Electrical generator or motor structure – Dynamoelectric – Rotary
Reexamination Certificate
1999-09-27
2001-02-20
Ramirez, Nestor (Department: 2834)
Electrical generator or motor structure
Dynamoelectric
Rotary
C310S059000, C310S07500D, C310S057000, C310S053000, C310S054000, C310S061000, C310S062000, C310S063000
Reexamination Certificate
active
06191511
ABSTRACT:
The present invention relates to an asynchronous electric machine, in particular an asynchronous motor, including a rotor within a stator and containing a liquid cooling circuit, the rotor having a hollow shaft in which is incorporated a pump for circulating the liquid.
The invention applies in particular to asynchronous motors for electric traction or hybrid vehicles, these motors having to have a high specific output, be compact and have as few as possible external connectors, in particular for the cooling liquid.
Usually, in motors of this type, the cooling liquid only circulates in the stator, then it is led to an external radiator to be air cooled. This arrangement creates difficulties for the layout of the radiator and the connecting conduits. Moreover, the poorly cooled rotor becomes much hotter than the stator. On the one hand, this increase in temperature forces the designer to limit the supply current, thus the power of the motor, and on the other hand, the difference in temperature between the rotor and stator involves differential expansions which can cause mechanical damage, in particular in the motor bearings.
German Patent Application No. 4020416 describes the incorporation of a pump in a shaft of an electric generator driven by the traction motor of a vehicle. This pump includes a central stationary body with several parallel channels, having a space requirement such that it can only be housed in a shaft of particularly large diameter. The circuit described cools the rotor shaft, but not the stator.
The present invention concerns an asynchronous electric machine, in particular a motor or a generator, whose liquid cooling circuit is arranged so as to avoid to a substantial extent the aforementioned drawbacks.
An asynchronous electric machine according to the invention is therefore characterised in that the liquid circuit is a closed circuit within the machine and passes in the stator and the rotor shaft, substantially over the entire length of the rotor and the entire length of the stator.
One thus obtains a cooling circuit which is completely closed within the motor, requiring neither an external pump, nor connection to an external radiator. The circulation of the liquid successively through the stator and through the rotor guarantees a good temperature balance between these two parts of the motor, thus fewer differential expansions and fewer localised temperature increases, thus allowing a greater specific output and/or a reduction in the motor volume for the same output.
Preferably, the liquid circuit in the stator passes into a cooling chamber where the liquid is in contact with a peripheral casing of the stator, which is provided with outer fins, the circuit then passing into conduits arranged in the support structure of the stator.
This means that the cooling chamber and the peripheral casing of the stator form a water-air heat exchanger, this casing being generally exposed to a strong air current when it is a motor for an electric automobile vehicle, in particular a motor individually coupled to a wheel of the vehicle and situated in the wheel passage.
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Griffin & Szipl, P.C.
Perez Guillermo
Ramirez Nestor
The Swatch Group Management Services AG
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