Electrical machine, especially alternator for motor cars

Details Electrical machine, especially alternator for motor cars Electrical machine, especially alternator for motor cars

1992-02-05

1993-08-03

Stephan, Steven L.

Electrical generator or motor structure

Dynamoelectric

Rotary

310 65, 310254, H02K 720

Patent

active

052332497

DESCRIPTION:

BRIEF SUMMARY
BACKGROUND OF THE INVENTION

The present invention relates to an electrical machine, preferably a three-phase generator for motor vehicles. More particularly, the present invention relates to an electrical machine which has a surface-cooled stator with two stator windings inserted in slots of a stator plate stack.
It is already known from the Japanese Utility Model Publication 57-65570 to provide the stator housing of an electric motor with cooling fins for guiding off heat. These cooling ribs, together with the annular spaces at the winding ends of the stator winding, are filled with a heat conducting mold resin after the stator plate stack has already been inserted into the housing with the stator winding. In so doing, the winding ends are completely embedded in the mold resin so that the heat losses generated in them can be guided outward. A disadvantage of an electrical machine produced in this way consists in that the entire prefabricated stator, including its housing, must be inserted in a press or injection mold for embedding the winding ends in heat conducting plastic, which requires special steps for sealing the injection or press mold. Such a solution becomes even more costly when the electrical machine has two stator plate stacks with stator windings located one after the other in the axial direction and when these systems are inserted into a pot-shaped stator housing in addition.
Such a three-phase generator for motor vehicles having a double-generator system in a closed, water-cooled housing is known (FIG. 5) from DE-OS 31 28 081 (R. 6932, FIGS. 5 to 7). The winding ends of the two systems are exposed. Consequently, due to the relatively poor heat conduction at the winding ends, the output of such an electrical machine is limited and its outer diameter is relatively large. Moreover the two stator plate stacks are inserted into the cylindrical stator housing from both sides, which cannot be realized in a pot-shaped construction of the housing.


SUMMARY OF THE INVENTION

The object of the present invention is to produce and assemble the stator in surface-cooled electrical machines having two stator systems located one after the other in the axial direction with good heat conduction and in a compact construction as inexpensively as possible.
In keeping with these objects and with others which will become apparent hereinafter, one feature of the invention resides, briefly states, in an electrical machine in which two stator plate stacks are positioned so as to be offset relative to one another by half a slot spacing and, together with the winding ends of the stator windings, are embedded in a heat conducting plastic to form a pre-fabricated constructional unit.
The electrical machine according to the invention has the advantage that the two stator systems are manufactured beforehand to form a constructional unit in a press mold by the heat conducting plastic in which the winding ends of the stator windings are embedded. A cylindrical or pot-shaped housing which is likewise manufactured beforehand can then be shrunk on to this constructional unit so that costly press molds or assembly devices can be dispensed with. Since the plastic and the stator plate stacks are located along the surface area of the inner surface of the machine housing, a good heat conduction from the winding ends to the housing is ensured. Another advantage consists in that the ripple of the d.c. voltage is considerably reduced by the stator plate stacks of the two generator systems in a parallel connection of the rectified generator voltages, the stator plate stacks being offset relative to one another by half a slot spacing.
In a particularly advantageous manner a heat conducting spacer ring having recesses, e.g. grooves, at its front sides is inserted as spacing means between the two plate stacks. Projections, e.g. positioning pins, arranged at the facing front sides of the stator plate stacks for the purpose of positioning engage in these grooves. For positioning the stator plate stacks the grooves at one front side of the

REFERENCES:
patent: 1584502 (1926-11-01), Apple
patent: 3758799 (1973-11-01), Dochterman et al.
patent: 3783313 (1974-01-01), Mathur
patent: 4785213 (1988-11-01), Satake
patent: 4920293 (1990-04-01), Kanda
Patent Abstracts of Japan vol. 10, No. 27 (E-378) (2084) 4 Feb. 1986.

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