Electricity: magnetically operated switches – magnets – and electr – Magnets and electromagnets – With magneto-mechanical motive device
Patent
1998-10-02
2000-09-26
Gellner, Michael L.
Electricity: magnetically operated switches, magnets, and electr
Magnets and electromagnets
With magneto-mechanical motive device
310 85, 310152, 324146, G01R 120, H01F 708
Patent
active
06124774&
DESCRIPTION:
BRIEF SUMMARY
BACKGROUND OF THE INVENTION
1. Field of the Invention
The present invention relates to the field of electromagnetically controlled drive devices, in particular devices known as "ratio meters".
A particular application for the present invention lies with indicator dials for the dashboards of motor vehicles.
2. Prior Art
It is known that in general a ratio meter comprises: defined by said coils; to receive the hub of a dial needle; and
The control coils are generally carried by a support frame made of plastics material.
The direction in which the needle points depends on the resultant of the magnetic fields created by the two coils.
Thus, if the two coils are fed with signals representing the sine/cosine or the tangent of an input magnitude, then the angle taken up by the magnet relative to a reference position is directly representative of said input magnitude.
Until now, the magnetic shielding has usually been provided in the form of a cylindrical metal bell.
Also until now, the rest position of the moving equipment of such an electromagnetically controlled drive has been set by adding auxiliary magnets or springs, thereby leading to structures that are complex. Document DE-A-3 541 395 describes magnetic shielding formed by a spiral winding of metal foil.
Document GB-A-564 181 describes an indicator having a magnet and a coil and including two screws located inside external shielding and suitable for being adjusted to set the rest position of the device.
SUMMARY OF THE INVENTION
The present invention now seeks to improve known electromagnetically controlled drives.
According to the present invention, this object is achieved by an electromagnetically controlled drive device which comprises: control coils (10, 20); and support frame, at least in part, is made by stamping a sheet of soft magnetic metal, comprises an annular skirt (110) that is not a circular cylinder.
According to an advantageous characteristic of the present invention, the shielding comprises an annular skirt that is generally a circular cylinder, but that possesses at least one re-entrant shape that is reentrant relative to the circular cylinder.
In a variant, two shapes that are re-entrant relative to the circular cylinder are provided in this way. These re-entrant shapes can comprise planes. Nevertheless, the re-entrant shapes may be of different geometry. The two re-entrant shapes may be diametrically opposite about the axis of the device. However in certain variants, these two re-entrant shapes are on the contrary not diametrically opposite.
According to an advantageous characteristic of the invention, the shielding comprises an annular skirt that is not a circular cylinder and that possesses two orthogonal planes of symmetry intersecting on the axis of rotation of the equipment.
In another variant of the invention, the annular skirt of the shielding is generally in the form of an ellipse.
According to another advantageous characteristic of the invention, the annular skirt comprises two diametrically-opposite sectors of a circular cylinder interconnected by two parallel planes.
The invention, together with the objects and advantages thereof, may best be understood by reference to the following detailed description with reference to the accompanying drawings given by way of non-limiting example, and in which:
BRIEF DESCRIPTION OF THE DRAWINGS
FIG. 1 is an axial plane view of a support frame for a ratio meter in accordance with the present invention;
FIG. 2 is an end view of magnetic shielding in accordance with the present invention;
FIG. 3 is a first section view through the shielding on a section plane referenced III--III in FIG. 2;
FIG. 4 is a second section view through the same shielding on a section plane referenced IV--IV in FIG. 3; and
FIG. 5 is a diagrammatic exploded view of a ratio meter in accordance with the present invention.
The general internal structure of the ratio meter comprising coils 10, 20, a magnet 200, and a needle-carrying shaft 210 is known per se and is not described in detail below.
The two coils 10, 2
REFERENCES:
patent: 5275141 (1994-01-01), Tsunoda et al.
patent: 5578918 (1996-11-01), Baatz
Barrera Raymond
Gellner Michael L.
Magneti Marelli France
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