GB2025708A

GB2025708A - Electrical self-exciting generator

Info

Publication number: GB2025708A
Application number: GB7924391A
Authority: GB
Original assignee: Robert Bosch GmbH
Current assignee: Robert Bosch GmbH
Priority date: 1978-07-13
Filing date: 1979-07-12
Publication date: 1980-01-23
Also published as: FR2431214A1; DE2830713A1; JPS5517298A

Abstract

A generator has a fixed output winding 23' and an energizing device for producing a rotatable exciter field which includes a magnetic circuit and an excitation winding 22, the magnetic circuit, besides having weakly magnetic parts 16, 17, 19, also having magnetically hardened parts 21, 27, 29, 31. This improves the build-up of the exciter field on start up of the generator. <IMAGE>

Description

SPECIFICATION Electrical self-exciting generator There is provided by the present invention an electrical self-exciting generator for motor vehicles.

-With electrical self-exciting generators there is always the problem of building up an exciter field. If the magnetizable material used in the energizing circuit is magnetically very weak, the remanent induction is very slight and it takes a very long time for a generator to self-excite after starting up. It is already known practice to build up an exciterfield in three-phase-current generators in motor vehicles, in that, after actuation of the ignition switch, a preenergizing current flows through a resistor or the charging control light into the energizing circuit. It is also already known practice to improve the build-up, i.e. the starting behaviour of the generator, by also including oxide magnets at a suitable point in the energizing circuit, particularly between the claws of three-phase-current generators having claw-pole rotors.The disadvantage of these known measures is that they require a certain amount of circuitry or they have the disadvantage of low mechanical strength. At any rate, the extra cost outweighs any advantage gained.

There is provided by the present invention an electrical self-exciting generator for a motor vehicle having a fixed output winding and an energizing device for producing a rotatable exciter field which includes a magnetic circuit and an excitation winding, wherein the magnetizable circuit, besides having weakly magnetic parts, also has magnetically hardened parts.

A generator according to the invention has by comparison with the prior art the advantage that the manufacturing cost is very low and exciter field build-up of the generator is always ensured. There is no need for circuitry outside the generator. Another advantage is that in the normal operating sequence of manufacture of the generator only one extra working step is necessary, namely, the first magnetization of the magnetically hardened parts.

Further in an embodiment of the invention a particular advantage is that the volume of the generator is not increased and that no mechanically vulnerable parts are used.

An embodiment of the invention is illustrated in the accompanying drawing, the sole figure of which ,shows a slip-ring-free three-phase-current generator according to the invention.

In a cup-shaped generator housing having the two housing parts 11, 12 serving as bearing brackets, a rotor shaft 15 isjournalled in bearings 13 and 14. A core 16 of an energizing device is placed on the rotor shaft 15. The core 16 carries a first magnet wheel 17.

A second magnet wheel 19 is connected to the first magnet wheel 17 by means of a non-magnetic ring 18 so that the second magnet wheel is not directly fixed on the rotor shaft 15. The bearing bracket 11 on the drive side carries a holding device 21 on which an excitation winding 22 is fixed. A stator 23 carrying an output winding 23' is inserted in the housing parts 11 and 12. Connected axiaily displaced from the output winding 23' is a rectifier 24 which, besides supplying current by way of a voltage reguiator 25, also supplies the exciting current. Current is supplied through the cable 26.

There are now various possibilities of inserting magnetically hardened parts into the energizing circuit. Those which are described hereinafter have proved particularly economical.

It costs very little to manufacture the holding device 21 for the excitation winding 22 in steel instead of soft iron. However, the holding device 21 need not be made entirely from magnetically hardened material, parts of the holding device may alternatively by weakly magnetic. Also, it is relatively simple to place a magnetically hardened ring 27 on the core 16. Moreover, a magnetically hardened ring 29 may be fixed on the second magnet wheel 19, which is not directly fixed on the rotor shaft 15, on the side 28 facing the holding device 21 of the excitation winding 22. Finally, the tips 31 of the claws ofthetwo claw-pole wheels 17 and 19 may easily be made magnetically hardened. In these arrangements, the magnetically hardened parts lie in the magnetic flux in series with the weakly magnetic parts.

As a magnetically hardenable material, a carbonrich steel having a carbon content of up to 0.8% has proved particularly favourable.

A slip-ring-free three-phase-current generator, such as is used in motor vehicles, has been selected as an embodiment. Most of the measures described could, however, be employed just as easily in a generator having slip rings. Also, instead of the inserted magnetically hardened parts, the corresponding areas of the original weakly magnetized material could be carburized and then magnetically hardened. The described possibilities of using magnetically hardened material may be used individually or in any combination.

1. An electrical self-exciting generator for a motor vehicle, having a fixed output winding and an energizing device for producing a rotatable exciter field which includes a magnetic circuit and an excitation winding, wherein the magnetizable circuit, besides having weakly magnetic parts, also has magnetically hardened parts.

2. A generator as in claim 1, in which the magnetically hardened parts lie in the magnetic flux in series with the weakly magnetic parts.

3. A generator as in claim 1 or 2, in which the support of the excitation winding is at ieast partially made from a magnetically hardened material.

4. A generator as in claim 3 without slip rings, in which the holding device of the excitation winding is at least partially made from a magnetically hardened material.

5. A generator as in claim 3 or 4, in which a magnetically hardened ring is fixed on the core of the energizing device.

6. A generator as in any of the previous claims having claw poles and a rotor shaft and without slip rings, wherein a magnetically hardened ring is fixed

**WARNING** end of DESC field may overlap start of CLMS **.

Claims

**WARNING** start of CLMS field may overlap end of DESC **. SPECIFICATION Electrical self-exciting generator There is provided by the present invention an electrical self-exciting generator for motor vehicles. -With electrical self-exciting generators there is always the problem of building up an exciter field. If the magnetizable material used in the energizing circuit is magnetically very weak, the remanent induction is very slight and it takes a very long time for a generator to self-excite after starting up. It is already known practice to build up an exciterfield in three-phase-current generators in motor vehicles, in that, after actuation of the ignition switch, a preenergizing current flows through a resistor or the charging control light into the energizing circuit. It is also already known practice to improve the build-up, i.e. the starting behaviour of the generator, by also including oxide magnets at a suitable point in the energizing circuit, particularly between the claws of three-phase-current generators having claw-pole rotors.The disadvantage of these known measures is that they require a certain amount of circuitry or they have the disadvantage of low mechanical strength. At any rate, the extra cost outweighs any advantage gained. There is provided by the present invention an electrical self-exciting generator for a motor vehicle having a fixed output winding and an energizing device for producing a rotatable exciter field which includes a magnetic circuit and an excitation winding, wherein the magnetizable circuit, besides having weakly magnetic parts, also has magnetically hardened parts. A generator according to the invention has by comparison with the prior art the advantage that the manufacturing cost is very low and exciter field build-up of the generator is always ensured. There is no need for circuitry outside the generator. Another advantage is that in the normal operating sequence of manufacture of the generator only one extra working step is necessary, namely, the first magnetization of the magnetically hardened parts. Further in an embodiment of the invention a particular advantage is that the volume of the generator is not increased and that no mechanically vulnerable parts are used. An embodiment of the invention is illustrated in the accompanying drawing, the sole figure of which ,shows a slip-ring-free three-phase-current generator according to the invention. In a cup-shaped generator housing having the two housing parts 11, 12 serving as bearing brackets, a rotor shaft 15 isjournalled in bearings 13 and 14. A core 16 of an energizing device is placed on the rotor shaft 15. The core 16 carries a first magnet wheel 17. A second magnet wheel 19 is connected to the first magnet wheel 17 by means of a non-magnetic ring 18 so that the second magnet wheel is not directly fixed on the rotor shaft 15. The bearing bracket 11 on the drive side carries a holding device 21 on which an excitation winding 22 is fixed. A stator 23 carrying an output winding 23' is inserted in the housing parts 11 and 12. Connected axiaily displaced from the output winding 23' is a rectifier 24 which, besides supplying current by way of a voltage reguiator 25, also supplies the exciting current. Current is supplied through the cable 26. There are now various possibilities of inserting magnetically hardened parts into the energizing circuit. Those which are described hereinafter have proved particularly economical. It costs very little to manufacture the holding device 21 for the excitation winding 22 in steel instead of soft iron. However, the holding device 21 need not be made entirely from magnetically hardened material, parts of the holding device may alternatively by weakly magnetic. Also, it is relatively simple to place a magnetically hardened ring 27 on the core 16. Moreover, a magnetically hardened ring 29 may be fixed on the second magnet wheel 19, which is not directly fixed on the rotor shaft 15, on the side 28 facing the holding device 21 of the excitation winding 22. Finally, the tips 31 of the claws ofthetwo claw-pole wheels 17 and 19 may easily be made magnetically hardened. In these arrangements, the magnetically hardened parts lie in the magnetic flux in series with the weakly magnetic parts. As a magnetically hardenable material, a carbonrich steel having a carbon content of up to 0.8% has proved particularly favourable. A slip-ring-free three-phase-current generator, such as is used in motor vehicles, has been selected as an embodiment. Most of the measures described could, however, be employed just as easily in a generator having slip rings. Also, instead of the inserted magnetically hardened parts, the corresponding areas of the original weakly magnetized material could be carburized and then magnetically hardened. The described possibilities of using magnetically hardened material may be used individually or in any combination. CLAIMS

6. A generator as in any of the previous claims having claw poles and a rotor shaft and without slip rings, wherein a magnetically hardened ring is fixed on the magnetwheel, which is not directly fixed on the rotor shaft, on the side facing the holding device of the excitation winding.

7. A generator as in any of the previous claims having claw poles, in which the tips of the claw poles are magnetically hardened.

8. A generator as in any of the previous claims, in which a carbon-rich steel is used as a magnetic material.

9. A generator as claimed in claim 8, wherein the steel has up to 8% carbon therein.

10. An electrical self-exciting generator substantially as hereinbefore described with reference to the accompanying drawings.