Piezoelectric actuator and piezoelectric actuator array

Abstract

A piezoelectric actuator 1 for performing an actuating movement 13 is proposed, which has a piezoelectric bending transducer 2 made of a carrier layer 4, which on one or both sides is at least partially covered with a piezoelectric sheet 3, which has a movable end 6 and a housing 31, which has a reference stop 15 connected to the housing 31 for determining a reference position 40 for the actuating movement 13, which has a first bearing region 7, which comprises the region of the piezoelectric actuator 1 and the housing 31 and allows a torsion Φ1 of the piezoelectric bending transducer 2, which has a second bearing region 8, which has a surface 10 on the side of the bending transducer and a surface 11 on the side of the housing and an intermediate layer 12 between these surfaces, which connects these surfaces and can be liquefied, and which has a pressure element 24 for generating a deflection torque 34 on the piezoelectric bending transducer 2 around the first bearing region 7 relative to the reference stop 15.

Description

Technical Field

[0001] This invention relates to a single piezoelectric bending transducer, as well as to arrangements of piezoelectric bending transducer arrays, so-called piezoelectric bending transducer arrays and their applications, and particularly to microvalves and microvalves arrays. Background Technology

[0002] The piezoelectric bending transducer array according to the invention is particularly useful for actuating microfluidic valve arrays in multi-channel printheads or coating heads having one or more rows of dispensing nozzles, which can be controlled individually or in groups to dispense droplets or liquid jets on a surface for color decoration purposes, or for CNC spraying one or more layers of liquid coatings (e.g., paints, varnishes, adhesives or sealants) with sharp outlines and no spraying, or for functional coating of components.

[0003] The corresponding printheads can potentially be used in painting, sealing, or bonding applications for various types of vehicles, such as motor vehicles, but also in aircraft and ships, primarily by using industrial robots (especially multi-axis flexor arm robots) to move the printhead or coating head, or in applications where industrial robots or Cartesian robots are used to coat any kind of components (including products in the consumer goods industry) with liquid paint, or integrated into single-pass printing or coating systems, as well as in all coating applications related to buildings.

[0004] Specifically, the aforementioned miniature valve array serves as a miniature pneumatic pilot valve array in a printhead or coating head of the aforementioned type, operating according to an electro-pneumatic principle, as described in EP 2 442 983 B1, for example. The components described herein demonstrate the functionality of the miniature pneumatic circuitry and actuator components described in EP 2 442 983 B1.

[0005] piezoelectric bending transducers from the prior art described herein (e.g.) Figure 1The piezoelectric bending transducer is primarily a specific length actuator firmly clamped to one side to generate actuating motion perpendicular to the longitudinal direction at its movable end, and is mainly flat and composed of multiple material layers having at least one piezoelectric layer. The longitudinal expansion caused by applying a voltage to one or more piezoelectric layers causes the bending transducer to bend perpendicular to the longitudinal direction due to the internal tension of the multilayer structure, resulting in a significantly larger deflection compared to the longitudinal expansion. This is used for actuation tasks, as the piezoelectric bending transducer either moves the actuating element directly at its first movable end (e.g., a microvalve) or via an effector. The deflection of the piezoelectric bending transducer increases with its length; the natural frequency of the first eigenmode is used for the actuation task, thus reducing the force and stiffness. The design goal of piezoelectric bending transducers is generally to maximize deflection, force, and the first natural frequency. The piezoelectric bending transducers described herein are designed for strokes of 20 μm, 50 μm, 100 μm, 200 μm, or higher, with distances between adjacent piezoelectric bending transducers ranging from, for example, 0.5 mm to, for example, 10 mm and above.

[0006] The constant reference position of the moving end of the piezoelectric bending transducer, or the effector connected thereto, relative to the actuating element of the microvalve, is crucial for defined operation. The actuating element of the microvalve is the moving element of the valve, for example, a closing element corresponding to the valve opening, thus forming a "valve" that allows the valve opening to close or open depending on the position of the actuating element. Due to the small deflections associated with the microvalve described above, adverse changes that may occur over time or are temperature-related in the piezoelectric bending transducer or its periphery (including the housing), such as mechanical expansion, deformation, or creep processes, can affect the reference position, i.e., the distance between the effector and the actuating element of the microvalve. A changing reference position alters the function of the microvalve. Conventional piezoelectric bending transducers are rigidly fixed to one side, for example, as... Figure 1 As shown, these changes cannot be compensated for in the long term.

[0007] As a solution, DE 10 2009 033 780 B4 proposes a piezoelectric bending transducer for pneumatic valves, which features a "floating bearing" or fluid bearing. Together with the deflection torque applied by the spring (pressing the piezoelectric bending transducer towards a reference position), the fluid bearing provides no resistance in the static state, thus continuously compensating for slowly occurring changes. However, by using a high-viscosity bearing fluid, rapid actuation encounters fluid resistance, making the fluid bearing associated with the actuation motion resemble a fixed bearing. However, a disadvantage of using a fluid bearing is that it cannot perform operations with static deflection; it is only suitable for pulsed operation.

[0008] In addition to the expectation that the actuation function will remain unchanged throughout its service life under the aforementioned adverse effects, the above applications also generally expect high operating frequencies (e.g., in the range of 500 Hz, 1 kHz, 2 kHz, 3 kHz, 4 kHz, or 5 kHz), high bending transducer deflection, high holding force, low electro-energizing operating voltage, minimal differences between adjacent piezoelectric bending transducers, and as long as possible unlimited service life and inexpensive mass production of piezoelectric bending transducer arrays and microvalve arrays. Summary of the Invention

[0009] Overall, the problem addressed by this invention is to create high-performance piezoelectric bending transducers for actuator arrays to extend their service life, particularly for the applications mentioned.

[0010] The problem is solved by a piezoelectric actuator having a piezoelectric bending transducer and a piezoelectric bending transducer array consisting of at least one row of piezoelectric bending transducers.

[0011] The piezoelectric actuators and piezoelectric actuator arrays thereof according to the present invention, including the disclosed embodiments, allow for continuous long-term operation.

[0012] According to a method for aligning a piezoelectric actuator, also claimed, an automatic alignment process of the piezoelectric actuator relative to the actuator is repeatedly performed to enable actuation of the actuating element (e.g., the closing element of a miniature valve) in a always reproducible manner. During the alignment process, the piezoelectric actuator, in this case, always returns to its reference or starting position relative to the actuating element to eliminate any undesirable changes in the piezoelectric element, actuating element, miniature valve, or housing region, and this state is frozen until the next alignment process. During the alignment process, the intermediate layer is briefly melted in the bearing region of the piezoelectric bending transducer, and the piezoelectric element enters a defined charging state. By applying an external force to the piezoelectric bending transducer, the moving end of the piezoelectric bending transducer or the effector connected thereto is moved relative to a reference stop (e.g., the closing element of a miniature valve). This state is then frozen by the solidification of the intermediate layer, and the piezoelectric actuator is once again in its reference position.

[0013] It should be noted that the alignment process according to the invention can be used in a variety of ways: for example, during the initial installation and / or startup of components, particularly printheads, coating heads, dosing heads, dispensing heads, liquid valves, or pneumatic valves, etc.; similarly, during maintenance, when modifying components for new applications, when changing or replacing peripheral components, and when changing the operating conditions of an existing configuration (e.g., by adapting it to the changed application or specification); particularly in the case of printheads or coating heads, when adapting them to different or changed coating agents or changed operating parameters (temperature, pressure, etc.), coating parameters (layer thickness, coating speed, dripping frequency, variations between dripping and jet coating); furthermore, after changing the position of a reference stop or when changing the charging state of the piezoelectric element of a piezoelectric actuator associated with the reference stop. In short, the alignment process according to the invention can be used in any situation where the piezoelectric actuator needs to be referenced to any type of new or changed conditions.

[0014] To enable the aforementioned alignment process, the piezoelectric actuator according to the present invention for performing actuation motion has the necessary means and methods: For this purpose, the piezoelectric actuator firstly has a piezoelectric bending transducer made of a carrier layer, one or both sides of which are at least partially covered with piezoelectric sheets; it also has a movable end for performing actuation motion; and a housing on which the piezoelectric bending transducer is mounted and an actuating element or actuating device (e.g., a miniature valve) is securely connected. The piezoelectric actuator according to the present invention is further characterized by a reference stop connected to the housing for determining a reference position for the actuation motion of the actuating element or actuating device; and further characterized by a first bearing region comprising the regions of the actuator and the housing, and allowing the piezoelectric bending transducer to twist. 1 becomes possible, and is further characterized by a second bearing region having a surface on the bending transducer side and a surface on the housing side, and an intermediate layer between these surfaces, the intermediate layer connecting the surfaces and being liquefiable (at low temperatures), and is finally characterized by a pressure element for generating a deflection torque relative to a reference stop on the piezoelectric bending transducer around the first bearing region.

[0015] The piezoelectric actuator according to the invention, having a piezoelectric bending transducer and a corresponding piezoelectric bending transducer array, firstly has a carrier layer conforming to the prior art of DE 10 2009 033 780 B4, which is covered on one side (“single state”) or both sides (“dual state”) by a piezoelectric sheet that at least partially covers / covers the carrier layer. The piezoelectric sheet also has a conventional metallization layer, for example, made of a silver-containing thick layer or thin film structure. Furthermore, the piezoelectric bending transducer (and the corresponding piezoelectric bending transducer array) has a movable end for performing an actuating motion, and a reference stop for determining a reference position associated with the actuating motion of the movable end of the piezoelectric bending transducer, and additionally has a first bearing region designed so that the piezoelectric bending transducer can rotate thereabout. It also has a second bearing region containing an intermediate layer between a surface located on the bending transducer side and a surface located on the housing side. In addition, it has a pressure element in the region of the first bearing region for generating a constant deflection torque on the piezoelectric bending transducer around the first bearing region, the pressure element being oriented such that the active end of the piezoelectric bending transducer or the effector connected thereto presses against the actuator or a reference stop associated with the microvalve.

[0016] In contrast to DE 10 2009 033 780 B4, the intermediate layer in this second bearing region is composed of a solid, but this solid can be temporarily fused (is fusible) to it. In one mode of operation, the intermediate layer in this second bearing region is in a solid aggregate state, and in different preferred variations, it either primarily functions as a fixed bearing or primarily functions as a rotatable bearing, thus resembling a bearing fixed at least in the direction of actuation of the piezoelectric bending transducer in terms of one or more translational degrees of freedom. In contrast to DE 10 2009 033 780 B4, the piezoelectric bending transducer therefore also allows for fixed deflection during operation.

[0017] In the first bearing type LA1, a second bearing region, which always includes an intermediate layer, supports the piezoelectric bending transducer over a larger area, such that this bearing region preferably functions stably in all six degrees of freedom of motion. See [link to previous section]. Figure 1 In the second bearing type LA2; this second bearing region is narrowly defined or designed as a point and is located at the end of the piezoelectric bending transducer opposite to the moving end of the piezoelectric bending transducer, see [link to relevant documentation]. Figure 2A-2B .

[0018] The piezoelectric bending transducer is further characterized by an operating mode and an alignment mode, wherein 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 strong to transmit bearing force in the second bearing region, and wherein in the alignment mode the piezoelectric bending transducer is aligned with a reference stop because the temperature of the intermediate layer is above its liquefaction temperature due to heating.

[0019] In the alignment mode, one or more alignment processes are performed, comprising the following steps: liquefying the intermediate layer of the second bearing region by heating it with a heat source in an interchangeable order, or applying voltages to all electrodes of the piezoelectric bending transducer, which should be relative to the position of the reference stop; in a subsequent step, at alignment time T A During the duration of the deflection torque, the piezoelectric bending transducer is aligned relative to the reference stop, and finally, through a cooling time t... k The intermediate layer is cured by cooling the second bearing region over a period of time. Therefore, in the step of curing the intermediate layer material, during curing, the surfaces on the curved transducer side and the housing side of the second bearing region are frozen relative to each other.

[0020] It should be noted that, prior to the step of curing the intermediate layer, the alignment time T should be within the range of, for example, 1 / 2 s [second], 1 s, 5 s, 10 s, 30 s, or 1 minute. A Within this, the intermediate layer must be present in a flowable state and a defined voltage must be applied to all electrodes of the piezoelectric bending transducer.

[0021] At the alignment time T A During the alignment process, if there is a positional deviation in the alignment of the piezoelectric bending transducer relative to the reference stop prior to the alignment process, the piezoelectric bending transducer rotates around the first bearing region in either the positive or negative direction. During the alignment process, the surface position of the bending transducer side changes relative to the fixed surface associated with the housing in the second bearing region, allowing liquefied material to flow into or out of the intermediate layer and into the gap between these surfaces. Finally, the positions of the two surfaces relative to each other are frozen during the curing process, and the piezoelectric bending transducer is in its reference alignment state.

[0022] The alignment process can be performed as a one-time process during the initial assembly of the piezoelectric bending transducer to bring it into reference alignment or reference position for the first time. In this case, the heat of fusion required to melt the intermediate layer can be provided, for example, by hot air or by a welding head.

[0023] Furthermore, the alignment process can be performed several times or at regular intervals throughout the lifespan of the printhead or coating head, such as annually, monthly, weekly, daily, or hourly. By performing the alignment process regularly, the piezoelectric bending transducer, and all piezoelectric bending transducers in the piezoelectric bending transducer array, can always operate precisely in its reference alignment for many years.

[0024] In addition to the resulting long-term stability, piezoelectric actuator-based and multi-channel printheads or coating heads containing one or more piezoelectric actuators show only minimal differences between individual channels after completion and the initial alignment process.

[0025] In this context, it is also recommended to continuously detect deviations in the printed image during printing or coating operations, or by testing the print output or coating (which can indicate differences between the channels of the printhead or coating head), as part of quality assurance, and to perform one or more timely alignment processes. For example, the printing or coating process can be specifically adjusted by enlarging or reducing the actuation area or by moving the actuation area of ​​the piezoelectric actuator. In this case, it is particularly desirable to perform the alignment process under a changing charging state, i.e., by applying a varying voltage to the electrodes of the piezoelectric bending transducer, compared to a more recent alignment process.

[0026] Therefore, it is recommended that the appropriate sequence for adjusting the printhead or coating head to adapt to the application or implementation of quality improvement measures include at least the following steps: a) dripping or spraying from the nozzle and / or performing test printouts or test coatings through the printhead or coating head; b) metrological, optical, or visual inspection and evaluation of the test printouts or test coatings, for example, by measuring layer thickness, outline sharpness, gloss, layer flatness, and detecting splatter or satellite droplets, or optically inspecting the delivery of dynamic droplets, including spray or dripping speed, attenuation process, and detecting coating agent deposition on the printhead (especially the nozzle exit); c) performing an alignment process, wherein the voltage applied to the electrodes of the piezoelectric bending transducer is different from that of the previous alignment process, or the position of the reference stop has changed compared to the previous alignment process. It should be noted that this can generally be considered as an iterative process, wherein the alignment process according to c) is preferably performed even before the first step according to a), and the iterative process is finally ended after step b) if satisfactory results have been produced.

[0027] If a repetitive alignment process is provided, preferably one or more heating elements have been securely integrated into the aforementioned printhead or coating head, which is preferably connected to the housing and in thermal contact with the surface of a second bearing region assigned to the housing. In this case, the voltage of the heating elements and the electrodes to be applied to the piezoelectric bending transducer can be controlled via a process controller. This may optionally be the same process controller that performs the entire control of the printing or coating process, or it may be subordinate to the aforementioned process controller. It should only be noted here that such control can be performed by simply specifying the heat output and duration or (preferably) by temperature control, preferably based on a temperature sensor's measurement of the actual temperature near the second bearing region.

[0028] The heat output from the heating element is preferably controlled by a process controller, such that the temperature in the second bearing region rises above the melting temperature of the intermediate layer, and the intermediate layer melts within a period of time on the order of 1 second, 10 seconds, or 100 seconds.

[0029] It must be mentioned here that an initial alignment process is performed during the initial assembly of the printhead or coating head or an assembly containing one or more piezoelectric actuators according to the invention. In this case, the intermediate layer can also be liquefied in alignment mode by an integrated heating element that is in thermal contact with the second bearing region. Alternatively, the intermediate layer can also be liquefied by an external heat source (such as hot air) or by a soldering iron that is in contact with the material of the intermediate layer or one of its adjacent surfaces.

[0030] For example, the intermediate layer may preferably comprise a solder with a melting temperature below 150°C, 200°C, or 250°C. It can also be used for electrical contact with the electrodes of the carrier layer or piezoelectric sheet of the piezoelectric bending transducer. Alternatively, the intermediate layer may comprise a hot-melt adhesive, thermoplastic material, thermoplastic elastomer (TPE), bitumen, or wax with a melting temperature below 100°C, 150°C, 200°C, or 250°C. It should be noted that the maximum temperature of the piezoelectric sheet of the piezoelectric bending transducer caused by heating should be kept sufficiently below the Curie temperature of the piezoelectric material. Therefore, it is generally preferred to use all materials with sufficiently low melting points as the intermediate layer, as they allow the intermediate layer material to melt without the maximum temperature of the piezoelectric sheet approaching the Curie temperature of the piezoelectric material. Using solder or thermoplastic material as the intermediate layer primarily results in a strong bond and directly eliminates torsional tolerances at the connection points. In this case, the required elasticity must be added separately in each bearing area. In the case of thermoplastic elastomers w (TPU, TPE), due to the elasticity of the material, the corresponding rotational tolerance of the second bearing region can already be achieved.

[0031] The alignment of the piezoelectric bending transducer relative to the reference stop is at alignment time T.A The duration is carried out under the action of the deflection torque. Therefore, the piezoelectric actuator according to the invention has means for applying a deflection torque to the piezoelectric bending transducer around the first bearing region, wherein the deflection torque is applied to press the active end of the piezoelectric bending transducer or the effector connected thereto against the reference stop.

[0032] A deflection torque is applied by applying a defined force F to the piezoelectric bending transducer using a pressure element, wherein the contact point between the pressure element and the piezoelectric bending transducer starts from the pivot point in the first bearing region and moves along the piezoelectric bending transducer by a lateral offset x. The clamping force F based on the piezoelectric bending transducer... K The distance L from the first bearing region to the actuation point of the piezoelectric bending transducer R The force F and the offset x are relative to the horizontal, and the following relationship applies: F * x < 0.5 * F K * L R The structural implementation of this force application will be described using embodiments based on the accompanying drawings.

[0033] It should be noted that the corresponding piezoelectric bending transducer 2 of the piezoelectric actuator according to the present invention can be constructed in a single state by a single piezoelectric sheet 3 bonded to the carrier layer 4, or it can be constructed in a dual state by two piezoelectric sheets 3 bonded to both sides of the carrier layer 4, wherein one or two piezoelectric sheets 3 cover the carrier layer (4) mainly in the region of the free length L1 of the piezoelectric bending transducer, or one or two piezoelectric sheets 3 substantially completely cover the carrier layer 4.

[0034] In addition to the aforementioned measures for ensuring, adjusting, 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 achieves significantly improved performance of the piezoelectric bending transducer compared to the prior art. This opens up applications with higher performance requirements and / or higher power densities. Conversely, without changing the application or actuation work, the control voltage can be reduced, thereby significantly reducing the voltage load and mechanical tension load on the piezoelectric element, which can significantly improve its long-term strength up to a certain fatigue strength level. The width of the piezoelectric bending transducer is reduced; therefore, in the case of printheads or coating heads, compared to the prior art, the channel width or the distance between the nozzles can be reduced or the print resolution increased while maintaining the actuation performance of each individual actuator or each pressure channel.

[0035] In a preferred embodiment, a piezoelectric actuator is characterized by an actuation point at its movable end, or an effector connected thereto, for performing actuating motion. Furthermore, it is characterized by a centrally located, narrowly defined bearing region comprising the actuator and housing regions, and also by a lateral, narrowly defined bearing region at the opposite end of the movable end, further comprising the actuator and housing regions. The central and lateral bearing regions each contain elasticity that allows for local rotation of the piezoelectric bending transducer of at least + / - 2°. In this case, the central bearing region is preferably located within the middle third of the piezoelectric bending transducer.

[0036] To clarify the terminology, it should be noted that the aforementioned bearing regions, "first bearing region" and "second bearing region," can respectively correspond to "bearing region located in the center" or "bearing region located on the side." Therefore, the terms "first bearing region" and "second bearing region" are based on their function and design, while the terms "bearing region located in the center" and "bearing region located on the side" are based on their location.

[0037] In the second bearing type LA2, the central bearing region is preferably located in the middle third of the piezoelectric bending transducer, and the lateral bearing regions are located at the ends of the piezoelectric bending transducer opposite to its movable end. Both are narrowly defined or designed as points and are designed to allow or permit rotational movement of the piezoelectric bending transducer caused by deformation of the transducer, rotating around the bearing without significant resistance. This bearing constellation results in the usable first eigenmode of the piezoelectric bending transducer, for example in... Figure 3A As shown in the image. (and) Figure 1 Compared to the conventional fixed clamping device for piezoelectric bending transducers, this one is characterized in that, for a given radius of curvature R and a given free length L1 of the piezoelectric bending transducer (with the same control voltage and deformation), a larger actuation path is achieved without increasing rigidity compared to a fixed-clamp piezoelectric bending transducer. Figure 3A D2 in the middle is replaced by Figure 1 The higher or larger actuation path is due to the fact that the deformation curve of the piezoelectric bending transducer has been torn in the centrally arranged bearing region. This will increase the end deflection D2, for example Figure 3A As shown. It should be noted that in the region of length L2, that is, between the bearing region located in the center and the bearing region located on the side, the piezoelectric bending transducer deflects in the opposite direction to the free length L1 region, which includes the movable end of the piezoelectric bending transducer.

[0038] Furthermore, the torque curve of the piezoelectric bending transducer installed in this way is longer than that of the previous one. Figure 1 The typical clamping device shown is more uniform, resulting in the greatest load on the clamping device. This is a common cause of pressure-related failures.

[0039] In order to Figure 3A The intrinsic mode of the piezoelectric bending transducer shown is made possible in the bearing region located at the center ( Figure 3B ) and the bearing area located on the side ( Figure 3C The piezoelectric bending transducer must be allowed to rotate according to its deformation curve, but must be firmly supported at least in the direction parallel to the actuation motion. Different technical solutions have been proposed for this purpose. For example, one option is to use a support fixed relative to the housing, and, for example, a fixed tip or linear contact element designed to protrude from the housing attachment portion, on which the piezoelectric bending transducer sits and is capable of performing a tilting motion outward from the plane of the piezoelectric sheet. In this case, the piezoelectric bending transducer must be pressed against the support with sufficient pressure to prevent it from being lifted, especially in higher actuation forces and / or highly dynamic operating modes. This pressure is applied via a movable spring-operated contact element (e.g., a metal helical spring, bending spring, electronic contact spring, or elastomeric element) in the corresponding bearing region on the side of the piezoelectric bending transducer opposite to the support.

[0040] In addition to combining the support with the pressure element, point-type, rotatable support for the piezoelectric bending transducer can be achieved because the corresponding bearing areas provide basic translational fixation. To obtain the required rotational movement according to the bending curve of the piezoelectric bending transducer in the bearing areas located at the center and sides, it is further proposed that these bearing areas contain elasticity to allow rotational movement about the corresponding (possibly virtual) pivot points of the respective bearing areas.

[0041] These can be, for example, elastomers within the respective bearing regions of a piezoelectric bending transducer, such as discrete elastic elements or structural elastic regions of a carrier layer associated with the corresponding bearing region and partially not covered by piezoelectric sheets. For example, this could be a region of the carrier layer that protrudes laterally from one or two piezoelectric sheets (for bearing regions located on the side). The aforementioned elastomers can also be elastic intermediate layers made of the elastomeric material of the corresponding bearing region. Furthermore, they can be elastomers associated with the housing, or additional elastomers or spring-like components connected to the housing between the housing and the corresponding bearing region. These elastomers are configured such that they allow, at least to a small extent, local rotation of the piezoelectric bending transducer within the region of the corresponding bearing region. Specific embodiments described herein will be used with reference to the accompanying drawings.

[0042] Regarding the size ratio, 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 L1 / L2 ratio is preferably between 0.5 and 2. At least one piezoelectric sheet may cover the carrier layer primarily in the region of the free length L1 or in regions L1 and L2 (i.e., on both sides of the respective central bearing region). The latter case is only meaningful for LA2 bearing type and results in the greatest deflection.

[0043] The corresponding piezoelectric actuator array preferably comprises the same piezoelectric actuators according to the invention, each having a corresponding piezoelectric bending transducer. Depending on the type of application, they are preferably spaced at a constant distance between each other between 0.5 mm and 1 mm, 0.75 mm and 2 mm, or 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, 0.1 mm and 0.3 mm, or 0.2 mm and 0.6 mm. Furthermore, the first and second bearing regions of the corresponding piezoelectric bending transducers, or the bearing regions located at the center and sides, are respectively located on a line.

[0044] Furthermore, in the piezoelectric actuator array, the contact point of the pressure element, the pivot point of the corresponding bearing area, and the actuation point of each piezoelectric bending transducer are all located on a straight line.

[0045] Furthermore, the piezoelectric actuator array preferably includes a component comprising at least all piezoelectric bending transducers and bearing regions, including the bearing region associated with the housing. For this purpose, it is advantageous to use torsional elastic connections (e.g., in respective first bearing regions) between adjacent piezoelectric bending transducers of the array.

[0046] Furthermore, the aforementioned components (e.g., supports and pressure springs) associated with the housing of the corresponding first bearing region and the aforementioned components associated with the housing of the corresponding second bearing region are preferably constructed of structural plates.

[0047] Definition: The term "bearing region" refers to all components related to the bearing, or connected to it, that effectively affect the bearing performance, whether for a stationary or rotating bearing, between a point, narrow or wide area of ​​the piezoelectric bending transducer and a portion of the housing 31. This is taken into consideration that rotating bearings are sometimes achieved through elasticity within the bearing region, which is effective for this purpose.

[0048] As a precaution, it should be noted that the numbers used herein (“first,” “second,” ...) are primarily (only) used to distinguish multiple similar objects, sizes, or processes; that is, in particular, they do not necessarily specify any dependency and / or order of said objects, sizes, or processes relative to each other. If dependency and / or order are required, they will be explicitly stated herein or will be obvious to those skilled in the art when studying the specifically described embodiments. Attached Figure Description

[0049] The invention and technical environment will be explained in more detail below using the accompanying drawings. It should be noted that the invention should not be limited to the described embodiments. In particular, unless explicitly stated otherwise, aspects may be extracted from the facts described in the drawings and combined with other components and insights from this specification and / or the drawings. In particular, it must be noted that the drawings and, in particular, the scales depicted are merely illustrative. The same reference numerals denote the same objects; therefore, descriptions from other drawings may be used supplementarily, if necessary. In the drawings:

[0050] Figure 1 A schematic diagram of a piezoelectric actuator 1 according to the first bearing type LA1 is shown.

[0051] Figure 2A A schematic diagram of a piezoelectric actuator 1 according to the second bearing type LA2 is shown, wherein the first bearing region 7 is located at the center of the piezoelectric bending transducer 2, and the second bearing region 8 is located on the side of the fixed end 6 and is designed to be narrow.

[0052] Figure 2B A schematic diagram of a piezoelectric actuator 1 according to the second bearing type LA2 is shown, wherein the second bearing region 8 is located in the center and the first bearing region 7 is located on the side of the fixed end 6 of the piezoelectric bending transducer 2.

[0053] Figure 3A A schematic diagram of a piezoelectric actuator 1 according to the second bearing type LA2 is shown, with an enlarged view of a specific intrinsic mode of a deflecting piezoelectric bending transducer 2. Figure 3B and 3C A further enlarged view of the bearing region 16 located in the center and the bearing region 17 located on the side is shown.

[0054] Figure 4A This is a top view of an embodiment of a piezoelectric actuator array consisting of piezoelectric actuators 1; Figure 4B A cross-sectional view is shown.

[0055] Figure 5 A cross-sectional view of another embodiment of a piezoelectric actuator array consisting of piezoelectric actuator 1 is shown.

[0056] Figure 6A and 6B Another embodiment of the second bearing region 8 is shown.

[0057] Reference tag list

[0058] 1. Piezoelectric actuator (piezoelectric bending transducer 2 + housing 31 + optional effector 19)

[0059] 2. Piezoelectric bending transducer

[0060] 3. Piezoelectric film

[0061] 4. Carrier layer

[0062] 5. Fixed end of piezoelectric bending transducer 2

[0063] 6. Movable end of piezoelectric bending transducer 2

[0064] 7. First bearing region of piezoelectric actuator 1

[0065] 8. Second bearing region of piezoelectric actuator 1

[0066] 9 Support of the first bearing area 7

[0067] 10. The surface of the second bearing region 8 on the side of the bent transducer.

[0068] 11. The surface of the second bearing region 8 on the housing side

[0069] 12. Intermediate layer of the second bearing region 8

[0070] 13 Actuation movement of the movable end 6 of the piezoelectric bending transducer 2

[0071] 14. Actuation point in contact with the actuating element

[0072] 15 Reference stop

[0073] 16. Bearing area located in the center

[0074] 17. Bearing area located on the side

[0075] 18 Connecting electrodes

[0076] 19 Effectors

[0077] 20 Flexible connectors

[0078] 21. Elastic region of the second bearing area

[0079] 22 Pivot point of the first bearing area

[0080] 23 Pressure contact points

[0081] 24. Pressure elements, pressure spring array

[0082] 25 Fixed bridge

[0083] 26 Contact pads

[0084] 27 Circuit Board

[0085] 28 Heating element

[0086] 29. Through connection

[0087] 30 bond wire

[0088] 31. Shell

[0089] 32 piezoelectric actuator array

[0090] 33 Process Controller

[0091] 34 yaw torque

[0092] 37 Temperature sensor

[0093] 38 External heat source

[0094] 39 Insulation layer

[0095] 40 Reference Position

[0096] D1 deflection, actuation path

[0097] D2 deflection, actuation path

[0098] L R Distance between pivot point and actuation point

[0099] The distance between the L1 center bearing and the moving end of the piezoelectric bending transducer, free area

[0100] Distance between L2 center bearing and side bearing

[0101] 1. Twist

[0102] 2. Reversal

[0103] R (radius of curvature) Detailed Implementation

[0104] Figure 1A schematic diagram of a piezoelectric actuator 1 is shown. The piezoelectric actuator 1 includes a piezoelectric bending transducer 2, which is deflected D1 at its movable end 6. In this case, the movable end 6 also represents an actuation point 14 in contact with any actuator, preferably a closing element of a miniature valve. A first bearing region 7, rotatable within a limit of + / -5°, is also shown. The first bearing region 7 is configured as a support 9 representing a pivot point 22 and is also connected to a housing 31. The distance between the pivot point 22 and the actuation point of the first bearing region 7 is L. R A second bearing region 8 is also shown, which extends laterally along the piezoelectric bending transducer, and an intermediate layer 12 made of a liquefiable or fusible material is provided between the surface 10 of the second bearing region 8 on the piezoelectric bending transducer side and the surface 11 on the housing side.

[0105] Due to its extensive extension, the second bearing region 8 in this embodiment generally serves as a fixing clamp, and in this case, the bearing having this characteristic represents the first bearing type (LA1). However, as shown, the deflection torque 34 caused by the downward force F acting on the contact point 23 still permanently acts on the piezoelectric bending transducer 2 around the first bearing region 7, which is located at a distance x offset from the pivot point 22 along the bending transducer of the first bearing region 7. The magnitude of the deflection torque 34 should be determined such that it applies a small, constant moment load to the piezoelectric bending transducer 2, sufficient to cause it to rotate relative to the reference stop 15 in the event of melting (i.e., powerlessness) the intermediate layer 12, which defines the reference position 40 of the actuation movement 13 of the piezoelectric bending transducer 2. As described above, the intermediate layer 12 can be liquefied in alignment mode by melting the intermediate layer 12. For example, it can be melted by providing heat from an external heat source 38 in the form of hot air supply during installation or by using a soldering iron. As described above, the alignment process can also be repeated with brief interruptions during operation by interacting with a control device that performs optional temperature control via a temperature sensor 37 using an integrated heating element 28. In this case, the heating element 28 and the temperature sensor 37 are connected, for example, to the housing 31 and are in close thermal contact with the second bearing region 8. A possible insulating layer 39 below the heating element to prevent excessive heat from flowing into the housing 31 is not shown here.

[0106] Figure 2A A schematic diagram of the piezoelectric actuator 1 according to the second bearing type (LA2) is shown. To avoid repetition, refer to... Figure 1 The description is as follows; in the following text, only the differences will be described. The second bearing type is similar to... Figure 1The difference between the first bearing type (LA1) and the second bearing region 8 is that the second bearing region 8 is spatially narrowly defined and designed to perform rotational motion within a small range, such as + / -2°. Figure 1 Instead, replace with a rotary bearing Figure 1 The fixed bearing in the second bearing region 8 results in different bending curves for the piezoelectric bending transducer 2, which allows for the realization of a piezoelectric actuator 1 with higher actuation force. Figure 1 and 2A In the diagram, the first bearing region 7 corresponds to the centrally located bearing region 16 of the second bearing type (see [reference]). Figure 3A , 3B ), and the second bearing region 8 containing the intermediate layer 12 corresponds to the side bearing region 17 of the second bearing type LA2 (see Figure 3A , 3C ).

[0107] Figure 2B A second option for implementing the second bearing type LA2 is shown, which is consistent with... Figure 2A The difference between the options shown is that the first bearing region 7 corresponds to the side bearing region 17 of the second bearing type, and the second bearing region 8, which includes the intermediate layer 12, corresponds to the center bearing region 16 of the second bearing type LA2. Again, refer to Figure 1 and Figure 2A To avoid repetition, only the differences will be described.

[0108] It should be mentioned that, such as Figure 2B The order of the bearing regions can also be transferred to the first bearing type LA1. However, the difference between the bearing types is again that in bearing type LA1, the second bearing region 8 is designed to be wide and serves as a fixed bearing.

[0109] Figure 3A The bending curve of the piezoelectric bending transducer 2 according to the second bearing type LA2 is shown. This represents the first intrinsic mode of the piezoelectric bending transducer 2 under the marginal conditions of the bearing region 16 located at the center and the bearing region 17 located on the side, both of which can withstand the 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 covered with piezoelectric sheets on one side (single state) or both sides. In this document, L1 represents the free length L1 of the piezoelectric bending transducer 2, which defines the length of free movement of the piezoelectric bending transducer 2 between the bearing region 16 located at the center and the movable end 6. The fixed end 5 of the piezoelectric bending transducer 2 is fixed to the bearing region 17 located on the side. To compare the actuation path at the movable end 6 with that of the piezoelectric bending transducer 2, the following diagram is provided. Figure 1 The difference between the piezoelectric bending transducer 2 of the first bearing type LA1 in the model is assumed to be based on... Figure 1The piezoelectric bending transducer 2 is constructed in its free region L1 and Figure 3A The piezoelectric actuator 1 in both is the same. Therefore, the radius of curvature of both in the deflection state is R. It can be seen that, under the same radius of curvature, the deflection D2 produced in the case of the second bearing type LA2 is much higher than that in the case of the first bearing type LA1.

[0110] Figure 3B and Figure 3C The piezoelectric bending transducer 2 is shown in the bearing region 16 located at the center. Figure 3B ) and the bearing area 17 located on the side ( Figure 3C A further magnified view of the deformation at () to show the torsion. 1 and 2. During operation, they typically move within a range of + / -2 degrees.

[0111] For example, Figure 4A and 4B An embodiment of a piezoelectric actuator array 32 is shown, which has a second bearing type LA2 and according to Figure 2A and Figure 3A This is an embodiment of a dual-state piezoelectric actuator 2 with a constructed and installed configuration. In this case, the bearing region 16 located at the center corresponds to... Figure 4B The first bearing region 7, shown by the dashed line, uses a support 9 as a pivot bearing, and the adjacent bearing region 17 corresponds to the second bearing region 8, for actuating motion 13 at the movable end 6 of the piezoelectric bending transducer 2. At the movable end 6 shown on the left, an effector 19 is provided, with an actuation point 14 at its tip. The effector 19 is preferably connected to the piezoelectric bending transducer 2 via an elastic connector 20, which in this case can be, for example, an elastomer intermediate or an elastic adhesive. The elastic connector 20 reduces the impact transmission from the actuation point 14 to the piezoelectric bending transducer 2 and simultaneously provides a certain rotational tolerance for the effector 19.

[0112] In this embodiment, the deflection torque 34 is applied via a pressure element 24 or an array 24 thereof located below the fixed bridge 25. The pressure element 24 is tongue-shaped and optionally a bent pressure spring bar. The springs can have any meaningful shape, but can be shaped such that they apply the force F to the respective piezoelectric bending transducers 2 precisely at the contact point 23. For this purpose, they may optionally each have a separate pressure element.

[0113] The electrical contact of the piezoelectric bending transducer 2 requires that all piezoelectric sheets 3 on the upper side be in contact with an operating voltage VDD, for example, 100V to 200V, and all piezoelectric sheets 3 on the lower side be in contact with ground (GND). This is accomplished on the upper and lower sides using one or more connected connecting electrodes 18 that extend laterally to the piezoelectric bending transducer 2 and are applied as contact strips or contact lines, for example, made of copper, brass, nickel, or a thin flexible circuit carrier material, by pressure welding or adhesive bonding during the manufacturing process of the piezoelectric actuator array 32.

[0114] A second bearing region 8, including the intermediate layer 12, is located at the fixed (right) end 5 of the piezoelectric bending transducer 2. One embodiment is shown in which the carrier layer 4 comprises a solderable material such as nickel, copper, or brass. Therefore, the second bearing region 8 includes a region of the carrier layer 4 that is not covered by the piezoelectric sheet 3 and represents the elastic region 21 of the second bearing region 8. Due to the relatively small thickness of the carrier layer 4, for example, from 30µm to 100µm, sufficient bending elasticity is already present, such that… Figure 3A The curved lines shown in the diagram become possible. Figure 4A It is shown that the carrier layer 4 is designed to be narrower in the elastic region 21, which results in a reduction of the bending force in the elastic region 21.

[0115] exist Figure 4A and 4B In this embodiment, the surface 10 of the second bearing region 8 on the bending transducer side is the side surface of the carrier layer 4 of the piezoelectric bending transducer 2, which is not covered by the piezoelectric sheet 3. The intermediate layer 12 is composed of a low-melting-point solder, and the surface 11 of the second bearing region 8 on the housing side is the contact pad 26 of the circuit board 27. The latter is preferably made of, for example, Figure 4A and 4B The material is made of ceramic, or of a circuit board material with a very high Tg. The (thick film) heating element 28, separated only by an electrically insulating layer, is preferably located directly below all the contact pads 26 of the piezoelectric bending transducer 2. In this configuration, there is direct thermal contact with the intermediate layer 12, allowing it to melt within seconds.

[0116] Figure 5 An example cross-section of a piezoelectric actuator array 32 according to an embodiment is shown. The piezoelectric actuator array 32 has a single-state piezoelectric actuator 1, which has a piezoelectric bending transducer 2. The piezoelectric bending transducer 2 has a piezoelectric sheet 3 below it, and according to the second bearing type LA2 and... Figure 2B and 3AConfiguration and installation. In this case, the central bearing region 16 corresponds to the second bearing region 8 shown by the dashed line, and the side bearing region 17 corresponds to the first bearing region 7 shown by the dashed line. The latter is achieved by firmly soldering the carrier layer 4 to the contacts of the circuit board 27. Figure 4A and 4B As shown, the elasticity of the current first bearing region 7 is represented by the carrier layer in region 21. The second bearing region 8 is located at the center of the piezoelectric bending transducer 2. The second bearing region is formed by an elastic, fusible intermediate layer 12, which has good adhesion to the piezoelectric bending transducer 2. The heating wires 28, which extend laterally within the insulating support structure to all piezoelectric bending transducers 2, are suitable for melting the intermediate layer 12 directly from the inside. In this configuration, pressure elements 24, in the form of a pressure spring array 24, for applying a deflection torque 34 around the first bearing region 7, are located on the right side of the figure.

[0117] Figure 6A A variation of the second bearing region 8 is shown, in which the furthest portion of the carrier layer 4 bends and protrudes through a through-connection in the circuit board 27. The intermediate layer 12 corresponds to the solder in the through-connection. Additionally, the heater 28 is located in a recess at the bottom of the circuit board.

[0118] Figure 6B A variation of the second bearing region 8 is shown, which uses a fusible elastomer or elastic adhesive as an intermediate layer 12 on the circuit board 27. It is heated by a heating layer 28 located directly beneath the intermediate layer 12 in direct thermal contact. An insulating layer 39 between the circuit board 27 and the housing 31 is also shown.

[0119] The piezoelectric actuator array 32 is manufactured in the panel. Multiple piezoelectric sheets 3 (e.g., 16, 32, or 64) are fabricated from plates of corresponding materials in the panel using sawing processes on saw foil and / or pre-constructed bent transducer carrier layers and / or micro-effects, respectively, i.e., manufactured such that they each form coherent components. They are then joined together in the panel to form a single-state or dual-state piezoelectric bent transducer array 32, and molded or glued to the panel with connected resilient contact electrodes and with micro-effects. Optionally, the piezoelectric sheets 3 and the pre-constructed piezoelectric bent transducer support structure may first be bonded to each other and sawn only in the panel on saw foil in a second step for further processing in the panel.

[0120] The method includes the steps of generating one or more panel piezoelectric actuator arrays 32 from a plurality of piezoelectric bending transducers 2 according to the invention, the piezoelectric bending transducers 2 being arranged side-by-side and forming an adhesive structure, inserting said structure into a printhead or coating head, and finally performing an alignment process according to the invention, wherein all piezoelectric actuators are aligned at their reference positions 40. The method is further characterized in that no further alignment is required.

[0121] A piezoelectric actuator 1 for performing actuation motion 13 is proposed, comprising a piezoelectric bending transducer 2 made of a carrier layer 4, wherein piezoelectric sheets 3 are at least partially covered on one or both sides of the carrier layer 4, wherein the piezoelectric bending transducer 2 has a movable end 6 and a housing 31, having a reference stop 15 connected to the housing 31 for determining a reference position 40 for actuation motion 13, and having a first bearing region 7, the first bearing region 7 including the area of ​​the piezoelectric actuator 1 and the housing 31 and allowing torsion of the piezoelectric bending transducer 2. 1. It has a second bearing region 8, which has a surface 10 on the bending transducer side and a surface 11 on the housing side, and an intermediate layer 12 between these surfaces, connecting these surfaces and which can be liquefied, and has a pressure element 24 for generating a deflection torque 34 on the piezoelectric bending transducer 2 around the first bearing region 7 relative to the reference stop 15.

Claims

1. A piezoelectric actuator (1) for performing actuation motion (13). It has a piezoelectric bending transducer (2) made of a carrier layer (4), which is at least partially covered on one or both sides by piezoelectric sheets (3), has a movable end (6), and has a housing (31). Its features are, - A reference stop (15) connected to the housing (31) is used to determine a reference position (40) for the actuation movement (13). - The first bearing region (7) includes the area of ​​the piezoelectric actuator (1) and the housing (31) and allows the piezoelectric bending transducer (2) to be torn ( 1), - A second bearing region (8) having a surface (10) on the bending transducer side and a surface (11) on the housing side, and an intermediate layer (12) between the surface (10) on the bending transducer side and the surface (11) on the housing side, wherein the intermediate layer (12) connects the surface (10) on the bending transducer side and the surface (11) on the housing side, wherein the intermediate layer (12) is liquefiable. - and pressure element (24), which is used to generate deflection torque (34) relative to the reference stop (15) around the first bearing region (7) on the piezoelectric bending transducer (2); The piezoelectric actuator (1) is operable in both operating mode and alignment mode. In this operation mode, the piezoelectric bending transducer (2) performs an actuation motion (13), the temperature of the intermediate layer (12) is below its liquefaction temperature, and the intermediate layer (12) is sufficiently robust to transmit bearing force in the second bearing region (8). Furthermore, in the alignment mode, the piezoelectric bending transducer (2) is aligned with the reference stop (15) because the temperature of the intermediate layer (12) is higher than its liquefaction temperature due to the heat supply. Furthermore, the intermediate layer (12) is liquefied in the alignment mode by an external heat source (38) or by an integrated heating element (28) in thermal contact with the second bearing region (8); Furthermore, the contact point (23) between the pressure element (24) and the piezoelectric bending transducer (2) is offset by a lateral offset x from the pivot point (22) of the first bearing region (7) along the piezoelectric bending transducer (2).

2. The piezoelectric actuator (1) according to claim 1, characterized in that, The heating element (28) is controlled by a process controller and the heat output is evaluated by the process controller to raise the temperature in the second bearing region (8) above the melting temperature of the intermediate layer (12), wherein the process controller evaluates the heating time to make the intermediate layer (12) melt within a time period on the order of 1 second, 10 seconds or 100 seconds.

3. The piezoelectric actuator (1) according to claim 1, characterized in that, The intermediate layer (12) is composed of solder with a melting temperature below 150°C, 200°C or 250°C, wherein the carrier layer (4) of the piezoelectric bending transducer (2) or the electrode (18) of the piezoelectric sheet (3) is electrically contacted through the solder, or wherein the intermediate layer (12) is composed of thermoplastic material, thermoplastic elastomer, asphalt or wax with a melting temperature below 100°C, 150°C, 200°C or 250°C.

4. The piezoelectric actuator (1) according to claim 3, characterized in that, The deflection torque (34) is applied by applying a defined force F to the piezoelectric bending transducer (2) using the pressure element (24). Furthermore, regarding the clamping force F based on the piezoelectric bending transducer (2) k The distance L from the first bearing region (7) to the actuation point (14) of the piezoelectric bending transducer (2) R The force F and the offset x are horizontal, subject to the following condition: (F)*(x)<0.5*(F) K )*(L R ).

5. The piezoelectric actuator (1) according to claim 1, characterized in that, The piezoelectric bending transducer (2) is constructed in a single state by a single piezoelectric sheet (3) bonded to the carrier layer (4), or in a dual state by two piezoelectric sheets (3) bonded to both sides of the carrier layer (4), wherein the single or two piezoelectric sheets (3) mainly cover or substantially completely cover the carrier layer (4) in the region of the free length (L1) of the piezoelectric bending transducer (2).

6. A method for aligning a piezoelectric actuator, characterized in that, The piezoelectric actuator is a piezoelectric actuator (1) according to any one of claims 1-5, and the method has the following steps in an interchangeable order: a) Liquefy the intermediate layer (12) of the second bearing region (8) by heating it with a heat source, or by applying voltages to all the electrodes of the piezoelectric bending transducer (2) relative to the position of the reference stop (15). b) The piezoelectric bending transducer (2), under the action of the deflection torque (34), during the alignment time (T) A Alignment with the reference stop (15) for the duration of the duration. c) By controlling the cooling time (T) K During this period, the second bearing region (8) is cooled to solidify the intermediate layer (12).

7. The method for aligning a piezoelectric actuator according to claim 6, characterized in that, When the reference stop does not represent the position during normal operation, the voltage applied to all electrodes is corrected to compensate for the deformation of the piezoelectric bending transducer under the deflection torque.

8. The method for aligning a piezoelectric actuator according to claim 7, characterized in that, In the step of applying the voltage to the electrodes of the piezoelectric bending transducer (2), the applied voltage is different from the voltage applied during the recent alignment process.

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