Transmission system for a human powered vehicle, or light electric vehicle

Abstract

The disclosure relates to a transmission system for a human powered vehicle, or light electric vehicle, comprising a crank housing, a crank axle, a front sprocket, and a transmission having an input connected to the crank axle and an output connected to the front sprocket. The transmission comprises an axle, offset and parallel to the crank axle, configured to be non-rotatably fixed or fixable to the crank housing, at least one sun gear rotatably mounted around the axle, and at least one clutch mechanism configured for in a first mode selectively preventing rotation of the at least one sun gear in a first rotational direction about the axle, and in a second mode selectively preventing rotation of the at least one sun gear in an opposite second rotational direction about the axle.

Description

[0001] Title: Transmission system for a human powered vehicle, or light electric vehicle

[0002] FIELD

[0003] The invention relates to a transmission system for a human powered vehicle, or light electric vehicle, such as for a bicycle.

[0004] BACKGROUND

[0005] Bicycle transmission systems are known per se. Many bicycle transmission systems are configured to provide a plurality of different transmission ratios.

[0006] A known class of bicycle transmission systems is based on a chain connecting a front chain wheel and a rear sprocket, wherein the rear sprocket is one of a plurality of rear sprockets, e.g. combined in a cassette, and a rear derailleur is provided for providing selectable different transmission ratios. Alternatively, or additionally, the front chain wheel is one of a plurality of front chain wheels, and a front derailleur is provided for providing selectable different transmission ratios.

[0007] Another known class of bicycle transmission systems uses encased transmissions. Such encased transmissions can e.g. be internally geared bicycle hub transmissions. Such encased transmissions can be internally geared crank units. The encased transmissions can be used in combination with a derailleur system.

[0008] Present encased transmission systems can have the disadvantage of having few different transmission ratios. Present encased transmission systems with more transmission ratios often have the disadvantage of being heavy.

[0009] SUMMARY

[0010] It is an object to propose an improved transmission system for a human powered vehicle or light electric vehicle, such as a bicycle. It will be appreciated that the transmission system can be used in various vehicles, such as bicycles or other human powered vehicles or light electric vehicles. It is an object to provide an improved crank transmission system for a human powered vehicle or light electric vehicle, such as a bicycle.

[0011] According to a first aspect is provided a transmission system for a human powered vehicle, or light electric vehicle, such as a bicycle. The transmission system comprises a crank housing, a crank axle and a front sprocket. The transmission system comprises a transmission having an input connected to the crank axle and an output connected to the front sprocket. The transmission can be configured for providing a speed reduction and / or speed increase between an input and output of the transmission. The transmission comprises an axle. The axle is offset and parallel to the crank axle. The axle is configured to be fixed against rotation. The axle can e.g. be non-rotatably fixed or fixable to the crank housing. The transmission comprises at least one sun gear rotatably mounted around the axle. The transmission comprises at least one clutch mechanism configured for in a first mode selectively preventing rotation of the at least one sun gear in a first rotational direction about the axle, and in a second mode selectively preventing rotation of the at least one sun gear in an opposite second rotational direction about the axle. The first mode is herein also referred to as first disposition. The second mode is herein also referred to a second disposition. It will be appreciated that it is possible that in the first mode the at least one sun gear can freely rotate in the second rotational direction about the axle. It will be appreciated that it is possible that in the second mode the at least one sun gear can freely rotate in the first rotational direction about the axle.

[0012] Optionally, the at least one clutch mechanism is configured for in a third mode allowing the sun gear to rotate freely around the axle in at least one or, preferably, both rotational directions. The third mode is herein also referred to as third disposition. Optionally, the crank axle drives the input of the transmission via a geared connection or via an endless drive member, such as a belt or chain. Thus, the transmission system can be configured such that the crank axle is connected to the input of the transmission via a first geared connection or via a first endless drive member, such as a belt or chain, for transferring torque from the crank axle to the input of the transmission. Thereto, the crank axle can be provided with a first gear or pully, and the input of the transmission can be provided with a second gear or pully.

[0013] Optionally, the crank axle drives the input of the transmission via a speed increasing transmission. The speed increase can have a ratio of between 1:1 or 2:1. Hence, e.g. a speed-increasing geared connection or a speed-increasing endless drive member connection can be provided between the crank axle and the input of the transmission, for instance having a transmission ratio between 1:1 and 2:1.

[0014] Optionally, the front sprocket is rotatable coaxially with the axle. Hence, the front sprocket is offset relative to the crank axle. Hence, the output of the transmission can directly, or via a freewheel, drive the front sprocket.

[0015] Optionally, the front sprocket is rotatable coaxially with the crank axle. Hence, the front sprocket is offset relative to the axle of the transmission. The output of the transmission can drive the front sprocket via a second geared connection or via a second endless drive member, such as a belt or chain. Thus, the transmission system can be configured such that the output of the transmission is connected to the front sprocket via a geared connection or via an endless drive member, such as a belt or chain, for transferring torque from the output of the transmission to the front sprocket. Thereto, the output of the transmission can be provided with a third gear or pully, and the front sprocket can be provided with a fourth gear or pully.

[0016] Optionally, the transmission system comprises an electric propulsion motor, such as for assisting in propulsion, e.g. in addition to muscle power. The electric motor can concentric with the crank axle. The electric motor is offset and parallel to the crank axle. The electric motor can drive the input of the transmission, e.g. via the first geared connection or via the first endless drive member. Thereto, the electric motor can drive the crank axle or a gear or pully, such as the first gear or pully, mounted on the crank axle, e.g. via a freewheel. The electric motor offset and parallel to the crank axle can drive the crank axle or the gear or pully, such as the first gear or pully, mounted on the crank axle, e.g. via a freewheel, e.g. via an intervening gear.

[0017] Optionally, the at least one clutch mechanism is configured to be actively electronically actuated to select the respective mode of the clutch mechanism.

[0018] Optionally, the at least one sun gear comprises at least two or at least three sun gears rotatably mounted around the axle. The at least one clutch mechanism can comprises a respective clutch mechanism associated with each of the sun gears for selecting at least the first and second modes. Hence, each sun gear can have an associated clutch mechanism. Each sun gear can be associated with one of the clutch mechanisms and each clutch mechanism can be associated with one of the sun gears.

[0019] Optionally, the at least two or at least three sun gears have different diameters and are connected by at last one stepped planet gear rotatably mounted inside a carrier. The bicycle transmission can comprise a ring gear meshing with one of the planets of the stepped planet gear(s).

[0020] Optionally, an input of the transmission is connectable either to the ring gear or to the carrier of the planetary gear set. The transmission can be configured to selectively transfer torque from the input of the transmission to the ring gear or to the carrier of the planetary gear set. The input of the transmission can be connected to the ring gear via a one-way clutch or one-way bearing. The input of the transmission can be connected to the carrier via a first actuatable clutch mechanism. Optionally, an output of the transmission is connectable either to the ring gear or to the carrier of the planetary gear set. The transmission can be configured to selectively transfer torque from the ring gear or the carrier of the planetary gear set to the output of the transmission. The carrier can be connected to the output of the transmission via a one-way clutch or one-way bearing. The ring gear can be connected to the output of the transmission via a second actuatable clutch mechanism. The first actuatable clutch and the second actuatable clutch can be part of a switching mechanism. This allows to selectively connect the input to the carrier and the ring gear to the output, or connect the input to the ring gear and the carrier to the output. Hence, the number of useable transmission ratios can be increased. It is also possible to connect the input and the output both to the carrier or both to the ring gear to provide a unity transmission ratio.

[0021] Optionally, the or each clutch mechanism comprises a first pawl and a second pawl configured to be actuated by a camshaft, such that the first pawl is selectively in engagement with the respective sun gear in the first mode, and the second pawl is selectively in engagement with the respective sun gear in the second mode.

[0022] Optionally, at least one of the clutch mechanisms comprises a passive one-way clutch or one-way bearing to create a first or second mode.

[0023] Optionally the camshaft is mounted inside the axle for actuating the at least one clutch mechanism. Optionally, the camshaft mounted inside the axle is configured for actuating the respective clutch mechanisms of the at least one clutch mechanism. Hence, the camshaft can actuate a plurality of clutch mechanisms. Optionally, the camshaft mounted inside the axle is configured for actuating the first and second actuatable clutch mechanisms. Hence, the camshaft can actuate the connecting of the input and output of the transmission to the ring gear and carrier as described above.

[0024] Optionally, the at least one clutch mechanism is designed such that it can disengage from a torque loaded sun gear, in at least one direction. Optionally, the pawls are designed such that they disengage under torque load on the sun gear, and that the camshaft is configured to allow to prevent disengagement.

[0025] Optionally, between the camshaft and the pawls there is a roller bearing.

[0026] Optionally, between the camshaft and axle there is at least one roller bearing.

[0027] Optionally, the transmission system further comprising a further transmission in the housing and in series with the transmission. A transmission ratio step size between successive transmission ratios of the further transmission can be smaller than a transmission ratio step size between successive transmission ratios of the transmission.

[0028] Optionally, the further transmission comprises a pully driven by the crank axle; a planet carrier connected to the pully; one or more stepped planet gears; a sun gear meshing with a larger portion of the stepped planet gears; a ring gear meshing with a smaller portion of the stepped planet gears; a freewheel between the pully or planet carrier and the input of the transmission; and a clutch mechanism configured for selectively preventing rotation of the sun gear of the further transmission in at least one rotational direction.

[0029] According to a second aspect is provided a transmission system for a human powered vehicle, or light electric vehicle, such as a bicycle. The transmission system comprises a crank housing, a crank axle and a front sprocket. The transmission system comprises a transmission having an input connected to the crank axle and an output connected to the front sprocket. The transmission comprises an axle. The axle is offset and parallel to the crank axle.. The axle is configured to be fixed against rotation. The axle can e.g. be non-rotatably fixed or fixable to the crank housing. The transmission comprises at least one sun gear rotatably mounted around the axle. The transmission comprises at least one clutch mechanism configured for in a first mode selectively preventing rotation of the at least one sun gear in a first rotational direction about the axle, and in a second mode decoupling the sun gear. The first mode is herein also referred to as first disposition. In the second mode the sun gear can be decoupled from the axle, such as being free to rotate in two directions. The second mode is herein also referred to a second disposition. It will be appreciated that it is possible that in the first mode the at least one sun gear can freely rotate in the second rotational direction about the axle. It will be appreciated that it is possible that in the second mode the at least one sun gear can freely rotate in both the first rotational direction and the second rotational direction about the axle.

[0030] The features and options described above in view of the transmission system of the first aspect also apply to the transmission system of the second aspect.

[0031] According to a third aspect is provided a human powered vehicle or light electric vehicle, such as a bicycle, comprising a transmission system as described herein.

[0032] It will be appreciated that any of the aspects, features and options described herein can be combined. Any of the aspects, features and options described in view of the transmission systems apply equally to the human powered vehicle or light electric vehicle, such as the bicycle.

[0033] BRIEF DESCRIPTION OF THE DRAWINGS

[0034] Embodiments of the present invention will now be described in detail with reference to the accompanying drawings in which:

[0035] Figure 1 shows a schematic example of a transmission; Figures 2A-2C show an example of an actuator;

[0036] Figures 3A-3I show an example of a sequence of gear shifting; Figure 4A shows an example of a freewheel clutch;

[0037] Figure 4B shows an example of an actuatable bidirectional clutch mechanism; Figures 5A and 5B show examples of an actuatable clutch of a shifting mechanism;

[0038] Figures 6A and 6B show an example of an actuator;

[0039] Figure 7 A shows an example of a spring;

[0040] Figure 7B shows an example of a clutch;

[0041] Figures 8A and 8B show an example of a selector;

[0042] Figures 9A and 9B show an example of a selector;

[0043] Figure 9C shows an example of a bush;

[0044] Figures 10A, 10B and 10C show an example of a selector;

[0045] Figure 11 shows an example of a transmission system;

[0046] Figures 12A and 12B show an example of a transmission system;

[0047] Figures 13A and 13B show an example of a transmission system; Figures 14A and 14B show an example of a transmission system; Figures 15A and 15B show an example of a transmission system; Figure 16 shows an example of a transmission system; and Figure 17 shows an example of a bicycle.

[0048] DETAILED DESCRIPTION

[0049] Figure 1 shows a schematic example of a transmission 100 for use in a transmission system 1000 for a human powered vehicle or light electric vehicle, such as bicycle. The transmission 100 includes a transmission input I and a transmission output O. The transmission 100 here is arranged for providing a speed reduction and / or speed increase between the input I and the output O.

[0050] The transmission 100 here comprises a planetary gear set 100, arranged for providing a speed reduction and / or speed increase between the input I and the output O. The planetary gear set may be housed in a, e.g. rotatable, housing 51. The planetary gear set 100 comprises a ring gear 128 and a planet carrier 126 carrying one or more planet gears 127. The planet carrier 126 in this example carries one or more stepped planet gears 127 having multiple planet gear parts 127i having different planet radii. In this example, the stepped planet gear has four planet gear parts 127a, 127b, 127c, 127d. The ring gear 128 meshes with one of the different planet radii 127i. Here, the ring gear 128 meshes with the third planet gear part 127c. The planetary gear set 100 also comprises a plurality of different sun gears 129i. The plurality of sun gears respectively mesh with the plurality of different planet radii 127i. Here, the plurality of sun gears comprises four sun gears 129a, 129b, 129c, 129d. Notice that in this example, the sun gears 129i are positioned with ever increasing diameters from one end of the axle 30 to the other end of the axle. This can be beneficial in combination with an ever increasing axle 30 diameter corresponding to the increasing sun gear diameter as described below. The same applies to the planet gear parts 127i. It is, however, also possible to position the sun gear 129d with the smallest diameter between two sun gears of larger diameter. This can provide a compact build. Similarly, positioning the planet gear parts 127d with the largest diameter between two planet gear parts of smaller diameter can provide a compact build.

[0051] The sun gears 129i are rotatably arranged about the stationary axle 30. The stationary axle 30 may be mounted to a housing of a crank gearbox as described below, for supporting torque thereon. Therefore, the axle may be mounted fixed against rotation to the frame.

[0052] The transmission 100 comprises a switching mechanism. The switching mechanism comprises a first actuatable clutch mechanism Si and a second actuatable clutch mechanism S2. the first actuatable clutch mechanism Si is arranged in a transmission path between the transmission input I and the ring gear 128. The second actuatable clutch mechanism S2 is arranged in a transmission path between the planet carrier 126 and the transmission output O. The transmission 100 also comprises a first freewheel 11 in a transmission path between the transmission input I and the planet carrier 126. The first freewheel 11 is hence parallel to the first actuatable clutch mechanism Si. The transmission 100 also comprises a second freewheel 12 in a transmission path between the ring gear 128 and the transmission output O. The second freewheel 12 is hence parallel to the second actuatable clutch mechanism S2.

[0053] The first switching mechanism is configured for selectively being in a first state or a second state.

[0054] In the first state of the switching mechanism, both the first and the second actuatable clutch mechanisms Si, S2 are in a clutched state. Torque can accordingly be transmitted in the first state from the transmission input I via the first actuatable clutch mechanism Si to the ring gear 128 and from the planet carrier 126 via the second actuatable clutch mechanism S2 to the transmission output O. The first freewheel 11 and the second freewheel 12 are overrun in the first state. In the first state, the planetary gear set 100 provides a speed reduction from the ring gear 128 to the planet carrier 126 in accordance with the relative dimensions of the cooperating rotational members of the planetary gear set 100.

[0055] In the second state, both the first and the second actuatable clutch mechanisms Si, S2 are in an unclutched state. Torque can accordingly be transmitted in the second state from the transmission input I via the first freewheel 11 to the planet carrier 126 and from the ring gear 128 via the second freewheel 12 to the transmission output O. In this state, the planetary gear set 100 provides a speed increase from the planet carrier 126 to the ring gear 128 in accordance with the relative dimensions of the cooperating rotational members of the planetary gear set 100.

[0056] Here, the transmission 100 also comprises an optional third freewheel 13 arranged in series with the first actuatable clutch Si, and an optional fourth freewheel 14 arranged in series with the second actuatable clutch S2. The third and fourth freewheels 13 and 14 can prevent lockup of the transmission 100 if the vehicle were to be rolled backwards.

[0057] The switching mechanism enables for reversing a transmission path through the planetary gear set 100, e.g. from ring gear 128 to carrier 126 or vice versa, to effectively increase the range of transmission ratios of the transmission 100 as whole. In the first state of the switching mechanism, the transmission 1000 operates according to an underdrive transmission ratio, reducing the rotational speed from the input I to the output O. In the second state of the switching mechanism, the transmission 1000 operates according to an overdrive transmission ratio, increasing the rotational speed from the input I to the output O.

[0058] The switching mechanism may also be arranged for selectively being in a third state. In the third state, the first actuatable clutch mechanism S 1 may be in its clutched state, while the second actuatable clutch mechanism S2 is in its unclutched state, or vice versa. In the third state, the transmission input I and the transmission output O are coupled to the same rotational member of the planetary gear set 100, e.g. both to the planet carrier 126 or both to the ring gear 128. In the third state, the transmission may be operable according to a unitary transmission ratio, e.g. a transmission ratio of 1:1.

[0059] The transmission 100 further comprises a clutch mechanism. The clutch mechanism is arranged for selectively clutching a selective one of the plurality of sun gears 129i to the stationary axle 30. Hereto, the clutch mechanism comprises a plurality of actuatable bidirectional clutch mechanisms Ci. In this example, the plurality of actuatable bidirectional clutch mechanisms Ci comprises four actuatable bidirectional clutch mechanisms Cl, C2, C3, C4. Each actuatable bidirectional clutch mechanism Ci is associated with a respective sun gear 129i, for clutching the associated sun gear 129i to the stationary axle 30 in a selective one of two opposing rotation directions. Each actuatable bidirectional clutch mechanism Ci is arranged for being selectively in a first disposition or a second disposition. In the first disposition, the actuatable bidirectional clutch mechanism Ci prevents rotation of the respective sun gear 129i in the first rotation direction about the stationary axle 30. Herein, preventing rotation of the respective sun gear 129i in the first rotation direction about the stationary axle 30 is also referred to as braking the respective sun gear 129i in the first rotation direction. In the second disposition, the actuatable bidirectional clutch mechanism C2.i prevents rotation of the respective sun gear 129i in the second rotation direction about the stationary axle 30. Herein, preventing rotation of the respective sun gear 129i in the second rotation direction about the stationary axle 30 is also referred to as braking the respective sun gear 129i in the second rotation direction. The direction in which a sun gear 129i is to be braked is dependent on the state of the switching mechanism. For example, if the switching mechanism is in its first state, a selective one of the actuatable bidirectional clutch mechanisms Ci may prevent rotation of a respective sun gear 129a in the second rotational direction, whereas if the switching mechanism is in its second state, a selective one of the actuatable bidirectional clutch mechanisms Ci may prevent rotation of a respective sun gear 129a in the first rotational direction.

[0060] When the transmission input I is driven in the first rotational direction R1 about the stationary axle 30, while the switching mechanism is in the first state, the ring gear 128 is also driven in the first rotational direction, and via the stepped planet gear 127, a rotational force is induced on the sun gears 129i in the second, reverse, rotational direction. By braking a selective one of the sun gears 129i in the second rotational direction with a corresponding one of the clutch mechanisms Ci, torque can be transmitted from the ring gear 128 to the planet carrier 126, according to an underdrive transmission ratio. When the transmission input I is driven in the first rotational direction about the stationary axle 30, while the switching mechanism is in the second state however, the planet carrier 126 is also driven in the first rotational direction, and via the stepped planet gear 127, a rotational force is induced on the sun gears 129i in the first rotational direction. By braking a selective one of the sun gears 129i in the first rotational direction with a corresponding one of the clutch mechanisms Ci, torque can be transmitted from the planet carrier 126 to the ring gear 128 according to an overdrive transmission ratio. In each of the first and second dispositions, the actuatable bidirectional clutch mechanisms Ci may be arranged to prevent rotation of the sun gear 129 in one direction, while allowing rotation of the sun gear in the opposite rotation direction, e.g. by freewheeling. Hence, in the first disposition, the actuatable bidirectional clutch mechanism Ci may be configured for allowing freewheeling of the sun gear 129i in the second rotational direction while preventing rotation of that sun gear 129i in the first rotational direction. Also, in the second disposition, the actuatable bidirectional clutch mechanism Ci may be configured for allowing freewheeling of the sun gear 129i in the first rotational direction while preventing rotation of that sun gear 129i in the second rotational direction.

[0061] One or more of the actuatable bidirectional clutch mechanisms Ci may also selectively be adjusted to a third disposition. In the third disposition, the actuatable bidirectional clutch mechanism Ci may allow free rotation of the respective sun gear 129i in both rotational directions about the stationary axle 30. For instance, while one of the actuatable bidirectional clutch mechanisms Ci is in the first disposition or the second disposition, other ones of the actuatable bidirectional clutch mechanisms can be in the third disposition.

[0062] One or more, e.g. all, of the actuatable bidirectional clutch mechanisms Ci may be configured to be adjustable to be in the third disposition, if the switching mechanism is in its third state, for allowing the ring gear 128 and the planet carrier 126 to corotate about the stationary axle 30. This way, the transmission 100 may provide a unitary transmission ratio between the input I and output O. If the switching mechanism is in its third state, one or more of the actuatable bidirectional clutch mechanisms Ci may also be adjusted to be in the second disposition, for allowing the ring gear 128 and the planet carrier 126 to corotate about the stationary axle 30 in the first rotational direction.

[0063] It is possible that one (or more) of the actuatable bidirectional clutch mechanisms Ci is a biased actuatable bidirectional clutch mechanism configured to be in the second disposition by default and configured to be actively actuated to the first disposition. The biased actuatable bidirectional clutch mechanism may be configured not to have a third disposition. The biased actuatable bidirectional clutch mechanism can be used to prevent that all actuatable bidirectional clutch mechanisms are in the third disposition while the switching mechanism is in the first or second state, which could lead to a state in which no torque is transferred by the transmission. Also, the biased actuatable bidirectional clutch mechanism Ci may be configured for allowing freewheeling of the sun gear 129i in the first rotational direction while preventing rotation of that sun gear 129i in the second rotational direction. It is also possible that one (or more) of the actuatable bidirectional clutch mechanisms Ci is a biased actuatable bidirectional clutch mechanism configured to be in the first disposition by default and configured to be actively actuated to the second disposition.

[0064] In figure 1 the planetary gear set 100 comprises four sun gears 129a, 129b, 129c, 129d meshing with four respective planet radii 127a, 127b, 127c, 127d of the stepped planet gear 127. Also, the plurality of clutch mechanisms Ci comprises four actuatable bidirectional clutch mechanisms Cl, C2, C3, C4, arranged for selectively clutching the respective sun gears 129a, 129b, 129c, 129d to the stationary axle 30. An eight speed or nine- speed transmission 1000 can be hence be obtained. Exemplary clutch states of the switching mechanism (first actuatable clutch mechanism S 1 and a second actuatable clutch mechanism S2) and clutch mechanism (actuatable bidirectional clutch mechanisms Cl, C2, C3, C4) for the nine-speed transmission 100 are summarized in table 1.

[0065] Exemplary clutch states of the switching mechanism (first actuatable clutch mechanism Si and a second actuatable clutch mechanism S2) and clutch mechanism (actuatable bidirectional clutch mechanisms Cl, C2, C3, C4) for the nine-speed transmission 100 are summarized in table 2 for a situation in which the first actuatable bidirectional clutch mechanism Cl is a biased actuatable bidirectional clutch mechanism.

[0066] In tables 1 and 2, the transmission 100 is operable according to a unitary transmission ratio, but this gear may optionally be omitted. The shifting mechanism may for example not include the third state, but may be adjusted only between the first state and the second state. Without the unitary gear, the first actuatable clutch S 1 and the second actuatable clutch S2 can be actuated in synchrony with each other, switching both clutches Si, S2 simultaneously between their clutched and their unclutched state. This may simplify the actuation construction. A benefit of the unitary gear is an increase in transmission ratio range. Also, with the unitary gear, each upshift or downshift to a next higher or lower gear may involve only shifting one the first and second actuatable clutch mechanisms Si, S2.

[0067] In tables 1 and 2, the actuatable bidirectional clutch mechanisms also include the optional third disposition. Instead, the actuatable bidirectional clutch mechanisms Ci may be adjusted between only the first disposition and the second disposition. The transmission of figure 1 can also be used for providing a five-speed transmission. For a five-speed reduction transmission, the clutch mechanisms Cl, C2, C3 and C4 may omit the first disposition, i.e. provide the second disposition and the third disposition. For a five-speed speed-increase transmission, the clutch mechanisms Cl, C2, C3 and C4 may omit the second disposition, i.e. provide the first disposition and the third disposition. Also for the five-speed transmission, one of the clutches Cl, C2, C3, C4 (e.g. Cl) may be a freewheel.

[0068] In the example of figure 1, the axle 30 has a central axis A. As further described below, the axle 30 can be a layshaft in a crank transmission. In this example, an actuator for actuating the clutch mechanisms Cl, C2, C3, C4 is mounted inside the axle 30. In this example, the actuator is an electromechanical actuator. The electromechanical actuator comprises an electric motor 32 in this example. The actuator in this example comprises a camshaft 34 mounted inside the axle 30 for actuating the clutch mechanisms Cl, C2, C3, C4. The electromechanical actuator 32 is configured for rotating the camshaft 34 inside the axis 30.

[0069] Figure 2A shows an example of the actuator. In figure 2A the electromechanical actuator 32 and the camshaft 34 are visible. Here, the camshaft comprises a plurality of cams Ni, in particular, six cams N 1, N2, N3, N4, N5, N6. Here, the camshaft 34 comprises a single notch profile for actuating the plurality of clutch mechanisms. The singe notch profile is formed by the plurality of cams Ni, extending along an axial direction of the camshaft 34. In this example, the singe notch profile, e.g. the plurality of cams Ni, extends along a line parallel to a central axial axis A of the camshaft 34. Figure 2B shows the actuator of figure 2A with pawls Pi, in particular pawls Pl, P2A, P2B, P3A, P3B, P4A, P4B, shown. Each clutch mechanism Cl, C2, C3, C4 comprises one or more pawls Pi configured to be actuated by the camshaft 34. In this example, the second C2, third C3 and fourth C4 clutch mechanisms each comprise a first pawl PiA and a second pawl PiB configured to be actuated by the camshaft 34, such that the first pawl PiA is selectively in engagement with the respective sun gear 129i in the first mode, and the second pawl PiB is selectively in engagement with the respective sun gear 129i in the second mode.

[0070] Each pawl Pi in this example comprises two support surfaces Pis that are supported on the camshaft 34 and can be lifted by the cams Ni. Here, the support surfaces Pis are formed as bearings, such as roller bearings or plain bearings. In this example, the first pawl Pl of the first clutch mechanism Cl comprises two support surfaces, here two roller bearings, Pls. The support surfaces Pls are supported on the camshaft 34 and lifted by the cams N 1 and N2. A circumferential groove is here provided in the camshaft 34 between the cams N 1 and N2 as clearance for the first pawl Pl. In this example, the first and second pawls P2A, P2B of the second clutch mechanism C2 each comprise two support surfaces, here two roller bearings, P2As, P2Bs. The support surfaces P2As, P2Bs are supported on the camshaft 34 and lifted by the cams N2 and N3. A circumferential groove is here provided in the camshaft 34 between the cams N2 and N3 as clearance for the first and second pawls P2A, P2B. In this example, the first and second pawls P3A, P3B of the third clutch mechanism C3 each comprise two support surfaces, here two roller bearings, P3As, P3Bs. The support surfaces P3As, P3Bs are supported on the camshaft 34 and lifted by the cams N3 and N4. A circumferential groove is here provided in the camshaft 34 between the cams N3 and N4 as clearance for the first and second pawls P3A, P3B. In this example, the first and second pawls P4A, P4B of the fourth clutch mechanism C4 each comprise two support surfaces, here two roller bearings, P4As, P4Bs. The support surfaces P4As, P4Bs are supported on the camshaft 34 and lifted by the cams N5 and N6. A circumferential groove is here provided in the camshaft 34 between the cams N5 and N6 as clearance for the first and second pawls P4A, P4B.

[0071] It will be appreciated that it is also possible that the cams of the camshaft 34 are provided with bearings, such as roller bearings or plain bearings for contacting the pawls. In an example, the actuator comprises a rotation sensor and / or a position sensor. Thus, a gear in which the actuator is positioned can be monitored. It is for instance possible to monitor a rotational position of the electromechanical actuator 32 and / or the camshaft 34.

[0072] Figure 6B show an example in which two sun gears 129a, 129b are shown mounted on the axle 30 over the respective pawls Pl, P2A, P2B. For clarity, the sun gears 129c, 129d are not shown in figure 6B.

[0073] As can be seen in more detail in figures 3A-3I, the pawls associated with larger sun gears in this example also have larger roller bearings for support surfaces, than pawls associated with smaller sun gears.

[0074] In this example, in each clutch mechanism Cl, C2, C3, C4, the first Pl, P2A, P3A, P4A and second P2B, P3B, P4B pawls are configured for each pivoting about a respective pivot axis. In this example, each pawl comprises two protrusions Pip forming end of a pivot axle P of the respective pawl. The protrusions P2Bp of the second pawl P2B of the second clutch mechanism C2 are indicated in figure 2B. It will be appreciated that the other pawls have similar protrusions in this example.

[0075] As can be seen in figure 2B, the pawls of the clutch mechanisms Cl, C2, C3, C4 are positioned rotated about the central axis A. That is, the pawl Pl of the first clutch mechanism Cl is positioned rotated about the central axis A relative to the pawls of the second, third and fourth clutch mechanisms C2, C3, C4. The first and second pawls P2A, P2B of the second clutch mechanism C2 are positioned rotated about the central axis A relative to the pawls of the first, third and fourth clutch mechanisms Cl, C3, C4. The first and second pawls P3A, P3B of the third clutch mechanism C3 are positioned rotated about the central axis A relative to the pawls of the first, second and fourth clutch mechanisms Cl, C2, C4. The first and second pawls P4A, P4B of the fourth clutch mechanism C4 are positioned rotated about the central axis A relative to the pawls of the first, second and third clutch mechanisms Cl, C2, C3. Thus, a first position of at least one pawl of at least one of the clutch mechanisms is rotated about the central axis relative to a second position of at least one pawl of at least another one of the clutch mechanisms. Here, a first position of the first and second pawls of at least one of the clutch mechanisms is rotated about the central axis relative to a second position of the first and second pawls of at least another one of the clutch mechanisms. As will be discussed in view of figures 3A-3I, in an example the pawls are positioned such that a rotation of the cam shaft in a single direction successively actuates the respective pawls such that the transmission ratios of the transmission are sequentially selected in a ascending or descending order. In this example, the positions of the pawls are spaced 40 degrees apart. Hence, the camshaft can be rotated over eight times 40 degrees to access nine different transmission ratios.

[0076] Figure 2B further shows two bearings 36, here roller bearings (but plains bearings are also possible) around the camshaft 34, for supporting the camshaft 34 inside the axle 30.

[0077] Figure 2C shows the actuator of figures 2A and 2B inside the axle 30. As shown in figure 2C, in this example the axle 30 has a plurality of axle sections of different outer diameter. In this example a first axle section 30A has a first outer diameter. The first 129a and second 129b sun gears can be mounted on the first axle section 30A in this example. A second axle section 30B has a smaller outer diameter than the first axle section 30A. The third sun gear 129c can be mounted on the second axle section 30B in this example. A third axle section 30C has a smaller outer diameter than the second axle section 30B. The fourth sun gear 129d can be mounted on the third axle section 30C in this example. Thus, the axle 30 has a different outer radius at positions of different sun gears 129i of the plurality of sun gears. The different outer diameters of the axle sections 30A, 30B, 30C can provide ease of assembly of the clutch mechanisms Cl, C2, C3, C4. The different outer diameters of the axle sections 30A, 30B, 30C can provide that a larger diameter axle section is provided supporting sun gears that transfer higher torque to the axle 30. Preferable, torque is supported from the axle 30 onto the frame of the vehicle, e.g. onto the housing, on the side of the axle 30 having the larges axle section diameter.

[0078] It can also be seen in figure 2C that a radial distance between a pivot axis p of the pawls and the central axis A of the axle 30 is different for different clutch mechanisms Cl, C2, C3, C4 of the plurality of clutch mechanisms. For all the pawls Pi, the pivot axis p of the respective pawls Pi is positioned such that the pivot axle P is positioned just below the surface of the respective axle section. In this example, a first radial distance between the pivot axis p of the first pawl Pl of the first clutch mechanism C 1 and the central axis A of the axle 30 is equal to a second radial distance between the pivot axis p of the first and second pawls P2A, P2B of the second clutch mechanism C2 and the central axis A of the axle 30. In this example, the first radial distance between the pivot axis p of the first and second pawls P2A, P2B of the second clutch mechanism C2 and the central axis A of the axle 30 is larger than a third radial distance between the pivot axis p of the first and second pawls P3A, P3B of the third clutch mechanism C3 and the central axis A of the axle 30. In this example, the third radial distance between the pivot axis p of the first and second pawls P3A, P3B of the third clutch mechanism C3 and the central axis A of the axle 30 is larger than a fourth radial distance between the pivot axis p of the first and second pawls P4A, P4B of the fourth clutch mechanism C4 and the central axis A of the axle 30. It will be appreciated that in this example, a radial distance between the tops of the cams N5, N6 of the fourth clutch mechanism C4 and the central axis A is also smaller than a radial distance between the tops of the cams N 1, N2, N3, N4 of the first, second, and third clutch mechanism Cl, C2, C3 and the central axis. The pivot axis p of the pawls is maintained at the radial distance from the central axis A in a pocket fashioned in the axle 30. In particular, the protrusions Pip forming ends of the pivot axle P of the respective pawl are nested in pockets fashioned in the axle 30.

[0079] Figures 3A-3I show a sequence of gear shifting using the transmission of figures 1-3C. In this example, When the transmission input I is driven in the first rotational direction R1 about the stationary axle 30, while the switching mechanism is in the first state, the ring gear 128 is also driven in the first rotational direction, and via the stepped planet gear 127, a rotational force is induced on the sun gears 129i in the second, reverse, rotational direction. By braking a selective one of the sun gears 129i in the second rotational direction with a corresponding one of the clutch mechanisms Ci, torque can be transmitted from the ring gear 128 to the planet carrier 126, according to an underdrive transmission ratio.

[0080] Figure 3A shows a situation with the transmission input I driven in the first rotational direction R1 about the stationary axle 30, while the switching mechanism is in the first state. The first actuatable bidirectional clutch mechanism Cl is shown in the second disposition in figure 3A. The first actuatable bidirectional clutch mechanism Cl, in this example, is a biased actuatable bidirectional clutch mechanism having only a single pawl Pl. The pawl Pl is not actuated by the cam N 1, N2 in the first position. The biased actuatable bidirectional clutch mechanism C 1 includes a freewheel clutch 15 allowing rotation in the first rotational direction Rl, and blocking rotation in the second rotational direction R2. Figure 4A shows an example of the freewheel clutch 15 of the biased actuatable bidirectional clutch mechanism Cl. Here, the freewheel clutch 15 comprises a plurality of rollers 15r, such as balls or cylinders, between an inner race 15i and an outer race 15o. In this example, the outer race 15o is provided with a sawtooth profile. Hence, the largest sun gear 129a is braked, and torque is transmitted from the input I via the ring gear 128 to the planet gear 127 to the output O via the planet carrier 126. The transmission ratio is determined by the first sun gear 129a and the first planet gear part 127a, and constitutes that smallest transmission ratio (first gear, underdrive).

[0081] Figure 3B shows a situation with the transmission input I driven in the first rotational direction R1 about the stationary axle 30, while the switching mechanism is in the first state. The second actuatable bidirectional clutch mechanism C2 is shown in the second disposition in figure 3B. The camshaft has been rotated to a second position. The second pawl P2B is actuated by the cam N2, N3 in the second position. An engagement surface of the second pawl P2B engages a corresponding engagement surface associated with the second sun gear 129b, and blocks rotation in the second rotational direction R2. Hence, the second sun gear 129b is braked, and torque is transmitted from the input I via the ring gear 128 to the planet gear 127 to the output O via the planet carrier 126. The transmission ratio is determined by the second sun gear 129b and the second planet gear part 127b, and constitutes a next higher transmission ratio (second gear, underdrive).

[0082] Figure 3C shows a situation with the transmission input I driven in the first rotational direction R1 about the stationary axle 30, while the switching mechanism is in the first state. The third actuatable bidirectional clutch mechanism C3 is shown in the second disposition in figure 3C. The camshaft has been rotated to a third position. The second pawl P3B is actuated by the cam N3, N4 in the third position. An engagement surface of the second pawl P2B engages a corresponding engagement surface associated with the third sun gear 129c, and blocks rotation in the second rotational direction R2. Hence, the third sun gear 129c is braked, and torque is transmitted from the input I via the ring gear 128 to the planet gear 127 to the output O via the planet carrier 126. The transmission ratio is determined by the third sun gear 129c and the third planet gear part 127c, and constitutes a next higher transmission ratio (third gear, underdrive).

[0083] Figure 3D shows a situation with the transmission input I driven in the first rotational direction R1 about the stationary axle 30, while the switching mechanism is in the first state. The fourth actuatable bidirectional clutch mechanism C4 is shown in the second disposition in figure 3D. The camshaft has been rotated to a fourth position. The second pawl P4B is actuated by the cam N5, N6 in the fourth position. An engagement surface of the second pawl P4B engages a corresponding engagement surface associated with the fourth sun gear 129d, and blocks rotation in the second rotational direction R2. Hence, the fourth sun gear 129d is braked, and torque is transmitted from the input I via the ring gear 128 to the planet gear 127 to the output O via the planet carrier 126. The transmission ratio is determined by the fourth sun gear 129d and the fourth planet gear part 127d, and constitutes a next higher transmission ratio (fourth gear, under drive).

[0084] Figure 3E shows a situation with the camshaft 34 rotated to a fifth position. In this fifth position, the fourth actuatable bidirectional clutch mechanism C4 is in the third disposition. Thus, neither the first pawl P4A nor the second pawl P4B is lifted by the cams N5, N6. In this situation, the switching mechanism is switched to the third state. Thus, the ring gear 128 and the planet carrier 126 are coupled to corotate. Torque is transmitted from the input I to the output O via the ring gear and / or planet carrier 126. It will be appreciated that in this example the cams N5, N6 of the fourth clutch mechanism C4 are wider than the cams N1-N4 of the other clutch mechanisms Cl, C2, C3. Hence, a smooth handover from the fourth to the fifth gear (and from the fifth to the sixth gear) can be obtained. This situation constitutes a next higher transmission ratio, which corresponds to a unity transmission ratio (fifth gear, unity transmission ratio).

[0085] Next, the switching mechanism is switched to the second state. When the transmission input I is driven in the first rotational direction about the stationary axle 30, while the switching mechanism is in the second state, the planet carrier 126 is also driven in the first rotational direction, and via the stepped planet gear 127, a rotational force is induced on the sun gears 129i in the first rotational direction. By braking a selective one of the sun gears 129i in the first rotational direction with a corresponding one of the clutch mechanisms Ci, torque can be transmitted from the planet carrier 126 to the ring gear 128 according to an overdrive transmission ratio.

[0086] Figure 3F shows a situation with the transmission input I driven in the first rotational direction R1 about the stationary axle 30, while the switching mechanism is in the second state. The fourth actuatable bidirectional clutch mechanism C4 is shown in the first disposition in figure 3F. The camshaft has been rotated to a sixth position. The first pawl P4A is actuated by the cam N5, N6 in the sixth position. An engagement surface of the first pawl P4A engages a corresponding engagement surface associated with the fourth sun gear 129d, and blocks rotation in the first rotational direction Rl. Hence, the fourth sun gear 129d is braked, and torque is transmitted from the input I via the planet carrier 126 to the planet gear 127 and to the output O via the ring gear 128. The transmission ratio is determined by the fourth sun gear 129d and the fourth planet gear part 127d, and constitutes a next higher transmission ratio (sixth gear, overdrive).

[0087] Figure 3G shows a situation with the transmission input I driven in the first rotational direction Rl about the stationary axle 30, while the switching mechanism is in the second state. The third actuatable bidirectional clutch mechanism C3 is shown in the first disposition in figure 3G. The camshaft has been rotated to a seventh position. The first pawl P3A is actuated by the cam N3, N4 in the seventh position. An engagement surface of the first pawl P3A engages a corresponding engagement surface associated with the third sun gear 129c, and blocks rotation in the first rotational direction Rl. Hence, the third sun gear 129c is braked, and torque is transmitted from the input I via the planet carrier 126 to the planet gear 127 and to the output O via the ring gear 128. The transmission ratio is determined by the third sun gear 129c and the third planet gear part 127c, and constitutes a next higher transmission ratio (seventh gear, overdrive). Figure 3H shows a situation with the transmission input I driven in the first rotational direction R1 about the stationary axle 30, while the switching mechanism is in the second state. The second actuatable bidirectional clutch mechanism C2 is shown in the first disposition in figure 3H. The camshaft has been rotated to an eighth position. The first pawl P2A is actuated by the cam N2, N3 in the eighth position. An engagement surface of the first pawl P2A engages a corresponding engagement surface associated with the second sun gear 129b, and blocks rotation in the first rotational direction Rl. Hence, the second sun gear 129b is braked, and torque is transmitted from the input I via the planet carrier 126 to the planet gear 127 and to the output O via the ring gear 128. The transmission ratio is determined by the second sun gear 129b and the second planet gear part 127b, and constitutes a next higher transmission ratio (eighth gear, overdrive).

[0088] Figure 31 shows a situation with the transmission input I driven in the first rotational direction Rl about the stationary axle 30, while the switching mechanism is in the second state. The first actuatable bidirectional clutch mechanism C 1 is shown in the first disposition in figure 31. The camshaft has been rotated to a ninth position. The pawl Pl is actuated by the cam Nl, N2 in the ninth position. An engagement surface 38 of the pawl Pl engages a corresponding engagement surface 40 associated with the first sun gear 129a, and blocks rotation in the first rotational direction Rl. Hence, the first sun gear 129a is braked, and torque is transmitted from the input I via the planet carrier 126 to the planet gear 127 and to the output O via the ring gear 128. The transmission ratio is determined by the first sun gear 129a and the first planet gear part 127a, and constitutes a next higher transmission ratio (ninth gear, overdrive).

[0089] It will be appreciated that while switching through the consecutive gears from the lowest (here first) gear to the highest (here ninth) gear, the sun gears 129i are first used in a sequence from the largest to the smallest sun gear, and subsequently in a sequence from the smallest to the largest sun gear.

[0090] Figure 4B shows an example of a sun gear 129i with an actuatable bidirectional clutch mechanism Ci. The pawls PiA, PiB are in this example generally L-shaped. The pawls PiA, PiB have a first body portion 44 extending from the pivot axle P to the engagement surface 38. The first body portion extends substantially tangentially to the outer surface of the axle 30. The pivot axle P is hingedly supported in a pocket 48 of the axle 30. The pawls PiA, PiB have a second body portion 46 extending substantially radially inwards. The second body portion 46 carries the support surfaces Pis. Here, the second body portion has two axially oriented bosses onto which roller bearings forming the support surfaces Pis are mounted. In this example, the engagement surface 38 of the pawls Pi and the corresponding engagement surface 40 of the sun gear 129i are angled relative to the radial direction. The angle is chosen such that moving the engagement surfaces 38, 40 against and towards each other tends to move the pawl Pi radially inwards. Hence, the pawls Pi are biased to disengage. A spring may be added for spring biased disengagement of the pawls Pi. Figure 6A shows an example of the pawls Pi biased by a spring 121. Hence, the actuatable bidirectional clutch mechanism Ci is biased to disengage. In the first and second disposition, the presence of the cam Ni underneath the support surfaces Pis prevents the engagement surfaces 38, 40 from disengaging when pressed against each other. In figure 4B, the camshaft 34 is positioned such that the clutch mechanism Ci is in the first disposition. In this first disposition, rotating the sun gear 129i in the first rotational direction R1 will force the engagement surfaces against each other, the first pawl PiA is pushed in the pocket 48 against a radial end wall 49 of the pocket 48, and rotation of the sun gear 129i in the first rotational direction is prevented (see corresponding figure 3G). Figure 4B shows the particular situation in which the clutch mechanism Ci is in the first disposition and the sun gear 129i is driven in the second rotational direction R2. The actuatable bidirectional clutch mechanism Ci is configured such that, in the first disposition, the sun gear 129i is prevented from rotating in the first rotational direction Rl, but enabled to rotate (freewheel) in the second rotational direction R2. In that case, the protrusions 50 on the inner perimeter of the sun gear 129i will push the first pawl PiA in the first rotational direction, tangentially moving the pawl PiA inside the pocket 48, away from the radial end wall 49 of the pocket, such that the support surfaces Pis drop off the cam Ni. This causes the first pawl PiA to pivot radially inward, such that the engagement surface 38 of the pawl PiA is at a radius that is smaller than the engagement surface 40 of the sun gear 129i. As a result, the sun gear 129i can freewheel in the first rotational direction Rl while the clutch mechanism Ci is in the first disposition. In this example, the first pawl PiA has a protrusion 52, such as a ridge, on a radially outward surface of the pawl PiA. The protrusion 52 can be caught by the protrusion 50 of the sun gear 129i to promote moving the pawl PiA tangentially so as to drop off the cam Ni. In this example, a spring or other resilient element is provided to bias the pawl PiA back into the pocket 48. The spring or other resilient element can pull the pawl, such that the pivot axle P tangentially abuts against the radial end wall of the pocket 48. It will be appreciated that similarly, the actuatable bidirectional clutch mechanism Ci is configured such that, in the second disposition, the sun gear 129i is prevented from rotating in the second rotational direction R2, but enabled to rotate (freewheel) in the first rotational direction Rl.

[0091] Figure 7A shows an example in which the spring 121 has the combined function of biasing the pawls PiA, PiB into the pocket 48, and for biasing the pawls PiA, PiB radially inward for biasing disengagement of the engagement surfaces 38, 40. In this example, the spring 121 comprises a helically wound section 121a. Two arms 121b, 121c extend from the ends of the helically wound section. The distal ends of the arms 121b, 121c overlap in this example. Thereby, the spring 121 wraps around the axle 30 over more than 360 degrees. The distal ends of the arms 121b, 121c are each provided with a hook 12 Id, 12 le. In this example, the spring comprises a single helically wound section 121a. It will be appreciated that the spring may also comprise more than one, e.g. two, helically wound sections. As shown in figure 8B, the hooks 12 Id, 12 le engage the respective pawls PiA, PiB. Thus, pulling force of the spring 121 biases the pawls PiA, PiB such that the pivot axle P tangentially abuts against a radial end wall of the pocket 48. Also, the arms 121b, 121c of the spring are positioned in circumferential grooves Pig of the pawls PiA, PiB (see e.g. grooves Pig, P2g, P3g, P4g in figures 6A and 6B), such that pulling force of the spring 121 biases the pawls PiA, PiB radially inward. Here, the arms wrap around the pawls PiA, PiB. In this example, the first arm 121b pushes the second pawl PiB radially inwards, and the second arm 121c pushes the first pawl PiA radially inwards. Here, the arms are also positioned in a circumferential groove 30g in the outer surface of the axle 30. In this example, the spring 121 extends between the pawls PiA, PiB, i.e. a first end 12 Id of the spring is attached to a first pawl PiA, and a second end 12 le of the spring is attached to a second pawl PiB. Hence, here the spring 121 pulls the pawls PiA, PiB towards each other. It will be appreciated that it is also possible that each pawl has one or more individual springs associated therewith.

[0092] Returning to Figures 1 and 2A, the camshaft 34 is in this example further configured for actuating the switching mechanism. In this example, the camshaft comprises one or more grooves 54, here two grooves, for actuating the switching mechanism. The camshaft 34 is configured for axially moving a selector 56 from a first position to a second position or from the second position to the first position. Here, the selector 56 comprises a pen 58 that extends into the groove 54. It will be appreciated that the groove 54 is shaped such that rotation of the camshaft 34 will axially move the pen 58, and thereby the selector 56. The first actuatable clutch Si and / or the second actuatable clutch S2 is configured to switch from a coupled state to a decoupled state or from a decoupled state to a coupled state upon axial movement of the selector 56. In this example, the groves 54 are shaped such that the first actuatable clutch S 1 and the second actuatable clutch S2 from the coupled state to the decoupled state or from the decoupled state to the coupled state substantially simultaneously.

[0093] The actuatable clutches Si, S2 of the shifting mechanism can be similar or identical to a clutch as described in WO2018 / 199757A2, W02020 / 085911A2, WO2021 / 080431A1 or WO2021 / 249945A1, incorporated herein by reference in their entirety. Referring to figures 5A and 5B, the actuatable clutches Si, S2 can have a first rotatable unit 80 including at least one first abutment surface 82 and a second rotatable unit 84 including at least one second abutment surface 86 arranged for selectively engaging the first abutment surface. The first and second abutment surfaces 82, 86 are adapted to each other so as to allow disengaging under load, preferably in two directions. The actuatable clutches Si, S2 can have a third rotatable unit 88 including at least one retaining member 90. The third rotatable unit 88 is arranged for selectively being in a first mode (figure 5A) or a second mode (figure 5B) relative to the second rotatable unit 84. In the first mode, the at least one retaining member 90 locks the at least one second abutment surface 86 for rotationally coupling the second rotatable unit 84 to the first rotatable unit 80, e.g. in two rotational directions. In the second mode, the at least one retaining member 90 releases the at least one second abutment surface 86 for decoupling the second rotatable unit 84 from the first rotatable unit 80. The actuatable clutches can include an actuator for moving the third rotatable unit from a first position (figure 5A) to a second position (figure 5B) or from a second position to a first position relative to the second rotatable unit. Here, the second rotatable unit 84 carries gripping members 92. The gripping members have the second abutment surface 86. The gripping members 92 are pivotally connected to the second rotatable unit 84. In the first position, here, the retaining member 90 is positioned such as to push the second abutment surfaces 86 of the gripping members 92 radially outwards into engagement with the first engagement surfaces 82. In this example, the second engagement surface 86 and the corresponding first engagement surface 82 are angled relative to the radial direction. The angle is chosen such that moving the engagement surfaces 82, 86 against and towards each other tends to move the gripping member 92 radially inwards. Hence, the gripping members 92 are biased to disengage. A spring may be added for spring biased disengagement of the gripping member 92. Hence, the actuatable clutches Si, S2 are biased to disengage. In the first position, the presence of the retaining member underneath the gripping member 92 prevents the engagement surfaces 82, 86 from disengaging when pressed against each other. In the second position, the retaining member 90 is positioned such as to allow the gripping member 92 to pivot radially inwards, to allow disengagement of the second abutment surface 86 from the first engagement surface 82.

[0094] The third rotatable unit 88 includes at least one actuation member 94 arranged for moving the third rotatable unit 88 from a first position to a second position or from a second position to a first position relative to the second rotatable unit 84. In this example, the actuatable clutches Si, S2 further includes a fourth unit 96 including a selector 98. The fourth unit 96 can be non-rotatable, e.g. relative to the axle 30. The selector being arranged for selectively being in a gripping or non-gripping mode. The selector 98 in the gripping mode is arranged for gripping the at least one actuation member 94 for rotating the third rotatable unit 88 from the first position to the second position or from the second position to the first position relative to the second rotatable unit 84. The selector 98 in the nongripping mode is arranged for not engaging the at least one actuation member 94.

[0095] Figures 8A and 8B show an example of the selector 98. In this example, the selector includes one or more grooves 120 immobile relative to the axle 30. The selector further includes a selection bush 122 that is axially movable relative to the axle 30. The bush 122 comprises a first section 122A of a first outer diameter, and a second section 122B having a second outer diameter that is smaller than the first outer diameter. In this example, the bush 122 can be axially moved by a pin 124 riding in the groove 54 of the camshaft 34. The bush 122 can be moved into a first position (figure 9A) and a second position (figure 8B). As can be seen in figures 8A and 8B, in this example the two actuation members 94A and 94B are slightly different. In particular, a cutout 136A, 136B of the respective actuation members 94A, 94B is positioned differently.

[0096] With the bush in the first position, as shown in figure 8A, the first actuation member 94A rides with its radially inward end on the larger outer diameter first section 122A of the bush. Hence, the first actuation member 94A is prevented from entering the groove 120. With the bush in the first position, as shown in figure 8A, the second actuation member 94B has its cutout 136B aligned with the larger outer diameter first section 122A of the bush. Hence, the second actuation member 94A is enabled to enter the groove 120. With the bush in the second position, as shown in figure 9B, the second actuation member 94B rides with its radially inward end on the larger outer diameter first section 122A of the bush. Hence, the second actuation member 94B is prevented from entering the groove 120. With the bush in the second position, as shown in figure 8B, the first actuation member 94A has its cutout 136A aligned with the larger outer diameter first section 122A of the bush. Hence, the first actuation member 94Ais enabled to enter the groove 120. Once the first or second actuation member 94A, 94B enters the groove 120, the third rotatable unit 88 is temporarily halted, causing the third rotatable unit to rotate relative to the second rotatable unit 84. The third rotatable unit 88 will rotate relative to the second rotatable unit 84 from a first position (figure 5A) to a second position (figure 5B) or from a second position to a first position. Hence, the actuatable clutch Si, S2 will engage or disengage. After the third rotatable unit 88 moving from a first position to a second position or from a second position to a first position, the respective actuation member 94A, 94B is knocked out of the respective groove 120 by a resetting member 138 e.g. corotating with the second rotatable unit 84. Optionally, a resilient member is placed in the connection between the camshaft 34 and the selection bush 122. The resilient member allows the camshaft 34 to already perform the motion for axially moving the bush 122, while the bush 122 is (temporarily) prevented from actually performing the axial movement, e.g. due to being blocked from performing the axial movement by one or more of the actuation members 94A, 94B. For example, when the first actuation member 94A is in the groove 120, the bush 122 may be prevented from moving from the first position to the second position. If, in this situation, the camshaft is rotated for axially moving the bush 122 from the first position to the second position the resilient member may be deformed. Once the first actuation member 94A is lifted out of the groove, the bush 122 may perform (or finish) the axial movement already imposed by the camshaft 34. For example, when the second actuation member 94B is in the groove 120, the bush 122 may be prevented from moving from the second position to the first position. If, in this situation, the camshaft is rotated for axially moving the bush 122 from the second position to the first position the resilient member may be deformed. Once the second actuation member 94B is lifted out of the groove, the bush 122 may perform (or finish) the axial movement already imposed by the camshaft 34.

[0097] The resilient member can be a compliant mechanism. The resilient member can be pre-tensioned, e.g. in two directions, such as two axial directions. The resilient member can e.g. be placed in the bush 122, between the bush 122 and the pin(s) 124, between the pins(s) 124 and the groove 54, and / or between the groove 54 and the camshaft 34.

[0098] Figures 9A-9C show an example of the selector 98. In this example, the selector includes one or more grooves 120 immobile relative to the axle 30. In this example, the selection bush 122 comprises a first section 122A of a first outer diameter. The second section 122B having a second outer diameter that is smaller than the first outer diameter is omitted in this example. Also in this example, the bush 122 can be axially moved by the pin 124 riding in the groove 54 of the camshaft 34. The bush 122 can be moved into a first position (figure 9A) and a second position (figure 9B). With the bush 122 in the first position, as shown in figure 10A, the first actuation member 94A rides with its radially inward end on the outer diameter first section 122A of the bush. Hence, the first actuation member 94Ais prevented from entering the groove 120. With the bush in the first position, as shown in figure 9A, the second actuation member 94B has its cutout 136B aligned with the outer diameter first section 122A of the bush. Hence, the second actuation member 94Ais enabled to enter the groove 120. With the bush in the second position, as shown in figure 9B, the second actuation member 94B rides with its radially inward end on the outer diameter first section 122 A of the bush. Hence, the second actuation member 94B is prevented from entering the groove 120. With the bush in the second position, as shown in figure 9B, the first actuation member 94A is enabled to enter the groove 120. In this example, the first actuation member 94A does not have a cutout 136 A. Instead, a width of the first actuation member 94A is chosen such that with the bush in the second position the first actuation member 94A is enabled to enter the groove 120. Once the first or second actuation member 94A, 94B enters the groove 120, the third rotatable unit 88 is temporarily halted, causing the third rotatable unit to rotate relative to the second rotatable unit 84. The third rotatable unit 88 will rotate relative to the second rotatable unit 84 from a first position (figure 5A) to a second position (figure 5B) or from a second position to a first position. Hence, the actuatable clutch Si, S2 will engage or disengage. After the third rotatable unit 88 moving from a first position to a second position or from a second position to a first position, the respective actuation member 94A, 94B is knocked out of the respective groove 120 by a resetting member 138 e.g. corotating with the second rotatable unit 84.

[0099] Figure 9C shows a side view of an example of the bush 122. In this example, the pin 124 is connected to the bush 122 via a tangential arm 124A. A proximal end of the arm 124A connects to the bush 122, while a distal end of the arm 124A connects to the pin 124. The arm is in this example made of a resilient material, such as a plastics material. The arm 124A can form the resihent member referred to above. The arm allows for the pin already moving in an axial direction of the axle 30, while the bush 122 is still prevented from axially moving by means of the first or second actuation member being positioned in a groove 120.

[0100] Figures 10A-10C show an example of the selector 98. In this example, the selector includes one or more grooves 120 immobile relative to the axle 30. In this example, the selection bush 122 comprises a first section 122A of a first outer diameter. The second section 122B having a second outer diameter that is smaller than the first outer diameter is omitted in this example. Also in this example, the bush 122 can be axially moved by the pin 124 riding in the groove 54 of the camshaft 34. The pin can e.g. be connected to the bush 122 via an arm 124A as shown in figure 9C. The pin extends through a cutout 123 in the axle 30. In an example, the bush 122 has a plurality of pins 124 connected thereto, such as 2 or 3 pins, e.g. evenly distributed about the circumference of the bush 122. The bush 122 can be moved into a first position (figure 10A) and a second position (figure 10C). As can be seen in figures 10A-10C, the groove 54 has two legs that extend transverse to the longitudinal axis of the camshaft 34. When the pin 124 is in one of the two legs, the bush is in a stable situation in the first or second position, respectively. The arm 124A can be tensioned in the first and / or second position, such that the bush 122 is pressed against an axial face 30A, 30B. Hence, a stable positioning of the bush 122 can be obtained. Figure 10B shows an intermediate position in which the camshaft 34 is rotated such that the pin 124 is in a slanted portion of the groove 54 that connects the two legs. The two actuation members 94A and 94B can be similar as shown in figures 8 A and 8B or 9 A and 9B.

[0101] The first and second actuation members 94A, 94B, can e.g. be as shown in figures 8A, 8B, 9A or 9B. With the bush 122 in the first position, as shown in figure 10A, the first actuation member 94A can ride with its radially inward end on the outer diameter first section 122A of the bush. Hence, the first actuation member 94A is prevented from entering the groove 120. With the bush in the first position, as shown in figure 10A, the second actuation member 94B can have its cutout 136B aligned with the larger outer diameter first section 122A of the bush. Hence, the second actuation member 94A is enabled to enter the groove 120. With the bush in the second position, as shown in figure 10C, the second actuation member 94B can ride with its radially inward end on the outer diameter first section 122A of the bush. Hence, the second actuation member 94B is prevented from entering the groove 120. With the bush in the second position, as shown in figure 8C, the first actuation member 94A can have its cutout 136A aligned with the outer diameter first section 122A of the bush. Alternatively, the first actuation member can have no cutout as described with respect to figures 9 A, 9B. Hence, the first actuation member 94A is enabled to enter the groove 120. Once the first or second actuation member 94A, 94B enters the groove 120, the third rotatable unit 88 is temporarily halted, causing the third rotatable unit to rotate relative to the second rotatable unit 84. The third rotatable unit 88 will rotate relative to the second rotatable unit 84 from a first position (figure 5A) to a second position (figure 5B) or from a second position to a first position. Hence, the actuatable clutch Si, S2 will engage or disengage. After the third rotatable unit 88 moving from a first position to a second position or from a second position to a first position, the respective actuation member 94A, 94B is knocked out of the respective groove 120 by a resetting member 128 e.g. corotating with the second rotatable unit 84.

[0102] In an example, the transmission system 1000 comprises an electric drive for propelling, or assisting in propelling, the bicycle. The electric drive can be mounted concentrically around the axle 30. Alternatively, the electric drive can be mounted at least partially inside the axle 30. The electric drive can comprise an electric motor. The electric motor can comprise a stator and a rotor. The electric drive can comprise a planetary gear set. The electric drive can comprise a rotation sensor and / or a position sensor. Figure 11 shows an example of a transmission system 1000 for a human powered vehicle or hght electric vehicle, such as a bicycle. Figures 12A and 12B show alternative views of the transmission of figure 11. The transmission system comprises a housing 308. The transmission system 1000 comprises a crank axle 1004. The transmission system 1000 comprises a front sprocket 1009. In this example, the transmission system 1000 comprises a transmission 100 as described herein above. The axle 30 is offset and parallel to a crank axle 1004. In this example, the crank axle 1004 comprises a first pully 302 and a second pully 304 is mounted to the input I of the transmission for driving the input I. Here, the input is driven via a belt 306. Thus, the transmission system 1000 is in this example configured such that the crank axle 1004 is connected to the input I of the transmission 100 via a first endless drive member 306, for transferring torque from the crank axle 1004 to the input I of the transmission 100. It will be appreciated that it is also possible to drive the transmission input I via a chain, cardan, offset gears, or the like. The transmission output O is connected to the front sprocket 1009, for engaging a chain or belt of a chain or belt drive 300 for driving a, e.g. rear, wheel of the vehicle. Here, the front sprocket 1009 is offset relative to the crank axle 1004. It will be clear that it is also possible that the front sprocket 1009 is coaxial with the crank axle 1004. In this example, an electric motor 310 is provided in the housing 308. Here the electric motor 310 drives the transmission input I, in particular via the belt 306. The motor 310 can drive the crank axle 1004 or the first pully 302, e.g. via a freewheel. A transmission ratio from the crank axle 1004 to the transmission input I is chosen to be a speed-increasing transmission ration in order to reduce torque on the transmission 100. The speed increasing transmission ratio from the crank axle to the transmission input can e.g. be about 2.5 or less.

[0103] Figures 13A and 13B show an example of a transmission system 1000 for a human powered vehicle or light electric vehicle, such as a bicycle, similar to the example of figures 11, 12A and 12B. In the example of figures 13A and 13B, the electric motor 310 is offset and parallel to the crank axle 1004. Here, the motor 310 drives the transmission input I, in particular via the belt 306. The motor 310 can drive the crank axle 1004 or the first pully 302, e.g. via a freewheel. Here, the motor 310 drives the first pully via a speed reduction 311, e.g. comprising an intervening gear 312.

[0104] Figures 14A and 14B show an example of a transmission system 1000 for a human powered vehicle or light electric vehicle, such as a bicycle, similar to the example of figures 13A and 13B. In this example, the crank axle 1004 drives the input I of the transmission 100 via a first gear 302’ meshing with a second gear 304’. However, it will be appreciated that it is also possible to use the pullies 302, 304 and belt 306 as in figures 13A, 13B, or a chain. In the example of figures 14A and 14B, the front sprocket 1009 is concentric with the crank axle 1004. Hence, the front sprocket 1009 is offset relative to the axle 30 of the transmission 100. The output O of the transmission 100 here drives the front sprocket via a second geared connection. In this example, the transmission output O comprises a third gear 314’ meshing with a fourth gear 316’ mounted to front sprocket 1009. Thus, in this example, the transmission system 1000 is configured such that the output O of the transmission 100 is connected to the front sprocket 1009 via a geared connection, for transferring torque from the output O of the transmission 100 to the front sprocket 1009. It will be appreciated that it is also possible to drive the front sprocket 1009 via a belt, chain, cardan, or the like.

[0105] Figures 15A and 15B show an example of a transmission system 1000 for a human powered vehicle or light electric vehicle, such as a bicycle, similar to the example of figures 11, 12A and 12B. In the example of figures 15A and 15B, the front sprocket 1009 is concentric with the crank axle 1004. Hence, the front sprocket 1009 is offset relative to the axle 30 of the transmission 100. The output O of the transmission 100 here drives the front sprocket 1009 via a second endless drive member. In this example, the transmission output O comprises a third pully 314 driving a fourth pully 316v mounted to front sprocket 1009, via a second belt 320. Thus, in this example, the transmission system 1000 is configured such that the output O of the transmission 100 is connected to the front sprocket 1009 via a endless drive member, for transferring torque from the output O of the transmission 100 to the front sprocket 1009. It will be appreciated that it is also possible to drive the front sprocket 1009 via a geared connection, chain, cardan, or the like.

[0106] Figure 16 shows an examples of a transmission system 1000 similar to the system of figures 11, 12A and 12B. Here, the transmission system 1000 is embodied as a crank transmission comprising a further transmission 200 in addition to the first transmission 100. The transmissions 100 and 200 are in this example both accommodated in the crank housing 308. The transmission system is here an offset crank transmission having an input axis Al and an output axis A2 that are parallel and spaced apart from each other. Here, the crank axle 1004 drives the second pully 304 via the first pully 302 and the belt or chain 306. Here, the transmission 100 is a nine-speed transmission as shown in figure 1. Here, the further transmission 200 is a two-speed transmission, selectively providing one of two transmission ratios. Preferably a transmission ratio step of the further transmission 200 is chosen to be smaller than a transmission ratio step of the transmission 100. In this example, the transmission ratio step of the further transmission 200 is chosen to be about half of the transmission ratio step of the transmission 100. Hence, the further transmission 100 can provide intermediate transmission ratios between the transmission ratios of the transmission 100. This may allow for smaller transmission ratio steps.

[0107] In the example of figure 16, the further transmission 200 is associated with the output axis A2. Here the second transmission 200 includes a planetary gear set. In this example, the chain or belt 306 drives the second pully 306. However, a geared driving using gears 302’, 304’ as shown in figures 14A, 14B is also possible. The pully 304 is connected to a planet carrier 200C of the planetary gear set. The planet carrier 200C carries one or more stepped planet gears 200P. The smaller portion of the stepped planet gear 200P meshes with a ring gear 200R. The ring gear 200R drives the input I of the transmission 100. The larger portion of the stepped planet gear 200P meshes with a sun gear 200S. The sun gear 200S can be braked in at least one rotational direction, so as to prevent rotation of the sun gear 200S with respect to the axle 30 in that rotational direction. The braking can e.g. be performed with a clutch, for instance similar to the clutches Ci as describe hereinabove. The clutch can e.g. be controlled by the or a cam shaft. The braking can e.g. be performed with a brake pawl. There can be a bearing, such as a rolling bearing between the cam shaft and the pawl. The planet carrier 200C or pully 304 is further connected to the ring gear 200R or the input I of the transmission 100 via a freewheel 200F.

[0108] In a first mode, the sun gear 200S is not braked, and thus free to rotate. In that case, the pully 200G will drive the input of the first transmission 100 via the freewheel 200F. Hence, a 1:1 transmission is obtained from the pully 304 to the input I of the transmission 100. In a second mode, the sun gear 200S is braked. In that case, the pully 304 will drive the ring gear 200R (via the planet carrier 200C and planet gears 200P) according to a speed increasing transmission ratio. Hence, the freewheel 200F will be overrun. Thus, in a very simple manner, the further transmission 200 can provide the two different transmission ratios.

[0109] It will be appreciated that the further transmission 200 can also be applied in the examples of figures 13A, 13B, 14A, IB, 15A, andl5B.

[0110] In the example of figure 16, the transmission 100 and further transmission 200 are both housed in a crank unit. It will be appreciated that the transmission 100 and further transmission 200 as described in view of figure 16 can also both be housed in a wheel hub. In that case, the pully 304 can e.g. be driven in rotation by a chain or belt by a front sprocket.

[0111] The bicycle transmission 1000 further comprises control electronics 150 for controlling the actuator, e.g. the electromechanical actuator 32. The control electronics can comprise at least one of a controller, generator, battery, PCB, wireless receiver / transmitter, antenna, LED, charge plug, connector, or micro-chip. In an example, the control electronics are mounted in the housing 308.

[0112] A receiver of the control electronics 150 can be configured for receiving a shift control signal, such as from a shifter 1024. The shift control signal can be representative of a desired transmission gear (e.g. first gear, second gear, third gear, etc.). The shift control signal can be representative of upshift or downshift. The controller can be configured for, on the basis of the shift control signal controlling the actuator, such as the electromechanical actuator. Alternatively, or additionally, the controller can be configured for autonomously changing a transmission gear, e,g. on the basis of a current transmission gear, a wheel speed, a cadence, a torque, and / or a heart rate. Particularly when the transmission system comprises the generator and is configured for autonomously changing the transmission ratio, a self-contained autonomous transmission can be provided. Optionally, characteristics of the transmission system, such as parameters on when to shift gears can be adjusted by a user, e.g. using an interface, such as on a mobile communications device, such as a smartphone, in (wireless) communication with the control electronics.

[0113] Figure 17 shows an example of a bicycle 1. The bicycle includes a frame 1002 and a front fork 1005. The bicycle includes a handlebar 1003. A front wheel 1011 is mounted to the front form 1005. The frame 1002 includes a rear fork 1007 having a rear wheel 1013 mounted thereto. A crank axle 1004 is mounted to the frame 1002. The crank axle 1004 can be connected to the housing 308, the housing 308 being connected to the frame. Pedals 1017 are connected to the crank axle 1004. A front sprocket 1009 is also connected to the crank axle 1004. The rear wheel is provided with a hub 1022. A rear sprocket 1021 is connected to the hub. In this example, the rear sprocket 1021 is connected to the hub 1022. The crank axle 1004 is connected to the front sprocket 1009 via a transmission system 100, e.g. as described above. The front sprocket 1009 drives the rear sprocket 1021 via an endless member, such as a chain or belt. The bicycle 1 in this example includes a shifter 1024 configured for transmitting a shift control signal to a receiver of the control electronics 150 of the transmission system 100.

[0114] Herein, the invention is described with reference to specific examples of embodiments of the invention. It will, however, be evident that various modifications and changes may be made therein, without departing from the essence of the invention. For the purpose of clarity and a concise description features are described herein as part of the same or separate embodiments, however, alternative embodiments having combinations of all or some of the features described in these separate embodiments are also envisaged.

[0115] In the examples, an eight-speed or nine-speed transmission system is provided using four different sun gears. It will be appreciated that it is also possible to provide the transmission system with fewer, or more different transmission ratios, such as two or three (e.g. one sun gear) four or five (e.g. two sun gears), six or seven (e.g. three sun gears), ten or eleven (e.g. five sun gears), twelve or thirteen (e.g. six sun gears), fourteen or fifteen (e.g. seven sun gears), sixteen or seventeen (e.g. eight sun gears), eighteen or nineteen (e.g. nine sun gears), or twenty or twenty-one (e.g. ten sun gears) different transmission ratios. The number of planet ger parts of different radii of the stepped planet gears can correspond to the number of different sun gears.

[0116] In the example, each sun gear is associated with an actuatable bidirectional clutch mechanism configured for in a first mode selectively preventing rotation of the at least one sun gear in a first rotational direction about the axle (and optionally allowing rotation of the at least one sun gear in an opposite second rotational direction about the axle), and in a second mode selectively preventing rotation of the at least one sun gear in the opposite second rotational direction about the axle (and optionally allowing rotation of the at least one sun gear in the first rotational direction about the axle), for providing two different transmission ratios with one sun gear. It will be appreciated that it is possible that the transmission system further includes one or more sun gears having an associated unidirectional clutch mechanism configured for in a first mode selectively preventing rotation of the at least one sun gear in a first rotational direction about the axle (and optionally allowing rotation of the at least one sun gear in the opposite second rotational direction about the axle), and in a second mode allowing rotation of the at least one sun gear in the first rotational direction (and optionally allowing rotation of the at least one sun gear in the opposite second rotational direction about the axle).

[0117] However, other modifications, variations, and alternatives are also possible. The specifications, drawings and examples are, accordingly, to be regarded in an illustrative sense rather than in a restrictive sense.

[0118] In the claims, any reference signs placed between parentheses shall not be construed as limiting the claim. The word ‘comprising’ does not exclude the presence of other features or steps than those listed in a claim. Furthermore, the words ‘a’ and ‘an’ shall not be construed as limited to ‘only one’, but instead are used to mean ‘at least one’, and do not exclude a plurality. The mere fact that certain measures are recited in mutually different claims does not indicate that a combination of these measures cannot be used to an advantage.

Claims

Claims1. A transmission system (1000) for a human powered vehicle, or light electric vehicle, such as a bicycle, comprising: a crank housing (308); a crank axle (1004); a front sprocket (1009); and a transmission (100) having an input (I) connected to the crank axle (1004) and an output (O) connected to the front sprocket (1009), the transmission (100) comprising: an axle (30), offset and parallel to the crank axle (1004), configured to be non-rotatably fixed or fixable to the crank housing (308); at least one sun gear (129i) rotatably mounted around the axle; and at least one clutch mechanism (Ci) configured for in a first mode selectively preventing rotation of the at least one sun gear (129i) in a first rotational direction about the axle (30), and in a second mode selectively preventing rotation of the at least one sun gear (129i) in an opposite second rotational direction about the axle (30).

2. The transmission system (1000) of claim 1, wherein the crank axle drives the input (I) of the transmission via a geared connection (302’, 304’) or via an endless drive member (306), such as a belt or chain.

3. The transmission system (1000) of claim 1 or 2, wherein the crank axle drives the input of the transmission via a speed increasing transmission.

4. The transmission system (1000) of claim 3, wherein the speed increase has a ratio of between 1:1 or 2:1.

5. The transmission system (1000) of any of claims 1-4, wherein the front sprocket (1009) is rotatable coaxially with the axle (30) or coaxially with the crank axle (1004).

6. The transmission system (1000) of claim 5, wherein the output (O) of the transmission drives the front sprocket (1009) via a geared connection (316’, 318’) or via an endless drive member (320), such as a belt or chain.

7. The transmission system (1000) of any of claims 1-6, wherein the transmission (100) is configured for providing a speed reduction and / or speed increase between the input (I) and the output (O) of the transmission.

8. The transmission system (1000) of any of claims 1-7, comprising an electric propulsion motor (310).

9. The transmission system (1000) of claim 8, wherein the electric motor is concentric with the crank axle.

10. The transmission system (1000) of claim 8, wherein the electric motor is offset and parallel to the crank axle.

11. The transmission (1000) system of any of claims 8-10, wherein the electric motor drives the input of the transmission.

12. The transmission system (1000) of any of claim 8-11, wherein the electric motor drives the crank axle (1004) or a gear or pully mounted on the crank axle.

13. The transmission system (1000) of any of claims 1-12, wherein the at least one clutch mechanism (Ci) is configured to be actively electronically actuated to select the respective mode of the clutch mechanism.

14. The transmission system (1000) of any of claims 1-13, wherein the at least one sun gear (129i) comprises at least two or at least three sun gears (129a, 129b, 129c, 129d) rotatably mounted around the axle (30), and the at least one clutch mechanism (Ci) comprises a respective clutch mechanism (Cl, C2, C3, C4) associated with each of the sun gears for selecting at least the first and second modes.

15. The transmission system (1000) of claim 14, wherein the at least two or at least three sun gears have different diameters and are connected by at last one stepped planet gear (127a, 127b, 127c, 127d) rotatably mounted inside a carrier (126).

16. The transmission system (1000) of claim 15, comprising a ring gear (128) meshing with one of the planets of the stepped planet gear(s).

17. The transmission system (1000) of any of claims 1-16, wherein the transmission is configured to selectively transfer torque from the input (I) of the transmission to the ring gear (128) or to the carrier (126) of the planetary gear set.

18. The transmission system (1000) of claim 17, wherein the input (I) of the transmission is connected to the ring gear (128) via a one-way clutch or one-way bearing (12).

19. The transmission system (1000) of claim 17 or 18, wherein the input of the transmission is connected to the carrier via a first actuatable clutch mechanism (Si).

20. The transmission system (1000) of any of claims 1-19, wherein the transmission is configured to selectively transfer torque from the ring gear (128) or the carrier (126) of the planetary gear set to the output of the transmission (O).

21. The transmission system (1000) of claim 20, wherein the carrier is connected to the output of the transmission via a one-way clutch or one-way bearing.

22. The transmission system (1000) of claim 20 or 21, wherein the ring gear is connected to the output of the transmission via a second actuatable clutch mechanism (S2).

23. The transmission system (1000) of any of claims 1-22, wherein the at least one clutch mechanism (Ci) is configured for in a third mode allowing the sun gear to rotate freely around the axle in at least one or both rotational directions.

24. The transmission system (1000) of any of claims 1-23, wherein the or each clutch mechanism (Ci) comprises a first pawl (PiA) and a second pawl (PiB) configured to be actuated by a camshaft (34), such that the first pawl is selectively in engagement with the respective sun gear (129i) in the first mode, and the second pawl is selectively in engagement with the respective sun gear (129i) in the second mode.

25. The transmission system (1000) of any of claims 1-24, wherein at least one of the clutch mechanisms (Ci) comprises a passive one-way clutch or one-way bearing to create a first or second mode.

26. The transmission system (1000) of claim 24, or 25 as far as dependent from claim 24, wherein the camshaft (34) is mounted inside the axle (30) for actuating the at least one clutch mechanism (Ci).

27. The transmission system (1000) of claim 26 as far as dependent form claim 14, wherein the camshaft (34) mounted inside the axle is configured for actuating the respective clutch mechanisms (Ci) of the at least one clutch mechanism.

28. The transmission system (1000) of claim 27 as far as dependent from claims 19 and 22, wherein the camshaft (34) mounted inside the axle is configured for actuating the first and second actuatable clutch mechanisms (SI, S2).

29. The transmission system (1000) of any of claims 1-28, wherein the at least one clutch mechanism is designed such that it can disengage from a torque loaded sun gear, in at least one direction.

30. The transmission system (1000) of claim 29 as far as dependent from claim 24, wherein the pawls (PiA, PiB) are designed such that they disengage under torque load on the sun gear, and that the camshaft is configured to allow to prevent disengagement.

31. The transmission system (1000) of any of claims 1-30, wherein between the camshaft (34) and the pawls (PiA, PiB) there is a roller bearing.

32. The transmission system of any of claims 1-31, wherein between the camshaft and axle there is at least one roller bearing (Pis).

33. The transmission system (1000) of any of claims 1-32, further comprising a further transmission (200) in the housing and in series with the transmission.

34. The transmission system (1000) of claim 33, wherein the further transmission (200) is placed in series between the crank axle (1004) and the transmission (100).

35. The transmission system (1000) of claim 33 or 34, wherein a transmission ratio step size between successive transmission ratios of the further transmission (200) is smaller than a transmission ratio step size between successive transmission ratios of the transmission (100).

36. The transmission system (1000) of claim 33, 34 or 35, wherein the further transmission (200) comprises: a pully (304) driven by the crank axle; a planet carrier (200C) connected to the pully; one or more stepped planet gears (200P); a sun gear (200S) meshing with a larger portion of the stepped planet gears; a ring gear (200R) meshing with a smaller portion of the stepped planet gears; a freewheel (200F) between the pully or planet carrier and the input of the transmission; and a clutch mechanism configured for selectively preventing rotation of the sun gear of the further transmission in at least one rotational direction.

37. A transmission system (1000) for a human powered vehicle, or light electric vehicle, such as a bicycle, comprising: a crank housing (308); a crank axle (1004);a front sprocket (1009); and a transmission (100) having an input (I) connected to the crank axle and an output (O) connected to the front sprocket, the transmission comprising: an axle (30), offset and parallel to the crank axle, configured to be non-rotatably fixed or fixable to the crank housing; at least one sun gear (129i) rotatably mounted around the axle; and at least one clutch mechanism (Ci) configured for in a first mode selectively preventing rotation of the at least one sun gear in a first rotational direction about the axle, and in a second mode decoupling the sun gear.

38. The transmission system (1000) of claim 37, comprising any of the features and options as recited in any of claims 2-36.

39. A human powered vehicle (1) or light electric vehicle, such as a bicycle, comprising the transmission system (1000) of any of claims 1-38.

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