IL109667A - Auxiliary drive for pedal-driven road vehicles - Google Patents

Description

AUXILIARY DRIVE FOR PEDAL-DRIVEN ROAD VEHICLES The present invention relates to an electric auxiliary drive to assist pedal-driven road vehicles, in particular bicycles. It also relates to a kit for turning a standard pedal-driven vehicle into an electrically-assisted one.

Although transportation is usually associated with engine power, the greatest share of personal transport needs is supplied by human power. Bicycles in Asia alone transport more people than all the world's cars.

Countries that have become dependent on the car are paying a high price in road accidents, air pollution, noise, urban congestion, parking problems, and the cost of fuel. In many countries, cars and other motor vehicles account for more than half their petroleum consumption, and create more air pollution than any other cause thereof.

The bicycle option, as a commuting link for short-distance travel, appeals to more and more countries. Much of Europe is moving towards pro-bicycle planning (i.e., Sweden, Switzerland, Germany, the Netherlands, Denmark). They believe that increased use of bicycles will curb the steep growth of motor transportation before urban air becomes unbreatheable and rush-hour traffic grinds to a complete standstill.

For every person who makes a trip by bicycle instead of by car, there is less pollution, less fuel used, and less space taken on the road. Bicycles use less energy per passenger kilometer than any other form of transport, including walking. A 16-kilometer trip by bicycle uses 350 calories of energy - the amount contained in one bowl of rice. The same trip in an average American car uses 18,600 calories, or more than half a gallon of gasoline.

While bicycles are lightweight, environmentally friendly and traffic-flexible, occasionally cycling calls for an excessive human effort that stresses the human body to its limits, such as when cycling up steep gradients, in high winds, etc. In such situations, the cyclist could use some assistance.

It is obvious that a well-designed, electric, auxiliary power drive attachment for bicycles which assists the human body in overcoming its limitations, will encourage wider usage of bicycles for transportation.

Electrically-assisted bicycles are known. European Patent 0 168 905 discloses an auxiliary drive for pedal-driven road vehicles having a battery-powered motor that can function as mover, drawing energy from the battery and imparting it to the vehicle, as well as a generator, drawing energy from the vehicle by the regenerative braking thereof on downhill stretches.

Other known electrically-assisted bicycles, known in Europe as "Mofas" or "Mopeds," are the "Electra" by Hercules (Germany) and the "Velomatic" by Velectro (Austria). These bicycles have a no-pedaling option, enabling the cyclist to travel by motor power only. As a consequence, energy consumption is high, calling for heavy and bulky batteries and a large motor, adding another 15-20 kg to the bicycle weight. Actually, these electric Mopeds and Mofas are bicycles only in the literal sense of the term. These are new electric vehicles, relatively heavy (over 30 kg), bulky (no folding option), short-distance (no energy recuperation) and expensive.

It is thus one of the objectives of the present invention to provide an electric power drive for all types of bicycles or other pedal-driven road vehicles that assists rather than substitutes for muscle power, and that facilitates a combination and smooth interaction of human and electrical energies.

It is another objective of the present invention to provide a compact electrical drive having a small, powerful motor using a lightweight rechargeable battery, which motor, by back-pedaling on flat or downhill stretches, can be turned into a generator, refreshing the battery and returning to it at least some of the energy drawn from it during motor-assisted uphill driving.

According to the invention, these objectives are achieved by providing an electric auxiliary drive for a pedal-driven road vehicle, comprising an electric motor; a rechargeable, multi-cell battery to power said motor; switch means to control said motor, which motor is adapted to operate in a first mode in which it functions as a mover, drawing energy from said battery and imparting it to said vehicle, and in a second mode in which it functions as a generator, drawing energy from the user of said road vehicle via the pedals thereof, and imparting it to said battery; transmission means to provide for the moving of said vehicle by said motor when operating in said first mode, and to enable said user to impart a rotary movement to said motor in said second mode of operation; an overrunning clutch interposed between said transmission means and the axle of said pedals, wherein said clutch free-wheels when said user moves said vehicle by pedaling in the forward direction, and said clutch engages when said motor is made to assist said user in said first mode of operation or when said user backpedals, to drive said motor in said second mode of operation.

The invention further provides a kit for turning a standard pedal-driven road vehicle into an electrically-assisted road vehicle, comprising an electric motor mounted on a casing accommodating a worm and a worm wheel which is fixedly attached to a gear pinion; a rechargeable, multi-cell battery; a box containing the electrical circuitry for the drive; two lugs to be attached to a bottom bracket bearing for mounting said motor and said casing; a pedal crank, to which is fixedly attached the inner race of an overrunning clutch, and a gear wheel, which is fixedly attached to the outer race of said overrunning clutch.

It will be appreciated that the drive according to the invention is suitable only for pedal-driven road vehicles which have a simple, free-wheeling rear hub. These hubs are, in any case, rapidly replacing the inferior coaster brake hubs.

The idea behind the invention is best understood by considering the following Table 1, which relates the energy demand on the cyclist to the gradient of the road as a function of cycling speed.

TABLE 1 Energy (W) calculated for a weight (rider + bicycle) of 100 kg for various gradients (°) and speeds (km/h): Speed km/h 3° 4° 5° 6° 7° 5 73 98 122 140 168 8 77 154 191 220 240 10 98 196 244 280 340 12 112 231 288 330 400 15 147 294 365 420 500 An average cyclist expends 35-40 W in an easy ride at 15 km/h on flat terrain. This cyclist is able to double his effort to 70-80 W and climb an easy uphill gradient of 3° at a speed of 8 km/h for 20 to 25 minutes. But, as shown in Table 1 above, climbing an even relatively moderate uphill gradient of 5° at a speed of 8 km/h, the cyclist has to invest 191 W, which means that he is lacking 110-120 W. The electric drive is meant to compensate him for this shortage.

In case the cyclist contributes only 40 W while climbing the 5° gradient, which he can easily manage, the drive will add the balance of 150 W. If the cyclist is able or willing to invest 80 W, the drive will provide the balance of 110 W, and so forth.

It should be noted that the complementary relationship between the energy invested by the cyclist and the energy drawn from the battery is a function of the load on the motor .

The invention will now be described in connection with certain preferred embodiments with reference to the following illustrative figures so that it may be more fully understood.

With specific reference now to the figures in detail, it is stressed that the particulars shown are by way of example and for purposes of illustrative discussion of the preferred embodiments of the present invention only, and are presented in the cause of providing what is believed to be the most useful and readily understood description of the principles and conceptual aspects of the invention. In this regard, no attempt is made to show structural details of the invention in more detail than is necessary for a fundamental understanding of the invention, the description taken with the drawings making apparent to those skilled in the art how the several forms of the invention may be embodied in practice.

In the drawings: Fig. 1 is a general view of a bicycle fitted with an electric auxiliary drive according to the invention; Fig. 2 is a kinematic drawing of the device, showing the interconnection of the different components; Fig. 3 is a partly cross-sectional view of the internal gear and the overrunning clutch; Fig. 4 is a schematic representation of the device as mounted; Fig. 5 shows the factory-attached lugs for mounting the device; Fig. 6 illustrates the mounting lugs as modified for self- assembly of the device, and Fig. 7 represents the electrical circuit of the device according to the invention.

Referring now to the drawings, there is seen in Fig. 1 a bicycle equipped with the electric auxiliary drive according to the invention. Attached to the bottom bracket bearing 2, in a manner to be explained further below, is an electric motor 4 and, mounted in a casing 5, its integral reduction gearing 6, shown to better advantage in Fig. 2. The output member of this gearing is a pinion 8 which meshes with a relatively large internal gear 10 mounted on the axle 12 of the pedal cranks 13 via an overrunning clutch 14, seen to better advantage in Figs. 2 and 3. Also seen is the standard chain wheel 16 and chain 18. The battery 20 is advantageously accommodated on the luggage carrier 22, but could also be suspended from the cross bar 24 or attached to the down tube 26. The electric circuitry is accommodated in a box 27. The device is operated by pushing a button 28 mounted on the handlebar.

As can be best seen in Fig. 2, the internal gear 10 is located on one side of the bottom bracket bearing 2, and the chain wheel 16 is located on the other side thereof.

Commercially available D.C. motors operating nominally on, e.g., 12 V have speeds of 3000-5000 rpm. If operating on over- voltage, as will be explained further below, their speed will be even higher. As a cyclist operates his pedals at a rate of about 40-60 rpm, the motor 4 of Fig. 1 must be geared down at a ratio of about 1:80. As seen in the kinematic drawing of Fig. 2, reduction is effected in two stages, the first of which is a worm gearing 6 consisting of a 3-start worm 30 mounted on the motor shaft and meshing with a worm wheel 32 having 34 teeth. The second stage consists of a gear pinion 8 which constitutes the output member of the worm gearing of the first stage. It has 12 teeth and meshes with an internal gear 10 having 85 teeth, which provides an overall reduction of 3 x 12 1 34 x 85 80 The pitch angle of the worm 30 must be large enough to make the worm gearing reversible, i.e., not only is the worm 30 to drive the worm wheel 32, but the latter must also be able to drive the former. This is not the case with standard worm gearing which is self-locking, i.e., the worm wheel cannot drive the worm.

The internal gear 10 adds to the compactness of the device as well as to safety, as its working face as well as the point of engagement with pinion 8 is turned inwards, i.e., away from the cyclist's leg.

The internal gear 10, as can be seen in Figs. 2 and 3, is not directly mounted on the pedal axle 12, but is fixedly attached to the outer race 34 of the overrunning clutch 14, the inner race 36 of which is fixedly connected to the pedal crank 13, preferably by being brazed to the head of the pedal crank 13 which is keyed to the axle 12 in the usual manner.

The mounting of the device is best understood from the schematic drawing of Fig. 4, in conjunction with Figs. 5 and 6.

There is provided a pair of lugs 38 (of which only one is seen in Fig. 4, the other being located behind the casing 5) having holes 40 (see Figs. 5, 6). The casing 5 has two holes 42 at the center distance of holes 40, to which casing the motor 4 is attached. The casing also accommodates the worm 30 and worm wheel 32, and the pinion 8 projects therefrom. The casing is inserted between the pair of lugs 38 and is clamped tight with the aid of bolts 44.

The device according to the invention can either be factory-delivered as an integral part of a new pedal-driven vehicle such as a bicycle, or can be bought as a kit for self-assembly.

In the first case, the lugs 38, as shown in Fig. 5, are made an integral part of the bicycle frame, i.e., are brazed or welded to the bottom bracket bearing 2 at the proper spacing and in proper angular relationship to the seat and down tubes 25, 26 (not shown).

In the second case, the lugs 38' are angled off and have a large bore 48 that slips over the bearing end 50, and are tightly pressed against the shoulders of the bottom bracket 2 by means of the nuts 52.

To further stabilize the position of the casing 5, there is provided a fork-like brace 46, the forked end of which grips the lugs 38 and is attached thereto by means of one of the bolts 44. The other end of brace 46 is clamped to the chain stays 48. At least one of the holes 42 in the casing 5 is advantageously slightly enlarged to facilitate fine adjustment of the mesh and clearance between the pinion 8 and the internal gear 10.

Further components of the kit include — apart from the battery 20, the circuitry box 27, the wiring, the motor 4 mounted on the casing 5, the reduction gearing 6 and the pinion 8 — a pedal crank 13, to the head of which is brazed or welded the inner race 36 of an overrunning clutch 14, and to the outer race 34 of which clutch is fixedly attached the internal gear 10 that meshes with the gear pinion 8.

When assembling the kit, one first removes the pedal cranks 13 and the nuts 52 (Fig. 6), and attaches the lugs 38' as above described. Then the nuts 52 are returned, but not fully tightened. The next step is the mounting, between the lugs 38', of the casing 5 carrying the motor 4 and its reduction gearing 6. After that, the forked end of brace 46 is slid over the lugs 38' and when the holes of brace 46, the holes of lugs 38' and the holes in casing 5 are brought into alignment, one of the bolts 44 is pushed into the assembled components. Then, the rear end of brace 46 is attached to the chain stays 48. Finally, screws 44 as well as nuts 52 are tightened, the pedal crank 13 on the side of chain wheel 13 is attached to pedal axle 12, and so is the pedal crank 13 that carries internal gear 10.

Fig. 7 represents the electrical circuit of the drive according to the invention, with only the lower, boxed-in circuit relating to the drive itself. The upper circuit is optional, and permits the bicycle lights to be selectively powered either by the standard dynamo, or by the battery 20.

When the push button 28 is pressed in the first operational mode, the relay 54 is energized and opens the normally closed contacts AB while closing the normally open contacts AC, thus closing the motor circuit via shunt 56 and actuating the auxiliary drive. When the cyclist, by back-pedaling, intends to operate the motor in the second mode, i.e., as generator charging the battery 20, the push button 28 is open, and the current generated flows via shunt 56, through the lower contacts AB to the battery +, and from the battery - through the upper pair of contacts AB via the diode 58 back to the motor/generator 4. This diode is required to cut off the battery-motor circuit when the push button 28 is not pressed. The amperemeter and voltmeter are advantageously mounted on the handlebar.

In the upper, optional circuit there is seen a dynamo 60 which, via a transformer 62, produces an A.C. voltage for the front and rear lights F, R of the bicycle, which voltage has the same amplitude as the battery voltage. It is thus possible to use the same bulbs for lighting either by means of the dynamo or via the battery 20 by throwing the light switch 64. Diodes 66, 68 prevent a short circuit via the grounded transformer coil when the switch 64 is closed. They also function as rectifiers.

In operation, the drive according to the invention functions as follows: During regular, pedal-powered travel, the overrunning clutch 14 freewheels and the internal gear 10 is stationary. When, for instance on a downhill stretch, the cyclist takes up the back-pedaling option to recharge the battery 20, the rear hub of the bicycle is free wheeling, the backward rotating inner race 36 of the overrunning clutch 14 begins to carry along the outer race 34 together with the internal gear 10 which, via the pinion 8 and the reversible worm gearing 6, drives the motor 4 in the opposite direction, thus making it work in the second mode, i.e., turning it into a generator and thus converting the cyclist's muscle energy into electrical energy used to charge the battery. Of course, the major part of recharging is done at home, e.g., during the night, using one of the conventional chargers that are plugged into the mains.

It has been found that the use of over-voltage, e.g., making the voltage applied larger by about 50% of the rated

Claims (10)

- 13 - 109,667/2 WHAT IS CLAIMED IS:

1. An electric auxiliary drive for a pedal-driven road vehicle, comprising: an electric motor; a rechargeable multi-cell battery to power said motor; switch means to control said motor, which motor is adapted to operate in a first mode in which it functions as a mover, drawing energy from said battery and imparting it to said vehicle, and in a second mode in which it functions as a generator, drawing energy from the user of said road vehicle via the pedals thereof, and imparting it to said battery; transmission means to provide for the moving of said vehicle by said motor when operating in said first mode, and to enable said user to impart a rotary movement to said motor in said second mode of operation; an overrunning clutch interposed between said transmission means and the axle of said pedals, wherein said clutch free-wheels when said user moves said vehicle by pedaling in the forward direction, and said clutch engages when said motor is made to assist said user in said first mode of operation or when said user backpedals, to drive said motor in said second mode of operation, and wherein all transmission means used to impart said rotary movement to said motor/generator in said second mode of operation are positive transmission means.

2. The drive as claimed in claim 1, wherein said overrunning clutch has an outer member and an inner member. - 14 - 109,667/2

3. The drive as claimed in claims 1 and 2, wherein said transmission means comprises: a worm fixedly attached to the shaft of said motor; a worm wheel meshing with said worm; a gear pinion keyed to the shaft of said worm wheel, and a gear wheel meshing with said pinion and fixedly attached to the outer member of said overrunning clutch, the inner member of which is kinematically connected to said pedal axle.

4. The drive as claimed in claim 3, wherein said gear wheel is an internal gear.

5. The drive as claimed in claim 1, wherein said motor is fixedly attached to a casing which also accommodates said worm wheel meshing with the worm attached to the shaft of said motor.

6. The drive as claimed in any of the preceding claims, further comprising two lugs fixedly attached in spaced-apart relationship to the bottom bracket bearing of said pedal-driven road vehicle, between which lugs is fixedly mounted said casing carrying said motor and accommodating said worm wheel, whereby, when mounted between said lugs, the gear pinion coaxial with said worm wheel will be in proper mesh with said internal gear. - 15 - 109,667/2

7. A kit for converting a standard pedal-driven road vehicle into an electrically-assisted road vehicle as claimed in claim 1, comprising: an electric motor mounted on a casing accommodating a worm and a worm wheel to which is fixedly attached a gear pinion; a rechargeable multi-cell battery; a box containing the electrical circuitry for said drive; two lugs to be attached to a member of the frame of said vehicle for mounting said motor and said casing; a pedal crank, to which is fixedly attached the inner race of an overrunning clutch, and a gear wheel, which is fixedly attached to the outer race of said overrunning clutch.

8. The kit as claimed in claim 7, further comprising a fork-like brace supporting said casing with one of its ends, and clamped onto a structural member of said road vehicle at its other end.

9. An electric auxiliary drive for a pedal-driven road vehicle according to claim 1, substantially as hereinbefore described and with reference to the accompanying drawings. - 16 - 109,667/2

10. A kit for converting a standard pedal-driven road vehicle into an electrically-assisted road vehicle according to claim 7, substantially as hereinbefore described and with reference to the accompanying drawings. for the Applicant: WOLFF, BREGHAN AND GOLLER