Rotational control device

Details Rotational control device Rotational control device

1992-08-05

1993-08-10

Rosenthal, Arnold

Valves and valve actuation

Electrically actuated valve

Rotary electric actuator

251 65, 25112912, 251368, F16K 3108, H01F 714

Patent

active

052341925

DESCRIPTION:

BRIEF SUMMARY
STATE OF TECHNOLOGY

The invention is based on a rotational control device for setting the angle of regulating elements, in particular on a restricting device used for determining the flow cross-section in a flow line for internal combustion engines.
In a known control device of this type (DE 38 30 114 A1), the two stator poles used to generate the magnetic reset moment in the event of a currentless setting motor are designed asymmetrical with a pole width significantly deviating, one from the other in the circumferential direction. The rotor poles, which are designed as shell shaped magnet segments, are arranged asymmetrically on the rotor and extend in each case circumferentially over an angle greater than 90.degree., in which arrangement the smaller pole width of the stator pole measured on the circumference is approximately equal to the angle over which the rotor poles extend. The stator winding, as a cylindrical coil, embraces a magnetic return path loop which connects the two stator poles with each other. Such a rotational control device involves high manufacturing costs due to the pronounced asymmetry.


ADVANTAGES OF THE INVENTION

In contrast, the control device in accordance with the invention has the advantage of a setting motor of compact construction which is easily manufactured in terms of production technology and in which the magnetic moment is sufficiently large to return the throttle element, in the event of a currentless setting motor, to its starting position which exposes a defined minimum aperture cross-section. The setting motor is robust and has low susceptibility to faults. By operating the stator winding with a direct current with reversible current direction, e.g. via an end stage which can supply both current directions, an adequately sized rotor setting angle is achieved between the closing position of the restricting device, at which the exposed aperture cross-section of the flow line is zero, and the end position of the restricting device, at which the exposed aperture cross-section of the flow line is maximum.
The magnetic engagement on the pole gaps between the two claw poles of the rotor, i.e. its magnetic return moment in the event of a currentless stator winding, can be strengthened by providing arched recesses in the central region of the front face connections of claw poles and ring casing in accordance with a first embodiment of the invention. This results in a reduction of the cross-section in the magnetic return path, so that the ratio of the magnetic resistances in the return path and in transverse direction of the claw poles, which determines the magnitude of the engagement moment, is increased.
The magnetic engagement on the pole gaps can alternatively be strengthened by the air gap under the claw poles being dimensioned in accordance with a preferred embodiment such that the radial air gap width in the central region of the claw poles is larger than in the edge zones of the claw poles, viewed in circumferential direction.
In a preferred embodiment of the invention, the magnet material for the permanent magnet rotor is hard ferrite or plastic bonded ferrite or plastic bonded neodymium iron boron. By comparison with the rare earth magnet material, a substantial reduction of the manufacturing costs is achieved. The rotor may have a cylindrical permanent magnet with diametric magnetisation direction, which accommodates the rotor shaft torsionally rigid in a central axial bore, or is pivoted on a stub axle, or it may have two shell shaped magnet segments which are fixed on a cylindrical carrier which is connected to the rotor shaft. The radial magnetisation direction in the two magnet segments extends in one magnet segment from the outside inwards and extends in the other magnet segment from the inside outwards. The attachment of the permanent magnet or of the permanent magnet segments on the rotor shaft or on the carrier connected with the rotor shaft is in both cases preferably by means of plastic moulding.
A stator design which is simple in terms of production tec

REFERENCES:
patent: 4428558 (1984-01-01), Odogaki et al.
patent: 4647009 (1987-03-01), Idogaki et al.
patent: 4976237 (1990-12-01), Bollinger

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