GB2336575A

GB2336575A - Auxiliary electrical drive for a bicycle

Info

Publication number: GB2336575A
Application number: GB9808605A
Authority: GB
Inventors: Chen Hui Lai
Original assignee: Individual
Current assignee: Individual
Priority date: 1998-04-22
Filing date: 1998-04-22
Publication date: 1999-10-27
Anticipated expiration: 2018-04-22
Also published as: GB2336575B; GB9808605D0; NL1009093C2; JPH11321771A

Abstract

An auxiliary electric drive in a bicycle includes a planetary gear set with a planet carrier 10 coupled to pedals 2B, planet gears 20, a ring gear 40 connected to the driving chain wheel 200 and a sun gear 30 which is drivable by an electric motor 500 through bevel gears 530, 400 and a one-way clutch 410. The sun gear 30 and bevel gear 400 are rotatably mounted on pedal axle A. The motor 500 is controlled by a controller which receives inputs from sensors which detect the speed of the pedal shaft A and the bicycle rear wheel. The chain drive to the rear wheel may include multiple sprockets and a derailleur mechanism or a hub gear.

Description

2336575 AUXILIARY DRIVING DEVICE OF ELECTRICALLY ASSISTANT VEHICLE The

present invention is related to an auxiliary driving device adapted to be incorporated in an electrically assistant vehicle, such as electric bicycle and electric tricycle, and having a closed loop feedback control system for controlling driving power/torque.

With the advent of environment protection era, bicycles have been widely used as a short distance transportation measure as weH as a sport device. To reduce the load of the bicycle rider in traveling with the bicycle, some of the newly developed bicycles are equipped with an electrically powered auxiliary driving device which usually comprises an electrical motor and the associated transmission system to help the rider in for example climbing a hill. Since the motor is usually powered by a rechargeable battery system, the power that is available for the motor is limited. Conversation of the battery power is important so that it is desired to have the motor operated in the most efficient, as well as well controllable way in order to conserve the power and reduce potential risk of accidents caused by an un-controlled motor operation.

In the conventional electric bicycle structure, a simple way to control the auxiliary driving power source is to mount the auxiliary driving power source to either the front wheel or the rear wheel of the bicycle and an electric switch that is used as a controller to turn on the electrical auxiliary power source is mounted on the handle bar to be readily accessible by the rider in order to turn on the auxiliary driving power source. The power 1 output of auxiliary driving power source the motor is directly applied to the wheel of the bicycle and is not well controlled and regulated which usually results in a water of the electrical power.

Furthermore, in the related prior document references, such as US patent No. 5,704,441, a torque sensor is disclosed to be mounted on the bicycle pedal to detect the riding force applied to the pedal in order to control the auxiliary power that is supplied by the motor of the auxiliary driving device. This, although providing an improvement to the problem that the auxiliary driving power of the conventional electric bicycle is supplied to the bicycle without being properly controlled, yet has a problem in that it provides a control to the auxiliary driving power system in response to the torque on the pedal. Since the torque on the pedal is to quite some extent dependent upon how the rider depresses the pedal and vanes very violently, the operation of the motor controlled in accordance with such a violently varied torque is quite unstable and may sometimes cause vibration. This, obviously, results in a waste of power.

Furthermore, the above mentioned US patent No. 5,704,441 is not only poor in controlling the motor to provide a stable mechanical power output, but also not suitable to be incorporated in bicycles that have a multiple stage derailleur system for it is incapable to provide proper rotational speed. and torque of the auxiliary driving power in accordance with the different speed setting of the multiple stage derailleur system and thus its practical use is limited.

Thus, it is desirable to have an auxiliary driving device which controls the operation of the motor to supply mechanical torque to the bicycle wheel in a smooth, well-controlled and regulated manner in order to overcome the problems encountered in the prior art-

2 Therefore,- an object of the present invention is to provide an auxiliary driving device of an electrically assistant vehicle, such as an electrical bicycle, which auxiliary driving device supplies a suitable torque to the vehicle in accordance with the driving speed of the pedals of the bicycle and the rotational speed of the rear wheel of the bicycle so as to make the auxiliary power supplied to the bicycle in a more smodth manner to facilitate the operation of the bicycle and thus reducing the load of the bicycle rider.

Another object of the present invention is to provide an auxiliary driving device of an electrically assistant vehicle, such as an electrical bicycle which determines the amount of power to be supplied to the bicycle in accordance with the driving speed of the bicycle pedals and the rotational speed of bicycle rear wheel so that it is compatible with bicycles having a multiple stage derailleur system and is capable to supply a suitable torque and rotational speed of auxiliary power to the bicycle Mi accordance with the speed setting of the derailleur system and thus broadening the application of the auxiliary driving device.

A further object of the present invention is to provide an auxiliary driving device of an electrically assistant vehicle, such as an electrical bicycle, whereifi the bicycle comprises a pedal driving system and an auxiliary driving device which are operable independently, the auxiliary driving device being only capable to supply power in a one way fashion so that when the bicycle is manually moved backward, no reversed rotation of the auxiliary driving device may be induced and the avoid a reversed current resulted therefrom which may damage the control circuit.

3 1 To achieve the above objects, Mi accordance with the present invention, there is provided an auxiliary driving device of an electrically assistant vehicle, such as an electrical bicycle. The auxiliary driving device comprises a planetary gear set which comprises a planetary gear support member rotatably supporting thereon a number of planetary gears and coupled to pedals of the bicycle. A sun gear is drivingly coupled to a motor in a one-way transmission manner to be driven by ie motor in a one-way fashion. A ring gear is co-axially fixed to a front driving chain wheel of the bicycle. The front driving chain wheel indirectly drives a derailleur system of the bicycle via a chain to cause the derailleur to drive a rear wheel of the bicycle. Two sensors are respectively mounted to the planetary gear support member and the bicycle rear wheel to detect the rotational speeds of the manually driven pedals and the rear wheel. Signals representing the rotational speeds are processed and transmitted to a controller which, in response thereto, generates an auxiliary power control signal which is then amplified by a power amplifier to drive the motor so as to control the motor to generate a suitable auxiliary power output to drive the bicycle rear wheel in response to the rotational speeds of the pedals and the bicycle rear wheel and thus forming a driving control system that has a rotational speed feedback for controlling/regulating the torque and speed output of the auxiliary driving system.

The above objects, as well as features and advantages, of the present invention will become apparent by reading the following detailed description of a preferred embodiment thereof with reference to the attached drawings wherein:

4 Figure 1 is an exploded perspective view of an auxiliary driving device adapted in an electrically assistant bicycle in accordance with the present invention, as well as a portion of frame of the bicycle; Figure 2 is a cross-sectional view of the auxiliary driving device of the present invention as well as a portion of the bicycle frame; Figure 3 is a schematic view showing the flow of torque in the bicycle incorporating the auxiliary driving device of the present invention; Figure 4 is a circuit diagram of a control circuit controlling the operation of the auxiliary driving device of the present invention; Figure 5(a) is a schematic view showing the operating relationship between the planetary gear and the ring gear of the planetary gear set adapted in the auxiliary driving device of the present invention; Figure 5(b) is a schematic view showing the operating relationship between the planetary gears, the sun gear and the planetary gear support member of the planetary gear set adapted in the auxiliary driving device of the present invention; Figure 6 is a top view of a portion of an electrically assistant bicycle incorporating the auxiliary driving device of the present invention; and Figure 7 is a top view of a portion of another electrically assistant bicycle incorporating the auxiliary driving device of the present invention.

With reference to the drawings and in particular to Figures 1 and 2, wherein an auxiliary driving device in accordance with the present 25 invention is shown mounted to an electrically assistant vehicle which in the 1 embodiment illustrated comprises an electrical bicycle, but is not limited thereto. the auxiliary driving device of the present invention comprises a planetary gear set 100 which comprises a planetary gear support member 10 having a central bore 11 fit over a pedal axle A of the bicycle that has pedals 2B mounted thereon and each secured thereto by means of a key I A which is received within a key slot of the pedal axle A and fit into a key slot 111 formed inside the central bore 11 of the planetary gear support member 10. The pedal axle A extends through and is rotatably supported by a five-branch tube I B of a frame B of the bicycle so that the planetary gear support member 10 is manually rotatable about a central axis of the five-branch tube lB or a central axis of the pedal axle A by means of the depression of the pedals 2B performed by a bicycle rider (not shown).

The planetary gear support member 10 has a plurality of pivot pins 12 fixed thereon and preferably equally spaced from each other and concentrically arranged about the central axis. Each of the pivot pins 12 receives and rotatably supports a planetary gear 20 so that the planetary gears 20 are driven to orbit about the central axis with the rotation of the planetary gear support member 10. In the embodiment illustrated, there are three planetary gears 20 rotatably supported on the planetary gear support member 10. However, there may be different number of the planetary gears.

A sun gear 3 0 is rotatable about the central axis of the pedal axle A and is disposed between the planetary gears 20 to engage with the planetary gears 20.

A ring gear 40 is disposed around the sun gear 30 and the planetary gears 20 to be engaged with the planetary gears 20. The ring gear 40 compnses a plurality of through holes 41 which receive bolts or other fasteners 2A. The bolts 2A are threaded on inner-threaded holes 2 10 that 6 are provided on a front driving chain wheel 200 that is co-axially rotatable about the central axis of the pedal axle A so as to secure the ring gear 40 to the front driving chain wheel 200.

The front drivng chain wheel 200 that is rotatable about the pedal axle A is drivingly coupled to a chain 300 (see Figure 6 and 7) to drive a rear wheel C of the bicycle.

A first, driving bevel gear 400 is rotatably fit over th6 pedal axle A and is connected to a co-axially arranged collar 420 by means of a one- way clutch or ratchet device 410 connected therebetween. The collar 420 has a key slot 421 thereon which corresponds to the key slot 311 of the sun gear 30 so as to receive therein a key 430 to couple the sun gear 30 to the collar 420 and thus forming a one-way driving coupling between the first bevel gear 400 and the sun gear 30.

The collar 420 and thus the first bevel gear 400 are rotatably supported on the pedal axle A by means of an inner bearing D' interposed between the collar 420 and the pedal axle A. An external bearing D is fit over the collar 420 to co-axially and rotatably support thereon the front driving chain wheel 200. Thus the rotation of the first bevel gear 400 is transmitted in a one-way fashion to the front driving chain wheel 200 by means of the sun gear 40 keyed to the collar 420 that is connected to the first bevel gear 400 by the one way clutch 410 and the engagement among the sun gear 40, the planetary gears 20 and the ring gear 40 which is secured to the front driving chain wheel 200 with the bolts 2A.

An electric motor 500, serving as an auxiliary driving power source of the auxfliary driving device, is fixed to the bicycle frame B by means of attaching a support plate 5 10 of the motor 500 to a plurality of lugs 413 that are fixed to for example the down tube 3B of the bicycle frame B. The electric motor 500 is preferably provided with a built-in reduction gear set 7 1 (not shown) having an output spindle 520 to which a second, output bevel gear 530 is fixed. The second bevel gear 530 engages the first bevel gear 400, preferably in a mutually perpendicular or right-angled manner, so as to transmit rotation andlor torque from the motor 500 to the first bevel gear 400 and thus the front driving chain wheel 200 (as discussed above). The one-way clutch 410 allows the bevel gears 400 and 530 to be kept stationary with the motor 500 when the motor 500 is not operating, while allows the front driving chain wheel 200 to freely rotate without being subject to any constraint from the bevel gears 400 and 530 and the motor 500. Thus, in case that the motor 500 is turned off, the bicycle is still manually operable.

in manually operating the bicycle, the rider depresses the pedals 213 to rotate the pedal axle A about its central axis which in turn drives the planetary gears 20 by means of the key coupling between the planetary gear support member 10 and the pedal axle A and the rotatable support of the planetary gears 20 on the pivot pins 12 of the planetary gear support member 10. The rotation of the planetary gears 20 causes the ring gear to drive the front driving chain wheel 200. It should be noted that although the engagement between the planetary gears 20 and the sun gear 30 also makes the sun gear 30 rotated, the rotation of the sun gear 30 is not allowed to be transmitted to the bevel gears 400 and 530 due to the one way clutch 410.

Figure 3 schematically shows the routes of torque flow from both the motor 500 and the pedals 2B to for example a rear wheel C of the bicycle.

The first route that is from the pedals 2B to the rear wheel C comprises manually applying torque to the pedals 213 which is then transmitted through the planetary gear support member 10 to the ring gear 40 from which the torque is transmitted to the rear wheel C via a rear derailleur 8 system E, if any. The second route is from the motor 500 to the sun gear 30 which is then drives the ring gear 40 from which the torque is transmitted to the rear wheel C via the derailleur system E. It should be noted that the derailleur system E is optional.

Due to the one-way clutch 410, the two torque flows may be applied to the ring gear 40 at the same time. In other words, the rear wheel C may be driven both manually via the pedals 2B and by the motor 500. It should be noted that due to the one-way clutch 410, the bicycle may only be driven by the motor 500 in the forward moving direction.

Figure 3 also show the route of a control signal for controlling the motor which forms a closed loop feedback system. The closed loop feedback system comprises a sensor 600 which may comprise any device that is capable to detect rotational speed, including, but not limited to, motor, photo-electric switch, reed switch, proximity switch, and Hall IC.

The sensor 600 is mounted to the planetary gear support member 10 to detect the rotational speed of the planetary gear support member 10 which is the rotational speed of the pedal axle A (that is the speed that the rider drives the pedals 2B). A signal generated by the sensor 600 that represents the rotational speed of the pedal axle A is then amplified by an amplification circuit having a gain constant K. In other words, the signal is amplified by.a factor of K. In the embodiment illustrated, the gain factor K is a constant and the calculation thereof will be described later.

The amplification circuit generates an output signal Er which is applied to an operation or comparison circuit 700, serving as an input of the closed loop feedback system.

The closed loop feedback system further comprises a second sensor 600' which may be identical to or similar with the first sensor 600 and is mounted to the rear wheel C to detect the rotational speed of the rear wheel 9 C to generate a feedback signal Eh which is applied to the comparison circuit 700 to be compared with the input signal Er.

The comparison circuit 700 generates an output signal Ec based on the difference or error between the input signal Er from the sensor 600 and the feedback signal Eh from the sensor 60C. The error signal Ec is then applied to a controller 800 which generates a control signal Es in response to the error signal Ec and the control signal Es is transmitted through and amplified by a power amplification 900 to drive the motor 500. The motor 500 then drives, via the sun gear 30 and the ring gear 40, as well as the derailleur system E, if any, the rear wheel C and the rotation of the rear wheel C causes the feedback signal Eh. This closed loop feedback system provides a precise control over the auxiliary driving device of the present invention.

Referring to Figure 4, which shows a circuit diagram of a control circuit adapted in the auxiliary driving device of the present invention, the control circuit comprises a plurality of voltage regulation circuits S 1, S2 and S3 which are comprised of voltage regulation integrated circuit U 1, U2 and U3 respectively to provide three different working voltages W, V1 and W The comparison circuit 700 shown in Figure 3 consists of three operational amplifiers U4, U5 and U6. The operational amplifiers U4 and U5 both form an integration circuit and respectively receive the input signal Er and the feedback signal Eh. The operational amplifier U6 forms a signal addition circuit which receives the integrated signals of the input signal Er and the feedback signal Eh and generates the error signal Ec.

Me controller 800 shown in Figure 3 comprises a power control integrated circuit U7 having an input pin IP to receive the error signal Ec, control signal to the power amplifier 900 in response to the error signal Ec.

The power amplifier 900 shown in Figure 3 comprises transistors Q 1, Q2 and Q3 which are controlled by the power control signal from the controller 800 to control the power output (namely, the output torque and rotational speed) of the motor 500 in order to adjust the power output of the motor 500 in accordance with the rotational speed of the rear wheel C and the driving speed of the pedals 2B.

Preferably, a free wheel diode D I is connected in parallel to the motor 500 to provide a by-pass current path for reversed current caused by discharge of inductive load when the motor 500 is turned off in order to avoid damage to the other components of the circuit.

The circuit shown in Figure 4 is only a practical embodiment which should not be considered limitative to the scope of the present invention.

The design idea of the present invention will now be described with reference to Figures 5(a) and 5(b). Referring to Figure 5(a) first which schematically shows the planetary gear support member 10, the planetary gears 20 and the sun gear 30 of the planetary gear system to illustrate the relationship between the torque and the rotational speed thereof. In the 20 following discussion, the following notations are adapted: Wa: rotational speed of the planetary gear support member 10; Wp: rotational speed of the planetary gears 20; Ws: rotational speed of the sun gear 30; Wr: rotational speed of the ring gear 40; Wb: rotational speed of the bicycle rear wheel C; Ta: torque of the planetary gear support member 10; Tp: torque of the planetary gears 20; Ts: torque of the sun gear 30; Tr: torque of the ring gear; Rs: radius of the sun gear 30; Rp: radius of the planetary gears 20; fap: the force applied by the planetary gear support member 10 to the 5 planetary gears 20; ' > fpa: the force applied by the planetary gears 20 to the planetary gear support member 10; fsp: the force applied by the sun gear 30 to the planetary gears 20; fps: the force applied by the planetary gears 20 to the sun gear 30; frp: the force applied by the ring gear 40 to the planetary gears 20; fps: the force applied by the planetary gears 20 to the ring gear 40; Ns: the tooth number of the sun gear 30; Nr: the tooth number of the ring gear 40; Nf. the tooth number of the front driving chain wheel 200; and Nb: the tooth number of the selected chain wheel of the derailleur system E. For the planetary gear system, the following equation (1) applies: Ws - Wa Nr Wr Wa Ns (1) It is understood from equation (1) that for given tooth numbers (Nr, Ns) of the sun gear 30 and the ring gear 40, the speed (Wr) of the ring gear is dependent upon the speed of the planetary gear support member 10 (Wa) which is the rotational speed of the pedal axle A or pedals 213 and the speed of the sun gear 30 (Ws) which is the rotational speed induced by the motor 500. Furthermore, Ts = Rs x SP Ta = (Rs + Rp) x fap TP = (Rs x fps) + [(Rs + Rp) x fpal From the above three equations, it obtains that 12 Ts+Ta+Tpl= 0 for fsp = -fps and fap = -fpa.

(2) Figure 5(b) reveals the relationship in rotational speed and torque between the sun gear 20 and the ring gear 40, wherein:

Tr = (2Rp + Rs) x frp Tp2 = (2Rp + Rs) x fpr and thus Tr + Tp2 = 0 for frp = -fpr.

Adding equations (2) and (3) together gives Ts + Ta+ Tr + Tpl + Tp2 = 0 (3) (4) Further, Tpl + Tp2 = Tp = 0, for the planetary gears 20 act as idle gears that do not work but transmit rotation so that they have only rotational speed, but no torque.

Putting the above equation in equation (4) gives the following result:

Ts + Ta + Tr = 0 (5) In addition, in accordance with the energy conservation principle, if the mechanical loss inside the planetary gear system is neglected, the input power and the output power of the planetary gear system are identical, 20 namely (TsWs + TaWa) + TrWr = 0 'Me sign convention for input and output is opposite to each other.

Multiplying equation (5) with the rotational speed of the planetary gear support member 10 results in the following equation (7):

TsWa + TaWa + TrWa = 0 (7) (6) Subtracting equation (7) from equation (6) gives Ts(Ws. - Wa) + Tr(Wr - Wa) = 0 which, after being properly manipulated, results in: Ts Wr-Wa Tr Ws - Wa From equations (1) and (8), it obtains that Ts Ns Tr Nr (8) which reveals that the proportion of the tooth numbers between the sun gear and the ring gear is equal to that between the torques of the sun gear and the ring gear and the following relationship is obtained Ts:T&Tr = Ns:-(Ns + Nr): Nr (9) which shows that for given tooth numbers of the sun gear and the ring gear, the ratio between the sun gear and the ring gear is a constant. Thus, a constant ratio is given between the torque that is manually applied to the pedals 2B by the rider's feet and the motor torque from the motor 500.

Based on the above relationships between the torques, the tooth numbers and the rotational speeds, the closed loop feedback control system shown in Figure 3 and the control circuit shown in Figure 4, as well as the controller 800, may thus be designed to realize the above relationships and the rotational speed of the rear wheel C may be expressed as follows:

Wb=KxWa, where K is a constant.

(10) In case that a rear derailleur system E is included, then Wb = Nf Wr Nb and putting the equation into equation (10) gives:

Wr=KxWax Nb Nf Putting equation (11) into equation (1) gives 14 (11) Ws=[l- Nr x (K x Nb - I)] x Wa Ns Nf Assume that As = [1 - Nr x (K x Nb _ 1)] which is also a constant for K is Ns Nf constant and Nr,, Nb and Nf are un-variable values, then Ws = As x Wa (12) Equation (12) reveals that the output rotational speed (Ws) of the motor 500 is proportional to the rotational speed (Wa) of thepedals 213 that is provided by the rider's movement of depressing the pedals and the proportional constant therebetween may be determined by the ratio between the tooth number of the front driving chain wheel 200 and the tooth number of the selected chain wheel in the rear derailleur system E, namely Nb/W In other words, by operating the derailleur system E to switch between different chain wheels of the derailleur system (namely different speed settingO, one may change the ratio. The larger the ratio Nb/Nf is, the larger the value of As is and the greater the rotational speed (Ws) of the sun gear 30 is. Correspondingly, the output rotational speed of the motor 500 is higher.

The value of K may be obtained from manipulation of equation (12) and may be determined on the basis of the desired rotational speed Wb of the rear wheel C, namely the speed of the bicycle. For example:

(1) in the case that the speed of the bicycle is below 15 Kniffi (kilometers per hour) with the auxiliary power being given as 1: 1 constant ratio, then the value of K is:

K 1 [(1 Ta Ns Ts Nr (I1) in the case that the speed of the bicycle is between 15-24 Km/h with the auxiliary power being given as a linear declination having a negative slope, then the value of K is:

K= 1+10- 1-(Wb-15)/9 x Ta) x Ns Ts Nr Thus the value of K may be readily obtained by substituting the ratio between the tooth numbers (Ns, Nr) of the sun gear 30 and the ring gear 40 in the above equation. For example, for the case that Ns=8 and Nr-21, from equation (9), Ts:Ta=8:(-29) which is substituted in the equations of cases (I) and (H), giving:

(a) when Wb is within the range between 0- 15 KnA K=58/21=2.761i5 (b) when Wb is within the range between 15-24 Km/h, such as Ws=18 Km/h, then K=145163=2.301; and (c) when Wb is greater than 24 Km/h, then K=0 and Ws=O, namely, no auxiliary power and rotational speed is provided by the motor 500.

Based on the above calculation, one can stably and automatically adjust the supply of the auxiliary power from the motor 500. In other words, the motor 500 may automatically regulates the auxiliary power that is supplied to the bicycle in response to the difference between the speed provided by the manual actuation of the bicycle pedals 2B and the rotational speed (Wb) of the rear wheel C of the bicycle so that the operation efficiency of the motor 500 may be enhanced and the consumption of lhe electrical power used to operate the motor 500 may be more efficient.

Refer-ring to Figures 6 and 7, which show the applications of the present invention in bicycles with different rear derailleur systems, the bicycle shown in Figure 6 that embodies the present invention comprises a rear derailleur E which is a regular multiple stage chain wheel type derailleur system. The chain wheels of the derailleur system is coupled to the front driving chain wheel 200 by means of the chain 300. As 16 discussed above, the motor 500 may provide different output based on the ratio between the tooth number of the selected one of the chain wheels of the derailleur E and the tooth number of the front driving chain wheel 200. It is apparent to those skilled in the art to design the output torque from the motor 500 by following the same principle discussed above in accordance with a particular fashion of the bicycle rider in switching between different chain wheels of the derailleur so as to allow the operation of the motor to better match the riding fashion of the rider. The feature of such a design of the operation of the motor is that it is linear so that the operation of the bicycle by both the rider and the motor is more smooth.

Figure 7 shows another derailleur system E' which allows switching between a multiplicity of speed ratios without using a number of exposed chain wheels. Similarly, the principle discussed above is also applicable to facilitate the control of the torque provided by the motor 500.

Besides what is discussed above, the present invention has an additional advantage that is the transmission of the rotation from the motor 500 to the rear wheel C of the bicycle is in a one-way fashion due to the provision of the one-way clutch 410 which prevents a backward movement of the bicycle by a person from causing the motor 500 to rotate reversely which results in current generated by the motor 500 in a reversed direction. Such a reversed current may damage the control circuit. Although the preferred embodiments have been described to illustrate the

present invention, it is apparent that changes and modifications in the specifical.ly described embodiments may be carried out without departing from the scope of the invention which is intended to be limited only by the appended claims.

17

Claims

CLAIMS 1 An auxiliary driving device of electrically assistant vehicle, 2 comprising: 3 4 6 7 8 9 11 12 13 14 is 16 17 18 19 20 21 22 23 24 26 a planetary gear set comprising a planetary gear support member, a sun gear, a ring gear and a plurality of planetary gears, the planetary gear support member being co-axially coupled to a driving pedal axle to be rotated by pedals attached to the driving pedal axle, the planetary gears being rotatably supported on the planetary gear support member and engaged by the ring gear at outer side and the sun gear at the inner side, the ring gear being co-axially fixed to a front driving chain wheel of the vehicle, the front driving chain wheel being coupled to a rear derailleur via a chain so as to drive a rear wheel of the vehicle; a driving bevel gear having a collar section with an inner bearing fit therein to rotatabIy receive the pedal axle therein, the collar being fit into a central bore of the front driving chain wheel and keyed to the sun gear to be drivingly coupled to the sun gear, a one-way clutch being provided bewteen the collar and the driving bevel gear; an auxiliary motor, mounted to a frame of the vehicle and having an output spindle with an output bevel gear fixed thereon, the output bevel gear being engaged by the driving bevel gear in a right-angled manner to drive the driving bevel gear so as to rotate the sun gear and thus supply auxiliary rotation and torque to the ring gear of the planetary gear set and the front driving chain wheel; 18 27 28 29 30 31 32 33 34 3 4 5 6 7 a pluarity of sensors, mounted to the planetary gears or a position suitable to detect rotational speed and to the rear wheel of the vehicle for detection of the rotational speed of the pedals and the rear wheel; and a controller receiving the rotational speeds of the pedals and the rear wheel from the sensors to control the operation of the motor in supplying auxiliary rotational speed and torque to the planetary gear set and the front driving chain wheel. 1 2. The auxiliary driving device of electrically assistant vehicle as 2 claimed in Claim 1, wherein the front driving chain wheel of the planetary gear set comprises a single chain wheel or a chain wheel set comprising a plurality of chain wheels of different tooth numbers and wherein the rear derailleur that is drivingly coupled to the front driving chain wheel comprises a single speed ratchet or a chain wheel set that is comprised of a number of chain wheels of different tooth numbers or a multi-staged drum type internal derailleur or a drum type stepless internal derailleur.

1

2

3 4 6 7 8 9 11 3. The auxiliary driving device of electrically assitant vehicle as claimed in Claim 1, wherein the sensors comprise motor, photo-electric switch, proximity switch, reed switch, Hall IC or other speed detecting devices, signals representing the rotational speeds of the pedals and the rear wheel provided by the sensors being processed by an operation circuit to provide an error signal which is applied to the controller; the operation circuit comprising a plurality of independent integration circuit and signal addition circuit constituted by operational amplifiers; the controller comprising a plurality of operational amplifier and a power control IC for controlling the rotational speed and torque provided by the motor in response to 19 12 13 14 change of ratio between tooth numbers of the rear derailleur and the front driving chain wheel so as to make the output of rotational speed and torque of the auxiliary motor linear.

4. An auxiliary driving device substantially as herein described with reference to and as illustrated in Figs. 1 to 5 of the accompanying drawings.

5. An electrically assistant vehicle haviAg an auxiliary drive device according to any of the preceding claims.