Electric power-assisted pedal bicycle

Abstract

An electric power pedal bicycle (10) has a drive system having an input (80) that receives drive from a pedal (40) of the bicycle (10) and rotates about an axis; an output (100) that rotates about the axis to provide drive to a bicycle wheel (30); an electric motor providing motor drive for the output (100); and a driveline that receives the drive from the motor and the pedal (40) and transmits the drive to the output (100). Between bicycle speeds V1 and V2, where V2 is greater than V1, the driveline provides a continuously variable transmission (CVT) by which the motor controls pedal rhythm. At the bicycle speed V2 or above, the driveline disengages the drive from the electric motor and provides only the output drive from the pedals (40).

Description

Technical Field

[0001] The invention relates to an electric power-assisted pedal bicycle. Background Art

[0002] There are many forms of pedal bikes. One traditional form of pedal bike is one that is propelled solely by the rider applying force to the pedals, which is sometimes called a "push bike". Another newer form of pedal bike is an electric-assisted pedal bike, now commonly referred to as an "e-bike", in which electricity is used to assist or replace the rider's effort. Both traditional pedal bikes and e-bikes may have two wheels, three wheels, or four wheels, or even more in some cases. In this document, the term "pedal bike" is used to include both traditional pedal bikes and e-bikes.

[0003] As mentioned above, in an electric bicycle, electrical power is used to assist or, in some cases, replace the effort of the rider. Thus, an electric bicycle includes means for storing electrical energy, such as a battery, and an electric motor arranged for propulsion in conjunction with or in place of pedal input. The battery may be charged by plugging it into an electrical energy source, such as a mains socket; in some cases, energy may also be recovered from the motion of the bicycle by regenerative braking, and in other cases, electricity is generated by a series hybrid configuration. The principles of regenerative braking will be familiar to those skilled in the art.

[0004] Electric bicycles can generally be divided into two categories. The first category is bicycles that can provide electric assistance on demand at all times, whether or not the rider is pedaling. This category of bicycles can be considered generally equivalent to electric mopeds. Pedal input may be used rarely, or only as a "limp home" function when the battery runs out of power. The second category of bicycles only provide electric assistance when the rider is pedaling. These are called "pedelecs".

[0005] At present, in many countries, including the UK, pedelecs are actually legally classed as conventional bicycles, and can therefore be ridden without a licence or insurance, as long as the pedelec stops at 25km / h (although there is a separate class of 'high-speed pedelecs' which have a speed limit of 45km / h and require a licence and insurance). As a result, there are few barriers to owning and operating an pedelec.

[0006] In recent years, there have been technical advances in the electromechanical drive units used in electric bicycles and in the associated energy storage and recovery devices. These advances have enabled electric bicycles to be operated by the rider with greater efficiency and therefore greater ease.

[0007] Due to all the reasons mentioned above, electric bikes are becoming increasingly popular around the world.

[0008] As background, the reader is referred to our PCT publications WO2010 / 092345, WO2017 / 021715 and WO2018 / 020259, which provide a great deal of information on electric bicycles, and in particular mention the use of continuously variable transmissions (CVTs) in electric power-assisted bicycles.

[0009] The use of CVTs in electric-assisted bicycles is relatively recent and is characterized by advantages such as great convenience of use. Nevertheless, given the early adoption of direct-drive systems in electric-assisted bicycles, the riding feel of CVTs needed to be adjusted to behave and feel similar to the direct-drive that has become the norm. This involved modifying the mechanical construction of the CVT to provide additional boost capability during start-up and high-torque demand situations. The question then arose how to engage and disengage the additional electric assistance in a controlled and smooth manner.

[0010] One aspect of using a CVT system is that in areas where there is a maximum speed limit for electric assistance (25 km / h in many countries), the rider may wish to increase the speed above that limit, and this must be done without electric assistance. Therefore, it is necessary to be able to switch from electric assistance to manual pedaling to achieve higher speeds and then switch back again in a controlled and smooth manner. Summary of the invention

[0011] The preferred embodiment of the present invention aims to provide an electric power-assisted vehicle and its drive system to seek to meet the above requirements. The embodiment of the present invention may be particularly effective when a 3-branch power combination planetary transmission (two inputs and one output) is used in a CVT transmission.

[0012] According to one aspect of the present invention, there is provided a driving system for an electric power-assisted pedal bicycle, the system comprising:

[0013] an input which, in use, receives drive from the pedals of the bicycle and rotates about an axis;

[0014] an output which, in use, rotates about the axis to provide drive to a driven wheel of the bicycle;

[0015] an electric machine which, in use, provides motor drive to the output; and

[0016] a drive train which, in use, receives drive from the motor and the pedal and transmits drive force to the output:

[0017] in:

[0018] Between bicycle speeds V1 and V2, where V2 is greater than V1, the drive train provides a continuously variable transmission (CVT) by which pedal cadence is controlled by the motor; and

[0019] Above bicycle speed V2, the drive train disengages drive from the motor to provide output drive from the pedals only.

[0020] Preferably, V1>0, and between bicycle speeds 0 and V1, the transmission system provides output drive only from the pedals.

[0021] Preferably, above the bicycle speed V2, the transmission system provides a higher gear ratio than that provided below the bicycle speed V1.

[0022] Preferably, the drive train comprises a planetary gear set having a first input connected to the motor and a second input connected to the pedal.

[0023] Preferably, the planetary gear set is a double planetary gear set having a first stage and a second stage connected to each other, the first stage comprising a first sun gear, planet gears and a ring gear, and the second stage comprising a second sun gear, planet gears and a ring gear.

[0024] Preferably, the electric machine has a rotor connected to drive the first sun gear.

[0025] Preferably, drive from the pedal is connected to drive the second planet carrier.

[0026] Preferably, the first ring gear is connected for rotation with the output.

[0027] Preferably, the second sun gear is connected for rotation with the output.

[0028] Preferably, the second ring gear is connected for rotation with the first planet carrier.

[0029] Preferably, a first one-way clutch is connected between said pedal input and said output to prevent said pedal input from rotating faster than said output.

[0030] Preferably, a second clutch is connected between the movable part of the transmission and the fixed part of the drive system or a respective bicycle, and an actuator of the second clutch activates the clutch to operate in a unidirectional mode.

[0031] Preferably, the actuator is responsive to an angular velocity of the output.

[0032] Preferably, the actuator is electrically operated.

[0033] Preferably, the actuator is selectively operable to cause the second clutch to lock the second planet carrier to the fixed portion.

[0034] Preferably, the movable part of the drive train is the second ring gear.

[0035] Preferably, a third one-way clutch is connected between the motor and the transmission system.

[0036] Preferably, V1 =5 kph.

[0037] Preferably, V2 = 25 kph.

[0038] The present invention extends to an electric power-assisted pedal bicycle having a drive system according to any of the preceding aspects of the present invention.

[0039] An electric power-assist pedal bicycle may be an electric power-assist bicycle that provides electric power assistance only when the rider pedals.

[0040] Alternatively, electric assist may be provided both when the rider is pedaling and when the rider is not pedaling.

[0041] In this case, the electric assist pedal bicycle may have a throttle control by which the rider can apply or overlay a desired amount of electric assist.

[0042] The transmission system may be located in the hub of the driven wheel. Alternatively, the transmission system may be located around or near the crankshaft connecting the two pedal cranks.

[0043] The driven wheel can be the rear wheel or the front wheel.

[0044] The present invention extends to a method of operating an electric power-assisted pedal bicycle according to any of the above aspects of the invention, comprising the steps of providing motor drive to the driven wheel of the bicycle via the motor, and providing pedal drive to the driven wheel of the bicycle via the transmission system.

[0045] In the context of this specification, the term "electric power-assisted bicycle" refers to an electric power-assisted pedal bicycle, in which electric power assistance is provided only when the rider pedals. BRIEF DESCRIPTION OF THE DRAWINGS

[0046] For a better understanding of the invention, and to show how embodiments of the invention may be carried into effect, reference will now be made, by way of example, to the accompanying drawings, in which:

[0047] Figure 1 It is a side view of the electric power-assisted bicycle;

[0048] Figure 2 It is a schematic diagram of the drive system of the electric power-assisted bicycle;

[0049] Figure 3 is a graph showing the relationship between pedal cadence (RPM) and electric assist vehicle (bicycle) speed;

[0050] Figure 4 is a graph showing the relationship between the angular velocity (RPM) of the ring gear of the planetary gear set and the speed of the electric power-assisted vehicle (bicycle);

[0051] Figure 5 is a graph showing the relationship between the angular speed (RPM) of the electric drive motor driving the sun gear of the planetary gear set and the speed of the electric power-assisted vehicle (bicycle);

[0052] Figure 6 An embodiment of a one-way clutch is shown in an activated (enabled) state and a deactivated (disabled) state; and

[0053] Figure 7 is similar to Figure 2 , but showing a mid-drive configuration.

[0054] In the drawings, the same reference numerals denote the same or corresponding parts. DETAILED DESCRIPTION

[0055] It should be understood that the various features described below and / or shown in the accompanying drawings are preferred, but not essential. The combination of features described and / or shown is not considered to be the only possible combination. Unless otherwise stated, individual features may be omitted, changed or combined in different combinations where feasible.

[0056] Figure 1 An electric power-assisted bicycle in the form of a bicycle 10 is shown. The bicycle 10 is similar to a conventional bicycle, having a steerable wheel 20 at the front and a driveable wheel 30 at the rear. The bicycle 10 also has a conventional pedal 40 arranged on a crank arm 50, which drives a front toothed gear 60, which is connected to a rear sprocket 80 via a chain or toothed belt 70, and the rear sprocket is mounted coaxially with the rear wheel 30. However, the bicycle 10 differs from a conventional bicycle in that the rear sprocket 80 is not fixedly mounted on the hub 100 of the rear wheel 30 to directly drive the wheel. Instead, the rear sprocket 80 provides the rider's power input to a drive system disposed within the hub 100. A control housing 90 and a battery housing 92 are mounted on the frame of the bicycle 10.

[0057] The drive system is installed in the wheel hub 100. Figure 2The drive system provides a transmission system that receives drive from the motor and pedals 40 and transmits the drive to the output. For ease of explanation, the hub 100 is hereinafter referred to as the outer hub 100, and the hub 100 provides the output of the drive system. The outer hub 100 is generally connected to the outside of the rear wheel 30 by spokes or any other connection to provide drive to the rear wheel 30.

[0058] It is worth noting that, for ease of explanation, Figure 2 The schematic diagram of FIG. 1 shows only the upper part of the drive system, in which a plurality of planetary gears are arranged around the axis of a central axle 1 fixed to the bicycle frame.

[0059] As mentioned above, the sprocket 80 is not directly connected to the outer hub 100, as is the case with conventional bicycles. Instead, the sprocket 80 is connected to the inner hub 2 mounted on a bearing (not shown) for rotation about a fixed axle 1 fixed to the bicycle frame. The sprocket 80 is preferably combined with a freewheel mechanism, as is found on many conventional bicycles. The outer hub 100 is generally cylindrical and is mounted at a first end on the inner hub 2 via a one-way clutch K1. The other end of the outer hub 100 is mounted on the axle 1 via 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 one-way clutch K1 may be formed by a bearing and a separate clutch.

[0060] The motor comprises a stator 5 fixedly mounted on the axle 1 and a rotor 6 mounted on a shaft 7 mounted on suitable bearings (not shown) for rotation about the axle 1. The first stage EP1 of the double planetary gear set EP1, EP2 connects the shaft 7 to the outer hub 100. The axle 1 is hollow and receives cables to connect the controller 91 (and battery 93) to components of the drive system.

[0061] The double planetary gear set EP1, EP2 provides a high transmission ratio and a small packaging space for a given torque capacity. The first planetary stage EP1 includes a first sun gear 21a, planet gears 22a, a planet carrier 23a and a ring gear or ring 24a. The first ring gear or ring 24a rotates integrally with the outer hub 100. The first sun gear 21a is optionally connected to the shaft 7 via a one-way clutch K3. There may be two, three or more planet gears 22a.

[0062] The second planetary stage EP2 comprises a second sun gear 21b, planetary gears 22b, a planetary carrier 23b and a ring gear or ring 24b. The second ring gear or ring 24b is connected to the first planetary carrier 23a, and both are also connected to the axle 1 through a one-way clutch K2, which can be selectively activated and deactivated (i.e. allowed or not allowed to prevent rotation in one direction). The second sun gear 21b is connected to rotate with the outer hub 100. There can be two, three or more planetary gears 22b.

[0063] The one-way clutch K2 can be selectively activated and deactivated based on the sensed angular rotational speed of the outer hub 100, which is proportional to the linear travel speed of the bicycle 10. For this purpose, a speed sensor 31 is provided. This can act directly on the clutch K2, which responds passively to be activated or deactivated. For example, a governor type mechanism can be used. A magnetic fluid can alternatively be used to use the movement of the hub 100 to enable the clutch K2. Alternatively, a solenoid or other actuator 32 can respond to the sensed speed to activate and deactivate the clutch K2, as described below with reference to Figure 6 Further description.

[0064] In use, pedal drive is transmitted to the rear sprocket 80 connected to the planet carrier 23b to drive its rotation. The planetary gear 22b transmits the driving force to the sun gear 21b that rotates with the outer hub 100. In short, the power input by the rider from the pedal 40 is transmitted to the planetary carrier 23b through the sprocket 80, and then to the outer hub 100 to drive the rear wheel 30. The electric assist from the rotor 6 is provided by the sun gear 21a. The speed of the motor can be changed relative to the hub speed to continuously change the rider's rhythm, so that EP1 and EP2 provide a continuously variable transmission (CVT). An embodiment of such a CVT is given in our above-mentioned WO publication.

[0065] Before describing the operation of the drive system shown, please note that Figure 3 , to illustrate potential problems with CVT systems and how the problems are solved by the illustrated embodiments of the present invention.

[0066] First, it should be noted that in some countries, the law requires that the motor assistance is not allowed until a speed of 5kph is reached. This is observed in the illustrated embodiment.

[0067] exist Figure 3 In FIG. 1 , a line comprising four straight sections 41, 42, 43 and 44 is drawn for an electric bicycle with a wheel diameter of 700 mm, representing the behavior of the drive system shown, showing the relationship between the cadence (RPM) of the pedals 40 and the linear speed (kph) of the bicycle 10. The behavior changes at bicycle speeds V1 and V2, which in this embodiment are 5 kph and 25 kph respectively, but in principle can be any suitable speed.

[0068] At the origin (0,0), the rider begins pedaling and the bicycle begins to move. Prior to speed V1, power is provided solely by the rider. This is represented by line portion 41, which in this embodiment represents the lowest gear ratio of 1:1. If no electric assistance were provided, the behavior of the drive system would continue along line portion 41b, which is an extension of line portion 41.

[0069] However, at speed V1, the pedaling cadence is about 38 rpm, electric assist is introduced and the linear speed of the bicycle continues to increase to speed V2 with little change in the pedaling cadence, as shown by line portion 42, which is controlled by setting the speed of the motors 5, 6. This allows the cadence change between speed V and point B to be set. In this embodiment, at speed V2, the pedaling cadence is about 45 rpm. In practice, line portion 42 can be substantially straight and horizontal. The rider continues to pedal at a speed of about 40 rpm, and as long as pedaling continues and there is sufficient torque, the bicycle speed will increase to V2. Therefore, line portion 42 indicates that the drive system is providing a continuously variable transmission (CVT) in which the ratio between the rider cadence and the bicycle speed changes continuously.

[0070] At speed V2, electric assistance is reduced and pedaling cadence increases, as shown by line portion 43. At a speed of approximately 28 kph and a pedaling cadence of approximately 58 rpm (in this embodiment), electric assistance ceases, and any further speed increase is achieved by the rider continuing to pedal at an increasing cadence, as shown by line portion 44. The slope of line portion 44 indicates that the highest chain or belt ratio is approximately 50:14 (in this embodiment). Line portion 44a represents the same ratio, extrapolated back to the origin (0,0).

[0071] It should be understood that if the behavior of the drive system is not suitable for following the Figure 3 If the electric assist CVT is performed in the manner shown (for example), once the electric assist CVT is exited at V2, the pedal cadence will have to be increased at a surprising rate in order to increase the speed above V2. In fact, it is difficult to increase the speed above V2 by pedaling alone. When the motors 5, 6 are not powered, the cadence will be determined by line 41b.

[0072] We will now describe Figure 2 How the drive system shown in Figure 1 operates to achieve Figure 3 First, the acceleration of the bicycle 10 from rest is described.

[0073] Mode 1: Pedal only Low speed: Line section 41

[0074] Starting from rest (0,0), the rider begins pedaling. One-way clutch K1 locks EP2 by preventing EP2 planet carrier 23b from rotating forward (i.e., rotating faster than outer hub 100 and wheel 30 in the direction of pedaling motion). As a result, EP2 ring 24b also rotates forward with outer hub 100 and wheel 30, and bicycle 10 moves forward. As the rider pedals faster, the bicycle moves faster, reaching a maximum speed of V1 (5 km / h).

[0075] To explain further, the EP2 clutch K1 forces the hub 100 to rotate forward at the same speed as the sprocket 80 through the inner hub 2. Therefore, the traction force passes through the clutch K1. The secondary effect is that the ring 24b and the planet carrier 23a also rotate at the same speed as the sprocket 80. Therefore, in EP1, the ring 24a and the planet carrier 23a also rotate at the speed of the sprocket 80. Therefore, the sun gear 21a also rotates at the speed of the sprocket 80.

[0076] Switch to Mode 2: Electric Assist (CVT)

[0077] When approaching V1, the rotor 6 starts to rotate backward, thereby disengaging the EP2 clutch K1 at a speed V1 by slowing down the speed of the EP2 ring 24b.

[0078] Mode 2: Electric Assisted Vehicle (CVT): Line Section 42

[0079] The motors 5, 6 control the pedal cadence by adjusting the speed of the EP2 ring 24b. At a given bicycle speed, and depending on the desired cadence (given by Figure 3 At point A in FIG. 1 ), the EP2 ring 24b will be stationary, and beyond this speed, it will rotate backwards.

[0080] Switch to Mode 3: Pedal Only - High Speed: Line Sections 42, 43

[0081] In this embodiment, the conversion can be achieved when the speed increases to between 22 kph and 27 kph, by Figure 3 Points A and B in are represented.

[0082] As the EP2 ring 24b rotates backward, the one-way clutch K2 is activated (enabled, not locked) to prevent the EP2 ring 24b, which is now rotating backward, from rotating forward.

[0083] When the bicycle speed exceeds V2 (e.g., the legal limit), the motors 5, 6 reduce or reverse their acceleration, and the EP2 ring 24b, which is still rotating backwards, will slow down. When the motor speed is low enough, the EP2 ring 24b will Figure 3 The one-way clutch K2 will prevent it from rotating forward at the point B in the middle. Therefore, the bicycle speed exceeding the point B, the EP2 ring 24b remains stationary.

[0084] Mode 3: Pedal Only - High Speed: Line Section 44

[0085] With one-way clutch K2 engaged, the rider can pedal unassisted at high speeds, limited only by the rider's ability, with a gear ratio (wheel to pedal speed) of about 50:14 (in this embodiment). When ring 24b is stationary, the motor rotates at a speed determined by EP1 and EP2. When clutch K3 is in place, the motor speed can be lower.

[0086] The deceleration of the bicycle 10 from a high speed, pedal-only operation to a stationary state will now be described.

[0087] Mode 3: Pedal Only - High Speed: Line Section 44

[0088] As the rider reduces pedal torque and cadence, the bicycle speed decreases.

[0089] Switch to Mode 2: Electric Assisted Vehicle (CVT): Line Section 43, 42

[0090] When the bicycle speed decreases, the motors 5, 6 are accelerated again to match the pedaling rhythm of point B and engage clutch K3. When the EP2 ring 24b starts to rotate backwards, the one-way clutch K2 is disengaged. If the clutch K3 is omitted, the motors 5, 6 are already running at the correct speed, so by applying power to the motors, the clutch K2 is unlocked.

[0091] Mode 2: Electric Assisted Vehicle (CVT): Line Section 42

[0092] The motors 5, 6 control the pedal rhythm by adjusting the speed of the EP2 ring 24b.

[0093] As the bicycle speed decreases and the EP2 ring 24b rotates backward, the one-way clutch K2 is deactivated to allow the currently backward rotating EP2 ring 24b to begin rotating forward when point A is passed.

[0094] The speed range over which clutch K2 is activated and deactivated is represented by reference X. This range will be within the speed interval between point A and point B. The range X may vary depending on the configuration. If clutch K2 is actively controlled (e.g. by solenoid 32), the range may be very narrow, and if it is passively controlled (e.g. by a speed governor mechanism), the range may be wider.

[0095] Shift to Mode 1: Pedal Only Low Speed: Line Section 41

[0096] As the bicycle speed decreases further, the motors 5, 6 are de-energized and the rotor 6 begins to rotate forward at the same speed as the outer hub 100, wheel 30 and EP2 planet carrier 22b, thereby allowing the one-way clutch K1 to re-engage.

[0097] Mode 1: Pedal only low speed: Line section 41

[0098] One-way clutch K1 locks EP2 by preventing EP2 ring 24b from rotating faster than outer hub 100 and wheel 30. Therefore, as bicycle 10 moves forward, EP2 ring 24b rotates forward along with outer hub 100 and wheel 30. As the rider pedals slower and / or applies the brakes, the bicycle moves slower and eventually stops.

[0099] Figure 4 The relationship between the angular velocity (rpm) of the EP2 ring 24b and the linear speed (kph) of the bicycle is shown. The ring 24b is initially Figure 3 The ring 24b rotates forward synchronously with the pedal speed in the bicycle, from 0 rpm to V1. Thereafter, the speed of the ring 24b decreases in a somewhat linear manner from V1 to V2 to achieve the desired rhythmic change in bicycle speed, from the forward direction to the backward direction at point A. From V2, the negative speed of the ring 24b decreases to zero at point B, at which point the electric assistance stops. From point B, as the bicycle speed increases, the ring 24b is held stationary by the clutch K2.

[0100] Figure 5 The relationship between the angular velocity (rpm) of the motor 5, 6 (i.e., the rotor 6) and the linear speed (kph) of the bicycle is shown. The rotor 6 initially rotates forward at a relatively slow speed, from 0 rpm to V1. Thereafter, the rotor speed increases linearly in the backward (negative) direction opposite to the direction of pedaling motion, from V1 to V2. From V2, the negative speed of the rotor 6 increases more slowly to point B, at which point the electric assistance stops. From point B, the rotor 6 rotates backward at a steadily increasing speed as the bicycle speed increases. This region is Figure 5 The chain ellipse in FIG. 4 shows that the motors 5 and 6 can be operated in generator mode to achieve power regeneration. For this purpose, the one-way clutch K3 is omitted and additional circuitry is required to accommodate any regenerated power. If power regeneration is not required, the one-way clutch K3 remains in place. The purpose of the clutch K3 is to prevent the rotor 6 from being driven and the motors 5 and 6 then enter generator mode.

[0101] A feature of the illustrated embodiment is that the drive system allows the bicycle to be pushed backwards. To this end, the one-way clutch K1 locks EP2 so that the wheel 30 and the outer hub 100 rotate the EP2 ring 24b backwards, thereby rotating the rotor 6. The rotor 6 can rotate regardless of whether the clutch K2 is active and locked.

[0102] Figure 6 An exemplary embodiment of the clutch K2 is shown.

[0103] In the top view (A), the clutch K2 is deactivated (disabled). The actuator 51 acts on the lever 52 of the pawl 53 mounted in the inner ring 55 so that the pawl 53 is out of engagement with the teeth 54 in the outer ring 56 .

[0104] In the lower view (B), the clutch K2 is activated (enabled). The actuator 51 no longer acts on the rod 52, so the pawl 53 can freely pivot outward (e.g. under the bias of a resilient spring) to engage with the teeth 54 in the outer ring 56. Thus, drive is provided between the inner ring 55 and the outer ring 56.

[0105] As described above, the actuator 51 may take various forms.

[0106] The configuration shown allows the bicycle 10 to be pushed in a side-by-side walking mode. While pushing, some motor assistance may be provided. For example, in accordance with EU regulations, when pushing an electric bicycle, the person pushing the vehicle can use the walking assist button to activate the motor, providing him / her with additional torque up to a bicycle speed of 6 km / h.

[0107] The illustrated embodiment of the invention may be adapted to allow the motors 5, 6 to propel the bicycle without the rider pedalling, ie to operate in a "throttle mode".

[0108] In the above description, the clutch K2 is activated between points A and B in the diagram, and then it behaves like a one-way clutch. By providing the option of completely locking the clutch K2 (two-way), the motors 5, 6 can directly propel the bicycle in throttle mode.

[0109] When the bicycle is stationary, the clutch K2 can be selectively fully locked (in both directions) under the control of the rider. The rider can choose whether to ride in electric assist mode or throttle mode before departure.

[0110] If the rider wishes to fully lock the clutch K2 while riding to switch from the electric assist mode to the throttle mode, the motors 5, 6 will need to change speed as well as the rider's cadence to bring the EP2 ring 24b to a substantially stationary position, thereby allowing the clutch K2 to be fully locked without significant vibration. The motors 5, 6 may be appropriately controlled by the controller 91 in response to the rider's selected input. Depending on the speed of the bicycle at the time, this may require the rider to increase the pedal cadence (if to the right of point A in the figure) or decrease the pedal cadence (if to the left of point A). The controller 91 may delay full locking of the clutch K2 until the speed of the motors 5, 6 and the rider's pedal cadence reach or approach the desired level to bring the EP2 ring 24b to a substantially stationary position. An audible and / or visual indication may be provided to the rider regarding the need to increase or decrease the pedal cadence.

[0111] Similarly, in order to selectively unlock the clutch K2 to switch from the throttle mode to the electric assist vehicle mode, it may be necessary to control the motor torque so that the locking torque of the clutch K2 is zero or close to zero.

[0112] although Figure 3 The wire portions 42 and 43 are shown in FIG. 5 as being straight, but they do not need to be straight because the shape of the wire portions 42 and 43 is controlled by the motors 5 , 6 .

[0113] Figure 7 The drive system shown in Figure 2 The system operates in a similar manner, and the same reference numerals represent the same or corresponding components. Figure 7 The variant in is configured for use as a central or intermediate drive position, centered around a crankshaft 150 connecting two pedal cranks 50 .

[0114] The drive from the pedals 40 is transmitted to the planet carrier 23b, which in this case is fixed to the shaft 150, and the shaft 150 is driven to rotate with the pedal crank 50. Thus, the shaft 150 provides the input from the pedals 40.

[0115] The stator 5 of the motor 5, 6 is mounted to a housing 130, which is fixed to the frame 140 of the bicycle. The housing 130 has a bearing 101 at one end, which is engaged with the shaft 150, and a bearing 103 at the other end, which is engaged with an output member 100 connected to a ring gear or ring gear 24a. The output member 100 is mounted on a bearing 102 that is engaged with 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 crank 50. The output member 100 is also connected to a chain ring or wheel 60, and the driving force is transmitted from the chain ring or wheel 60 to a driven wheel, which is usually the rear wheel 30, but can also be the front wheel 20.

[0116] The rotor 6 of the motor 5 , 6 is mounted on a shaft 7 which in turn is mounted on suitable bearings (not shown) for rotation relative to the housing 130 .

[0117] In use, input from the pedal crank 50 is applied to the planet carrier 23b. Motor drive is provided to the sun gear 21a. Drive from the output member 100 is transmitted to the driven wheel through a chain ring or wheel 60, which is connected to a drive sprocket on the driven wheel, usually connected by a flywheel mechanism. Although chain drive is the most common, other configurations (such as belt drive or drive shaft) are also possible.

[0118] The same reference numerals represent the same or corresponding components, including clutches K1, K2, K3, and it can be understood that Figure 7 The drive system shown in Figure 2 The system operates in a similar manner as described above, particularly with reference to Figures 3 to 6 Apart from the significant differences in construction, the above reference Figures 2 to 6 The description also applies to Figure 7 Embodiment of the invention.

[0119] exist Figure 7 In a configuration of a forward-biased drive, the gear ratios of the planetary gear sets may be different from those in a rear-drive configuration.

[0120] The above-described and illustrated embodiments of the present invention may provide a drive system for an electrically assisted pedal bicycle which is efficient and relatively light and compact, and in particular allows the rider to conveniently operate the CVT at a predetermined speed, after which the rider may continue to accelerate by pedaling without electric assistance, and with a practical and efficient gear ratio between the pedals and the wheels.

[0121] In principle, V1 and V2 can have any reasonable values, although this may often be dictated by local law. V1 can be zero, where there is no legal minimum speed for electric assistance.

[0122] Although electric motor and drive train embodiments have been illustrated and described, other embodiments of the present invention may have different electric motor and drive train configurations.

[0123] In this specification, the verb "comprise" has its normal dictionary meaning, indicating non-exclusive inclusion. That is, the use of the word "comprise" (or any of its derivatives) to include one or more features does not exclude the possibility of also including other features. The word "preferably" (or any of its derivatives) indicates one or more preferred but non-essential features.

[0124] The reader's attention should be directed to all priority documents related to the present application and all papers and documents filed concurrently with or before the present application and open to the public with the present specification, and the contents of all such papers and documents are incorporated herein by reference.

[0125] All or any features disclosed in this specification (including any accompanying claims, abstract and drawings), and / or all or any 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.

[0126] Unless expressly stated otherwise, each feature disclosed in this specification (including any accompanying claims, abstract and drawings) may be replaced by an alternative feature having the same, equivalent or similar purpose. Therefore, unless expressly stated otherwise, each feature disclosed is merely one embodiment of a series of generally equivalent or similar features.

[0127] The invention is not limited to the details of the foregoing embodiments. The invention extends to any novel feature or any novel combination of features disclosed in this specification (including any accompanying claims, abstract and drawings), or to any novel feature or any novel combination of steps of any method or process so disclosed.

Claims

1. A drive system for an electric power-assisted pedal bicycle, the system comprising: an input which, in use, receives drive from the pedals of the bicycle and rotates about an axis; an output which, in use, rotates about the axis to provide drive to a driven wheel of the bicycle; an electric motor which, in use, provides motor drive to the output; as well as a drive train which, in use, receives drive from the motor and the pedal and transmits drive force to the output: in: Between bicycle speeds V1 and V2, where V2 is greater than V1, the drive train provides a continuously variable transmission (CVT) by which pedal cadence is controlled by the motor; as well as Above bicycle speed V2, the drive train disengages drive from the motor to provide output drive from the pedals only.

2. The drive system according to claim 1, wherein: V1>0, and between bicycle speeds 0 and V1, the drivetrain provides output drive only from the pedals.

3. The drive system according to claim 2, wherein: Above bicycle speed V2, the transmission system provides a higher gear ratio than that provided below bicycle speed V1.

4. A drive system according to any one of the preceding claims, wherein: The powertrain includes a planetary gear set having a first input connected to the motor and a second input connected to the pedal.

5. The drive system according to claim 4, wherein: The planetary gear set is a double planetary gear set having a first stage and a second stage connected to each other, the first stage including a first sun gear, planet gears, and a ring gear, and the second stage including a second sun gear, planet gears, and a ring gear.

6. The drive system according to claim 5, wherein: The electric machine has a rotor connected to drive the first sun gear.

7. The drive system according to claim 5 or 6, wherein: Drive from the pedal is connected to drive the second planet carrier.

8. A drive system according to claim 5, 6 or 7, wherein: The first ring gear is connected for rotation with the output.

9. The drive system according to any one of claims 5 to 8, wherein: The second sun gear is connected for common rotation with the output.

10. The drive system according to any one of claims 5 to 9, wherein: The second ring gear is connected for common rotation with the first planet carrier.

11. A drive system according to any one of the preceding claims, wherein: A first one-way clutch is connected between the pedal input and the output to prevent the pedal input from rotating faster than the output.

12. A drive system according to any one of the preceding claims, wherein: A second clutch is connected between the movable part of the transmission system and the fixed part of the drive system or a corresponding bicycle, and an actuator of the second clutch activates the clutch to operate in a one-way mode.

13. The drive system according to claim 12, wherein: The actuator is responsive to an angular velocity of the output.

14. The drive system according to claim 12 or 13, wherein: The actuator is electrically operated.

15. A drive system according to claim 12, 13 or 14, wherein: The actuator is selectively operable to cause the second clutch to lock the second planet carrier to the stationary portion.

16. A drive system according to any one of claims 12 to 15 as appended to claim 5, wherein: The movable part of the drive train is the second ring gear.

17. A drive system according to any one of the preceding claims, wherein: A third one-way clutch is connected between the motor and the transmission system.

18. A drive system according to any one of the preceding claims, wherein: V1=5kph.

19. A drive system according to any one of the preceding claims, wherein: V2=25kph.

20. An electric power-assisted pedal bicycle having a drive system according to any one of the preceding claims.

21. The electric power-assisted pedal bicycle according to claim 20, which is an electric power-assisted bicycle that provides electric power assistance only when the rider pedals.

22. The electric power-assist pedal bicycle of claim 20, which provides electric power assistance both when the rider is pedaling and also when the rider is not pedaling.

23. An electrically assisted pedal bicycle according to claim 22, having a throttle control by which the rider can apply or superimpose a desired amount of electric assistance.

24. An electric power-assisted pedal bicycle according to any one of claims 20 to 23, wherein the drive train is located within the hub of the driven wheel.

25. An electric power-assisted pedal bicycle according to any one of claims 20 to 23, wherein the drive train is located around or near a crankshaft connecting two pedal cranks.

26. The method for operating an electric power-assisted pedal bicycle according to any one of claims 20 to 25, comprising the following steps: Motor drive is provided to the driven wheel of the bicycle by the electric motor, and pedal drive is provided to the driven wheel of the bicycle by the transmission system.

27. A drive system for an electric power-assisted pedal cycle, said system being substantially as hereinbefore described with reference to the accompanying drawings.

28. An electric power-assisted pedal cycle substantially as hereinbefore described with reference to the accompanying drawings.

29. The method of operating the electric power-assisted pedal bicycle is substantially the same as that described above with reference to the accompanying drawings.

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