Mounting device for piezoelectric motor elements

Abstract

A piezoelectric actuator is described that includes a piezoelectric motor element having a top surface and a bottom surface, and a connecting element that includes an arm having a flexure hinge for contacting the piezoelectric motor element at different fixed positions located at node positions of a bending mode of the piezoelectric motor element, the flexure hinge allowing the piezoelectric motor element to move in a normal direction and such that the flexure hinge is rigid in a tangential direction, whereby the flexure arm is fixed to the piezoelectric motor element by a fixing means.

Description

Technical Field

[0001] Field of the Invention The present invention relates to piezoelectric motors, such as ultrasonic piezoelectric motors, and methods of attaching elements of piezoelectric motors. More particularly, the present invention relates to methods and systems for connecting or attaching piezoelectric motor elements, such as ultrasonic piezoelectric motor elements, to stator components of a positioning device.

Background Art

[0002] Background of the Invention Piezoelectric actuators are often used in many applications that require a high degree of miniaturization. However, the greatest limitation of a typical piezoelectric positioner is that the displacement is very small. To counter this effect, several principles of piezoelectric motors with unlimited stroke have been presented.

[0003] Three main types of piezoelectric motors, namely, (1) stepping motors, (2) stick-slip / inertia drive motors, and (3) resonant motors, are designed with infinite stroke. Stepping motors have high holding force but are often too slow for many applications. Stick-slip motors achieve speeds of about 10 mm / s but often cause excessive vibration. Resonant motors, often called "ultrasonic" because of their high operating frequencies, conversely achieve peak speeds of about 100 mm / s or more. This is because the piezoelectric elements of resonant motors are excited by drive signals at frequencies close to the two natural frequencies of the motor. A typical piezoelectric motor has, for example, longitudinal and transverse movement natural modes with approximately matching frequencies.

[0004] Small ultrasonic piezoelectric motors are characterized by high power efficiency compared to electric motors of the same size. Due to their compactness and efficiency, they are often used in handheld devices. Ultrasonic piezoelectric motors are quiet motors due to their high-frequency operation. Another advantage of these motors is the absence of transmission systems such as gears or belts. Therefore, the operating mechanism is not very complex and there is no mechanical backlash. This means that these motors can achieve better positioning accuracy. Even when shut down, these motors still exert holding force, so the position of the moving sample is fixed. Some applications also require that the operation be reversible. This means that the sample can still be moved manually, limiting the effects of hard impacts, for example, when it hits a hard target. Like other piezoelectric motors, ultrasonic piezoelectric motors are often used in specific environments such as high vacuum or ultra-high vacuum, when avoiding magnetic fields, and cryogenic environments. However, these motors are also used in applications in the atmosphere, typically when both miniaturization and high speed are required.

[0005] Several ultrasonic motors that operate using resonant vibration modes have been designed over the past few years, but they still have some drawbacks.

[0006] Japanese Patent Publication No. 7-107758 discloses an ultrasonic actuator that applies high-frequency voltages of different phases to two sets of electromechanical energy converters. A standing wave vibration is generated in a resonator, and the node portion of this standing wave vibration is fixed by a holding means using an elastic hinge structure.

[0007] European Patent Application Publication No. 0978886 discloses an ultrasonic motor intended to reduce leakage of driving force generated by a piezoelectric element and efficiently transmit the driving force to a moving member. The ultrasonic motor comprises a piezoelectric element that vibrates in response to an input drive signal to generate driving force, and a support member that supports the piezoelectric element on a substrate. The support member has a signal supply function that supplies a drive signal to the piezoelectric element. As a result, there is no need to provide a separate signal transmission means, and vibrations caused by the piezoelectric element are less likely to leak than in conventional configurations. As a result, the ultrasonic motor efficiently transmits the driving force to the moving member. Furthermore, the support member has elasticity due to its constriction, and therefore also has a pressure-contact function that presses the piezoelectric element against the moving member. In this case, vibration leakage is further reduced.

[0008] Nevertheless, there is still a demand for small ultrasonic piezoelectric motors and piezoelectric motors that are easy to install. [Overview of the Initiative] [Problems that the invention aims to solve]

[0009] Summary of the Invention The object of the present invention is to provide a good mounting system and method for mounting elements of an ultrasonic piezoelectric motor. [Means for solving the problem]

[0010] An advantage of the embodiments of the present invention is that the motor element is held in a fixed position by eliminating the appropriate degrees of freedom of the piezoelectric motor element. An advantage of the embodiments of the present invention is that the degrees of freedom of all but one of the piezoelectric motor elements are eliminated. An advantage of the embodiments of the present invention is that the motor can move in a direction perpendicular to the sliding direction in order to generate a preload between the motor's drive contacts and the traction surface of the positioning device.

[0011] An advantage of the embodiments of the present invention is that preload can be applied by a mechanical spring component, and the present invention is not limited thereto.

[0012] An advantage of the embodiments of the present invention is that the mounting does not interfere with the ultrasonic drive vibrations generated when the piezoelectric motor is excited at its resonant frequency. Another advantage of the embodiments of the present invention is that the fixing points are selected such that there is no or minimal interaction with the natural modes of the piezoelectric motor at resonance. The latter results in good force and travel speed for the positioning device.

[0013] Fixed points are the locations where the piezoelectric element is fixed to other elements. Aside from the drive contacts, these are the only locations where the piezoelectric element makes contact with the surrounding elements.

[0014] An advantage of the embodiments of the present invention is that the method and system have no or minimal play or backlash in the motor's driving direction.

[0015] An advantage of the embodiments of the present invention is that the mounted motor elements are realized in a very compact manner, resulting in a compact system.

[0016] An advantage of the embodiments of the present invention is that the mounting of the motor elements can be achieved by inexpensive manufacturing processes such as punching or laser cutting, resulting in low manufacturing costs. Another advantage of the embodiments of the present invention is the short assembly time.

[0017] An advantage of the embodiments of the present invention is that a method and system are provided that provides symmetry and reduces the influence on motor resonance modes. An advantage of the embodiments of the present invention is that good thermal stability of the resulting positioning system is obtained. An advantage of the embodiments of the present invention is that great symmetry of the apparatus is obtained and stability is improved.

[0018] The present objective and optionally one or more advantages are satisfied by the mounting method and resulting system according to the independent claims of the present invention. Dependent claims relate to preferred embodiments.

[0019] The present invention relates to a piezoelectric actuator, for example, an ultrasonic piezoelectric actuator, wherein the piezoelectric actuator comprises a piezoelectric motor element having a top surface and a bottom surface, A connecting element comprising an arm having a bending hinge for fixing a piezoelectric motor element at different fixed positions located at the node positions of one or more bending modes of the piezoelectric motor element, The bending hinge is such that it allows the piezoelectric motor element to move in the normal direction, and the bending hinge is rigid in the tangential direction, thereby the bending arm comprises a connecting element and is fixed to the piezoelectric motor element by a fixing means.

[0020] In some embodiments, the connecting element may comprise two foil elements: one top connecting foil element positioned on the top side of the piezoelectric motor element and one bottom connecting foil element positioned on the bottom side of the piezoelectric motor element. In some embodiments, both the top connecting foil element and the bottom connecting foil element may have arms with bending hinges.

[0021] The bending hinge for contacting the piezoelectric motor element may be configured to contact the piezoelectric motor element at the top surface and the bottom surface, respectively.

[0022] Alternatively, a single connecting element can be provided, having an arm equipped with a bendable hinge that contacts the piezoelectric motor element on its circumferential surface.

[0023] In embodiments of the present invention, when referring to foil, this may refer to a film-like structure or a thin layer, but may also include thicker layers, such as a thin plate. In some embodiments, such a plate can be bent, for example.

[0024] In an embodiment of the present invention, when it is mentioned that the piezoelectric motor element can move in the normal direction and the flexure hinge is rigid in the tangential direction, the fact that the flexure hinge is perpendicular to the movement in the expansion mode at the position of the fixed point is mentioned. The normal direction may also be defined as the radial direction with respect to the central position.

[0025] The flexure arm may be fixed to the piezoelectric motor element using an adhesive. The adhesive may be an epoxy adhesive or an acrylate or polyurethane.

[0026] The piezoelectric motor element can have a hole extending from the top surface to the bottom surface through the piezoelectric motor element, and the connecting element can further include a connection portion disposed through the hole of the piezoelectric motor element. The connection portion mechanically connects the top connection foil element and the bottom connection foil element, whereby different fixed positions are arranged away from the hole, and at the position of the hole, the connecting element and the piezoelectric motor element do not contact each other.

[0027] The connection portion may include a spacer ring for separating the top connection foil element and the bottom connection foil element.

[0028] The outer diameter of the spacer ring may be substantially smaller than the inner diameter of the hole of the piezoelectric motor element. In some embodiments, the outer diameter of the spacer ring may be 50 μm smaller than the inner diameter of the hole. In some embodiments, being substantially smaller than the inner diameter may mean less than 90%, for example less than 80%, for example less than 70% of the inner diameter of the hole.

[0029] The connection portion can include two shim elements, such as shim rings, that provide a mechanical connection between the top connection foil element and the bottom connection foil element and help to separate the foil elements from the piezoelectric motor element.

[0030] The dimensions of the connection portion may be such that there is a clearance in the range of 2 μm to 50 μm, for example 2 μm to 20 μm, for example about 10 μm, between the shim element and the top and bottom surfaces of the piezoelectric motor element.

[0031] In embodiments of the present invention, no force is generated in the vertical axis direction during operation, and therefore, play in this direction does not cause undesirable play or backlash in the driving direction.

[0032] A flexible circuit may be provided between the piezoelectric motor element and the connecting foil for electrically connecting to the electrodes of the piezoelectric motor element.

[0033] Flexible circuits for connecting piezoelectric motor elements provide a quick and precise method for electrically connecting electrodes within the piezoelectric motor elements, although such electrodes within the piezoelectric motor elements can also be connected by electrical wiring.

[0034] The piezoelectric actuator may further include a suspension element for suspending the piezoelectric motor element so that the piezoelectric motor element can move freely in a direction perpendicular to the driving direction while preventing undesirable movement in the driving direction.

[0035] The suspension element may comprise two suspension foils, one of which is positioned on the top side of the piezoelectric motor element and the other on the bottom side of the piezoelectric motor element.

[0036] The suspension foil may be positioned on the side of the connecting foil facing outward from the piezoelectric motor element, and the suspension foil and connecting foil may be positioned so as to be separated from each other by a shim element.

[0037] The suspension foil, shim elements, and connecting foils may be mechanically connected to one another. The suspension foil, shim element, and connecting foil may be mechanically connected to each other using a connector that extends through the central hole of the piezoelectric motor element.

[0038] The piezoelectric motor element may be in the shape of a plate. The electrodes may be electrically connected and configured so that driving the electrodes induces in-plane modes.

[0039] Taking into account the polarity of the piezoelectric motor elements, the electrodes can be electrically connected and configured such that the driving of the electrodes induces an in-plane bending mode and / or an in-plane expansion mode.

[0040] Taking into account the polarity of the piezoelectric material, the electrodes can be electrically connected and configured such that the driving of the electrodes alternately induces in-plane bending mode and in-plane expansion mode.

[0041] In some embodiments, electrodes can be configured to use in-plane modes.

[0042] An in-plane bending mode may be a vibration mode in which adjacent angles move in opposite directions, and an in-plane expansion mode may be a vibration mode in which different angles of the apex move synchronously in the same direction outward or inward.

[0043] In another embodiment, the present invention relates to a piezoelectric actuator, wherein the piezoelectric actuator is A piezoelectric motor element having a top surface and a bottom surface, A connecting element comprising two foil elements, wherein one top connecting foil element is positioned on the top side of the piezoelectric motor element, and one bottom connecting foil element is positioned on the bottom side of the piezoelectric motor element, and the top connecting foil element and the bottom connecting foil element contact the piezoelectric motor element at different fixed positions, and therefore the connecting element holds the piezoelectric motor element in a fixed position without interfering with the intrinsic modes of the piezoelectric motor element during resonance, The piezoelectric motor element has a hole that penetrates the piezoelectric motor element and extends from the top surface to the bottom surface. The connecting element further comprises a connecting portion positioned through a hole in the piezoelectric motor element, the connecting portion mechanically connecting the top connecting foil element and the bottom connecting foil element, thereby positioning different fixing positions away from the hole, and thereby preventing the connecting element and the piezoelectric motor element from contacting each other at the location of the hole.

[0044] The fixing position may be on the top and / or bottom surface of the piezoelectric element. Alternatively, the fixing position may be on the side surface of the piezoelectric motor element.

[0045] An advantage of the embodiments of the present invention is that a compact piezoelectric motor can be obtained. The connecting portion may include a spacer ring to separate the top connecting foil element and the bottom connecting foil element.

[0046] The outer diameter of the spacer ring may be substantially smaller than the inner diameter of the hole in the piezoelectric motor element. In some embodiments, the outer diameter of the spacer ring may be 50 μm smaller than the inner diameter of the hole. In some embodiments, substantially smaller than the inner diameter may mean less than 90% of the inner diameter of the hole, for example less than 80%, for example less than 70%.

[0047] The connection section may include two shim elements, such as shim rings, which provide a mechanical connection between the top connecting foil element and the bottom connecting foil element and help separate the foil elements from the piezoelectric motor element.

[0048] The dimensions of the connection part may be such that there is a clearance of 2 μm to 50 μm, for example, 2 μm to 20 μm, or for example, about 10 μm, between the top and bottom surfaces of the shim element and the piezoelectric motor element.

[0049] An advantage of the embodiments of the present invention is that no force is generated in the vertical axis direction during operation, and therefore play in this direction does not cause undesirable play or backlash in the drive direction.

[0050] A flexible circuit may be provided between the piezoelectric motor element and the connecting foil for electrically connecting to the electrodes of the piezoelectric motor element.

[0051] Flexible circuits for connecting piezoelectric motor elements provide a quick and precise method for electrically connecting electrodes within the piezoelectric motor elements, although such electrodes within the piezoelectric motor elements can also be connected by electrical wiring.

[0052] The piezoelectric actuator may further include a suspension element for suspending the piezoelectric motor element so that the piezoelectric motor element can move freely in a direction perpendicular to the driving direction while preventing undesirable movement in the driving direction.

[0053] The suspension element may comprise two suspension foils, one of which is positioned on the top side of the piezoelectric motor element and the other on the bottom side of the piezoelectric motor element.

[0054] The suspension foil may be positioned on the side of the connecting foil facing outward from the piezoelectric motor element, and the suspension foil and connecting foil may be positioned so as to be separated from each other by a shim element.

[0055] The suspension foil, shim elements, and connecting foils may be mechanically connected to one another. The suspension foil, shim element, and connecting foil may be mechanically connected to each other using a connector that extends through the central hole of the piezoelectric motor element.

[0056] The piezoelectric motor element may be in the shape of a plate. Taking into account the polarity of the piezoelectric motor elements, the electrodes can be electrically connected and configured such that the driving of the electrodes induces an in-plane bending mode and / or an in-plane expansion mode.

[0057] Taking into account the polarity of the piezoelectric material, the electrodes can be electrically connected and configured such that the driving of the electrodes alternately induces in-plane bending mode and in-plane expansion mode.

[0058] An in-plane bending mode may be a vibration mode in which adjacent angles move in opposite directions, and an in-plane expansion mode may be a vibration mode in which different angles of the apex move synchronously in the same direction outward or inward.

[0059] Specific preferred embodiments of the present invention are described in the appended independent and dependent claims. Features from the dependent claims may be combined as appropriate with features of the independent claims and other dependent claims, and may not be as explicitly described in the claims.

[0060] These and other aspects of the present invention will become apparent and clarified by reference to the embodiments described below. Further features of the present invention will become apparent from the examples and drawings.

[0061] Brief explanation of the drawing [Brief explanation of the drawing]

[0062] [Figure 1] A schematic diagram shows the motor elements of an ultrasonic piezoelectric motor having a mounting mechanism according to an embodiment of the present invention. [Figure 2] Figure 1 shows a cross-sectional view of the motor element along line AA. [Figure 3] This shows an overview of the motor elements of an ultrasonic piezoelectric motor with mounting functionality according to an embodiment of the present invention. [Figure 4] This shows a cross-sectional view of the motor element of an ultrasonic piezoelectric motor having a mounting function according to an embodiment of the present invention. [Figure 5] This shows a detailed view of a part of the cross-section of a motor element of an ultrasonic piezoelectric motor having a mounting function according to an embodiment of the present invention. [Figure 6] The diagram shows different components (layers) of an ultrasonic piezoelectric motor having a mounting mechanism according to an embodiment of the present invention, and also shows the piezoelectric motor. [Figure 7] The flexprint shows different components (layers) of an ultrasonic piezoelectric motor having a mounting mechanism according to an embodiment of the present invention. [Figure 8] The diagram shows different components (layers) of an ultrasonic piezoelectric motor having a mounting mechanism according to an embodiment of the present invention, and also shows the connecting foil. [Figure 9]The diagram shows different components (layers) of an ultrasonic piezoelectric motor having a mounting mechanism according to an embodiment of the present invention, and also shows a suspension foil that can be used in an embodiment of the present invention. [Figure 10] An example of a piezoelectric motor according to one embodiment of the present invention is shown. [Modes for carrying out the invention]

[0063] The drawings are illustrative and non-limiting. The sizes of some elements in the drawings may be exaggerated, and they may not be drawn to scale for illustrative purposes only. No reference numeral in the claims should be construed as limiting. In different drawings, the same reference numeral refers to the same or similar element.

[0064] Detailed description of preferred embodiments The present invention is described with respect to specific embodiments and with reference to specific drawings, but is not limited thereto and is limited only by the claims. The drawings described are schematic and non-limiting. In the drawings, the sizes of some elements are exaggerated and may not be drawn to scale for illustrative purposes only. When the term “comprising” is used herein and in the claims, it is not intended to exclude other elements or processes. When an indefinite or definite article, e.g., “a” or “an” or “the,” is used with a singular noun, this includes the plural of that noun unless otherwise specified. The term “comprising” as used in the claims should not be construed as being limited to the means enumerated thereafter, and this is not intended to exclude other elements or processes. Accordingly, the expression “apparatus comprising means A and B” should not be limited to an apparatus consisting only of components A and B. This means that, with respect to the present invention, the relevant components of the apparatus are only A and B. Furthermore, terms such as first, second, third, etc., in the specification and claims are used to distinguish similar elements and are not necessarily intended to describe a sequential or chronological order. It should be understood that such terms are interchangeable under appropriate circumstances, and that embodiments of the invention described herein may operate in an order other than those described or illustrated herein. Furthermore, terms such as top, bottom, above, below, etc., in the specification and claims are used for descriptive purposes and are not necessarily intended to describe relative positions. Such terms are interchangeable under appropriate circumstances, and it should be understood that embodiments of the invention described herein may operate in an orientation other than those described or illustrated herein.

[0065] In the drawings, similar reference numerals indicate similar features, and reference numerals appearing in two or more drawings refer to the same element. The drawings and the following detailed description illustrate specific embodiments of actuators, more specifically piezoelectric actuators.

[0066] In embodiments of the present invention, when referring to a piezoelectric material, it refers to a material that exhibits the effect of accumulating electric charge in response to applied mechanical stress. Conversely, by applying an electric field to a piezoelectric material, the material undergoes deformation and undergoes displacement.

[0067] When referring to an actuator in embodiments of the present invention, the term refers to an active element, preferably in the form of a piezoelectric ceramic block or a stack of different piezoelectric ceramic layers, which includes, for example, a piezoelectric material and electrodes. The actuator used in embodiments of the present invention may be of any type: a piezoelectric actuator, a magnetostrictive actuator, or an electrostrictive actuator.

[0068] In embodiments of the present invention, when referring to a motor, for example a piezoelectric motor, the term refers to a motor equipped with an actuator, for example a piezoelectric ceramic actuator.

[0069] In embodiments of the present invention, when referring to a suspension or suspension foil, it refers to a component or mechanism that supports a motor and presses it against a load with a force that provides preload.

[0070] In embodiments of the present invention, when referring to contact, for example, it refers to the position where the tip of the motor according to an embodiment of the present invention contacts the surface of the driven object.

[0071] In embodiments of the present invention, when referring to a fixed position, it refers to the position / location where the flexible hinge is fixed to the piezoelectric motor.

[0072] In embodiments of the present invention, when referring to preload, it refers to a static force acting on an actuator or motor according to an embodiment of the present invention that acts substantially perpendicular to the direction of movement of the load.

[0073] In embodiments of the present invention, when referring to a load or stage, it refers to a component or structure that is (should be) driven by a motor according to an embodiment of the present invention.

[0074] It should be noted that the external form of the piezoelectric motor element does not limit the embodiments of the present invention. For illustrative purposes, embodiments of the present invention are not limited thereto, and specific embodiments are described with reference to piezoelectric motor elements having the same external form as described in European Patent Application Publication No. 3535842 in the name of the present applicant, and such piezoelectric motor elements may be driven in the same manner as described in European Patent Application Publication No. 3535842, for example, using the same modes. European Patent Application Publication No. 3535842 discloses that electrodes can be electrically connected and configured such that, taking into account the polarity of the piezoelectric material, the driving of the electrodes induces in-plane bending modes and / or in-plane expansion modes. In a preferred embodiment of European Patent Application Publication No. 3535842, the resonant mode is achieved by exciting or energizing two electrode pairs with two AC voltages while varying the phase difference and / or voltage amplitude between the two AC voltages. These voltages excite the horizontal eigenmode of the actuator, e.g., the in-plane bending mode, and the vertical eigenmode, e.g., the in-plane expansion mode, resulting in elliptical motion of the contact region. When the contact area (tip) is pressed against the surface, this surface is driven relative to the actuator at a speed and direction corresponding to the selected trajectory.

[0075] Nevertheless, embodiments of the present invention are not limited by the external shape of the piezoelectric motor element or the mode used to drive the piezoelectric motor element, but are limited by the features defined in the independent claims.

[0076] While specific excitation modes may be mentioned in the examples of embodiments of the present invention, the embodiments are not limited thereto and also encompass piezoelectric motors driven using different excitation modes.

[0077] In a first embodiment, the present invention relates to a piezoelectric actuator comprising a piezoelectric motor element made of a piezoelectric material. The piezoelectric material may be a piezoelectric plate, but embodiments are not limited thereto. The piezoelectric motor element has a top surface and a bottom surface. The piezoelectric actuator also comprises at least one contact point for contacting a load to be actuated. The at least one contact point is located on a third circumferential surface of the ceramic piezoelectric material. In embodiments of the present invention, mounting and contact are performed at two separate locations on the piezoelectric material.

[0078] The piezoelectric actuator also comprises a connecting element. In some embodiments, the connecting element comprises two foil elements, namely, one top connecting foil element positioned on the top side of the piezoelectric motor element and one bottom connecting foil element positioned on the bottom side of the piezoelectric motor element. In some embodiments, a single connecting foil or plate is provided. According to embodiments of the present invention, the connecting element has an arm with a bending hinge for securing the piezoelectric motor element to different fixed positions located at the node positions of one or more bending modes of the piezoelectric motor element.

[0079] Alternatively, a single connecting element can be provided, having an arm equipped with a bendable hinge that contacts the piezoelectric motor element on its circumferential surface.

[0080] The bending hinge allows the piezoelectric motor element to move in the normal direction, and the bending hinge is rigid in the tangential direction, thereby the bending arm is fixed to the piezoelectric motor element by a fixing means.

[0081] Embodiments of the present invention may further typically comprise at least one pair of electrodes positioned on the top surface of a piezoelectric material and at least one electrode positioned on the bottom surface of a ceramic piezoelectric material. Taking into account the polarity of the ceramic piezoelectric material, the electrodes can be electrically connected and configured such that the driving of the electrodes induces in-plane bending and / or in-plane expansion modes. This can be provided using a flexible circuit, as illustrated, but embodiments are not limited thereto. Further standard and optional features are described below with reference to exemplary embodiments.

[0082] In a second aspect, the present invention relates to a motor comprising a piezoelectric actuator as described in the first aspect. When referring to a motor in embodiments of the present invention, it refers to at least the combination of the actuators described above, in combination with suspension and applied preload.

[0083] For illustrative purposes, the present invention will be further described with reference to drawings showing typical and optional components of exemplary embodiments of the present invention. Note that while motors are mentioned, where elements of a piezoelectric actuator are described, the actuator itself is also mentioned.

[0084] In embodiments of the present invention, the connection comprises two foil elements positioned on the top and bottom sides of the motor element. In certain embodiments, each foil contacts the motor at four points, but embodiments are not limited to this. At the locations of these fixing points, the motor moves / vibrates only in the normal direction (nodes of the bending mode). The foil element has four arms with bending hinges that enable this normal vibration. However, in the tangential direction, the hinges are completely rigid. Some examples of materials that can be used are ferrous materials, non-ferrous materials, engineering plastics, etc. In preferred embodiments, contact between the motor element and the bending arms is achieved by epoxy adhesive. Alternatively, other types of adhesives, such as acrylate or polyurethane, can also be used. Nevertheless, alternatively, other types of adhesives or even other types of fastening, such as soldering or brazing, can also be used. In some embodiments, the shape of the arm ends is designed such that capillary forces acting on the uncured adhesive form a meniscus shape that holds the adhesive in place during curing.

[0085] The combination of the top and bottom connecting foils holds the motor element in place by eliminating two lateral degrees of freedom and all rotational degrees of freedom. This is achieved through a highly rigid and backlash-free connection in the drive direction without interfering with the motor's intended natural modes.

[0086] In some specific embodiments, the connecting foil is separated by a spacer ring and a shim ring. This stacked layer of elements is pressed against each other by a bolt connection through a central hole. There is no mechanical contact between the motor and the connecting elements around the motor's central mounting hole. The outer diameter of the spacer ring is significantly smaller than the inner diameter of the piezoelectric motor's central hole. In some embodiments, the outer diameter of the spacer ring may be 50 μm smaller than the inner diameter of the hole. In some embodiments, substantially smaller than the inner diameter may be less than 90% of the inner diameter of the hole, e.g., less than 80%, e.g., less than 70%. There is a minimum amount of play between the shim ring and the top / bottom surface of the motor in the vertical / axial direction. The amount of such play may be in the range of 2 to 20 micrometers, e.g., about 10 micrometers. No force is generated in the vertical / axial direction during operation. Any play in this direction does not cause undesirable play or backlash in the driving direction.

[0087] Instead of a central or off-center mounting hole, the connecting foil may be held together by a connector located on the outside of the piezoelectric motor element.

[0088] As described above, in some embodiments, a flexprint circuit is provided between the motor and the connecting foil to make electrical connections to different electrodes of the motor element. Another solution for this may be a simple wire.

[0089] Figures 1 and 2 show the first diagram and cross-sectional view of the piezoelectric motor element and connecting foil, as well as, in this example, the mechanical connection between the connecting foils through a hole passing through the piezoelectric motor element.

[0090] In embodiments of the present invention, the piezoelectric actuator may also include a suspension element. In some embodiments, the suspension element may consist of two suspension layers. In one embodiment, the suspension element adds another foil to both the top and bottom sides of the motor. In some embodiments, a piezoelectric is provided having a suspension structure, e.g., two connecting foils attached to a thick suspension element. The system can provide sufficient tilt stiffness. The function of these foils is to allow the motor element to move freely in a direction perpendicular to the drive direction while preventing undesirable movement in the drive direction. These suspension foils are also provided with a bending hinge that allows them to move freely over a predetermined distance. Such a distance may be 0.1 mm to 1 mm, for example, about 0.5 mm. The hinge is rigid in the drive direction and the torsional direction. In this example, the suspension foils are attached to both sides of the motor element along with their connecting foils. A shim ring is installed between the two layers. Some flexibility exists in the vertical / axial and two tilt directions. However, this flexibility is not a problem as no force is generated in these directions. Figures 3 to 5 show the suspension layers and how they are configured in relation to the connecting layers and piezoelectric motor elements.

[0091] Figure 6 shows a piezoelectric motor that can be used in an embodiment of the present invention, Figure 7 shows a flexible print that can be used in an embodiment of the present invention, Figure 8 shows a connecting foil that can be used in an embodiment of the present invention, and Figure 9 shows a suspension foil that can be used in an embodiment of the present invention.

[0092] Other methods could be used for this suspension function, such as small guideways. However, these other methods are not as compact and introduce mechanical play in the drive direction.

[0093] In this embodiment, the stack of suspension foil, shim ring, and connecting foil is held together by bolts and threaded pins passing through the motor's central hole. The tightening torque must be sufficient to withstand the motor's driving force and torque. The central pin is also responsible for aligning all the components.

[0094] The combination of the motor element, connecting layer, and suspension layer forms a motor unit that is easily mounted on the stator of the positioning device. The last element is a spring that presses the motor's drive contacts against the traction surface of the device. The spring may be a simple U-shaped spring that provides equal preload at the top and on both sides of the motor unit. Again, other solutions are possible, but this U-shaped spring results in a very compact implementation.

[0095] In one particular embodiment, the connecting layer and the suspension layer can be combined into a single layer. In another particular embodiment, for example, electrical connections via a flexible circuit and mechanical connections can be combined into a single layer.

[0096] In the exemplary embodiment described above, the connecting element or the different parts of the connecting element and the suspension element are held together using bolt and screw connections, but alternative means for holding these parts together, such as press-fit connections, shrink-fit connections, adhesives, etc., can be used.

[0097] In one particular embodiment, a square piezoelectric element is used, wherein a connecting foil is connected to the piezoelectric element via fixed points, one on each side of the piezoelectric element, and the connecting foil is fixed to the piezoelectric element via a bendable arm and hinge. An example of such an embodiment is shown in Figure 10.

[0098] As a further example, Figure 10 shows a piezoelectric motor according to an embodiment of the present invention. Different orientations applicable to the system are shown in the figure. It can be seen that the fixing point for fixing the hinge to the piezoelectric element is located at the node of the bending mode. The fixing point is positioned on the node of the bending mode. The longitudinal direction of the arm is perpendicular to the local direction of movement of the other mode. Such a mode may be a bending mode or an expansion mode. The longitudinal direction is defined by a line connecting the hinge and the fixing point.

[0099] In the embodiments of the present invention described above, bending and expansion modes are used, but it should be noted that embodiments of the present invention can also use other bending modes, thereby positioning the fixed points at the nodes of the bending modes. The flexible hinge is positioned perpendicular to the local movement of the other modes.

[0100] In another embodiment, the present invention relates to a piezoelectric actuator comprising a piezoelectric motor element having a top surface and a bottom surface, and a connecting element comprising two foil elements, the two foil elements being one top connecting foil element positioned on the top side of the piezoelectric motor element and one bottom connecting foil element positioned on the bottom side of the piezoelectric motor element, wherein the top connecting foil element and the bottom connecting foil element contact the piezoelectric motor element at different fixed positions on the top surface of the piezoelectric element and the bottom surface of the piezoelectric motor element, respectively, and therefore the connecting element holds the piezoelectric motor element in a fixed position without interfering with the intrinsic modes of the piezoelectric motor element during resonance.

[0101] According to embodiments of the present invention, the piezoelectric motor element has a hole that penetrates the piezoelectric motor element and extends from the top surface to the bottom surface. This hole may be located in the center or at any other suitable location. According to embodiments of the present invention, the connecting element further comprises a connecting portion disposed through the hole in the piezoelectric motor element, the connecting portion mechanically connecting the top connecting foil element and the bottom connecting foil element, thereby arranging different fixed positions away from the hole, and the connecting element and the piezoelectric motor element not in contact with each other at the location of the hole. The piezoelectric motor element may be as described in the first embodiment. The connecting element may be as described in the first embodiment. The piezoelectric actuator may also comprise a suspension element, which may, in one example, be as described in the first embodiment.

[0102] According to embodiments of the present invention, the connection may include, for example, bolts and screws that hold the elements together. Nevertheless, alternatives such as press-fit connections, shrink-fit connections, and adhesives may also be used.

[0103] Further features may be as described in the first embodiment. The elements of the piezoelectric actuator or motor may further be as described in European Patent Application Publication No. 3535842, but the embodiments are not limited thereto.

[0104] Clause Specific embodiments of the present invention are described by the following numbered clauses.

[0105] 1. A piezoelectric actuator, A piezoelectric motor element having a top surface and a bottom surface, A connecting element having an arm with a bending hinge for contacting the piezoelectric motor element at different fixed positions located at the node positions of one or more bending modes of the piezoelectric motor element, A bending hinge that allows the piezoelectric motor element to move in the normal direction and is rigid in the tangential direction, thereby fixing the bending arm to the piezoelectric motor element by a fixing means, A piezoelectric actuator equipped with the following features.

[0106] 2. The piezoelectric actuator as described in Clause 1, wherein the bendable arm is fixed to the piezoelectric motor element using adhesive.

[0107] 3. A piezoelectric actuator according to any of the preceding clauses, wherein the connecting element comprises two foil elements, one top connecting foil element positioned on the top side of the piezoelectric motor element, and one bottom connecting foil element positioned on the bottom side of the piezoelectric motor element, and the top connecting foil element and the bottom connecting foil element have arms having a bending hinge for contacting the piezoelectric motor element, and are configured to contact the piezoelectric motor element at the top surface and bottom surface of the piezoelectric motor element, respectively.

[0108] 4. The piezoelectric motor element has a hole that penetrates the piezoelectric motor element and extends from the top surface to the bottom surface, and the connecting element further comprises a connecting portion disposed through the hole in the piezoelectric motor element, the connecting portion mechanically connecting the top connecting foil element and the bottom connecting foil element, thereby arranging different fixed positions away from the hole, and the connecting element and the piezoelectric motor element do not come into contact with each other at the location of the hole, the piezoelectric actuator according to Clause 3.

[0109] 5. The piezoelectric actuator according to Clause 4, wherein the connecting portion includes a spacer ring for separating the top connecting foil element and the bottom connecting foil element.

[0110] 6. The piezoelectric actuator described in Clause 5, wherein the outer diameter of the spacer ring is substantially smaller than the inner diameter of the hole in the piezoelectric motor element.

[0111] 7. The piezoelectric actuator according to any of the preceding clauses, wherein the connecting portion comprises two shim elements, such as shim rings, which provide a mechanical connection between the top connecting foil element and the bottom connecting foil element and help to separate the foil elements from the piezoelectric motor element.

[0112] 8. The dimensions of the connection part are such that there is a clearance of approximately 2 μm to 20 μm between the shim element and the top and bottom surfaces of the piezoelectric motor element, as described in Clause 7.

[0113] 9. A piezoelectric actuator according to any of the preceding clauses, insofar as it is subject to clause 3, wherein a flexible circuit for electrical connection to electrodes within the piezoelectric motor element is provided between the piezoelectric motor element and the connecting foil.

[0114] 10. A piezoelectric actuator according to any of the preceding clauses, further comprising a suspension element for suspending a piezoelectric motor element so that the piezoelectric motor element can move freely in a direction perpendicular to the driving direction while preventing undesirable movement in the driving direction.

[0115] 11. The piezoelectric actuator according to Clause 10, wherein the suspension element comprises two suspension foils, one of which is positioned on the top side of the piezoelectric motor element and the other suspension foil is positioned on the bottom side of the piezoelectric motor element.

[0116] 12. The piezoelectric actuator according to Clause 11, to the extent that it is subject to Clause 3, wherein the suspension foil is positioned on the side of the connecting foil facing outward from the piezoelectric motor element, and the suspension foil and the connecting foil are positioned so as to be separated from each other by a shim element.

[0117] 13. The piezoelectric actuator described in Clause 12, wherein the suspension foil, shim element, and connecting foil are mechanically connected to one another.

[0118] 14. The piezoelectric actuator according to Clause 13, wherein the suspension foil, shim element, and connecting foil are mechanically connected to one another using a connecting portion extending through the central hole of the piezoelectric motor element.

[0119] 15. A piezoelectric actuator as described in any of the preceding clauses, wherein the piezoelectric motor element is plate-shaped.

Claims

1. A piezoelectric actuator, A piezoelectric motor element having a top surface and a bottom surface, A connecting element comprising an arm having a bending hinge for contacting the piezoelectric motor element at different fixed positions located at the node positions of one or more bending modes of the piezoelectric motor element, The longitudinal direction of the arm having a bending hinge is such that, at each fixed point, the piezoelectric motor element is positioned perpendicular to the movement of the expansion mode, so that at each fixed point, the piezoelectric motor element can move only radially with respect to the central position. As a result, the bending arm is fixed to the piezoelectric motor element by a fixing means, and the connecting element is A piezoelectric actuator equipped with the following features.

2. The piezoelectric actuator according to claim 1, wherein the bending hinge is rigid in the tangential direction.

3. The piezoelectric actuator according to claim 1 or 2, wherein the connecting element comprises four arms having a bending hinge.

4. The piezoelectric actuator according to claim 1 or 2, wherein the bendable arm is fixed to the piezoelectric motor element using an adhesive.

5. The piezoelectric actuator according to claim 1 or 2, wherein the connecting element comprises two foil elements, one top connecting foil element positioned on the top side of the piezoelectric motor element, and one bottom connecting foil element positioned on the bottom side of the piezoelectric motor element, and the top connecting foil element and the bottom connecting foil element have arms having a bending hinge for contacting the piezoelectric motor element, and are configured to contact the piezoelectric motor element at the top surface and the bottom surface of the piezoelectric motor element, respectively.

6. The piezoelectric motor element has a hole that penetrates the piezoelectric motor element and extends from the top surface to the bottom surface, and the connecting element further comprises a connecting portion disposed through the hole of the piezoelectric motor element, the connecting portion mechanically connects the top connecting foil element and the bottom connecting foil element, as described in claim 5.

7. The piezoelectric actuator according to claim 6, wherein the different fixing positions are arranged away from the hole such that the connecting element and the piezoelectric motor element do not come into contact with each other at the location of the hole.

8. The piezoelectric actuator according to claim 7, wherein the connecting portion includes a spacer ring for separating the top connecting foil element and the bottom connecting foil element.

9. The piezoelectric actuator according to claim 8, wherein the outer diameter of the spacer ring is substantially smaller than the inner diameter of the hole in the piezoelectric motor element.

10. The piezoelectric actuator according to claim 1 or 2, wherein the connecting portion comprises two shim elements, such as shim rings, which provide a mechanical connection between the top connecting foil element and the bottom connecting foil element and help separate the foil element from the piezoelectric motor element.

11. The piezoelectric actuator according to claim 10, wherein the dimensions of the connection portion are such that there is a clearance of about 2 μm to 20 μm between the shim element and the top and bottom surfaces of the piezoelectric motor element.

12. The connecting element comprises two foil elements, one top connecting foil element positioned on the top side of the piezoelectric motor element, and one bottom connecting foil element positioned on the bottom side of the piezoelectric motor element, and the top connecting foil element and the bottom connecting foil element each have an arm having a bending hinge for contacting the piezoelectric motor element, and are configured to contact the piezoelectric motor element at the top surface and the bottom surface of the piezoelectric motor element, respectively. The piezoelectric actuator according to claim 1 or 2, wherein a flexible circuit for electrical connection to an electrode in the piezoelectric motor element is provided between the piezoelectric motor element and the connecting foil.

13. The piezoelectric actuator according to claim 1 or 2, further comprising a suspension element for suspending the piezoelectric motor element so that the piezoelectric motor element can move freely in a direction perpendicular to the driving direction while preventing undesirable movement in the driving direction.

14. The piezoelectric actuator according to claim 13, wherein the suspension element comprises two suspension foils, one of which is positioned on the top side of the piezoelectric motor element and the other suspension foil is positioned on the bottom side of the piezoelectric motor element.

15. The connecting element comprises two foil elements, one top connecting foil element positioned on the top side of the piezoelectric motor element, and one bottom connecting foil element positioned on the bottom side of the piezoelectric motor element, and the top connecting foil element and the bottom connecting foil element each have an arm having a bending hinge for contacting the piezoelectric motor element, and are configured to contact the piezoelectric motor element at the top surface and the bottom surface of the piezoelectric motor element, respectively. The piezoelectric actuator according to claim 14, wherein the suspension foil is positioned on the side of the connecting foil facing outward from the piezoelectric motor element, and the suspension foil and the connecting foil are positioned so as to be separated from each other by a shim element.

16. The piezoelectric actuator according to claim 15, wherein the suspension foil, the shim element, and the connecting foil are mechanically connected to one another.

17. The piezoelectric actuator according to claim 16, wherein the suspension foil, the shim element, and the connecting foil are mechanically connected to each other using a connecting portion extending through the central hole of the piezoelectric motor element.

18. The piezoelectric actuator according to claim 1 or 2, wherein the piezoelectric motor element is plate-shaped.

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