DE102020002199B4 - Piezoelectric inchworm linear motor - Google Patents

Abstract

Piezoelectric inchworm linear motor (1, 1', 1") comprising: a first clamp cell (2) having a first clamp frame (7) and a first piezoelectric clamp stack (27), the first piezoelectric clamp stack (27) being located within the first clamp frame (7 ) is arranged such that the first piezoelectric clamp stack (27) is at least partially in contact with the first clamp frame (7),a second clamp cell (3) having a second clamp frame (11) and a second piezoelectric clamp stack (31), wherein the second piezoelectric clamp stack (31) is arranged within the second clamp frame (11) such that the second piezoelectric clamp stack (31) is at least partially in contact with the second clamp frame (11), anda feed cell (5, 5', 5" ) with a piezoelectric feed stack (35, 35', 35"), wherein the piezoelectric feed stack (35, 35', 35") is at least indirectly in contact with the two clamping cells (2, 3) and the two clamping cells ( 2, 3) to one another or coupled to one another, the two clamping cells (2, 3) and the feed cell (5, 5', 5") being connected in series and along a movement axis (19) of the piezoelectric inchworm linear motor (1, 1' , 1"), each piezoelectric clamp stack (27, 31) being arranged in the clamp cell (2, 3) such that a change in an electrical voltage across the piezoelectric clamp stack (2, 3) causes a change in expansion of the piezoelectric clamp stack ( 2, 3) parallel to the movement axis (19), so that the clamping frame (7, 11) undergoes a change in size essentially perpendicular to the movement axis (19), and so that the clamping frame (7, 11) is connected to a guide unit (47) in Engaging occurs or the engagement is released, and wherein the feed stack (35, 35', 35") is arranged transversely to the movement axis (19), so that by applying an electrical voltage to the feed stack (35, 35', 35"), the feed stack (35, 35', 35") a change in length q learns about the movement axis (19).

Description

The present application relates to a piezoelectric inchworm linear motor (PIL).

An inchworm linear motor uses piezoelectric actuators or stacks to move or move along a guide, such as a shaft, with nanometer-level precision. Due to its low mass and small volume, the inchworm linear motor is used in particular in medical technology, for example in orthopedics and in jaw surgery, e.g. for the realization of callus distractor implants. In addition, the inchworm linear motor is widely used in scanning tunneling microscopes. A scanning tunneling microscope requires nanometer-scale control of a scanning tip in close proximity to the material to be observed.

Inchworm linear motors are available on the market in different designs and with different operating concepts. In its simplest form, the inchworm linear motor uses three piezoelectric stacks to which an electrical voltage is applied sequentially so that a guide unit can be gripped by one of the piezoelectric stacks, with the guide unit being moved in a linear direction or the inchworm linear motor linearly moving along the guide unit moves. The movement is due to the expansion of a piezoelectric feed stack, which translates a piezoelectric clamp stack in a linear direction relative to the guide unit.

The greatest challenge in the realization of a piezoelectric inchworm linear motor is the miniaturization and compact design while at the same time achieving a high actuating or driving force.

In "Kim J., Lee, J.; Self-moving cell linear motor using piezoelectric stack actuators. In: Smart Mater. structure 14 (2005), pp. 934 - 940 describes a linear motor with a self-moving cell (SCLM) using a piezoelectric stack actuator. The self-moving cell consists of an oval-shaped shell structure and a piezoelectric stack actuator. The concept of the self-propelled cell differs from a conventional inchworm linear motor because the SCLM has a unified clamping and thrust mechanism. The clamping force of the SCLM is determined by the amount of interference and the friction between the shell structure and the guideway. Thus, this motor can generate a large clamping force and maintain a fail-safe lock.

the EP 0 836 266 A2 describes an actuator in which a piezoelectric element is placed in a posture perpendicular to a guide rail, while a piezoelectric element is placed in a posture parallel to the guide rail. Further, the actuator includes a movable body having a stepped notch portion, the notched portion substantially dividing the movable body into two portions. When the piezoelectric element slides, part of the split movable body is fixed between guide rails.

the EP 1 702 368 B1 describes a positioner with a fixed part that can be moved in a plane relative to a movable part. The moving part includes a piezoelectric device arranged to expand and contract within the plane. The movable member can be selectively clamped in position relative to the fixed member at the first, second, and third locations by respective first, second, and third releasable clamping mechanisms.

the DE 101 18 456 A1 describes a drive system that works according to the inchworm principle as a linear drive. In particular, it serves as an adjustment mechanism for optical elements in optical systems. It has sections that can be moved relative to a guide element and are connected to one another via an element that is linearly variable in length. Each of the sections has at least one clamping device. In the non-actuated state, the clamping devices clamp the sections in a fixed position relative to the guide element.

Various configurations of piezoelectric linear motors are known from the prior art. Many of the configurations allow for a compact size and a large lift capability, but the driving force response is rather small. Motors and actuators designed based on the force amplification mechanism exhibit better drive force response, which is essential for applications where large actuation force is the critical factor. However, these motors and actuators have less stroke response or lift capability. By stroke is meant the distance covered by the piezoelectric feed stack of the piezoelectric inchworm motor in a reciprocating motion along the guide unit.

The piezoelectric linear motors, developed based on a force amplification mechanism, exhibit better force response, which is crucial for applications where large actuation force is the critical factor. However, the stroke response becomes smaller and more control pulses need to be applied in order to achieve a large deflection or a large feed. The internal mechanical stress of the mechanism, either in the case of deflection or force amplification, affects the overall efficiency of the motor.

The actuation force applied to the load or guide assembly is the resultant force of the piezoelectric stack after subtracting the internal mechanical force of the mechanism. This means that the more internal tension there is, the less force is amplified and vice versa.

Approaches to force amplification are known from the prior art, which are based either on large carriers for piezoelectric stacks that are connected by tiny hinges ( U.S. 2014/0333180 A1 ), or on nested frames ( U.S. 2012/0119620 A1 ) are based. However, the reliability problems of the hinges, the mechanical losses due to internal stresses and the bulky sizes are the main disadvantages of such designs for realizing a piezoelectric inchworm linear motor, which is miniaturized and allows both a large stroke and a large force release.

Proceeding from the prior art, it is therefore the object of the present invention to provide an improved piezoelectric inchworm linear motor that enables a large stroke and a large amount of force to be released.

According to the invention, this object is achieved by the subject matter of the independent claim. Preferred embodiments emerge from the dependent claims.

According to one aspect of the invention, there is provided a piezoelectric linear inchworm motor, the piezoelectric linear inchworm motor comprising: a first clamp cell having a first clamp frame and a first piezoelectric clamp stack, the first piezoelectric clamp stack being disposed within the first clamp frame such that the first piezoelectric clamp stack is at least partially in contact with the first clamping frame, a second clamping cell having a second clamping frame and a second piezoelectric clamping stack, the second piezoelectric clamping stack being arranged within the second clamping frame such that the second piezoelectric clamping stack is at least partially in contact with the second clamping frame and a feed cell with a piezoelectric feed stack. The piezoelectric feed stack is at least indirectly in contact with the two clamp cells and connects or couples the two clamp cells to one another and the two clamp cells and the feed cell are arranged in series and along a movement axis of the piezoelectric inchworm linear motor. Each piezoelectric clamp stack is arranged in the clamp cell such that a change in an electrical voltage across the piezoelectric clamp stack causes a change in expansion of the piezoelectric clamp stack parallel to the axis of movement, so that the clamp frame undergoes a change in size substantially perpendicular to the direction of movement, and so that the clamp frame comes into engagement with a guide unit or the engagement is released.

According to the piezoelectric inchworm linear motor according to the invention, the two clamping cells and the feed cell, which is preferably arranged between the clamping cells, are arranged in series and along an axis of movement; the axis of movement preferably runs parallel to the guide unit, which is, for example, a drive shaft or a housing of a drive object or Target object can be. A change in the electrical voltage on one of the two piezoelectric clamping stacks or on the feed stack causes a change in expansion of the respective piezoelectric stack along or parallel or transverse or perpendicular to the movement axis. A change in expansion means that the respective stack is lengthened or shortened at least along a preferred direction as a result of the application or change in an electrical voltage. As a rule, a conventional piezo stack expands when an electrical voltage is applied, specifically in a preferred direction in particular. Depending on the arrangement of the piezo stack, the expansion can thus be parallel to the axis of movement or transverse to the axis of movement of the piezoelectric inchworm linear motor. In particular, depending on the arrangement of the piezo stack, the piezo stack can be lengthened or shortened, namely parallel to the axis of movement or transverse to the axis of movement. Thus, opposite side faces of the stack can have a changed distance from one another due to the change in expansion.

A piezo stack as is the subject of this application can comprise a plurality of stacked conventional piezo elements.

In the simplest case, a piezo element is a plate with electrodes on the end faces that expands in the thickness direction and contracts in the transverse direction when a voltage is applied. The deformation persists as long as the stress remains applied. If there are no changing external forces, no energy is required to maintain the deformation. If the polarity of the voltage is reversed, the direction of the deformation changes - in this case contraction in the thickness direction and expansion in the transverse direction.

In particular, a piezo stack can be manufactured by cascading a plurality of conventional piezo elements by joining together a number of thin piezo elements with electrodes in between. This results in a mechanical series arrangement controlled by an electrical parallel circuit. Piezo elements and electrodes can be stacked alternately. A piezo disc can be stacked on top of an electrode, for example the plus connection, an electrode (-) can be stacked on top of this piezo disc, and finally another piezo disc, but this time the polarization direction is changed. A variety of these assemblies can be stacked on top of each other. The plus and minus electrodes are each connected externally.

The voltage mentioned above is applied to the electrode, so that the distance between the two electrodes increases due to the linear expansion of the piezoelectric crystal. The maximum voltage to be applied depends on the thickness of the piezo discs, the material and the insulating properties between the electrodes.

The change in expansion of the piezoelectric clamping stack can occur in either direction along the axis of movement. The piezoelectric stacks arranged in the cells are arranged in series and in the direction of the movement axis. The two clamp stacks and the feed stack can be arranged in a row and in the direction of a longitudinal axis of the PIL or extend in the direction of the longitudinal axis of the PIL, so that by applying an electrical voltage to one or both clamp stacks and/or the feed stack, one or the two clamp stacks and/or the feed stack experience a change in length along the longitudinal axis of the PIL. The feed stack is arranged transversely to the longitudinal axis of the PIL or extends transversely to the longitudinal axis of the PIL, so that application of an electrical voltage to the feed stack causes the feed stack to change in length transversely to the longitudinal axis of the PIL. By applying a voltage to the individual piezoelectric stacks, the piezoelectric inchworm linear motor can be moved along the guide unit. Preferably, the linear inchworm piezoelectric motor moves parallel to the guide unit. Due to the expandability of the feed stack in the longitudinal direction or in the direction of the axis of movement, the piezoelectric force in the longitudinal direction (longitudinal piezoelectric force) can be used directly and miniaturization and thus a compact design of the piezoelectric inchworm linear motor is made possible.

The clamping cells of the piezoelectric inchworm linear motor according to the invention each comprise clamping frames, the clamping stacks arranged in the clamping frames preferably being in contact with opposite sides of the clamping frames in the direction of the longitudinal axis of the PIL. By applying or changing a voltage on the clamp stack, the clamp stack can experience a change in expansion. The clamping stack is lengthened in the direction of the longitudinal axis of the PIL or in the direction of the axis of movement and possibly shortened transversely to the longitudinal axis of the PIL or transversely to the axis of movement. In other words, the distance between opposite side faces of the clamp stack in the direction of the longitudinal axis of the PIL is increased. Due to mechanical properties of the clamping stack, the distance between opposite side surfaces of the PIL can be shortened transversely, in particular perpendicularly, to the longitudinal axis. As a result of this change in expansion of the clamping stack, the clamping frame in turn undergoes a deformation due to the contact with the clamping stack. Since the piezoelectric clamping stack is at least partially in contact with the clamping frame, the clamping frame is also deformed relative to the movement axis, i.e. viewed in the direction of the movement axis or parallel to the movement axis and perpendicular to the movement axis, due to the change in expansion of the piezoelectric clamping stack. The clamping frame is deformed by the change in length of the piezoelectric clamping stack, as a result of which a force is exerted on the clamping frame in the direction of the movement axis. This causes the size or the shape of the clamping frame to be changed. In other words, the extent of the clamping frame lengthens in the direction of the movement axis and shortens transversely or perpendicularly to the movement axis. The distance between opposite side surfaces of the clamping frame in the direction of the longitudinal axis of the PIL or in the direction of the movement axis is increased, and the distance between opposite side surfaces of the clamping frame transversely or perpendicularly to the longitudinal axis of the PIL is shortened.

Due to the deformation or resizing of the clamping frame, the clamping frame with the Guide unit engage or the engagement can be released from the guide unit. Due to the fact that the extent of the clamping frame shortens in the direction perpendicular to the axis of movement and lengthens in the direction of the axis of movement, a leverage effect is created. A first portion of the clamping frame has a long lever action, whereas a second portion of the clamping frame has a short lever action.

The first region at least partially comprises one of the two opposite side surfaces of the clamping frame in the direction of the longitudinal axis of the PIL, on which a force is exerted by the expansion of the clamping stack. Because the clamping stack expands or changes its length in the direction of the movement axis when an electrical voltage is applied, the clamping stack presses against the clamping frame, so that the clamping frame in the first area moves linearly in the direction of movement of the PIL and deforms, with the first Area can experience a shift in the direction of the axis of movement. This deformed first area has the effect of a long lever.

The second area at least partially comprises one of two opposite side surfaces of the clamping frame transverse to the direction of the longitudinal axis of the PIL. The second area can correspond to an area of the clamping frame which is not directly in contact with the clamping stack and is connected to the clamping stack by means of the first area. Because the clamping stack expands or changes its length in the direction of the movement axis when an electrical voltage is applied, the clamping stack presses against the clamping frame, so that the first area of the clamping frame moves and deforms in the direction of movement of the PIL. At the same time, the second area moves transversely to the axis of movement or longitudinal axis of the PIL and is deformed, with the second area being able to undergo a displacement transversely to the axis of movement. This deformed second area has the effect of a short lever.

The second region of the clamping frame is preferably in engagement with the guide unit when the clamping cell is in the resting state, i.e. in the state when no electrical voltage is applied to the clamping stack. By applying a voltage to the clamping stack and changing the shape of the clamping frame, the first area of the clamping frame is pivoted at least in areas towards the guide unit and the second area is moved away from the guide unit. In this way, the second area of the clamping frame can be detached from the guide unit. If the tension on the clamping stack is reduced or removed, the clamping stack and the clamping frame return to their original shapes. The first portion of the clamp frame is pivoted away from the guide unit and the second portion is moved toward the guide unit and is engageable with the guide unit. Thanks to the leverage effect, the maximum force and energy capacity of the piezoelectric clamping stack can be used. The maximum piezoelectric force of the clamp stack can be transmitted to the guide unit of the target object. Because of the leverage, it is even possible for the second section to be moved against a force that exceeds the maximum force of the piezoelectric clamping stack. In particular, it is possible for the second area of the clamping frame to exert a normal force on the guide unit that is greater than the maximum force of the piezoelectric clamping stack. Due to the leverage between the first area and the second area, the piezoelectric clamping stack can nevertheless deflect the second area against this normal force and thus release the contact between the piezoelectric clamping stack and the guide unit. A high adhesive force can thus be generated between the clamping frame and the guide element.

The piezoelectric inchworm linear motor according to the invention thus enables a large stroke and a large amount of force to be released. The piezo force in the direction of the movement axis is used directly without the need for the use of further structures with hinges. In this way, power losses due to the occurrence of mechanical friction are avoided. At the same time, miniaturization is made possible, so that no additional inertial masses or external mechanical clamping springs are required. The piezoelectric inchworm linear motor has a high reliability by excluding fragile elements such as hinges or pivot points from the construction by using clamping frames. In addition, the piezoelectric inchworm linear motor has high electromechanical energy efficiency, is self-clamping when not in use, and is simple in both design and implementation.

Preferably, the first clamping frame has a first coupling wall with a first engagement unit, and the second clamping frame has a second coupling wall with a second engagement unit, the engagement units being designed for engagement with the guide unit.

The first engagement unit can be formed as a first engagement groove and/or the second engagement unit can be formed as a second engagement groove. The engagement grooves can be in a coupling wall of the corresponding clamping frame stretch mens Preferably, the coupling wall is an outer wall of the frames, facing away from the interior of the frames and thus not in contact with the piezoelectric clamping stacks. The engagement grooves can extend at least partially over the outer wall. The two engagement grooves preferably extend over the entire outer wall and in a plane parallel to the movement axis. Furthermore, the engagement grooves can each have a first lateral contact surface and an opposite second contact surface, which extend parallel to the movement axis. The two lateral contact surfaces can delimit an inner contact surface. When the engagement unit is in engagement with the guide unit, the inner contact surface can bear against the guide unit and the two lateral contact surfaces can bear laterally on or surround the guide unit. The two lateral contact surfaces can thus in particular guide the clamping frame on the guide unit. The inner contact surface can preferably press against the guide unit with a predetermined normal force and thus generate the adhesive force between the inner contact surface and the guide unit.

The engagement units or the engagement grooves enable a secure and firm engagement and thus coupling of the clamping frame with the guide unit. When the clamping cell is in the idle state, when no electrical voltage is applied to the clamping stack, the engagement units enable secure engagement with the guide unit. The opposing lateral contact surfaces and the inner contact surface enable a particularly firm and secure engagement of the clamping frame with the guide unit, so that a high level of leverage and leverage are made possible. The high leverage allows the maximum force and energy capacity of the piezoelectric clamp stack to be used, so that the maximum piezoelectric stack force is transmitted to the guide unit of the target object.

The engagement units preferably come into frictional engagement with the guide unit as a result of the change in expansion of the piezoelectric clamping stacks or the change in size of the clamping frames.

In the idle state of the clamping cells, the engagement grooves can be in frictional engagement with the guide unit. In this case, a frictional force or an adhesive force can be exerted by the engagement grooves on the guide unit, so that the engagement grooves are coupled to the guide unit. If an electrical voltage is applied to a clamping stack, the engagement groove can be moved away from the guide unit due to the corresponding deformation of the clamping frame, in particular of the first area and the second area of the clamping frame. The adhesive force is reduced until the engagement groove is decoupled from the guide unit. As an alternative or in addition to a possible frictional connection between the respective engagement grooves and the guide unit, it is also possible for the respective engagement grooves to enter into a form fit with the guide unit.

The engagement grooves thus enable a particularly large frictional force between the clamping frame and the guide unit, so that the movement of the clamping frame and the guide unit against one another is prevented. This enables maximum power transmission from the clamping frame to the guide unit.

Preferably, the first clamp cell and the second clamp cell are located on opposite sides of the feed cell.

The first clamping cell, the second clamping cell and the feed cell can be arranged relative to one another in such a way that the cells extend along a common longitudinal axis of the PIL, which can correspond to the movement axis described above. Thus, the PIL may include a first end and a second end between which the longitudinal axis extends. The first clamp cell may be located at the first end and the second clamp cell may be located at the second end, wherein the feed cell may be located between the first end and the second end adjacent or adjacent to the two clamp cells and more preferably intermediately. In the direction of the axis of movement or in the direction of movement of the PIL, the first end is preferably the front end and the second end is preferably the rear end.

This arrangement of the clamping cells and the feed cell promotes a change in expansion of the piezoelectric stack and a change in size of the clamping frame in the direction of the longitudinal axis or in the direction of the axis of movement, preferably parallel to the alignment of the guide unit. This enables a compact and thus miniaturized design of the PIL. Furthermore, the two lateral clamping cells allow the PIL to be engaged or jammed with the guide unit. The feed cell enables the PIL to be displaced or reciprocated in a linear direction along the guide unit.

Preferably, by sequentially changing an electrical voltage across the piezoelectric clamp stacks and the feed stack, the clamp frames alternately engage and disengage from the guide unit this, so that the cells or the PIL perform a linear movement relative to the guide unit.

For example, by sequentially applying an electric voltage to the first piezoelectric clamp stack, the feed stack, and the second piezoelectric clamp stack, the first engagement unit and the second engagement unit of the two clamp stacks can be engaged with the guide unit in succession. In this way, the clamping frames or the clamping cell can be coupled to the guide unit one after the other. Correspondingly, the first engagement unit and the second engagement unit can be released from the guide unit again, so that the clamping frames or the clamping cell are not coupled to the guide unit. By applying an electrical voltage to the feed stack, the feed cell can bring about a feed of the respectively uncoupled clamping frame or the uncoupled clamping cell in the direction of the movement axis. In this way, the PIL can be moved in the direction of movement along the guide unit. It is also conceivable that the guide unit is moved in the direction of movement along the PIL by the sequential application of an electrical voltage to the piezoelectric clamping stacks and to the feed stack. This enables linear movement of the PIL and/or linear movement of the guide unit.

For example, a voltage can be applied to the first piezoelectric clamping stack so that it changes its size in the direction of the movement axis or longitudinal axis. Because the first piezoelectric clamping stack is at least partially in contact with the first clamping frame, the first clamping frame changes its shape, in particular the first area and the second area of the first clamping frame experience a change in shape. In this way, the first clamping cell can be detached from the guide unit. If a voltage is also applied to the feed stack, the feed stack changes its size in the direction of the movement axis and/or in the direction transverse to the movement axis, depending on the design of the feed frame. Thus, the PIL can be moved or shifted linearly in the direction of the movement axis.

Alternatively, a voltage can be applied to the second piezoelectric clamping stack (and the first clamping stack can be de-energized) so that it changes its size in the direction of the movement axis or longitudinal axis. Because the second piezoelectric clamping stack is at least partially in contact with the second clamping frame, the second clamping frame changes its shape, in particular the first area and the second area of the second clamping frame experience a change in shape. The second clamping cell can thus be detached from the guide unit. If a voltage is now applied to the feed stack, the feed stack changes its size in the direction of the axis of movement and/or in the direction transverse to the axis of movement. In this way, the PIL can be moved or shifted linearly in the direction of the movement axis.

If a voltage is applied sequentially to the first piezoelectric clamping stack and to the second piezoelectric clamping stack as described above, the clamping cells or clamping frames can be released sequentially from the guide unit. The PIL can be stepwise linearly moved back and forth in the direction of the movement axis by additionally applying a voltage to the piezoelectric feed stack.

The first clamping frame and the second clamping frame preferably have an oval-shaped cross-sectional area.

The first clamping frame and the second clamping frame can extend along a longitudinal axis of the clamping frame, with the clamping frames having an oval-shaped cross-sectional area in a plane along the longitudinal axis of the clamping frame. The clamping frames each have an interior space which is partially enclosed. Thus, the clamping frame can have a first open side and a second open side, which can be arranged opposite to the longitudinal axis of the clamping frame. The two open sides make it particularly easy to insert and remove the piezoelectric clamping stacks in the clamping frames. In addition, the open sides allow access to apply the electrical voltage. Furthermore, the clamping frame can have a first, essentially flat outer wall and a second, essentially flat outer wall. The first and second outer walls can be arranged opposite one another in a direction transverse to the longitudinal axis of the clamping frame. The first and second planar outer walls are preferably designed to rest against the target object or drive object.

The clamping frame can have a first, curved outer wall and a second, curved outer wall, which are arranged opposite one another in the direction of the longitudinal axis of the clamping frame. One of these curved outer walls may correspond to the coupling wall previously described and include the engagement groove previously described. It is also conceivable that both curved outer walls as coupling walls with the previously described NEN features are formed and each includes a guide unit with all the features described above. In this way, the clamping frames can be used in a more versatile manner by enabling engagement with a guide unit, in principle, with one of the engagement grooves or with both engagement grooves on the two opposite curved outer walls or coupling walls.

The shape of the first and second, curved outer walls are also advantageous for the leverage effect that is caused by the application of the electrical voltage to the piezoelectric clamping stacks and the resulting size changes in the piezoelectric clamping stacks and deformations of the clamping frames. The first area of the clamping frame experiences a displacement due to the curved outer walls or oval shape of the clamping frame, with the distance between the two opposite side surfaces of the clamping frame being able to be increased in the direction of the movement axis. The second area of the clamping frame is also shifted, in that the distance between the two opposite side surfaces of the clamping frame can be reduced transversely to the axis of movement. In this way, the maximum possible force can be exerted on the guide unit of the target object by means of the second area of the clamping frame, which leads to an improved stroke response.

The feed cell preferably includes a feed frame, the piezoelectric feed stack being arranged at least in regions, preferably completely, within the feed frame such that the piezoelectric feed stack is at least partially in contact with the feed frame and/or with the two clamping frames.

The feed cell can comprise a feed frame which can be connected or can be connected to the two clamping frames. The piezoelectric feed stack may be located within the feed frame. Because the piezoelectric feed stack is also arranged in a feed frame, which is connected or can be connected to the clamping frame, the maximum possible piezo force can be transmitted in the direction of movement without the need for additional structures with hinges. In this way, power losses due to the occurrence of mechanical friction are avoided. At the same time, miniaturization is made possible, so that no additional inertial masses or external mechanical clamping springs are required. The piezoelectric inchworm linear motor is thus more reliable because fragile elements such as hinges or pivot points are excluded from the construction by the clamping frames.

The feed frame preferably has an oval-shaped cross-sectional area.

The feed frame can have all the design features of the clamping frame described above, with the exception of the engagement unit. The feed frame can thus extend along a feed frame longitudinal axis, the feed frame having an oval-shaped cross-sectional area in a plane through the feed frame longitudinal axis. The feed frame may have an interior space that is partially enclosed. Thus, the feed frame can have a first open side and a second open side, which can be arranged opposite to the plane of the longitudinal axis of the feed frame. Due to the two open sides, the piezoelectric feed stack can be inserted into and removed from the feed frame particularly easily. In addition, the open sides allow access to apply the electrical voltage. Furthermore, the feed frame can have a first, essentially flat outer wall and a second, essentially flat outer wall. The first and second outer walls can be arranged opposite one another in a direction transverse to the longitudinal axis of the feed frame.

Like the clamping frames, the feed frame can have a first, curved outer wall and a second, curved outer wall, which are arranged opposite one another in the direction of the longitudinal axis of the feed frame. Instead of engagement grooves, both curved outer walls of the feed frame can each have a projection, the projections preferably extending in the plane of the longitudinal axis of the feed frame and extending away from the curved outer walls in opposite directions. The two projections can serve as connecting elements for connecting the feed frame to the two clamping frame frames. Thus, the projection or the connecting element of the first curved outer wall can be connected or can be connected to one of the two essentially flat outer walls of the first clamping frame. The projection or the connecting element of the second, curved outer wall can advantageously be connected or can be connected to one of the two essentially flat outer walls of the second clamping frame. This enables a PIL with a compact or miniaturized design.

If a voltage is now applied to the piezoelectric feed stack inside the feed frame, the piezoelectric feed stack undergoes a change in shape. Because the feed stack is at least partially in contact with the feed frame, the feed frame is deformed by the force transmission. In particular, the first area and the second area experience a change in shape. The first area at least partially comprises one of the two opposite side faces of the clamping frame, viewed transversely to the direction of the longitudinal axis of the PIL, on which a force is exerted by the expansion of the clamping stack. Because the feed stack expands or changes its length in the direction transverse to the movement axis when an electrical voltage is applied, the feed stack presses against the feed frame, so that the feed frame in the first area moves transverse to the direction of movement of the PIL and deforms, wherein the first area can experience an extension. This deformed first area has the effect of a long lever.

The second area at least partially comprises one of two opposite side surfaces of the feed frame in the direction of the longitudinal axis of the PIL. The second area can correspond to an area of the feed frame that is not directly in contact with the feed stack and is not connected to the feed stack. Because the feed stack expands or changes its length in the direction transverse to the movement axis when an electrical voltage is applied, the feed stack presses against the feed frame, so that the first area of the feed frame moves and deforms transverse to the direction of movement of the PIL. At the same time, the second area moves in the direction of the movement axis or longitudinal axis of the PIL and is deformed. This deformed second area has the effect of a short lever, so that a large force can be exerted in the direction of movement.

The volume or extent of the piezoelectric feed stack preferably corresponds to the volume or extent of the two piezoelectric clamping stacks. The feed stack is preferably offset by an angle of 90 degrees to the two clamp stacks in the PIL. The oval-shaped feed frame is used according to the principle of mechanical advantage. When using the oval-shaped feed frame, a stroke resolution in the nanometer range (nano-stroke resolution) is achieved by applying a voltage to the piezoelectric feed stack inside the feed frame. The oval-shaped feed frame and the oval-shaped clamping frame can have the same deformation behavior. A stroke resolution of between approximately 600 and 800 nanometers, particularly preferably approximately 800 nanometers, is possible. A stroke resolution of 600 nanometers is preferably possible with a mechanical load of 50 N. A stroke resolution of 800 nanometers is preferably possible with a mechanical load of 0 N.

The oval-shaped clamping frames at the two opposite ends of the PIL enable a clamping function with the target object. The oval-shaped feed frame in the middle between the two oval-shaped clamping frames enables an expansion function or feed function. The piezoelectric stacks can be inserted into the respective frames and configured to be arranged in the longitudinal mode or in the longitudinal direction or in the direction of the movement axis, thus enabling a maximum electromechanical coupling response.

Preferably, the feed frame has a folded structure.

The two opposite, flat outer walls of the feed frame can have a folded structure. The opposite, planar outer walls can be formed by a rod or a beam, which is specifically deformed so that it is bent back and forth in one plane. The opposite, flat outer walls preferably have a rectangularly folded structure in the plane of the outer wall. Thus, the rod can be folded back and forth between a first outer wall side and a second outer wall side, one fold having a substantially rectangular cross-sectional area. In the direction of the longitudinal axis of the feed frame, the opposite, flat outer walls can have at least one fold, which can be connected or is connected to the two clamping frames. The number of folds depends on the length of the piezoelectric piezo stack used. The two opposite, planar outer walls preferably have more than one fold, preferably between 2 and 20 folds, particularly preferably between 10 and 15 folds, more preferably fourteen folds. One of the folds of the opposite outer walls can be connected or connectable to the first clamping frame. Another of the folds of the opposite outer walls can be connected or connectable to the second clamping frame. However, fewer than fourteen folds are also conceivable. The two opposite, planar outer walls preferably extend in planes which are aligned parallel to one another. More preferably, the two outer walls extend in parallel planes in the entire area between the first and the second clamping frame.

The folded structure of the two opposite, flat outer walls of the feed frame enable a gentle or soft mechanism of the feed. Depending on the number of folds, lift responses of different sizes can be achieved. An embodiment of the feed frame, in which the opposite, planar outer walls have a fold, enables a stroke resolution in the nanometer range (nano-stroke resolution) by applying a voltage to the piezoelectric feed stack inside the feed frame. An embodiment of the feed frame, in which the opposite, flat outer walls have fourteen folds, can have a stroke resolution in the micrometer range (micro-stroke resolution). A stroke resolution of between about 1 and 8 micrometers, particularly preferably about 1.7 micrometers, is possible. A stroke resolution of 1.7 microns is preferably possible with a mechanical load of 50 N. A stroke resolution of 8 micrometers is preferably possible with a mechanical load of 0 N. An embodiment of the feed frame, in which the opposite, flat outer walls have two folds, can have a stroke resolution in the micrometer range (micro-stroke resolution). A stroke resolution of between about 1 and 2 micrometers, particularly preferably about 1.7 micrometers, is possible. A stroke resolution of 1.7 microns is preferably possible with a mechanical load of 50 N. A stroke resolution of 2 micrometers is preferably possible with a mechanical load of 0 N. The force value or the maximum possible force effect of the piezoelectric stack depends on the material of the piezoelectric stack and its size.

The oval-shaped clamping frames on the two opposite ends of the PIL enable a clamping function with the guide unit of the target object. The feed frame with the folded structure in the middle between the two oval-shaped clamping frames enables an expansion function or feed function. The piezoelectric stacks can be inserted into the respective frames and configured to be arranged in the longitudinal mode or in the longitudinal direction or in the direction of the movement axis, thus enabling a maximum electromechanical coupling response.

The volume or extent of the piezoelectric feed stack is preferably greater than the volume or extent of the two piezoelectric clamping stacks. The feed stack preferably has a volume that corresponds to the volume of the feed frame. The feed stack can thus be designed in such a way that it is in contact with the two clamping frames and with the two opposite, flat outer walls of the feed frame.

The feed cell preferably extends essentially in the direction of the axis of movement of the linear inchworm piezoelectric motor, with the two clamping cells extending essentially in a direction transverse to the axis of movement of the linear inchworm piezoelectric motor. The piezoelectric clamping stacks and the piezoelectric feed stack preferably extend parallel to one another and/or parallel to the movement axis. Preferably, the clamping piezoelectric stacks extend parallel to each other and/or parallel to the axis of movement, and the feed piezoelectric stack is oriented perpendicular to the clamping piezoelectric stacks and/or to the axis of movement. These configurations advantageously enable a linear movement of the PIL along the guide unit or a linear movement of the guide unit along the PIL in the direction of the axis of movement by the targeted application of an electrical voltage to the piezoelectric stack and the resulting change in size of the cells or frames. A PIL with a miniaturized and thus compact design is made possible.

Preferably, the two clamping frame cells or clamping frame frames and the feed cell or the feed frame are arranged relative to one another in such a way that the longitudinal axis of the feed frame is aligned in the direction of the axis of movement, and so that the two longitudinal axes of the clamping frame are aligned transversely, preferably perpendicularly, to the longitudinal axis of the feed frame. This enables a maximum feed force to be exerted in the direction of movement by applying a voltage to the piezoelectric feed stack and by applying the electrical voltage to the piezoelectric clamp stack and the resulting size changes in the piezoelectric clamp stack and deformation of the clamp frame, the maximum possible force in the second areas of the clamping frames are exerted on the guide unit of the target object. This enables an improved PIL that has a compact or miniaturized design and an improved stroke response.

The two clamping frames preferably form a monolithic structure with the feed frame.

The two clamping frames and the feed frame can be formed in one piece with one another and thus consist of one piece and can be manufactured in one piece. Furthermore, the three frames can be formed from the same material. The monolithic structure enables a compact or miniaturized design. Furthermore, force amplification and improved stroke response can be achieved while eliminating the need for large supports for piezoelectric stacks and hinges to connect these supports. Also, no nested frames need to be manufactured. On the one hand, this simplifies the manufacturing process of the PIL. On the other hand, the reliability of the PIL is improved by reducing mechanical losses due to internal stresses and bulky component sizes.

Preferably, the linear inchworm piezoelectric motor comprises or is formed of aluminum or stainless steel or titanium.

The piezoelectric inchworm linear motor can be made of different piezoelectric materials. All components of the piezoelectric inchworm linear motor are preferably made of the same piezoelectric materials. Thus, the piezoelectric stacks and the frames can be made of titanium, or of stainless steel, or of aluminum, or of a PZT5A-3195HD material. However, the piezoelectric stacks and frames may also include titanium, or stainless steel, or aluminum, or PZT5A-3195HD. For example, ferroelectrics such as barium titanate (BTO) and lead zirconate titanate (PZT) can be used. Quartz crystal SiO2, lithium niobate or gallium orthophosphate, berlinite, minerals from the tourmaline group, Seignette salt are also conceivable as piezoelectric crystals.

Piezoelectric ceramics made from synthetic, inorganic, ferroelectric and polycrystalline ceramic materials are also conceivable. Zinc oxide (ZnO) or aluminum nitrate (AlN) are conceivable as further piezoelectric materials. Like piezoelectric ceramics, plastic polyvinylidene fluoride (PVDF) can also be polarized and can then be used as a material for the piezoelectric stack.

The materials aluminium, stainless steel and titanium, or PZT5A-3195HD, are flexible and thus elastically deformable when an electrical voltage is applied. Due to the piezoelectric effect, these materials change their geometry and are particularly suitable as materials for the previously described piezoelectric inchworm linear motor. In addition, these materials are beneficial for energy transfer in the PIL.

The energy transfer occurs in different stages from the electrical input form in the piezoelectric stack to the mechanical output form at the target object to be actuated. The supplied electrical energy is converted by the piezoelectric stacks into a certain amount of mechanical energy, which is determined by the electromechanical coupling factor of the piezoelectric stacks. This factor depends on the mode of operation of the piezoelectric stack, normal mode (longitudinal and transverse) or shear mode.

For example, the PZT5A-3195HD material has an electromechanical coupling factor of 0.72 in normal mode (k33), while in shear mode (k15) it is 0.61. Few materials have a shear mode k15 larger than the normal k33 mode. In all cases it is possible to electrically configure the piezoelectric material in the mode with the highest electromechanical coupling factor. It is more efficient to use Normal mode instead of Shear mode. Therefore, it is important to choose a piezoelectric material that has a larger electromechanical coupling factor in the normal mode than in the shear mode.

The electrical energy converted to mechanical energy by the piezoelectric stack can be reduced due to mechanical bias loss either by a housing mechanism or by mechanical stress required for mechanical contacting. The mechanism can also be some kind of mechanical amplifier. However, the boost value should be clearly comparable to the case of a very soft mechanism that offers no power boost.

The final stage of energy transfer is when the resulting energy is transferred to the target after mechanical bias loss. This resultant energy is observed at the target as displacement and force actuation. The displacement coefficient of the piezoelectric stacks is generally larger in the shear mode than in the normal mode. For example, the material PZT5A-3195HD has a displacement coefficient of 350 pm/V in the longitudinal normal mode (d33) and 360 pm/V in the shear mode (d15). This means that operating the piezoelectric stacks in shear mode results in higher displacement behavior than in normal mode. However, the larger the deflection response, the smaller the associated force response. Knowing that the electromechanical In general, if the coupling factor in normal mode is greater than that in shear mode, then more mechanical energy can be dissipated in normal mode, and then more energy can be used for force actuation than displacement actuation. This force actuation can be done either directly on the target object or by mechanical friction. However, the latter leads to further energy losses as well as further low efficiency of the reaction.

Preferably, the first piezoelectric clamp stack and the second piezoelectric clamp stack have a height of about 1 mm to 4 mm, preferably about 2 mm, a width of about 2 mm to 5 mm, preferably about 3 mm, and a length of about 2 mm to 5 mm, preferably about 3 mm, and/or the feed stack has a height of about 1 mm to 4 mm, preferably about 2 mm or about 7 mm to 12 mm, preferably about 9 mm, a width of about 2 mm to 5 mm, preferably about 3 mm and a length of about 2 mm to 5 mm, preferably about 3 mm.

In the embodiment in which the two clamping frames and the feed frame each have an oval cross section, the PIL can have a volume of approximately 14×7×3 mm ³ . In the embodiment in which the two flat, opposite outer walls of the feed frame have a folded structure with a fold, the PIL can have a volume of approximately 8×7×3 mm ³ . In the embodiment in which the two flat, opposite outer walls of the feed frame have a folded structure with fourteen folds, the PIL can have a volume of approximately 15×7×3 mm ³ .

The dimensions of the piezoelectric stacks and the corresponding frames described above enable a PIL with a compact and thus miniaturized design while at the same time high power transmission to the target object and improved stroke response. With the embodiments described above, a miniaturized piezoelectric inchworm linear motor (PIL) with high efficiency and large force can be realized if the following features are taken into account: Implementation of piezoelectric stacks in the longitudinal direction of the PIL along the movement axis. In this way, the PIL can be operated in normal mode with a maximum electromechanical coupling factor. Implementation of mechanisms with very low mechanical preload and with mechanical advantages. Applying power actuation using a direct and frictionless configuration.

• 1A eine seitliche Ansicht eines ersten Ausführungsbeispiels eines piezoelektrischen Inchworm Linearmotors (PIL) mit zwei ovalförmigen Klemmrahmen und einem ovalförmigen Vorschubrahmen zeigt,
• 1B eine seitliche Ansicht des piezoelektrischen Inchworm Linearmotors aus der 1A zeigt, bei dem die piezoelektrischen Stapel jeweils in die Klemmrahmen und Vorschubrahmen eingefügt sind,
• 2A eine seitliche Ansicht eines zweiten Ausführungsbeispiels eines piezoelektrischen Inchworm Linearmotors mit zwei ovalförmigen Klemmrahmen und einem Vorschubrahmen mit gefalteter Struktur zeigt,
• 2B eine seitliche Ansicht des piezoelektrischen Inchworm Linearmotors aus der 2A zeigt, bei dem die piezoelektrischen Stapel jeweils in die Klemmrahmen und in den Vorschubrahmen eingefügt sind,
• 3A eine seitliche Ansicht eines dritten Ausführungsbeispiels eines piezoelektrischen Inchworm Linearmotors mit zwei ovalförmigen Klemmrahmen und einem Vorschubrahmen mit gefalteter Struktur zeigt,
• 3B eine seitliche Ansicht des piezoelektrischen Inchworm Linearmotors aus der 3A zeigt, bei dem die piezoelektrischen Stapel jeweils in die Klemmrahmen und in den Vorschubrahmen eingefügt sind,
• 4 eine seitliche Ansicht des piezoelektrischen Inchworm Linearmotors aus der 3A in Relation mit einem Zielobjekt zeigt,
• 5A und 5B die Formveränderung des piezoelektrischen Inchworm Linearmotors aus der 3B zeigen, wenn eine Spannung an den ersten piezoelektrischen Klemmstapel in dem ersten Klemmrahmen angelegt ist und keine mechanische Belastung vorliegt,
• 6A und 6B die Formveränderung des piezoelektrischen Inchworm Linearmotors aus der 3B zeigen, wenn jeweils eine Spannung an den ersten piezoelektrischen Klemmstapel in dem ersten Klemmrahmen und an den Vorschubstapel in dem Vorschubstapel angelegt ist und keine mechanische Belastung vorliegt,
• 7A und 7B die Formveränderung des piezoelektrischen Inchworm Linearmotors aus der 3B zeigt, wenn eine Spannung an den ersten piezoelektrischen Klemmstapel in dem ersten Klemmrahmen angelegt ist und eine mechanische Belastung mit einer Kraft von 50 N vorliegt, und
• 8A und 8B die Formveränderung des piezoelektrischen Inchworm Linearmotors aus der 3B zeigen, wenn jeweils eine Spannung an den ersten piezoelektrischen Klemmstapel in dem ersten Klemmrahmen und an den Vorschubstapel in dem Vorschubstapel angelegt ist und eine mechanische Belastung mit einer Kraft von 50 N vorliegt.

The present invention is explained below with reference to drawings showing only preferred exemplary embodiments, in which:

• 1A shows a side view of a first embodiment of a piezoelectric inchworm linear motor (PIL) with two oval-shaped clamping frames and an oval-shaped feed frame,
• 1B FIG. 14 is a side view of the linear inchworm piezoelectric motor of FIG 1A shows, in which the piezoelectric stacks are respectively inserted into the clamp frames and feed frames,
• 2A shows a side view of a second embodiment of a piezoelectric inchworm linear motor with two oval-shaped clamping frames and a feed frame with a folded structure,
• 2 B FIG. 14 is a side view of the linear inchworm piezoelectric motor of FIG 2A shows, in which the piezoelectric stacks are respectively inserted in the clamping frame and in the feed frame,
• 3A shows a side view of a third embodiment of a piezoelectric inchworm linear motor with two oval-shaped clamping frames and a feed frame with a folded structure,
• 3B FIG. 14 is a side view of the linear inchworm piezoelectric motor of FIG 3A shows, in which the piezoelectric stacks are respectively inserted in the clamping frame and in the feed frame,
• 4 FIG. 14 is a side view of the linear inchworm piezoelectric motor of FIG 3A in relation to a target object shows
• 5A and 5B the shape change of the piezoelectric inchworm linear motor from the 3B show when a voltage is applied to the first piezoelectric clamping stack in the first clamping frame and there is no mechanical load,
• 6A and 6B the shape change of the piezoelectric inchworm linear motor from the 3B show when a voltage is applied to the first piezoelectric clamping stack in the first clamping frame and to the feed stack in the feed stack and there is no mechanical load,
• 7A and 7B the shape change of the piezoelectric inchworm linear motor from the 3B shows when a voltage is applied to the first piezoelectric clamp stack in the first clamp frame and a there is a mechanical load with a force of 50 N, and
• 8A and 8B the shape change of the piezoelectric inchworm linear motor from the 3B show when a voltage is respectively applied to the first piezoelectric clamping stack in the first clamping frame and to the feed stack in the feed stack and a mechanical load with a force of 50 N is present.

1A and 1B show a first exemplary embodiment of a piezoelectric inchworm linear motor 1 according to the invention. The piezoelectric inchworm linear motor 1 comprises a first clamping cell 2, a second clamping cell 3 and a feed cell 5.

The first clamping cell 2 has a first clamping frame 7 and extends along a first longitudinal axis 9 of the clamping frame. The second clamping cell 3 has a second clamping frame 11 and, like the first clamping cell 2 , extends along a longitudinal axis 13 of the clamping frame. The feed cell 5 comprises a feed frame 15 which also has an oval cross-sectional area in the direction of a longitudinal axis 17 of the feed frame.

The first clamping cell 2 is arranged in the direction of a movement axis 19 or longitudinal axis 19 of the piezoelectric inchworm linear motor 1 at a first end 21, and the second clamping cell 3 is arranged in the direction of the movement axis 19 at a second end 23 of the piezoelectric inchworm linear motor 1. The feed cell 5 is arranged between the first clamping cell 2 and the second clamping cell 3 . In other words, the first clamp cell 2 and the second clamp cell 3 are arranged on opposite sides of the feed cell 5 .

The first clamping frame 7 has a first interior space 25 with a first piezoelectric clamping stack 27, the first piezoelectric clamping stack 27 being or being arranged in the first interior space 25 in such a way that the first piezoelectric clamping stack 27 is at least partially in contact with the first clamping frame 7 is in contact. The second clamping frame 11 has a second interior space 29 with a second piezoelectric clamping stack 31, the second piezoelectric clamping stack 31 being or being arranged in the second interior space 29 in such a way that the second piezoelectric clamping stack 31 is at least partially connected to the second clamping frame 11 is in contact.

The feed cell 5 has a third interior space 33 in which a piezoelectric feed stack 35 is arranged or can be arranged in such a way that the piezoelectric feed stack 35 is at least partially in contact with the feed frame 15 .

The interior spaces 25, 29, 33 of the three cells 2, 3, 5 are partially enclosed by the frames 7, 11, 15. Thus, each of the three frames 7, 11, 15 has a first open side 37 and a second open side 39, which are arranged opposite to the clamping frame longitudinal axes 9, 13 and the feed frame longitudinal axis 17 level.

Furthermore, the three frames 7 , 11 , 15 each have a first, essentially flat outer wall 41 and a second, essentially flat outer wall 43 . The first and second outer walls 41, 43 are arranged opposite one another in a direction transverse to the respective longitudinal axis 9, 13, 17 of the frame. A first of the essentially flat outer walls 41, 43 of the first clamping frame 7 and the second clamping frame 11 can be used to rest against a target object 45 or drive object 45 (not in the 1A and 1B shown) serve. The second of the essentially planar outer walls 41 , 43 of the first clamping frame 7 and the second clamping frame 11 can be used to abut or connect the clamping frames 7 , 11 to the feed frame 15 .

The piezoelectric feed stack 35 is at least indirectly in contact with the two clamping cells 2, 3 and connects or couples the two clamping cells 2, 3 to one another. In the in the 1A and 1B In the exemplary embodiment shown, the piezoelectric feed stack 35 is arranged in the feed frame 15, the feed frame 15 being connected to the two clamping frames 7 and 11. The two clamping cells 2, 3 and the feed cell 5 are arranged in series and along the movement axis 19 of the piezoelectric inchworm linear motor 1. Each piezoelectric clamping stack 27, 31 is arranged in the clamping cell 2, 3 in such a way that a change in an electrical voltage at the piezoelectric clamping stack 27, 31 causes a change in expansion of the piezoelectric clamping stack 27, 31 parallel to the axis of movement 19 and/or in the direction of the axis of movement 19 causes. As a result, the clamping frame 7, 11 undergoes a change in size essentially perpendicular to the direction of movement, and the clamping frame 7, 11 arrives with a guide unit 47 (not in the 1A 1 and 1b) engaged or disengaged from the guide unit 47.

The first clamping frame 7 has a first coupling wall 49 with a first engagement unit 51 and the second clamping frame 11 has a second coupling wall 53 with a second engagement unit 55, the engagement units 51, 55 being designed to engage with the guide unit 47 (not in 1A and 1B shown) are designed. Opposite the coupling walls 49, 53 viewed in the direction of the clamping frame longitudinal axis 9, 13, the clamping frames 7, 11 each have a further coupling wall, the further coupling walls being designed in accordance with the coupling walls 49, 53 and each having a further engagement unit, the further engagement units are designed according to the engagement units 51, 55. The clamping frames 7, 11 thus have a symmetrical structure.

The two engagement units 51, 55 are formed as engagement grooves 51, 55. The engagement grooves 51, 55 extend over the outer walls or coupling walls 49, 53 in a plane parallel to the movement axis 19. The engagement grooves 51, 55 each have a first lateral contact surface 57 and an opposite second contact surface 59, which are each parallel to the movement axis 19 extend and an inner contact surface 58 limit. Correspondingly, the further engagement units are designed as engagement grooves as previously described.

Due to the change in expansion of the piezoelectric clamping stacks 27, 31 or the change in size of the clamping frames 7, 11, the engagement units or engagement grooves 51, 55 with the guide unit 47 (not in the 1A and 1B shown) frictionally engaged.

Instead of engagement grooves, the feed frame 15 can have projections 61, the projections 61 preferably extending in the plane of the feed frame longitudinal axis 17 and extending away from curved outer walls of the feed frame 15 in opposite directions. The two projections 61 serve as connecting elements for connecting the feed frame 15 to the two clamping frames 7, 11. The feed frame 15 thus has a symmetrical structure.

The embodiment of the feed frame 5 described above, which has an oval cross-sectional area, enables a stroke resolution in the nanometer range (nano-stroke resolution) by applying a voltage to the piezoelectric feed stack 35 .

2A and 2 B show a second embodiment of a piezoelectric inchworm linear motor 1' according to the invention. The second embodiment of the piezoelectric inchworm linear motor 1' differs from the first embodiment of the piezoelectric inchworm linear motor 1 in FIGS 1A and 1B by the design of the feed cell 5' and its connection to the two clamping cells 2, 3. In addition, the piezoelectric feed stack 35' of the second embodiment is arranged at 90 degrees to the piezoelectric feed stack 35 of the first embodiment.

The two opposite, flat outer walls 41', 43' of the feed frame 5' have a folded structure 63. The opposite, flat outer walls 41', 43' are each formed by a deformed or bent rod 65, the deformed or bent rod 65 being bent back and forth in one plane.

The opposite, flat outer walls 41', 43' each have a rectangularly folded structure or fold 67. The curved rod 65 is folded back and forth between a first outer wall side 69 and a second outer wall side 71, the fold 67 having a substantially rectangular cross-sectional area. The fold 67 is connected to the two terminal frames 7, 11. The feed stack 35' arranged within the feed frame 5' is in direct contact with the two clamping frames 7, 11.

The embodiment of the feed frame 5', in which the opposite, flat outer walls 41', 43' each have a fold 67, enables a stroke resolution in the nanometer range (nano-stroke -Resolution).

3A and 3B show a third embodiment of a piezoelectric inchworm linear motor 1" according to the invention. The third embodiment of the piezoelectric inchworm linear motor 1" differs from the second embodiment of the piezoelectric inchworm linear motor 1' in FIGS 2A and 2 B due to the design of the feed cell 5".

The two opposite, flat outer walls 41", 43" have a large number 69 of folds. The plurality 69 of folds includes fourteen folds. Outer planar wall 41" includes seven folds and outer planar wall 43" includes seven folds. There are therefore fourteen folds in total. A first of the plurality 69 of folds is with the first Clamping frame 7 connected. The second of the plurality 69 of folds is connected to the second clamping frame 11 .

The configuration of the feed frame 5", in which the opposite, flat outer walls 41", 43" have a large number 69 of folds, in particular fourteen folds, enables a stroke resolution in the micrometer range (micro-stroke resolution).

4 shows an exemplary orientation of the second embodiment of a piezoelectric inchworm linear motor 1" from FIGS 3A and 3B with the target object or drive object 45 and the guide unit 47. The guide unit 47 is designed as a guide frame or guide housing, which extends along a guide housing longitudinal axis 71 or guide unit longitudinal axis 71 between a first end 73 and an opposite second end 75. One of the two ends has an opening 77 through which the driving object 45 extends, so that the driving object 45 extends partly inside the guide unit 47 and partly outside. A spring element or tension element 79 can be provided at the second end 75 . The piezoelectric inchworm linear motor 1" is arranged in the guide unit or in the guide housing 47 in such a way that the piezoelectric inchworm linear motor 1" extends along the guide unit longitudinal axis 71 and the movement axis 19 runs in the direction of the guide unit longitudinal axis 71. A flat outer wall 41 of the first clamping frame 7 bears against the target object 45 and can drive it. The guide units 47 of the two clamping frames 7, 11 can engage with the guide unit 47 laterally. By sequentially changing an electrical voltage across the piezoelectric clamp stacks 27, 31 and the feed stack 35'', the clamp frames 7, 11 alternately engage and disengage from the guide unit 47 so that the stacks 27, 31, 35'' relatively perform a linear movement to the guide unit 47 .

In all of the previously described embodiments of the piezoelectric inchworm linear motor 1, 1', 1", the feed cell 5, 5', 5" extends essentially in the direction of the movement axis 19 of the piezoelectric inchworm linear motor 1, 1', 1" and the two clamping cells 2 , 3 extend essentially in a direction transversely at an angle of 90 degrees to the movement axis 19 of the piezoelectric inchworm linear motor 1, 1', 1". The two clamping frames 7, 11 each form a monolithic structure with the feed frame 15, 15′, 15″. The piezoelectric inchworm linear motor 1, 1′, 1″ can comprise aluminum or stainless steel or titanium or be made of aluminum or stainless steel or titanium.

The first piezoelectric clamp stack 27 and the second piezoelectric clamp stack 31 of the three embodiments of the piezoelectric inchworm linear motor 1, 1', 1" (see 1B , 2 B and 3B) have a height of about 2 mm, a width of about 3 mm and a length of about 3 mm. The feed stack 35, 35' of the first and second embodiments of the piezoelectric inchworm linear motor 1, 1' (see Fig 1B and 2 B) has a height of about 2 mm, a width of about 3 mm and a length of about 3 mm. The feed stack 35" of the third embodiment of the piezoelectric inchworm linear motor 1" (see 3B) has a height of about 9 mm, a width of about 3 mm and a length of about 3 mm.

5A until 8B each show simulations of the shape changes of the piezoelectric inchworm linear motor 1" based on the finite element method (FEM) for different initial conditions 5A until 8B The Z-direction shown corresponds to the direction along the movement axis 19, and the Y-direction shown corresponds to the direction which is perpendicular to the movement axis 19. All in the 5A until 8B The simulations shown are based on an electrical voltage being applied to the first piezoelectric clamping stack 27 and show how a first region 81 and a second region 83 of the first clamping frame 7 experience a displacement in the Z direction and in the Y direction.

5A and 5B 11 respectively show the Y-direction and Z-direction shape change of the piezoelectric linear inchworm motor 1" under the following conditions: the second clamp cell 3 is fixed, a voltage of 75 V is applied to the first clamp piezoelectric stack 27 in the first clamp frame 7, and there is no mechanical stress No mechanical stress means that an end of the drive object 41 that is in the 4 as shown protruding from the guide unit 47 is a free end 42 where there is no load. In this case, the full force of the PIL 1" acts on the drive object 45.

In the in the 5A and 5B In the FEM simulation shown, the piezoelectric inchworm linear motor 1" expanded by a maximum of 2.1 µm in the Z direction in the first area 81 under an operating voltage of 75 V. The first clamping frame 7 showed a lateral deformation in the second area 83 between -0.4 and -0.6 µm under the same operating voltage.The first area 81 experiences thus a displacement in the Z-direction, whereas the second area 83 undergoes a displacement in the Y-direction. This lateral displacement or displacement is sufficient to release the piezoelectric inchworm linear motor 1" from the clamped state.

6A and 6B each show the shape change of the piezoelectric inchworm linear motor 1" in the Y-direction and Z-direction under the following conditions: the second clamp cell 3 is fixed, a voltage of 75 V is applied to the first piezoelectric clamp stack 27 in the first clamp frame 7 and applied to the feed pile 35" in the feed frame 15".

In the in the 6A and 6B In the FEM simulation shown, the piezoelectric inchworm linear motor 1" expanded by a maximum of 10.1 µm in the Z direction in the first area 81 under an operating voltage of 75 V. The first clamping frame 7 showed a lateral displacement in the second area 83 between -0.4 and -0.6 µm under the same operating voltage. The first area 81 thus undergoes a displacement in the Z direction, whereas the second area 83 undergoes a displacement in the Y direction. This lateral displacement or displacement is sufficient to move the piezoelectric inchworm linear motor 1" out of the to solve the stuck condition.

7A and 7B 11 respectively show the Y-direction and Z-direction shape change of the piezoelectric linear inchworm motor 1" under the following conditions: the second clamp cell 3 is fixed, a voltage of 75 V is applied to the first clamp piezoelectric stack 27 in the first clamp frame 7, and there is a 50 N mechanical load.

In the in the 7A and 7B According to the FEM simulation shown, the piezoelectric inchworm linear motor 1" expanded by a maximum of 1.14 µm in the Z direction in the first area 81 under an operating voltage of 75 V and a mechanical load of 50 N. The first clamping frame 7 showed a lateral deformation in the second area 83 between -0.1 and -0.3 µm under the same mechanical load and operating voltage.The first area 81 thus experiences a displacement in the Z direction, whereas the second area 83 experiences a displacement in the Y direction.This lateral displacement or displacement is sufficient to to release the piezoelectric inchworm linear motor 1" from the clamped state.

8A and 8B each show the shape change of the piezoelectric inchworm linear motor 1" in the Y-direction and Z-direction under the following conditions: the second clamp cell 3 is fixed, a voltage of 75 V is applied to the first piezoelectric clamp stack 27 in the first clamp frame 7 and applied to the feed stack 35" in the feed frame 15" and there is a 50 N mechanical load.

In the in the 8A and 8B According to the FEM simulation shown, the piezoelectric inchworm linear motor 1" expanded by a maximum of 9.14 µm in the Z direction in the first area 81 under an operating voltage of 75 V and a mechanical load of 50 N. The first clamping frame 7 showed a lateral deformation in the second area 83 between -0.1 and -0.3 µm under the same mechanical load and operating voltage The first area 81 thus undergoes a displacement in the Z direction, whereas the second area 83 undergoes a displacement in the Y direction.This lateral displacement is sufficient to move the piezoelectric inchworm to release the linear motor 1" from the clamped state.

The previously described embodiments of a piezoelectric inchworm linear motor 1, 1', 1" enable a large stroke and a large force release. The piezo force in the direction of the movement axis 19 is used directly without the need for the use of further structures with hinges avoided by the occurrence of mechanical friction. At the same time, miniaturization is made possible, so that no additional inertia masses or external mechanical clamping springs are required. The piezoelectric inchworm linear motor 1, 1 ', 1 "in accordance with the invention has a high degree of reliability, in that fragile elements such as hinges or Pivot points are excluded from the construction by using clamping frames. In addition, the piezoelectric inchworm linear motor 1, 1′, 1″ according to the invention has a high electromechanical energy efficiency and is simple both in design and in implementation.

reference list

1, 1', 1"

piezoelectric inchworm linear motor

2

first clamp cell

3

second clamp cell

5, 5', 5"

feed cell

7

first clamping frame

9

first longitudinal axis of the clamping frame

11

second clamping frame

13

second clamping frame longitudinal axis

15, 15', 15"

feed frame

17

feed frame longitudinal axis

19

motion axis

21

first end of the piezoelectric inchworm linear motor

23

second end of the piezoelectric inchworm linear motor

25

first interior

27

first piezoelectric clamp stack

29

second interior

31

second piezoelectric clamp stack

33

third interior

35, 35', 35"

piezoelectric feed stack

37

first open side of the frame

39

second open side of the frames

41, 41', 41"

first, flat outer wall

42

free end

43, 43', 43"

second, flat outer wall

45

Target object or drive object

47

Guide unit

49

first coupling wall

51

first intervention unit

53

second coupling wall

55

second engagement unit

57

first lateral contact surface

58

inner contact surface

59

second lateral contact surface

61

protrusions

63

folded structure

65

deformed or bent rod

67

rectangular folded structure or fold

69

variety of folds

71

Guide unit longitudinal axis

73

first end

75

second end

77

opening

79

Spring element or tension element

81

first area

83

second area

Claims (10)

Piezoelectric inchworm linear motor (1, 1', 1"), comprising: a first clamp cell (2) with a first clamp frame (7) and a first piezoelectric clamp stack (27), the first piezoelectric clamp stack (27) being located within the first clamp frame (7 ) is arranged such that the first piezoelectric clamp stack (27) is at least partially in contact with the first clamp frame (7), a second clamp cell (3) having a second clamp frame (11) and a second piezoelectric clamp stack (31), wherein the second piezoelectric clamp stack (31) is arranged within the second clamp frame (11) in such a way that the second piezoelectric clamp stack (31) is at least partially in contact with the second clamp frame (11), and a feed cell (5, 5', 5 ") with a piezoelectric feed stack (35, 35', 35"), wherein the piezoelectric feed stack (35, 35', 35") is at least indirectly in contact with the two clamping cells (2, 3) and the two clamping cells en (2, 3) are connected or coupled to one another, the two clamping cells (2, 3) and the feed cell (5, 5', 5") being connected in series and along a movement axis (19) of the piezoelectric inchworm linear motor (1, 1', 1"), each piezoelectric clamping stack (27, 31) being arranged in the clamping cell (2, 3) in such a way that a change in an electrical voltage on the piezoelectric clamping stack (2, 3) causes a change in expansion of the piezoelectric Clamping stack (2, 3) parallel to the movement axis (19), so that the clamping frame (7, 11) undergoes a change in size essentially perpendicular to the movement axis (19), and so that the clamping frame (7, 11) is connected to a guide unit ( 47) comes into engagement or the engagement is released, and wherein the feed stack (35, 35', 35") is arranged transversely to the movement axis (19), so that by applying an electrical voltage to the feed stack (35, 35', 35 ") the feed stack (35, 35', 35") undergoes a change in length transversely to the movement axis (19). Piezoelectric inchworm linear motor (1, 1', 1") according to claim 1 , wherein the first clamping frame (7) has a first coupling wall (49) with a first engaging unit (51), wherein the second clamping frame (11) has a second coupling wall (53) with a second engaging unit (55), and wherein the engaging units ( 51, 55) are designed to engage with the guide unit (47). Piezoelectric inchworm linear motor (1, 1', 1") according to claim 2 , the engagement units (51, 55) frictionally engaging with the guide unit (47) as a result of the change in expansion of the piezoelectric clamp stacks (27, 31) or the change in size of the clamp frames (7, 11). Piezoelectric inchworm linear motor (1, 1', 1") according to any one of the preceding claims, wherein the first clamp cell (2) and the second clamp cell (3) are arranged on opposite sides of the feed cell (5, 5', 5"). Piezoelectric inchworm linear motor (1, 1', 1") according to one of the preceding claims, wherein by sequentially changing an electrical voltage on the piezoelectric clamping stacks (27, 31) and on the piezoelectric feed stack (35, 35', 35"), the Clamping frames (7, 11) alternately engage and disengage from the guide unit (47) so that the piezoelectric inchworm linear motor (1, 1', 1") performs a linear movement relative to the guide unit (47). Piezoelectric inchworm linear motor (1, 1', 1") according to one of the preceding claims, wherein the first clamping frame (7) and the second clamping frame (11) have an oval-shaped cross-sectional area. Piezoelectric inchworm linear motor (1, 1', 1") according to one of the preceding claims, wherein the feed cell (5, 5', 5") comprises a feed frame (15, 15', 15"), wherein the piezoelectric feed stack (35, 35', 35") is arranged within the feed frame (15, 15', 15") in such a way that the piezoelectric feed stack (35, 35', 35") is at least partially connected to the feed frame (15, 15', 15"). and/or is in contact with the two clamping frames (7, 11). Piezoelectric inchworm linear motor (1, 1', 1") according to claim 7 wherein the feed frame (15) has an oval-shaped cross-sectional area or wherein the feed frame (15', 15") has a folded structure. Piezoelectric inchworm linear motor (1, 1', 1") according to one of the preceding claims, wherein the feed cell (5, 5', 5") moves essentially in the direction of the axis of movement (19) of the piezoelectric inchworm linear motor (1, 1', 1") extends, wherein the two clamping cells (2, 3) extend substantially in a direction transverse to the movement axis (19) of the piezoelectric inchworm linear motor (1, 1', 1"), and/or wherein the piezoelectric clamping stacks (27, 31) extend parallel to each other and/or parallel to the movement axis (19) and the piezoelectric feed stack (35, 35', 35") perpendicular to the piezoelectric clamping stacks (27, 31) and/or to the Movement axis (19) is aligned. Piezoelectric inchworm linear motor (1, 1', 1") according to one of Claims 7 until 9 , wherein the two clamping frames (7, 11) form a monolithic structure with the feed frame (15, 15', 15") and/or wherein the piezoelectric inchworm linear motor (1, 1', 1") comprises aluminum or stainless steel or titanium or is made of aluminum or stainless steel or titanium, and/or wherein the first piezoelectric clamping stack (27) and the second piezoelectric clamping stack (31) have a height of about 2 mm, a width of about 3 mm and a length of about 3 mm, and/or wherein the feed stack (15, 15', 15") has a height of about 2 mm or of about 9 mm, a width of about 3 mm and a length of about 3 mm.

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