Spring devices – Resilient shock or vibration absorber – Including energy absorbing means or feature
Patent
1994-11-01
1997-10-14
Ballato, Josie
Spring devices
Resilient shock or vibration absorber
Including energy absorbing means or feature
267218, 248550, H04R 142, F16F 1502, F15B 700
Patent
active
056763530
DESCRIPTION:
BRIEF SUMMARY
FIELD OF THE INVENTION
The present invention relates to an improved electromagnetic actuator for use in vibration cancellation systems.
BACKGROUND OF THE INVENTION
It has been proposed to cancel vibrations in a mechanical system by sensing the vibrations and utilising an electronic control circuit to drive a mechanical actuator in order to apply vibrations to the system which tend to cancel out the original source of vibration. For example, it has been proposed to use a mechanical actuator in association with an engine mount for an internal combustion engine to apply cancelling vibrations to the engine for producing smooth running.
Known actuators are of the moving-iron type, wherein a magnetic field is produced which interacts with a metal armature to generate a force thereon. The armature then moves under the influence of the generated force. A disadvantage of these actuators is that the force generated is non-linear with respect to armature displacement. It is, therefore, an object of the present invention to provide an actuator having more linear characteristics than moving-iron type actuators by employing either a constant or variable volume hydraulic lever.
SUMMARY OF THE INVENTION
According to a first aspect the present invention there is provided an electromagnetic actuator comprising a moving-coil electrical signal-to-displacement transducer and a hydraulic lever wherein the hydraulic lever transforms the transducer output.
According to a second aspect of the present invention there is provided an electromagnetic actuator comprising a rotary electric motor and a hydraulic lever wherein the hydraulic lever transforms the motor output. Preferably, the motor drives an Archimedean screw in order to transfer hydraulic fluid between a hydraulic fluid reservoir and a hydraulic lever working chamber. However, other forms of reversible rotary pump may usefully be employed.
Advantageously, two counter-rotating Archimedean screws may be used in order to balance out stator rotational reaction forces.
Conveniently, the actuator according to the present invention may be employed as an engine mounting as part of a vibration cancellation system.
BRIEF DESCRIPTION OF THE DRAWINGS
Embodiments of the present invention will now be described, by way of example, with reference to the accompanying drawings, in which:
FIG. 1 shows an actuator according to the first aspect of the present invention;
FIG. 2 shows a single screw version of an actuator according to the second aspect of the present invention;
FIG. 3 shows a double screw actuator according to the second aspect of the present invention; and
FIG. 4 shows an active vibration control system applied to an internal combustion engine.
Referring to the FIG. 1, an actuator 1 includes a body 2, formed from an annular permanent magnet 3 having first and second axial extremities 3a, 3b, a disc-shaped first end-piece 4 and a dish-shaped second end-piece 5. The first end-piece has a diameter substantially the same as the outer diameter of the magnet 3 and is affixed coaxially across the first axial extremity 3a thereof. The second end-piece 5 has the same diameter as the first end-piece 4 and is similarly affixed across the second axial extremity 3b of the magnet 3 with its wall portion 5a extending away from the magnet 3.
The second end-piece 5 is provided with an aperture 6 in the centre of its planar portion. A column 7 extends coaxially from the centre of the first end-piece 4 in the direction of the second end-piece 5, passes through the aperture 6 therein.
A first piston 8, comprising a tube having a closed end, supports an energisable coil 9 wound about the tubular portion adjacent the closed end thereof. The first piston 8 is mounted for axial movement relative to the column 7 and is supported by a pair of spiders 10, 11 extending radially inwardly from the inner wall of the magnet 3 such that a portion of the coil 9 is within the aperture 6.
A chamber 12 is defined by the outwardly facing planar surface and the inner surface of the wall portion of the seco
REFERENCES:
patent: 3456755 (1969-07-01), Walker
patent: 5423523 (1995-06-01), Gossman et al.
Jones Owen
Trinder Michael C. J.
Ballato Josie
Noise Cancellation Technologies, Inc.
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