Electricity: magnetically operated switches – magnets – and electr – Magnets and electromagnets – For magnetizing or demagnetizing
Patent
1985-10-21
1988-04-12
Grimley, Arthur T.
Electricity: magnetically operated switches, magnets, and electr
Magnets and electromagnets
For magnetizing or demagnetizing
310 905, 361143, H01F 1300
Patent
active
047377534
DESCRIPTION:
BRIEF SUMMARY
The present invention concerns a multipolar magnetization device for forming on at least one surface of a magnetizable body a series of magnetized zones having successively alternating polarities, comprising at least one source of electric power, at least one current pulse generating device connected to this source, and several elongated portions of electric conductors connected to said pulse generating device and arranged so as to create magnetic fields producing the magnetization of said zones.
In such a device, it is usual to supply the conductors in power from a single current pulse generator, the voltage of which had to be sufficiently high to create the necessary magnetization current.
Such an arrangement presents however major drawbacks when one has to produce on a body of small dimensions, such as a rotor of a stepping motor, a high number of magnetized zones, for example for the purpose of attaining, in the case of such a motor, a high number of steps. As a matter of fact, when the number of zones to magnetize increases for a given volume or surface of the corresponding body, the utilizable copper section and the space available for the insulation of the conductors are reduced accordingly. The result of this is that on the one hand, the problem of the heating of the device becomes very rapidly critical, and that, on the other hand, the permissible working voltage decreases because of the risk of breakdown. Further, in the devices of this type, the homogeneity of the magnetization of the different zones is not satisfactory. As a matter of fact, the portions of conductors producing the respective magnetization fields always exhibit in practice variations in section, therefor of electric resistance, and thus conduct different magnetization currents. The usual power supply, in parallel, of the conductors or groups of conductors does not permit a sufficient homogeneity to be ensured from the moment when it is not possible any more, in particular for reasons of overheating, to saturate the zones to be magnetized by an excess of current. An additional drawback originates from the fact that the usual power supply makes the detection of malfunctioning resulting from a breakdown very difficut, the corresponding variations of the level of current being very small.
The aim of the invention is to remedy the drawbacks and the limitations of known magnetization devices, and in particular to provide a device of the type mentioned at the beginning permitting to magnetize a high number of zones in a reduced space, in a very homogeneous manner.
For this purpose, the device according to the invention is characterized in that said portions of conductors are disposed in such a manner that the magnetization of each zone is produced by the magnetic field generated by at least four portions of conductors connected to at least two distinct pulse generating devices producing approximately equal current pulses.
Other particularities of the invention will become apparent from the description given hereunder and from the appended drawing illustrating an example of realization of the present device.
In the drawing,
FIG. 1 is a diagram of the disposition and of the power supply of the electric conductors of the magnetization device,
FIG. 2 is a schematic transverse cross-sectional view, along the line II--II of FIG. 1, showing the magnetization of a zone of the body to magnetize, and
FIG. 3 is a transverse cross-sectional view of the device in the working state.
The device illustrated in the FIGS. 1 to 3 is intended for the magnetization of a multipolar rotor of a stepping motor, which has the shape of a flat annular disk 1, visible in section in FIG. 2. Elongated portions of conductors, such as 21 to 28, designated as a whole by 2 in FIG. 1, are disposed to be parallel to the disk in the radial direction thereof, so as to produce in the circumferential direction of the disk a series of magnetized zones in the transverse direction, i.e. in the axial direction of the disk.
The magnetization device comprises two annular support pa
REFERENCES:
patent: 3158797 (1964-11-01), Andrews
patent: 3423707 (1969-01-01), Williams
patent: 3624572 (1971-11-01), Mallinson et al.
patent: 3824516 (1974-07-01), Benowitz
patent: 3885839 (1975-05-01), Haberman
Grimley Arthur T.
Lau Jane K.
Portescap
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