DE4408618B4 - Adjustment drive made of bimorph elements - Google Patents

Abstract

Adjustment device with piezo drive, in particular for precision mechanical optical devices, consisting of at least one piezo oscillator, which undergoes a change in length due to the application of differently controlled electrical voltages and alternately comes into operative connection via its free end with an output element (10, 100) in such a way that, when there is an active connection, motion is transmitted takes place on the output element, whereas, when the operative connection is broken, the piezo oscillator in the area of its free end is reset to prepare for the next movement transmission, so that the output element carries out the adjustment movement in the desired direction, the piezo oscillator having two actuators, which are in parallel directly next to one another and in Drive direction arranged one behind the other form a bimorph element (1, 6 - 9, 16 - 19, 21 - 28, 41 - 46, 51 - 56), the two actuators extend approximately perpendicular to the desired direction of movement and electrically decoupled from one another and can be controlled separately, such that, using a different expansion of the two actuators of the piezo oscillator, their bending and thus a path curve in longitudinal and ...

Description

The invention relates to an adjusting device a piezo drive, in particular for precision mechanical optical devices and the like, consisting of at least one piezo transducer, which by applying differently controlled electrical voltages a change in length learns and take turns its free end comes into operative connection with an output element such that with existing Active connection a transmission of movement takes place on the output element, whereas when the operative connection is removed the piezo oscillator in the area of its free end a provision for Preparing the next motion transmission experience, so that Output element performs the adjustment movement in the desired direction, according to the generic term of claim 1.

Known adjustment devices Piezo oscillators are, for example, the so-called micro-impact drives: Here, a piezo oscillator is attached on one side while it with its free end at an angle pressed against a rotor becomes. Now the piezo oscillator with a high-frequency AC voltage excited, which is in the range of the resonance frequency of the vibrator, so leads the transducer standing longitudinal and bending vibrations. This has the creation of an ellipse-like one Swinging movement of the free end of the oscillator relative to the rotor results in the sliding friction forces Rotation of the rotor causes. Moved by the wedging effect the rotor moves forward whereas the oscillating end slides along the rotor during its backward movement or takes off.

This type of micro-impulse drive However, it is only able to drive the rotor in one direction. To get a reversible drive, you need another piezo oscillator provide that engages in the opposite direction on the rotor, whereby each one piezo oscillator out of active connection with the Rotor must be located if one move according to the driving direction of the other Piezo vibrator should be generated.

The micro-impulse drives mentioned have a big one though Disadvantage because the piezo oscillators used have a high frequency AC voltage in the ultrasonic range must be excited in order standing longitudinal and to generate bending vibrations that only work with the Microburst drives enable. A simple longitudinal vibration, how it would be generated with quasi-static voltage application, could not to drive, but only to move the Rotors in the order of magnitude the change in length of the piezo oscillator. Because of the high-frequency AC voltage applied, such are Drives only as endurance runners or with burst control for replacement of focal lengths from a few 10 to 100 nm to use. Exactly Positioning, as is particularly the case with precision mechanical and optical devices would be required is in any case not possible with this, since with a resonating oscillator neither a precisely defined one Adjustment feasible the exact point of attack between the rotor and vibrator is still defined can be and for the rest It is unclear whether and how the rotor rotates during the return movement of the vibrator advanced.

From the U.S. Patent 4,742,260 A piezoelectric drive is previously known, where each piezo oscillator has at least two actuators which are firmly connected to form a bimorph element and which extend approximately perpendicular to the desired direction of movement, are electrically decoupled from one another and can be controlled separately. The elements there are reset by actively lifting them off the drive element.

The JP 03-261379 A (Patnet Abstacts of Japan) Affects a group of piezo oscillators, with each oscillator in the group gradually making a certain movement there.

Piezo oscillator drive devices, also with a change of direction in motion, are also out of the question DE 35 18 055 C2 , the DE 14 88 698 A1 and the U.S. Patent 4,613,782 refer to.

With the generic teaching after DE 41 33 108 A1 is assumed to be an electric rotary or linear motor, the rotor of which is driven by piezoelectric means generating ultrasonic vibrations. A bimorph element is provided there as an actuator. The known piezoelectric motor enables a bidirectional drive by executing an elliptical movement alone with a contact point of a bimorph element, which makes it possible during the contact time to advance a runner in one direction of movement in the desired direction and then again without contact with the runner to return to the starting point. The bimorph element according to DE 41 33 103 A1 is formed from two piezoelectric strips that have corresponding electrodes. The rotor of the known motor is always contacted and dragged by friction when the length of the bender becomes large, since the desired contact with the rotor then arises in order to achieve the desired feed in a certain direction.

From the above, it is therefore an object of the invention to provide a further developed adjustment device with a piezo drive, in particular using bimorph elements, which in particular ders is inexpensive to manufacture and a simple electrical control is possible.

The solution to the problem of the invention takes place with the combination of features of claim 1, wherein the subclaims expedient configurations and represent further training.

Overall, there is the advantage that this Bimorph element also well below the resonance frequency, so in the quasi-static frequency range not only movements in the longitudinal direction, but can also perform in the transverse direction, for example the cut one actuator with simultaneous extension of the neighboring actuator due to the fixed connection of the actuators to a lateral deflection of the free end of the bimorph element leads to the side on which the shortened actuator is located located. It follows that at accordingly controlled voltage application of the actuators free end of the bimorph element a movement in two coordinate directions, for example, an elliptical movement can be forced. Here will the upper area of such an elliptical curve curve is used to the transmission of motion in the desired one Direction to perform during the lower area, where the active connection between the bimorph element and output element is lifted for the provision in preparation the next motion transmission is being used.

An effective drive behavior results when the voltage profiles of the two actuators are one Bimorph element out of phase by about 90 ° are and the two actuators are subjected to an approximately sawtooth-shaped alternating voltage be so that one if possible smooth propulsion movement results.

At least two bimorph elements are expedient provided so that both alternately for the motion transmission worry while each the bimorph element, which is located in the lower end with its free end Area of the respective curve is located, is reset. So that is ensured that the Output element during the reset of the Bimorph element does not perform an undefined movement, but continue in the desired Direction is moved, i.e. twice the distance covered per time.

Become two groups of bimorph elements used, let the pressure of the piezo drive on the output element and also further improve positioning accuracy. Here are the two groups expediently each connected in parallel, i.e. side by side or one behind the other arranged bimorph elements are as uniform as possible in groups divided with the same voltage curves.

It is useful that the bimorph elements are connected to a controller that connects the active connection of a only then lifts each bimorph element with the output element, after the operative connection of the output element with the other Bimorph element is made. This ensures that the critical When the drive is changed, the output element is still securely clamped is present, whereby the delivery accuracy is improved.

It is particularly advantageous if the adjustment movements of the bimorph elements overlap, which is indicated by suitable Voltage curves, achieved, for example, by applying a sawtooth AC voltage can be. This gives to avoid a continuous drive without interrupting the flow of power of the disadvantage that the desired Adjustment movement of the output element to reset a bimorph element must be interrupted.

Also adding more bimorph element groups has a positive effect on the drive behavior. As the best constellation has the arrangement of two or more pairs of bimorph elements emphasized, the corresponding actuators of the pairs connected in parallel, but all four actuators of a pair are subjected to offset voltage profiles are.

In everyone, not just in the ideal It is advantageous if the bimorph elements have the same, temporally offset voltage profiles be charged.

For the above mentioned areas of application the voltage acting on the bimorph elements has a frequency, which is in particular below the ultrasound frequency range. Due to the avoidance of resonance vibrations of the bimorph elements is a resolution of the feed movements possible down to the lower nanometer range. however the scope of the present invention should not now exclusively on limit the frequency range mentioned, since excitation in the ultrasound range for delivery movements makes sense at high speeds and here the voltage amplitude for example ten times higher or a voltage lower by a factor of 10 is required. Because about that in addition, the phase shift in the resonance range is 90 ° is sufficient it here, the one electrode of the bimorph element accordingly to control, the other electrode each automatically. around Lags 90 °.

In principle, the bimorph element can come into operative connection with the output element either via its end face, via a side surface or via an intermediate member connected to the bimorph element. Gripping the end face of the bimorph element is particularly advisable if it is used as a drive, as described above. On the other hand, however, the bimorph element can also be used as a self-running device instead of as a drive element. The bimorph element can move according to the adjustment movements on a stationary base, which is a kinemati reverse to the drive described above.

Was when used as a drive the trajectory is still parallel to the longitudinal extent of the bimorph elements, so it is useful when used as a self-running, over a side surface of the bimorph elements in operative connection with the output element, that is, with the Document. As a result, a more stable edition of the Runner consisting of several bimorph elements on the base and also a lower overall height of the runner reached. Of course, the side surfaces are covered especially in the area of the free end of the bimorph elements, because there the adjustment movement is greatest.

For use as a no-brainer it is particularly advantageous if a bimorph element is used with the two forming actuators, a further pair of actuators is firmly connected, wherein the two actuator pairs are next to each other and in cross-section seen should form a square arrangement. This will both lifting off the stationary base, which is used to prepare the Provision of the respective bimorph element is necessary as well as a perpendicular adjustment movement achieved because the four actuators combined to form a double bimorph element by corresponding ones Voltage application can be coordinated with one another as desired.

However, such double bimorph elements not as a sure-fire success, but used as drives, they allow an adjustment movement in the second dimension of the output element level. This is done removing the active connection as with the drives described above by shortening the double bimorph elements.

In any case, it is useful when used both as a drive and as a self-runner if the free ends of the bimorph elements, which come into operative connection with the output element or with the base, are evenly distributed over the latter in order to create a stable support , In the self-running, this is achieved in particular by a double comb arrangement of double bimorph elements parallel to one another, as described in 4 is shown.

This double arrangement can be expanded in this way if at least two additional bimorph elements are provided be in the same plane but perpendicular to the first Bimorph elements extend and are also parallel to each other. Daßei there is the additional Advantage that a Movement in the second dimension and thus even any level Circular and curve movements possible are.

While in the above, used as runners Bimorph elements, their weight for a constant pressing of the bimorph elements the bottom, it is particularly useful with the piezo drives that they by at least one spring element in operative connection with the output element are feasible and the operative connection of each bimorph element Stress can be canceled. This gives the advantage that due of permanent pressure the spring element securely clamps the output element guaranteed at all times is, so always at least one bimorph element in operative connection with the output element. The active connection is removed through the respective bimorph element itself, making inevitable Path differences no longer adversely affect the quality of the clamping can impact. Because only the relative paths and not the absolute length differences the bimorph elements are relevant for clamping or lifting, thus have length fluctuations none of the bimorph elements due to temperature, aging and environmental influences Influence on a reliable Operating behavior of the piezo drive. The bimorph elements can therefore with low precision requirements and therefore cheaper getting produced.

To bring about the active connection between On the one hand there is the possibility of bimorph element and output element that this Spring element: acts on the output element; on the other hand can the spring element instead act on the bimorph elements, it being particularly advantageous to have them on a common one Mount base. This ensures that always the longer one at the moment Bimorph element guarantees the active connection, while the shorter bimorph element its provision carry out can.

According to the common basis formed in that at Bimorph elements made of piezoceramic by comb-like sawing out individual ones Comb teeth are made from a piezoceramic plate, whereby the comb web extending perpendicular to the tines as a common Basis maintains the connection between the bimorph elements. in this connection the individual actuators are manufactured in such a way that the electrical decoupled from each other and separately controllable electrodes the piezoceramic are evaporated, expediently - as already mentioned - each equivalent bimorph elements are connected in parallel.

Another advantage is if the piezoceramic of the bimorph elements from many thin layers is formed. Through such multilayer bimorph elements that are in the thickness direction are layered, the required excitation voltage is reduced from, for example, 500 V to 1000 V by a factor of 10 to 50 V to 100 V, which considerably increases the areas of application for such drives.

But it is also beyond that possible that the Bimorph elements made of electro- or magnetostrictive instead of piezoceramic Material.

Other advantages and features of present invention result from the following description of embodiments based on the drawings; show here

1a the movement of a bimorph element in front view;

1b the course of the excitation voltage with which the bimorph element as 1a is acted upon;

2a an adjustment drive consisting of four bimorph elements in front view;

2 B the actuator 2a in side view;

2c the actuator 2a in top view;

2d the output element and the path curves of the adjusting device acting on it 2a in a sectional front view;

3a an adjustment drive similar to the adjustment drive 2a , however, the bimorph elements each have four actuators;

3b the actuator 3a in side view;

3c the actuator 3a in top view;

3d a sketch of the mode of operation and the trajectory of the adjustment drive 3a ;

4 an alternative design of the adjustment drive 3a in double comb arrangement and

5 another design of the adjustment drive 3a in a four-way arrangement.

1a shows a bimorph element 1 in four movement situations No. 1 to No. 4. On the bimorph element consisting of a one-piece piezoceramic 1 are two electrodes 2 and 3 evaporated to form piezo actuators which are electrically decoupled from one another and can be controlled separately by voltage sources A and B. Piezo actuators have the property of changing their length when a voltage is applied, i.e. if one end of an actuator is held firmly, a change in voltage causes the free end of the actuator to move in the longitudinal direction.

But since both actuators or electrodes 2 and 3 are firmly connected, a one-sided voltage change on an electrode leads to a bending of the free end in the transverse direction, namely in the direction of the currently shorter actuator. In this way it is due to the corresponding application of voltage to the two electrodes 2 and 3 possible, the free end of the bimorph element 1 Forcing movements in the longitudinal and transverse directions, for example in the form of in 1a shown elliptical orbit curve, which is described by the center of the free end and by the in 1b shown voltage curves A (t) and B (t) was generated.

Here is the electrode 2 with the voltage source A and the electrode 3 connected to the voltage source B. Out 1b the two voltage values at the time of the four movement sections No. 1 to No. 4 can also be read.

It is now easy to see that at least two bimorph elements arranged side by side and driven in opposite directions the upper area of the elliptical Path curve for transmission the adjustment movement can be used while the lower ellipse area at by the neighboring higher Bimorph element active link between bimorph element and Output element for a reset of the free end can be used.

The in the 2a to 2c adjusting device shown in different views 5 consists of bimorph elements 6 . 7 . 8th and 9 , which each have two actuators. The bimorph elements 6 to 9 are made by comb-like sawing out individual comb teeth from a piezoceramic plate, leaving a common base 11 formed in the form of a ridge, whereupon the individual electrodes on one side of the ceramic plate and on the back of each bimorph element each have a neutral conductor 63 . 73 . 83 and 93 get evaporated.

The four bimorph elements 6 to 9 are electrically coupled so that every fourth electrode, that is, the electrodes of every second bimorph element, are connected to one another. So is the electrode connected to the power supply C. 61 with the electrode 81 connected, the electrode connected to the voltage supply D. 62 to the electrode 82 etc. This ensures that the bimorph elements 6 and 8th on the one hand and the bimorph elements 7 and 9 on the other hand, move in the same way and in synchronism. Accordingly, the respective centers of the free ends of the bimorph elements describe the in 2d shown elliptical trajectory (clockwise movement) and thus transfer the desired adjustment movement to an output element 10 (Movement in 2d to the right).

As can be seen from the trajectory, it is for an effective attack on the bimorph elements 6 to 9 on the output element 10 Particularly useful if either the output element in the direction of the adjusting device by a spring, not shown 5 or this in the direction of the output element 10 are pressed, thereby ensuring a permanent operative connection with the output element.

In 2c is again shown in plan view, like the respective electrodes of the bimorph elements 6 to 9 are connected to the respective voltage supply C, D, E and F, while the rear sides of the bimorph elements on which the neutral layers are 63 . 73 . 83 and 91 are evaporated, connected.

In the 3a to 3c is another adjustment device 15 Darge in different views puts out on a common basis 12 arranged bimorph elements 16 . 17 . 18 and 19 consists of four electrodes each 161 to 164 . 171 to 174 . 181 to 184 and 191 to 194 are evaporated. The additional electrode pairs which are connected to voltage sources K, L, M and N separated from voltage sources G, N, I and J of the first electrode pairs now make it possible, for example the electrodes 161 and 162 to act in the same direction while the electrodes 163 and 164 are excited with a phase-shifted voltage, causing a bending of the bimorph element 16 in the thickness direction (i.e. in 3c up / down) can be generated. This movement is particularly in the in 3d shown attack conditions required, the adjusting device 15 to a document 100 extends in parallel and runs along it, that is to say the adjustment movement does not produce a transmission of motion to the output element, but rather the adjustment device 15 moves in the desired direction, although the electrical connections must be carried when the adjustment device is moved, but a remote control, albeit a technically complex one, would also be conceivable.

The one in the 3a to 3c shown actuator 15 is particularly improved in that the number of bimorph elements is doubled and additional bimorph elements 25 . 26 . 27 and 28 symmetrical to a ridge 29 extend opposite to bimorph elements 21 to 24, which are the bimorph elements 16 to 19 out 3 correspond. Such an adjustment device 30 , who also works as a runner, is in 4 shown. There is also the lateral deflection of the bimorph elements, which are evenly divided into two groups 21 to 28 recognizable. As with the adjustment device 15 out 3 Here too, the voltage applied to the respective bimorph elements must be coordinated so that both a movement of the free ends of the bimorph elements in the transverse direction - which produces the adjustment movement - and a movement of the ends in the thickness direction - which serves to establish and remove the operative connection - are carried out can.

In 5 after all is an adjuster 50 shown the two groups of bimorph elements 41 to 46 and 51 to 56 has, wherein the bimorph elements 41 to 46 each run parallel to one another, but their direction of extension is perpendicular to the bimorph elements, which also run parallel to one another 51 to 56 is. Such an arrangement has the great advantage that not only moving in one direction - as is the case with the runner 30 out 4 the case is - but rather a movement in a second coordinate direction and thus all types of movements in a plane parallel to the respective contact surface are possible. Accordingly, with such a runner 50 not only straight movements perpendicular to each other, but also any curve movements can be carried out.

For it makes sense to use all adjustment devices or runners instead a solid piezoceramic plate a multilayer structure made up of many thin Ceramic layers to use: While with the plate shape with usually 1 mm thickness in one embodiment 500 to 1000 volts required are reduced accordingly in the case of a structure composed of a large number thinner Layers the needed Tension about a factor of 10. For example, for the elliptical trajectories, that result from such stress and from free end of a bimorph element are described, a stroke difference of about 1.5 μm and a lateral deflection difference - used for the infeed movement will - from 10 μm listed.

Claims (12)

Adjustment device with piezo drive, in particular for fine mechanical optical devices, consisting of at least one piezo oscillator, which experiences a change in length due to the application of differently controlled electrical voltages and alternately via its free end with an output element ( 10 . 100 ) comes into operative connection in such a way that when there is an active connection there is a movement transmission to the output element, whereas when the active connection is released, the piezo oscillator in the area of its free end is reset to prepare for the next movement transmission, so that the output element carries out the adjustment movement in the desired direction, whereby the piezo oscillator has two actuators, which are arranged in parallel next to each other and one behind the other in the drive direction a bimorph element ( 1 . 6 - 9 . 16 - 19 . 21 - 28 . 41 - 46 . 51 - 56 ) form, the two actuators extend approximately perpendicular to the desired direction of movement and are electrically decoupled from one another and can be controlled separately, such that, using a different expansion of the two actuators of the piezo oscillator, their bending and thus a trajectory in the longitudinal and transverse directions of the bimorph element are generated, the resetting takes place actively while lifting off the driven element, characterized in that the bimorph element consists of a one-tier piezoceramic or a multilayer piezoceramic, two electrically running electrodes (running parallel) running on one side of the ceramic common to the two actuators ( 2 . 3 ; 61 . 62 ; ...; 91 . 92 ; 161 . 162 ; ...; 191 . 192 ) and on the opposite side of the ceramic either a neutral electrode ( 63 . 73 . 83 . 93 ) or another pair of electrodes ( 163 . 164 ; ...; 193 . 194 ) have evaporated. Adjusting device according to claim 1, characterized in that the voltage profiles at the respective electrodes of the two actuators of a bimorph element ( 1 . 6 - 9 . 16 - 19 . 21 - 28 . 41 - 46 . 51 - 56 ) are out of phase by about 90 °. Adjusting device according to claim 1, characterized in that several bimorph elements ( 6 - 9 . 16 - 19 . 21 - 28 . 41 - 46 . 51 - 56 ) are provided, some of which alternately transfer the movement to the output element ( 10 . 100 ) and the other part carries out the reset. Adjusting device according to claim 1, characterized in that the bimorph elements ( 6 - 9 . 16 - 19 . 21 - 28 . 41 - 46 . 51 - 56 ) are connected to a controller that connects the active connection of each bimorph element with the output element ( 10 . 100 ) is only canceled after the operative connection of the output element to the other bimorph element has been established. Adjusting device according to claim 1, characterized in that that the Bimorph elements are subjected to the same, temporally staggered voltage profiles (A - B, C - F, G - J, K - N) are. Adjusting device according to claim 1, characterized in that that the voltages acting on the bimorph elements have a frequency, enable quasi-static operation and can be below the ultrasonic frequency range. Adjusting device according to claim 1, characterized in that the bimorph elements are operatively connected via their end faces to the driven element ( 10 . 100 ) reach. Adjusting device according to claim 1, characterized in that the bimorph elements are operatively connected to the output element (1) via their side surfaces lying in the region of the free end. 10 . 100 ) reach. Adjusting device according to claim 1, characterized in that in addition to the two actuators forming a bimorph element, a further pair of actuators is provided, which is arranged parallel to it in the drive direction of the first actuator pair and with this to form a double bimorph element ( 16 - 19 . 21 - 28 . 41 - 46 . 51 - 56 ) is firmly connected. Adjusting device according to claim 1, characterized in that in addition to the at least two mutually parallel bimorph elements (41 - 46 ) at least two other bimorph elements ( 51 - 56 ) are provided which extend in the same plane and perpendicular to the first bimorph elements and are also parallel to one another. Adjusting device according to claim 1, characterized in that the bimorph elements ( 6 - 9 . 16 - 19 . 21 - 28 . 41 - 46 . 51 - 56 ) by at least one spring element in operative connection with the output element ( 10 ) 100 ) can be brought and the operative connection of each bimorph element can be canceled by applying voltage. Adjusting device according to claim 1, characterized in that the bimorph elements have a common base ( 11 . 12 . 29 and 49 ) are connected.