Electrical generator or motor structure – Dynamoelectric – Oscillating
Patent
1992-02-12
1995-03-28
Voeltz, Emanuel T.
Electrical generator or motor structure
Dynamoelectric
Oscillating
310231, H02K 706
Patent
active
054020220
DESCRIPTION:
BRIEF SUMMARY
BACKGROUND OF THE INVENTION
The invention relates to a rotary actuator, particularly for controlling a throttle cross-section in a line carrying operating fluid for an internal combustion engine.
An electromagnetic rotary actuator is known comprising an actuator motor having a stator which is fixed with respect to a housing in which the motor is located and a rotatable armature. Either the armature or the stator has opposing permanent magnet segments arranged symmetrically with respect to the axis of rotation. The armature or stator not having the permanent magnet segments has field windings through which current can flow to energize the rotary actuator. A magnetically acting contactless restoring element is also provided located in the field of at least one of the permanent magnets. From JP-GM-GM 60-88044, such a rotary actuator is already known which has a magnetic restoring element which, when the power supply to the motor actuator fails, moves the armature of the rotary actuator into a defined rest position. Apart from the housing-fixed permanent magnets, the known restoring element consists of two further permanent magnets connected to the armature. Due to the small torque gradient in the rest position, this leads to a relatively small restoring force. On the other hand, the maximum torque of the restoring element opposing the control torque is undesirably high.
SUMMARY OF THE INVENTION
It is an object of the present invention to provide an electromagnetic rotary actuator, particularly for throttling an operating fluid flow in an internal combustion engine, which does not have the above-mentioned disadvantages.
This object and others which will be made more apparent hereinafter are attained in an electromagnetic rotary actuator comprising an actuator motor with a stator which is fixed with respect to the housing and a rotatable armature. Either the armature or the stator has opposing permanent magnet segments arranged symmetrically with respect to the axis of rotation of the armature. The armature or stator not having the permanent magnet segments has field windings through which current flows. A magnetically acting contactless restoring element is also provided located in the field of at least one of the permanent magnets.
According to the invention the restoring element consists of a magnetizable or ferromagnetic, but not permanently magnetic, material.
By comparison, the rotary actuator according to the invention, has the advantage that the restoring element has a more advantageous torque characteristic and at the same time a much simplified structure.
Other embodiments of the rotary actuator according to the invention are possible. At least one permanent magnet segment can be axially extended so that the restoring element is located in the magnetic field of the at least one permanent magnet segment axially extended.
The restoring element can comprise a disk which has two spoke-shaped radial continuations on opposite sides of the disk extending radially opposite to each other. Each spoke-shaped radial continuation has two arms extending along an imaginary circular line from an outer end of each of the continuations. Advantageously three of the arms have substantially equal lengths but one arm is a longer or shorter so that the restoring element is unsymmetrical in cross-section. Each continuation can have a flattening or flattened portion in the vicinity of which a distance from the restoring element to the permanent magnet segment is greater than another distance from the restoring element to the permanent magnet segment in the vicinity of one of the arms. The radial width of each of the arms is advantageously less than the thickness of the disk.
In a preferred embodiment of the invention the field windings and the restoring element are arranged on the stator. The armature is cup-shaped and encircles the stator and the permanent magnet segments are arranged in an axially protruding manner on cylindrical walls of the armature. An asymmetrical cross-sectional shape of the restoring element, whic
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patent: 3234436 (1966-02-01), Bieger
patent: 4500861 (1985-02-01), Nelson
patent: 4999531 (1991-03-01), Mavadia et al.
patent: 5087847 (1992-02-01), Giesbert et al.
Patent Abstracts of Japan, vol. 9, No.: 110 (E-314) (1833).
Patent abstracts of Japan. vol. 5, No.: 145 (E-74) (817).
Bertolini Thomas
Herm Werner
Nguyen Matthew
Robert & Bosch GmbH
Striker Michael J.
Voeltz Emanuel T.
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