Electrical generator or motor structure – Non-dynamoelectric – Piezoelectric elements and devices
Patent
1993-07-07
1995-01-17
Budd, Mark O.
Electrical generator or motor structure
Non-dynamoelectric
Piezoelectric elements and devices
310323, 310 26, H01L 4108
Patent
active
053828631
DESCRIPTION:
BRIEF SUMMARY
The present invention relates to a method and a device for causing a first body, which is held in engagement with a second body, to move therealong, said second body being composed of or consisting of materials which due to magnetostrictive, electrostrictive or piezoelectrical action may be caused to undergo a dimensional change across the intended movement direction.
It is previously known to use the material deformations obtained in materials of the kind mentioned initially under the influence of a magnetic or an electric field, in order to bring about a movement of a mechanical element, e.g. in electrical contact means, in printers or in step motors, adjusting motors etc. For use in motors it has proved to be advantageous to use magnetostrictive materials, and particularly so called giant magnetostrictive materials, i.g. materials consisting of an alloy between rare earth metals and magnetic transition metals. The largest magnetostriction known so far has been established within this group of alloys, i.g. the property of undergoing, under the influence of a magnetic field, a dimensional change corresponding to the magnitude of the magnetic field. All those motor constructions are characteristic in that the material deformation generated by magnetic or electric influence in a repeated manner is transformed into an outer mechanical movement. This generally results in motor constructions with a relatively low movement velocity, linear or rotating.
A motor construction of this kind which per se is excellent is described in the international publications WO 88/05618 and WO 90/07821. In one embodiment described in one of said applications, a giant magnetostrictive rod (Terfenol rod) is by shrinking fixed within a tube. By actuating a partial zone of the rod from one end thereof to the other under the influence of a magnetic field which is movable along said rod, the giant magnetostrictive rod is caused to move stepwise along the tube. The step dimension corresponds to the axial elongation caused within the actuated zone. A typical dimension of this elongation is about 10 .mu.m. Each of said steps requires a zone displacement along the entire length of the giant magnetostrictive rod. The zone displacement can take place with a very high velocity and is in principle limited by the elastic wave velocity of the material, which for the giant magnetostrictive material which is called Terfenol amounts to about 1700 m/s. Since each step requires a zone displacement along the entire length of the rod, the resulting movement velocity of the motor is substantially lower than the movement velocity of said zone.
The object of the present invention is to provide a method and a device in which materials of the kind mentioned initially are used to cause a first body, which is held in engagement with a second body of said material, to move along said body, and thereby bring about a motor allowing very fast and at the same time exact movements, linear or rotating, and which has high velocity and acceleration performances and renders possible a good positional control and rigid and exact position adjustment characteristics.
The object mentioned above is obtained by giving the method and the device according to the invention the characteristic features specified in the appended claims.
The invention is described below with reference to schematical examples of embodiments illustrated in the appended drawings, in which
FIG. 1 and 2 schematically illustrate the principal mechanical construction of a motor variant according to the invention with a sliding movement between the fixed and the movable part of fluid motor,
FIG. 3 schematically illustrates the power transmission between the movable and the fixed part of the motor according to FIGS. 1 and 2,
FIG. 4 schematically illustrates a motor variant according to the invention, with rolling movement between the fixed and the movable part of said motor,
FIG. 5 schematically shows an embodiment including a plane rod of magnetostrictive material cooperating with a pair of interconnected
REFERENCES:
patent: 3389274 (1968-06-01), Robertson
patent: 3649856 (1972-03-01), O'Neill
patent: 4454441 (1984-06-01), Taniguchi
Budd Mark O.
DSP Holdings Ltd.
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