution allows fully manual drive, electrical assistance combined with manual drive, or fully electrical drive without requiring modification by the user to achieve each different mode.