Electrically-assisted pedal cycles

Abstract

A drive system for an electrically-assisted pedal cycle 10 comprises a pedal input 80 that rotates about an input axis 1; an output 100 that rotates about an output axis 1 to drive a wheel; an electri

Description

[0001] The present invention relates to electrically-assisted pedal cycles.

[0002] Electrically-assisted pedal cycles are now in common use, and typically referred to as an 'eBike', in which electrical power is used to assist or replace the efforts of the rider. Like conventional pedal cycles, eBikes 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 eBikes.

[0003] eBikes may be placed generally 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. eBikes in the second group only provide electrical assistance when the cyclist is pedalling. These are referred to as 'pedelecs'.

[0004] In recent years, technical advances have been made to electromechanical drive arrangements and to associated energy storage and recovery devices used in eBikes. These advances have resulted in eBikes that can be operated with greater efficiency, and hence greater ease, by the cyclist.

[0005] By way of background, the reader is referred to our PCT publications WO2010 / 092345, W02017 / 021715 and W02018 / 020259, where much information about eBikes is provided. There is particular reference to the use of continuously variable transmissions (CVTs) in pedelecs.

[0006] The reader is further referred to our PCT publication WO2023 / 170394, which discloses a CVT drive system for an electrically-assisted pedal cycle, in which drive is switched over from electrical assistance to manual pedalling for higher speeds, and back again, in a controlled and smooth manner. This is of particular relevance in territories where there is a maximum speed limit for electrical assistance - 25 kph in many countries. Above this or any other desired speed, the rider needs to be able to pedal unassisted, but at a practical pedal cadence (rotational speed of the pedals).

[0007] Whilst a system as disclosed in WO2023 / 170394 has proved very practical, there are occasions when a higher rider assistance level than a regular CVT system may be desirable. For example, when climbing a steep hill.

[0008] Preferred embodiments of the present invention aim to provide electrically-assisted pedal cycles and drive systems for them, which are improved in this respect. Embodiments of the invention may be particularly effective in the use of a 3-branch power combining epicyclic transmission (two inputs and one output) in a CVT transmission.

[0009] According to one aspect of the present invention, there is provided a drive system for an electrically-assisted pedal cycle, the system comprising: an input that, in use, receives drive from a pedal of the cycle and rotates about an input axis; an output that, in use, rotates about an output axis to provide drive to a driven wheel of the cycle; an electrical machine that, in use, provides motor drive to said output; and a drive train that, in use, receives drive from the electrical machine and the pedal and transmits drive to said output: wherein the drive train is operable in one mode to provide a continually variable transmission (CVT) by which pedal cadence is controlled by the electrical machine; the drive train is operable in another mode to provide output drive both from said pedal and said electrical machine in parallel; and the drive system further comprises a mode selector that is operable to select said modes.

[0010] Preferably: said one mode is a second mode; said another mode is a third mode; between cycle speeds of 0 and VI, where Vl>0, the drive train is operable in a first mode to provide output drive only from said pedal; at cycle speeds greater than VI, the drive train is operable in said second mode to provide a continually variable transmission (CVT); and the mode selector is operable to select said first, second or third mode.

[0011] Preferably, above a cycle speed of V2, the drive train is operable in a fourth mode to disengage drive from the electrical machine to provide output drive only from said pedal; and the mode selector is operable to select said first, second, third or fourth mode.

[0012] Preferably, above a cycle speed of V2, which is greater than VI, the drive train is operable in said fourth mode to disengage drive from the electrical machine to provide output drive only from said pedal, with a gear ratio that is higher than that provided below a cycle speed of VI.

[0013] Preferably, the drive train comprises an epicyclic gear set having a first input connected to the electrical machine and a second input connected to the pedal.

[0014] Preferably, the epicyclic gear set is a dual epicyclic gear set having first and second stages, the first stage comprising a first sun, planets and annulus and the second stage comprising a second sun, planets and annulus.

[0015] Preferably, the mode selector is operable to connect and disconnect said first and second stages.

[0016] Preferably, the mode selector is operable to connect said first and second stages when the drive train operates in said one mode or said second mode to provide a continually variable transmission (CVT).

[0017] Preferably, the mode selector is operable to disconnect said first and second stages when the drive train does not operate in said one mode or said second mode to provide a continually variable transmission (CVT).

[0018] Preferably, when the drive train operates in said another mode or said third mode to provide output drive both from said pedal and said electrical machine in parallel, the mode selector is operable to connect said first planet carrier with a one-way clutch that, in use, is fixed with respect to the cycle.

[0019] Preferably, when the drive train operates in said fourth mode to provide output drive only from said pedal, the mode selector is operable to connect said second planet carrier with a one-way clutch that, in use, is fixed with respect to the cycle.

[0020] The mode selector may comprise a moveable mechanical link.

[0021] The mode selector may be operable manually.

[0022] The mode selector may be operable automatically in response to sensed parameters.

[0023] Said sensed parameters may include cycle speed and / or incline.

[0024] Said input axis and said output axis may be the same axis.

[0025] Said input and output axes may be spaced from one another.

[0026] In another aspect, the invention provides a drive system for an electrically-assisted pedal cycle, the system comprising: an input that, in use, receives drive from a pedal of the cycle and rotates about an input axis; an output that, in use, rotates about an output axis to provide drive to a driven wheel of the cycle; an electrical machine that, in use, provides motor drive to said output; and a drive train that, in use, receives drive from the electrical machine and the pedal and transmits drive to said output: wherein: the drive train is operable in one mode to provide a continually variable transmission (CVT) by which pedal cadence is controlled by the electrical machine; above a cycle speed of V2, the drive train is operable in another mode to disengage drive from the electrical machine to provide output drive only from said pedal, with a gear ratio between said input and output that is higher than that upon startup of the cycle; said input axis is an axis of rotation of a pedal crankshaft; and the electrical machine and drive train are offset with respect to said input axis.

[0027] Such a drive system may further comprise a second electrical machine that, in use, provides motor drive to said output.

[0028] The drive train may be operable in a further mode to provide output drive only from said second electrical machine.

[0029] The drive train may comprise a single epicyclic gear set.

[0030] A drive system as above may further comprise a pair of gears that are configured to be locked together to provide a gear ratio between said input and output that is higher than that upon startup of the cycle.

[0031] Such drive systems may include, in any practical combination, any of the features of the preceding aspects of the invention and / or as disclosed in the following description and / or accompanying drawings.

[0032] The invention extends to an electrically-assisted pedal cycle having a drive system according to any of the preceding aspects of the invention.

[0033] The electrically-assisted pedal cycle may be a pedelec in which electrical assistance is provided only when the cyclist is pedalling.

[0034] Electrical assistance may be available both when the cyclist is pedalling and also when the cyclist is not pedalling.

[0035] A throttle control may be provided, by which a cyclist can apply or superimpose a desired amount of electrical assistance.

[0036] The drive train may be located within a hub of the driven wheel.

[0037] The drive train may be located around or adjacent a crankshaft connecting two pedal cranks.

[0038] The input axis of the drive train may be the axis of rotation of the crankshaft and the output axis of the drive train parallel to but spaced from the input axis.

[0039] The invention extends to a method of operating an electrically-assisted pedal cycle according to any of the preceding aspects of the invention, comprising the steps of providing motor drive to the driven wheel of the cycle by the or each said electrical machine and providing pedal drive to the driven wheel of the cycle, via said drive train.

[0040] 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:

[0041] Figure 1 is a side view of an electrically-assisted pedal cycle;

[0042] Figure 2 is a diagrammatic view of a drive system for the electrically- assisted pedal cycle, with the drive system in a second mode;

[0043] Figure 3 is a diagrammatic view of the drive system in a first mode;

[0044] Figure 4 is a diagrammatic view of the drive system in a third mode;

[0045] Figure 5 is a diagrammatic view of the drive system in a fourth mode;

[0046] Figure 6 is a graph to show pedal cadence (RPM) against cycle speed;

[0047] Figure 7 is a view similar to Figure 2, with a compound epicyclic gear;

[0048] Figure 8 is a view similar to Figure 2, but showing a mid-drive configuration;

[0049] Figure 9 is a diagrammatic illustration of input and output axes that are not coaxial;

[0050] Figure 10 is a diagrammatic view of a mid-drive drive system that is similar to those of the preceding figures, but with much of the drive system off-axis, with the drive system in a second mode;

[0051] Figures 11a, lib and 11c illustrate a mode selector of the drive system of Figure 10, in different positions;

[0052] Figure 12 is a diagrammatic view of the drive system of Figure 10 in a first mode;

[0053] Figure 13 is a diagrammatic view of the drive system of Figure 10 in a third mode;

[0054] Figure 14 is a diagrammatic view of the drive system of Figure 10 in a fourth mode;

[0055] Figure 15 illustrates a drive system that provides a CVT mode with high gear pedal-only mode above a limit speed and with a direct motor drive option, with much of the drive system off-axis;

[0056] Figure 16 is a diagrammatic view of the drive system of Figure 15 in a first mode;

[0057] Figure 17 is a diagrammatic view of the drive system of Figure 15 in a second mode;

[0058] Figure 18 is a diagrammatic view of the drive system of Figure 15 in a third mode; and

[0059] Figure 19 is a diagrammatic view of the drive system of Figure 15 in a fourth mode

[0060] Figure 20 illustrates a drive system that provides a CVT mode with high gear pedal-only mode above a limit speed and with a direct motor drive option, with much of the drive system off-axis, with a single epicyclic gear set;

[0061] Figure 21 is a diagrammatic view of the drive system of Figure 20 in a first mode;

[0062] Figure 22 is a diagrammatic view of the drive system of Figure 20 in a second mode;

[0063] Figure 23 is a diagrammatic view of the drive system of Figure 20 in a third mode; and

[0064] Figure 24 is a diagrammatic view of the drive system of Figure 20 in a fourth mode.

[0065] In the figures, like references denote like or corresponding parts.

[0066] 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.

[0067] Figure 1 shows an electrically-assisted pedal cycle 10. The cycle 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 cycle 10 also has a conventional arrangement of pedals 40 on crank arms 50 that drive a front toothed cog 60 connected by a chain or toothed belt 70 to a rear sprocket 80, the rear sprocket being mounted co-axially with the rear wheel 30. However, the cycle 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.

[0068] A drive system is mounted within the hub 100 and is described as follows, with reference to Figure 2. The drive system provides a drive train that receives drive from an electrical machine and the pedals 40 and transmits drive to an output. For ease of explanation, the hub 100 is referred to in the following as an outer hub 100 and provides the output of the drive system. The outer hub 100 is typically connected to the outer part of the rear wheel 30 by spokes, or by any other connection, to provide drive to the rear wheel 30.

[0069] It will be noted that, for ease of explanation, the diagrammatic view of Figure 2 (and others) shows just an upper part of the drive system with multiple planets, arranged around the axis of a central axle 1 fixed to the cycle frame. Typically, the drive system is arranged symmetrically around the axis of the central axle 1.

[0070] As mentioned above, the sprocket 80 is not connected directly to the outer hub 100, as would be the case with a regular cycle. Instead, it is connected to an inner hub 2 that is mounted on bearings (not shown) for rotation about fixed axle 1, which is secured to the cycle frame. The sprocket 80 preferably incorporates a freewheel mechanism, as found on many regular cycles. The outer hub 100 is of generally cylindrical shape and is mounted at a first end on the inner hub 2, via a first passive one-way clutch KI. An opposite end of the outer hub 100 is mounted on the axle 1 by way of one or more bearings. The outer hub 100 and the inner hub 2 are rotatable about a common axis, which is the axis of the axle 1. The purpose of the one-way clutch KI is to prevent the pedal input 80 from rotating faster than the output at the outer hub 100. The one-way clutch KI could be made up of a bearing and a separate clutch.

[0071] An electrical machine comprises a stator 5 that is fixedly mounted on the axle 1 and a rotor 6 that is mounted on a shaft 7 that is mounted on suitable bearings (not shown) for rotation about the axle 1. A first stage EPl of a dual epicyclic gear set EPl, EP2 connects the shaft 7 to the outer hub 100. The axle 1 is hollow and receives cables to connect a controller 91 (and a battery 93) to components of the drive system.

[0072] The dual epicyclic gear set EPl, EP2 affords a high gear ratio and a small packaging space for a given torque capacity. The first epicyclic stage EPl comprises first sun 21a, planets 22a, planet carrier 23a and annulus or ring 24a. The first annulus or ring 24a is rotationally solid with the outer hub 100. There may be two, three or more planets 22a.

[0073] The second epicyclic stage EP2 comprises second sun 21b, planets 22b, planet carrier 23b and annulus or ring 24b. The second sun 21b is connected for rotation with the outer hub 100. There may be two, three or more planets 22b.

[0074] Second and third passive one-way clutches K2 and K3 are mounted on the axle 1.

[0075] In a somewhat similar example that is disclosed in our above-mentioned WO2023 / 170394, epicyclic gear trains EPl and EP2 are permanently connected - for example, by a link denoted diagrammatically in the present Figure 2 by broken line 120, which connects first planet carrier 23a with second ring 24b.

[0076] However, in the present embodiment of Figure 2, there is no such permanent link 120. Instead, a selectable link between first planet carrier 23a and second ring 24b is provided by way of a three-position mode selector 110 comprising a moveable mechanical link that is moveable left and right as seen in Figure 2, to provide a selection between four modes - Mode 1, Mode 2, Mode 3, Mode 4.

[0077] Figures 2, 3, 4 and 5 show respective modes of operation of the drive train; for each mode, only the active components of the drive train are shown in the respective figure.

[0078] Figure 3 illustrates Mode 1 of the drive train, with selector 110 in a central or left position. This provides pedal-only drive. In use, pedal drive is transmitted to rear sprocket 80, which drives inner hub 2, which in turn drives outer hub 100 and thus the rear wheel 30 of the cycle 10. There is no electrical assistance from the motor 5,6. Mode 1 may be selected to launch the cycle from rest, with a lowest internal gear ratio (e.g. 1:1) between inner hub 2 and outer hub 100.

[0079] Figure 2 illustrates Mode 2 of the drive train, with selector 110 in a central position. The mode selector 110 connects engagement teeth 111 on the first planet carrier 23a with engagement teeth 113 on the second ring 24b. Thus, the diagrammatic link 120 is established.

[0080] In Mode 2 use, pedal drive is transmitted to rear sprocket 80 that is connected to second planet carrier 23b to drive it in rotation. Planet gears 22b transmit drive to sun gear 21b that rotates with outer hub 100. Electrical assistance from the rotor 6 is supplied via the first sun 21a, planets 22a and ring 24a. The speed of the electric motor can be varied in relation to the hub speed to continuously alter the rider cadence. Thus, EPl and EP2 afford a continuously variable transmission (CVT), in a manner similar to that disclosed in our WO2023 / 170394.

[0081] Figure 4 illustrates Mode 3 of the drive train, with selector 110 in a left position. The mode selector 110 connects engagement teeth 111 on the first planet carrier 23a with engagement teeth 112 on a third one-way clutch K3 that is mounted on the axle 1. There is no connection between engagement teeth 111 and 113. The diagrammatic link 120 is broken.

[0082] This holds the first planet carrier 23a in a fixed position such that drive from the motor 5,6 is transmitted directly to the outer hub 100 via EPl. At the same time, as in Mode 1, pedal drive is transmitted to the outer hub 100 via rear sprocket 80, inner hub 2 and first one-way clutch KI. Thus, Mode 3 is a drive mode that is common to many eBikes, namely a Parallel Hybrid (PH) mode.

[0083] Figure 5 illustrates Mode 4 of the drive train, with selector 110 in a right position. The mode selector 110 connects engagement teeth 113 on the second ring with engagement teeth 114 on the second one-way clutch K2 that is mounted on the axle 1. There is no connection between engagement teeth 111 and 113. The diagrammatic link 120 is broken.

[0084] This holds the second ring 24b in a fixed position such that pedal torque is transmitted to the outer hub 100 via EP2. This enables pedal-only drive but, with the pedal torque now being transmitted through EP2, the gearing between inner hub 2 and outer hub 100 is now much higher. This facilitates pedal drive at higher speeds - for example, greater than 25 km / h - with a pedal cadence that is achievable by the rider.

[0085] Figure 6 illustrates the four modes of operation.

[0086] Firstly, the drive system is described in 'Launch' mode - that is, Mode 1 as shown in Figure 3.

[0087] In Figure 6, at the origin (0,0) the rider begins to pedal and the cycle begins to move. Up to speed VI, power is provided solely by the rider. This is represented by line portion 41 that, in this example, represents a lowest internal gear ratio of the drive of 1:1. If no electrical assistance were provided, the behaviour of the drive system would continue along line portion 41b, which is an extension of line portion 41.

[0088] Now, the drive system is described in CVT mode - that is, Mode 2 as shown in Figure 2.

[0089] A line comprising four portions 41, 42, 43 and 44 shows the relationship between cadence (RPM) of pedals 40 and linear speed (kph) of cycle 10. The behaviour changes at bicycle speeds VI and V2 that, in this example, are around 3 kph and 25 kph respectively but, in principle, could be any appropriate speeds.

[0090] Referring to solid line 42 in Figure 6, at speed VI, with a pedal cadence of around 28 rpm, electrical assistance is introduced and the pedal cadence remains around 28 rpm until the linear speed of the bicycle reaches 5 kph. The pedal cadence then increases steadily up to about 50 rpm at about 8 kph. Thereafter, as long as pedalling continues with sufficient torque, pedal cadence continues to increase up to speed V2, with only a gradual change in pedal cadence from about 8 kph to about 23 kph, as indicated by line portion 42, which is controlled by controlling the speed of the electric motor 5,6. Thus, line portion 42 indicates that the drive system is providing a continuously variable transmission (CVT) where the ratio between rider cadence and bike speed varies continuously.

[0091] As speed V2 is approached, electrical assistance diminishes and pedal cadence increases, as represented by line portion 43.

[0092] Now, the drive system is described in High-Speed Pedal-Only mode -that is, Mode 4 as shown in Figure 5.

[0093] At speed V2 (which is 25 kph with a pedal cadence of around 70 rpm in this example), electrical assistance ceases and any further increase in speed is effected by the rider continuing to pedal at an increased cadence, as indicated by line portion 44. The gradient of line portion 44 indicates a highest internal gear ratio of the drive of around 3.5:1 (in this example). Line portion 44a indicates the same ratio, extrapolated back to the origin (0, 0). As the rider is now pedalling with an increased internal gear ratio, a practical pedal cadence can be achieved.

[0094] Line 44, 44a indicates the ratio line with clutch K2 closed. Here, the speed of the rear sprocket 80 and inner hub 2 is equal to the speed of the wheel 30 and outer hub 100, divided by (1+EP2R), where EP2R is the gear ratio of the second epicyclic gear EP2. The ratio EP2R is defined by the absolute value of the ratio of the speeds of sun gear 21b to ring gear 24b when the planet carrier 23b is held stationary (not rotating)..

[0095] As mentioned, there are occasions when a higher rider assistance level from a CVT system may be desirable. For example, when climbing a hill.

[0096] Accordingly, the drive system is now described in Parallel Hybrid (PH) mode - that is, Mode 3 as shown in Figure 4.

[0097] Chain-dot line portion 42a indicates electrical assistance by the motor 5,6, in parallel with pedal drive. Line portion 42a is superposed upon line portion 41b, indicating that the motor 5,6 is applying torque while operating along line 41b, the ratio line of clutch KI closed and, with a lowest internal gear ratio of the drive of 1:1, the speed of rear sprocket 80 and inner hub 2 will correspond to the speed of wheel 30 and outer hub 100.

[0098] Drive in PH mode continues until a speed of about 7 kph, pedal cadence of about 65 rpm, at which point it is deselected and drive continues in Mode 2 (CVT), as indicated by chain-dot line 42b. CVT drive may then continue for as long as desired below cycle speed V2. Above V2, Mode 4 is automatically selected - that is, high-speed pedal-only mode. If at any time the cycle speed decreases due to insufficient torque - e.g. when encountering a steep hill -Mode 3 may be selected to apply both pedal torque and motor torque, in Parallel Hybrid mode.

[0099] Thus, the illustrated examples provide the facility of switching between four different modes. The first mode entails pedal-only drive in low gear, which might be suitable for launching the cycle from rest - or may be engaged at any time, if desired. The second mode provides the convenience of a continuously variable transmission (CVT). The third mode provides a parallel hybrid drive, where additional pedal drive may be employed to assist electrical drive. The fourth mode again entails pedal-only drive, but in relatively higher gear, suitable for high speeds.

[0100] This provides considerable flexibility of available drive options, to suit varying conditions.

[0101] The mode selector 100 may be operated in various different ways. It may be operated manually - e.g. by a pushbutton. Alternatively or additionally, it may be operated automatically - for example, in response to the output of an inclinometer 33, where a significant incline is detected. It may be operated automatically in response to a detected speed - for example, greater than 25 km / h. To this end, a speed sensor 31 may be provided.

[0102] Manual and / or automatic mode selection may be adopted in all or any of the examples disclosed in the present specification and drawings. To this end, one or more sensor such as speed sensor 31, inclinometer 33 and torque sensor TS (as in Figure 10, mentioned below) may provide one or more output signal to one or more control device such as controller 91, for example. A control device such as controller 91 may also respond to rider-selected settings.

[0103] The drive system shown in Figure 7 operates in a similar manner to the system of Figure 2 and like references denote like or corresponding parts. However, in Figure 7, EPl is a compound epicyclic gear, having one set of planets 22a and another set of planets 222a, mounted on a common shaft that is driven by planet carrier23a. The planets 22a engage with the first sun 21a and the planets 222a engage with the first ring 24a. This arrangement provides higher gearing in a relatively small space and significantly reduce motor torque requirements while increasing motor speed requirements. Otherwise, the system of Figure 7 operates as previously described.

[0104] The drive system shown in Figure 8 operates in a similar manner to the system of Figure 2 and like references denote like or corresponding parts. However, the Figure 8 variant is configured for use as a central or mid-drive location, around a crankshaft 150 connecting two pedal cranks 50.

[0105] Drive from pedals 40 is transmitted to planet carrier 23b which, in this case, is secured to shaft 150 that is driven in rotation with pedal cranks 50. Shaft 150 therefore provides the input, from pedals 40.

[0106] The stator 5 of motor 5, 6 is mounted to a housing 130 that is secured to a frame of the cycle at 140. The housing 130 has bearings 101 at one end, which engage with the shaft 150, and bearings 103 that engage at the other end with an output member 100 that is connected to annulus or ring gear 24a. The output member 100 is mounted on bearings 102 that engage the shaft 150. The output member 100 and the shaft 150 are rotatable about a common axis, which is the axis of rotation of the pedal cranks 50. The output member 100 is also connected to chain ring or wheel 60, from which drive is transmitted to a driven wheel, which would typically be a rear wheel 30 but could be a front wheel 20.

[0107] The rotor 6 of motor 5, 6 is mounted on shaft 7 that is mounted in turn on suitable bearings (not shown) for rotation with respect to the housing 130.

[0108] In use, input from the pedal cranks 50 is applied to planet carrier 23b. Motor drive is provided to sun gear 21a. Drive from output member 100 is transmitted to a driven wheel via chain ring or wheel 60 that connects to a drive sprocket on the driven wheel, typically via a freewheel mechanism. Whilst a chain drive is most common, other configurations such as belt drive or drive shaft are possible.

[0109] With like references denoting like or corresponding parts, including passive one-way clutches KI, K2, K3, it will be understood that the drive system shown in Figure 8 operates in a similar manner to the system of Figure 2. Passive one-way clutch K7 allows the rider to stop pedalling at any time.

[0110] In the Figure 8 configuration, the gear ratio of the epicyclic gear sets may be different to that in a rear drive configuration.

[0111] In the mid-drive configuration illustrated in Figure 8, whilst the axis of rotation of the chain ring or wheel (or cog) 60 is the same as the axis of rotation of the crankshaft 150, it may be different. This may facilitate a preferred use of space in the drive system.

[0112] Figure 9 illustrates diagrammatically such an arrangement. Drive from chain ring or wheel (or cog) 60 is transmitted to a driven cog or sprocket 80 on a driven (typically rear) wheel, by means of a chain or belt 70 that passes around idler gears or pulleys 71, 72, thereby passing around the axis of rotation of the crankshaft 150, from which the axis of rotation of the chain ring or wheel 60 is spaced. The axes of rotation of the chain ring or wheel 60 and the crankshaft 150 will typically be parallel.

[0113] In order to make efficient use of space, especially in a mid-drive arrangement, the drive system may have a drive train that is off-axis - that is to say, not arranged symmetrically around a central axis that is typically that of a crankshaft such as 150. Such alternatives are shown diagrammatically in Figures 10 to 14.

[0114] Figure 10 illustrates a drive system that is functionally similar to those shown in Figures 1 to 8 and described above and like reference numerals denote like or corresponding parts. However, in Figure 10, much of the drive train is off-axis. Crankshaft 150, with pedals 50, affords an input axis about which the crankshaft 150 rotates. Output member 100, along with drive wheel, ring or cog 60, rotates about an output axis that is the same as the input axis, although it could be different.

[0115] Rotor 5 and epicyclic gear stages EPl and EP 2 are mounted for rotation about an offset axle and axis A, which is spaced from the input / output axis and preferably parallel to it. Axle A is fixed with respect to housing 130.

[0116] As before, epicyclic gear stage EPl comprises first sun 21a, planets 22a, planet carrier 23a and ring 24a. Ring 24a is connected to output member 100 via an output gear 27.

[0117] Likewise, second epicyclic gear stage EP2 comprises second sun 21b, planets 22b, planet carrier 23b and ring 24b. Planet carrier 23b is connected to input shaft 150 via an input gear 28.

[0118] Figure 10 illustrates a torque sensor TS, to which controller 91 may respond.

[0119] In Figure 10, selector 110 engages selectively with engagement teeth 111 and 113 that are connected to the first planet carrier 23a and the second ring 24b respectively. As compared to the Figure 2 example, a single passive one way clutch K5 with engagement teeth 115 replaces clutches K2 and K3 with engagement teeth 112 and 114.

[0120] Since the various modes of operation have already been described with reference to Figures 1 to 8, they are not repeated in detail. However, in summary, they are as follows.

[0121] Figure 11a shows selector 110 in a position for Modes 1 and 2. First planet carrier 23a and second ring 24b are connected via engagement teeth 111 and 113 respectively. Thus, the first and second epicyclic gear stages EPl and EP2 are connected.

[0122] Figure lib shows selector 110 in a position for Mode 3. First planet carrier 23a is connected to the one-way clutch K5. The first and second epicyclic gear stages EPl and EP2 are not connected.

[0123] Figure 11c shows selector 110 in a position for Mode 4. Second ring 24b is connected to the one-way clutch K5. The first and second epicyclic gear stages EPl and EP2 are not connected.

[0124] Figures 12, 10, 13 and 14 illustrate those parts of the drive system that are operative for the respective Modes 1, 2, 3 and 4 - analogous to Figures 3, 2, 4 and 5 respectively.

[0125] Figure 12 illustrates Mode 1 of the drive train, with selector 110 in the position of Figure 11a. This provides pedal-only drive. In use, pedal drive is transmitted from crankshaft 150 directly to drive wheel, ring or cog 60, which in turn drives rear sprocket 80. There is no electrical assistance from the motor 5,6. As before, Mode 1 may be selected to launch the cycle from rest, with a lowest gear ratio.

[0126] Figure 10 illustrates Mode 2 of the drive train, with selector 110 in the position of Figure 11a. Epicyclic gear stages EPl and EP2 are connected and afford a continuously variable transmission (CVT), in a manner similar to that described above with reference to Figure 2.

[0127] Figure 13 illustrates Mode 3 of the drive train, with selector 110 in the position of Figure lib. There is no connection between epicyclic gear stages EPl and EP2. Drive is transmitted to the output member 100 from both pedals 50 and motor 5, 6. Thus, in a manner similar to that described above with reference to Figure 4, Mode 3 is a Parallel Hybrid (PH) mode.

[0128] Figure 14 illustrates Mode 4 of the drive train, with selector 110 in the position of Figure 11c. There is no electrical drive assistance. In a manner similar to that described above with reference to Figure 5, this enables pedal-only drive but, with the pedal torque now being transmitted through EP2, the gearing between inner hub 2 and output member 100 is now much higher. This facilitates pedal drive at higher speeds - for example, greater than 25 km / h -with a pedal cadence that is achievable by the rider.

[0129] The off-axis mid-drive system that is illustrated in Figures 15 to 19 provides a CVT mode with high gear pedal-only mode above a limit speed and also a direct motor drive option by way of a second electrical machine configured in motor mode.

[0130] Figure 15 is generally similar to Figure 10, like reference numerals continuing to denote like or corresponding parts. One difference in Figure 15 is that selector 110 is operative to connect only with engagement teeth 115, connected to clutch K5, which could be either one-way or two-ways, and engagement teeth 113, connected to second ring 24b. First ring 24a is permanently connected to second sun 21b. Drive from motor 5,6 to first sun 21a is via one-way clutch K6.

[0131] Another difference in Figure 15 is the provision of the second electric motor with stator 206 and rotor 205. When activated, this provides a direct drive to the output member 100, via output gear 208 and clutch KI. This direct drive may provide direct drive exclusively, or provide additional support - e.g. for acceleration and on steep hills.

[0132] Figures 16 to 19 illustrate those parts of the drive system that are operative for respective drive modes.

[0133] Figure 16 is similar to Figure 12, illustrating a first mode of the drive train, which provides pedal-only drive. In use, pedal drive is transmitted from crankshaft 150 directly to drive wheel, ring or cog 60, which in turn drives rear sprocket 80. There is no electrical assistance from either motor 5,6 or second motor 205, 206. As before, this first mode may be selected to launch the cycle from rest, with a lowest gear ratio between crankshaft input 150 and output member 100.

[0134] Figure 17 is similar to Figure 10, illustrating a second mode of the drive train. As noted above, epicyclic gear stages EPl and EP2 are connected and afford a continuously variable transmission (CVT), in a manner similar to that described above with reference to Figure 2. Selector 110 provides no connection between engagement teeth 113 and 115.

[0135] Figure 18 illustrates a third mode of the drive train, where the first motor 5, 6 is not activated and no drive need be provided via the pedals 50 and crankshaft 150. In this mode, a direct motor drive is provided by the second motor 205, 206, but this can alternatively be used in combination with the first motor 5,6 (which controls the pedal cadence) in all modes in which it is legal to aid the driver (e.g. below the speed limit). The control system could also be set up so that the rider may control the second motor output torque by way of a throttle control.

[0136] Figure 19 is similar to Figure 14 and illustrates a fourth mode of the drive train, with selector 110 connecting engagement teeth 113 and 115 that effectively connects the second ring 24b with one-way clutch K5. There is no electrical drive assistance. In a manner similar to that described above with reference to Figure 5, this enables pedal-only drive but, with the pedal torque now being transmitted through EP2, the gearing between pedals 50 and output member 100 is now much higher. This facilitates pedal drive at higher speeds -for example, greater than 25 km / h - with a pedal cadence that is achievable by the rider. The one-way clutch K6 allows decoupling the unpowered first (variator) motor 5,6 from the rest of the drive, therefore preventing the drive from driving the motor 5,6 and causing a motor overspeed condition.

[0137] The off-axis mid-drive system that is illustrated in Figures 20 to 24 provides a CVT mode with high gear pedal-only mode above a limit speed and also a direct motor drive option by way of a second electrical machine configured in motor mode. In these respects, the system of Figures 20 to 24 is similar to that of Figures 15 to 19. However, the system of Figures 20 to 24 is realised with only a single epicyclic gear set EPl.

[0138] Like reference numerals continue to denote like or corresponding parts.

[0139] For convenience, the single epicyclic gear set in Figure 20 is simply referenced EPl. It has sun, planets, planet carrier and ring, similar to the parts 21a, 22a, 23a and 24a in the previous figures, including Figure 15. In Figure 20, there is no second epicyclic gear set such as EP2 as shown in the preceding figures. This simplifies size, weight and cost of the drive system.

[0140] Figure 20 shows first motor 5,6 and second motor 205, 206, as before.

[0141] An addition in Figure 20 is a gear set 300 comprising a pair of gears 307, 308 that are driven by respective output gears 27, 28 via respective intermediate or idler gears 317, 318 and are connectable via active clutch K8 activated by solenoid S. Gears 27, 307 afford a different gear ratio to gears 28, 308. Active clutch K8 can be activated via solenoid S to lock together or unlock gears 307, 308 in response to a sensed parameter - e.g. cycle speed.

[0142] Figures 21 to 24 illustrate those parts of the drive system that are operative for respective drive modes.

[0143] Figure 21 is similar to Figure 16, illustrating a first mode of the drive train, which provides pedal-only drive. In use, pedal drive is transmitted from crankshaft 150 directly to drive wheel, ring or cog 60, which in turn drives rear sprocket 80. There is no electrical assistance from either motor 5,6 or second motor 205, 206. As before, this first mode may be selected to launch the cycle from rest, with a lowest gear ratio between crankshaft 150 input and output member 100.

[0144] Figure 22 is analogous to Figure 17, illustrating a second mode of the drive train. However, in Figure 22, only the single epicyclic gear set EPl receives input from pedals 50 and motor 5,6 to afford a continuously variable transmission (CVT), in a manner that is known generally to the skilled reader.

[0145] Figure 23 is similar to Figure 18 and illustrates a third mode of the drive train, where the first motor 5, 6 is not activated and no drive need be provided via the pedals 50 and crankshaft 150. In this mode, a direct motor drive is provided by the second motor 205, 206, but this can alternatively be used in combination with the first motor 5,6 (which controls the pedal cadence) in all modes in which it is legal to aid the driver (e.g. below the speed limit). The control system could also be set up so that the rider may control the second motor output torque by way of a throttle control.

[0146] Figure 24 illustrates a simpler embodiment of a fourth mode of the drive train. This enables pedal-only drive but the gearing between pedals 50 and output member 100 is now much higher than at start up in first mode. This facilitates pedal drive at higher speeds - for example, greater than 25 km / h -with a pedal cadence that is achievable by the rider. The higher gearing is obtained as follows.

[0147] The gear set 300 provides a means to lock gears 307, 308 together, so that they rotate at the same speed. As the two gears 307, 308 have different numbers of teeth, they force the pedal output 28 and the drive output 27 to rotate with an output:input ratio that is greater than 1.

[0148] Referring to Figure 6, when the pedal cadence and cycle speed fall on the lines 44 and 44a, the two gears 307, 308 will rotate at the same speed, and therefore can be locked to rotate in unison by means of the clutch K8 activated by solenoid S, without any jolts. If the system operation is below line 44a, e.g. line 43, the one-way clutch K8 can be used to connect the two gears, the clutch will lock, and the two gears 307, 308 will start rotating in unison if the system tries to operate above line 44a or 44, effectively creating the higher pedal-only ratio.

[0149] The system of Figure 24 shows one of two options for achieving the higher pedal-only ratio, once the line 44a is crossed downwardly. That is, a gear pair that will invert their relative speed of rotation and therefore can be connected to each other by one-way clutch K8 without jolts. If the system tries to go back to operating above line 44a, the clutch will prevent it by locking.

[0150] This is an alternative option to that shown in the previous examples of Figures 2, 5, 7, 8,10,14,15 and 19, by engaging clutches K2 or K5, depending on the figure. In those systems, ring 24b of EP2 changes direction of absolute rotation, and therefore can be connected to ground by the one-way clutch K2 or K5 without jolts. If the system tries to go back to operating above line 44a, the clutch will prevent it by locking.

[0151] The drive systems of all of the preceding examples typically incorporate a controller such as 91 and battery such as 93 but, in the interests of clarity, these are not shown in all of the figures.

[0152] The drive systems of all of the preceding examples typically incorporate a controller such as 91 and battery such as 93 but, in the interests of clarity, these are not shown in all of the figures.

[0153] The above-described and illustrated examples of the invention may provide drive systems for electrically-assisted pedal cycles that are effective whilst being relatively light and compact and, in particular, allow the rider the convenience of CVT operation up to a predetermined speed, after which the rider can continue to increase speed by pedalling, without electrical assistance and with a practical and effective gear ratio between pedal and wheel. Moreover, parallel hybrid mode can be selected at anytime where additional pedal torque is desirable to supplement motor torque.

[0154] The above-described and illustrated examples of the invention may be realised as pedelecs or other electrically-assisted pedal cycles.

[0155] Whilst examples of motors and drive trains have been illustrated and described, other embodiments of the invention may have different configurations of motors and drive trains. Instead of a single motor, as in the illustrated examples, dual motors or dual electrical machines may be used.

[0156] 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.

[0157] 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.

[0158] 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.

[0159] 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. A drive system for an electrically-assisted pedal cycle, the system comprising:an inputthat, in use, receives drive from a pedal of the cycle and rotates about an input axis;an output that, in use, rotates about an output axis to provide drive to a driven wheel of the cycle;an electrical machine that, in use, provides motor drive to said output; anda drive train that, in use, receives drive from the electrical machine and the pedal and transmits drive to said output:wherein the drive train is operable in one mode to provide a continually variable transmission (CVT) by which pedal cadence is controlled by the electrical machine;the drive train is operable in another mode to provide output drive both from said pedal and said electrical machine in parallel; andthe drive system further comprises a mode selector that is operable to select said modes.

2. A drive system according to claim 1, wherein:said one mode is a second mode;said another mode is a third mode;between cycle speeds of 0 and VI, where Vl>0, the drive train is operable in a first mode to provide output drive only from said pedal;at cycle speeds greater than VI, the drive train is operable in said second mode to provide a continually variable transmission (CVT); andthe mode selector is operable to select said first, second or third mode.

3. A drive system according to claim 1 or 2, wherein:above a cycle speed of V2, the drive train is operable in a fourth mode to disengage drive from the electrical machine to provide output drive only from said pedal; andthe mode selector is operable to select said first, second, third or fourth mode.

4. A drive system according to claims 2 and 3, wherein:above a cycle speed of V2, which is greater than VI, the drive train is operable in said fourth mode to disengage drive from the electrical machine to provide output drive only from said pedal, with a gear ratio that is higher than that provided below a cycle speed of VI.

5. A drive system according to any of the preceding claims, wherein the drive train comprises an epicyclic gear set having a first input connected to the electrical machine and a second input connected to the pedal.

6. A drive system according to claim 5, wherein the epicyclic gear set is a dual epicyclic gear set having first and second stages, the first stage comprising afirst sun, planets and annulus and the second stage comprising a second sun, planets and annulus.

7. A drive system according to claim 6, wherein the mode selector isoperable to connect and disconnect said first and second stages.

8. A drive system according to claim 7, wherein the mode selector is operable to connect said first and second stages when the drive train operates in said one mode or said second mode to provide a continually variable transmission (CVT).

9. A drive system according to claim 7 or 8, wherein the mode selector is operable to disconnect said first and second stages when the drive train does not operate in said one mode or said second mode to provide a continually variable transmission (CVT).

10. A drive system according to any of the preceding claims wherein, when the drive train operates in said another mode or said third mode to provide output drive both from said pedal and said electrical machine in parallel, the mode selector is operable to connect said first planet carrier with a one-way clutch that, in use, is fixed with respect to the cycle.

11. A drive system according to claim 3 or 4 together with any of claims 5 to 10 wherein, when the drive train operates in said fourth mode to provide output drive only from said pedal, the mode selector is operable to connect said second planet carrier with a one-way clutch that, in use, is fixed with respect to the cycle.

12. A drive system according to any of the preceding claims, wherein the mode selector comprises a moveable mechanical link.

13. A drive system according to any of the preceding claims, where the mode selector is operable manually.

14. A drive system according to any of the preceding claims, where the mode selector is operable automatically in response to sensed parameters.

15. A drive system according to claim 14, where said sensed parameters include cycle speed and / or incline.

16. A drive system according to any of the preceding claims, wherein said input axis and said output axis are the same axis.

17. A drive system according to any of claims 1 to 15, wherein said input and output axes are spaced from one another.

18. A drive system for an electrically-assisted pedal cycle, the system comprising:an inputthat, in use, receives drive from a pedal of the cycle and rotates about an input axis;an output that, in use, rotates about an output axis to provide drive to a driven wheel of the cycle;an electrical machine that, in use, provides motor drive to said output;anda drive train that, in use, receives drive from the electrical machine and the pedal and transmits drive to said output:wherein:the drive train is operable in one mode to provide a continually variable transmission (CVT) by which pedal cadence is controlled by the electrical machine;above a cycle speed of V2, the drive train is operable in another mode to disengage drive from the electrical machine to provide output drive only from said pedal, with a gear ratio between said input and output that is higher than that upon startup of the cycle;said input axis is an axis of rotation of a pedal crankshaft; andthe electrical machine and drive train are offset with respect to said input axis.

19. A drive system according to claim 18, wherein the drive train further comprises a second electrical machine that, in use, provides motor drive to said output.

20. A drive system according to claim 19, wherein the drive train is operable in a further mode to provide output drive only from said second electrical machine.

21. A drive system according to claim 18,19 or 20, wherein the drive train comprises a single epicyclic gear set.

22. A drive system according to any of the preceding claims, further comprising a pair of gears that are configured to be locked together to provide agear ratio between said input and output that is higher than that upon startup of the cycle.

23. An electrically-assisted pedal cycle having a drive system according to any of the preceding claims.

24. An electrically-assisted pedal cycle according to claim 23, being a pedelec in which electrical assistance is provided only when the cyclist is pedalling.

25. An electrically-assisted pedal cycle according to claim 23, in which electrical assistance is available both when the cyclist is pedalling and also when the cyclist is not pedalling.

26. An electrically-assisted pedal cycle according to claim 25, having a throttle control by which a cyclist can apply or superimpose a desired amount of electrical assistance.

27. An electrically-assisted pedal cycle according to any of claims 23 to 26, wherein the drive train is located within a hub of the driven wheel.

28. An electrically-assisted pedal cycle according to any of claims 23 to 26, wherein the drive train is located around or adjacent a crankshaft connecting two pedal cranks.

29. An electrically-assisted pedal cycle according to claim 28, wherein the drive train is in accordance with claim 17, the input axis of the drive train is the axis of rotation of the crankshaft and the output axis of the drive train is parallel to but spaced from the input axis.

30. A method of operating an electrically-assisted pedal cycle according to any of claims 23 to 29, comprising the steps of providing motor drive to the driven wheel of the cycle by the or each said electrical machine and providing pedal drive to the driven wheel of the cycle, via said drive train.5 31. A drive system for an electrically-assisted pedal cycle, the system beingsubstantially as hereinbefore described with reference to the accompanying drawings.

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

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