Electronically commutated DC

Details Electronically commutated DC Electronically commutated DC

1999-09-03

2001-05-15

Mullins, Burton (Department: 2834)

Electrical generator or motor structure

Dynamoelectric

Rotary

C310S114000, C310S112000, C310S090000, C310S268000, C310S254100, C310S091000

Reexamination Certificate

active

06232690

ABSTRACT:

BACKGROUND OF THE INVENTION
The invention relates to an electronically commutated DC motor having an air gap in which a stator coil is arranged and having a first permanent magnet rotor arranged on one side of this air gap. A second permanent magnetic rotor is positioned at the opposite side of the air gap, whereby the second rotor is coaxially arranged to the first rotor without a mechanical connection to the first rotor.
From DE 195 03 521 A1 an electronically commutated drive motor with planar air gap having a fan wheel connected to the rotor is known. Such motors are relatively inexpensive because of their simple construction and are therefore used, among other applications, also in the interior of motor vehicles. However, a certain noise level may not be surpassed in these situations. It is therefore important that the rotor of the fan wheel will not begin to vibrate as a result of the occurring driving accelerations but remains secured within its guide bearing. The required axial force is provided by magnetic coupling between the rotor magnet and the steel disk positioned within the stator. A disadvantage is that eddy currents will result which decrease the efficiency of the motor and indirectly increase the running noise level. A further disadvantage of such disk rotor motors is that, in general, electromagnetically caused axial reaction forces result which may cause the entire system to vibrate.
It is an object of the invention to provide an electric motor of the aforementioned kind which has an even more reduced noise level at acceptable costs.
SUMMARY OF THE INVENTION
Inventively, the DC motor has a housing having an air gap and a stator coil is positioned in the air gap. A first permanent magnet rotor and a second permanent magnet rotor are coaxially arranged to one another in the housing on opposite sides of the air gap. The first and second permanent magnet rotors are mounted in the housing without being mechanically connected to one another.
In another embodiment, a flat stator coil is provided. At least one permanent magnet rotor comprises an axially magnetized annular rotor magnet, a plastic part as a support for the rotor magnet, a shaft mounted in the plastic part, and a soft magnetic ground element mounted by a snap connection on the plastic part. The rotor magnet is fastened to the soft magnetic ground element.
In another embodiment, a housing having a first cup-shaped housing part and a second cup-shaped housing part, is provided. The first housing part has a first bottom and the second housing part has a second bottom. The first and second bottoms face one another and are spaced from one another to form an air gap. A flat stator coil is positioned in the air gap.
In yet another embodiment, a stator support with an air gap is provided A stator coil is wound onto the stator support within the air gap. An axle is mounted centrally in the stator support. A first permanent magnet rotor and a second permanent magnet rotor are coaxially arranged to one another on opposite sides of the air gap. The first and second permanent magnet rotors are mounted without being mechanically connected to one another.


REFERENCES:
patent: 3526795 (1970-09-01), Pecs
patent: 4644207 (1987-02-01), Catterfeld et al.
patent: 5245238 (1993-09-01), Lynch et al.
patent: 436 550 (1967-11-01), None
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patent: Gm 76 01 853 (1976-05-01), None
patent: 40 42 432 (1993-08-01), None
patent: 44 21 855 (1996-01-01), None
patent: 0 548 362 (1997-09-01), None
patent: WO 97/47068 (1997-12-01), None
patent: 0 814 269 (1997-12-01), None
patent: 53-126110 (1978-11-01), None
patent: 55-63493 (1982-01-01), None
Patent Abstracts of Japan JP 59 172961 Sep. 29, 1984.

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