Electrical generator or motor structure – Dynamoelectric – Rotary
Reexamination Certificate
2001-08-13
2004-04-13
Le, Dang (Department: 2834)
Electrical generator or motor structure
Dynamoelectric
Rotary
C310S057000, C310S058000, C310S059000, C310S266000, C310S268000
Reexamination Certificate
active
06720688
ABSTRACT:
BACKGROUND OF THE INVENTION
An electric machine with a rotor which is rotatably mounted in a housing with a rotor shaft which extends beyond the housing, a plurality of electromagnet components which are statically disposed in the housing at uniform angular spacings and spaced from the axis of rotation of the rotor, each with a coil core bearing a coil winding consisting of one or more conductors and with permanent magnets which are disposed at uniform angular spacings and are non-rotatably retained in or on the rotor, these permanent magnets each having a pole face aligned opposite the end faces of the coil cores and each having a polarity which is successively reversed in the peripheral direction, wherein the coil cores of the electromagnet components are disposed parallel to the axis of rotation of the rotor shaft in the interior of the housing in such a way that their opposing end faces each lie in two planes which are spaced from one another and extend at right angles to the axis of rotation of the rotor shaft and the ends of the electric conductors which form the coil winding of the individual electromagnet components are interconnected via an electric or electronic control device to form at least two pairs of electrical connections and the rotor has at least two outer armature discs which extend radially to before the end faces of the coil cores and in which the permanent magnets are retained with their pole faces aligned with the respective associated end faces of the coil cores, the radially inner region of the said armature discs being provided with holes.
Such machines which can be connected to electric current sources are used for example as wheel hub motors for vehicle drives because of the favourable power-weight ratio. In this case these motors are designed so that the permanent magnets are retained in a disc, which is made from non-magnetic material and is non-rotatably connected to the rotor shaft, in such a way that their pole faces open freely on both sides into the flat sides of the disc-shaped rotor armature, the magnets being disposed so that in the peripheral direction successive pole faces on the same side of the armature have alternating polarities. The electromagnet components in the form of coils wound on metal cores are disposed on the inner faces of the housing cover or radial housing walls facing the disc-shaped rotor armature at a distance corresponding to the average radial distance of the permanent magnets from the axis of rotation of the rotor shaft. The control of these coils is achieved preferably by an electronic control device which generates a magnetic rotating field, so that the control of contacts sliding on a commutator, which is basically also conceivable but is susceptible to wear, is omitted. Such electronically controlled machines are also designated as brushless disc armature machines (GB 2 275 371 A). Furthermore, brushless disc armature machines are also known in which the rotor has two outer armature discs which extend radially to in front of the end faces of the coil cores which are fixed on the housing, the permanent magnets being retained in these armature discs with their pole faces aligned with the respective associated end faces of the coil cores (e.g. DE 197 01 797 A, FIG. 18; DE 42 14 483).
SUMMARY OF THE INVENTION
The object of the invention is to improve the efficiency of the known electric machines and to minimise any decline in the power due to reduction of the magnetisation of the permanent magnets over the course of time. At the same time the machines should be economical and simple to produce and should have a favourable unit weight.
Starting from an electric machine of the type mentioned in the introduction, this object is achieved according to the invention in that in each case pairs of legs, which succeed one another in the peripheral direction and are each provided with a pole face of different polarity on the free end facing the coil, of the permanent magnets provided in the two opposing outer armature discs are connected to one another in the end regions remote from the pole faces by a respective yoke which encloses the magnetic field and is made from soft or hard magnetic material, that the armature discs are connected to one another by radially extending walls which form the cavity between the armature discs into a plurality of chambers which are offset with respect to one another in the peripheral direction and are open towards the electromagnet components, and that the radially inner holes provided in the armature discs each open into the chambers of the rotor. The permanent magnets which are associated with the electromagnet components disposed centrally between both armature discs and thus are rigidly fixed on the peripheral wall of the housing of the machine are constructed in the manner of horseshoe magnets by means of the yokes which in each case connect two single magnets which succeed one another in the peripheral direction, resulting in a construction of the motor in which the magnetic field of the permanent magnets is kept contained as far as possible within the magnetic material of the permanent magnets, connected by the yoke, of the coil core, so that a low magnetic leakage field can be produced only in the narrow air gap between the end faces of the coil cores of the electromagnet components and the pole faces of the electromagnets. Losses of the magnetic rotating field generated in the electromagnetic components when the machine is switched on as motor are therefore minimised. This also applies when the machine is used as generator, which suggests itself for example for wind generators in which a direct coupling of the axis of rotation of the rotor to the output shaft of the wind wheel is possible without connection of a reduction gear between them. In addition to the favourable electric efficiency of the generator, the mechanical losses in the transmission gear are also avoided. In this case the radially extending walls which connect the armature discs act like the blades of a fan, i.e. via the radially inner holes in the armature discs air is drawn out of the housing and is blown radially outwards between the electromagnet components as a cooling air stream.
In the simplest case a row of electromagnet components is provided in the interior of the housing of the machine, and then the rotor has two outer armature discs guided on opposing sides in front of the coil core end faces of the electromagnet components.
The power of the machine can be increased without increasing the diameter in that two or more rows of electromagnet components spaced from one another in the longitudinal direction of the rotor shaft are disposed in the interior of the housing, wherein in addition to the two outer armature discs which are guided in front of the outer end faces of the coil cores, pointing in opposite directions, of the outermost rows the rotor has an additional armature disc with permanent magnets guided into each space between adjacent rows of electromagnet components in front of the end surfaces thereof which face one another, and the pole faces of differing polarity of the permanent magnets which are each exposed on opposing sides of the respective additional armature disc are aligned in the radial direction with the end faces of the coil cores of the rows of electromagnet components. Thus the permanent magnets disposed in the additional armature discs are—unlike the permanent magnets in the outer armature discs—constructed not as horseshoe magnets but as bar magnets of short length in order thus to keep the air gaps small between the pole faces of these magnets and the facing end surfaces of the coil cores of the electromagnet components and thus to avoid losses due to magnetic leakage fields.
In this case the interior of the housing is advantageously closed off and sealed against the external atmosphere, this sealing being achieved in the region of the shaft of the machine extending beyond the housing by a corresponding seal. The air drawn in from the housing through the radially inner holes in
Le Dang
Norris & McLaughlin & Marcus
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