GB2284106A

GB2284106A - Alternator for vintage motorcycles

Info

Publication number: GB2284106A
Application number: GB9421920A
Authority: GB
Inventors: Herve Hamon
Original assignee: FORMATS AGENCE
Current assignee: FORMATS AGENCE
Priority date: 1993-11-02
Filing date: 1994-11-01
Publication date: 1995-05-24
Anticipated expiration: 2014-11-01
Also published as: FR2712124B1; FR2712124A1; GB9421920D0; GB2284106B

Abstract

A permanent-magnet alternator for vintage motorcycles comprises a rotor (22) including a ferromagnetic cylindrical body mounted on a shaft (17), said rotor rotating about a stator (20) having windings (19) that supply a load circuit, in such a way that the rotating magnetic field produced by the rotor induces an electrical alternating current in the windings of the stator: characterized in that the shaft (17) of the rotor (22) is connected to an input shaft (1) by means of a reduction gear cluster comprising: an internally toothed gear (27) fixed to one end of the shaft (17) of the rotor (22) and an externally toothed spur gear (10) that meshes with the internally toothed gear (27) and is fixed to one end of the input shaft (1), said input shaft (1) being parallel to the shaft (17) of the rotor (22) and being offset with respect to it. <IMAGE>

Description

ALTERNATOR FOR VINTAGE MOTORCYCLES The invention pertains to the field of mechanics.

More specifically, the invention pertains to the making of alternators for motorcycles and more particularly for old or vintage motorcycles.

The interest in vintage motorcycles, namely motorcycles manufactured up till the 1960s, has grown especially in Great Britain and in the United States and has gradually spread to other countries like France. These machines are increasingly being sought after by certain collectors as well as certain motorcycle enthusiasts.

Most usually, therefore, the owner of a vintage motorcycle has to restore it to its original condition so that it can be used again on the road.

Certain aspects of this restoring work may raise technical problems, especially as regard the current generator.

Indeed, all motorcycles up to 1958 were fitted out with six-volt dynamos. Certain makes of motorcycles kept these dynamos up till the 1960s.

Not only are such dynamos no longer manufactured, but they have the drawback of being ill-suited to present-day traffic conditions and to the highway code. Furthermore, they are technically complicated, unreliable and electrically lowpowered, especially at low speeds.

Since the architecture and usual technology of alternators is greatly different from that of dynamos, it has not been possible to mount alternators as elements replacing the dynamos. Hence, alternators have been mounted on motors designed solely for this purpose.

Depending on the type of alternator, the inductor which is formed by a coil and magnetic poles may be a rotor rotating around a stator or armature, or again rotating within the stator or armature.

In certain cases, the inductor coil of the rotor may be replaced by permanent magnets, thus simplifying the technology.

It is to this latter type of so-called permanent-magnet alternator that the invention pertains.

At present, there are no alternators on the market having the sizes and characteristics that would enable them to be adapted to motorcycles -originally fitted out with dynamos.

There is therefore a need for such alternators.

It is the aim of the invention to meet this need.

In particular, an aim of the invention is to provide an alternator having a shape and overall dimensions making it possible to easily replace the dynamo of a vintage motorcycle without its being necessary to carry out any major alteration or modification of the other mechanical parts of this motorcycle.

Another aim of the invention is to propose such an alternator.

These different aims as well as others that shall appear here below are achieved by means of the invention which relates to a permanent-magnet alternator for vintage motorcycles comprising: - a rotor including a ferromagnetic cylindrical body mounted on a shaft, said rotor rotating about a stator having windings that supply a load circuit, in such a way that the rotating magnetic field produced by the rotor induces an electrical alternating current in the windings of the stator, characterized in that said shaft of the rotor is connected to an input shaft by means of a reduction gear cluster comprising: - an internally toothed gear fixed to one end of the shaft of the rotor and, - an externally toothed spur gear that meshes into said internally toothed gear and is fixed to one end of said input shaft, said input shaft being parallel to the shaft of the rotor and being offset with respect to it.

The offset of the input shaft with respect to the axis of the rotor and the presence of the reduction gear cluster enable the rotation speed of the input shaft to be adapted to the rotor of the alternator. This current is then rectified by means of diodes and regulated by a power Zener diode.

Preferably, the diametral pitch m of the gears is 1.27 (or 20 DP). Indeed, this diametral pitch should be a sub-multiple of the distance between centres of the two gears which is half an inch (12.7 mm), a size identical to that of the offset of the input shaft of the dynamos.

Advantageously, said input shaft is offset with respect to said shaft of the rotor by a distance of 12.7 mm. This distance corresponds to half an inch.

Also preferably, said internally toothed gear has a number of teeth Zl greater by 20 than the number Z2 of teeth of the spur gear.

It will be noted that it is also possible to choose any reduction ratio between 0.5 and 0.6 provided that the difference between Zl and Z2 is 20 teeth.

According to one variant of the invention, the number Zl of teeth of said internally toothed gear is equal to 50 and the number Z2 of teeth of said spur gear is equal to 30, the reduction ratio of said gear cluster then being 0.6.

According to another variant of the invention, the number Zl of teeth of said internally toothed gear is equal to 40 and the number Z2 of teeth of said spur gear is equal to 20, the reduction ratio of said gear cluster being then 0.5.

Again advantageously, the alternator according to the invention has an overall diameter of three inches. This diameter was indeed the one most commonly used for dynamos in vintage motorcycles of British make.

The invention as well as its different advantages will be understood more clearly from the following description of an embodiment, made with reference to the appended drawings of which: - Figure 1 shows a longitudinal sectional view of a permanent-magnet alternator according to the invention; - Figure 2 gives a schematic view of the gear cluster of the alternator shown in Figure 1 seen in a front view.

Referring to Figure 1, the alternator according to the invention has a rotating part and a fixed part. The fixed part is formed by a front support 7 on which there is mounted a central support 12 and by a stator 20 mounted on the central support. The rotating part is formed by the input shaft 1, the rotor 22 and the rotor shaft 17.

The front support 7 is bored so as to be capable of receiving the input shaft 1 connected to the crankshaft of the motorcycle engine, while the central support 12 is bored so as to receive the rotor shaft 17. A half-inch offset is designed between the alignment of the input shaft 1 and the shaft of the rotor 22 as will be understood more clearly with reference to Figure 2.

The rotor 22 of the alternator shown is formed by magnets 21 positioned essentially in parallel to the axis of the rotor 22 and mounted above the stator. This rotor is protected by a cap 23.

The stator 20 for its part has a coil 19 designed to convey the current, induced by the movement of the rotor about the stator, towards the electrical supply, circuit of the vehicle.

It is fixed by means of a nut 18 to the central support 12.

Bearings 13 and 15 are provided at each end of the rotor shaft 17 in order to permit the free rotation of this shaft about itself in the central support 12. A joint 16 located close to the bearing 15 and a clip 25 and a shim ring 14 secure the positioning of the rotor shaft 17 in this bearing.

The gear cluster of the alternator is constituted by: - an internally toothed gear 27 whose flange 26 is fixedly joined to the rotor shaft 17 by means of a key 24 and a screw 28, and - a spur gear 10 fixedly joined to the input shaft 1 by means of a key 29 and a screw 9 provided with a clamping washer 11.

During the working of the alternator, the spur gear 10 rotates in the internally toothed gear 27 so as to transmit the rotational motion of the input shaft 1 to the rotor shaft 17 and thus enable the induction of an electrical current in the coil 19 of the stator 20.

A gear cluster such as this makes it possible to compensate for the offset between the input shaft 1 and the rotor shaft 17 and thus makes it possible to adapt the alternator according to the invention to the position previously occupied by the dynamo.

The rotation of the input shaft 1 in the front support 7 is organised by bearings 3 and 8. A clip 5 and a joint 2 are provided at the position of the bearing 3 in order to secure the positioning of the shaft 1 at the nose 4 of the front support.

In Figure 2, which gives a schematic view of the gear cluster of the alternator shown in Figure 1 in a front view, the internally toothed gear 27 has a diameter R and the spur gear 10 has a diameter r. The diameter of the gear 27 and that of the spur gear are related by the formula: R = 1 2. 7 mm + r 12.7 mm corresponding to the offset between the axes of the shafts 1 and 17, namely half an inch.

It being known that the radius of the gears is related to the number of their teeth by the formulae 2R = m Zl and 2r = m Z2 wherein m is the diametral pitch of the gear system. It is deduced therefrom that this diametral pitch should be a submultiple of 25.4 to give an integer.

my1/2 = mZ2 + 12.7 my1/2 = mZ2 = 12.7 m(Zl - Z2) = 25.4 Z1 - Z2 = 25.4/m In the framework of the present exemplary embodiment, m is equal to 1.27 (giving a diametral pitch or DP of 20 which is very commonly used in Great Britain), corresponding to a difference between the number of teeth of the internally toothed gear 27 and the number of teeth of the spur gear 10 equal to 20: Zl - Z2 = 25.4/1.27 = 20 For a diametral pitch of 1.27, the internally toothed gear 27, whose diameter is limited to 69.8 mm, may have a maximum of 20 teeth. The spur gear 10 will therefore, in this case, have a number of teeth Z2 equal to 30, giving a reduction ratio of 0.6.

According to need, it is also possible to use an internally toothed gear having a number of teeth Zl equal to 40 with a spur gear having a number of teeth Z2 leading to a reduction ratio of 0.5.

The exemplary embodiment of the invention described here is not designed to reduce its scope. In particular, it is possible to envisage the making of an alternator having gear dimensions different from those indicated herein.

Claims

1. A permanent-magnet alternator for vintage motorcycles comprising: a rotor including a ferromagnetic cylindrical body mounted on a shaft, said rotor rotating about a stator having windings that supply a load circuit, in such a way that the rotating magnetic field produced by the rotor induces an electrical alternating current in the windings of the stator, characterized in that said shaft of the rotor is connected to an input shaft by means of a reduction gear cluster comprising: an internally toothed gear fixed to one end of the shaft of the rotor and, an externally toothed spur gear that meshes with said internally toothed gear and is fixed to one end of said input shaft, said input shaft being parallel to the shaft of the rotor and being offset with respect to it.

2. An alternator according to claim 1, characterized in that the diametral pitch m of the gears is 1.27.

3. An alternator according to claim 2, characterized in that said input shaft is offset with respect to said shaft of the rotor by a distance of 12.7 mm.

4. An alternator according to claims 2 and 3, characterized in that said internally toothed gear has a number of teeth Zl greater by 20 than the number Z2 of teeth of the spur gear.

5. An alternator according to claim 4, characterized in that the number Zl of teeth of said internally toothed gear is equal to 50 and in that the number Z2 of teeth of said spur gear is equal to 30, the reduction ratio of said gear cluster then being 0.6.

6. An alternator according to claim 5, characterized in that the number Zl of teeth of said internally toothed gear is equal to 40 and in that the number Z2 of teeth of said spur gear is equal to 20, the reduction ratio of said gear cluster being then 0.5.

7. An alternator according to any of the claims 1 to 6, characterized in that its overall diameter is three inches.

8. An alternator according to claim 1 and substantially as hereinbefore described with reference to, and as shown in the accompanying drawings.