EP2739523A1

EP2739523A1 - Method and device for shifting gears on an electric bicycle

Info

Publication number: EP2739523A1
Application number: EP13707263.3A
Authority: EP
Inventors: Jakub Ryba; Milan KREN; David VISEK
Original assignee: Mraz Richard
Current assignee: Mraz Richard
Priority date: 2012-10-16
Filing date: 2013-01-29
Publication date: 2014-06-11
Also published as: WO2014059953A1

Abstract

The electric bicycle (1) is equipped with a central electric motor (2) to assist the drive of the chainwheel (3), which uses a chain (8) to power a driven wheel (9). In order to eliminate the shocks and stress on the front derailleur (14) of chainwheel (3), rear derailleur (17), and other parts of the bicycle (1) when shifting gears while the electric motor (2) is providing power, in accordance with the invention, the bicycle (1) is equipped with motion sensors (22, 23), which detect the movement of the front and rear derailleur shifter (12, 15) or inner cables (13, 16), and using an electrical signal fed to the electronic control unit (20) cause the elimination of the effect of the electric motor (2) or a reduction of its torque acting on the chainwheel (3) during gear shifting. The design improves riding comfort and increases the life span of the gearshifting equipment, particularly allowing for a wide use of multi-row chainwheels (3) with front derailleurs (14) in combination with a central electric motor (2) on power assisted electric bicycles (1).

Description

Method and device for shifting gears on an electric bicycle

Field of the invention

The invention relates a method and device for shifting gears on an electric bicycle with a power-assist or main electric motor whose power is transferred to a chainwheel then through a chain to the driven wheel.

Background of the invention

A bicycle fitted with a power-assist or main electrical drive system uses electrical power either directly in the hub of the driven wheel or is equipped with a central electric drive which is set up so that its power is transferred through a chainwheel to the driven wheel. Systems with^' a central electric drive have the advantage over hub drive systems in that they make better use of energy, which is very important for electric bicycles with a limited driving range.

Bicycles with a central electric drive are prevented from further expansion due to technical problems associated with the transfer of torque from the chainwheel to the driven wheel when gears are shifted using a hand-operated, electric, or hydraulic derailleur.

The most extended feature for shifting gears on an electric bicycle is provided by a multi-row chainwheel connected with a bottom bracket axle with crank arms equipped with pedals, from which the chain runs to a multi-row sprocket on the hub of the driven wheel. Gears are shifted using a derailleur shifter (lever shifter or twist grip shifter on the handlebars) which uses an inner cable to control the front derailleur on a multi-row chainwheel or a rear derailleur on a multi-row sprocket. When a central^~~electric ¹ motor is connected to this system, the problem of switching gears during motor thrust arises. The torque of the motor applies a constant pull on the chain. This pull is very difficult to overcome with a front derailleur even when the front derailleur is powered differently than with a hand lever shifter or twist grip. When the gears are shifted, then, the chain either does not shift to the next sprocket of the multi-rowed chainwheel, or the shift is inaccurate. This often results in the chain jumping and being bent excessively sideways, or in the chain breaking, jamming, or falling off.

The strong shocks that occur when the chain jumps lead to excessive chain wear and even reduce operation safety as a result of an unexpected chain defect. Riding the bicycle then becomes uncomfortable, and shifting gears is very noisy. Most manufacturers of power-assisted electric bicycles tend to use a gear shifting design in which the central electric motor drives only a single-rowed chainwheel, from which the chain runs to a multi-row sprocket on the driven wheel which is fitted with a standard rear derailleur. Even this design, however, suffers from disadvantages consisting of excessive wear on the sprocket, chain, and rear derailleur. Operation is noisy and jerky during gear shifting, adjustment of the gear- shifting mechanism is difficult, and life span is short.

An alternative design is a combination of a single-row chainwheel, from which the chain leads to a single-row sprocket which is connected to an internal hub gear located inside the hub of the driven wheel. Even with this design, however, the ability of the internal hub gear to change gears is very limited due to the permanent tension of the chain. The internal hub gear must be very strongly constructed, which is problematic while maintaining required constructional dimensions and weight.

From the perspective of electric motor operation design, there are systems known which switch off the motor when the brakes are applied. A sensor notes the movement of the brake cable and deactivates the motor during braking. There are also systems known, e.g. in accordance with EP 0816215A1, in which a sensor fitted on the derailleur control cable evaluates which gear has been shifted and monitors the pedalling frequency and riding speed for the electronic control of the motor's immediate power in order to achieve the optimal level of assisted drive. There is no system known, however, which would resolve control of the electric motor during the shifting of the gears.

At present, manufactures of bicycles with a central electric assisted drive, as a result of the aforementioned problems, are forced to use single-row chainwheels combined with multi- row driven sprockets. This design is unable to provide the required range of gears at the moment of forced disconnection of drive due to insufficient energy in the battery, with the simultaneous need to complete the route without support of the motor, particularly in hilly terrain.

The task of this invention is to create a method and device for shifting the gears on a bicycle which would allow for the use of a central electric motor which drives a multi-row chainwheel and, through a chain, a multi-row sprocket on the driven wheel, and in which shifting gears is possible using a normal front and rear derailleur without the gear shifting process showing the aforementioned inadequacies. The method and device should be usable for other gear-shifting mechanisms as well, e.g. for internal geared hubs inside the hub axle of the driven wheel.

Summary of the invention

The formulation of the task is resolved by the creation of a method and device for shifting gears on an electric bicycle according to the present invention.

The invention relates the method of shifting gears on a bicycle fitted with an assisted-power or main electric motor powering a chainwheel which includes at least one chain- driving sprocket, in which the chainwheel is alternately or simultaneously driven via a bottom bracket axle equipped with crank arms and pedals, also in which the chainwheel, using a chain, drives a wheel equipped with a sprocket which includes ,at least one chain-driven sprocket, while the gear shift takes place using the front derailleur shifter which uses an inner cable to control a front derailleur and/or using a rear derailleur shifter which uses an inner cable to control a rear derailleur of a sprocket or an internal geared hub of the driven wheel. The essence of the invention is that the movement of the derailleur shifter or inner cable during a gear shift is converted into an electrical signal which is fed directly or indirectly to the electric motor, and this results in a reduction of the torque value or to the complete elimination of the transfer of torque of the electric motor to the chainwheel during gear shift, then after the gear shifting is completed, the value of the torque increases again or the transfer of the torque is re-activated from the electric motor to the chainwheel. During gear shifting, the stress on the chain, derailleur, and other parts of the gear-shifting system is thus significantly reduced, and it is possible to comfortably shift gears and subsequently re-engage the electrically assisted drive.

In an advantageous embodiment of the method according to the invention, the electrical signal is fed to the electronic control unit to operate the electric motor, this unit switches off the electric motor during gear shifting, or reduces its power. The suitable use of the electronic control unit is for operating a three-phase electric motor connected to a power supply, suitable software and hardware can also be used to control the switch-off of the electric motor or reduction of its power, respectively its torque during gear shifting. The electronic control unit is a device known to these skilled in the art and is resolved in the usual manner, and its integration is not the subject of the present invention.

In another advantageous embodiment according to the invention, the electronic control unit uses a programmable timer to switch off the electric motor or reduce its power at a previously configured time interval, during which gear shifting takes place.

The subject-matter of the present invention is also a device for shifting gears on a bicycle equipped with a power-assisted or main electric motor that drives the chainwheel, which includes at least one chain-driving sprocket, where the chainwheel is alternately or simultaneously powered via a bottom bracket axle fitted with crank arms and pedals, where the chainwheel is connected via a chain to the driven wheel with a sprocket that includes at least one chain-driven sprocket, while _..the device includes the front derailleur shifter using an inner cable to control the front derailleur of the chainwheel and/or a rear derailleur shifter which uses an inner cable to control the derailleur of a freewheel or an internal geared hub in the hub of the driven wheel.

The essence of the device according to the invention is that at least one derailleur shifter, or at least one inner cable, is equipped with a motion sensor to sense the movement of the derailleur shifter or cable when the gear is shifted, and the output of the electrical signal from the motion sensor is connected either directly or indirectly to the electric motor to reduce the value of the torque or to completely eliminate the effect of the electric motor on the chainwheel during gear shifting .

The device serves for carrying out the method according to the present invention, i.e. to enable gear shifting with the front or rear derailleur during reduced load on the chain and other parts of the gear shifting system.

In an advantageous embodiment of the device according to the invention, the electrical signal output of the motion sensor is connected to the electronic control unit which controls the electric motor; the unit is connected with the electric motor to switch it off or to reduce its power during gear shifting. The advantages of controlling the electric motor using the electronic control unit are described above.

In another advantageous embodiment of the device according to the invention, the electrical signal output of the motion sensor is modified to detect the motion of the derailleur shifter or inner cable connected in both directions to the electronic control unit, which is equipped with a programmable timer that can switch off or reduce the power of the electric motor to a previously configured time interval during gear shifting, and for increasing the torque value, or for reactivating the transfer of the torque from the electric motor to the chainwheel after gear shifting is completed. Lightened shifting can be executed during the configured time interval.

In a particular embodiment of the invention, it is advantageous when the motion sensor is formed by a cylindrical housing through which the inner cable passes and which is equipped with an internal optical sensor to detect the motion of the inner cable.

It is advantageous to place a reflective surface opposite the optical sensor inside the cylindrical housing to better reflect the optical signal and to increase the accuracy of the motion sensor.

Lastly, it is advantageous that the device according to the invention, includes a pedalling torque sensor, the output signal of which is connected to the electronic control unit. The control unit is programmed to evaluate the pedalling torque. If the pedalling torque shows a low value, the motor power is decreased, whereas a high torque value results in the disconnection of the electric drive.

The method and device for shifting gears on a bicycle according to the invention primarily enable manufacturers of power-assisted electric bicycles to use multi-row chainwheels, thus offering bicycles with a wider range of gears.

The method and device for shifting gears according to the invention also increase the reliability, life span, and operational safety of all shifting mechanisms used on power- assisted electric bicycles by fundamentally reducing the stress on the systems by disconnecting the drive during the gear shifting process. There is also a reduction in the risk of accidents caused by blocked chains or by other mechanical defects associated with the transfer of power.

Description of the drawings

The invention is described in detail by means of the drawings, where Fig. 1 depicts a side view of a power-assisted electric bicycle with central motor fitted with a three-row chainwheel and multi-row sprocket, where the motion sensor detects the movement of the inner cables leading from the derailleur shifters to the front and rear derailleurs. Fig. 2 depicts an overhead view with partial cross-section of the bicycle as per Fig. 1. Fig. 3 depicts a block schemata of the electrical connection of the bicycle drive as per Fig. 1. Fig. 4 depicts a schematic cross-section of a sample motion sensor of the bicycle. Fig. 5 depicts a side view of a power-assisted electric bicycle with central motor fitted with a single-row chainwheel and internal geared hub in the hub of the driven wheel, where the motion sensor detects the motion of the inner cable leading from the derailleur shifter to the internal geared hub. Fig. 6 shows an overhead view with partial cross- section of the bicycle as per Fig. 5. Fig. 7 depicts a block schemata of the electrical connection of the bicycle drive as per Fig. 5. Fig. 8 depicts a side view of a power-assisted electric bicycle with central motor fitted with a three-row chainwheel and multi-row sprocket, and with an added pedalling torque sensor. Fig. 9 depicts an overhead view with partial cross-section of the bicycle as per Fig. 8. Fig. 10 depicts a block schema of the electrical connection of bicycle drive as per Fig. 8.

Examples of the preferred embodiments of the invention

It should be understood that the following described and displayed specific examples of the realization of the invention are presented solely for illustrative purposes and not as a limitation of the examples of the embodiments of the invention for the cases indicated. Persons skilled in the art who are familiar with the state of the art shall find, or using routine experimentation will be able to determine, a larger or smaller number of equivalents to the specific realizations of the invention which are specifically described here. These equivalents shall also be included into the scope of the patent claims.

In the first example of the preferred embodiment depicted in Fig. 1 to Fig. 4, the power-assisted electric bicycle 1 is fitted with a three-row chainwheel 3 with chain-driving sprockets 4 and a multi-row sprocket 1_0 with driven sprockets 11. The handlebars of the bicycle 1 are fitted with a front derailleur shifter 12 which uses an inner cable 13 to control the front derailleur 14 of the chainwheel 3. The handlebars of the bicycle 1 are also fitted with a rear derailleur shifter 15 which uses an inner cable 16 to control the rear derailleur 17 of the sprocket 10 on the driven wheel 9. The front and rear derailleur shifters 12, 15 may be designed as lever shifters, twist grip shifters, or another technical feature. The inner cables 13, lj6 are housed in outer casings 2_1, which hold integrated motion sensors 22, 23. The motion sensor 23 in the embodiment depicted in Fig. 4 is formed by a cylindrical housing 2_4, which firmly holds the ends of an interrupted outer casing 21, and through which the inner cable 13 passes. The housing 24 is equipped with an internal optical sensor 25 which detects the movement of the inner cable 13, and which is also equipped with a sensor electrical outlet wire 26. Opposite the optical sensor 25 inside the motion sensor cylindrical housing 24 is a reflective surface 27. The motion sensor 2_2 in the embodiment depicted in Fig. 1 to Fig. 4 has the same technical feature as the motion sensor 23. In other embodiments not depicted here, the motion sensors 22, 23 may be technically executed using another embodiments known by experts, e.g. using a Hall effect sensor and magnets stored in the derailleur shifter formed by a grip shifter with the use of photocells, infrared or laser beams, or another similar design suitable for detecting the movement of the inner cables 13, 16 with electrical signal output. The signal of the optical sensor 25 runs to the electronic control unit 20 , which interrupts or limits the supply of electricity from the power supply 19 to the electric motor 2 at the moment that the inner cable 13 or 16 moves. In the next phase of motion of the derailleur shifter 12 or 15 using the inner cable 1_3 or 16 the position of the front derailleur 14 or sprocket ]L0 changes, thus shifting the gear. At the end of the motion of derailleur shifter 12 or 15, the motion sensor 22 or 23 is deactivated based on the signal provided by the optical sensor 25_, and the supply of electricity into the motor 2 is renewed. In the time interval between activation and deactivation of the motion sensor 2_2, 23_ the bicycle l_^ is driven solely by the power provided by the rider, or by drive power with a reduced degree of support from the electric motor 2. This embodiment is intended for all types of bicycles 1 with power-assisted electric drive, or with electrically-supplied main drive, primarily for sports bicycles. In the second example of the preferred embodiment depicted in Fig. 5 to Fig. 7, the power-assisted electric bicycle 1 with electric motor 2 acts on the chainwheel 3 which is fitted with a single-row chainwheel 3 and an internal gear hub 1_8 in the hub of the driven wheel 9. Gears are shifted with the rear derailleur shifter 15 located on the handlebars (shown in this example as a grip twist shifter) and using an inner cable 16 to control the internal geared hub 1 . The rear derailleur shifter 15 is fitted with a motion sensor 22 which consists of one of the technical features described in the first embodiment of the invention, e.g. with an optical sensor 25 as per Fig. 4. When the grip twist shifter is used, the optical sensor 25 activates the motion sensor 22 connected to. the electronic control unit 20 of the electric motor 2. Using the signal from the motion sensor 22, the control unit 20 interrupts or limits the thrust of the motor 2. The period of interruption is programmed to 1 second. After the programmed time period has expired, the thrust of the motor 2 is resumed. This embodiment is intended for all types of bicycles 1 with power-assisted electric drive or with electrically-supplied main drive, primarily city, travel, or folding bicycles.

In the third example of the preferred embodiment depicted in Fig. 8 to Fig. 10, the power-assisted electric bicycle 1 is equipped with a three-row chainwheel 3 and multi-row sprocket 10 like in the first example. The handlebars of the bicycle 1 hold the front derailleur shifter 12 which uses the inner cable 13 to control the front derailleur 14 of the chainwheel 3. The handlebars of the bicycle 1 also hold the rear derailleur shifter 15 which uses the inner cable 16 to control the rear derailleur 1_7 of the sprocket 1_0 on the driven wheel 9. The front and rear derailleurs 1_2, 15 may be designed as lever shifters, twist grip shifters, or another technical feature. The inner cables 13, 16 are housed inside outer casings 21 which are integrated with motion sensors 22, 23. The motion sensor 23 in the embodiment depicted in Fig. 4 is formed by a cylindrical housing 24, which firmly holds the ends of an interrupted outer casing 21, and through which the inner cable 13 passes.

The housing 2_4 is equipped with an internal optical sensor 25 which detects the movement of the inner cable 13, and which is also equipped with a sensor electrical outlet wire 26. Opposite the optical sensor 25_ inside the motion sensor cylindrical housing 24 is a reflective surface 27. The motion sensor 22 in the embodiment depicted in Fig. 4 has the same technical feature as the motion sensor 23. In other embodiments not depicted here, the motion sensors 22, 23 may be technically executed using another features as described in the first example of the embodiment.

The function of the device during gear shifting is the same as in the first embodiment of the invention. The bicycle 1 is also equipped with a pedalling torque sensor 28. The output signal of the pedalling torque sensor 28 is connected to the electric control unit 20. The control unit 20 is programmed to evaluate the pedalling torque. In the event of low pedalling torque, the power of the electric motor 2 is reduced, while an increase in power results in the interruption of the transfer of torque from the electric motor 2 to the chainwheel 3. The rider has the option of adjusting these values as personally needed, independently for the chainwheel 3 and sprocket 10. This embodiment is intended for all types of bicycles 1 with power-assisted electric drive, primarily for comfort models with a large number and range of gears. Industrial applicability

The method and device for shifting gears on a electric bicycle according to the invention can be used in the construction of bicycles with assisted electric drive for sports, mountain, and road bicycles as well as for city, travelling, and folding bicycles .

Overview of the positions used in the drawings

1 bicycle

2 electric motor

3 chainwheel

4 chain-driving sprocket

5 bottom bracket axle

6 crank arm

7 pedal

8 chain

9 driven wheel

10 sprocket

11 chain-driven sprocket

12 front derailleur shifter

13 inner cable

14 front derailleur

15 rear derailleur shifter

16 inner cable

17 rear derailleur

18 internal geared hub

19 power supply

20 electronic control unit

21 outer casing

22 motion sensor

23 motion sensor

24 motion sensor cylindrical housing

25 optical sensor

26 sensor's electrical outlet wire

27 reflective surface

28 pedalling torque sensor

Claims

1. The method of shifting gears in a bicycle (1) equipped with a power-assisted or main electric motor (2) which drives a chainwheel (3) that includes at least one chain-driving sprocket (4), where the chainwheel (3) is alternately or simultaneously driven by a bottom bracket axle (5) fitted with crank arms (6) and pedals (7), and where the chainwheel (3) utilizes a chain (8) to drive a driven wheel (9) with a sprocket (10) that includes at least one chain-driven sprocket (11), while the gears are changed using a front derailleur shifter (12) which uses an inner cable (13) to control a front derailleur (14) of the chainwheel (3) and/or uses a rear derailleur shifter (15) in conjunction with an inner cable (16) to control a rear derailleur (17) of the sprocket (10) or an internal geared hub (18) in the hub of the driven wheel (9), characterized in that upon a shifting of gears, the movement of the derailleur shifters (12,15) or of the inner cables (13,16) are converted into an electrical signal which is fed directly or indirectly into the electric motor (2), and as a result of this signal the torque value is reduced, or the effect of the electric motor (2) on the chainwheel (3) during gear change is eliminated entirely, and after gear changing is completed, the torque value subsequently increases, or the transfer of torque is reactivated from the electric motor (2) to the chainwheel (3) .

2. The method according to claim 1, characterized in that the electrical signal is fed to the electronic control unit (20) that controls the electric motor (2) and which switches off the electric motor (2) during gear shifting, or reduces its power. The method according to claim 2, characterized in that the electronic control unit (20) uses a programmable timer to switch off the electric motor (2) or to reduce its power at a previously configured time interval.

A device for changing the gears on a bicycle (1) that is equipped with a power-assisted or main electric motor (2) that drives a chainwheel

(3) which includes at least one chain-driving sprocket

(4), in which the chainwheel (3) is alternately or simultaneously powered by a bottom bracket axle (5) fitted with crank arms (6) and pedals (7), and where the chainwheel (3) is connected by a chain (8) with the driven wheel (9) with a sprocket (10) which includes at least one chain-driven sprocket (11), while the device includes a front derailleur shifter (12) using an inner cable (13) to control the front derailleur (14) of a chainwheel (3) and/or a rear derailleur shifter (15) uses an inner cable (16) to control the rear derailleur (17) of a sprocket (10) or internal gear hub (18) in the hub of the driven wheel (9), characterized in that at least one derailleur shifter (12,15) or at least one inner cable (13,16) is fitted with a motion sensor (22,23) to detect the motion of the derailleur shifter (12,15) or inner cable (13,16) during a gear change, and the outgoing electrical signal from the motion sensor (22,23) is connected directly or indirectly to the electric motor (2) to reduce the value of the torque or to completely eliminate the effect of the electric motor (2) on the chainwheel (3) during gear shifting .

5. A device according to claim 4, characterized in that the outgoing electric signal from the motion sensor (22,23) is connected to an electronic control unit (20) that controls the electric motor (2) and is connected to the electric motor (2) to switch it off or reduce its power during gear shifting .

6. A device according to claim 5, characterized in that the outgoing electrical signal from the motion sensor (22,23), modified to detect the movement of the derailleur shifter

(12,15) or inner cable (13,16), is connected in both directions to the electronic control unit (20) equipped with a programmable timer to switch off the electric motor (2) or to reduce its power to a previously configured time interval during gear shifting and to increase the torque value or to re-activate the transfer of torque from the electric motor

(2) to the chainwheel (3) after the expiration of the configured time interval.

7. A device according to claim 5 or 6, characterized in that the motion sensor (22,23) is made of a cylindrical housing (24) through which the inner cable (13,16) passes, and which is equipped with an internal optical sensor (25) to detect the movement of the inner cable (13, 16) .

8. A device according to claim 7, characterized in that a reflective surface (27) is located in opposite the optical sensor (25) inside the cylindrical housing (24).

9. A device according to at least one of claims 5 to 8, characterized in that it includes a pedalling torque sensor (28), the output signal of which is connected to the electronic control unit (20) .