DE102020002199A1 - Piezoelectric inchworm linear motor - Google Patents

Abstract

Shown and described is a piezoelectric inchworm linear motor (1, 1 ', 1 ") comprising: a first clamping cell (2) with a first clamping frame (7) and a first piezoelectric clamping stack (27), a second clamping cell (3) with a second Clamping frame (11) and a second piezoelectric clamping stack (31), 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 terminal cells (2, 3) and connects the two terminal cells (2, 3) to one another or couples them to one another, the two terminal cells (2, 3) and the feed cell (5, 5 ', 5 ") are arranged in series and along a movement axis (19) of the piezoelectric inchworm linear motor (1, 1 ', 1"), with each piezoelectric clamping stack (27, 31) being arranged in this way in the clamping cell (2, 3), see above that a change in an electrical voltage on the piezoelectric clamping tape l (2, 3) causes a change in expansion of the piezoelectric clamping stack (2, 3) parallel to the axis of movement (19), so that the clamping frame (7, 11) undergoes a change in size essentially perpendicular to the direction of movement (19), and so that the Clamping frame (7, 11) engages with a guide unit (47) or the engagement is released.

Description

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

An inchworm linear motor uses piezoelectric actuators or stacks to move a guide unit, for example a shaft, with a precision in the nanometer range or to move along a guide unit, for example a shaft, with a precision in the nanometer range. Due to its low mass and small volume, the Inchworm linear motor is used in particular in medical technology, for example in orthopedics and maxillofacial surgery, e.g. for the implementation of callus distractor implants. In addition, the Inchworm linear motor is often used in scanning tunneling microscopes. A scanning tunneling microscope requires control of a scanning tip in the nanometer range in the vicinity of the material being observed.

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

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

Various designs of piezoelectric linear motors are known from the prior art. Many of the embodiments allow a compact size and a large lifting capacity, although the drive force reaction is rather low. Motors and actuators developed on the basis of the force amplification mechanism exhibit better drive force response, which is essential for applications where a large actuation force is the critical factor. However, these motors and actuators have a smaller stroke response or lower stroke capacity. The term “stroke” means the path that the piezoelectric feed stack of the piezoelectric inchworm motor travels back and forth along the guide unit.

The linear piezoelectric motors developed on the basis of a force amplification mechanism have a better force response, which is crucial for applications where a large actuating force is the critical factor. However, the stroke response is smaller and the application of more control pulses is necessary in order to achieve a large deflection or a large feed. The internal mechanical stress on the mechanism, either in the event of deflection or force amplification, affects the overall efficiency of the motor.

The actuation force applied to the load or guide unit 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 increased and vice versa.

Approaches to force amplification are known from the prior art, which either use large supports for piezoelectric stacks that are connected by tiny hinges ( US 2014/0333180 A1 ), or on nested frames ( US 2012/0119620 A1 ) are based. 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 enables both a large stroke and a large force release.

Starting from the prior art, it is therefore the object of the present invention to provide an improved piezoelectric inchworm linear motor which enables a large stroke and a large force release.

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, a piezoelectric inchworm linear motor is provided, the piezoelectric inchworm linear motor comprising: a first clamp cell with a first clamp frame and a first piezoelectric clamp stack, wherein the first piezoelectric clamp stack is arranged 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 with a second clamping frame and a second piezoelectric clamping stack, wherein the second piezoelectric clamping stack is 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 the two clamp cells to one another or couples them 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 clamping stack is arranged in the clamping cell in such a way that a change in an electrical voltage on the piezoelectric clamping stack causes a change in expansion of the piezoelectric clamping stack parallel to the axis of movement, so that the clamping frame undergoes a change in size essentially perpendicular to the direction of movement, and so that the clamping 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; 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 transversely or perpendicular to the axis of movement. 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 of an electrical voltage. As a rule, a conventional piezo stack expands when an electrical voltage is applied, in particular in a preferred direction. Depending on the arrangement of the piezo stack, the expansion can thus be parallel to the axis of movement or transversely 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 transversely to the axis of movement. Opposite side surfaces of the stacks can thus have a changed distance from one another due to the change in expansion.

A piezo stack as it 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, which expands in the direction of thickness and contracts in the transverse direction when a voltage is applied. The deformation persists as long as the voltage is applied. If there are no changing external forces, no energy is required to maintain the deformation. If the voltage is reversed, the direction of the deformation changes - in this case, contraction in the direction of thickness and expansion in the transverse direction.

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

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

The expansion change of the piezoelectric clamping stack can take place in both directions 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 clamping stacks and the feed stack can be arranged in series 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 clamping stacks and / or the feed stack, one or both of the the two clamping stacks and / or the feed stack experience a change in length along the longitudinal axis of the PIL. However, it is also conceivable that, for example, 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 when an electrical voltage is applied to the feed stack, the feed stack experiences a 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. The piezoelectric inchworm linear motor preferably moves parallel to the guide unit. Due to the expansion capability of the feed stack in the longitudinal direction or in the direction of the movement axis, the piezo force in the longitudinal direction (longitudinal piezo 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 clamping stack, the clamping 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, if necessary, is shortened transversely to the longitudinal axis of the PIL or transversely to the axis of movement. In other words, the distance between opposite side surfaces of the clamping stack in the direction of the longitudinal axis of the PIL is increased. Due to the mechanical properties of the clamping stack, the distance between opposite side surfaces of the PIL can be shortened transversely, in particular perpendicular to the longitudinal axis. As a result of this change in expansion of the clamping stack, the clamping frame in turn experiences 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 change in expansion of the piezoelectric clamping stack also deforms the clamping frame relative to the movement axis, i.e. in the direction of the movement axis or parallel to the movement axis and perpendicular to the movement axis. The deformation of the clamping frame takes place through the change in length of the piezoelectric clamping stack, whereby a force is exerted on the clamping frame in the direction of the axis of movement. This has the effect that the size or the shape of the clamping frame is changed. In other words, the extent of the clamping frame is lengthened in the direction of the axis of movement and shortened transversely or perpendicular to the axis of movement. 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 axis of movement is increased, and the distance between opposite side surfaces of the clamping frame transversely or perpendicular to the longitudinal axis of the PIL is shortened.

By deforming or changing the size of the clamping frame, the clamping frame can come into engagement with the guide unit or the engagement can be released from the guide unit. Because the size of the clamping frame is shortened in the direction perpendicular to the axis of movement and lengthened in the direction of the axis of movement, a leverage effect is produced. A first area of the clamping frame has the effect of a long lever, whereas a second area of the clamping frame has the effect of a short lever.

The first area 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 its length changes when an electrical voltage is applied in the direction of the axis of movement, 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 is deformed 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 in direct contact with the clamping stack and is connected to the clamping stack by means of the first area. Because the clamping stack expands or its length changes when an electrical voltage is applied in the direction of the movement axis, 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 experience a displacement transverse 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 in the rest state of the clamping cell, that is to say 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 partially 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 area of the clamping frame is from the guide unit pivoted away and the second area is moved towards the guide unit and can come into engagement with the guide unit. The lever effect allows the maximum force and energy capacity of the piezoelectric terminal stack to be used. The maximum piezoelectric force of the clamp stack can be transmitted to the guide unit of the target object. Due to the leverage effect, it is even possible that the second area is 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 which 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. In this way, a high adhesive force can 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 force release. The piezo force in the direction of the movement axis is used directly without the need for additional structures with hinges. This avoids power losses due to the occurrence of mechanical friction. At the same time, miniaturization is made possible, so that no additional inertial masses or external mechanical clamping springs are required. The inchworm piezoelectric linear motor has a high level 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 has a high electromechanical energy efficiency, is self-clamping in the idle state and is simple both in construction and in implementation.

The first clamping frame preferably 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 designed as a first engagement groove and / or the second engagement unit can be designed as a second engagement groove. The engagement grooves can extend in a coupling wall of the corresponding clamping frame. The coupling wall is preferably an outer wall of the frame which faces away from the interior of the frame and is therefore not in contact with the piezoelectric terminal 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 axis of movement. Furthermore, the engagement grooves can each have a first lateral contact surface and an opposing second contact surface, which extend parallel to the axis of movement. 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 rest against the guide unit and the two lateral contact surfaces can rest laterally against the guide unit or surround it. 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 secure and firm engagement and thus coupling of the clamping frame to the guide unit. In the idle state of the terminal cell, when no electrical voltage is applied to the terminal stack, the engagement units enable secure engagement with the guide unit. The opposite 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 leverage effect and leverage are made possible. Due to the high leverage, the maximum force and energy capacity of the piezoelectric clamping stack can be used, so that the maximum piezoelectric stacking force is transmitted to the guide unit of the target object.

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

In the rest state of the clamping cells, the engagement grooves can be frictionally engaged 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 clamp stack, the engagement groove can be moved away from the guide unit due to the corresponding deformation of the clamp frame, in particular of the first area and the second area of the clamp 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.

The first clamping cell and the second clamping cell are preferably arranged on opposite sides of the feed cell.

The first clamping cell, the second clamping cell and the feed cell can be arranged with respect to one another such that the cells extend along a common longitudinal axis of the PIL, which can correspond to the axis of movement described above. Thus, the PIL can comprise a first end and a second end, between which the longitudinal axis extends. The first clamping cell can be arranged at the first end and the second clamping cell can be arranged at the second end, wherein the feed cell can be arranged between the first end and the second end adjoining or adjacent to the two clamping cells and more preferably in between. 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 favors a change in expansion of the piezoelectric stacks 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 enable the PIL to be engaged with or clamped to the guide unit. The feed cell enables the PIL to be shifted or to move back and forth in a linear direction along the guide unit.

By sequentially changing an electrical voltage on the piezoelectric clamping stacks and on the feed stack, the clamping frames alternately engage and detach from the guide unit, so that the cells or the PIL execute a linear movement relative to the guide unit.

For example, by successively applying an electrical voltage to the first piezoelectric clamping stack, the feed stack and the second piezoelectric clamping stack, the first engagement unit and the second engagement unit of the two clamping stacks can successively engage the guide unit. In this way, the clamping frame or the clamping cell can couple with the guide unit one after the other. Correspondingly, the first engagement unit and the second engagement unit can be released again from the guide unit, 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 terminal cell in the direction of the movement axis. The PIL can thus be moved in the direction of movement along the guide unit. It is also conceivable that the sequential application of an electrical voltage to the piezoelectric clamping stacks and to the feed stack moves the guide unit in the direction of movement along the PIL. This enables a linear movement of the PIL and / or a 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 axis of movement 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 released from the guide unit. There is also a tension on the feed pile applied, 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. The PIL can thus 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 is de-energized) so that it changes its size in the direction of the axis of movement 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 released 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 movement axis and / or in the direction transverse to the movement axis. 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. By additionally applying a voltage to the piezoelectric feed stack, the PIL can be moved back and forth linearly in steps in the direction of the movement axis.

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, 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. The clamping frame can thus have a first open side and a second open side, which can be arranged opposite to the longitudinal axis of the clamping frame. Due to the two open sides, the piezoelectric clamping stacks can be inserted into and removed from the clamping frames particularly easily. In addition, the open sides provide access for applying 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 flat 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 can correspond to the coupling wall described above and comprise the engagement groove described above. It is also conceivable that both curved outer walls are designed as coupling walls with the features described above and each include a guide unit with all the features described above. The clamping frames can thus be used in a more versatile manner, in that engagement with a guide unit is made possible in principle with one of the engagement grooves or with both engagement grooves on the two opposing curved outer walls or coupling walls.

The shape of the first and second, curved outer walls are also advantageous for the leverage effect caused by the application of the electrical voltage to the piezoelectric clamping stacks and the resulting changes in size of the piezoelectric clamping stacks and deformations of the clamping frames. The first area of the clamping frame is displaced by the curved outer walls or oval shape of the clamping frame, it being possible to increase the distance between the two opposite side surfaces of the clamping frame in the direction of the axis of movement. The second area of the clamping frame also experiences a shift in that the distance between the two opposite side surfaces of the clamping frame can be reduced across the axis of movement. The maximum possible force can thus be exerted on the guide unit of the target object by means of the second region of the clamping frame, which leads to an improved lifting response.

The feed cell preferably comprises a feed frame, the piezoelectric feed stack being arranged at least in some areas, preferably completely within the feed frame, so 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 or can be connected to the two clamping frames. The piezoelectric feed stack can be arranged within the feed frame. Because the piezoelectric feed stack is also arranged in a feed frame which is 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 further structures with hinges. This avoids power losses due to the occurrence of mechanical friction. 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 frame.

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

The feed frame can have all the design features of the previously described clamping frames 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 can have an interior space which 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 feed frame longitudinal axis. 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 provide access for applying 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.

The feed frame, like the clamping frames, 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 engaging 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 or can be connected to one of the two, essentially flat outer walls of the first clamping frame frame. The projection or the connecting element of the second, curved outer wall can advantageously be connected or connectable to one of the two essentially flat outer walls of the second clamping frame 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 experiences 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. In this case, the first area at least partially comprises one of the two opposite side surfaces of the clamping frame, seen 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 axis of movement when an electrical voltage is applied, the feed stack presses against the feed frame, so that the feed frame moves and deforms in the first area transversely to the direction of movement of the PIL, whereby the first area can be extended. 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 which is not in direct 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 axis of movement 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 transversely to the direction of movement of the PIL. At the same time, the second area moves in the direction of the axis of movement or the 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 the extent of the piezoelectric feed stack preferably corresponds to the volume or the extent of the two piezoelectric clamping stacks. The feed stack is preferably arranged offset by an angle of 90 degrees with respect to the two clamping stacks in the PIL. The oval-shaped feed frame is used according to the principle of mechanical strength 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 between approximately 600 and 800 nanometers, particularly preferably approximately 800 nanometers, is possible. A stroke resolution of 600 nanometers is possible with a mechanical load of 50N. 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 make it possible to do this of the PIL has 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 and configured in the corresponding frames in such a way that they are arranged in the longitudinal mode or in the longitudinal direction or in the direction of the movement axis and thus enable a maximum electromechanical coupling reaction.

The feed frame preferably has a folded structure.

The two opposite, flat outer walls of the feed frame can have a folded structure. The opposite, flat outer walls can be formed by a rod or a bar which is deliberately 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. The rod can thus be folded back and forth between a first outer wall side and a second outer wall side, one fold having an essentially 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 or is connected to the two clamp frames. The number of folds depends on the length of the piezoelectric piezo stack used. The two opposite, flat 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, flat outer walls preferably extend in planes which are aligned parallel to one another. Furthermore, the two outer walls preferably 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 allow a gentle or soft mechanism of the feed. Depending on the number of folds, lift responses of different sizes can be achieved. For example, an embodiment of the feed frame in which the opposite, flat outer walls are folded, 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 between approximately 1 and 8 micrometers, particularly preferably approximately 1.7 micrometers, is possible. A stroke resolution of 1.7 micrometers 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 between approximately 1 and 2 micrometers, particularly preferably approximately 1.7 micrometers, is possible. A stroke resolution of 1.7 micrometers 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 stacks depend on the material of the piezoelectric stacks and on their size.

The oval-shaped clamping frames at 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 and configured in the corresponding frames in such a way that they are arranged in the longitudinal mode or in the longitudinal direction or in the direction of the movement axis and thus enable a maximum electromechanical coupling reaction.

The volume or the extent of the piezoelectric feed stack is preferably greater than the volume or the 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 piezoelectric inchworm linear motor, the two clamping cells essentially extending in a direction transverse to the axis of movement of the linear piezoelectric inchworm motor. The piezoelectric clamping stacks and the piezoelectric feed stack preferably extend parallel to one another and / or parallel to the axis of movement. The piezoelectric clamping stacks preferably extend parallel to one another and / or parallel to the axis of movement and the piezoelectric feed stack is oriented perpendicular to the piezoelectric clamping 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 through the targeted application of an electrical voltage to the piezoelectric stack and the resulting change in the size of the cells or frames. A PIL with a miniaturized and thus compact design is made possible.

The two clamping frame cells or clamping frame frames and the feed cell or the feed frame are preferably arranged in relation to one another so that the feed frame longitudinal axis is aligned in the direction of the movement axis and so that the two clamping frame longitudinal axes are oriented transversely, preferably perpendicularly, to the feed frame longitudinal axis. This enables a maximum feed force to be exerted in the direction of movement by applying a voltage to the piezoelectric feed stack, and 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, which 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 designed in one piece with one another and thus consist of one piece and be manufactured together. Furthermore, the three frames can be formed from the same material. The monolithic structure enables a compact or miniaturized construction. Furthermore, a force amplification and an improved stroke response can be achieved, wherein large carriers for piezoelectric stacks and hinges for connecting these carriers can be dispensed with. There is also no need to manufacture nested frames. 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 components.

The piezoelectric inchworm linear motor preferably comprises aluminum or stainless steel or titanium or is formed from aluminum or stainless steel or titanium.

The piezoelectric inchworm linear motor can be formed from different piezoelectric materials. All components of the piezoelectric inchworm linear motor are preferably formed from the same piezoelectric materials. The piezoelectric stacks and the frames can be made from titanium or from stainless steel or from aluminum or from a PZT5A-3195HD material. The piezoelectric stacks and the frames can also comprise 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 of 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. Plastic polyvinylidene fluoride (PVDF) can also be polarized - similar to piezoelectric ceramics - and can then be used as a material for the piezoelectric stack.

The materials aluminum, 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 piezoelectric inchworm linear motor described above. In addition, these materials are beneficial for energy transfer in the PIL.

The energy transfer takes place in different stages from the electrical input form in the piezoelectric stack to the mechanical output form on the target object to be actuated. The electrical energy supplied 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 operating mode of the piezoelectric stack, the normal mode (longitudinal and transverse direction) or the shear mode.

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

The electrical energy converted into mechanical energy by the piezoelectric stack can be reduced due to a loss of mechanical preload either by a housing mechanism or by mechanical stress that is required for the mechanical contact. The mechanism can also be some kind of mechanical amplifier. However, the gain value should be clearly comparable to the case of a very soft mechanism that does not provide force amplification.

The final stage of energy transfer is when the resulting energy is transferred to the target object after the mechanical loss of prestress. This resulting energy is observed on the target object as a displacement and force actuation. The coefficient of displacement of the piezoelectric stacks is generally larger in the shear mode than in the normal mode. The material PZT5A-3195HD, for example, 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 the operation of the piezoelectric stacks in the shear mode leads to a higher displacement behavior than in the normal mode. However, the greater the deflection reaction, the lower the associated force reaction. Knowing that the electromechanical coupling factor in normal mode is generally greater than that in shear mode, then more mechanical energy can be converted in normal mode and then more energy can be used for force actuation than for displacement. This force actuation can either take place directly on the target object or through mechanical friction. However, the latter leads to further energy losses and to a further low efficiency of the reaction.

The first piezoelectric clamping stack and the second piezoelectric clamping stack preferably 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 of about 3 mm, and / or the feed stack has a height of about 1 mm to 4 mm, preferably of about 2 mm or of about 7 mm to 12 mm, preferably of 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-shaped 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 above-described dimensions of the piezoelectric stacks and the corresponding frames enable a PIL with a compact and thus miniaturized design with high power transmission to the target object and an improved stroke response at the same time. With the embodiments described above, a miniaturized piezoelectric inchworm linear motor (PIL) with high efficiency and large actuating 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 axis of movement. 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. Application of power actuation by means of 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, wherein

• 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 a side view of the inchworm piezoelectric linear motor from FIG 1A shows in which the piezoelectric stacks are inserted into the clamping frames and feed frames, respectively,
• 2A a side view of a second embodiment of a piezoelectric inchworm linear motor with two oval-shaped Shows clamping frame and a feed frame with a folded structure,
• 2 B a side view of the inchworm piezoelectric linear motor from FIG 2A shows in which the piezoelectric stacks are inserted into the clamping frame and the feed frame, respectively,
• 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 a side view of the inchworm piezoelectric linear motor from FIG 3A shows in which the piezoelectric stacks are inserted into the clamping frame and the feed frame, respectively,
• 4th a side view of the inchworm piezoelectric linear motor from FIG 3A shows in relation to a target object,
• 5A and 5B the change in shape of the piezoelectric inchworm linear motor from the 3B show when a voltage is applied to the first piezoelectric clamp stack in the first clamp frame and there is no mechanical load,
• 6A and 6B the change in shape 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 change in shape of the piezoelectric inchworm linear motor from the 3B FIG. 13 shows when a voltage is applied to the first piezoelectric clamp stack in the first clamp frame and a mechanical load with a force of 50 N is present, and FIG
• 8A and 8B the change in shape 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 a mechanical load with a force of 50 N is present.

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

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

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

The first clamp frame 7th has a first interior 25th with a first piezoelectric clamp stack 27 on, wherein the first piezoelectric clamp stack 27 such in the first interior 25th is arranged or can be arranged so that the first piezoelectric clamping stack 27 at least partially with the first clamping frame 7th is in contact. The second clamp frame 11 has a second interior 29 with a second piezoelectric clamp stack 31 on, the second piezoelectric clamp stack 31 such in the second interior space 29 is arranged or can be arranged so that the second piezoelectric clamping stack 31 at least partially with the second clamping frame 11 is in contact.

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

The interiors 25th , 29 , 33 of the three cells 2 , 3 , 5 are partially from the frame 7th , 11 , 15th is enclosed. So each has the three frames 7th , 11 , 15th a first open page 37 and a second open side 39 on, which is opposite to the plane of the clamping frame longitudinal axes 9 , 13th or the longitudinal axis of the feed frame 17th are arranged.

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

The piezoelectric feed stack 35 is at least indirectly with the two terminal cells 2 , 3 is in contact and connects or couples the two terminal cells 2 , 3 together. In the in the 1A and 1B The embodiment shown is the piezoelectric feed stack 35 in the feed frame 15th arranged, the feed frame 15th with the two clamping frames 7th and 11 connected is. The two terminal cells 2 , 3 and the feed cell 5 are in series and along the axis of motion 19th of the piezoelectric inchworm linear motor 1 arranged. Any piezoelectric clamp stack 27 , 31 is like that in the terminal cell 2 , 3 arranged so that a change in an electrical voltage on the piezoelectric clamp stack 27 , 31 a change in expansion of the piezoelectric clamp stack 27 , 31 parallel to the axis of movement 19th and / or in the direction of the axis of movement 19th causes. This experiences the clamping frame 7th , 11 a change in size substantially perpendicular to the direction of movement, and the clamping frame 7th , 11 arrives with a guide unit 47 (not in the 1A and! b) engaged or is of the guide unit 47 solved.

The first clamp frame 7th has a first coupling wall 49 with a first engagement unit 51 on and the second clamping frame 11 has a second coupling wall 53 with a second engagement unit 55 on, the engagement units 51 , 55 for engagement with the guide unit 47 (not in 1A and 1B shown) are designed. Opposite to the coupling walls 49 , 53 in the direction of the longitudinal axis of the clamping frame 9 , 13th seen show the clamping frames 7th , 11 each have a further coupling wall, the further coupling walls corresponding to the coupling walls 49 , 53 are configured and each have a further engagement unit, the further engagement units corresponding to the engagement units 51 , 55 are designed. The clamp frames 7th , 11 thus have a symmetrical structure.

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

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

Instead of engaging grooves, the feed frame 15th Ledges 61 have, wherein the projections 61 preferably in the plane of the longitudinal axis of the feed frame 17th extend and extend from curved outer walls of the feed frame 15th extend away in opposite directions. The two protrusions 61 serve as connecting elements to connect the feed frame 15th with the two clamping frames 7th , 11 . The feed frame 15th thus has a symmetrical structure.

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

2A and 2 B show a second embodiment of a piezoelectric inchworm linear motor according to the invention 1' . The second embodiment of the piezoelectric inchworm linear motor 1' differs from the first embodiment of the inchworm piezoelectric linear motor 1 in the 1A and 1B through the design of the feed cell 5 ' and their connection to the two terminal cells 2 , 3 . In addition, the piezoelectric feed stack 35 ' of the second embodiment by 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 ' exhibit a folded structure 63 on. The opposite, flat outer walls 41 ' , 43 ' are each characterized by a deformed or bent rod 65 formed, the deformed or bent rod 65 is bent back and forth in one plane.

The opposite, flat outer walls 41 ' , 43 ' each have a rectangularly folded structure or fold 67 on. The curved rod 65 is between a first outer wall side 69 and a second outer wall side 71 folded back and forth, the folding 67 has a substantially rectangular cross-sectional area. The folding 67 is with the two terminal frames 7th , 11 tied together. The one inside the feed frame 5 ' arranged feed stacks 35 ' is directly with the two clamping frames 7th , 11 in contact.

The design of the feed frame 5 ' , in which the opposite, flat outer walls 41 ' , 43 ' one fold each 67 have, made possible by applying a voltage to the piezoelectric feed stack 35 inside the feed frame 5 ' a stroke resolution in the nanometer range (nano stroke resolution).

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

The two opposite, flat outer walls 41 " , 43 " exhibit a multitude 69 of folds. The multitude 69 of folds includes fourteen folds. The flat outer wall 41 " includes seven folds, and the flat outer wall 43 " includes seven folds. So there are a total of fourteen folds. A first of the multitude 69 at folds is with the first clamping frame 7th tied together. The second of the multitude 69 at folds is with the second clamping frame 11 tied together.

The design of the feed frame 5 " , in which the opposite, flat outer walls 41 " , 43 " a multitude 69 of folds, in particular fourteen folds, enables a stroke resolution in the micrometer range (micro-H u b resolution).

4th Figure 12 shows an exemplary alignment of the second embodiment of an inchworm piezoelectric linear motor 1" from the 3A and 3B with the target object or drive object 45 and the management unit 47 . The management 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 extends. One of the two ends has an opening 77 through which the drive object 45 extends therethrough so that the drive object extends 45 partially inside the guide unit 47 and partially extends outside. At the second end 75 can be a spring element or tension element 79 be provided. The piezoelectric inchworm linear motor 1" is in such a way in the guide unit or in the guide housing 47 arranged so that the piezoelectric inchworm linear motor 1" along the longitudinal axis of the guide unit 71 extends and the axis of movement 19th in the direction of the longitudinal axis of the guide unit 71 runs. A flat outer wall 41 of the first clamping frame 7th depends on the target object 45 on and can drive this. The management units 47 of the two clamping frames 7th , 11 can with the guide unit 47 intervene laterally. By sequentially changing an electrical voltage on the piezoelectric terminal stacks 27 , 31 and on the feed pile 35 " get the clamping frames 7th , 11 alternating with the guide unit 47 engage and disengage from this, leaving the stack 27 , 31 , 35 " relative to the guide unit 47 perform a linear movement.

In all of the above-described embodiments of the piezoelectric inchworm linear motor 1 , 1' , 1" the feed cell extends 5 , 5 ' , 5 " essentially in the direction of the axis of movement 19th of the piezoelectric inchworm linear motor 1 , 1' , 1" and the two terminal cells 2 , 3 extend essentially in a transverse direction, namely at an angle of 90 degrees to the axis of movement 19th of the piezoelectric inchworm linear motor 1 , 1' , 1" . The two clamping frames 7th , 11 each form with the feed frame 15th , 15 ' , 15 " a monolithic structure. The piezoelectric inchworm linear motor 1 , 1' , 1" can comprise aluminum or stainless steel or titanium or be formed from 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" (please refer 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 pile 35 , 35 ' the first and second embodiments of the inchworm piezoelectric linear motor 1 , 1' (please refer 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 pile 35 " the third embodiment of the inchworm piezoelectric linear motor 1" (please refer 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. The ones in the 5A until 8B The Z direction shown corresponds to the direction along the axis of movement 19th , and the Y-direction shown corresponds to the direction which is perpendicular to the movement axis 19th is aligned. All in the 5A until 8B The simulations shown are based on the fact that on the first piezoelectric clamp stack 27 an electrical voltage is applied and show how a first area 81 and a second area 83 of the first clamping frame 7th experience a displacement in the Z-direction and in the Y-direction.

5A and 5B each show the change in shape of the piezoelectric inchworm linear motor 1" in the Y-direction and Z-direction under the following conditions: the second terminal cell 3 is fixed, a voltage of 75 V is on the first piezoelectric clamp stack 27 in the first clamp frame 7th applied and there is no mechanical load. No mechanical load means that one end of the drive object 41 that is in the 4th than from the management unit 47 is prominently shown, a free end 42 on which there is no load. In this case, the full power of the PIL is effective 1" on the drive object 45 .

In the in the 5A and 5B As shown in the FEM simulation, the piezoelectric inchworm linear motor expanded 1" below 75 V operating voltage in the Z direction in the first area 81 by a maximum of 2.1 µm. The first clamp frame 7th 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 thus experiences a shift in the Z direction, whereas the second area 83 experiences a shift in the Y direction. This lateral displacement or displacement is sufficient to drive the piezoelectric inchworm linear motor 1" to be released from the clamped state.

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

In the in the 6A and 6B As shown in the FEM simulation, the piezoelectric inchworm linear motor expanded 1" below 75 V operating voltage in the Z direction in the first area 81 by a maximum of 10.1 µm. The first clamp frame 7th 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 experiences a shift in the Z direction, whereas the second area 83 experiences a shift in the Y direction. This lateral displacement or displacement is sufficient to drive the piezoelectric inchworm linear motor 1" to be released from the clamped state.

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

In the in the 7A and 7B As shown in the FEM simulation, the piezoelectric inchworm linear motor expanded 1" under 75 V operating voltage and 50 N mechanical load in the Z direction in the first area 81 by a maximum of 1.14 µm. The first clamp frame 7th 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 shift in the Z direction, whereas the second area 83 experiences a shift in the Y direction. This lateral displacement or displacement is sufficient to drive the piezoelectric inchworm linear motor 1" to be released from the clamped state.

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

In the in the 8A and 8B As shown in the FEM simulation, the piezoelectric inchworm linear motor expanded 1" under 75 V operating voltage and 50 N mechanical load in the Z direction in the first area 81 by a maximum of 9.14 µm. The first clamp frame 7th 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 shift in the Z direction, whereas the second area 83 experiences a shift in the Y direction. This lateral displacement is sufficient to drive the inchworm piezoelectric linear motor 1" to be released from the clamped state.

The above-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 axis of movement 19th is used directly without the need for additional structures with hinges. Thus, power losses due to the Avoid occurrence of mechanical friction. 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 according to the invention 1 , 1' , 1" has a high level of reliability in that fragile elements such as hinges or pivot points are excluded from the construction by the use of clamping frames. In addition, the inventive piezoelectric inchworm linear motor 1 , 1' , 1" has a high electromechanical energy efficiency and is simple both in construction and in implementation.

List of reference symbols

1, 1 ', 1 "

piezoelectric inchworm linear motor

2

first terminal cell

3

second terminal cell

5, 5 ', 5 "

Feed cell

7th

first clamp frame

9

first longitudinal axis of the clamping frame

11

second clamping frame

13th

second longitudinal axis of the clamping frame

15, 15 ', 15 "

Feed frame

17th

Feed frame longitudinal axis

19th

Axis of motion

21

first end of the piezoelectric inchworm linear motor

23

second end of the inchworm piezoelectric linear motor

25th

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 frame

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 engagement unit

53

second coupling wall

55

second engagement unit

57

first lateral contact surface

58

inner contact surface

59

second lateral contact surface

61

Ledges

63

folded structure

65

deformed or bent rod

67

rectangular folded structure or folding

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

QUOTES INCLUDED IN THE DESCRIPTION

This list of the documents listed by the applicant was generated automatically and is included solely for the better information of the reader. The list is not part of the German patent or utility model application. The DPMA assumes no liability for any errors or omissions.

Patent literature cited

• US 2014/0333180 A1 [0008]
• US 2012/0119620 A1 [0008]

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 arranged within the first clamp frame (7) in such a way that the first piezoelectric clamp stack (27) is at least partially in contact with the first clamping frame (7), a second clamp cell (3) with a second clamp frame (11) and a second piezoelectric clamp stack (31), the second piezoelectric clamp stack (31) being 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 clamping 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 terminal cells (2, 3) and connects or couples the two terminal cells (2, 3) to one another, wherein the two clamping cells (2, 3) and the feed cell (5, 5 ', 5 ") are arranged in series and along a movement axis (19) of the piezoelectric inchworm linear motor (1, 1', 1"), wherein each piezoelectric terminal stack (27, 31) is arranged in the terminal cell (2, 3) in such a way so 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) experiences a change in size essentially perpendicular to the direction of movement (19), and so that the clamping frame (7, 11) comes into engagement with a guide unit (47) or the engagement is released. 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 engagement unit (51), wherein the second clamping frame (11) has a second coupling wall (53) with a second engagement unit (55), and wherein the engagement units ( 51, 55) are designed for engagement with the guide unit (47). Piezoelectric inchworm linear motor (1, 1 ', 1 ") according to Claim 2 , wherein the change in expansion of the piezoelectric clamping stacks (27, 31) or the change in size of the clamping frames (7, 11) bring the engagement units (51, 55) into frictional engagement with the guide unit (47). Piezoelectric inchworm linear motor (1, 1 ', 1 ") according to one of the preceding claims, wherein the first terminal cell (2) and the second terminal 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 a sequential change of 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 come into engagement with and detach from the guide unit (47), so that the piezoelectric inchworm linear motor (1, 1 ', 1 ") executes 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 (9) 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 (9, 11). Piezoelectric inchworm linear motor (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") extends essentially in the direction of the movement axis (19) of the piezoelectric inchworm linear motor (1, 1 ', 1 "), the two terminal cells (2, 3) extending essentially in a direction transverse to the axis of movement (19) of the piezoelectric inchworm linear motor (1, 1 ', 1"), and / or wherein the piezoelectric clamping stacks ( 27, 31) and the piezoelectric feed stack (35, 35 ', 35 ") extend parallel to one another and / or parallel to the axis of movement or wherein the piezoelectric clamping stacks (27, 31) extend parallel to one another and / or parallel to the movement axis and the piezoelectric feed stack (35, 35 ', 35 ") is aligned perpendicular to the piezoelectric clamping stacks (27, 31) and / or to the axis of movement. Piezoelectric inchworm linear motor (1, 1 ', 1 ") according to one of the Claims 7 until 10 , 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 approximately 2 mm or approximately 9 mm, a width of approximately 3 mm and a length of approximately 3 mm.

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