Electrical generator or motor structure – Dynamoelectric – Rotary
Reexamination Certificate
1999-04-22
2001-05-08
Ramirez, Nestor (Department: 2834)
Electrical generator or motor structure
Dynamoelectric
Rotary
C310S164000, C310S254100
Reexamination Certificate
active
06229238
ABSTRACT:
BACKGROUND AND SUMMARY OF THE INVENTION
This application claims the priority of 198 18 035.7 filed Apr. 22, 1998, the disclosure of which is expressly incorporated by reference herein.
The invention relates to a transversal flux machine and a rotor arrangement for a transversal flux machine.
Permanent-magnet-excited synchronous machines according to the transversal flux concept are generally known and permit high force densities with high efficiency.
A transversal flux machine of the aforementioned type is described in European Patent Document EP 0 677 914. The transversal flux machine according to this document has a stator and a rotor as well as magnetic circuits. The flux of the magnetic circuits extends essentially transversely to the movement direction of the rotor. The stator has E-shaped pole elements, in the case of which the central pole shanks are arranged offset by one pole pitch with respect to the outer pole shanks. The permanent magnets of the rotor essentially have a cubical construction and are situated in their flux direction perpendicular to the adjoining pole surfaces of the pole elements, while they rotate between two shanks respectively of the E-shaped pole elements.
International Patent Document WO 90/09697 describes a permanent-magnet-excited electric machine which has an outer stator and at least one coaxial inner stator. A rotor rotates between these with two parallel rows of permanent magnets which extend at an axial distance from one another. Permanent magnets adjacent in the circumferential and axial direction have different polarities.
For the industrial manufacturing of such a machine, the outer stator and the inner stator are each constructed in three parts including a yoke ring and two laminated pole rings. The pole rings carry radially projecting pole teeth which are arranged in the rotating direction at a spacing of one pole pitch respectively. The laminated and segmented pole rings are pressed in the radial direction against the yoke ring and are supported in the axial direction on a ring web radially projecting from the yoke ring. One winding half-branch respectively of a ring-shaped pole winding is situated between the pole rings and the ring web. The winding half-branches in the outer and inner stator each form the pole winding.
International Patent Document WO 88/06375 discloses an electric machine in a transversal flux construction, in which an improvement is provided wherein the pole arrangement has an identical construction on the whole circumference and leakage flux components in the longitudinal direction are avoided. By means of this arrangement the magnetic resistance for the field components is reduced.
International Patent Document WO 95/04399 describes a transversal flux machine, wherein several winding branches are provided in the stator in the form of ring-shaped coils arranged coaxially with respect to the machine axis. These are embedded within sequences of C-shaped soft-iron elements arranged in the circumferential direction. The rotor and the partial rotors consist of permanent magnet elements and flux-guiding soft-iron elements which rotate in groove-type recesses of the soft-iron stator elements.
European Patent Document EP 0 712 199 illustrates a transversal flux machine with a number of outer soft-iron stator elements, with a plurality of inner soft-iron stator elements, one ring winding respectively of the outer and inner stator, and a rotor which, in turn, consists of mutually alternating magnets and soft-iron elements. In the case of this transversal flux machine, the magnets taper from the outside to the inside, and the width of the inner soft-iron stator elements is smaller than the width of the outer soft-iron stator elements.
All of the above-mentioned transversal flux arrangements have the disadvantage that their construction is not sufficiently stable in the transition area from the stator to the rotor. As a result, vibrations caused by the locally constantly changing attraction ratios between the rotating rotor and the stator, undesirable noises are developed. In addition, no optimal cooling is ensured in the case of the above-discussed transversal flux machines. Specifically, in the case of high-power transversal flux machines, noise development may occur which is of such a magnitude that efficiency deteriorates because of the higher conductor resistance and because the machine supplies less power because the magnetic properties deteriorate at higher temperatures. In an extreme case, its operability may even be endangered. In addition, the maximal constant power is lower while the cooling is insufficient.
It is an object of the invention to further develop a transversal flux machine of the aforementioned type, which generates little noise in its operation, so that mechanical stability, efficiency and capacity are increased and a functionally reliable operation can be ensured in the high-power range. In addition, a simple and low-cost manufacturing is permitted.
According to the present invention, this object is achieved by a transversal flux machine wherein, a retaining ring is provided on the stator side in each case between the ring winding and the rotor arrangement. The retaining ring has equidistantly spaced recesses at its two edge areas for receiving teeth of a pole or a pole system which project in the direction of the rotor arrangement.
The retaining ring is used for stabilizing the totality of the pole system and the ring coil so that, during an operation of the transversal flux machine, the individual pole elements move neither in the direction toward the rotor nor parallel thereto. Thus, vibrations are avoided in the stator range which may result in an increased generation of noise.
In addition, the retaining ring provides thermal shielding of the rotor and the stator so that heat generated in the stator arrangement cannot be transmitted unhindered to the rotor.
The intensity of the magnetic flux currents in the rotor—thus in the permanent magnets and the soft-iron reflux elements—depends on the temperature of the permanent magnets. In particular, the magnetic properties deteriorate as the temperatures rise. Starting at defined limit temperatures, the magnetic properties of the permanent magnets are lost completely. The above-mentioned shielding is therefore particularly advantageous in the case of high-power transversal flux machines, in the case of which—at least on the stator side, a high heat development takes place.
In addition, it is possible to cool the retaining ring. In this case, the heat generated in the stator can be carried away in a simple manner, thereby increasing the maximal constant power of the whole arrangement. The shielding between the stator and the rotor is further increased by this measure.
According to an advantageous embodiment, cooling of the retaining ring can be achieved in that at least one cooling duct is constructed in this retaining ring. When a suitable liquid flows through the cooling duct, the heat can be carried away in a simple and efficient manner.
The retaining ring represents an optimal winding carrier for the ring coil but also the pole system so that, overall a compact total unit can be provided which is easy to manufacture.
In a preferred embodiment, the recesses in the retaining rings are constructed to be tapering, for example, essentially conically, in the direction of the rotor arrangement. By means of a complementary construction of the teeth of the pole system received in the recesses, the stability of the overall arrangement, particularly in the direction of the rotor, can be further improved. Furthermore, the induction decreases in the conical teeth. Also, the whole circumference of the machine is available for guiding the flux in the pole yoke. The thickness of the pole yoke in the radial direction is not subjected to any limitation, so that arbitrary values of the induction can be set in the pole yoke. This leads to lower iron losses, which is advantageous in the case of a machine which is to be operated at high frequencies.
According to anot
Bayerische Motoren Werke Aktiengesellschaft
Evenson, McKeown, Edwards & Lenahan P.L.L.C.
Ramirez Nestor
Tamai Karl E.
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