GB2617391A

GB2617391A - Drive apparatus

Info

Publication number: GB2617391A
Application number: GB2205165.0A
Authority: GB
Inventors: Ravillious Mark
Original assignee: Intra Drive Ltd
Current assignee: Intra Drive Ltd
Priority date: 2022-04-08
Filing date: 2022-04-08
Publication date: 2023-10-11
Anticipated expiration: 2042-04-08
Also published as: GB202205165D0; GB2617391B

Abstract

A drive apparatus is disclosed for a vehicle which can be selectively driven by muscle power and/or motor power, comprising an input 106 to receive muscle-power torque; a motor 10 to provide motor-power torque; an output 105 to provide power to at least one wheel of the vehicle; and a transmission 12 couplable to the input 106 and motor 10 to transfer torque from the input 106 and/or motor 10 to the output 105. The motor 10 has an annular configuration, comprising a stator assembly and rotor assembly arranged annularly around a radially external portion of the motor and defining a central cavity within the motor 10; and the apparatus further comprising a motor reduction gearing 40 disposed within the central cavity.

Description

DRIVE APPARATUS

Field of Invention

The present invention relates to a drive apparatus for a vehicle which can be selectively driven by muscle power and/or motor power. Embodiments of the invention also relate to an e-bike comprising a drive apparatus.

Background

Vehicles which can be selectively driven by muscle power and/or motor power can provide a useful combination of the advantages of powered and muscle-powered vehicles. As such, e-bikes (or electric bikes) are a rapidly growing market and may be generally defined as small vehicles which have an electric drive apparatus but also retain the ability to be human powered (i.e. pedalled). E-bikes are being used as both alternatives to conventional bicycles and as a replacement for fossil fuel powered vehicles (for example mopeds or auto-rickshaws). Particularly in cities, there is great potential for the use of e-bikes as low-carbon replacements for a range of vehicles including delivery and taxi services. In this regard, it will be appreciated that whilst the literal meaning of bicycle relates to two-wheeled vehicles, "e-bike" is broadly used and also includes any other pedal powered vehicle configurations including tri-cycles or quad wheeled vehicles.

There are a range of types and classifications for e-bikes which may in some cases be dependent upon local laws and regulations governing usage. However, for convenience the term e-bike is used broadly herein and may, for example, include vehicles which are purely pedal-assist based (which may be referred to as a "Pedelec" or EAPC) or power-on-demand vehicles which usually include a user-activated throttle.

The applicant has proposed a multi-speed transmission, in International Patent Application W02020/174025. This transmission is compact, lightweight and durable and is particularly suitable for use in vehicles which can be selectively driven by muscle power and/or motor power such as an e-bike. Embodiments of the present invention specifically address the integration of a motor and transmission (which may be a transmission of the type disclosed in W02020/174025) into a drive apparatus.

It is desirable that a drive apparatus for use in vehicles which can be selectively driven by muscle power and/or motor power is lightweight and compact. It is also desirable that the drive assembly provides an efficient arrangement that is durable and requires minimal maintenance. Embodiments of the invention seek to provide a drive apparatus which addresses at least some of these needs.

Summary of Invention

According to a first aspect of the invention, there is provided a drive apparatus for a vehicle which can be selectively driven by muscle power and/or motor power. The drive apparatus comprises an input to receive muscle-power torque; a motor to provide motor-power torque; an output to provide power to at least one wheel of the vehicle; and a transmission couplable to the input and motor to transfer torque from the input and/or motor to the output. The motor has an annular configuration, comprising a stator assembly and rotor assembly arranged a n nularly around a radially external portion of the motor and defining a central cavity within the motor; and the apparatus further comprising a motor reduction gearing disposed within the central cavity.

Embodiments of the invention provide a highly compact arrangement in which the motor and motor reduction gearbox share a common space. Advantageously, this may for example allow the motor and motor reduction gearbox to be coaxial and share the same (or at least overlapping) axial space within the drive apparatus. The provision of an axially compact arrangement is particularly useful in a mid-mounted drive apparatus since the drive apparatus can be located between the pedals of the e-bike. Embodiments of the invention may be particularly advantageous in providing a motor and motor reduction gearbox configuration which can be installed on a side of the transmission without significantly increasing the overall size of the drive apparatus. The transmission may typically include a multi-speed gearbox (the transmission may, for example, be a multi-speed transmission of the type disclosed in International Patent Application W02020/174025). Embodiments may provide a compactly packaged motor reduction gearbox and motor which may enable space within the drive apparatus for the transmission gearing to be maximised (i.e. for a given total housing size). This may for example enable a wider gear range or a greater number of gear speeds to be provided. In some embodiments the drive apparatus may comprise a housing and the housing may comprise a first housing portion enclosing a multi-speed transmission and a second housing portion adjacent to the first housing portion and enclosing the motor and motor reduction gearing.

For example a drive apparatus in accordance with an embodiment may be useful for use in a mid-motor e-bike configuration in which the drive apparatus is located between the pedals and as such the axial space is limited.

The motor may be an axial flux or a radial flux motor. In either configuration the stator assembly and rotor assembly may be arranged annularly. In the case of an axial flux motor an annular stator assembly and an annular rotor assembly may be positioned axially side-by-side around an external portion of the motor. In the case of a radial flux motor an annular stator assembly and an annular rotor assembly may be concentrically arranged around an external portion of the motor.

In embodiments the motor reduction gearing comprises a planetary gearset.

Advantageously a planetary gearbox can be coaxially arranged within the motor. A planetary gearbox can also provide high efficiency and a large reduction ratio in a compact gearing arrangement.

The planetary gearset may comprise an internal gear fixed with respect to the stator assembly. If the internal gear (which may also be referred to as a ring gear) is fixed with respect to the stator it will be appreciated that it may also be fixed with respect to a casing or housing of the drive apparatus. The planetary gearset may also comprise an input gear fixed with respect to the rotor assembly. The internal gear may be adjacent to an internal surface of the radially external portion of the motor (which comprises the stator assembly and rotor assembly). The internal gear may circumferentially surround the central cavity. In a radial flux motor, the rotor assembly may be radially internal to the stator assembly and the internal gear may be adjacent a radially internal surface of the rotor assembly.

The planetary gearset may be a compound planetary gearset. For example the planetary gearset may have two stages.

The rotor assembly may be supported by a motor bearing. The motor bearing may be disposed at one axial side of the motor. As such, the motor bearing may provide a cantilever support to the rotor. Advantageously, a cantilever support arrangement for the motor bearing provides space on the side of the motor without the bearing for the reduction gearing. In embodiments the motor bearing may be positioned on the external side of the drive apparatus and the motor may effectively enclose the motor reduction gearbox. The motor may further comprise a motor housing and the motor bearing may rotatably mount the rotor assembly relative to the motor housing. By providing a cantilever bearing configuration the motor can be supported from a surface of the motor housing without the need for an additional support on the other side of the motor, this can help provide a lightweight arrangement. The stator assembly may also be fixed relative to the housing.

The provision of a single sided bearing arrangement is considered advantageous in its own right. Accordingly, in a further aspect of the invention there is provided a drive apparatus for a vehicle which can be selectively driven by muscle power and/or motor power, the drive apparatus comprising: an input to receive muscle-power torque; a motor to provide motor-power torque; an output to provide power to at least one wheel of the vehicle; and a transmission couplable to the input and motor to transfer torque from the input and or motor to the output. The motor comprises: a stator assembly fixed relative to a motor housing, a rotor assembly rotatably mounted relative to the motor housing, and a motor bearing supporting the rotor assembly.

The rotor bearing is disposed at one axial side of the motor and provides a cantilever support to the rotor.

In embodiments the rotor bearing is axially outside of the stator and rotor. This may for example provide increased space for the motor reduction gearing within the region which is coaxial to the stator and rotor.

In embodiments, the rotor assembly further comprises a rotor support comprising: an axially extending rim for supporting the rotor and a hub connected to the motor bearing. The rotor support may further comprise a radial extending support face disposed at one axial side of the rotor. Thus, the rotor assembly may define a cylindrical tube shape which is open at one axial end (for example the rotor assembly may be generally cup shaped). The open axial end of the rotor assembly may define a mouth of the central cavity of the motor. In embodiments the hub and rotor extend from the opposing axial sides of the radial extending support face support face. The support face may be a non-continuous surface, for example a series of radial spokes.

In some embodiments the support face comprises a solid disk.

The hub may comprise an external seat for the motor bearing. The hub may further comprise an internal bore. The bore may receive an input gear for the motor reduction gearing. The input gear may be mounted to the opposing axial side of the support face from the external seat.

The motor bearing may be a rolling element bearing. The motor bearing may be selected to ensure a strict tolerance for the air gap between the stator and rotor. In some embodiments the motor bearing comprises a double row angular contact bearing. In some embodiments the motor bearing may comprise a needle bearing. In some embodiments the motor bearing may be a four-point contact ball bearing.

The apparatus may further comprise a clutch between the motor and transmission. The clutch may be disposed between the motor reduction gearing and the transmission. By being positioned between the reduction gearing and the transmission the clutch is on the low-speed side of the motor reduction gearing. This may be advantageous in efficiency and wear of the clutch mechanism.

The provision of the clutch between the motor reduction gearing and the transmission may be advantageous in its own right. Accordingly, from another aspect of the invention there is provided a drive apparatus for a vehicle which can be selectively driven by muscle power and/or motor power, the drive apparatus comprising: an input to receive muscle-power torque; a motor to provide motor-power torque; an output to provide power to at least one wheel of the vehicle; and a transmission couplable to the input and motor to transfer torque from the input and or motor to the output. The motor further comprises a motor reduction gearing and a clutch disposed between the motor reduction gearing and the transmission.

The clutch may comprise an annular clutch arrangement. The clutch may be disposed within a central cavity of the motor.

In embodiments the clutch may be a sprag clutch. The clutch may be a freewheel or overrunning clutch. The provision of an overrunning clutch enables smooth transition of power between human input and motor input. Additionally, the clutch may allow the transmission to be muscle-powered (using the pedals) without back-driving the motor (which would increase resistance and require additional effort).

The transmission in embodiments may comprise two parallel shaft assemblies. A first shaft assembly may comprise coaxial input and output shafts. A second shaft assembly may comprise a drive shaft and camshaft gear change actuator. An example of such a transmission is shown in International Patent Application W02020/174025.

The motor, the motor reduction gearing (and optionally the clutch) may be coaxial with the second shaft. The transmission may further comprise a first gearing stage coupling the input shaft of the first shaft assembly to the second shaft assembly and a second gearing stage coupling the second shaft assembly to the output shaft of the first shaft assembly. At least one of the gearing stages may be a multi-speed stage.

For example, the first gearing stage may be a two-speed gearing, and the second gearing stage may comprise an at least three-speed gearing.

In embodiments, the motor is a permanent magnet motor. In an embodiment in which the motor is a radial flux motor, the motor may be an inrunner motor. The stator may comprise a plurality of coils disposed adjacent to a housing of the motor.

The motor may comprise a housing. The housing may be connected to or integral with a housing of the drive apparatus.

The drive apparatus input may comprise a crank and pedals. The output may comprise a sprocket. The sprocket may drive a chain or belt connected to a wheel (or wheels) of the vehicle (for example via a sprocket on the wheel hub).

Whilst the invention has been described above, it extends to any inventive combination of the features set out above or in the following description or drawings.

Description of the Drawings

Embodiments of the invention may be performed in various ways, and embodiments thereof will now be described by way of example only, reference being made to the accompanying drawings, in which: Figure 1 shows an e-bike including a drive assembly in accordance with an embodiment; Figure 2 shows a cross sectional top view through a drive apparatus in accordance with an embodiment; Figure 3A and 38 respectively shows an exploded three-dimensional view and top view of a drive apparatus in accordance with an embodiment; Figure 4 shows a three-dimensional cross section through a drive apparatus in accordance with an embodiment; Figures SA, 5B and SC respectively show isolated front perspective, rear perspective and cross-sectional views of a motor for use in an embodiment; Figure 6A, 68, 6C and 6D respectively show an isolated end view from a first axial side, an isolated end view from the other axial side, an end view and a cross-sectional view of a motor reduction gearbox for use in an embodiment;

Detail Description of Embodiments

It may be noted that directional/orientational terms such as radial, circumferential, and axial may be used herein to refer to the general directions of the assembly or components thereof relative to their in-use configuration. It will be understood that such general directions are used with reference to the axis of the motor (which as will be described further below is coaxial with one of the axles of the transmission).

However, the skilled person will appreciate that (unless expressly indicated otherwise) such directions are used broadly and do not imply strict mathematical conformance with a particular orientation. Likewise, the use of such terminology does not exclude a component or feature having a non-circular or irregular form.

Figure 1 shows a "mid-drive" e-bike 100 which has a generally standard bicycle configuration having a pair of wheels 102, 103 supported on a frame 101 (in the illustrated example a mountain bike, but this is not essential). In such a mid-drive e-bike the drive apparatus 1 is mounted at the hub with the shaft 104 for the pedals extending through the drive apparatus 1. The drive apparatus 1 is provided with power from battery cells which may be mounted internally within the frame 101 of the bicycle 100. The bicycle 100 includes cranks 106 (on which pedals are mounted) that are rotated by the user to provide muscle-power torque. The drive apparatus 1 includes an electric motor 10 (as explained further below) which receives power from batteries to provide motor-power torque. The output from the drive apparatus 1 is provided via a sprocket gear 105 which is coaxial with the cranks 106 which drives the rear wheel 103 via a chain 107. In embodiments the drive apparatus 1 includes an internal multispeed gearbox 12 and, as such, the bicycle does not need to include additional external multi-speed gearing between the output sprocket 105 and the rear wheel 103.

Figure 2 shows a cross-section of the drive apparatus 1 of an embodiment. The drive apparatus 1 includes a transmission 12 and a motor 10 both within an environmentally sealed protective housing 18. The transmission 12 is couplable to the input from the shaft 104 of the cranks 106 (which it can be seen comprise an opposed pair of crank arms 106a, 106b) and to an output from the motor 10 to transfer torque from the crank shaft 106 and/or motor 10 to the output sprocket 105. The transmission 12 is arranged around two parallel shaft assemblies 14, 16. The first shaft 14 comprises coaxial input and output shafts -the input shaft being the crank shaft 106 and the output shaft being coupled to the output sprocket 105. The second shaft assembly 16 comprises a drive shaft and camshaft gear change actuator. The transmission 12 has a first gearing stage 12a (which may for example be a 2-speed gear stage) coupling the input shaft 106 of the first shaft 14 assembly to the second shaft assembly 16 and a second gearing stage 12b (which may for example be a 4-speed gear stage) coupling the second shaft assembly 16 to the output shaft (and therefore the sprocket 105) of the first shaft assembly 14. Whilst other transmission arrangements may be available this arrangement provides a compact, lightweight, and durable arrangement. The gear shifting of the transmission may be electronically controlled and may, for example, utilise the transmission arrangement described in the Applicant's prior International Patent Application W02020/174025. The motor 10 is coaxially arranged with the second shaft assembly 16 and will be described in further detail below.

It may be appreciated that the function of the transmission gearing 12 is separate to that of the motor reduction gearing 40 (explained further below). The motor reduction gearing 40 reduces the output speed of the motor 10 (with a corresponding increase in torque) to enable the motor 10 operates at an efficient speed whilst providing an output (to the transmission 12) at a required speed and torque. The gearing of the transmission 12 provides control of the relative speed between the inputs to the transmission and the output sprocket 105 (such that it controls the speed of the rotation of the rear wheel 10). The transmission 12 therefore provides a gearing which is used for both muscle-power torque and motor-power torque.

With reference to figures 3 to 5, the configuration of the motor 10 in accordance with embodiments will now be discussed further. The motor 10 has an annular configuration (best seen in the isolated views of figure 5) in which the rotor 20 and stator 30 both have an annular configuration and are arranged at an outer radial portion of the motor to provide a central cavity 19 which is open on one side. The stator assembly 30 comprises an array of stator coils 32 mounted to a stator body 34.

The coils 34 are circumferentially distributed and surround the rotor assembly 20. As the rotor 20 is internal to the stator 30 it may be noted that the motor 10 is classed as an "inrunner" motor. The rotor assembly 20 comprises a rotor support having a hub 22 at its centre and a disc shaped support face 24 extending from the hub 22. The body 26 of the rotor is a tubular section extending axially away from the face 24 and carrying a plurality of permanent magnets 28 which are embedded into the body 26 as a circumferentially distributed array. When assembled into the drive assembly 1, the open side of the central cavity 19 is axially inward (and faces the transmission 12) and the support face 24 of the rotor is on the axially outward side of the motor 10. As such the cavity 19 provides an enclosed space within the motor.

Whilst the illustrated motor 10 is a radial flux motor the skilled person will appreciate that it could be easily modified to provide an axial flux motor in which the rotor magnets and stator coils are arranged in a parallel axially adjacent configuration. Such a motor configuration could still provide an annular motor with a central cavity as shown the embodiment.

The rotor 20 of the motor 10 is rotatably supported on a motor bearing 35. The motor bearing extends from the hub 22 of the rotor assembly 20 on the opposing side to the body 26 of the rotor. As such, the motor bearing 35 provides a cantilever support arrangement for the rotor 20, in which the bearing 35 is axially outside of the rotor 20. The motor bearing in the illustrated example comprises a double row angular contact bearing including first and second sets of rolling elements 37a, 37b. The bearing 35 is mounted externally around a radially outwardly facing bearing seat 23 formed by the hub 22 of the rotor support. The use of an external bearing seat 23 enables a central bore 21 of the hub 22 to be unobstructed. The inner race 38a of the bearing 30 is mounted to the bearing seat 23 and the outer race 38b is supported on a radially inward facing bearing seat formed in the housing 18 of the drive assembly 1 (as shown in figure 2). This arrangement also provides the advantage of ensures that the motor bearing 35 can be made easily accessible (for example for lubrication) and the housing may, for example include a removable cover plate 18c for ease of access to the motor bearing.

Advantageously, the cavity 19 defined within the motor is utilised to provide a motor reduction gearing 40. The motor reduction gearing is shown in isolation in figures 6A to 6D. Embodiments use a planetary gearset (also known as an epicyclic gearset) which enables a relatively high reduction ratio in a small space, and which has only a narrow axial extent such that it can be fully fitted into the cavity 19. The planetary gearbox 40 is surrounded by a ring gear 41 fixed by a plurality of screws 42 to an internal flange of the housing 18 (and therefore fixed relative to the stator assembly 30). The ring gear 41 is radially adjacent to the inner face of the rotor assembly 20 such that it separates the motor 10 from the motor reduction gearing 40. It will be appreciated that the planetary gearset 40 could have a number of different configurations depending upon the reduction ratio required.

In the illustrated embodiment the planetary gearset 40 is a compound, two-stage, gearing. The first stage of the gearing is the high-speed stage 43. The high-speed stage 43 includes a high-speed sun gear 44 which is coupled to the output of the motor 10. The shaft of the sun gear 44 is coupled to the rotor assembly 20 via the bore 21 of the hub 22. The sun gear 44 drives a set of planet gears 45 which rotate on the ring gear 41 and result in the rotation of a high-speed planet carrier 46. The high-speed carrier 46 provides the input to the second, low speed, stage 50 of the gearset 40. The low-speed input is a sun gear 51 which extends from the opposite axial side of the high-speed carrier 56. The sun gear 51 drives a second set of planet gears 52 which also engage and rotate on the ring gear 41. A low-speed planet carrier 53, supported on a bearing 54, is driven by the planet gears 52 and provides an output SS from the motor reduction gearset 40.

In embodiments the output 55 of the gearset 40 is formed as an annular flange which projects axially away from the motor reduction gearset 40 on the transmission facing side of the low-speed planet carrier 53. The output 55 is coaxial with the motor 10 and the transmission 12. The radially inner side of the output SS is provided with a thrust surface 56 for transmission of torque from the motor reduction gearing 40 to the transmission 12.

In embodiments, a clutch 60 is provided between the motor 10 and the transmission 12. The clutch 60 is best seen in the exploded views of Figure 3 and cross section of figure 4. The clutch 60 has an annular configuration and is arranged between the output 55 of the motor reduction gearing 40 and an input to the transmission 12. The annular configuration of the clutch 60 provides a compact arrangement which does not require additional axial space. It is particularly useful for the clutch 60 to be an automatic one-way clutch which allows the transmission 12 to overrun the motor output for example when the motor is switched off or when the human power causes the speed of the bicycle to exceed the motor output. The clutch 60 can be a sprag clutch which includes a number of asymmetrically shaped sprags 62 which engage when the output 55 is driving the transmission but tilt into a non-engaged position if the relative speed of the transmission exceeds that of the output 55.

Although the invention has been described above with reference to preferred embodiments, it will be appreciated that various changes or modification may be made without departing from the scope of the invention as defined in the appended claims. For example, whilst the illustrated example is a bicycle other configurations of "e-bike" are increasingly available. Embodiments of the invention may, for example, be used on a three or four wheeled vehicle which can be selectively driven by muscle power and/or motor power and the configuration of the drive apparatus may vary accordingly (for example pedals for inputting human torque could be indirectly coupled to the input of the drive apparatus). Equally it will be appreciated that inclusive cycling products are available such as handcycles in which the human input is via hand operated pedals rather than conventional pedals and embodiments may be equally applicable to such vehicles.

Claims

Claims 1. A drive apparatus for a vehicle which can be selectively driven by muscle power and/or motor power the drive apparatus comprising: an input to receive muscle-power torque; a motor to provide motor-power torque; an output to provide power to at least one wheel of the vehicle; and a transmission couplable to the input and motor to transfer torque from the input and/or motor to the output; wherein the motor has an annular configuration, comprising a stator assembly and rotor assembly arranged around a radially external portion of the motor and defining a central cavity within the motor; and the apparatus further comprising a motor reduction gearing disposed within the central cavity.
2. The drive apparatus of claim 1, wherein the motor reduction gearing comprises a planetary gearset.
3. The drive apparatus of claim 2, wherein the planetary gearset is a compound planetary gearset.
4. The drive apparatus of claim 2 or 3, wherein the planetary gearset comprises: an internal gear fixed with respect to the stator assembly, and an input gear fixed with respect to the rotor assembly.
5. The drive apparatus of claim 4, wherein the rotor assembly is radially internal to the stator assembly and wherein the ring gear is adjacent a radially internal surface of the rotor assembly.
6. The drive apparatus of any preceding claim, wherein the rotor assembly is supported by a motor bearing disposed at one axial side of the motor such that the motor bearing provides a cantilever support to the rotor.
7. The drive apparatus of claim 6, wherein the motor further comprises a motor housing, the stator assembly being fixed relative to the housing and the motor bearing rotatably mounts the rotor assembly relative to the motor housing.
8. A drive apparatus for a vehicle which can be selectively driven by muscle power and/or motor power, the drive apparatus comprising: an input to receive muscle-power torque; a motor to provide motor-power torque; an output to provide power to at least one wheel of the vehicle; and a transmission couplable to the input and motor to transfer torque from the input and or motor to the output; wherein the motor comprises: a stator assembly fixed relative to a motor housing, a rotor assembly rotatably mounted relative to the motor housing, and a motor bearing supporting the rotor assembly; and wherein the rotor bearing is disposed at one axial side of the motor and provides a cantilever support to the rotor.
9. The drive apparatus of claims 7 or 8, wherein the rotor bearing is axially outside of the stator and rotor.
10. The drive apparatus of claim 7, 8 or 9, wherein the rotor assembly further comprises a rotor support comprising: an axially extending rim for supporting the rotor, and a hub connected to the motor bearing.
11. The drive apparatus of claim 10, wherein the hub and rotor extend from the opposing axial sides of the support face.
The drive apparatus of claim 10 or 11, wherein the support face comprises a solid disk.
The drive apparatus of any of claims 11 to 12, wherein the hub comprises an external seat for the motor bearing.
The drive apparatus of claim 13, wherein the hub further comprises an internal bore, the bore receiving an input gear for a motor reduction gearing and wherein the input gear is mounted to the opposing axial side of the support face from the external seat.
The drive apparatus of any of claims 7 to 14, wherein the motor bearing comprises a double row angular contact bearing.
The drive apparatus of any preceding claim, wherein the apparatus further comprises a clutch between the motor and transmission.
The drive apparatus of claim 16, wherein the clutch is disposed between a motor reduction gearing and the transmission.
A drive apparatus for a vehicle which can be selectively driven by muscle power and/or motor power, the drive apparatus comprising: an input to receive muscle-power torque; a motor to provide motor-power torque; an output to provide power to at least one wheel of the vehicle; and a transmission couplable to the input and motor to transfer torque from the input and or motor to the output; wherein the motor further comprises a motor reduction gearing and a clutch disposed between the motor reduction gearing and the transmission. 12. 13. 14. 15. 16. 17. 18.
19. The drive apparatus of claim 17 or 18, wherein the clutch comprises an annular clutch arrangement and is disposed within a central cavity of the motor.
20. The drive apparatus of any of claims 17 to 19, wherein the clutch is a sprag clutch.
21. The drive apparatus of any preceding claim wherein the transmission comprises two parallel shaft assemblies, comprising: a first shaft assembly comprises coaxial input and output shafts; and a second shaft assembly comprises a drive shaft and camshaft gear change actuator; and wherein the motor, the motor reduction gearing, and optionally the clutch, are coaxial with the second shaft.
22. The drive apparatus of claim 21, wherein the transmission further comprises: a first gearing stage coupling the input shaft of the first shaft assembly to the second shaft assembly and a second gearing stage coupling the second shaft assembly to the output shaft of the first shaft assembly.
23. The drive apparatus of claim 22, wherein at least one of the gearing stages is a multi-speed stage.
24. The drive apparatus of any preceding claim, wherein the motor is a permanent magnet motor.
25. The drive apparatus of claim 24, wherein the motor is an inrunner motor and the stator comprises a plurality of coils disposed adjacent to a housing of the motor.
26. The drive apparatus of any preceding claim, wherein the motor is a radial flux motor.
27. The drive apparatus of any preceding claim wherein the motor comprises a housing which is connected to or integral with a housing of the drive apparatus.
28. An e-bike comprising a drive apparatus of any preceding claim, wherein the drive apparatus input comprises a crank and the output comprises a sprocket.