Electrical generator or motor structure – Dynamoelectric – Reciprocating
Patent
1994-06-30
1996-09-24
Dougherty, Thomas M.
Electrical generator or motor structure
Dynamoelectric
Reciprocating
310 15, 360104, H02K 3312
Patent
active
055593780
DESCRIPTION:
BRIEF SUMMARY
BACKGROUND OF THE INVENTION
1. Field of the Invention
The present invention concerns an electromagnetic actuator of the type which generates a force resulting from substantially-constant current over the entire functional course of travel and which generates a reduced force in the absence of current, this actuator including a stator structure having two components, of which at least one incorporates three stator poles, and of a device which is movable in translational motion comprising two pairs of poles corresponding to two thin magnets magnetized in opposite directions; it further concerns the manufacture of pneumatic distributing devices utilizing these actuators.
2. Discussion of the Background
The general concept of such actuators, which can be produced incorporating plane or axial symmetry, are known in prior art.
In particular, the Applicant holds French Patent No. 89/08051, which discloses a single-phased electromagnetic actuator taking up little space. The actuators described in this patent are designed, in particular, for control of hard disk reading and writing heads or the actuation of plotting table pens. In these cases, a low electric time constant is sought.
For applications in which a strong force generated by electric power applied to the coil is sought, these three stator-pole actuators known according to prior art exhibit disadvantages. Indeed, when the width of the three poles match the course of travel of the rotor, the space available for housing the copper wire belonging to the electric trip coil may prove to be insufficient.
One may certainly increase the width of the poles beyond the dimension required for the expected course of travel of the rotor. In this case, it is also necessary to increase the width of the stator poles, a step which increases the cost price, since the high-quality magnetic materials used to produce the high-performance thin magnets are expensive.
Prior art further encompasses suggestions for producing multi-stage actuators having 2N+1 stator poles and 2N pairs of rotor poles, or 2N+1 pairs of rotor poles and 2N stator poles. However, in addition to the high cost of these actuators, these devices take up large amounts of space.
SUMMARY OF THE INVENTION
The object of the present invention is to remedy these difficulties by proposing an electromagnetic actuator incorporating three stator poles and two pairs of rotor poles of such a nature as to generate a force by means of significant applied electric power and having optimal space requirements. More especially, the invention concerns an actuator of the linear type or incorporating axial geometry, including a stator structure having two stator elements. One of the stator elements has a central pole whose length Y.sub.C is greater than, or equal to, the course of travel Y of the rotor component, increased by a length substantially equal to the length E of the air gap. The length Y.sub.L of the lateral poles is determined solely by the volume required for housing the electric trip coil, whose characteristics are calculated as a function of the required force generated by applied electric current, on the one hand, and of the thickness Z of this coil, on the other. The length Y.sub.L is greater than the length Y.sub.C of the central stator pole.
Contrary to current teachings in the field, the three-pole actuator according to the invention incorporates one central pole and two lateral poles of different sizes. This embodiment, which the specialist finds surprising, nevertheless makes it possible to maintain satisfactory performance levels, while making possible the housing of a coil incorporating a large volume of copper. It further makes it possible to limit the lateral space requirement, and, accordingly, to allow adaptation of the device to the constraints made obligatory in numerous applications.
The preferred ratio between the thickness of the coil as measured in the plane perpendicular to the thin magnet and the length of Y.sub.cu of the coil as measured along the axis of travel of the mobile element is les
REFERENCES:
patent: 5013223 (1991-05-01), Takahashi et al.
patent: 5136194 (1992-08-01), Oudet et al.
Gandel Pierre
Oudet Claude
Dougherty Thomas M.
Jones Judson H.
Moving Magnet Technologies (S.A.)
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