Piezoelectric Actuator and Piezoelectric Actuator Array

Abstract

To manufacture a piezo bending transducer for an actuator array with long service life and high performance.SOLUTION: There is provided a piezoelectric actuator 1 for performing an actuation motion 13. The piezoelectric actuator 1 includes a piezo bending transducer 2 in which the carrier layer 4 is partially covered with a piezo thin layer 3, a movable end 6, and a housing 31. A reference stopper 15 is connected to the housing 31 and determines a reference position 40 for the actuation motion 13. A first bearing area 7 includes an area of the piezoelectric actuator 1 and an area of the housing 31, which allows the piezo bending transducer 2 to twist Φ1. A second bearing area 8 has a surface 10 on the side of the bending transducer, a surface on the side of the housing, and an intermediate layer 12 between these surfaces. The intermediate layer 12 connects these surfaces, and the intermediate layer 12 can be liquefied. A pressure element 24 produces an urging torque to the piezo bending transducer 2 around the first bearing area 7 against the reference stopper 15.SELECTED DRAWING: Figure 4B

Description

[Technical Field]

[0001] The present invention relates to a single piezoelectric bending transducer and also to an array arrangement of a plurality of piezoelectric bending transducers, so-called piezoelectric bending transducer arrays, and their applications, in particular microvalves and microvalve arrays. [Background technology]

[0002] The piezoelectric bending transducer array according to the present invention is particularly useful for actuating microfluidic valve arrays in multi-channel printheads or multi-channel coating heads with one or more rows of dispensing nozzles that can be controlled individually or collectively and dispense droplets or liquid jets onto a surface. Applications include color decoration, sharp-contoured, jet-free, digitally controlled application of one or more layers of liquid coatings such as paints, varnishes, adhesives, and sealants, and functional coating of components.

[0003] Corresponding printheads may be used in the following areas: painting, sealing and gluing of all kinds of autonomous vehicles, including cars, aircraft and ships, primarily using industrial robots (especially multi-axis articulated arm robots) that move the print or coating head, or coating of any kind of parts, including products in the consumer goods industry, with liquid coatings using industrial or Cartesian robots or such robots integrated into single-pass printing or single-pass coating systems, and in any coating required in connection with construction.

[0004] In particular, the microvalve arrays described above are used as micro-pneumatic pilot valve arrays working on electro-pneumatic operating principles in printheads or coating heads of the type mentioned above, for example as described in U.S. Patent No. 5,629,994. The components described herein perform the functions of the components of the micro-pneumatic circuits and actuators described in U.S. Patent No. 5,629,994.

[0005] Prior art piezoelectric bending transducers (see, e.g., FIG. 1 ) discussed herein are typically actuators of a specific length, rigidly clamped on one side to generate actuation motion at a movable end perpendicular to the longitudinal direction. Furthermore, such piezoelectric bending transducers are primarily flat and comprise multiple layers of material, including at least one piezoelectric layer. Longitudinal expansion resulting from application of a voltage to one or more piezoelectric layers causes the bending transducer to bend perpendicular to the longitudinal direction. This is the result of internal tension in the multilayer structure, and the deflection is significantly larger than the longitudinal expansion. Piezoelectric bending transducers are used for actuation tasks in that they move actuating elements, such as microvalves, either directly at their first movable end or via an effector. As the length of a piezoelectric bending transducer increases, the deflection increases, and the natural frequency of the first natural mode used for actuation tasks decreases, resulting in a corresponding decrease in force and stiffness. The design goal of a bending transducer is typically to maximize the deflection, force, and first natural frequency. The piezoelectric bending transducers discussed herein are designed with distances between adjacent piezoelectric bending transducers of 0.5 mm [millimeters] to, for example, 10 mm or more, and strokes on the order of 20 μm [micrometers], 50 μm, 100 μm, 200 μm, or more.

[0006] For a given operation, it is essential that the reference position of the movable end of the piezoelectric bending transducer, or the reference position of the effector connected to this movable end, remains constant relative to the microvalve's actuating element. The microvalve's actuating element is the valve's movable element, e.g., a closing element corresponding to the valve opening. Thus, a "valve" is formed, with the valve opening closing or opening depending on the position of the actuating element. Due to the small deflection of each microvalve, undesirable changes in the piezoelectric bending transducer or its surroundings, including the housing (such as mechanical expansion, deformation, or creep processes that may occur over time or are temperature-related) affect the reference position, i.e., the distance between the effector and the microvalve's actuating element. A change in the reference position alters the function of the microvalve. Conventional piezoelectric bending transducers, for example, are rigidly clamped on one side, as shown in FIG. 1A, and therefore cannot compensate for these changes over time.

[0007] As a solution, Patent Document 2 proposes a piezoelectric bending transducer for pneumatic valves equipped with a "floating bearing" or fluid bearing. A biasing torque is applied by a spring that presses the piezoelectric bending transducer against a reference position, and the fluid bearing offers no resistance when stationary, thereby continuously compensating for gradual changes. However, if a highly viscous bearing fluid is used, rapid actuation movements encounter fluid resistance. Therefore, the fluid bearing acts like a fixed bearing for the actuation movement. On the other hand, a drawback of using a fluid bearing is that it is not possible to operate with static deflection. Fluid bearings are only suitable for pulsed operation.

[0008] In addition to the requirement that the operating function remain unchanged over the entire period of use even under the aforementioned harmful influences, there are also basic underlying requirements for the aforementioned applications, such as a high operating frequency, for example in the range of 500 Hz, 1 kHz, 2 kHz, 3 kHz, 4 kHz, or 5 kHz, a large bending transducer deflection, a high coercive force, a low operating voltage, a small difference between adjacent piezoelectric bending transducers, an unlimited possible service life, and inexpensive mass production of piezoelectric bending transducer arrays and microvalve arrays. [Prior art documents] [Patent documents]

[0009] [Patent Document 1] European Patent No. 2442983(B1) [Patent Document 2] German patent number 102009033780 (B4) Summary of the Invention [Problem to be solved by the invention]

[0010] Overall, the problem addressed by the present invention is to fabricate piezoelectric bending transducers of actuator arrays with long service life and high performance, specifically targeted for the mentioned applications. [Means for solving the problem]

[0011] This problem is solved by a piezo actuator with the features of the independent claims, which comprises a piezo bending transducer and a piezo bending transducer array consisting of at least one row of piezo bending transducers,

[0012] Piezoelectric actuators according to the present invention, including the disclosed embodiments, and piezo actuator arrays comprising such piezo actuators, enable continuous long-term operation.

[0013] According to the proposed method for aligning a piezoelectric actuator, an automated alignment process of the piezoelectric actuator with respect to a reference stop is repeatedly carried out in order to be able to actuate an actuating element, such as a closing element of a microvalve, in a repeatable manner at any time. In the alignment process, the piezoelectric actuator is always returned to its reference or starting position with respect to the actuating element, in this case, to eliminate any undesired changes in the piezoelectric element, the actuating element, the microvalve, or in the area of ​​the housing. This state remains until the next alignment process. In the alignment process, the intermediate layer is temporarily melted in the bearing area of ​​the piezoelectric bending transducer, and each piezoelectric element is brought to a defined charge state. An external force on the piezoelectric bending transducer causes the piezoelectric bending transducer to move its movable end or an effector connected to this movable end against a reference stop, such as a closing element of a microvalve. In contrast This state is then frozen by solidification of the intermediate layer, and the piezo actuator is again at its reference position.

[0014] It should be noted that the alignment process according to the invention can be used in many ways, for example, during the initial installation and start-up of components, in particular print heads, coating heads, dosing heads, dispensing heads, liquid valves, pneumatic valves, etc., to name a few. It can also be used during maintenance work, i.e., when changing components for a new application, when changing or replacing peripheral components, or when changing the operating conditions of an existing configuration, for example, to adapt it to a changed application or specification. It can also be used, in particular with print heads and coating heads, when adapting this head to the use of a different or changed coating material, or to changes in operating parameters (temperature, pressure, etc.) or coating parameters (layer thickness, application speed, drop frequency, change between droplet and jet application). It can also be used after changing the position of a reference stop or when changing the charge state of each piezo element of a piezo actuator associated with a reference stop. In short, the alignment process according to the invention can be used in all situations where a piezo actuator needs to be referenced with respect to new or changed conditions of any kind.

[0015] The piezo actuator according to the invention is used to perform the actuation movement and comprises the necessary devices and means to enable the aforementioned alignment process. For this purpose, the piezo actuator first comprises a piezo bending transducer made of a carrier layer, which is at least partially covered on one or both sides with a thin piezo layer. Furthermore, the piezo actuator comprises a movable end for performing the actuation movement, a housing in which the piezo bending transducer is mounted, and an actuation element or actuation application (such as a microvalve) firmly connected thereto. The piezo actuator according to the invention is further characterized by: a reference stop connected to the housing and determining a reference position for the actuation movement of the actuation element or actuation application; a first bearing area including an actuator area and a housing area and allowing a torsion Φ1 of the piezo bending transducer; a second bearing area having a surface on the side of the bending transducer, a surface on the side of the housing, and an intermediate layer between these surfaces, which connects these surfaces and can be liquefied (at low temperatures); and finally, a reference stop. against , a pressure element for generating an energizing torque on the piezo bending transducer around the first bearing area.

[0016] Thus, a piezo actuator according to the present invention, including a piezo bending transducer and a corresponding piezo bending transducer array, originally comprises a carrier layer according to the prior art of Patent Document 2. The carrier layer is covered on one side ("monomorphically") or both sides ("bimorphically") by a thin piezo layer that at least partially covers the carrier layer. The thin piezo layer also has a conventional metal coating, for example made from a silver-containing thick layer or thin-film structure. Furthermore, the piezo bending transducer (and the corresponding piezo bending transducer array) has a movable end for performing the actuation movement, a reference stop associated with the movable end of the piezo bending transducer that defines a reference position for the actuation movement, and a first bearing area designed to allow the piezo bending transducer to rotate around it. The piezo bending transducer also has a second bearing area with an intermediate layer located between the surface facing the bending transducer and the surface facing the housing. Furthermore, the piezoelectric bending transducer has a pressure element in the region of the first bearing region for generating a constant biasing torque on the piezoelectric bending transducer around the first bearing region, the pressure element being oriented so that the movable end of the piezoelectric bending transducer or an effector connected to this movable end is pressed against an actuator or a reference stop associated with the microvalve.

[0017] However, in contrast to Patent Document 2, the intermediate layer in the second bearing region consists of a solid that can be temporarily melted (melted) into the intermediate layer. In one operating mode, the intermediate layer in the second bearing region is in a solid-state condensed state, and in another preferred variant, the intermediate layer acts primarily like a fixed bearing or primarily like a rotatable bearing. Thus, it acts like a bearing that is fixed in one or more translational degrees of freedom, at least in the direction of the actuation movement of the piezoelectric bending transducer. Thus, in contrast to Patent Document 2, the piezoelectric bending transducer also allows static deflection during operation.

[0018] In the first bearing type LA1, the second bearing area, which always comprises an intermediate layer, supports the piezoelectric bending transducer in a larger area, which preferably acts rigidly in all six degrees of freedom of movement (see FIG. 1). In the second bearing type LA2, the second bearing area is of narrowly defined or point-like design and is located at the end of the piezoelectric bending transducer opposite the movable end of the piezoelectric bending transducer (see FIGS. 2A to 3C).

[0019] The piezoelectric bending transducer further features an operating mode and an alignment mode. In the operating mode, the piezoelectric bending transducer performs an actuation motion, the temperature of the intermediate layer is below its liquefaction temperature, and the intermediate layer is sufficiently stiff to transmit bearing forces in the second bearing region. In the alignment mode, the piezoelectric bending transducer is aligned to the reference stop while the temperature of the intermediate layer is above its liquefaction temperature due to the application of heat.

[0020] In the alignment mode, an alignment process is carried out one or more times, including the steps of heating the intermediate layer of the second bearing region with a heat source to liquefy the intermediate layer, or applying a voltage to all electrodes of the piezoelectric bending transducer that is to be related to the position of the reference stop, and then, in a subsequent step, moving the piezoelectric bending transducer to the reference stop under the influence of an applied torque for the duration of an alignment time TA. In contrast The method includes a step of aligning the second bearing region and, finally, a step of solidifying the intermediate layer by cooling the second bearing region during a cooling time TK. The order of these steps can be interchanged. Thus, in the step of solidifying the material of the intermediate layer, the positions of the surface of the second bearing region facing the bending transducer and the surface of the housing relative to each other are frozen during solidification.

[0021] It should be noted that prior to the step of solidifying the intermediate layer at an alignment time TA, which may be in the range of 1 / 2 second, 1 second, 5 seconds, 10 seconds, 30 seconds, 1 minute, etc., the intermediate layer must simultaneously be in a fluid state and a specified voltage must be applied to all electrodes of the piezoelectric bending transducer.

[0022] If there was a deviation in the position of the piezoelectric bending transducer with respect to its alignment with the reference stop before the alignment process, the piezoelectric bending transducer rotates in a positive or negative rotational direction around the first bearing region during the alignment time TA. While aligning the piezoelectric bending transducer in the alignment process, the position of the bending transducer-side surface of the second bearing region changes relative to the fixed surface of the second bearing region associated with the housing, allowing the liquefied material to flow into and out of the intermediate layer into the gap between the surfaces. Eventually, the relative position of the two surfaces is frozen during solidification, and the piezoelectric bending transducer is in its reference alignment state.

[0023] The alignment step can be performed as a one-off step during the initial assembly of the piezoelectric bending transducer to initially bring the piezoelectric bending transducer into a reference alignment or position, in which case the heat of fusion required to melt the intermediate layer can be provided by, for example, hot air or a soldering iron tip.

[0024] The alignment process can also be performed several times over the useful life of the print head or coating head or at regular intervals, for example, on a yearly, monthly, weekly, daily, or hourly basis, so that the piezoelectric bending transducers, and thus all of the piezoelectric bending transducers in the piezoelectric bending transducer array, can be operated accurately in their reference alignment state for many years.

[0025] In addition to providing long-term stability in a multi-channel printhead or multi-channel coating head based on a piezo actuator and having one or more piezo actuators, variations between the individual channels are minimized after completion and after the initial alignment process.

[0026] In this context, it is also proposed to continuously detect deviations in the printed image as part of quality assurance during printing or coating operations, by means of test printouts or test coatings, and to perform one or more timely alignment steps. During deviation detection, differences between the channels of the print head or coating head can be displayed. Specific adjustments to the printing or coating process can be made, for example, by enlarging or reducing the active area or by moving the active area of ​​the piezo actuator. In this regard, it is particularly recommended to perform the alignment step with a modified charge state compared to the last alignment step performed, i.e., by applying a modified voltage to the electrodes of the piezo bending transducer.

[0027] It is therefore proposed that a sequence of procedures for adjusting a print head or coating head to suit an application, or for carrying out quality improvement measures, comprises at least once the following steps: a) performing drop or jet ejection from a nozzle, and / or producing a test printout or performing a test coating with a print head or coating head; b) metrological, optical or visual detection and qualification of the test printout or test coating, for example by measuring the layer thickness, the edge sharpness, the glossiness, the flatness of the layer and detecting splashes or associated droplets, or by optical inspection of the dynamic droplet ejection, including the jet or droplet velocity, of the corrosion process and of the deposition of coating material on the printhead, in particular at the nozzle outlet. c) performing an alignment step, where the voltages applied to the electrodes of the piezoelectric bending transducer are different from the voltages at the time of the last alignment step, or the position of the reference stop has changed compared to its position at the time of the last alignment step; It should be noted that this sequence as a whole can be considered as an iterative process, preferably with the alignment step according to c) being carried out even before the first step according to a), and finally terminating the iterative process after step b) if satisfactory results are obtained.

[0028] If the alignment process is repeated, one or more heating elements are preferably already firmly integrated into the print or coating head, preferably connected to the housing and in thermal contact with the surface of the second bearing area assigned to the housing. In this case, each heating element and each voltage applied to each electrode of each piezoelectric bending transducer can be controlled via a process controller. This process controller can optionally be the same process controller that performs the overall control of the printing or coating process, or it can be subordinate to the aforementioned process controller. Here, such control can be achieved by simply specifying the heat output and duration, or (preferably) by temperature control. This temperature control is preferably based on measuring the actual temperature near the second bearing area with a temperature sensor.

[0029] The heat output emitted by the heating element is preferably controlled by a process controller so that the temperature in the second bearing region rises above the melting temperature of the intermediate layer and so that the intermediate layer melts in a period of the order of 1 second, 10 seconds, or 100 seconds.

[0030] It should be mentioned here that the initial alignment step is carried out during the initial assembly of a print or coating head or component comprising one or more piezo actuators according to the invention. In this case, an integrated heating element in thermal contact with the second bearing area can also be used to liquefy the intermediate layer in the alignment mode. Alternatively, however, the intermediate layer can be liquefied by an external heat source such as hot air or by contacting a soldering iron with the material of the intermediate layer or with one of the surfaces adjacent to the intermediate layer.

[0031] For example, the intermediate layer can preferably consist of solder, the melting temperature of which is below 150°C, 200°C, or 250°C. At the same time, the solder can be used to electrically contact either the carrier layer of the piezoelectric bending transducer or the electrodes of the piezoelectric thin layer. Alternatively, the intermediate layer can consist of a hot-melt adhesive, a thermoplastic material, a thermoplastic elastomer (TPE), bitumen, or wax, the melting temperature of which is below 100°C, 150°C, 200°C, or 250°C. It should be noted that the maximum temperature of the piezoelectric thin layer of the piezoelectric bending transducer, which is induced by heating, should remain sufficiently below the Curie temperature of the piezoelectric material. Therefore, generally, any material with a sufficiently low melting point is preferred for use as the intermediate layer, since this allows the material of the intermediate layer to melt without the maximum temperature of the piezoelectric thin layer approaching the Curie temperature of the piezoelectric material. The use of solder or thermoplastic material as an intermediate layer primarily ensures a solid connection and directly eliminates any torsional tolerances at the connection point. Any elastic components required within the individual bearing areas would then have to be added separately. In the case of thermoplastic elastomers (TPU, TPE), the elasticity of the material means that the rotational tolerances of the corresponding second bearing area can already be achieved.

[0032] Piezo bending transducer as reference fixture In contrast The alignment is performed during an alignment time TA under the influence of a biasing torque. The piezo actuator according to the invention therefore comprises means for applying a biasing torque to the piezo bending transducer around the first bearing area, as a result of which the movable end of the piezo bending transducer or an effector connected to this movable end is pressed against the reference stop.

[0033] The biasing torque is applied by a pressure element exerting a defined force F on the piezoelectric bending transducer. The contact point between the pressure element and the piezoelectric bending transducer is offset by a lateral offset x along the piezoelectric bending transducer from the pivot point of the first bearing region. Clamping force F of the piezoelectric bending transducerK The level of force F and displacement x based on the distance L of the first bearing area to the operating point of the piezoelectric bending transducer R The following relationship holds for F*x<0.5*F K *L R This structural application of force will be addressed using the illustrated embodiment.

[0034] It should be noted that the corresponding piezoelectric bending transducer 2 of the piezoelectric actuator according to the invention can be constructed monomorphically with only a single piezoelectric lamina 3 glued to the carrier layer 4, or bimorphically with two piezoelectric lamina 3 glued on either side of the carrier layer 4. The one or two piezoelectric lamina 3 cover the carrier layer 4 or substantially completely cover the carrier layer 4, for example mainly in the region of the free length L1 of the piezoelectric bending transducer.

[0035] In addition to the above-mentioned measures for ensuring, adapting, or restoring constant operating conditions of the piezoelectric actuator, the second bearing type LA2 of the piezoelectric bending transducer in the piezoelectric actuator according to the present invention further significantly improves the performance of the piezoelectric bending transducer compared to the prior art. This opens up opportunities for applications with higher performance requirements or higher power density. Conversely, for the same application and the same actuation workload, the control voltage can be reduced, thereby significantly reducing the voltage load and mechanical tensile load on the piezoelectric elements. This significantly improves their long-term strength, even to the level of fatigue strength. Since the actuation performance per individual actuator or per pressure channel remains unchanged compared to the prior art, the width of the piezoelectric bending transducer can be reduced, which in the case of a print head or coating head, allows for a smaller channel width or a smaller distance between dispensing nozzles, or even improves printing resolution.

[0036] In a preferred embodiment, the piezoelectric actuator is characterized by: an actuation point at its movable end, or an effector connected to this movable end for performing actuation movements; a centrally located and narrowly defined bearing area including the area of ​​the actuator and the housing; and a laterally located and narrowly defined bearing area at the end opposite the movable end including the area of ​​the actuator and the housing. The centrally located bearing area and the laterally located bearing area each have elastic members that allow local rotation of the piezoelectric bending transducer of at least + / - 2°. In this case, the centrally located bearing area is preferably located in the middle of three sections of the piezoelectric bending transducer.

[0037] For clarity of designations, it should be noted that the previously described bearing areas "first bearing area" and "second bearing area" can correspond to both "centrally located bearing area" and "laterally located bearing area", respectively. That is, the designations "first bearing area" and "second bearing area" are based on their function and design, while the designations "centrally located bearing area" and "laterally located bearing area" are based on their location.

[0038] In the second bearing type LA2, the central bearing area is preferably located in the middle of the piezoelectric bending transducer's third section, and the lateral bearing area is located at the end of the piezoelectric bending transducer opposite the movable end. Both bearing areas are narrowly defined or point-like in design and are designed to allow or tolerate the rotational movement of the piezoelectric bending transducer around the bearing resulting from the piezoelectric bending transducer's deformation without significant resistance. This bearing arrangement enables the first eigenmode of the piezoelectric bending transducer, as shown in FIG. 3A and elsewhere. Compared to the rigidly clamped piezoelectric bending transducer outlined in FIG. 1, this is characterized by the realization of a significantly larger actuation path (D2 in FIG. 3A instead of D1 in FIG. 1) for a given bending radius R (same control voltage and deformation) and a given free length L1 of the piezoelectric bending transducer. The rigidly clamped piezoelectric bending transducer lacks stiffness, resulting in reduced actuation forces. The much higher or larger actuation path is due to the deformation curve of the piezoelectric bending transducer already being torsion Φ in the centrally located bearing region, which leads to an increased end deflection D2 (see e.g. Fig. 3A). Note that in the region of length L2, i.e. between the centrally located bearing region and the laterally located bearing region, the piezoelectric bending transducer deflects in the opposite direction to the region of free length L1 which includes the movable end of the piezoelectric bending transducer.

[0039] Furthermore, a piezoelectric bending transducer mounted in this manner has a torque curve that is more uniform over its length than a typical fixed fastener, such as that shown in Figure 1, which experiences a strong maximum load on the fastener, which is a common cause of stress-related failures.

[0040] To enable the eigenmodes of the piezoelectric bending transducer shown in FIG. 3A, the centrally located bearing area (FIG. 3B) and the lateral bearing areas (FIG. 3C) must be able to rotate the piezoelectric bending transducer according to its deformation curve. However, the piezoelectric bending transducer must be firmly supported, at least in the direction parallel to the actuation movement. For this purpose, different technical implementation options are proposed. For example, one option is the use of supports that are fixed relative to the housing and are designed as fixed, pointed or linear contact elements that protrude, for example, from housing appendages. The piezoelectric bending transducer rests on these contact elements, which can perform tilting movements out of the plane of the piezoelectric lamina. In this case, the piezoelectric bending transducer must be pressed against the support with sufficient compression force to prevent it from lifting, especially when the actuation force is high or the operating mode is highly dynamic. This compressive force is exerted by a movable spring-actuated contact element, such as a metallic spiral spring, bending spring, electrical contact spring, or by an elastomeric element, on the side of the piezoelectric bending transducer opposite the support, in a corresponding bearing area.

[0041] In addition to using supports in combination with pressure elements, it is also possible to realize point-like rotatable supports of the piezoelectric bending transducer, in that each bearing area essentially provides a translational fixation. In order to obtain the required rotational movement according to the bending line of the piezoelectric bending transducer in the centrally arranged and laterally arranged bearing areas, it is further proposed that these bearing areas have elastic elements that allow rotational movement around each (possibly virtual) pivot point of each bearing area.

[0042] The elastic members can be, for example, elastic members of the piezoelectric bending transducer in each bearing region, e.g., separate elastic elements or structurally elastic regions of the carrier layer. The elastic regions are associated with each bearing region and are locally not covered by the piezoelectric thin layers. These can be, for example, regions of the carrier layer (in the case of laterally positioned bearing regions) that protrude laterally from one or two piezoelectric thin layers. The aforementioned elastic members can also be elastic intermediate layers made of elastomeric material in each bearing region. Furthermore, these elastic members can also be elastic members associated with the housing or additional elastic or spring-like components connected to the housing between the housing and each bearing region. These elastic members are configured to allow rotation of the piezoelectric bending transducer, at least to a small extent, locally in the region of each bearing region. Particular embodiments will now be described with reference to the figures.

[0043] With regard to the dimensional ratios, it should be noted that, depending on the application, the length L1 of the piezoelectric bending transducer is, for example, between 4 mm and 6 mm, between 5 mm and 9 mm, or between 7 mm and 15 mm. The length ratio L1 / L2 is preferably between 0.5 and 2. The at least one piezoelectric lamina can cover the carrier layer mainly in the region of the free length L1 or in the regions L1 and L2, i.e., on both sides of the respective central bearing region. The latter case is only significant for the variant of the second bearing type LA2, which produces the maximum deflection.

[0044] A corresponding piezoelectric actuator array preferably consists of identical piezoelectric actuators according to the invention with corresponding piezoelectric bending transducers. Depending on the type of application, these piezoelectric actuators are preferably spaced apart from one another at a distance of between 0.5 mm and 1 mm, between 0.75 mm and 2 mm, or between 1.5 mm and 5 mm. The width (B) of the gap between adjacent piezoelectric bending transducers is preferably between 0.05 mm and 0.2 mm, between 0.1 mm and 0.3 mm, or between 0.2 mm and 0.6 mm. Furthermore, the first and second bearing areas of each piezoelectric bending transducer, or the central bearing area and the lateral bearing areas, respectively, are aligned in a line.

[0045] Furthermore, within the piezo actuator array, each contact point of each pressure element, each pivot point of each bearing area, and each actuation point of each individual piezo bending transducer lie on a line.

[0046] Furthermore, the piezo actuator array preferably comprises a portion including at least all the piezo bending transducers and bearing regions, said portion including a plurality of portions of the bearing region associated with the housing, and for this purpose it is advantageous to use torsionally elastic connections between adjacent piezo bending transducers of the array, for example at their respective first bearing regions.

[0047] Furthermore, the above-mentioned components associated with the housing (supports, pressure springs, etc.) of each first bearing area and of each second bearing area preferably consist of structured plates.

[0048] By way of definition, the term "bearing area" refers to all components associated with the bearing, whether point-like, narrow or wide, located in the area between the piezoelectric bending transducer and the part of the housing 31 associated with the bearing, or to components connected to the bearing and effectively contributing to the behavior of the bearing (whether it is a fixed or a rotary bearing). It should be taken into account that the rotary bearing may be realized in the area of ​​the bearing by means of elastic members effective for this purpose.

[0049] For the avoidance of doubt, ordinal numbers ("first," "second," ...) used herein primarily (and only) serve to distinguish between multiple similar objects, values, or steps, i.e., do not necessarily establish any dependency or ordering of those objects, values, or steps relative to one another. If a dependency or ordering is required, this will either be explicitly stated herein or will become apparent to those skilled in the art from a review of the embodiments actually described.

[0050] The present invention and technical environment will be described in more detail below with reference to the drawings. It should be noted that the present invention should not be limited to the illustrated embodiments. Unless otherwise specified, it is possible to extract partial features of the technical content illustrated in the drawings and combine them with other components and knowledge from this specification and the drawings. It should be noted that the drawings and the illustrated dimensional ratios are merely approximate. The same reference numerals represent the same objects, and any explanations from the explanations of other drawings can be used as supplements as necessary. [Brief explanation of the drawings]

[0051] [Figure 1] A principle diagram of a piezo actuator 1 using a first bearing type LA1 is shown. [Figure 2A] 1 shows a principle diagram of a piezo actuator 1 according to the second bearing type LA2. The first bearing area 7 is located in the center of the piezo bending transducer 2, and the second bearing area 8 is located laterally at the stationary end 5 and is designed narrower. [Figure 2B] 1 shows a principle diagram of a piezo actuator 1 according to the second bearing type LA2, in which the second bearing area 8 is located in the center and the first bearing area 7 is located laterally at the stationary end 5 of the piezo bending transducer 2. [Figure 3A] Schematic diagram of the piezo actuator 1 with second bearing type LA2, with an enlarged view of a special eigenmode of the deflected piezo bending transducer 2. [Figure 3B] This is a further enlargement of the bearing area 16 located in the center. [Figure 3C] The bearing area 17 located in the lateral direction is further enlarged. [Figure 4A] 1 is a top view of an embodiment of a piezo actuator array consisting of a plurality of piezo actuators 1. FIG. [Figure 4B] 1 shows a cross section of an embodiment of a piezo actuator array consisting of a plurality of piezo actuators 1. [Figure 5] 1 shows a cross section of a further embodiment of a piezo actuator array consisting of a plurality of piezo actuators 1. [Figure 6A] A further embodiment of the second bearing area 8 is shown. [Figure 6B] A further embodiment of the second bearing area 8 is shown. DETAILED DESCRIPTION OF THE INVENTION

[0052] FIG. 1 shows a schematic diagram of a piezoelectric actuator 1, consisting of a piezoelectric bending transducer 2 deflected by D1 at its movable end 6. The movable end 6 in this case also represents an actuation point 14 that contacts an actuator, preferably a closing element of a microvalve. Also shown is a first bearing area 7, which can rotate within a limited range of ±5°. The first bearing area 7 is configured as a support 9, which represents a pivot point 22 for the first bearing area 7 and is also connected to the housing 31. The distance between the pivot point 22 of the first bearing area 7 and the actuation point is designated LR. A second bearing area 8 is also shown, which here extends laterally along the piezoelectric bending transducer. The second bearing area 12 comprises an intermediate layer 12 made of a liquefiable or meltable material between a surface 10 of the second bearing area 8 facing the piezoelectric bending transducer and a surface 11 facing the housing.

[0053] The second bearing area 8 in this embodiment is so extensive that it acts as a fixed fastening overall. In this case, this characteristic is designated as the first bearing type (LA1). Meanwhile, as shown, a biasing torque 34 permanently acts on the piezoelectric bending transducer 2 around the first bearing area 7. This biasing torque 34 is generated by a downward force F acting on a contact point 23 located a distance x from the pivot point 22 along the bending transducer of the first bearing area 7. The biasing torque 34 is dimensioned to correspond to a slight, constant moment load on the piezoelectric bending transducer 2, which corresponds to a reference stop 15 that defines a reference position 40 for the actuation movement 13 of the piezoelectric bending transducer 2 when the intermediate layer 12 is fused, i.e., when no force is applied. In contrast1. The intermediate layer 12 has a thickness sufficient to rotate the piezoelectric bending transducer. As mentioned above, the intermediate layer 12 can be liquefied in the alignment mode by melting it. For example, the intermediate layer can be melted by applying heat from an external heat source 38 in the form of a hot air supply while attached, or by using a soldering iron. As mentioned above, the alignment process can also be performed repeatedly with multiple short pauses during operation using an integrated heating element 28 in communication with a controller, with selective temperature control by a temperature sensor 37. In this case, the heating element 28 and temperature sensor 37 are connected to the housing 31 or the like and are in intimate thermal contact with the second bearing region 8. A potential insulating layer 39, which prevents excessive heat from flowing into the housing 31, is located below the heating element, but is not shown here.

[0054] FIG. 2A shows a schematic diagram of a piezoelectric actuator 1 according to the second bearing type (LA2). To avoid redundancy, reference is made to the description of FIG. 1, and only the differences will be discussed below. This second bearing type differs from the first bearing type (LA1) in FIG. 1 in that the second bearing area 8 is spatially narrowly defined and designed to perform a small rotational movement, e.g., a maximum of ±2°. Replacing the fixed bearing of the second bearing area 8 in FIG. 1 with a rotary bearing results in a different bending line of the piezoelectric bending transducer 2 compared to FIG. 1, which allows for a piezoelectric actuator 1 with a much higher actuation power. In FIGS. 1 and 2A, the first bearing area 7 corresponds to the centrally located bearing area 16 (see FIGS. 3A and 3B) of the second bearing type, while the second bearing area 8 with the intermediate layer 12 corresponds to the laterally located bearing area 17 (see FIGS. 3A and 3C) of the second bearing type LA2.

[0055] Figure 2B shows a second option for implementing the second bearing type LA2. This second option differs from the option shown in Figure 2A in that the first bearing area 7 corresponds to the laterally located bearing area 17 of the second bearing type, and the second bearing area 8 with the intermediate layer 12 corresponds to the centrally located bearing area 16 of the second bearing type LA2. To avoid repetition, reference is again made to the description of Figures 1 and 2A and only the differences will be highlighted.

[0056] 2B can also be transferred to the first bearing type LA1. The difference between the bearing types is again that in the latter the second bearing area 8 is wider and is designed as a fixed bearing.

[0057] FIG. 3A shows the bending line of a piezoelectric bending transducer 2 with a second bearing type LA2. This bending line represents the first eigenmode of the piezoelectric bending transducer 2 under the limiting conditions of the central bearing 16 and the lateral bearing 17. Both bearings resist local rotational deformation of the piezoelectric bending transducer 2. In this case, the entire length L1+L2 of the piezoelectric bending transducer 2 is preferably coated on one side (monomorphically) or both sides with a thin piezoelectric layer. In this context, L1 represents the free length L1 of the piezoelectric bending transducer 2, which specifies the length of the piezoelectric bending transducer 2 that is freely movable between the central bearing 16 and the movable end 6. The stationary end 5 of the piezoelectric bending transducer 2 is fixed on the lateral bearing 17. In order to compare the difference in the actuation path at the movable end 6 with a piezoelectric bending transducer 2 of the first bearing type LA1 as in Fig. 1, we assume that the piezoelectric bending transducer 2 according to Fig. 1 is constructed identically to the piezoelectric actuator 1 of Fig. 3A in its area L1. They both therefore have a radius of curvature of magnitude R in the deflected state. Due to the same radius of curvature, it can be seen that the resulting deflection D for the second bearing type LA2 is significantly larger than for the first bearing type LA1.

[0058] Figures 3B and 3C show magnified views of the deformation of the piezoelectric bending transducer 2 according to Figure 3A, respectively at the central bearing area 16 (Figure 3B) and at the lateral bearing areas 17 (Figure 3C). The twists Φ1 and Φ2 are shown. During operation, these twists typically move within a range of + / - 2 degrees.

[0059] 4A and 4B show an exemplary embodiment of a piezoelectric actuator array 32, which includes a bimorph piezoelectric actuator 2 according to FIGS. 2A and 3A and is mounted by a second bearing type LA2. In this case, the centrally located bearing area 16 corresponds to the first bearing area 7, shown in dashed lines in FIG. 4B, and is equipped with a support 9 as a pivot bearing. The lateral bearing area 17 corresponds to the second bearing area 8 for performing the actuation movement 13 at the movable end 6 of the piezoelectric bending transducer 2. The movable end 6, shown on the left, includes an effector 19, which has an actuation point 14 at its tip. The effector 19 is preferably connected to the piezoelectric bending transducer 2 via an elastic connection 20, which in this case can be, for example, an elastomeric intermediate piece or an elastic adhesive. The elastic connection 20 reduces the transmission of shocks from the actuation point 14 to the piezoelectric bending transducer 2 and simultaneously provides the effector 19 with some rotational tolerance.

[0060] In this embodiment, the biasing torque 34 is applied by a pressure element 24 in the form of a structured, optionally curved, tongue-like pressure spring strip or array 24, located below a retaining bridge 25. The springs can have any significant shape, but are shaped to exert a force F on the individual piezo bending transducers 2 exactly at the contact points 23. For this purpose, each of these piezo bending transducers can optionally have a separate pressure element.

[0061] The electrical contact of the piezoelectric bending transducers 2 requires that all piezoelectric thin layers 3 be connected on the upper side with an operating voltage VDD of, for example, 100 V to 200 V, and on the lower side with ground (GND). This contact is made by connecting one or more connection electrodes 18 on the upper and lower sides. These connection electrodes 18 extend transversely to each piezoelectric bending transducer 2 and are applied during the manufacture of the piezoelectric actuator array 32 as contact strips or contact wires, for example made of copper, brass, nickel or a thin flexible circuit carrier material, by soldering or gluing under pressure.

[0062] The second bearing area 8, which includes the intermediate layer 12, is located at the stationary end 5 (located to the right) of the piezoelectric bending transducer 2. This shows an embodiment in which the carrier layer 4 is made of a solderable material such as nickel, copper, or brass. The second bearing area 8 thus comprises areas of the carrier layer 4 that are not covered with the piezoelectric thin layer 3 and represent the elastic areas 21 of the second bearing area 8. Therefore, the small thickness of the carrier layer 4, for example between 30 μm and 100 μm, already provides sufficient bending elasticity to allow bending lines such as those in FIG. 3A. FIG. 4A shows that the carrier layer 4 is designed to be narrower in the elastic areas 21. This reduces the bending forces in the elastic areas 21.

[0063] 4A and 4B, the surface 10 of the second bearing area 8 facing the bending transducer is therefore a lateral surface of the carrier layer 4 of the piezoelectric bending transducer 2, which is not covered by the thin piezoelectric layer 3. The intermediate layer 12 consists of a low-melting-point solder, and the surface 11 of the second bearing area 8 facing the housing are the contact pads 26 of a circuit board 27. This circuit board is preferably made of ceramic, as shown in FIGS. 4A and 4B, or a circuit board material with a very high Tg. A (thick-film) heating element 28 is then preferably located directly below all contact pads 26 of the piezoelectric bending transducer 2, separated only by an electrically insulating layer. In this configuration, the heating element is in direct thermal contact with the intermediate layer 12, which can therefore melt within a few seconds.

[0064] FIG. 5 shows an example of a cross-sectional view of an embodiment of a piezoelectric actuator array 32, which includes a monomorph piezoelectric actuator 1 according to FIGS. 2B and 3A, implemented with a second bearing type LA2. The monomorph piezoelectric actuator 1 includes a piezoelectric bending transducer 2 with a thin piezoelectric layer 3 at its bottom. In this case, the centrally located bearing area 16 corresponds to the second bearing area 8, shown in dashed lines, while the lateral bearing area 17 corresponds to the first bearing area 7, also shown in dashed lines. The latter is achieved by firmly soldering the carrier layer 4 to the contacts of the circuit board 27. The elasticity of this first bearing area 7 is determined by the carrier layer in area 21, as shown in FIGS. 4A and 4B. The second bearing area 8 is located in the center of the piezoelectric bending transducer 2. The second bearing area is formed by an elastic and meltable intermediate layer 12, which has good adhesion to the piezoelectric bending transducer 2. A heating wire 28 runs transversely to all the piezoelectric bending transducers 2 within an insulating support structure, which is suitable for directly melting the intermediate layer 12 from the inside. In this configuration, the pressure element 24 for applying a biasing torque 34 around the first bearing area 7 is located on the right hand side of the drawing and has the form of a pressure spring array 24.

[0065] 6A shows a further embodiment of the second bearing area 8, in which the outermost part of the carrier layer 4 is bent and protrudes through a feedthrough in the circuit board 27. The intermediate layer 12 corresponds to the solder in the feedthrough. Furthermore, a heater 28 is located in a groove in the bottom of the circuit board.

[0066] 6B shows a further embodiment of the second bearing area 8, which comprises a meltable elastomer or elastic adhesive as an intermediate layer 12 on a circuit board 27. This intermediate layer 12 is heated by and in direct thermal contact with a heating layer 28 located immediately below the intermediate layer 12. An insulating layer 39 between the circuit board 27 and the housing 31 is also shown.

[0067] The fabrication of the piezo actuator array 32 is performed within a panel. A large number of piezo lamina 3, for example 16, 32, or 64, are each produced using a sawing process. The sawing process is performed on sawed lamina, pre-structured bending transducer carrier layers, and / or micro-effectors, which are produced from plates of the respective materials within the panel, i.e., they form a single, integrated part. These are then bonded together to the panel to form the monomorph or bimorph piezo bending transducer array 32, which is molded or glued to the panel with the connected elastic contact electrodes and the micro-effectors. Alternatively, the piezo lamina 3 and the pre-structured piezo bending transducer support structure can first be glued together and then sawed within the panel on the sawed lamina for further processing within the panel in a second step.

[0068] The method comprises the following steps: a manufacturing step in which one or more piezo actuator arrays 32 are fabricated from a multitude of panel-type piezo bending transducers 2 according to the invention, which are arranged side by side to form a coherent structure; an insertion step in which said structure is inserted into a print head or coating head; and finally an alignment step in which an alignment process according to the invention is carried out, in which all piezo actuators are aligned to their reference positions 40. The method is also characterized by the absence of any further alignment steps.

[0069] A piezo actuator 1 is proposed for performing an actuation movement 13. The piezo actuator 1 comprises a piezo bending transducer 2 consisting of a carrier layer 4, one or both sides of which are at least partially covered with a thin piezo layer 3, a movable end 6, and a housing 31. The piezo actuator 1 is characterized by: a reference stop 15 connected to the housing 31 and determining a reference position 40 for the actuation movement 13; a first bearing area 7 including the area of ​​the piezo actuator 1 and the area of ​​the housing 31 and allowing a torsion Φ1 of the piezo bending transducer 2; a second bearing area 8 having a surface 10 on the side of the bending transducer and a surface 11 on the side of the housing with an intermediate layer 12 between them, the intermediate layer 12 connecting these surfaces, the intermediate layer 12 being liquefiable; a pressure element 24 connected to the reference stop 15. against , a pressure element 24 for generating a biasing torque on the piezo bending transducer 2 around said first bearing area (7). [Explanation of symbols]

[0070] 1 Piezo Actuator (2 Piezo Bending Transducers + Housing 31 + Optional Effector 19) 2 Piezo bending transducers 3 Piezo thin layer 4 Carrier Layer 5. Fixed end of piezoelectric bending transducer 2 6 Movable end of piezoelectric bending transducer 2 7 First bearing area of ​​piezo actuator 1 8 Second bearing area of ​​piezo actuator 1 9 Support for first bearing area 7 10 surface of the second bearing area 8 facing the bending transducer 11 surface of the second bearing region 8 facing the housing 12 intermediate layer of second bearing region 8 13 Actuation movement at the movable end 6 of the piezoelectric bending transducer 2 14 Actuation point in contact with actuation element 15 Reference fastener 16 Centrally located bearing area 17 Laterally located bearing area 18 Connecting electrode 19 Effectors 20 Elastic connection 21 Elastic region of the second bearing region 22 Pivot point of first bearing area 23 Contact points of compressive force 24 pressure elements, pressure spring array 25 Retaining Bridge 26 contact pads 27 Circuit Board 28 heating element 29 Through-connection 30 adhesive wire 31 Housing 32 Piezo Actuator Array 33 Process Controller 34 Applying torque 37 Temperature Sensor 38 External heat source 39 Insulating layer 40 Reference position D1 deflection, working path D2 deflection, actuation path LR Distance between pivot point and actuation point L1 Distance between the central bearing and the moving end of the piezo bending transducer, free area L2 Distance between the center bearing and the side bearing Φ1 twist Φ2 twist R bending radius

Claims

1. A piezo actuator (1) for performing an actuation movement (13), comprising: a piezoelectric bending transducer (2) consisting of a carrier layer (4), one or both sides of which are at least partially covered with a thin piezoelectric layer (3); A movable end (6), Housing (31) and Equipped with A reference stop (15), connected to the housing (31); and a reference stop (15) for determining a reference position (40) for said actuation movement (13); A first bearing area (7), The piezoelectric actuator (1) includes a region of the housing (31), a first bearing area (7) that allows torsion (Φ1) of the piezoelectric bending transducer (2); A second bearing area (8), a surface (10) facing the bending transducer; a side surface (11) of the housing; an intermediate layer (12) between the surface (10) on the side of the bending transducer and the surface (11) on the side of the housing; and the intermediate layer (12) connects the surface (10) on the side of the bending transducer with the surface (11) on the side of the housing; the intermediate layer (12) being liquefiable, a second bearing region; A pressure element (24), a pressure element (24) for generating a biasing torque (34) on the piezoelectric bending transducer (2) around the first bearing area (7) relative to the reference stop (15); It is characterized by The piezo actuator (1) is operable in an operating mode and an alignment mode; In said operating mode, said piezo bending transducer (2) performing an actuation movement (13); the temperature of the intermediate layer (12) is below its liquefaction temperature; the intermediate layer (12) being sufficiently stiff to transmit bearing forces in the second bearing region (8); In the alignment mode, The piezoelectric bending transducer (2) is aligned with the reference stop (15) while the temperature of the intermediate layer (12) is raised above its liquefaction temperature by the application of heat. A piezoelectric actuator characterized by:

2. A piezo actuator (1) according to claim 1, In the alignment mode, the intermediate layer (12) liquefied by an external heat source (38), or It is liquefied using an integral heating element (28) in thermal contact with the second bearing area (8). Piezo actuator.

3. A piezo actuator (1) according to claim 2, so that the temperature in the second bearing region (8) rises above the melting temperature of the intermediate layer (12); The heating element (28) is controlled by a process controller; and The heat output can be calculated by the process controller; so that the intermediate layer (12) melts in a period of time on the order of 1 second, 10 seconds, or 100 seconds. The process controller calculates the heating time. Piezo actuator.

4. A piezo actuator (1) according to any one of claims 1 to 3, The intermediate layer (12) is made of a solder having a melting temperature below 150°C, 200°C, or 250°C; a piezo actuator electrically contacted by the solder either to the carrier layer (4) of the piezo bending transducer (2) or to the electrodes (18) of the piezo thin layer (3); or The intermediate layer (12) is made of a thermoplastic material, a thermoplastic elastomer, bitumen, or wax having a melting temperature below 100°C, 150°C, 200°C, or 250°C.

5. A piezo actuator (1) according to any one of claims 1 to 4, The piezo actuator (1) further comprises means for applying a biasing torque (34) to the piezo bending transducer (2) around the first bearing area (7); the movable end (6) of the piezoelectric bending transducer (2) or an effector (19) connected to the movable end (6) is pressed against a reference stop (15) as a result of the application of the biasing torque (34); Piezo actuator.

6. A piezo actuator (1) according to claim 5, The biasing torque (34) is applied by exerting a defined force (F) on the piezoelectric bending transducer (2) by a pressure element (24), a contact point (23) between the pressure element (24) and the piezoelectric bending transducer (2) is offset from a pivot point (22) of the first bearing area (7) by a lateral offset (x) along the piezoelectric bending transducer (2); The clamping force (F Ｋ ) and the level of the force (F) and the displacement (x) based on the distance (L) of the first bearing area (7) to the operating point (14) of the piezoelectric bending transducer (2). Ｒ ) and (F)*(x)<0.5*(F Ｋ )*(L Ｒ ) holds true Piezo actuator.

7. A piezo actuator (1) according to any one of claims 1 to 6, The piezoelectric bending transducer (2) monomorphically constructed with a single piezo thin layer (3) glued to the carrier layer (4), or It is constructed in a bimorphic manner by two of the piezo thin layers (3) glued on either side of the carrier layer (4), One or two of said piezo thin layers (3) are covering the carrier layer (4) mainly in the region of the free length (L1) of the piezoelectric bending transducer (2), or substantially completely covering the carrier layer (4) A piezoelectric actuator characterized by:

8. A method for aligning a piezo actuator (1) according to any one of claims 1 to 7, comprising: a) heating the intermediate layer (12) of the second bearing region (8) using a heat source to liquefy the intermediate layer; applying each voltage to be related to the position of the reference stop (15) to all electrodes of the piezo bending transducer (2); b) aligning said piezoelectric bending transducer (2) with respect to said reference stop (15) under the influence of said biasing torque (34) for the duration of an alignment time (TA); c) solidifying said intermediate layer (12) by cooling said second bearing area (8) during a cooling time (TK); It is equipped with These steps are performed in the order listed above. method.

9. 9. A method for aligning a piezo actuator according to claim 8, comprising: the voltages applied to all electrodes are corrected to compensate for deformation of the piezoelectric bending transducer under the biasing torque; method.

10. 10. A method for aligning a piezo actuator according to claim 9, comprising: In the step of applying the voltages to the electrodes of the piezoelectric bending transducer (2), A voltage different from the voltages applied during the most recently performed alignment step is applied. A method characterized by:

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