GB2465648A

GB2465648A - Bicycle power generation unit

Info

Publication number: GB2465648A
Application number: GB0910836A
Authority: GB
Inventors: Alan Paul Davison; Andrew John Thomson
Original assignee: CYCLONE ELECTRONICS Ltd
Current assignee: CYCLONE ELECTRONICS Ltd
Priority date: 2009-06-23
Filing date: 2009-06-23
Publication date: 2010-06-02
Anticipated expiration: 2029-06-23
Also published as: GB2465648B; GB0910836D0

Abstract

A power generation unit for a bicycle includes a dive wheel 20 for attachment to a wheel 4 of the bicycle for rotation therewith, a driven wheel 16 and a drive element 18, such as a chain or belt, for transmitting drive from the drive wheel 20 to the driven wheel 16. An alternator 10 has a drive input (12, figure 3) and a clutch (14, figure 3) has an input connected to the driven wheel 16 and an output connected to the alternator drive input 12. The clutch 14 is constructed and arranged to transmit drive from the driven wheel 20 to the alternator 10 when the rotational speed of the driven wheel exceeds a predetermined value, and to disconnect the alternator 10 from the driven wheel 16 when the rotational speed of the driven wheel is less than the predetermined value.

Description

POWER GENERATION UNIT

The present invention relates to a power generation unit, and in particular but not exclusively to a power generation unit for a bicycle, and to a bicycle having a power generation unit.

It is well known to provide bicycles (bikes) with a dynamo that is driven by motion of the bike and generates a supply of electricity that may be used to light front and rear lamps.

Usually, the dynamo includes a drive wheel that is pressed against the rim or tyre of one of the bike wheels so that it rotates during motion of the bicycle and drives the dynamo. The dynamo then generates an electrical current that is usually sufficient to light one or two small lamps, providing that the dynamo is driven sufficiently quickly.

However, traditional dynamos are inefficient and the friction drive mechanism, using a drive wheel that is pressed against the wheel rim, is also mechanically inefficient. As a result, the power generated by a traditional dynamo is usually very small and only sufficient to light low power lamps that serve to warn other road users of the bike's presence. The power output is not usually sufficient to light a high power lamp similar to the headlamp of a motor bike that allows the rider to see distant objects. Furthermore, as the power output depends on the speed of the bike, the warning lights may dim or go out if the bike is travelling slowly or is stationary. This causes a hazard to the rider and to other *: :: 24) road users and pedestrians. * ***

There is also an increasing need for an on-bike power supply that can be used for driving other devices and accessories such a horns, satellite navigation devices, music players and so on. Traditional dynamos are unable to provide a sufficient power output for such uses.

r A more efficient lighting system is described in EP 0742136 A. This system includes an * : * 2 alternator that is driven from one of the bike wheels via a belt drive system. The alternating current (a.c.) output of the alternator is converted by a rectifier into a direct current (d.c.) supply and is used to charge an accumulator, which in turn provides power for one or more lamps. External recharging terminals are also provided for charging the accumulator from an external power supply.

The lighting system described in EP 0742136 A overcomes some of the problems associated with traditional dynamo-based systems. The alternator is electrically more S efficient than a dynamo and the belt drive system is mechanically more efficient than a friction drive. The alternator is therefore able to generate a greater output power for a given mechanical input power. Furthennore, because electrical energy is stored in an accumulator and released when required, the lamps will remain fully lit at all times, even if the bike is stationary. This leads to greater safety for the rider and other road users.

However, one disadvantage of the lighting system described in EP 0742136 A is that because the alternator has a large inertia and rotates at a much higher speed than the wheels, considerable effort is required from the rider when starting from a stationary condition. This may cause the rider to wobble or fall over, so giving rise to another safety hazard. Furthermore, the effort required to drive the alternator will add considerably to the exertion required by the rider when riding uphill.

It is an object of the present invention to provide a power generation unit for a bicycle that mitigates one or more of the aforesaid disadvantages.

According to one aspect of the present invention there is provided a power generation unit for a bicycle, the power generation unit including a drive wheel for attachment to a wheel of the bicycle for rotation therewith, a driven wheel, a drive element comprising a belt or chain for transmitting drive from the drive wheel to the driven wheel, an alternator having .. : a drive input, and a clutch having an input connected to the driven wheel and an output *... connected to the alternator drive input, said clutch being constructed and arranged to transmit drive from the driven wheel to the alternator when the rotational speed of the * driven wheel exceeds a predetermined value, and to disconnect the alternator from the driven wheel when the rotational speed of the driven wheel is less than the predetermined ** *.

: * * value. *. *

*.: By disconnecting the alternator at low speeds, the problems associated with starting from a stationary condition are avoided. The rider is able to accelerate rapidly up to a speed at which greater stability is assured, thus reducing the risk of wobbling. Furthermore, if the speed of the bike falls, for example when riding uphill, the clutch disconnects the alternator from the driven wheel, thereby reducing the exertion required by the rider. When the bike is travelling at a higher speed, for example when riding steadily along a level road or when coasting downhill, the clutch connects the alternator to the driven wheel to charge the battery.

The power generation unit also benefits from numerous other advantages as compared to traditional dynamo-based systems. The alternator is electrically efficient and the belt or chain drive system is mechanically more efficient than a friction drive: the system is therefore able to generate a greater output power for a given mechanical input power. This allows it to drive high power lamps and other auxiliaiy equipment, if required. Further, because electrical energy is stored in an accumulator and released when required, the lamps will remain fully lit at all times, even if the bike is stationary. This leads to greater safety for the rider and other road users.

Advantageously, the predetermined value at which the clutch transmits drive is approximately 0.5 revolutions per second. Alternatively or additionally, the predetermined value may be equivalent to a bicycle speed of approximately 2 metres per second. This ensures that drive to the alternator is not engaged until the bike has reached a speed at which it is reasonably stable.

Advantageously, the clutch is centrifugal clutch. This provides a simple and efficient mechanism for disengaging drive to the alternator at slow speeds. *5*S

Advantageously, the alternator is a multi-phase alternator, for example a three-phase S** * * ** . alternator, for high energy efficiency and a high power output.

* ** Advantageously, the power generation unit includes a gear drive for transmitting drive between the driven wheel and the alternator drive input. Preferably, the gear drive is located between the clutch and the alternator drive input. Use of a gear drive allows a high : *. gear ratio to be provided, so that the alternator rotates at a high speed for maximum * efficiency. Advantageously, the unit provides a gear ratio between the drive wheel and the alternator drive input of at least 20:1, preferably approximately 30:1.

Advantageously, the power generation unit includes a rectifier for rectifying an electrical output of the alternator. This converts the a.c. output of the alternator to a d.c. supply, which can be used for example for charging a battery or for driving devices that require a d.c. input Advantageously, the power generation unit includes a voltage regulator for regulating an electrical output of the alternator. This ensures that a substantially uniform d.c. output voltage is provided, regardless of the output power of the alternator or the electrical load.

Advantageously, the power generation unit includes a rechargeable battery connected to an electrical output of the alternator. The battery stores electrical energy and allows lights and other electrical loads to operate even when the bike is stationary.

Advantageously, the power generation unit includes a charger for charging the rechargeable battery from an external power supply. This allows the battery to be charged fully while it is not in use, so that it is ready to provide power whenever required.

Advantageously, the power generation unit includes a control unit for controlling the flow of electrical power from the alternator to the rechargeable battery, in order to prevent overcharging and to reduce the mechanical effort required to turn the alternator when the battery is fully charged and the required output power is low. Advantageously, the control unit is constructed and arranged to control the flow of electrical power from the alternator and/or the rechargeable battery to an electrical load. Preferably, the control unit includes a switch enabling a user to control the flow of electrical power from the alternator and/or the rechargeable battery to an electrical load. S... * . .

Advantageously, the alternator is constructed and arranged to provide in normal use a peak **..

output power in the range 20-50W. S. * S

* According to a further aspect of the invention there is provided a bicycle including a power generation unit according to any one of the preceding statements of invention, wherein the :. drive wheel is attached to a wheel of the bicycle for rotation therewith.

Advantageously, the alternator is mounted on a frame of the bicycle.

An embodiment of the invention will now be described by way of example with reference to the accompanying drawings, wherein: Figure 1 is a side view of a rear part of a bicycle; Figure 2 is a rear view of a rear bicycle wheel; Figure 3 is a rear view of an alternator and various drive components; Figure 4 is a view from above of the alternator and drive components shown in figure 3, and Figure 5 is a simple circuit diagram.

The bike shown in Fig. 1 includes a conventional frame 2 and a rear wheel 4 mounted between paired chain stays 6 and seat stays 8. The bike will also include various other conventional parts such as a seat, pedals, sprockets, drive chain, front wheel, front fork and handlebars, which are omitted from the drawings for clarity.

The bike is provided with a power generation unit including an alternator 10 that is mounted on one of the seat stays 8. The alternator 10 is preferably a multi-phase alternator, for example a three phase alternator. Preferably, the alternator 10 is constructed and arranged to provide in normal use a peak output power in the range 20-SOW. We have found that the system is readily able to supply in excess of 40W. This compares to the output of a traditional dynamo system, which is typically only 5-6W.

As shown in Figs. 3 and 4, the alternator 10 has an input shaft 12 that is connected via a centrifugal clutch 14 to a small drive wheel 16. The small drive wheel 16 is in turn * connected via an endless drive element 18 to a large drive wheel 20 that is connected to the rear wheel 4 for rotation therewith. The endless drive element 18 transmits drive from the large drive wheel 20to the small drive wheel 16 (the "driven wheel"), the rotational speed of the small driven wheel 16 being greater than that of the larger drive wheel 20 owing to : the difference in their sizes.

In this example, the two drive wheels 16,20 are sprockets and the endless drive element 18 is a drive chain. In an alternative form of the invention, the drive wheels 16,20 are pulley wheels and the drive element 18 is a belt. In either case, the drive element 18 serves to transmit drive from the large drive wheel 20 to the smaller driven wheel 16.

The large drive wheel 20 is attached to the axle of the rear wheel 4 and is located on the opposite side of the rear wheel to the main drive sprocket 22, which is driven from the pedals via the front sprocket and the chain. In the example shown in Figures 1 and 2, the large drive wheel 20 is shown on the right hand side of the rear wheel 4 and the main drive sprocket 22 is (unconventionally) located on the left: this arrangement may of course be reversed.

The centrifugal clutch 14 is constructed and arranged to transmit drive from the driven wheel 16 to the alternator 10 when the rotational speed of the driven wheel 16 exceeds a predetermined value, and to disconnect the alternator 10 from the driven wheel 16 when the rotational speed of the driven wheel is less than the predetermined value. The predetermined value may for example be approximately 0.5 revolutions per second, or a speed that is equivalent to a bicycle speed of approximately 2 metres per second (approximately 7kph). This ensures that drive to the alternator 10 is not engaged until the bike has reached a speed at which it is reasonably stable.

The alternator 10 is connected to an electrical circuit for example as shown in Fig. 5. The output of the alternator 10 is connected a rectifier 24, which converts the a.c. output of the alternator into a d.c. supply. Optionally, the rectifier 24 may also include a voltage regulator that controls the output voltage of the supply. The d.c. output of the rectifier/regulator 24 is connected to a controller 26, which controls the flow of electric * : * current to and from other parts of the circuit including a rechargeable battery (or accumulator) 28, lamps 30, other auxiliary equipment 32 and an optional external charger 36 for charging the battery 28 from an external power supply. S.

* 5 The controller 26 may include manual controls allowing the rider to select various operations, for example turning on and off the bicycle lamps 30. It may also include * automatic controls, for example for controlling the flow of electricity to and from the * battery 28 according to the state of charge of the battery, the power output of the alternator and the power requirements of the lamps 30 and/or auxiliary equipment 32. The controller 26 may also control the flow of electricity from the optional external charger 36 to the battery 28 during recharging, to ensure that the battery is not overcharged.

In use, the alternator 10 is driven from the rear wheel 4 during motion of the bicycle, providing that the bike is travelling above a predetermined speed (for example, about 7kph). When the bike is travelling at a slower speed or is stationary the centrifugal clutch 14 disengages the alternator 10 from the driven wheel 16 so that it does not rotate. This allows the rider to accelerate quickly to a stable speed without any additional drag. It also allows the rider to direct all his or her efforts into propelling the bike when cycling at slow speed, for example up a steep hill.

The alternating current generated by the alternator 10 is converted into a direct current by the rectifier 24 and supplied via the controller 26 to the battery 28 and/or the load (the lamps 30 andlor auxiliary equipment 32). The controller 26 is preferably constructed and arranged to control the flow of electricity to and from the battery 28 according to the state of charge of the battery, the amount of power available from the alternator 10 and the power requirement of the load 3 0,32. For example, if the battery 28 is only partially charged and the power generated by the alternator 10 exceeds the requirements of the load, the excess current may be used to recharge the battery. On the other hand, if the power requirement of the load is greater than the power supplied by the alternator 10, energy may be drawn from the battery 28 to supplement the output of the alternator 10. The system is thus able to ensure that essential electrical equipment such as the lamps 30 continue to operate even when the bike is travelling slowly or is stationary.

When the bike is not being used, the battery 28 may be recharged from amains electricity :: supply using the external charger 36. * ***

Various modifications of the power generating unit are of course possible. For example, * 25 the alternator 10 may include a gear drive for transmitting drive between the driven wheel 16 and the alternator drive input and increasing the gear ratio of the input, so that the * alternator rotates at a high speed. The gear drive may be located for example between the *: * clutch 14 and the alternator drive input shaft 12. Advantageously, the drive train provides a gear ratio between the drive wheel 20 and the alternator drive shaft 12 of at least 20:1, preferably approximately 30:1.

Although the alternator 10 is shown as being driven from the rear wheel 4, it may alternatively be driven from the front wheel or directly from the main drive train (that is, from the main drive sprocket or from an additional sprocket that engages the main drive chain. However, driving the alternator 10 from the rear wheel 4 is generally preferred as in this way the alternator can be driven either by the exertions of the rider or by the recovery of energy when free-wheeling or coasting downhill, or when slowing down.

The controller 26 may optionally be omitted or replaced with manual switches if preferred.

The auxiliary equipment 32 may include for example direction indicators, an audible warning horn, a music player, a satellite navigation system or a power outlet socket for supplying electricity to other electrical devices.

The alternator 10 may also include a manual input socket (not shown) that accepts a winding device, for example a crank, allowing the battery 28 to be recharged manually even when the bike is stationary.

The power generation unit may also be used with other vehicles apart from bicycles. a... * . . a. I * .*. * . * . * .*. I. ** * . S * * *S S **

Claims

CLAIMSI. A power generation unit for a bicycle, including: (a) a drive wheel for attachment to a wheel of the bicycle for rotation therewith; (b) a driven wheel; (c) a drive element comprising a belt or chain for transmitting drive from the drive wheel to the driven wheel; (d) an alternator having a drive input, and (e) a clutch having an input connected to the driven wheel and an output connected to the alternator drive input, said clutch being constructed and arranged to transmit drive from the driven wheel to the alternator when the rotational speed of the driven wheel exceeds a predetermined value, and to disconnect the alternator from the driven wheel when the rotational speed of the driven wheel is less than the predetermined value.
2. A power generation unit according to claim 1, wherein the predetermined value is approximately 0.5 revolutions per second.
3. A power generation unit according to claim 1 or claim 2, wherein the predetermined value is equivalent to a bicycle speed of approximately 2 metres per second.
4. A power generation unit according to any one of the preceding claims, wherein the * : : :: clutch is centrifugal clutch.

*
5. A power generation unit according to any one of the preceding claims, wherein the alternator is a multi-phase alternator.
6. A power generation unit according to any one of the preceding claims, including a * gear drive for transmitting drive between the driven wheel and the alternator drive *:*. input.
7. A power generation unit according to claim 6, wherein the gear drive is located between the clutch and the alternator drive input.
8. A power generation unit according to any one of the preceding claims, having a gear ratio between the drive wheel and the alternator drive input of at least 20:1, preferably approximately 30:1.
9. A power generation unit according to any one of the preceding claims, including a rectifier for rectifying an electrical output of the alternator.
10. A power generation unit according to any one of the preceding claims, including a voltage regulator for regulating an electrical output of the alternator.
11. A power generation unit according to any one of the preceding claims, including a rechargeable battery connected to an electrical output of the alternator.
12. A power generation unit according to claim 11, including a charger for charging the rechargeable battery from an external power supply.
13. A power generation unit according to claim 11 or claim 12, including a control unit for controlling the flow of electrical power from the alternator to the rechargeable battery.
14. A power generation unit according to claim 13, wherein the control unit is constructed and arranged to control the flow of electrical power from the alternator and/or the rechargeable battery to an electrical load.
15. A power generation unit according to claim 14, wherein the control unit includes a switch enabling a user to control the flow of electrical power from the alternator * : and/or the rechargeable battery to an electrical load.

*
16. A power generation unit according to any one of the preceding claims, wherein the * alternator is constructed and arranged to provide in normal use a peak output power in the range 20-SOW.

* :*
17. A power generation unit substantially as described herein, with reference to and as illustrated by the accompanying drawings.
18. A bicycle including a power generation unit according to any one of the preceding claims, wherein the drive wheel is attached to a wheel of the bicycle for rotation therewith.
19. A bicycle according to claim 18, wherein the alternator is mounted on a frame of the bicycle.
20. A bicycle substantially as described herein, with reference to and as illustrated by the accompanying drawings. * * * ** * **** * S **S. ** * S * S.. *. .5 * . S * S S. SS S S **Amendments to the claims have been filed as follows:-CLAIMS1. A power generation unit for a bicycle, including: (a) a drive wheel for attachment to a wheel of the bicycle for rotation therewith; (b) a driven wheel; (c) a drive element comprising a belt or chain for transmitting drive from the drive wheel to the driven wheel; (d) an alternator having a drive input, and (e) a clutch having an input connected to the driven wheel and an output connected to the alternator drive input, said clutch being constructed and arranged to transmit drive from the driven wheel to the alternator when the rotational speed of the driven wheel exceeds a predetermined value, and to disconnect the alternator from the driven wheel when the rotational speed of the driven wheel is less than the predetermined value.2. A power generation unit according to claim 1, wherein the predetermined value is approximately 0.5 revolutions per second.3. A power generation unit according to claim 1 or claim 2, wherein the predetermined value is equivalent to a bicycle speed of approximately 2 metres per second.4. A power generation unit according to any one of the preceding claims, wherein the * : : :: clutch is centrifugal clutch.* 5. A power generation unit according to any one of the preceding claims, wherein the alternator is a multi-phase alternator.6. A power generation unit according to any one of the preceding claims, including a * gear drive for transmitting drive between the driven wheel and the alternator drive *:*. input.7. A power generation unit according to claim 6, wherein the gear drive is located between the clutch and the alternator drive input.8. A power generation unit according to any one of the preceding claims, having a gear ratio between the drive wheel and the alternator drive input of at least 20:1.9. A power generation unit according to claim 8, having a gear ratio between the drive wheel and the alternator drive input of approximately 30:1.10. A power generation unit according to any one of the preceding claims, including a rectifier for rectifying an electrical output of the alternator.11. A power generation unit according to any one of the preceding claims, including a voltage regulator for regulating an electrical output of the alternator.12. A power generation unit according to any one of the preceding claims, including a rechargeable battery connected to an electrical output of the alternator.13. A power generation unit according to claim 12, including a charger for charging the rechargeable battery from an external power supply.14. A power generation unit according to claim 12 or claim 13, including a control unit for controlling the flow of electrical power from the alternator to the rechargeable battery.15. A power generation unit according to claim 14, wherein the control unit is constructed and arranged to control the flow of electrical power from the alternator S...and/or the rechargeable battery to an electrical load.* .. *5.S16. A power generation unit according to claim 15, wherein the control unit includes a p... . switch enabling a user to control the flow of electrical power from the alternator * and/or the rechargeable battery to an electrical load. * S. ..j.*: 17. A power generation unit according to any one of the preceding claims, wherein the alternator is constructed and arranged to provide in normal use a peak output power in the range 20-50W.18. A power generation unit substantially as described herein, with reference to and as illustrated by the accompanying drawings.19. A bicycle including a power generation unit according to any one of the preceding claims, wherein the drive wheel is attached to a wheel of the bicycle for rotation therewith.20. A bicycle according to claim 18, wherein the alternator is mounted on a frame of the bicycle.
21. A bicycle substantially as described herein, with reference to and as illustrated by the accompanying drawings. * p ********* * I **. * * I.. * * ** 1 * *Is* S. * * S. I S.