Electrical generator or motor structure – Non-dynamoelectric – Piezoelectric elements and devices
Patent
1993-04-13
1995-01-03
Budd, Mark O.
Electrical generator or motor structure
Non-dynamoelectric
Piezoelectric elements and devices
H01L 4108
Patent
active
053789482
DESCRIPTION:
BRIEF SUMMARY
FIELD OF THE INVENTION
The invention relates to a method and apparatus for converting mechanical oscillations of electrically driven actuators into mechanical movements.
BACKGROUND TO THE INVENTION
Electromotors which convert electrical into mechanical energy by means of the electromagnetic principle have the disadvantage that there is electrical and mechanical inertia at the rotors.
Actuatorelectric drives in which either an inverted piezoelectric effect on polarized crystals, magnetostrictive effects or the like are used, lead one to expect low inertias. In such cases it is necessary to arrange actuators in series, in order to form a longer stroke from the oscillating travel of the actuators when alternating voltage is applied. Various suggestions have been made in this connection.
One of these suggestions hydraulically converts the slight stroke of an actuator into a longer stroke according to the principle of variable piston surfaces. The disadvantage of this suggestion, however, is that the overall size of the structure is excessive and the hydraulic unit easily begins to leak.
In so-called ultrasound motors, e.g. the rotary control drive described in patent publication EP 0 112 454 B1, the main problem is the mechanical wear at the contact point between piezoelectric crystal actuator and rotor which, in most cases, restricts its life or even makes operation impossible, particularly in small structures.
Low-wear surface coatings and soft intermediate layers were suggested which soften the hard impact of the actuator end on the rotor. However, the problems are not adequately solved with these structures.
The so-called inchworm motor also has disadvantages of this type. Two piezoelectric crystal sleeves are wedged in a round guide shaft, whereby a longitudinal piezoelectric crystal located between them ensures that a corresponding unclamped sleeve is advanced within the shaft. Its operation is quite heavily dependent on the wear between the piezoelectric sleeve and shaft.
It was also suggested that piezoelectric crystals be allowed to radially or angularly strike against a rotor in an oscillating manner. However tangential and radial oscillation amplitudes cannot be cleanly separated even at the control side and, therefore, additional wear results.
The very slight stroke of the actuators is easily offset by play and wear in the mechanical arrangement and the device thus made ineffective. Otherwise, the structure must be made appropriately rigid and precise and is thus expensive.
These problems occur in linear motors, as well as in rotary motors and piezoelectric crystals and also when using other actuators.
An object of the invention is to improve an actuatorelectric motor and its electronic control in such a way that these disadvantages are eliminated.
SUMMARY OF THE INVENTION
In accordance with an embodiment of the invention, in a method for converting mechanical oscillations of electrically driven actuators into mechanical movements, actuators move forward in steps between two elastically prestressed surfaces of an output drive element.
BRIEF INTRODUCTION TO THE DRAWINGS
Embodiments of the invention are described in greater detail below with reference to the following drawings, in which:
FIG. 1 is a section C--C through a linear motor
FIG. 2 is a section B--B through a linear motor
FIG. 3 is a section A--A through a linear motor
FIG. 4 is a detail from a linear motor
FIGS. 5 and 6 are a basic diagram from a linear motor
FIG. 7 is a section D--D through a rotary motor
FIG. 8 is a section E--E through a rotary motor
FIG. 9 is a cut of a rotary motor combined with a drive
FIGS. 10-17 are phase diagrams of a rotary motor
FIGS. 18 and 19 are a frequency diagram of a rotary motor
FIG. 20 is a circuit diagram of control electronics for actors
FIG. 21 is a cut-off diagram
DETAILED DESCRIPTION OF THE INVENTION
In FIGS. 1-6, a cover plate 2 is situated opposite a base plate 1. Both represent the stator of the linear motor and thus a guide rail having any length desired. Armature 6 slides between b
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