Classifications

• • H—ELECTRICITY
  • H02—GENERATION; CONVERSION OR DISTRIBUTION OF ELECTRIC POWER
  • H02N—ELECTRIC MACHINES NOT OTHERWISE PROVIDED FOR
  • H02N2/00—Electric machines in general using piezoelectric effect, electrostriction or magnetostriction
  • H02N2/0005—Electric machines in general using piezoelectric effect, electrostriction or magnetostriction producing non-specific motion; Details common to machines covered by H02N2/02 - H02N2/16
  • H02N2/009—Thermal details, e.g. cooling means
• • H—ELECTRICITY
  • H02—GENERATION; CONVERSION OR DISTRIBUTION OF ELECTRIC POWER
  • H02N—ELECTRIC MACHINES NOT OTHERWISE PROVIDED FOR
  • H02N2/00—Electric machines in general using piezoelectric effect, electrostriction or magnetostriction
  • H02N2/02—Electric machines in general using piezoelectric effect, electrostriction or magnetostriction producing linear motion, e.g. actuators; Linear positioners ; Linear motors
  • H02N2/021—Electric machines in general using piezoelectric effect, electrostriction or magnetostriction producing linear motion, e.g. actuators; Linear positioners ; Linear motors using intermittent driving, e.g. step motors, piezoleg motors
  • H02N2/025—Inertial sliding motors
• • H—ELECTRICITY
  • H02—GENERATION; CONVERSION OR DISTRIBUTION OF ELECTRIC POWER
  • H02N—ELECTRIC MACHINES NOT OTHERWISE PROVIDED FOR
  • H02N2/00—Electric machines in general using piezoelectric effect, electrostriction or magnetostriction
  • H02N2/02—Electric machines in general using piezoelectric effect, electrostriction or magnetostriction producing linear motion, e.g. actuators; Linear positioners ; Linear motors
  • H02N2/04—Constructional details

Definitions

• This blockage can be resolved by heating the piezoelectric actuators to a temperature above 30 K in order to desorb the gas.
• an actuator comprising: o a transducer mounted on one of the blocks and comprising a piezoelectric body and a wiper in contact with the piezoelectric body and covering the piezoelectric body, o a pad mounted on the other block and movable by sticky sliding on the wiper when an electrical signal is applied to the piezoelectric body, in order to move the blocks relative to each other along an X axis, and
• the actuator can thus be heated directly, without it being necessary to heat the entire instrument in which the positioner can be installed.
• the gases released by the local heating of the actuator can be adsorbed by cooler walls of other components of the positioner.
• the pad and the piezoelectric body thus freed from the gas(es), can perform a sticky sliding motion relative to each other, reducing the risk of jamming.
• the actuator heats up quickly, and the energy required to heat the actuator is low.
• direct heating of the piezoelectric body increases the piezoelectric coefficient, which increases the power of the positioner.
• the invention limits the thermal expansion of the components of the positioner by concentrating the heat produced by the heating member on the actuator. This avoids the effects resulting from this thermal expansion which are complex and difficult to understand when designing the positioner.
• the “sticky sliding” motion of the pad on the collector is induced by a deformation of the piezoelectric body when an electrical voltage is applied to the transducer.
• the deformation of the piezoelectric body causes the block containing the pad to move relative to the block containing the collector due to the friction between the pad and the collector.
• the sliding phase during which the voltage is rapidly decreased, the piezoelectric body abruptly returns to its initial position without the two blocks moving, due to the sliding of the pad on the collector.
• a repetition of cycles each comprising a sticky phase and a sliding phase allows the continuous movement of one block relative to the other.
• the heating member is fixed, more preferably glued, in particular with a thermal glue, on the actuator and/or on one of the blocks and/or is in the form of a layer covering the actuator and/or one of the blocks.
• the layer can extend over a surface area of between 5 mm 2 and 50 mm 2 .
• the thickness of the layer may be between 0.5 and 5 mm.
• the layer may comprise a resistive wire, for example shaped like a serpentine, immersed in a binder, for example a thermal glue.
• the opposite ends of the wire may be connected to electrical connectors, for an electrical supply by means of an electric current generator.
• the electrical connectors are for example arranged on an external face of one of the blocks.
• the heating member may be remote from the actuator.
• the distance between the heating member and the actuator may be between 0.01 mm and 1 mm, preferably between 0.01 mm and 0.5 mm, more preferably between 0.01 mm and 0.1 mm.
• the pad may be sandwiched between the heater and the transducer.
• the transducer may be sandwiched between the heater and the pad.
• the actuator is preferably configured to translate the blocks relative to each other along the X axis.
• the actuator is compressed between the blocks. In this way, in the absence of an electrical signal powering the actuator, it is ensured that the blocks remain stationary relative to each other.
• the block on which the transducer is mounted may include a housing in which the transducer, in particular the piezoelectric body, is received.
• the housing and the transducer are preferably of complementary shape to ensure optimum retention of the transducer on the block.
• the positioner comprises at least one group of actuators comprising two, preferably three actuators distributed opposite each other.
• this avoids unwanted movements of one block relative to the other along one or more axes transverse to the X axis.
• the actuators of the actuator group are distributed, preferably regularly around the X axis.
• each actuator of the actuator group is heated by a corresponding heating member.
• the positioner comprises two groups of actuators arranged at a distance from each other, each group of actuators preferably comprising three actuators facing each other.
• One of the blocks may comprise a support, the actuators being in contact with the support.
• the actuators are distributed around the support.
• the actuators may be arranged between the support and the other block, the pad of each actuator preferably being arranged between the support and the wiper of said actuator.
• the heating member of each actuator may be arranged between the support and the pad of the actuator that it is intended to heat.
• the support is cylindrical of revolution or, preferably, prismatic, in particular with a triangular base, for example equilateral.
• the friction member and/or the pad may be made of a material chosen from sapphire, alumina, bronze, graphite, adamantine carbon and their mixtures.
• the wiper is made of sapphire and/or the pad is made of alumina.
• the actuators may be distributed on the support facing each other.
• the number of actuators may be greater than three, for example a multiple of three.
• the actuators may each be arranged between the support and the other block.
• the pad of each actuator may be arranged between the support and the wiper of said actuator.
• Either block may have several parts that move relative to each other, or parts that are fixed to each other. Alternatively, it may be monolithic.
• each of the blocks is metallic, for example stainless steel for non-magnetic applications or titanium, brass, aluminum for applications in magnetic fields.
• the different constituent parts of each block can be made of different alloys.
• At least one of the blocks comprises a base part, a support part and a spring, transverse to the X axis, deformed, such that the actuator is compressed between the blocks.
• the compressive force exerted on the actuator is oriented perpendicular to the X axis.
• the spring is made of a metallic material, preferably an alloy, in particular a bronze alloy, for example CuSn6, or a beryllium bronze alloy.
• the material of the spring can be adapted to the experimental conditions.
• the spring can be made of stainless steel for non-magnetic applications or of titanium, brass, copper, for applications in a magnetic field.
• the spring is preferably annular, ring-shaped, or helical, in order to easily accommodate thermal deformations that develop in the components of the positioner during large temperature variations, such as those that may occur when placing a sample on the positioner at room temperature and studying it at a temperature below 20 K.
• the device comprises several, for example four, springs to ensure uniform compression.
• the springs have an identical rigidity, or are even identical.
• the spring elastically connects the support piece to the base piece and is preferably helical.
• the spring is fixed to the support piece and to the base piece.
• the spring exerts a restoring force on the support piece and base piece, which is oriented perpendicular to the X axis.
• the support piece may have a “U” or “L” shaped cross section.
• the support can be arranged between the base piece and the support piece.
• At least one of the actuators can be arranged between the support and the base part and at least one other of the actuators may be arranged between the support and the support piece.
• at least one of the actuators of a group of actuators may be arranged between the support and the base piece and at least one other of the actuators of said group may be arranged between the support and the support piece.
• the actuator disposed between the support and the base part can be compressed by the support and the base part and the other actuator disposed between the support and the support part can be compressed by the support and the support part.
• the heating member may be arranged between the base part and the piezoelectric body. It may be in contact with the base part and the piezoelectric body.
• the spring surrounds the base part and the support part, and preferably is in contact with the base part and the support part, and preferably is annular or in the form of a ring portion.
• the support piece preferably oriented radially around the X axis, in order to maintain the actuator(s) in compression between the support and the support piece.
• the block comprising the support piece and the base piece preferably comprises a hollow tubular portion, the wall of the hollow tubular portion comprising the support piece, the support and the actuator(s) being housed in an interior space delimited by the tubular portion.
• the block comprising the support may further comprise a plate, for example to carry a sample to be studied, and a bracket rigidly fixed to the plate and to the support.
• the support piece may be at least partially arranged between the support and the plate.
• the support piece may have a through opening into which the bracket is engaged.
• the support piece can be mounted freely on the base piece, Le. it can be moved along at least one, or even two, or even three perpendicular axes.
• the movable part is not rigidly fixed on the support piece.
• the positioner preferably comprises an axial spring, preferably helical, exerting a restoring force between the base piece and the support piece, and which is oriented parallel to the X axis.
• the support piece and the base piece may each be hollowed out so as to together define a housing, the axial spring being disposed in the housing.
• the axial spring may be disposed between the support and the plate.
• the axial spring is helical.
• the support piece may be rigidly fixed to the base piece and may comprise a flexible portion extended by a rigid portion on which the transverse spring(s) are fixed, the flexible portion being elastically deformable during the sticky sliding of the pad on the wiper and elastically recalling the rigid portion, in particular against the base piece, following the sticky sliding of the pad against the wiper.
• a "flexible portion” means a portion with lower bending and/or shear stiffness than the rigid portion.
• a flexible portion is, however, sufficiently rigid not to deform under its own weight.
• the flexible portion preferably has an area, preferably at least twice, or even at least ten times, smaller than the area of the rigid portion.
• the support piece may have the shape of a plate and the flexible portion may have a recess extending in a median plane of the plate along an axis perpendicular to the Y axis.
• the recess has, for example, the shape of a dumbbell.
• the invention also relates to a positioning device, preferably multi-axis, comprising first and second positioners according to the invention, one of the blocks of the second positioner comprising, or even consisting of, the first positioner.
• the blocks of the first positioner are movable relative to each other by sticky sliding along a first axis and the blocks of the second positioner are movable relative to each other along a second axis that is non-parallel, preferably perpendicular, to the first axis.
• the positioning device is multi-axis and allows a sample to be moved along two dimensions of space.
• the positioning device may comprise a third positioner according to the invention, one of the blocks of the third positioner comprising, or even consisting of, the second positioner.
• the blocks of the third positioner are movable relative to each other by sticky sliding along a third axis that is non-parallel, preferably perpendicular, to each of the first and second axes.
• the positioning device multi-axis positioning allows a sample to be moved in three spatial dimensions.
• the second positioner block that is movable relative to the first positioner defines a housing in which the first positioner is received.
• it has a generally tubular and hollow shape and defines an interior space in which at least one of the blocks of the first positioner is entirely received.
• the third positioner block that is movable relative to the second positioner defines a housing in which the second positioner is received.
• it has a generally tubular and hollow shape and defines an interior space in which at least one of the second positioner blocks is entirely received.
• the first, second and third positioners can be arranged in the manner of a Russian doll within the positioning device.
• the invention also relates to a method for heating the actuator of a positioner according to the invention or of a positioning device according to the invention.
• the temperature of the actuator prior to heating, is less than 10 K, or even less than 5 K.
• the method may include supplying electrical power to the actuator to heat the latter, in particular by the Joule effect.
• the heating induces an increase in the actuator temperature of less than 50 K.
• the positioner can be arranged in a near-field microscope, for example a scanning tunneling microscope or an atomic force microscope.
• the method comprises, after heating, the movement of a sample carried by one of the two blocks, by electrically supplying the actuator.
• the temperature of the actuator is between 260 K and 273 K, the heating being carried out to defrost the contact faces of the pad and the friction member.
• the invention finally relates to a system comprising:
• a microscope in particular a near-field microscope, comprising an enclosure
• a positioner according to the invention or a positioning device according to the invention arranged in the enclosure - optionally, a cooling module to cool the enclosure to a temperature below 30 K, in particular around 4 K.
• FIG. 1 is a perspective view of a positioner according to a first embodiment of the invention
• FIG. 2 is a side view of the positioner according to the first embodiment
• FIG. 3], FIG. 4] and [Fig. 5] are sectional views of the positioner according to the first embodiment according to planes (AA), (BB) and (CC) respectively,
• FIG. 6 [Fig. 7] and [Fig. 8] are perspective views of different parts of the positioner according to the first embodiment
• FIG. 9 is an enlarged view of two specific arrangements of the heating member of the positioner according to the first embodiment
• FIG. 10 is a perspective view of a positioner according to a second embodiment of the invention.
• FIG. 11 is a side view of the positioner according to the second embodiment
• FIG. 12] and FIG. 13] are sectional views along planes (DD) and (EE) respectively.
• FIG. 14 is a longitudinal sectional view of a positioner according to a third embodiment of the invention.
• FIG. 15 is a longitudinal sectional view of a multi-axis positioning device according to the invention integrating the positioner according to the third embodiment of the invention.
• Figures 1 to 10 illustrate a first example of a positioner 1 according to the invention.
• the positioner 1 comprises two blocks 2, 3, six actuators 4 and heating members 6 of the respective actuators 4. This number of actuators 4 and heating members 6 is however not limiting.
• the actuators 4 and the heating elements 6 are arranged between the blocks 2,3.
• Blocks 2,3, which will subsequently be referred to as the first 2 and second 3 blocks respectively, can be moved relative to each other and are movable along an X axis.
• the first block 2 comprises a base piece 5 and a support piece 7 which surmounts the base piece 5, lower pins 8, upper pins 9 and transverse springs 10 on the X axis and helical springs which, in the example presented, extend vertically.
• the first block 2 may have a length measured along the X axis, between 15 and 50 mm, a width between 15 and 25 mm, and a height, measured along the vertical direction, between 15 and 25 mm.
• the side wall 51 comprises a positioning notch 52 of prismatic shape, for example with a substantially triangular base, which opens onto the inner face 54 of the side wall 51.
• the recess 52 may be through, as can be observed for example in FIG. 10.
• a recess 53 of circular section is also provided in the side wall 51 and opens onto the inner face 54.
• the base part 5 comprises a relief structure 55 which extends vertically from the lower wall 50.
• Each of the support pieces 5 are portions of a cylinder of revolution with a shape complementary to each of the recesses made in the wall 83.
• the positioning device 90 comprises first 1, second 91 and third 100 positioners which are all according to the invention, the first positioner 1 being that illustrated in FIG. 14. It comprises blocks 2, 3 movable relative to each other along a vertical X axis.
• the positioning device 90 is thus multi-axis and allows movement of a sample placed on the stage along one or more of the X, Y and Z axes.

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• General Electrical Machinery Utilizing Piezoelectricity, Electrostriction Or Magnetostriction (AREA)

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• 2023
  • 2023-04-04 EP EP23745234.7A patent/EP4690452A1/de active Pending
  • 2023-04-04 WO PCT/FR2023/050484 patent/WO2024209135A1/fr not_active Ceased

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