WO2022023774A1

WO2022023774A1 - Electrically- assisted pedal cycles

Info

Publication number: WO2022023774A1
Application number: PCT/GB2021/051986
Authority: WO
Inventors: Linan GONG
Original assignee: Ebike Systems Ltd
Priority date: 2020-07-31
Filing date: 2021-07-30
Publication date: 2022-02-03
Also published as: GB202011968D0; GB2597734A; GB2597734B

Abstract

An electrically-assisted pedal cycle has a pair of pedals that drive a front sprocket. A rear driven wheel is spaced from the pedals and has a hub (100) in which an electrically-assisted drive system is mounted. A rear sprocket (80) is mounted on or adjacent the hub (100) and a chain or belt connects the front and rear sprockets (80). Moving parts (111) of a cadence sensor (111,112) are mounted on a part (13) of the electrically-assisted drive system that rotates with the rear sprocket (80). That rotating part may be a part (13) (e.g. a planet carrier) of an epicyclic gear set (15) that is part of the electrically- assisted drive system, which preferably provides a continuously variable transmission (CVT).

Description

ELECTRICALLY-ASSISTED PEDAL CYCLES

The present invention relates to electrically-assisted pedal cycles.

There are various forms of pedal cycle. One conventional form of pedal cycle is that which is only ever driven by a cyclist applying force to the pedals, such cycles sometimes being referred to as "push bikes". Another more recent form of pedal cycle is the electrically-assisted pedal cycle, commonly now known as “e-Bikes” in which electrical power is used to assist or replace the efforts of the rider. Both conventional pedal cycles and e-Bikes may have two, three or four wheels, and, in some cases, even more. In the present document, the term "pedal cycle" is used to include both conventional pedal cycles and e-Bikes.

As mentioned, in an e-Bike, electrical power is used to assist, or in some cases replace, the efforts of the rider. Accordingly, e-Bikes include means for storing electrical energy, such as batteries, and an electric motor arranged to propel, either in combination with pedal input, or to replace pedal input. The batteries can be recharged by plugging them into a supply of electrical energy, such as an outiet from a mains supply; in some cases, also by recovering energy from motion of the cycle by way of regenerative braking, and in others by generation of electricity in a series hybrid configuration. The principle of regenerative braking will be familiar to those skilled in this field of technology.

As a result, the overall effort usually required by a cyclist to pedal an e- Bike is lower than for a conventional cycle, or absent. e-Bikes can be placed into one of two groups.

The first group is that in which the cycle can provide electrical assistance on demand, at any time, regardless of whether or not the cyclist is pedalling. Cycles in this group can be thought of as being generally equivalent to electric mopeds. The pedal input may be rarely used or only as a “limp home” capability when the battery is discharged. Cycles in the second group only provide electrical assistance when the cyclist is pedalling. These are referred to as "pedelecs". Currentiy, in all European Union countries, including the UK, and many other countries, pedelecs are effectively legally classified as conventional bicycles and so may be ridden without a driving license or insurance, providing electrical assistance ceases at a speed of 25kph (although a separate category of “speed pedelecs” with a speed limitation of 45kph has license and insurance requirements). There are therefore few barriers to owning and operating a pedelec.

In recent years, technical advances have been made to the electromechanical drive arrangements and to the associated energy storage and recovery devices used in e-Bikes. These advances have resulted in e-Bikes that can be operated with greater efficiency, and hence greater ease, by the cyclist.

For all the reasons given above, e-Bikes are becoming increasing popular, all over the world.

By way of background, the reader is referred to our PCT publications WO2010/ 092345, W02017/021715 and W02018/020259, where much information about e-Bikes is provided. There is particular reference to the use of continuously variable transmissions (CVTs) in pedelecs.

Controllers for e-Bikes often require data as to the angular speed or rate of rotation, or cadence, of the pedals at any given time. This is usually effected by a cadence sensor located adjacent the pedals and crankshaft. However, this can expose the cadence sensor to accidental damage and requires both individual fitting and data connection to other parts of the bicycle.

Preferred embodiments of the invention aim to provide e-Bikes with cadence sensors that are generally improved in the foregoing respects.

According to one aspect of the present invention, there is provided an electrically-assisted pedal cycle comprising: a frame; a pair of pedals and crankshaft mounted on the frame; a front sprocket driven by the pedals; a driven wheel spaced from the pedals and crankshaft; an electrically-assisted drive system mounted in the hub of the driven wheel; a rear sprocket mounted on or adjacent the hub of the driven wheel; a chain or belt connecting said front and rear sprockets; and a cadence sensor, at least a part of which is mounted on a part of the electrically-assisted drive system that rotates with the rear sprocket.

In the context of this specification, the term ‘sprocket’ includes both components that are formed with teeth in order to engage a drive chain and components that are otherwise formed to engage a drive belt.

Preferably, said driven wheel is a rear wheel of the cycle.

The electrically-assisted pedal cycle may be a pedelec. Preferably, said drive system includes an epicyclic gear set having a component that is driven by the rear sprocket and the cadence sensor has a part that is mounted for movement with said component.

Preferably, said component is a planet carrier. Preferably, the cadence sensor comprises a plurality of magnetic elements and two or more Hall sensors.

Preferably, said magnetic elements are mounted on said planet carrier.

Preferably, said two or more Hall sensors are mounted on an axle of the driven wheel. Preferably, axle is hollow and electrical cabling to the one or more Hall sensor passes through the axle.

Preferably, the drive system includes an electrical machine that is configured to operate selectively as a generator or a motor and the system further includes a controller that alternately operates the electrical machine as a generator for a first period and then as a motor for a second period, the controller obtaining an indication of torque applied at the rear sprocket as a function of generator output, and then applying power to the motor as a function of the torque indicated.

Preferably, the hub of the driven wheel encloses the drive system and cadence sensor.

The cycle may be a bicycle. Preferably, the drive system provides a continuously variable transmission (CVT).

For a better understanding of the invention, and to show how embodiments of the same may be carried into effect, reference will now be made, by way of example, to the accompanying diagrammatic drawings, in which:

Figure 1 is a side view of a pedelec;

Figure 2 is a sectional view of an electrically-assisted drive system of the pedelec, with an integrated cadence sensor. In the figures, like references denote like or corresponding parts.

It is to be understood that the various features that are described in the following and / or illustrated in the drawings are preferred but not essential. Combinations of features described and/ or illustrated are not considered to be the only possible combinations. Unless stated to the contrary, individual features may be omitted, varied or combined in different combinations, where practical.

Figure 1 shows a pedelec in the form of a bicycle 10. The bicycle 10 is similar to a conventional bicycle in having a steerable wheel 20 at the front and a driveable wheel 30 at the back. The bicycle 10 also has a conventional arrangement of pedals 40 on crank arms 50 that drive a front toothed sprocket 60 (often referred to as a front cog or chainwheel), connected by a chain 70 to a rear sprocket 80, the rear sprocket being mounted co-axially with the rear wheel 30. ITowever, the bicycle 10 differs from a conventional bicycle in that the rear sprocket 80 is not fixedly mounted to a hub 100 of the rear wheel 30 to drive that wheel directly. Instead, the rear sprocket 80 provides a rider’s power input to a drive system that is disposed within the hub 100.

A control housing 90 and a battery housing 92 are fitted to the frame of the bicycle 10. These may be mounted at any convenient location. A handlebar 119 is provided for steering and a throttie twist-grip 120 is optionally provided for controlling electrical power assistance.

In a conventional e-Bike, a cadence sensor 110 is fitted adjacent the pedals 40 and crankshaft (as illustrated in broken lines) and electrically connected to the control housing 90 in order to provide data as to the angular speed or rate of rotation of the pedals 40 at any given time. However, such a cadence sensor 110 is exposed to the elements, susceptible to accidental damage in the event of careless handling of the bicycle 10 and requires electrical connection to the control housing 90.

The illustrated embodiment of the invention aims to provide an improved e-Bike with cadence sensor.

Figure 2 shows one example of the arrangement of rear hub 100 in an e- Bike along the lines of that shown in Figure 1.

The rear hub 100 is connected to drive the rear wheel 30 via spokes 18 or other mechanical connection. The drive to the rear hub 100 itself is provided via a variable combination of physical input via rear sprocket 80 and epicyclic gear set 15 and electrical drive input via an electrical machine comprising stator 5 and rotor 6. Preferably, the drive system provides a continuously variable transmission (CVT). The rear sprocket 80 may typically have a freewheel mechanism, but otherwise is connected to drive planet carrier 13 of the epicyclic gear set 15 in a forward direction, with the planet carrier 13 linked directiy, via the rear sprocket 80, to the forward sprocket 60 and crank 50 system. Thus, the planet carrier 13 has a speed which is directiy and permanently linked to both the positive turning speed of the crankshaft with cranks 50, and a positive torque input from the rider, which may be regarded as a human input branch of the drive system. Both rear sprocket 80 and planet carrier 13 are mounted on bearings for rotation about a rear axle 1 of the e-Bike 10. The planet carrier 13 is shown in block colour in Figure 2.

To provide a cadence sensor within the hub 100, a ring of magnets 111 is attached to the planet carrier 13 for rotation with it and cooperates with fixed Hall effect elements 112 mounted in the axle 1. An axial bore 113 in the axle 1 allows for the passage of cabling 114 to the Hall effect elements 112 and also cabling 115 to the stator 5. A common connector 116 enables connection of the cables 114 and 115 to the e-Bike controller in housing 90.

According to a control algorithm which may be applied in a CVT system, in which a torque input signal induced by any torque input from the human rider via the planet carrier 13 through its interaction with a sun gear mounted on the rotor of the motor is constantly monitored by the controller using an algorithm called Differential Inductive Torque Sensing DITS (see W02017/021715), any positive torque input in combination with a positive planet carrier speed will be considered as positive crank movement. Any negative crank turning speed will lead to disruption of rider’s torque input via the planet carrier 13, and this will lead to reduction of motor current to 2ero, and subsequently standstill of the motor. In case the bike is pushed backwards, the planet carrier 13 will also move backwards with the hub member; in this case, the Hall effect elements 112 will recognize a negative crank speed and will not lead to motor start. In other words, any backwards movement of the planet carrier 13 will be recognized by the sensor elements 112 and will be used as a signal to suppress motor start.

A detailed explanation of the transmission characteristics of the illustrated drive system is not required for the present invention. It is sufficient to understand that drive from pedals 40 is transmitted via cranks 50, front sprocket 60, chain 70, rear sprocket 80 and epicyclic gear set 15 to hub 100 and thus, via spokes 18 or alternative, to the driven rear wheel 30. The e-Bike controller in housing 90 controls operation of the electrical machine 5, 6 to provide electrical assistance to the drive from the pedals 40 in accordance with varying conditions. Throttie 120 on handlebar 119 may afford a degree of user control as to the amount of electrical assistance provided at any time. Although the bicycle 10 is described as a pedelec, it could alternatively (or optionally) provide electrical assistance when the cyclist is not pedalling.

In order to provide control of the e-Bike 10, it is desirable to know the frequency of rotation, or cadence, of the rear sprocket or cog 80 and planet carrier 13 at any given time. To this end, the Hall effect elements 112 respond to passage of the magnets 111. This provides data as to cadence, which is fed to the e-Bike controller in housing 90 via cable 114 and connector 116.

Such a configuration of cadence sensor may be much improved over known e-Bikes. By integrating the cadence sensor into the rear drive system, the sensor is better shielded against heat, moisture, splash water and other negative environmental elements. It is better shielded against vandalising. Less cable may be used, thus facilitating cable routing. It may provide more reliable signal quality. Incorporating the cadence sensor in the overall hub assembly, such that the hub 100 which, in existing designs, may already incorporate a bike speed sensor, encloses the drive system and cadence sensor, and may facilitate fitting and provide a more aesthetically pleasing appearance. In such a case, the drive unit or system may contain all sensors the pedelec system needs to function properly. No external cable routing for sensor system is then necessary. This may be of significant importance to bike sharing businesses.

It may be noted that the electrical machine 5,6 may be configured to operate selectively as a generator or a motor, with a controller that alternately operates the electrical machine as a generator for a first period and then as a motor for a second period, the controller monitoring generator output to infer or sense torque applied at the rear sprocket 80, and then applying power to the motor as a function of the inferred or sensed torque. The reader is referred to our publication WO 2017/021715 for further details of such arrangements.

Although, in the illustrated embodiment, the driven wheel is a rear wheel, which is typical, the driven wheel could alternatively be a front wheel.

The term ‘driven wheel’ is used in this specification to refer to a wheel that is driven in rotation by power applied via pedals and/ or motor. Such a wheel may also be referred to as a ‘driving wheel’, as it applies drive to the surface on which the cycle travels.

The reader's attention is directed to all and any priority documents identified in connection with this application and to all and any papers and documents which are filed concurrentiy with or previous to this specification in connection with this application and which are open to public inspection with this specification, and the contents of all such papers and documents are incorporated herein by reference.

In this specification, the verb "comprise" has its normal dictionary meaning, to denote non-exclusive inclusion. That is, use of the word "comprise" (or any of its derivatives) to include one feature or more, does not exclude the possibility of also including further features. The word “preferable” (or any of its derivatives) indicates one feature or more that is preferred but not essential.

All or any of the features disclosed in this specification (including any accompanying claims, abstract and drawings), and/ or all or any of the steps of any method or process so disclosed, may be combined in any combination, except combinations where at least some of such features and/ or steps are mutually exclusive.

Each feature disclosed in this specification (including any accompanying claims, abstract and drawings), may be replaced by alternative features serving the same, equivalent or similar purpose, unless expressly stated otherwise. Thus, unless expressly stated otherwise, each feature disclosed is one example only of a generic series of equivalent or similar features.

The invention is not restricted to the details of the foregoing embodiment(s). The invention extends to any novel one, or any novel combination, of the features disclosed in this specification (including any accompanying claims, abstract and drawings), or to any novel one, or any novel combination, of the steps of any method or process so disclosed.

Claims

1. An electrically-assisted pedal cycle comprising: a frame; a pair of pedals and crankshaft mounted on the frame; a front sprocket driven by the pedals; a driven wheel spaced from the pedals and crankshaft; an electrically-assisted drive system mounted in the hub of the driven wheel; a rear sprocket mounted on or adjacent the hub of the driven wheel; a chain or belt connecting said front and rear sprockets; and a cadence sensor, at least a part of which is mounted on a part of the electrically-assisted drive system that rotates with the rear sprocket.

2. An electrically-assisted pedal cycle according to claim 1, wherein said driven wheel is a rear wheel of the cycle.

3. An electrically-assisted pedal cycle according to claim 1 or 2, being a pedelec.

4. An electrically-assisted pedal cycle according to claim 1, 2 or 3, wherein said drive system includes an epicyclic gear set having a component that is driven by the rear sprocket and the cadence sensor has a part that is mounted for movement with said component.

5. An electrically-assisted pedal cycle according to claim 4, wherein said component is a planet carrier.

6. An electrically-assisted pedal cycle according to any of the preceding claims, wherein the cadence sensor comprises a plurality of magnetic elements and two or more Hall sensors.

7. An electrically-assisted pedal cycle according to claims 5 and 6, wherein said magnetic elements are mounted on said planet carrier.

8. An electrically-assisted pedal cycle according to claim 6 or 7, wherein said two or more Hall sensors are mounted on an axle of the driven wheel.

9. An electrically-assisted pedal cycle according to claim 8, wherein said axle is hollow and electrical cabling to the one or more Hall sensor passes through the axle.

10. An electrically-assisted pedal cycle according to any of the preceding claims, wherein the drive system includes an electrical machine that is configured to operate selectively as a generator or a motor and the system further includes a controller that alternately operates the electrical machine as a generator for a first period and then as a motor for a second period, the controller monitoring generator output to infer torque applied at the rear sprocket, and then applying power to the motor as a function of the inferred torque.

11. An electrically-assisted pedal cycle according to any of the preceding claims, wherein the hub of the driven wheel encloses the drive system and cadence sensor.

12. An electrically-assisted pedal cycle according to any of the preceding claims, wherein the cycle is a bicycle.

13. An electrically-assisted pedal cycle according to any of the preceding claims, wherein the drive system provides a continuously variable transmission

(CVT).

14. An electrically-assisted pedal cycle substantially as hereinbefore described with reference to the accompanying drawings.