GB2620726A

GB2620726A - Improved power train

Info

Publication number: GB2620726A
Application number: GB2208539.3A
Authority: GB
Inventors: Sarna Kris
Original assignee: Individual
Current assignee: Individual
Priority date: 2022-06-10
Filing date: 2022-06-10
Publication date: 2024-01-24
Also published as: GB202208539D0

Abstract

A power train for a pedal-driven vehicle, and comprising a multi-speed gear train which in use can transmit the force generated by a pedal operator’s thrusts to one or more propulsive outlets of the vehicle; characterised in that the power train comprises a motive source of power operatively linked to the gear train, and respectively meshed primary and secondary geared input through to output gear clusters, together with torque sensing means, responsive to an axial force generated on the pedal-driven crankshaft in use to vary the output characteristics of the motive power source and/or the input-to-output ratio of the gear clusters.

Description

IMPROVED POWER TRAIN

Field of the Invention

The invention relates to power trains, and is particularly -although not exclusively -applicable to power trains forming part of the propulsive transmission of a pedal-driven vehicle such as a cycle.

Review of Art Known to the Applicant Power trains suitable for incorporating or adapting into the transmission of a human-powered pedal cycle are well-known and have formed part of the state of this particular art for around or beyond a century. Initially such power trains consisted of three-speed hub-mounted gearboxes such as the Sturmey Archer unit. Subsequently the Derctilleur five-speed style of multiple geared unit took over as a more popular option, with its popularity boosted by professional cycle racing successes. The essential difference between the two types is that the Derailleur physically whips the transmission's chain successively off and back onto one of a range of cogs fixed to the driven back wheel of the cycle; whereas the older Sturmey Archer design operated as an internally contained gear-shaft-shifting "box".

Both, however, needed the cycle rider to positively select a change of gear up or down -neither of them was an automatic shift system responsive to feedback from the road and/or the torque being input into the pedal cranks by the cycle rider.

In recent years this broad state of affairs within the relevant art has changed, in that gearboxes are now available which are not only automatic in operation (i.e. they shift gear up or down in response to feedback rather than requiring the rider to do it) but they are designed and incorporated into the cycle in the region of the rider-driven pedalled cranks, rather than the hub of the driven (usually the rear) wheel of the cycle.

Gearboxes of the kind just referred to do nevertheless have drawbacks and one of them lies in the fact that the multi-speed gear train as such habitually occupies a relatively lengthy area of the volumetric space around or adjoining the pedal-bearing crankshaft region. The present invention seeks to overcome those drawbacks.

Summary of the Invention

In its broadest aspect the invention is embodied in a power train, suitable for incorporating or adapting into the transmission of a pedal-driven vehicle, and comprising a multi-speed gear train which in use can transmit the force generated by a pedal operator's thrusts to one or more propulsive outlets of the vehicle; characterised in that the power train comprises a motive source of power operatively linked to the gear train, and respectively meshed primary and secondary geared input-through-to-output gear clusters, together with torque sensing means, responsive to the axial force generated on the pedal-driven crankshaft in use to vary the output characteristics of the motive power source and/or the input-to-output ratio of the gear clusters.

Brief Description of the Drawings

In the accompanying drawings filed with and forming part of this disclosure: Figure 1 is a perspective view of the electric motor, the primary and secondary geared inputthrough-to-output gear clusters, and the central part of the crankshaft, of a power train embodying the invention, Figure 2 is a schematic illustration of the power train unit; Figure 3, shown in an enlarged scale relative to the previous figures, is a perspective view of a central region of the crankshaft showing the torque sensing pressure washer of the unit; Figures 4 and 5 are, again, perspective views showing respectively the planetary gear drive incorporated into the electric motive power source of the unit (Figure 4) and the planetary gear carrier integrated within one of the gear cluster counter-shafts (Figure 5), Figure 6 is another schematic illustration showing further detail of the operation of the geared transmission; and Figures 7 and 8 highlight pictorially the way the torque sensing mechanism works.

The power train unit shown is only one form the invention might take within its broadest aspect. Variations which yet fall within the scope of the invention will become apparent to the intended skilled addressee of this specification. All such variations are intended to be included within the legally effective and enforceable scope of this application.

Description of the Preferred Embodiment

The power train illustrated, which as stated immediately above is only one form the invention might take within its broadest aspect, is intended to form an integrated supported "mid-drive" for a relatively otherwise conventional road-going cycle. The cycle may be a pedal cycle or it could equally be a power-driven one. In either event, the power train of the present invention is intended to be applicable without inventive thought to, for example, pedal-driven cycles such as those currently known under the designation mountain bike (for recreational purposes) or cargo bikes (i.e. delivery vehicles).

The drawings illustrate a power train embodying the invention and comprising a multi-speed gear train which, in this specific example, incorporates a 13-speed gear box using two primary gears and six secondary gears The same package would allow a 16-speed configuration, this time using three primary gears and five secondary gears, but it will be apparent at once to the reader that other ratio numbers can be settled on once the principles underlying the invention have been absorbed and applied.

The power train incorporates a motive source of power in the form of an electric motor which itself incorporates a planetary gear drive as shown particularly in Figure 4 of the drawings. This is integrated (Figure 5) with a counter-shaft forming one of-in this instance -two gear cluster carrying shafts. The electric motor itself has a single stage speed reducer, and the two respective gear clusters constitute primary and secondary gears in operation as Figure 2 shows schematically and clearly.

A torque-sensing means in the form of a pressure washer (Figure 3) responds to the crankshaft being driven, i.e. rotated by the pedals, once the cycle is in motion, and operates through a force sensing resistor or load cell to function as a notionally trouble-free and neat way of varying the effective input-to-output ratio afforded by the gear clusters as the unit operates. The format illustrated in Figure 3, when assessed in the light of this explanation, will be appreciated as providing an especially low cost high accuracy torque sensing means but others could be varied and/or added if needs be as the invention is developed within its overall aspect. Referring again to the drawings, the selector barrel illustrated rotates in use at the same angular speed as the countershaft (due to the same ratio to planetary gear sets of electric motor speed reducer and planetary shifter respectively) using a common "sun" gear, whilst the relative positions of the selector barrel and countershaft can be changed by rotating the shifter planetary ring gear (see Figures 2; 4; 5 in particular).

The lowest gear of the unit uses a one-way bearing for a direct drive (Figure 2) and this enables the electric motor to be integrated with a single-stage speed reduction. The whole power train, as can clearly be seen from the drawings in total, constitutes an exceptionally compact space-efficient way of incorporating or adapting a multi-speed gear train into the transmission of a pedal-driven vehicle and, whilst the design details may all well be finessed with development and testing, the broad principles which the invention embodies are applicable over the whole range of production units resulting from this disclosure Figures 7 and 8 highlight these virtues of the embodiment described and illustrated in this current disclosure. The key element, which generates an axial thrust force in response to the torque sensed by the unit in response to the crankshaft being driven as the rider rotates the pedals, is the ramp surface shown in Figures 7 and 8 and highlighted in Figure 8 especially. This camming surface is angled (again as Figure 8 emphasises pictorially) and it is the rotary movement of this surface which the force sensing means reacts to in operating the unit.

Finally, whilst the invention has been described and illustrated with reference to a power train for incorporation into a pedal-driven road-going cycle, it could equally well in theory be adapted successfully into the propulsion of for example water craft, hover craft, or the like. The term "pedal-driven vehicle" is to be interpreted broadly in that respect.

Claims

Claims 1 A power train, suitable for incorporating or adapting into the transmission of a pedal-driven vehicle, and comprising a multi-speed gear train which in use can transmit the force generated by a pedal operator's thrusts to one or more propulsive outlets of the vehicle; characterised in that the power train comprises a motive source of power operatively linked to the gear train, and respectively meshed primary and secondary geared input-through-tooutput gear clusters together with torque sensing means, responsive to the axial force generated on the pedal-driven crankshaft in use to vary the output characteristics of the motive power source and/or the input-to-output ratio of the gear clusters 2. An integrated supported bike mid-drive unit having the features described and illustrated in the accompanying drawings.3. Any invention capable of practical realisation and falling within the scope of the inventive concept disclosed herein.