DE4408618A1 - Bimorphous element adjustment drive - Google Patents

Abstract

The adjustment device has a piezo drive and is particularly suitable for fine mechanics optical devices, etc. It has at least one piezo-oscillator (1,6-9,16-19,21-28,41-46,51-56) which undergoes length changes by application of different electric voltages. Its free ends alternately come into operative connection with a drive element such that movement is translated to the drive element. When the connection is lifted, the piezo-oscillator, at its free end, is returned ready for the next movement transfer, such that the drive element carries out the adjustment movement in the desired direction. The piezo-oscillators (1,6-9,16-19,21-28,41-46,51-56) have at least two actuators (2,3;61,.62,71,72,81,82,91,92,161,162;171,172,181,182,191,192) arranged adjacent and parallel to each other in the drive direction. They ar fixedly connected together to form a bimorphous element (1,6-9,16-19,21-28,41-46,51-56). The actuators extend perpendicular to the desired direction of movement. They are electrically decoupled from each other and can be controlled separately. By using actuators with different expansions, they can be bent and a curved track is formed in the longitudinal and transverse direction of the bimorphous elements. The return positioning results from lifting the drive element (10,100).

Description

The invention relates to an adjusting device a piezo drive, especially for precision mechanical optical devices and the like, consisting of at least least a piezo transducer, which by placing under differently controlled electrical voltages Undergoes change in length and alternates via its free End with an output element in operative connection reaches such that when the active connection exists, a Motion is transmitted to the output element, whereas, when the active connection is broken, the piezo oscillates a reset in the area of its free end preparation for the next transmission of motion experiences so that the output element the Verstellbewe in the desired direction.

Known adjustment devices from piezo oscillators are For example, the so-called micro-impulse drives: here a piezo oscillator is attached on one side, while with its free end at an angle to a rotor is pressed. Now the piezo oscillator with one high frequency AC excites that in the range the resonance frequency of the transducer is, so leads Vibration standing longitudinal and bending vibrations. This has the creation of an elliptical-like vibration  movement of the free end of the vibrator relative to the rotor result in the rotation of the Rotor. Moved by the wedging effect the rotor moves forward, while the end of the oscillator contributes its backward movement slides along the rotor or takes off.

However, this type of micro-impulse drive is only in able to start the rotor in one direction float. To get a reversible drive, you have to provide another piezo oscillator, which in reverse direction on the rotor, whereby each because the one piezo oscillator out of active connection with the rotor must be located when there is movement accordingly the drive direction of the other piezo oscillator to be fathered.

The micro-impulse drives mentioned, however, have one big disadvantage because the piezo vibrators used with a high-frequency alternating voltage in the ultrasound need to be richly stimulated to stand longitudinally and To generate bending vibrations that only work with the micro push drives. An easy one Longitudinal vibration, as with quasi-static chip would not be able to a drive, but only for a back and forth movement towards the rotor in the order of magnitude of the change in length of the piezo oscillator.

Because of the high-frequency AC voltage applied are such drives only as endurance or with burst control for covering increments  from a few 10 to 100 nm. Exactly Positioning, as is especially the case with precision optical devices would be required is hereby everyone if not possible, because with a resonant Chen oscillator neither a precisely defined adjustment is feasible, the exact point of attack between the rotor and oscillator can be determined and in remaining unclear whether and how the rotor turns during the return movement of the transducer.

The present invention is therefore the object reasons to provide an actuator, which is working in the quasi-static frequency range and thus the creation of the smallest distances and a re producible positioning with resolution up to Subnanometer range enabled.

According to the invention the object is achieved in that the piezo oscillator has at least two actuators, the parallel side by side and in the drive direction arranged one behind the other and to form a bi morph element are firmly connected that the Actuators are approximately perpendicular to the desired movement extend direction and that they are electric from each other are decoupled and separately controllable, such that using a different stretch together associated actuators their bending and thus a Path curve in the longitudinal and transverse directions of the bimorph telem tes is generated, with the provision active under Take off from the output element.

This has the advantage that the bimorph element also well below the resonance frequency, i.e. in  quasi-static frequency range not just movements in the longitudinal direction, but also in the transverse direction can lead to, for example, the shortening of an actuator with simultaneous extension of the neighboring actuator due to the fixed connection of the actuators to one 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 if taxed accordingly ter voltage application of the actuators to the free end movement of the bimorph element in two coordinates directions, for example an elliptical movement is mandatory. The upper area becomes a such an elliptical orbit curve, the Be transmission of movement in the desired direction lead while the lower area where the knit connection between bimorph element and output element is canceled for the provision to prepare the next motion transmission is used.

This results in an even more effective drive behavior especially when the voltage waveforms at phase the actuators of a bimorph element by about 90 ° are shifted and the two actuators with an approximately sawtooth-shaped alternate savings are applied, so that there is the most uniform possible drive movement results.

At least two bimorph elements are expediently provided see so that both alternate for the movement over care while the bimorph element, the itself with its free end in the lower area of the the respective curve is located, is reset. In order to  it is ensured that the output element during the Resetting the bimorph element no undefined Performs movement, but continues in the desired one Direction is moved, i.e. twice the way per time puts back.

If two groups of bimorph elements are used, can be the pressure of the piezo drive from drive element and also the accuracy in positioning further improve. Here are the two groups expediently connected in parallel, that is the name of the bi or next to each other Morph elements are grouped as evenly as possible divided with the same voltage curves.

It is appropriate that the bimorph elements a controller is connected, which is the active connection of each bimorph element with the stripping element ment only after the active connection of the Output element with the other bimorph element represents is. This ensures that in the crit torque of the drive change is still a safe one Clamping of the output element 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 ge suitable voltage profiles, for example through Beauf Beat with a sawtooth AC voltage can be reached. This gives you a conti nuclear drive without power flow interruption under Avoiding 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. When The best constellation has been the arrangement of two or more pairs of bimorph elements, wherein correspondingly related actuators of the pairs paral switched on, but with all four actuators of a pair offset voltage profiles are applied.

In every, not just in the ideal case, it is there partial if the bimorph elements with the same, time shifted voltage profiles are applied.

For the areas of application mentioned above, the has the voltage acting on the bimorph elements is a frequency on, especially below the ultrasonic fre frequency range. Due to the avoidance of reso The vibrations of the bimorph elements are a resolution of the feed movements down to the lower nanometer range rich possible. However, the scope should of the present invention is not exclusively based on limit the frequency range mentioned, since an Er excitation in the ultrasonic range for infeed movements with high speeds makes sense and the Voltage amplitude for example ten times higher or a voltage smaller by a factor of 10 is required is. Because, moreover, the phase shift in the Resonance range is 90 °, it is sufficient here that an electrode of the bimorph element accordingly control, the other electrode automatically lagging by 90 °.  

Basically, the bimorph element can either be over his face, over a side face or else via a connection with the bimorph element Intermediate link in operative connection with the output element reach. Attacking the face of the bimorph elementes is particularly recommended if this - as described above - is used as a drive. On the other hand, however, the bimorph element can be used instead of Drive element also used as a no-brainer become. The bimorph element can change accordingly the adjustment movements on a stationary base move forward, which is a kinematic reversal to the above described drive corresponds.

When used as a drive, the trajectory was still there parallel to the longitudinal extent of the bimorph elements, see above it is useful when used as a self-runner ßig, over a side surface of the bimorph elements in Active connection with the output element, that is, with to get the document. This will, above all a more stable edition of several bimorph telemes existing runner on the pad and so on achieved a lower overall height of the runner. The Anlie of course on the side surfaces, especially in the Area of the free end of the bimorph elements, since there the adjustment movement is greatest.

For use as a no-brainer, it is special an advantage if the two are a bimorph element forming actuators firmly connected another pair of actuators is, with the two pairs of actuators next to each other a square and seen in cross section  should form an arrangement. As a result, both the Ab lift from the stationary base, that to the preparation the provision of the respective bimorph element is required, as well as a vertical Ver actuation movement achieved because the four to a double bi morph element summarized actuators by corre sponding appropriate voltage application on each other can be voted.

However, such double bimorph elements are not considered Self-propelled, but used as drives, so made possible make an adjustment movement in the second dimension sion of the output element level. Here the opening takes place lifting the active connection as in the above Drives by shortening the double bimorph elements.

In any case, it is useful when using both as a drive and as a self-runner if the free ends of the bimorph elements, which are in contact with the output element or with the base, are evenly distributed over these to ensure a stable support to accomplish. In the self-running, this is achieved in particular by a double-comb arrangement of parallel double bimorph elements, as is shown in FIG. 4.

This double arrangement can be expanded in this way if at least two more bimorphs are added elements are provided that are in the same Plane, but perpendicular to the first bimorph elements extend and are also parallel to each other. This has the additional advantage that a loading  movement in the second dimension and thus even Any flat circular and curved movements are possible.

While in the above, used as a runner Bimorph elements whose weight for a permanent Pressing the bimorph elements on the floor is it is particularly useful with the piezo drives that they by at least one spring element in operative connection with the output element can be brought and the operative connection each bimorph element by applying voltage can be canceled. This gives the advantage that due to the permanent pressure from the Spring element a secure clamping of the output element is guaranteed at all times, so always at least one bimorph element in operative connection with the Output element is located. The removal of the active connection is done by the respective bimorph element itself, whereby inevitable path differences no longer exist can have a negative impact on the quality of the clamping. Because only the relative paths and not the Absolutlän gene differences of the bimorph elements for clamping or Taking off are relevant, therefore have length fluctuations of bimorph elements due to temperature, aging and Environmental influences do not affect a reliable Operating behavior of the piezo drive. The bimorphele elements can therefore with low precision requirements and thus can be manufactured more cost-effectively.

To bring about the active connection between bimorph on the one hand there is the element and the output element Lichity that the spring element on the output element acts; on the other hand, the spring element can take place  whose act on the bimorph elements, whereby it it is particularly advantageous here at a ge to assemble common base. This ensures security represents that the currently longer bimorph element the active connection is guaranteed, while the shorter Bi morph element can perform its reset.

The common basis is expediently ge forms that in bimorph made of piezoceramic elements by comb-like sawing out of individual Comb teeth made from a piezoceramic plate are, which is perpendicular to the tines stretching ridge as a common base the verbin between the bimorph elements. Here at are the individual actuators of the type represents that the electrically decoupled and separately controllable electrodes on the piezoceramic be evaporated, expediently - as be already mentioned - in each case equivalent bimorph elements can be connected in parallel.

Another advantage arises when the piezoceramic the bimorph elements are made up of many thin layers det. Through such multilayer bimorph elements that are built up layered in the thickness direction, reduced the required excitation voltage, for example 500 V to 1000 V by a factor of 10 to 50 V to 100 V, which considerably ver the areas of application of such drives enlarged.

In addition, it is also possible that the Bi morph elements instead of piezoceramic made of electro or magnetostrictive material.

Further advantages and features of the present inven dung result from the following description of exemplary embodiments with reference to the drawings; here at show

Figure 1a is the sequence of movement of a bimorph element according to the invention in front view.

FIG. 1b shows the course of the excitation voltage, is applied to the bimorph of Figure 1a.

FIG. 2a shows an adjustment according to the invention best starting view from four bimorph in Vorderan;

Fig. 2b the adjustment drive of Figure 2a in Seitenan view.

Fig. 2c, the adjustment drive of Figure 2a in plan view.

FIG. 2d the driven element and the trajectory curves of the adjusting device from FIG. 2a acting thereon in a sectional front view; FIG.

Figure 3a is an adjustment according to the invention similarity Lich the adjusting of Figure 2a, except that the bimorphous elements each comprise four ren Akto..;

Fig. 3b, the adjustment drive of Figure 3a in Seitenan view.

FIG. 3c view the adjustment of Fig 3a in plan.

FIG. 3d shows a sketch of the mode of operation and the trajectory of the adjusting drive from FIG. 3a;

Fig. 4 shows an alternative design of the adjustment drive from Fig. 3a in a double comb arrangement and

Fig. 5 shows a further design of the adjustment drive from Fig. 3a in a four-way comb arrangement.

Fig. 1a shows a bimorph element 1 in four movement situations No. 1 to No. 4. On the bimorph element 1 consisting of a one-piece piezoceramic, two electrodes 2 and 3 are evaporated to form piezo actuators, which are electrically decoupled from one another and separated by voltage sources A. and B can be controlled. 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.

However, since both actuators or electrodes 2 and 3 are now firmly connected to one another, 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 possible by appropriate voltage application of the two electrodes 2 and 3 to force the free end of the Bi morphelementes 1 movements in the longitudinal and transverse directions, for example in the form of the elliptical orbit curve shown in Fig. 1a, which is described by the center of the free end and was generated by the voltage profiles A (t) and B (t) shown in FIG. 1b.

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

It is now readily apparent that at least two juxtaposed and exactly opposite controlled bimorph elements of the upper area of the ellip Sen-shaped trajectory for transferring the adjustment movement can be used while the lower ellip area due to the neighboring higher bimorphele ment on an active connection between bimorphs ment and output element for resetting the free Can be used in the end.

The adjusting device 5 shown in FIGS . 2a to 2c in different views consists of bimorph elements 6 , 7 , 8 and 9 , each having two actuators 61 and 62 , 71 and 72 , 81 and 82 , 91 and 92 . The bimorph elements 6 to 9 are formed by comb-like sawing out individual comb teeth from a piezoceramic plate while leaving a common base 11 in the form of a comb web, whereupon the individual electrodes on one side of the ceramic plate and on the back of each bimorph element, a neutral conductor 63 , 73 , 83 and 93 are 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. Thus, the electrode 61 connected to the voltage supply C is connected to the electrode 81 , the electrode 62 connected to the voltage supply D to the electrode 82 , etc. This ensures that the bimorph elements 6 and 8 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 elliptical trajectory shown in Fig. 2d (clockwise movement) and thus cause the transfer of the desired adjustment movement to an output element 10 (movement in Fig. 2d to the right).

As can be seen from the trajectory curves, it is particularly expedient for an effective attack of the bimorph elements 6 to 9 on the output element 10 if either the drive element is pushed in the direction of the adjusting device 5 by a spring (not shown) or this is pressed in the direction of the output element 10 , thereby a permanent operative connection with the output element is ensured.

In Fig. 2c is a plan view once again illustrates how 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 63 , 73 , 83 and 93 are evaporated, connected to each other.

In FIGS. 3a to 3c a further Verstellein is directionally represented in different views 15, arranged out on a common base 12 bimorph elements 16, 17, 18 and 19 consists, on the four electrodes 161 to 164, 171 to 174, 181 to 184 and 191 to 194 are evaporated. Due to the additional pairs of electrodes connected to voltage sources K, L, M and N separated from voltage sources G, H, I and J of the first electrode pairs, it is now possible, for example, to apply the electrodes 161 and 162 in the same direction while the Electrodes 163 and 164 are excited with a phase-shifted voltage, whereby a bending of the bimorph element 16 in the thickness direction (that is to say upwards / downwards in FIG. 3c) can be generated. This movement is required in particular in the grip conditions shown in FIG. 3d, wherein the adjusting device 15 extends parallel to a base 100 and extends along it, that is to say the adjusting movement does not produce a transmission of motion to the drive element, but rather the adjusting device 15 moves in the desired direction, although the electrical connections must be carried with the movement of the adjusting device, but a - albeit technically complex - remote control would also be conceivable.

The Fig. 3a to 3c shown Verstellan drive 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 opposite to bimorph elements 21 to 24 extend , which correspond to the bimorph elements 16 to 19 from FIG. 3. Such Ver adjusting device 30 'which also works as a runner is shown in Fig. 4. The lateral deflection of the bimorph elements 21 to 28, which are evenly divided into two groups, can also be seen there. As with the adjusting device 15 from FIG. 3, the voltage applied to the respective bimorph elements must be coordinated with one another in such a way that both a movement of the free ends of the bimorph elements in the transverse direction - which produces the adjusting movement - and a movement of the ends in the thickness direction - the serves to establish and remove the active connection - can be carried out.

Finally, FIG. 5 shows an adjusting device 50 which has two groups of bimorph elements 41 to 46 and 51 to 56 , the bimorph elements 41 to 46 each running parallel to one another, but their direction of extension perpendicular to the bimorph elements 51 which also run parallel to one another to 56 . Such an arrangement has the great advantage that not only the movement in one direction - as is the case with the rotor 30 from FIG. 4 - but also a movement in a second coordinate direction and thus all types of movements in a respective bearing surface parallel plane are possible. Accordingly, not only straight movements perpendicular to one another, but also any curve movements can be performed with such a rotor 50 .

For all adjustment devices or It makes sense for runners instead of a solid piezo ceramic plate a multilayer structure from many thin Ceramic layers to use: While with the plates shape with usually 1 mm thickness in one version Example 500 to 1000 volts are required, see above  decreases with a construction from a multitude correspondingly thinner layers the required voltage about a factor of 10. Take ellip as an example sen-shaped trajectories that result from such Stress application result and from the free end a bimorph element are described, a Hubdif reference of about 1.5 µm and a lateral deflection difference - used for the delivery movement - of 10 µm.

Claims (16)

1. adjusting device with a piezo drive, in particular for precision mechanical optical devices and the like, be existing from at least one piezo oscillator which experiences a change in length by applying differently controlled electrical voltages and alternately via its free end with an output element comes into an active connection such that at Existing active connection, a movement is transmitted to the output element, whereas in the case of an elevated active connection, the piezo oscillator in the area of its free end undergoes a reset to prepare for the next movement transmission, so that the output element performs the adjustment movement in the desired direction, characterized in that Piezo oscillator ( 1 , 6-9 , 16-19 , 21-28 , 41- 46 , 51-56 ) at least two actuators ( 2 , 3 ; 61 , 62 ; 71 , 72 ; 81 , 82 ; 91 , 92 ; 161 , 162 ; 171 , 172 ; 181 , 182 ; 191 , 192 ), which runs parallel and side by side and in the drive direction ereinander arranged and Bil dung of a bimorph element (1, 6-9, 16-19, 21- 28, 41-46, 51-56) are fixedly connected together in that the actuators about movement direction extending perpendicular to the desired loading and that they are electrically decoupled from one another and can be controlled separately, in such a way that, using a different expansion of actuators belonging together, their bending and thus a path curve in the longitudinal and transverse directions of the bimorph element is generated, the provision being active while being lifted off the output element ( 10 , 100 ) he follows. 2. Adjusting device according to claim 1, characterized in that the voltage profiles of the two actuators ( 2 , 3 ; 61 , 62 ; 71 , 72 ; 81 , 82 ; 91 , 92 ; 161 , 162 ; 171 , 172 ; 181 , 182 ; 191 , 192) are of a bimorph element (1, 6-9, 16- 19, 21-28, 41-46, phasenver advanced by about 90 ° 51-56). 3. Adjusting device according to claim 1, characterized in that a plurality of bimorph elements ( 6-9 , 16-19 , 21-28 , 41-46 , 51-56 ) are provided, each of which, in alternation, a part of the transmission of motion to the drive element ( 10 , 100 ) and the other part carries out the reset. 4. Adjustment 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 which 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. 5. Adjusting device according to claim 1, characterized, that the bimorph elements with the same, staggered in time voltage curves (A-B, C-F, G-J, K-N) be hit. 6. Adjusting device according to claim 1, characterized, that the stresses acting on the bimorph elements have a frequency that is quasi-static operation enable and below the ultrasonic frequency range ches can lie. 7. Adjusting device according to claim 1, characterized in that the bimorph elements via their end faces in operative connection with the output element ( 10 , 100 ). 8. Adjusting device according to claim 1, characterized in that the bimorph elements come into operative connection with the driven element ( 10 , 100 ) via their side surfaces lying in the region of the free end. 9. Adjusting device according to claim 1, characterized in that in addition to the two a bimorph element form the actuators ( 161 , 162 ; 171 , 172 ; 181 , 182 ; 191 , 192 ) a further pair of actuators ( 163 , 164 ; 173 , 174 ; 183 , 184 ; 193 , 194 ) is provided, which is arranged parallel to it in the drive direction of the first pair of actuators and is fixedly connected to the latter to form a double bimorph element ( 16-19 , 21-28 , 41-46 , 51-56 ). 10. 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 further bimorph elements ( 51-56 ) are provided which are in the same plane and perpendicular to the first bimorph elements extend and are also parallel to each other. 11. Adjusting device according to claim 1, characterized in that the bimorph elements ( 6-9 , 16-19 , 21-28 , 41- 46 , 51-56 ) can be brought into operative connection with the output element ( 10 , 100 ) by at least one spring element are and the operative connection of each bimorph element can be canceled by applying voltage. 12. Adjusting device according to claim 1, characterized in that the bimorph elements are connected to a common base ( 11 , 12 , 29 and 49 ). 13. Adjusting device according to claim 1, characterized in that the bimorph elements ( 1 , 6-9 , 16-19 , 21-28 , 41- 46 , 51-56 ) consist of piezoceramic. 14. Adjusting device according to claim 13, characterized in that the bimorph elements ( 1 , 6-9 , 16-19 , 21-28 , 41- 46 , 51-56 ) are formed by comb-like sawing out individual comb teeth from a ceramic plate. 15. An adjusting device according to claim 13, characterized in that the piezoelectric ceramic of the bimorphous elements (1, 6-9, 16- 19, 21-28, 41-46, 51-56) of many thin in the longitudinal direction of the bimorphous elements extending Schich th is formed . 16. Adjusting device according to claim 1, characterized in that the bimorph elements ( 1 , 6-9 , 16-19 , 21-28 , 41- 46 , 51-56 ) consist of electro- or magnetostrictive material.