Gearbox

Abstract

A modern bicycle drivetrain includes a chain and a plurality of sprockets, where the chain is moved between the respective sprockets by derailleur. Although these systems are readily accessible by a user for maintenance, they are also readily malfunctioning, such as chain disengagement or derailleur mechanical malfunction. A gearbox (2) for a bicycle is proposed that solves at least this problem, the gearbox (2) comprising: an input gear (8) configured to receive a drive input and to rotate in a first plane about a first axis of rotation; an output gear (4) configured to rotate about a second axis of rotation in a second plane different from the first plane; a plurality of drive transmitting devices intermediate the input gear (8) and the output gear (4), each drive transmitting device (26) comprising a first gear (44) engaged with the input gear (8), a second gear (46) engaged with the output gear (4), and a shaft (58) therebetween, each drive transmitting device (26) being configurable between a locked configuration in which the first gear (44) engages with the input gear (8), and an unlocked configuration in which the second gear (46) engages with the output gear (4), rotation of one of the first gear (44) and the second gear (46) causes rotation of the other of the first gear (44) and the second gear (46) such that drive between the input gear (8) and the output gear (4) is enabled, and an unlocked configuration in which the first gear (44) and the second gear (46) rotate independently of each other thereby disabling drive from the input gear (8) to the output gear (4); and selection means (71) for selecting one of the plurality of drive transmission means (26) and reconfiguring the selected drive transmission means (26) between an unlocked configuration and a locked configuration.

Description

[0001] The present invention relates to a gearbox suitable for a bicycle or a pedelec (such as a bicycle assisted by an electric motor) powered entirely by the cyclist.

[0002] Modern bicycle drivetrains include a chain and a plurality of sprockets, wherein the chain is moved between the respective sprockets by a derailleur. While these systems are easily accessible to the user for maintenance, they are also prone to failure, such as chain derailment or derailleur mechanical failure.

[0003] One way to overcome these drawbacks is to use a gearbox drive. Conventional gearbox arrangements utilize a number of gears axially arranged along a plurality of shafts. These gears are axially selectively meshed with each other on these shafts to achieve different gear ratios. The combined effect of the plurality of gears on a single or multiple shafts results in a long drive chain, thereby resulting in a bulky and heavy drivetrain. Another embodiment of a gear drive is a planetary gearbox, which can produce a more compact drive, but is still heavy and may have a long drivetrain when multiple gear ratios are required.

[0004] It is desirable for a bicycle to be lightweight, thereby reducing the gravitational burden when traveling uphill and any frictional losses associated with the increased weight. This makes the use of conventional gear drives challenging as they add significant weight. Additionally, due to their large size, they cannot be comfortably fitted within a conventional bicycle frame, which means that such frames generally cannot accommodate a more affordable derailleur drive as an alternative drivetrain option.

[0005] Aspects of the present invention seek to address the above deficiencies or at least provide useful alternatives.

[0006] According to the present invention, there is provided a gearbox for a bicycle, comprising:

[0007] - an input gear configured to receive a drive input and rotate about a first axis of rotation in a first plane;

[0008] - an output gear configured to rotate about a second axis of rotation in a second plane different from the first plane;

[0009] - a plurality of drive transmission means located intermediate the input gear and the output gear, each drive transmission means including a first gear engaged with the input gear, a second gear engaged with the output gear, and a shaft therebetween, each drive transmission means being configurable between a locked configuration in which rotation of one of the first gear and the second gear causes rotation of the other of the first gear and the second gear such that drive between the input gear and the output gear is enabled, and an unlocked configuration in which the first gear and the second gear rotate independently of each other, thereby disabling drive from the input gear to the output gear;

[0010] - A selection device for selecting one of a plurality of drive transmission devices and reconfiguring the selected drive transmission device between an unlocked configuration and a locked configuration.

[0011] The selection device advantageously switches between the respective drive transmission devices, which means selecting a drive transmission device suitable for the movement of a vehicle incorporating a gearbox. It should be understood that when the drive transmission device is in the locked configuration such that the first gear and the second gear rotate simultaneously, the drive between the drive input gear and the drive output gear is enabled.

[0012] The interpretation of the term "drive" when referring to enabling between the input gear and the output gear means that torque is transmitted from the input gear to the output gear through the drive transmission device in the locked configuration.

[0013] The first gear of each drive transmission device is advantageously located in a first plane, and the second gear of each drive transmission device is advantageously located in a second plane.

[0014] The gear ratio of at least one drive transmission device between the first gear and the second gear is not 1:1. Each of the first gear and the second gear on at least one (preferably each) drive transmission device has a plurality of teeth for engaging with the respective input gear and output gear, wherein the number of teeth on the first gear is different from the number of teeth on the second gear.

[0015] The gear ratio between the first gear and the second gear of the first drive transmission device is different from the gear ratio between the first gear and the second gear of the second drive transmission device. This enables the user to achieve different gear selections.

[0016] The gear ratio of the input gear to the first gear is advantageously less than 1:1. It is advantageously significantly less than 1:1.

[0017] This can be adjusted according to torque and speed requirements. For the first gear to the last gear, illustrative suitable gear ratio ranges are respectively 6:1 to 10:1, even more preferably 5:1 to 9:1, and even more preferably 4:1 to 8:1. By way of illustration, the input gear can have approximately 80 teeth. This means that the first gear of the drive transmission device has a higher angular velocity than the input gear. This means that the torque on the input transmission device is smaller, which means that for a given input torque capacity, the drive transmission device can be smaller and lighter.

[0018] The first gear of each drive transmission device is advantageously in constant mesh with the input gear. The second gear of each drive transmission device is advantageously in constant mesh with the output gear.

[0019] The second rotational axis is preferably different from the first rotational axis. The first axis and the second axis are advantageously parallel to each other. The first and second gears of each drive transmission device advantageously rotate about a common axis. In other words, the first and second gears of one drive transmission device rotate about a common axis that is different from the common rotational axis of the first and second gears of any other drive transmission device.

[0020] The selection device preferably includes an actuator device for reconfiguring a selected drive transmission device from an unlocked configuration to a locked configuration. The selection device also preferably includes a controller for controlling the actuator device. The controller may include a shifter for receiving a user input for transmitting a signal to the actuator device to effect movement of the actuator device. Such movement results in reconfiguration between the unlocked and locked configurations. The signal may be mechanical or electrical.

[0021] The selection device is preferably constructed such that only one drive transmission device having a particular gear ratio is in the locked configuration at any given time. It should be understood that multiple drive transmission devices having the same gear ratio may be in the locked configuration at any given time.

[0022] Each drive transmission device may include a separate actuator device. In such an embodiment, each actuator device is preferably controlled by an electrical signal from the controller. Each actuator device may include a solenoid.

[0023] The actuator device may include a structure rotatably mounted relative to the plurality of drive transmission devices and arranged to selectively reconfigure the selected drive transmission device between the locked and unlocked configurations. The structure may be coaxial with the first rotational axis. The structure may include a plate.

[0024] The drive transmission device is preferably arranged such that one of the first or second gears is fixed relative to the shaft such that rotation of the corresponding first or second gear causes rotation of the shaft, and the other of the first or second gears is rotatably mounted relative to the shaft. The drive transmission device further includes locking means arranged to releasably engage and disengage the first or second gear rotatably mounted to the shaft from the shaft such that relative rotation is enabled when disengaged and disabled when engaged. In such an enabled configuration, there is no drive from the input gear to the output gear.

[0025] The locking device may include: one or more locking elements for interlocking the shaft and the first or second gear in a locked configuration; and a pin movable between a first position and a second position, in which the locking element is biased to engage the first or second gear, and in which the locking element is released from engagement with the first or second gear. The pin is preferably longitudinally movable in a rotational axis that is the same as the rotational axes of the first and second gears. The locking element may be a pawl.

[0026] Each locking device may include a pin for moving the locking element(s), and wherein the actuator device includes a structure rotatably mounted relative to a plurality of drive transmission devices, the structure including a plurality of recesses or abutments, wherein each recess or abutment is paired with a corresponding pin such that in discrete rotational positions of the structure, when the pin engages the corresponding paired recess or abutment, the paired pin is axially displaced. In such positions, no other pin is received in or on their corresponding paired recesses or abutments.

[0027] Alternatively, at least one of the first and second gears may be axially movable between a locked configuration and an unlocked configuration. A locking device in the form of a claw clutch may be provided to effect locking between the first and second gears. The first and second gears may be axially positioned between a structure and a spring. The spring is for returning the first and second gears from the locked configuration to the unlocked configuration. There may be a first structure and a second structure axially arranged on either side of the drive transmission device and movable to selectively actuate one of the drive transmission devices between a locked configuration and an unlocked configuration. The first and second structures preferably include corresponding protrusions and / or recesses. It should be understood that one drive transmission device means one or more drive transmission devices having the same gear ratio.

[0028] Under certain conditions and for certain applications, a gearbox may require the ability to shift gears under high torque conditions. This can occur when the user is climbing a steep hill and wants to quickly change gears without minimizing their torque input. Thus, in such a case, the actuator device may not be able to rotate to effect the changeover of the selected drive transmission means from the locked configuration to the unlocked configuration. Accordingly, the actuator device may be configured to deflect axially into a deflected configuration (under higher torque conditions), and also provides an abutment that can move with the input gear or the output gear, wherein the abutment and the actuator device are configured to abut in the deflected configuration and force the selected drive transmission means into the unlocked configuration. It should be understood that when the abutment and the actuator device abut, the force may be mainly axial (due to the geometry of the abutment, i.e., the ramp), and thus forces the actuator device to reverse the deflected part, thereby forcing the transmission means that resists axial movement to return. This effectively forces a gear shift. The actuator device may plastically deform into the deflected configuration or may be axially displaced as a whole away from the drive transmission means. The abutment is preferably a shoulder projecting from the input gear or the output gear adjacent to the actuator device.

[0029] The input gear preferably includes an input gear ring, and the output gear preferably includes an output gear ring. Each of the input gear and the output gear preferably includes a plurality of engaging teeth. The teeth of the input gear and the output gear may project radially inwards or outwards. Depending on the relative positioning of the input gear and the output gear, the gearbox may be a hub gearbox or a direct crank drive gearbox.

[0030] The output gear is preferably fixedly connected to a plurality of teeth that extend outwards. These outwards-extending teeth transmit the drive from the gearbox outwards to an external element. Preferably, they are used to transmit the drive from the gearbox to the rear wheel of a bicycle via a chain. The fixed connection means that rotation of the output gear causes the associated rotation of the plurality of teeth. Further, the fixed connection means that the output gear is coaxial with the plurality of outwards-extending teeth.

[0031] The input gear preferably includes coupling means for coupling one or more shafts to the input gear to transmit the drive input to the input gear. The (one or more) shafts may be driven by a crank arm and / or a motor. Optionally, the input drive from the motor may be transmitted to a first gear of the drive transmission means in the unlocked configuration, and then the drive is transmitted to the input gear. The input gear then transmits the drive to a different drive transmission means in the locked configuration, and then to the output gear. This can reduce the number of reduction stages required to transmit the rotation from the electric motor to the gearbox.

[0032] The gearbox preferably further includes a motor coupled to the coupling means for providing an auxiliary drive to the input gear. The motor and the gearbox are advantageously provided in a single housing.

[0033] According to the present invention, there is also provided a gear motor for an electric bicycle, comprising:

[0034] - a gearbox as described above;

[0035] - a motor for providing drive to the input gear.

[0036] According to the present invention, there is also provided a power system for an electric bicycle, comprising:

[0037] - a gear motor as described above;

[0038] - a sprocket for mounting on a wheel of the bicycle;

[0039] - a chain or a drive belt coupled to the output gear and the sprocket for transmitting the drive from the output gear to the sprocket.

[0040] The motor can provide drive to the input gear by means of a reduction gear stage, or alternatively, the motor can indirectly drive the input gear by providing direct drive to a first gear of a drive transmission means or indirect drive via a shorter reduction gear stage. Thus, the gearbox can be arranged such that the motor provides direct drive to the first gear or the second gear.

[0041] Aspects of the present invention will now be described only by way of illustration with reference to the accompanying drawings, in which:

[0042] Figure 1 is a schematic view of a gearbox according to an illustrative embodiment of the present invention.

[0043] Figure 2 Figs. 3 to 5 are exploded schematic views of a gearbox according to an illustrative embodiment of the present invention.

[0044] Figures 6a to 6d is a schematic view of a perspective view, an exploded view and a cross-sectional view of a drive transmission means present in an illustrative embodiment of the present invention, Figures 6e to 6f is an alternative drive transmission means.

[0045] Figure 7 is a schematic view of an actuator means present in an illustrative embodiment of the present invention.

[0046] Figure 8a and Figure 8b are respectively a schematic perspective view and an exploded view of a motor and a gearbox assembly according to an illustrative embodiment of the present invention.

[0047] Figure 9a and Figure 9b are schematic perspective views of an illustrative embodiment of the present invention.

[0048] Figure 10 is a schematic perspective view of a hub gearbox according to an illustrative embodiment of the present invention.

[0049] Figure 11 is a schematic exploded view of a hub gearbox according to an illustrative embodiment of the present invention.

[0050] Figure 12 is a schematic view of a part of an illustrative embodiment of the present invention.

[0051] Figure 13a and Figure 13b is a schematic view of a part of an illustrative embodiment of the present invention.

[0052] Figure 14 is a schematic view of a part of an illustrative embodiment of the present invention.

[0053] Figure 15a and Figure 15b is a schematic view of a part of an illustrative embodiment of the present invention.

[0054] Figure 16 is a schematic view of a part of an illustrative embodiment of the present invention.

[0055] Figures 17a to 17c is a schematic view of an illustrative embodiment of the present invention.

[0056] Figure 18 is a schematic view of an illustrative embodiment of the present invention.

[0057] Reference Figure 1 , shows a gearbox 2 according to an illustrative embodiment of the present invention. Figure 1 Shows the external components of the gearbox, in the form of an output gear structure 4 which internally carries the output gear and which additionally includes a plurality of outward-facing teeth 6. Also provided is an input gear structure 8 which carries the input gear and a housing 10 which houses the components of the actuator device - the actuator device enabling the selection of which "gear" is to be used by the operator - and a carrier which carries a series of drive transmission means. The gearbox 2 is connected to the pedal crank arm 12 via fixing bolts 14. It should be understood that the axial thickness of the gearbox is relatively small and can be mounted in place of the conventional crank arm and chainring on a conventional bicycle frame without the need to modify the frame or design a custom frame construction. Thus, the gearbox 2 can be mounted to an existing bicycle frame, thereby eliminating the need for a conventional derailleur.

[0058] Reference Figure 2, shows an exploded view of a gearbox 2 according to an illustrative embodiment of the present invention. In this figure, for clarity, the crank arm 12 is removed together with the housing 10. The input gear structure 8 carries an input gear having a plurality of inwardly facing gear teeth 18. The input gear structure 8 further includes a coupling structure 20, such as a plurality of spline teeth, which is designed to be coupled to a pedal crankshaft and / or a motor, and the pedal crankshaft and / or the motor provides drive to the input gear structure 8. The input gear structure 8 is driven about a rotation axis through the center of the ring.

[0059] Adjacent to the input gear structure 8 is a selector plate 22, which forms part of an actuator device that will be described in more detail later. Axially adjacent to the selector plate 22 is a carrier 24, which is arranged to carry a plurality of drive transmission devices 26. In the presented embodiment, there are eight drive transmission devices 26, which means that the gearbox provides eight individual gear ratios for the user. It should be understood that the number of drive transmission devices 26 can be modified according to the number of required individual gear ratios. A bearing 31 is provided for receiving an input shaft 30, wherein the input shaft 30 receives input from the crank arm 12 and / or a motor (if present). The input shaft 30 extends through the bearing 31 and is supported by it to be coupled to the motor. Optionally, additionally or alternatively, the input shaft 30 can be coupled to the coupling structure 20 of the input gear structure 8.

[0060] The output gear structure 4 is axially outside the carrier 24 and includes a plurality of outwardly facing teeth 34, which are engaged via a chain or a belt to engage a sprocket that forms part of a bicycle rear wheel. Thus, the output gear provides a linkage for driving the rear wheel. The output gear structure 4 further includes an output gear having a plurality of radially inwardly facing teeth 36, which are more clearly shown in Figure 3 such that the inner surface of the output gear structure 4 is visible.

[0061] When assembled, it should be understood that the teeth 18 of the input gear are constantly engaged with the drive transmission devices 26, and the inner teeth 36 of the output gear are also constantly engaged with the drive transmission devices 26. Thus, each drive transmission device provides an alternative path for the drive from the input gear to the output gear. How the drive passes through a single drive transmission device 26 to provide different gears to the user will be described in more detail later. It should also be understood that the selector plate 22 enables the selection of one drive transmission device 26 to be actuated, which means that the drive passes through this drive transmission device 26. It should be understood that the drive will pass through a different drive transmission device 26 at a time, and the selector plate 22 makes this happen. The selector plate 22 can be operated by means of a servo motor 38, which realizes the actuation of the selector plate 22. The servo motor 38, the selector plate 22 and a controller in the form of a shifter (not shown) together partially include a selection device.

[0062] Now referring to Figure 3 , an alternative exploded view of the gearbox is presented, wherein the gear teeth 36 of the output gear are also presented as extending radially inwards in the output gear structure 4, and wherein the teeth 34 are also shown for transmitting drive to the rear wheels. The output gear structure 4 also includes a flange 39 integral with the output gear structure 4, wherein the flange is configured to be inserted into the Figure 2 bearing 28 best shown in, and the output gear structure 4 rotates about this bearing. The bearing 28 is held in the carrier 24. Figure 2 The input shaft 30 presented in Figure 3 is not shown in, however, it extends through the flange 39, through the bearing 28, and is then supported by a bearing 31 axially parallel to but offset from the bearing 28. The input shaft is then coupled to an electric motor. A selector plate 22 in the form of a disc and coaxial with the input shaft (and the first axis of rotation) has a plurality of recesses 40, as Figure 2 shown, and the servo motor 38, also clearly visible, is included. As will be described in more detail, the servo motor 38 enables the selector plate 22 to rotate, which means that different drive transmission means 26 can be selected and locked, such that drive is transmitted through the selected drive transmission means.

[0063] Figure 4 The assembly of the gearbox in the assembled configuration is also schematically presented. For clarity, only the output gear of the output gear structure 4 and its plurality of teeth 36, and the input gear of the input gear structure 8 and its plurality of teeth 18 are shown. The carrier 24 is clearly visible, showing the plurality of drive transmission means 26. Each drive transmission means includes a first gear 44 and a second gear 46 that engage respectively with the input gear teeth 18 and the output gear teeth 36. In order to achieve different gear ratios, each of the first gear 44 and the second gear 46 is different in each drive transmission means. In the locked configuration where rotation of the input gear structure 8 causes the associated rotation of the first gear 44, the second gear 46 will also rotate, causing the associated rotation of the output gear structure 4. In the unlocked configuration, the first gear 44 and the second gear 46 rotate independently of each other, which means that there is no drive from the first gear 44 to the second gear 46 and thus no drive from the input gear structure 8 to the output gear structure 4. Each of the first gear and the second gear is in constant mesh with the input gear and its plurality of teeth 18 and the output gear and its plurality of teeth 36, which means that it does not matter which drive transmission means 26 is in the locked configuration, and there is a permanent rotation of each of the first gear 44 and the second gear 46.

[0064] Figure 4The arrangement of the arm 47 of the carrier 24 is shown more clearly therein. The arm 47 can be used to rotate about a fixed first axis and then fix the entire carrier relative to the bicycle frame. Since the output gear structure 4 is mounted eccentrically relative to the input shaft, the position of the output gear structure 4 relative to the frame on which the gearbox is mounted can be adjusted. This means that the chain or belt can be tensioned without other tensioning devices or a specific frame design.

[0065] Further reference Figure 4 , it is clear that the input gear and its plurality of teeth 18 and the output gear and its plurality of teeth 36 are respectively in the first and second planes, wherein these planes are different from each other. They are effectively in a side-by-side configuration with the carrier 24 located therebetween. Thus, the thickness or width of the gearbox is very narrow, which means that the gearbox can be first integrated into an existing standard bicycle without modifying the frame. Secondly, this means that such a gearbox can be positioned relative to the motor in a side-by-side configuration, which means that the width of the entire motor / gearbox assembly is minimized.

[0066] Figure 5a is another figure from which the additional components have been removed. This is presented as simply showing the input gear and its plurality of teeth 18, the output gear and its plurality of teeth 36, and showing seven drive transmission devices 26 in the illustrative embodiment. For clarity, other components such as the carrier and the actuator device have been removed. FIG. 5 clearly illustrates the low axial width of the gearbox and shows the drive transmission device 26 in more detail. The drive transmission device and the first gear 44 and the second gear 46 respectively have different numbers of teeth to provide different gears to the user. For example, it should be understood that by providing a first gear having many teeth relative to a second gear having fewer teeth, a low gear is provided, wherein the input speed of the input gear structure 8 is high relative to the low output speed of the output gear structure 4. For the other drive transmission devices 26, the situation is reversed.

[0067] Reference Figure 5b , a device is presented in which one of the first gear 44 or the second gear 46 is driven by an electric motor 47. In this case, the motor benefits from the naturally occurring reduction stage. Also shown in this figure are the same first and second drive transmission devices 26 provided for increasing the peak torque capacity. This is beneficial in some applications.

[0068] Figure 5c is a diagram of a device in which the drive transmission device is arranged outside the input gear structure 8 and the output gear structure 4.

[0069] Now refer Figures 6a to 6d , the illustrative drive transmission device 26 is presented. The drive transmission device 26 includes a first gear 44 and a second gear 46, each having a plurality of teeth.Figure 6a The bearing 50 about which the shaft 58 rotates is shown. Now refer to Figure 6b , the shaft rotates within the bearing, and one of the gears 44, 46 is fixedly connected to the shaft, which can be, for example, via a plurality of splines 52. This means that one of the first gear 44 or the second gear 46 is fixed relative to the shaft and thus must rotate with the shaft 58. In the illustrated embodiment, the fixed gear will be referred to as the first gear 44. The second gear 46 is also mounted to the shaft 58 via a bearing 54, which allows the second gear 46 to rotate relative to the shaft 58 in the unlocked configuration. A locking device is provided, which may include a pawl 60 held within the body of the shaft 58. Other components present are a spring 62 and a transfer pin 64, where the transfer pin 64 includes a first region having a first radius 66 and a second region having a second radius 68. The second radius 68 is greater than the first radius 66.

[0070] Now in connection with Figure 6b refer to Figure 6c , the drive transmission 26 is in the locked configuration, where the spring 62 applies a force to the rear of the transfer pin 64 such that it protrudes outward from the front surface of the second gear 46. This protrusion 66a causes the second region 68 of the transfer pin 64 to contact the rear of the pawl 60, forcing them radially outward from the shaft 58. Thus, in this configuration, the pawl 60 engages into a corresponding orifice 68 in the inner surface of the second gear 46, which means that the second gear 46 cannot rotate relative to the shaft 58 about the bearing. Thus, in this configuration, the drive is transmitted from the first gear 44 to the second gear 46.

[0071] Now refer to Figure 6d , the drive transmission 26 is in the unlocked configuration, where the protrusion 66a no longer extends significantly from the front surface of the second gear 46, which means that the transfer pin 64 has been pushed inward against the force of the spring 62. This means that, since the first region having the first radius is now in communication with the pawl 60, the pawl disengages from the recess 68 and now allows rotation of the second gear 46, which means that the drive transmission 26 is now in the unlocked state. The drive transmission is biased towards the locked state, however, at any given moment, only one drive transmission can be in the locked state. The remaining drive transmissions are in the unlocked state, and in the presented embodiment, the transfer pin 66 must thus be deflected into the compressed configuration as shown in Figure 6d . This means that once the transfer pin 64 can be released into the Figure 6c configuration, the engagement of the drive transmission 26 and the drive through it will be achieved.

[0072] Refer to Figure 6e, an alternative drive transmission is presented, in which one of the first gear 44 or the second gear 46 axially moves between a locked configuration and an unlocked configuration relative to the other of the first gear or the second gear. The type of drive transmission presented is called a dog clutch. The gear pair 44, 46 disengages when moving axially apart and engages when moving axially together. In this case, the gear pair 44, 46 remains in constant mesh with the main input gear and the output gears 4, 8 by only partially deviating from the main input and / or output gears. When using softer materials (such as polymers) in a gearbox construction, the dog clutch provides a significantly increased amount of material and increased load transfer. In the presented embodiment, the first gear 44 is rotatably mounted to the first shaft portion 101 at a fixed axial position (but this configuration can be reversed), and the second gear is rotatably mounted to the second shaft portion 103 at a fixed axial position, wherein the first and second shaft portions 101, 103 can move axially relative to each other. In the unlocked configuration where the gears are axially separated, they can rotate independently of each other, while in the locked configuration where the gears are engaged with each other, drive is transmitted between the first gear and the second gear. In this embodiment, the locking means includes corresponding protrusions 105 and recesses 107 arranged to engage with each other, and the engagement can be maintained by angled or hooked elements belonging to the thrust surfaces in the protrusions 105, which generate an axial coupling force between the gears 44 and 46, and this axial coupling force can counteract any unwanted axial force that could cause an undesired disengagement of the clutch. To achieve a similar effect, the gear profiles can be helical and oriented to generate an axial force in a direction that promotes clutch engagement. Axial movement can be effected by an actuator device such as the selection plate 22 described above. The selection plate biases one of the first or second shaft portions, compresses a spring (not shown in the schematic) and forces the gears to engage. When the selected gear is released by the movement of the selection plate 22, the spring (not shown) biases the gears apart. For example, reference will be made to Figure 12 and FIG. 13 to describe further operation of this illustrative embodiment of the drive transmission. Figure 6e The embodiment of can be called a one-way dog clutch, in which the wedge-shaped dog feature (locking means) cannot transmit reverse torque and thus provides a ratchet effect. In this case, the applied torque will force the gear pair apart and simply compress the spring, which promotes engagement. This embodiment enables the selected drive transmission and thus the entire gearbox to also be used as a flywheel.

[0073] Reference Figure 6f, due to the configuration of the locking device, this embodiment can be referred to as a two-way claw clutch, whereby the clutch can transmit reverse torque. In this case, the clutch can transmit reverse torque for applications such as regenerative braking. This embodiment also prevents the gear ratios of the two partially engaged gears from conflicting with each other, which is particularly useful when the actuation of gear ratio change is slow, instantaneously causing the two transmission devices to engage simultaneously.

[0074] The mechanism for achieving selection between respective drive transmission devices to reconfigure the selected drive transmission device between an unlocked configuration and a locked configuration can be implemented in various ways. In the illustrative embodiment presented as Figure 7 shown, an actuator device 71 is used, which includes a selection plate 22 actuated via a linkage 72 by a servo motor 70. Both the servo motor and the linkage cause the selection plate 22 to rotate step by step between various rotational states. The selection plate includes a plurality of selection slots 74. The slots are located in a third plane that is different from the first and second planes occupied by the input gear and its plurality of teeth 18 and the output gear and its plurality of teeth 36 (and correspondingly the first gear 44 and the second gear 46). The selection plate 22 further rotates about the same axis as the input gear structure 8. When the servo motor 70 rotates the selection plate 22, the protrusion 66a of the transmission pin 64 engages or disengages with the corresponding selection slot 74 according to the degree of rotation. The selection slots are chamfered to allow easy positioning and withdrawal from the corresponding selection slots. This means that after or when one transmission pin 64 starts to disengage, it engages with the transmission pins of different drive transmission devices having different selection slots. Since the second gears of the respective drive transmission devices have different numbers of teeth, the plurality of selection slots 74 are arranged at different radial distances from the axis of rotation, advantageously resulting in different pitch circle diameters for the respective selection slots, and thus being able to engage only with any one transmission pin 64 arranged on the same pitch circle diameter. Since the respective drive transmission devices have different gear ratios, this will naturally occur at different pitch circle diameters. Therefore, each transmission pin 64 can only enter or exit a single selection slot 74.

[0075] In an alternative embodiment, the mechanism for reconfiguring individual drive transmission elements can alternatively include an electronic actuator, such as a solenoid. The solenoid will control the position of the transmission pin 64, thus eliminating the need for the reaction force provided by the spring 62 and the actuating force provided by the selection plate 22. Therefore, the disclosed alternative embodiment will have an actuating device including a solenoid, which will replace the need for Figure 1 the servo motor 70, the selection plate 22, and the linkage 72 disclosed in the illustrative embodiment shown in FIGS. 1 to 8.

[0076] In a further alternative embodiment, instead of via a servo motor, the stepwise rotation actuation of the selection plate 22 can be achieved by a conventional mechanical cable system actuated by a controller in the form of a mechanical shifter.

[0077] It should be understood that alternative means can be provided to enable locking and unlocking of the drive transmission 26. For example, individual solenoids can be provided for each drive transmission to actuate the transmission pin so as to select and deselect the locking of that particular drive transmission. For example, such solenoids can be electronically controlled by the user from the handlebar mount via an electronic controller.

[0078] Now referring to Figure 8a and Figure 8b , which shows a gearbox according to an illustrative embodiment of the present invention, the gearbox being combined with an electric motor to provide a motor-gearbox assembly. The motor-gearbox assembly 90 can be provided in a single housing and has, as shown, a drive input that can also optionally be transmitted via the crank arm 12. The output ring gear 93 is shown external to the assembly. It is then connected via a chain or belt to a sprocket mounted on the rear wheel of the bicycle.

[0079] Referring to Figure 8b , the electric motor 92 transmits the drive to the input shaft 30 through a series of helical gears 94, and the input shaft cooperates via the coupling structure 20 in the input gear structure 8 and then through the output gear structure 4. It should be understood that the drive transmission path between the motor and the input gear structure 8 can take other forms, an example of which is the motor directly engaging the first gear 44 of the drive transmission 26. This figure is actually schematic, meaning that the output gear structure 4 will then be connected (or integrally formed) to another ring gear 93 positioned external to the housing so as to be connected forwardly to the rear sprocket. Due to the small axial width of the gearbox, side-by-side mounting of the motor and the gearbox is achieved. Furthermore, a significant advantage of coupling the gearbox according to the present invention with the motor is that due to the high rotational speed of the motor, multiple helical gears are required to provide an output speed suitable for the desired application. However, by utilizing the present invention, the number of helical gears can be reduced.

[0080] Referring to Figure 9a and Figure 9b shows Figure 1Embodiments where there is no pedal crankshaft are shown. This shows that the first and second rotational axes 109, 111 are offset relative to each other, meaning that the gearbox can rotate relative to the bicycle frame, and the eccentric mounting of the output gear relative to the frame enables the tensioning of a chain or belt connected to the rear sprocket driving the rear wheel. Thus, the second axis is not fixed relative to the frame. The gearbox is fixed relative to the frame by a fixing member that secures the mounting structure 113, such as an elongate slot 115 bent to have a common center with the first rotational axis. This means that the gearbox and thus the output gear can rotate to accurately tension the chain or belt.

[0081] The gearbox, in particular the mounting structure, provides a useful torque reaction point 117 that can be used to determine the torque applied to the input gear. Thus, a sensor can be provided to give an output that indicates the torque applied to the input gear. Based on the sensor output and the selected known gear ratio, the torque can be determined and / or a pedal assist signal can be provided to the motor (if present) to control the input torque from the motor. The sensor can be internal and take the form of a strain gauge appropriately positioned and calibrated to detect the applied torque range. Alternatively, the torque sensor can be external and part of a corresponding torque reaction linkage attached to the bicycle frame.

[0082] Reference Figure 10 , the complete wheel assembly includes a sealed internal gearbox and an internal drive transmission configured for one-way torque transfer. By having each drive transmission with its own drive ratio and, for example, a ratchet pawl clutch, the wheel can produce an audible and familiar hub sound comparable to that of other bicycle freewheels, but the key difference is that when a new gear ratio is selected, the audible frequency changes. This gives the cyclist an auditory indication of the gear they are in. Similar to that described with respect to FIG. 9, the main rotational axis (first rotational axis) of the wheel is fixed by a U-shaped slot in the bicycle frame, and the axis of the belt / chain pulley (second rotational axis) is movable to adjust the belt / chain tension. It should be understood that the difference between a hub gearbox and a crankshaft-mounted gearbox is that in Figure 10 the hub gearbox, the input gear is the outermost gear and the output gear is the innermost gear. This is further shown in Figure 11 .

[0083] Reference Figure 11 , an illustrative embodiment of the present invention is presented, which includes an exploded view of a hub gearbox, where the selection plate 22 can be cable-actuated to effect a selection between six drive transmissions 26. As described with respect to the previous embodiments, each drive transmission is held by a carrier 24. In this embodiment, the drive transmissions are as described with respect to Figure 6e or Figure 6fThe device described above, wherein one of the gears 44, 46 is axially displaced according to the position of the selector plate 22 to engage and disengage from the other of the gears 44, 46. A leaf spring or cross spring 121 is provided to act on the selector plate 22, thus disengaging the gears 44, 46 when selecting another gear position. The axle support plate 123, bearings 125a, 125b, 125c and 125d, and the shifter 127 are also shown in the exploded view. The sealing surface attached to the output gear 4 is also shown, which remains in sliding contact with the anti-sealing feature attached to the input gear 8. The components of this embodiment can be made of polymer materials.

[0084] Reference Figure 12 , a drive transmission device 26 is presented, which is particularly suitable for a polymer gearbox with a cable-actuated shift disk. The two cables shown provide a device for two-way displacement without a return spring. A single cable and a return spring or a directly mounted shift lever are alternatives. In this case, a remote twist-type shifter with a double cable can be used. In this embodiment, there is a return spring preferably in the form of a leaf spring or cross spring 121. In the represented embodiment, the concave feature 131 in the selector plate 22 is aligned with a part of the shaft of the intermediate gear, as Figure 12 shown, and the axial displacement of the gears is achieved such that the gears 44, 46 are locked together while remaining engaged with the input gear and the output gear. This spring engages any shaft of the specific drive transmission device 26 allowed by the selector plate 22, so the selector plate 22 can be forced to disengage from a given transmission device, and the spring 121 can quickly engage the next selected gear ratio. The spring is preferably positioned together with the first gear and the second gear, and the first gear and the second gear are axially positioned between the selector device in the form of the selector plate 22 and the spring. It should be understood that any known type of spring, such as a helical spring, can be used. Figure 12 A spring-loaded positioning pin 148 is also shown in [reference], which facilitates the stepped positioning of the selector plate 22, which in turn increases the shifting accuracy and improves the user feedback in the form of an easily detectable click sound. The increased spring stiffness in each transmission box can provide a similar effect.

[0085] Reference Figure 13a and Figure 13b, presents another illustrative embodiment. In this embodiment, no return spring is required to return the gears 44, 46 from the locked configuration to the unlocked configuration. Instead, there are a first structure and a second structure (selector plate 22) axially arranged on either side of the drive transmission 26. When shifting gears, the remote shifter 127 rotates the two selector plates 22a, 22b. The second selector plate 22b has a convex feature 129 instead of a groove and eliminates the return spring. In this case, the two shift disks must be mechanically synchronized (not modeled). The opposing concave features 131 and convex feature 129 of the shift disk pair control the axial position of the gears of the drive transmission 26. In the illustrated embodiment, the convex feature biases a portion of the shaft of the intermediate gear, as Figure 13a shown, and effects an axial displacement of the gears such that the gears 44, 46 are locked together while remaining engaged with the input gear and the output gear (not shown).

[0086] Refer to Figure 14 , presents another illustrative embodiment. In this embodiment, there are separate return springs on opposite sides that return the gears 44, 46 from the locked configuration to the unlocked configuration. (Selector plate 22a) is axially arranged on the opposite side of the drive transmission 26. When shifting gears, the remote shifter 127 rotates the selector plate 22a. In the illustrated embodiment, the convex feature 129 biases a portion of the shaft of the intermediate gear, as Figure 14 shown, and effects an axial displacement of the gears such that the gears 44, 46 are locked together while remaining engaged with the input gear and the output gear (not shown).

[0087] Refer to Figure 15a and Figure 15b , shows a push / pull shift cylinder that has a similar effect to the embodiments shown in Figure 13a and Figure 13b , eliminates the return spring, and serves as an actuator device. In this embodiment, the actuator 135 replaces the selector plate 22. The gear 44a is in the engaged configuration while the gear 44b is in the disengaged configuration. A similar narrower version can also be received within a groove on a laterally movable gear or shaft.

[0088] Refer to Figure 16, in any of the embodiments presented, depending on the gearbox configuration, the input gear and / or the output gear 4, 8 may include annular ribs that increase the peak torque capacity. This is particularly beneficial when the input / output gears and the gears of the drive transmission are made of a polymeric material. The corresponding gears are characterized by a central recess 151 that accepts the ribbed feature. Optionally, we may provide multiple recesses and ribs to increase tooth strength, and the recesses / ribs may be located anywhere along the lateral side of the tooth face. The recesses and ribs may also be used to limit the axial position of the gears for a dog clutch embodiment. It should be understood that the ribs may alternatively be located on the gear, with the corresponding recesses located on the input / output gear.

[0089] Under certain conditions and for certain applications, the gearbox may require the ability to shift gears under high torque conditions. This may occur when the user is climbing a steep hill and wants to quickly change gears without minimizing their torque input. Thus, in such a case, the actuator device may not be able to rotate to effect the switching of the selected drive transmission from the locked configuration to the unlocked configuration. Referring to Figures 17a to 17c , an exploded view and an assembled view of a device for switching between a locked and an unlocked configuration under higher torque conditions are presented. The actuator device in the form of a selector plate 22 is configured to axially deflect (shown in region 141) to a deflected configuration caused by the shaft of the selected drive transmission 26 that still abuts the selector plate 22 with a significant force. A buttress 143 in the form of a shoulder extends inwardly from the input gear structure 8 (or the output gear structure 4 if it is a hub gearbox). Due to the deflection of the selector plate 22, the buttress causes an obstruction to the selector plate 22 (particularly to the structure 147 on the surface of the selector plate 22) due to contact with the buttress, and causes a reversal of the deflection, thereby forcing the stubborn drive transmission back to the unlocked configuration. Then the selection of another gear is achieved.

[0090] Referring to Figure 18 , an alternative version including a rigid selector plate 22 and a thrust plate 145 is presented, where the thrust plate that positions the selector plate 22 is spring-loaded and thus configured to axially move relative to the drive transmission. The axial movement is caused by the shaft of the selected drive transmission 26 that still abuts the selector plate 22 with a significant force. A buttress 143 in the form of a shoulder extends inwardly from the input gear structure 8. Due to the deflection of the selector plate 22, the buttress causes an obstruction to the selector plate 22 (particularly to the structure 147 on the surface of the selector plate 22) due to contact with the buttress, and causes a reversal of the axial movement, thereby forcing the stubborn drive transmission back to the unlocked configuration. Then the selection of another gear is achieved.

[0091] Aspects of the present invention are described by way of example only, and those skilled in the art will appreciate that modifications and variations can be made without departing from the scope of protection provided by the appended claims.

Claims

1. A gearbox for a bicycle, comprising: an input gear configured to receive a drive input and rotate about a first axis of rotation in a first plane; an output gear configured to rotate about a second axis of rotation in a second plane different from the first plane; a plurality of drive transmission means located intermediate the input gear and the output gear, each drive transmission means including a first gear engaged with the input gear, a second gear engaged with the output gear, and a shaft therebetween, each drive transmission means being configurable between a locked configuration and an unlocked configuration, in the locked configuration, rotation of one of the first gear and the second gear causes rotation of the other of the first gear and the second gear such that drive between the input gear and the output gear is enabled, and in the unlocked configuration, the first gear and the second gear rotate independently of each other, thereby disabling drive from the input gear to the output gear; and selection means for selecting one of the plurality of drive transmission means and causing the selected drive transmission means to be reconfigured between the unlocked configuration and the locked configuration.

2. The gearbox for a bicycle according to any one of the preceding claims, wherein the first gear of each drive transmission means is located in the first plane and the second gear of each drive transmission means is located in the second plane.

3. The gearbox for a bicycle according to any one of the preceding claims, wherein each of the first gear and the second gear on at least one of the drive transmission means has a plurality of teeth for engaging with the corresponding input gear and output gear, respectively, wherein the number of teeth on the first gear is different from the number of teeth on the second gear.

4. The gearbox for a bicycle according to any one of the preceding claims, wherein the gear ratio between the first gear and the second gear of a first drive transmission means is different from the gear ratio between the first gear and the second gear of a second drive transmission means.

5. The gearbox for a bicycle according to any one of the preceding claims, wherein the first gear of each drive transmission means is constantly engaged with the input gear.

6. The gearbox for a bicycle according to any one of the preceding claims, wherein the second gear of each drive transmission means is constantly engaged with the output gear.

7. The gearbox for a bicycle according to any one of the preceding claims, wherein the second axis of rotation is different from the first axis of rotation.

8. The gearbox for a bicycle according to any one of the preceding claims, wherein the first gear and the second gear of each drive transmission means rotate about a common axis.

9. The gearbox for a bicycle according to any one of the preceding claims, wherein The selection device includes an actuator device for reconfiguring the selected drive transmission device from the unlocked configuration to the locked configuration, and preferably includes a controller for controlling the actuator device.

10. The gearbox for a bicycle according to claim 9, wherein, the controller includes a shifter configured to receive a user input for transmitting a signal to the actuator device to effect movement of the actuator device.

11. The gearbox for a bicycle according to any one of the preceding claims, wherein, each of the drive transmission devices includes a separate actuator device, preferably wherein each of the separate actuator devices includes a solenoid.

12. The gearbox for a bicycle according to any one of claims 9 to 10, wherein, the actuator device includes a structure rotatably mounted relative to the plurality of drive transmission devices, wherein the structure is arranged to selectively reconfigure the selected drive transmission device between the locked configuration and the unlocked configuration.

13. The gearbox according to any one of the preceding claims, wherein, at least one of the first gear or the second gear is axially movable between the locked configuration and the unlocked configuration.

14. The gearbox according to claim 13, wherein, the first gear and the second gear are axially positioned between the structure and the spring.

15. The gearbox according to claim 11, wherein, the actuator device is configured to be axially deflected to a deflected configuration, and a abutment portion movable with the input gear or the output gear is also provided, wherein the abutment portion and the actuator device are configured to abut in the deflected configuration and force the selected drive transmission device into the unlocked configuration.

16. The gearbox for a bicycle according to any one of the preceding claims, wherein, each of the drive transmission devices is arranged such that one of the first gear or the second gear is fixed relative to the shaft and the other of the first gear or the second gear is rotatably mounted relative to the shaft, and the drive transmission device further includes a locking device arranged to releasably engage the first gear or the second gear rotatably mounted to the shaft and disengage the first gear or the second gear from the shaft such that relative rotation is enabled when disengaged and relative rotation is disabled when engaged.

17. The gearbox for a bicycle according to claim 16, wherein, the locking device includes: one or more locking elements for interlocking the shaft and the first gear or the second gear in the locked configuration; and a pin movable between a first position and a second position, in the first position, the locking element is biased to engage the first gear or the second gear, and in the second position, the locking element is released from engagement with the first gear or the second gear.

18. The gearbox for a bicycle according to claim 17, wherein, The actuator device includes a structure rotatably mounted relative to the plurality of drive transmission devices, and the structure includes a plurality of recesses or abutment portions, wherein each of the recesses or abutment portions is paired with a corresponding pin such that in discrete rotational positions of the structure, when the pin engages with the corresponding paired recess or abutment portion, the paired pin is axially displaced.

19. The gearbox for a bicycle according to claim 18, wherein, when the structure is in one of the discrete rotational positions, only one pin is received in its corresponding paired recess and no other pin is received in its corresponding paired recess.

20. The gearbox for a bicycle according to any one of the preceding claims, wherein, the input gear includes an input gear ring, and the output gear includes an output gear ring, wherein each of the input gear ring and the output gear ring includes a plurality of engaging teeth.

21. The gearbox for a bicycle according to any one of the preceding claims, wherein, the input gear includes coupling means for coupling one or more input shafts to the input gear to transmit the drive input to the input gear.

22. The gearbox for a bicycle according to any one of the preceding claims, wherein, the drive input is a crank arm and / or a motor.

23. The gearbox for a bicycle according to any one of the preceding claims, wherein, in an unlocked configuration, the drive input is transmitted into the input gear through the first gear of the drive transmission means.

24. The gearbox for a bicycle according to claim 21, wherein, the coupling means is configured to be further coupled to a motor for providing an auxiliary drive to the input gear.

25. A gear motor for an electric bicycle, comprising: the gearbox according to any one of the preceding claims; and a motor for providing a drive to the input gear.

26. The gear motor for an electric bicycle according to claim 25, including a reduction gear stage for providing a drive from the motor to the input gear.

27. A power system for an electric bicycle, comprising: the gear motor according to any one of claims 25 to 26; a sprocket for mounting on a wheel of the bicycle; and a chain or a drive belt coupled to the output gear and the sprocket for transmitting the drive from the output gear to the sprocket.

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