WO2024114884A1

WO2024114884A1 - Bicycle transmission system and a control method therefor

Info

Publication number: WO2024114884A1
Application number: PCT/EP2022/083530
Authority: WO
Inventors: Roëll Marie van Druten
Original assignee: Classified Cycling Bv
Priority date: 2022-11-28
Filing date: 2022-11-28
Publication date: 2024-06-06

Abstract

Title: Bicycle transmission system and a control method therefor Abstract The disclosure relates to a bicycle transmission system, comprising a continuously variable transmission (CVT) which is selectively operable according to different transmission ratios within a continuous set of transmission ratios. The transmission system also comprises a control unit. The control unit has a memory that stores one or more discrete subsets of transmission ratios. Each discrete subset is a discrete subset of transmission ratios of the continuous set of transmission ratios. The control unit is configured for controlling the CVT to operate according to a selective one of the one or more discrete subsets of transmission ratios. The CVT is hence controlled to operate as a discrete transmission. The CVT allows for flexibility in the composition of a discrete subset. The distinct transmission ratios of a subset may hence be determined as desired, e.g. to adapted to a further transmission gearing of the transmission system.

Description

Title: Bicycle transmission system and a control method therefor

FIELD

The invention relates to a bicycle transmission systems, particularly to bicycle transmission systems including a continuously variable transmission.

BACKGROUND

Bicycles typically comprise a transmission system with multiple indexed gears that are selectable by a user of the bicycle. Conventional bicycle transmission systems include a derailleur for shifting a chain between differently sized sprockets of a cassette of sprockets. An alternative to derailleurs is formed by hub transmissions where a gear train is provided inside the wheel hub of a driven wheel, and crank transmissions where a gear train is provided inside a crank housing. Hybrid forms are also known where a hub or crank transmission is combined with a derailleur and associated cassette of sprockets.

Some bicycle transmission systems may include a continuously variable transmission (CVT), which is operable according to various transmission ratios within a continuous range of transmission ratios. A CVT allows a user to change the transmission ratio of the CVT in a stepless manner, hence providing a smooth shifting of gears.

SUMMARY

According to an aspect, a bicycle transmission system is provided, comprising a continuously variable transmission (CVT) which is selectively operable according to different transmission ratios within a continuous set of transmission ratios. The transmission system also comprises a control unit. The control unit has a memory that stores one or more discrete subsets of transmission ratios. Each discrete subset is a discrete subset of transmission ratios of the continuous set of transmission ratios. The control unit is configured for controlling the CVT to operate according to a selective one of the one or more discrete subsets of transmission ratios. The CVT is hence controlled to operate as a discrete transmission. The CVT allows for flexibility in the composition of a discrete subset. The distinct transmission ratios of a subset may hence be determined as desired, e.g. to adapted to a further transmission gearing of the transmission system.

A gear change with the transmission system may include a change of the transmission ratio of the CVT from one distinct transmission ratio of the discrete subset to another distinct transmission ratio of the subset. The transmission ratios of the continuous set that lie between the distinct transmission ratios of a discrete subset are not effectively used. The distinct transmission ratios of a discrete subset may correspond to distinct operational settings of the CVT, wherein a gear change with the CVT includes switching from one CVT setting to another CVT setting. The control unit may control the CVT to transit between the different CVT settings, particularly in accordance with a user-commanded gear shift of the transmission system.

The memory may store a plurality of discrete subsets of transmission ratios. Each discrete subset includes a finite number of distinct transmission ratios, e.g. selected from the theoretically infinite set of transmission ratios according to which the CVT is operable.

Optionally, the control unit is configured to automatically determine a discrete subset of transmission ratios and store the automatically determined discrete subset in the memory. The control unit may for example compute a finite number of transmission ratios from the continuous set, forming the discrete subset. The CVT may for example be used in combination with various further transmissions. A discrete subset of transmission ratios for the CVT may hence be automatically determined based on a further transmission with which the CVT is to be combined, to obtain a desired set of system transmission ratios for the transmission system.

Optionally, the control unit is configured for automatically selecting a discrete subset of transmission ratios from the one or more discrete subsets stored in the memory and control the CVT to operate according to the automatically selected discrete subset of transmission ratios. The control unit may hence select an optimal subset of transmission ratios from a plurality of subsets that are stored in the memory.

Optionally, the control unit is configured for controlling the CVT to operate according to a discrete subset of transmission ratios, wherein said discrete subset of transmission ratios is automatically determined and/or automatically selected based on cycling data.

The cycling data for example comprises bicycle hardware data indicative of presence or absence of hardware components of the bicycle and of specific attributes of those hardware components. The bicycle hardware data may for example be indicative of a presence of a further transmission of the transmission system and its associated gearing. The bicycle hardware data may also for example be indicative of a type of bicycle, e.g. whether the bicycle is a road racing bicycle, a gravel bike, a mountain bike, a commuter bike, a cargo bicycle, a light electric vehicle, etc. The bicycle hardware data may also for example be indicative of a presence or absence of an electric propulsion motor, and the power properties of a present propulsion motor.

The cycling data may for example include user data indicative of a user of the bicycle. The user data may for example be indicative of userpreferences, such as a preferred gearing of the transmission system and a preferred cadence, and/or indicative of physical properties of the user, such as a general fitness level, age, body length and weight, a maximum power output, a functional threshold power, a maximal aerobic capacity (VO2 max), maximum heart rate, etc.. The cycling data may for example comprises use data, indicative of a use of the bicycle. The use data may for example be indicative of an intended use of the bicycle, e.g. whether the bicycle is used for riding long steep climbs, predominantly on flat roads, for commuting within a city, for transporting cargo, for indoor training, etc.. The use data may also be indicative of a current or forecasted geographical location of the bicycle, e.g. a planned route of the bicycle, general terrain properties, etc..

The cycling data may be inputted by a user, such as through a user interface, and/or may be obtained from various sensors, such as power sensors, cadence sensors, heart rate monitors, GPS sensors, etc..

Optionally, the bicycle transmission system includes a further transmission. If the transmission system includes a further transmission, the control unit is optionally configured to determine a discrete subset of transmission ratios by obtaining first gearing data indicative of transmission ratios of the further transmission; obtaining second gearing data indicative of desired system transmission ratios for the bicycle transmission system; and computing the discrete subset of transmission ratios for the CVT based on the first gearing data and second gearing data.

Optionally, the transmission system is configured for enabling a user to select, e.g. through a user interface, any one of the one or more discrete subsets of transmission ratios stored in the memory, and control, with the control unit, the CVT according to the user-selected subset.

Optionally, the transmission system is configured for enabling a user to program, e.g. through a user interface, a discrete subset of transmission ratios by appointing a finite number of different transmission ratios within the continuous set of transmission ratios, and storing the appointed transmission ratios as a discrete subset in the memory.

Optionally, the control unit is configured for switching from controlling the CVT according to one of the one or more subsets of transmission ratios to controlling the CVT according to any other one of the one or more subsets of transmission ratios, in particular while the bicycle is in use.

Optionally, each transmission ratio of the one or more discrete subsets of transmission ratios has a predetermined continuous fine- adjustment range associated therewith, and wherein the control unit is configured for, while controlling the CVT according to a transmission ratio of one of the one or more subsets of transmission ratios, adjusting said transmission ratio within the associated predetermined continuous fine- adjustment range based on a user-input. Hence, a fine-adjustment to the system transmission ratio can be made, by fine-adjusting the transmission ratio of the CVT. A cadence, i.e. the number of bicycle crank revolutions per time interval, can hence be fine-adjusted if desired. The fine-adjustment range for a certain transmission ratio of the CVT may particularly be smaller than a step size from said transmission ratio to a successive transmission ratio.

Optionally, the control unit is configured tracking a cadence set point by adjusting the transmission ratio within the associated predetermined continuous fine-adjustment range. For example, the control unit may be configured for determining, based on a sensed cadence-related parameter, an appropriate CVT transmission ratio so as to obtain and/or maintaining a cadence value at the cadence set point, and automatically adjusting the CVT transmission ratio to the determined appropriate transmission ratio. Hence, the CVT can be used for accurately tracking the cadence set point.

Optionally, the control unit is configured for upshifting or downshifting the CVT from a current CVT transmission ratio of the discrete subset to a higher or lower CVT transmission ratio of the discrete subset, in case the appropriate CVT transmission ratio is outside of the fine- adjustment range of the current CVT transmission ratio. Optionally the transmission system is configured for enabling a user to select and adjust the cadence set point while cycling, e.g. through a user interface. The user interface may for example include a manually operable switch, such as a rotary switch, by means of which the user can increase and decrease the cadence set point according to his/her preference.

According to another aspect, a method for controlling a bicycle transmission system is provided. The bicycle transmission system comprises a continuously variable transmission (CVT) selectively operable according to different transmission ratios within a continuous set of transmission ratios. The transmission system also includes a control unit having a memory that stores one or more discrete subsets of transmission ratios, each discrete subset being a discrete subset of transmission ratios of the continuous set of transmission ratios. The method comprises controlling the CVT with the control unit to operate according to a selective one of the one or more discrete subsets of transmission ratios stored in the memory.

In a general sense, the method relates to a use of a continuously variable transmission (CVT) in a bicycle transmission system, the CVT being selectively operable according to different transmission ratios within a continuous set of transmission ratios, comprising operating the CVT according to a selective one of a plurality of different discrete subsets of the set of transmission ratios.

Optionally, the method comprises automatically determining, with the control unit, a discrete subset of transmission ratios and store the automatically determined discrete subset in the memory.

Optionally, the method comprises automatically selecting a discrete subset of transmission ratios from the one or more discrete subsets stored in the memory and control the CVT to operate according to the automatically selected discrete subset of transmission ratios.

Optionally, the method comprises automatically determining and/or automatically selecting a discrete subset of transmission ratios based on cycling data, wherein the cycling data for example comprises one or more of bicycle hardware data, user data, and use data. The hardware data may be indicative of presence or absence of hardware components of the bicycle and of specific attributes of those hardware components. The user data may be indicative of a user of the bicycle. The use data may be indicative of a use of the bicycle.

Optionally, the bicycle transmission system includes a further transmission, wherein the determining of the discrete subset of transmission ratios includes having the control unit obtain first gearing data indicative of transmission ratios of the further transmission; having the control unit obtain second gearing data indicative of desired system transmission ratios for the bicycle transmission system; and having the control unit compute the discrete subset of transmission ratios for the CVT based on the first gearing data and second gearing data. The further transmission may particularly be a discrete transmission that is operable according to a finite invariable discrete set of transmission ratios.

Optionally, the method comprises having a user select, e.g. through a user interface, any one of the one or more discrete subsets of transmission ratios stored in the memory, and control the transmission unit according to the user-selected subset.

Optionally, the method comprises having a user program, e.g. through a user interface, a discrete subset of transmission ratios by appointing a finite number of different transmission ratios within the continuous set of transmission ratios, and storing the appointed transmission ratios as a discrete subset in the memory.

Optionally, the method comprises switching from controlling the CVT according to the selective one of the one or more subsets of transmission ratios to controlling the CVT according to another one of the one or more subsets of transmission ratios, in particular while riding the bicycle. The method may further comprise switching from controlling the further transmission according to one of its respective transmission ratios to controlling the further transmission according to another one of its respective transmission ratios, in particular while riding the bicycle.

Optionally, each transmission ratio of the one or more discrete subsets of transmission ratios has a predetermined continuous fine- adjustment range associated therewith, and wherein the method comprises, while controlling the CVT according to a transmission ratio of one of the one or more subsets of transmission ratios, adjusting said transmission ratio within the associated predetermined continuous fine-adjustment range based on a user-input.

According a further aspect, a transmission system for a bicycle is provided. The transmission system of this aspect may be in accordance with any other aspect described herein. The transmission system comprises a continuously variable transmission (CVT) selectively operable according to different transmission ratios within a continuous set of transmission ratios. The control unit has a memory that stores a cadence set point. The control unit is configured for determining, based on a sensed cadence-related parameter, an appropriate CVT transmission ratio so as to obtain and/or maintaining a cadence value at the cadence set point, and automatically controlling the CVT to operate according to the determined appropriate transmission ratio. Hence, the CVT can be used for accurately tracking the cadence set point. The control unit can particularly make substantially continuous adjustments to the CVT transmission ratio, thus allowing for accurate and perceptually seamless tracking of the cadence set point. When a user for example increases its output power and accelerates the bicycle, the CVT transmission ratio may be adjusted accordingly by the control unit so as to maintain a constant cadence. The cadence set point may for example be defined by the user, e.g. reflecting a personal preference. The cadence set point may be defined as the number of bicycle crank revolutions per time interval. Optionally, the sensed cadence-related parameter includes one or more of a sensed cadence value, a sensed crank speed, a sensed operating speed of the bicycle, a sensed rotation speed of a wheel of the bicycle, a sensed user-output. The cadence value need not be measured directly, but can also be inferred from other parameters, such as from the operating speed of the bicycle, the rotation speed of a wheel of the bicycle and the sensed user-output such as a user’s power-output or torque-output. The sensed cadence value itself may in some instances not be accurate as user may occasionally stop pedaling. The sensed cadence value would hence be zero in these instances, while this does not a appropriate reflection of the actual cadence. Secondary indicators may hence be used instead, or in addition, to estimate a current cadence value.

Optionally, the transmission system further comprises a discrete transmission, connectable in series with the CVT, and selectively operable according to a plurality of different discrete transmission ratios.

Optionally, the control unit is configured for determining, based on the sensed cadence-related parameter, an appropriate system transmission ratio for the transmission system so as to obtain and/or maintaining a cadence value at the cadence set point, and based on the appropriate system transmission ratio, determine an appropriate discrete transmission ratio for the discrete transmission and the appropriate CVT transmission ratio for the CVT for forming the appropriate system transmission ratio, and automatically correspondingly controlling the discrete transmission and the CVT to operate according to their respective determined appropriate transmission ratio. As the CVT may have a limited range, it may be necessary to also shift a further transmission of the transmission system. The system transmission ratio may be defined as the transmission ratio provided by the transmission system between the transmission system input and the transmission system output. In may hence be formed by the transmissions between the transmission system input and the transmission system output. The system transmission ratio may hence be formed, at least in part, by the CVT transmission ratio and the discrete transmission ratio.

Optionally, the control unit is configured to determine the appropriate CVT transmission ratio at a current discrete transmission ratio of the discrete transmission; determine whether the appropriate CVT transmission ratio is inside or outside of the continuous set; and automatically upshift or downshift the discrete transmission from the current discrete transmission ratio to a higher or lower transmission ratio in case the determined appropriate CVT transmission ratio is outside of the continuous set.

Optionally the transmission system is configured for enabling a user to select and adjust the cadence set point while cycling, e.g. through a user interface. The user interface may for example include a manually operable switch, such as a rotary switch, by means of which the user can increase and decrease the cadence set point according to his/her preference.

According to another aspect, a method for controlling a bicycle transmission system is provided. The bicycle transmission system comprises a continuously variable transmission (CVT) selectively operable according to different transmission ratios within a continuous set of transmission ratios. The bicycle transmission may be in accordance with any bicycle transmission described herein. The bicycle transmission comprises a control unit having a memory that stores a cadence set point. The method comprises determining, based on a sensed cadence-related parameter, an appropriate CVT transmission ratio so as to obtain and/or maintaining a cadence value at the cadence set point, and automatically controlling the CVT to operate according to the determined appropriate transmission ratio.

Optionally, the transmission system further comprises a discrete transmission, connectable in series with the CVT, and selectively operable according to a plurality of different discrete transmission ratios. Optionally, the method comprises determining, based on the sensed cadence-related parameter, an appropriate system transmission ratio for the transmission system so as to obtain and/or maintaining a cadence value at the cadence set point; determining, based on the appropriate system transmission ratio, an appropriate discrete transmission ratio for the discrete transmission and the appropriate CVT transmission ratio for the CVT for forming the appropriate system transmission ratio; and automatically correspondingly controlling the discrete transmission and the CVT to operate according to their respective determined appropriate transmission ratio.

Optionally, the method comprises determining the appropriate CVT transmission ratio at a current discrete transmission ratio of the discrete transmission; determining whether the appropriate CVT transmission ratio is outside of the continuous set; and automatically upshifting or downshifting the discrete transmission from the current discrete transmission ratio to a higher or lower transmission ratio in case the determined appropriate CVT transmission ratio is outside of the continuous set.

Optionally, the method comprises having a user select and adjust the cadence set point while cycling, e.g. through a user interface.

According to an aspect, a bicycle is provided comprising a transmission system as described herein. It will be appreciated that a bicycle encompasses similar human-powered vehicles, particularly pedal- powered, such as tricycles, quadricycles, etc. The bicycle transmission may be embodied as a hub transmission of the bicycle and/or as a crank transmission of the bicycle.

According to an aspect, an electrically powered vehicle is provided, such as a light electrically powered vehicle for example an electrically powered bicycle or scooter. The electrically powered vehicle comprises a bicycle transmission as described herein, and an electric propulsion motor having an output power of maximum 10 kW, preferably maximum 4 kW; the electric propulsion motor being arranged for propelling, or assist in propelling the vehicle, wherein the propulsion motor output power is transmitted at least partly through the bicycle transmission.

It will be appreciated that any of the aspects, features and options described herein can be combined. It will particularly be appreciated that any of the aspects, features and options described in view of the transmission system apply equally to the method, and vice versa.

BRIEF DESCRIPTION OF THE DRAWINGS

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

Figures 1 and 2 show examples of a bicycle transmission system;

Figure 3 shows a bicycle.

DETAILED DESCRIPTION

Figure 1 shows a schematic example of a transmission system 10, comprising a continuously variable transmission CVT 1, and a control unit 2 having a memory 3. The CVT 1 is selectively operable according to a plurality of different transmission ratios within a continuous set of transmission ratios. The CVT 1 may be any kind of CVT. An example of suitable CVT 1 is described in PCT/EP2022/060915, the entire contents of which are incorporated herein by refence. The control unit 2 is operatively connected to the CVT 1, for controlling the CVT 1. The memory 3 of the control unit 2 stores one or more discrete subsets of the continuous set of transmission ratios. Hence, each discrete subset includes a finite number of transmission ratios, which have been selected from the theoretically infinite number of transmission ratios of the continuous set of transmission ratios of the CVT 1. The control unit 2 is particularly arranged for controlling the CVT 1 to operate according to a selective one of the one or more subsets of transmission ratios. The control unit 2 may for example control an actuator of the CVT 1, to change an operational setting of the CVT 1 in accordance with the transmission ratios of a particular discrete subset.

The memory 3 may store a plurality of different discrete subsets of transmission ratios. A user may for example select any one of the discrete subsets stored in memory 3, and have the control unit 2 control the CVT 1 accordingly. A user may also have a discrete subset of transmission ratios stored in the memory 3.

Additionally or alternatively, the memory 3 may store a cadence set point. A user may for example select a desired cadence set point and/or adjust the cadence set point.

Figure 2 shows a schematic example of the transmission system 10, including a user interface 4 through which a user can interact with the control unit 2. The user interface 4 may be part of the control unit. Through the user interface 4, the user may for example have a discrete subset of transmission ratios stored in the memory 3, and/or select any one of the discrete subsets stored in the memory 3 for having the CVT 1 controlled accordingly. Additionally or alternatively, through the user interface, the user may have a cadence set point stored in the memory 3, and/or adjust and select any cadence set points stored in the memory 3.

It will be appreciated that the user interface 4 may include various input means for receiving user inputs from the user, and various output means for providing the user with feedback. In a particular example, the user interface 4 may include a bicycle computer and/or a general purpose computer, such as a smart phone. Also, the user interface may include a switch, such as a rotary switch, for allowing the user to manually adjust the cadence set point.

In the example of figure 2, the transmission system 10 comprises a further transmission 5, which is here connected to the CVT 1 in series. The further transmission 5 is in this example a discrete transmission that is selectively operable according to a plurality of different discrete transmission ratios. The further transmission 5 may for example comprise a gear train, such as a planetary gear set, and/or derailleur system. The control unit 2 is in this example configured for controlling the further transmission. The control unit 2 may for example control a shift actuator of the further transmission 5, for shifting gears of the further transmission 5. Hence, in this example, the CVT 1 and the further transmission 5 can collaboratively provide various transmission ratios.

The memory 3 of the control unit 2 may store a discrete subset of transmission ratios for the CVT 1 that is adapted to the gearing of the further transmission 5. This way, a suitable set of system transmission ratios can be obtained, e.g. with appropriate steps between successive transmission ratios. The control unit 2 may for example be configured to compute a discrete subset of transmission ratios for the CVT 1 based on the gearing of the further transmission 5 and store the computed discrete subset in the memory 3. The control unit 2 may also be configured to select an appropriate discrete subset of transmission ratios from the one or more discrete subsets stored in the memory 3, and control the CVT 1 accordingly. A user can for example input through the user interface whether the further transmission is present, and characteristics of the further transmission, such as its particular gearing. The control unit 2 may also be configured to automatically detect the presence of the further transmission and the CVT 1, and characteristics of those transmissions. This may be useful for modular transmission systems where multiple transmission modules can be coupled together.

The memory 3 of the control unit 2 may store a discrete subset of transmission ratios for the CVT 1 that is adapted to a preference of a user. The user may for example select, from the discrete subsets stored in the memory 3, a desired subset of transmission ratios, e.g. that suits an intended type of riding. For example, if the user intends on riding the bicycle predominantly uphill, an appropriate discrete subset can be selected that provides many small increments between high gears of the transmission system. The user may for example select a desired discrete subset through the user interface, e.g. prior to riding the bicycle and/or whilst riding the bicycle.

Additionally or alternatively, the control unit 2 may be configured to automatically select and/or automatically determine a discrete subset of transmission ratios for the CVT 1. Such automatic selection and/or determination may be based on various aspects, including but not limited to

- bicycle hardware aspects, e.g. a presence or absence of hardware components of the bicycle and of specific attributes of those hardware components, such as whether the bicycle is a road racing bicycle, a gravel bike, a mountain bike, a commuter bike, a cargo bicycle, a light electric vehicle, and whether an electric propulsion motor is present;

- user aspects such as preferences and attributes of a user of the bicycle, e.g. a preferred gearing of the transmission system and preferred cadences, physical properties of the user, such as a general fitness level, age, body length and weight, a maximum power output, a functional threshold power, a maximal aerobic capacity (VO2 max), maximum heart rate;

- cycling aspects, e.g. an intended use of the bicycle, such as for riding long steep climbs, predominantly on flat roads, for commuting within a city, for transporting cargo, for indoor training, and current and forecasted geographical location of the bicycle.

Any of such aspects may be inputted by a user, such as through the user interface 4, and/or may be obtained from various sensors 6, such as speed sensors, power sensors, cadence sensors, heart rate monitors, GPS sensors, etc..

The example of figure 2 also includes a shifter device 7 that is manually operable by a user for commanding gear shift. The shifter device 7 may for example be provided at a handle bar of the bicycle and configured for transmitting a shift signal upon actuation of the shifter device 7. The shift signal may for example be an upshift signal for commanding an upshift to higher gear or a downshift signal for commanding a downshift to a lower gear. The control unit 2 is configured for receiving the shift signal, and accordingly control the CVT 1 and in this example also the further transmission 5. The shifter device 7 may be part of the user interface 4. Hence, a user may for example select a discrete subset of transmission ratios stored in the memory using the shifter device 7. For example, the transmission system 10 may be brought into a subset selection mode, e.g. using a dedicated switch or predetermined sequence of actuations with the shifter device, wherein, while in the subset selection mode, the upshift signal may select a next discrete subset stored in the memory 2 and the downshift signal may select a previous discrete subset stored in the memory 2.

In an example, the further transmission 5 is selectively operable according to four different transmission ratios Rl, R2, R3 and R4. The CVT 1 is operable according to any transmission ratio RCVT within a continuous set of transmission ratios, e.g. from 1.00 to 1.50. The user may for example input through the user interface 4 to preferably have a seventeen-speed transmission system 10, with a substantially constant step between successive transmission ratios of about nine percent. A discrete subset of transmission ratios for the CVT 1, e.g. RCVT_1, RCVT_2, RCVT_3, RCVT_4, may be determined based on hereon, as given in table 1. Table 1

In the example of table 1, the discrete subset of transmission ratios for the CVT 1 includes only five different transmission ratios, here RCVT_1 to RCVT_4. The control unit 2 may thus control the CVT 1 in accordance with this exemplary discrete subset of transmission ratios, for example, by switching the CVT between only five different CVT settings. The control unit 2 also controls the further transmission 5 in accordance with the system transmission ratios. The control unit may for example be configured to receive an upshift or downshift signal from a manually operable shifter device, and control the further transmission 5 and the CVT 1 accordingly, to obtain respectively the next higher or lower system transmission ratio.

In another example, using the same further transmission 5 and the same CVT 1 as the example of table 1, a nine-speed transmission system can be obtained, wherein a step size between successive system transmission ratios is constant and about nineteen percent, as given in table 2. Such system transmission ratios may for example be suitable for city commuting.

Table 2

In another example, using the same further transmission 5 and the same CVT 1 as the example of tables 1 and 2, a fourteen-speed transmission system can be obtained, wherein a step size between successive system transmission ratios is progressively increasing, as given in table 3. Such system transmission ratios may be suitable for uphill cycling. Table 3

Figure 3 shows a bicycle 100. The bicycle 100 comprises a frame 102 with a front fork 105 and a rear fork 107, as well as a front wheel and a rear wheel 111, 113 located in the front and rear fork respectively. The bicycle 100 also comprises a crank 117, and a front chain wheel 119 connected to each other. The bicycle 100 also comprises a rear sprocket 121 and a rear wheel hub 122 of the rear wheel 113, wherein a chain 123 threads over the front chain wheel 119 and the rear sprocket 121. The bicycle 100 comprises a transmission system 10 as described herein. In this example, the transmission system 10 includes the further transmission 5. The further transmission 5 is in this example embodied as a hub transmission that is housed by the rear wheel hub 122. The CVT 1 of the transmission system 10 is here arranged in a transmission path between the rear sprocket 121 and the further transmission 5. The control unit 2 is in this example housed by the frame 102. The control unit may be wiredly or wireless connected to the further transmission 5 and the CVT 1. A user interface 4, here formed by a bicycle computer, is mounted to the handlebars 131, for allowing a user to interface with the control unit 2.

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.

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.

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

1. A transmission system for a bicycle, comprising: a continuously variable transmission (CVT) selectively operable according to different transmission ratios within a continuous set of transmission ratios; and a control unit having a memory that stores one or more discrete subsets of transmission ratios, each discrete subset being a discrete subset of transmission ratios of the continuous set of transmission ratios, wherein the control unit is configured for controlling the CVT to operate according to a selective one of the one or more discrete subsets of transmission ratios.

2. The transmission system of claim 1, wherein the control unit is configured to automatically determine a discrete subset of transmission ratios and store the automatically determined discrete subset in the memory.

3. The transmission system of claim 1 or 2, wherein the control unit is configured for automatically selecting a discrete subset of transmission ratios from the one or more discrete subsets stored in the memory and control the CVT to operate according to the automatically selected discrete subset of transmission ratios.

4. The transmission system of claim 2 or 3, wherein control unit is configured for controlling the CVT to operate according to a discrete subset of transmission ratios, wherein said discrete subset of transmission ratios is automatically determined and/or automatically selected based on cycling data, wherein the cycling data for example comprises one or more of: - a further transmission of the transmission system, such as a presence of the further transmission and/or a transmission ratio of the further transmission;

- an intended use of the bicycle;

- a current and/or forecasted geographical location of the bicycle;

- a bicycle type;

- a presence or absence of an electric propulsion motor;

- a fitness level of a user of the bicycle

5. The transmission system of claim 2, or claim 3 or 4 when dependent on claim 2, wherein the bicycle transmission system includes a further transmission, and wherein the control unit is configured to determine the discrete subset of transmission ratios by obtaining first gearing data indicative of transmission ratios of the further transmission; obtaining second gearing data indicative of desired system transmission ratios for the bicycle transmission system; computing the discrete subset of transmission ratios for the CVT based on the first gearing data and second gearing data.

6. The transmission system of any preceding claim, configured for enabling a user to select, e.g. through a user interface, any one of the one or more discrete subsets of transmission ratios stored in the memory, and control the CVT according to the user-selected subset.

7. The transmission system of any preceding claim, configured for enabling a user to program, e.g. through a user interface, a discrete subset of transmission ratios by appointing a finite number of different transmission ratios within the continuous set of transmission ratios, and storing the appointed transmission ratios as a discrete subset in the memory.

8. The transmission system of any preceding claim, wherein the control unit is configured for switching from controlling the CVT according to one of the one or more subsets of transmission ratios to controlling the CVT according to any other one of the one or more subsets of transmission ratios, in particular while the bicycle is in use.

9. The transmission system of any preceding claim, wherein each transmission ratio of the one or more discrete subsets of transmission ratios has a predetermined continuous fine-adjustment range associated therewith, and wherein the control unit is configured for, while controlling the CVT according to a transmission ratio of one of the one or more subsets of transmission ratios, adjusting said transmission ratio within the associated predetermined continuous fine-adjustment range based on a user-input.

10. The transmission system of claim 9, wherein the control unit is configured tracking a cadence set point by adjusting the transmission ratio within the associated predetermined continuous fine-adjustment range.

11. A method for controlling a bicycle transmission system, wherein the bicycle transmission system comprises a continuously variable transmission (CVT) selectively operable according to different transmission ratios within a continuous set of transmission ratios and a control unit having a memory that stores one or more discrete subsets of transmission ratios, each discrete subset being a discrete subset of transmission ratios of the continuous set of transmission ratios; wherein the method comprises controlling the CVT with the control unit to operate according to a selective one of the one or more discrete subsets of transmission ratios stored in the memory.

12. The method of claim 11, comprising automatically determining, with the control unit, a discrete subset of transmission ratios and store the automatically determined discrete subset in the memory.

13. The method of claim 11 or 12, comprising automatically selecting a discrete subset of transmission ratios from the one or more discrete subsets stored in the memory and control the CVT to operate according to the automatically selected discrete subset of transmission ratios.

14. The method of claim 12 or 13, comprising automatically determining and/or automatically selecting a discrete subset of transmission ratios based on cycling data, wherein the cycling data for example comprises one or more of:

- a further transmission of the transmission system, such as a presence of the further transmission and/or a gearing of the further transmission;

- an intended use of the bicycle;

- a current and/or forecasted geographical location of the bicycle;

- a bicycle type;

- a presence or absence of an electric propulsion motor;

- a fitness level of a user of the bicycle.

15. The method of claim 12, or claim 13 or 14 when dependent on claim 12, wherein the bicycle transmission system includes a further transmission, and wherein the determining of the discrete subset of transmission ratios includes having the control unit obtain first gearing data indicative of transmission ratios of the further transmission; having the control unit obtain second gearing data indicative of desired system transmission ratios for the bicycle transmission system; having the control unit compute the discrete subset of transmission ratios for the CVT based on the first gearing data and second gearing data.

16. The method of any of claims 11-15, comprising having a user select, e.g. through a user interface, any one of the one or more discrete subsets of transmission ratios stored in the memory, and control the transmission unit according to the user-selected subset.

17. The method of any of claims 11-16, comprising having a user program, e.g. through a user interface, a discrete subset of transmission ratios by appointing a finite number of different transmission ratios within the continuous set of transmission ratios, and storing the appointed transmission ratios as a discrete subset in the memory.

18. The method of any of claims 11-17, comprising switching from controlling the CVT according to the selective one of the one or more subsets of transmission ratios to controlling the CVT according to another one of the one or more subsets of transmission ratios, in particular while riding the bicycle.

19. The method of any of claims 11-18, wherein each transmission ratio of the one or more discrete subsets of transmission ratios has a predetermined continuous fine-adjustment range associated therewith, and wherein the method comprises, while controlling the CVT according to a transmission ratio of one of the one or more subsets of transmission ratios, adjusting said transmission ratio within the associated predetermined continuous fine-adjustment range based on a user-input.

20. A transmission system for a bicycle, such as in accordance with any preceding claim, comprising: a continuously variable transmission (CVT) selectively operable according to different transmission ratios within a continuous set of transmission ratios; and a control unit having a memory that stores a cadence set point; wherein the control unit is configured for determining, based on a sensed cadence-related parameter, an appropriate CVT transmission ratio so as to obtain and/or maintaining a cadence value at the cadence set point, and automatically controlling the CVT to operate according to the determined appropriate transmission ratio.

21. The transmission system of claim 20, wherein the sensed cadence- related parameter includes one or more of a sensed cadence value, a sensed operating speed of the bicycle, a sensed rotation speed of a wheel of the bicycle, a sensed user-output.

22. The transmission system of claim 20 or 21, further comprising a discrete transmission, connectable in series with the CVT, and selectively operable according to a plurality of different discrete transmission ratios.

23. The transmission system of claim 22, wherein the control unit is configured for determining, based on the sensed cadence-related parameter, an appropriate system transmission ratio for the transmission system so as to obtain and/or maintaining a cadence value at the cadence set point, and based on the appropriate system transmission ratio, determine an appropriate discrete transmission ratio for the discrete transmission and the appropriate CVT transmission ratio for the CVT for forming the appropriate system transmission ratio, and automatically correspondingly controlling the discrete transmission and the CVT to operate according to their respective determined appropriate transmission ratio.

24. The transmission system of claim 22 or 23, wherein the control unit is configured to determine the appropriate CVT transmission ratio at a current discrete transmission ratio of the discrete transmission; determine whether the appropriate CVT transmission ratio is outside of the continuous set; and automatically upshift or downshift the discrete transmission from the current discrete transmission ratio to a higher or lower transmission ratio in case the determined appropriate CVT transmission ratio is outside of the continuous set.

25. The transmission system of any of claims 20-24, configured for enabhng a user to select and adjust the cadence set point while cycling, e.g. through a user interface.

26. A method for controlling a bicycle transmission system wherein the bicycle transmission system comprises a continuously variable transmission (CVT) selectively operable according to different transmission ratios within a continuous set of transmission ratios and a control unit having a memory that stores a cadence set point, wherein the method comprises determining, based on a sensed cadence-related parameter, an appropriate CVT transmission ratio so as to obtain and/or maintaining a cadence value at the cadence set point, and automatically controlling the CVT to operate according to the determined appropriate transmission ratio.

27. The method of claim 26, wherein the transmission system further comprises a discrete transmission, connectable in series with the CVT, and selectively operable according to a plurality of different discrete transmission ratios.

28. The method of claim 27, comprising determining, based on the sensed cadence-related parameter, an appropriate system transmission ratio for the transmission system so as to obtain and/or maintaining a cadence value at the cadence set point; determining, based on the appropriate system transmission ratio, an appropriate discrete transmission ratio for the discrete transmission and the appropriate CVT transmission ratio for the CVT for forming the appropriate system transmission ratio; and automatically correspondingly controlling the discrete transmission and the CVT to operate according to their respective determined appropriate transmission ratio.

29. The method of claim 27 or 28, comprising determine the appropriate CVT transmission ratio at a current discrete transmission ratio of the discrete transmission; determine whether the appropriate CVT transmission ratio is outside of the continuous set; and automatically upshift or downshift the discrete transmission from the current discrete transmission ratio to a higher or lower transmission ratio in case the determined appropriate CVT transmission ratio is outside of the continuous set.

30. The method of any of claims 26-29, comprising having a user select and adjust the cadence set point while cycling, e.g. through a user interface.

31. A bicycle comprising a transmission system in accordance with any of claims 1-10 and/or any of claims 20-25.