JP2007505599A - Ultrasonic motor for lead screw - Google Patents

Abstract

An apparatus for driving a threaded shaft assembly that contains a threaded shaft with an axis of rotation and, engaged therewith, a threaded nut. Subjecting the threaded nut to ultrasonic vibrations causes the threaded shaft to simultaneously rotate and translate in the axial direction. The threaded shaft is connected to a load that applies an axial force to the threaded shaft. ® KIPO & WIPO 2007

Description

  The present invention relates to a small ultrasonic linear motor assembly provided with a threaded shaft and a nut screwed into the shaft.

  A transducer using piezoelectric electrostriction technology, electrostatic technology, or electromagnetic technology is extremely useful for accurate positioning on the nanometer scale. In the case of a piezoelectric device, a ceramic capacitor that deforms during charging and discharging is formed to produce a force transducer and a position actuator. When used as a position actuator, the deformation of the piezoelectric ceramic is approximately proportional to the applied voltage. Piezoelectric actuators are limited to a range of approximately 0.1% of the ceramic length, which corresponds to a typical stroke length of 10 micrometers. The stiffness and nanometer precision of a piezoelectric actuator is extremely useful, but many applications require a greater number of strokes.

  A number of piezoelectric motors have been designed and developed that correct small ceramic deformations and produce longer strokes.

  US Pat. No. 3,902,084 describes a PZT stepping motor, the entire disclosure of which is hereby incorporated by reference. This motor utilizes a sequence of clamp extension clamp retraction operations to group a number of short PZT actuator cycles. This stepping linear actuator operates from a direct current to a frequency of up to several kilohertz and generates a large noise and vibration. The posture is not maintained when the power is off. Resolutions better than 1 nanometer are achieved over a stroke of 200 millimeters.

  US Pat. No. 5,410,206 describes a PZT inertial stick-slip motor, the entire disclosure of which is hereby incorporated by reference. The motor described therein rotates a shaft with fine threads using a split nut that forms a jaw that bites both ends of the shaft. The PZT actuator moves the jaw at high speed in the opposite direction with an asymmetrical AC drive signal. The high-speed movement of the jaw overcomes the clamping friction and causes slipping. The low speed movement of the jaws causes the shaft to rotate without causing slip. This stick-slip motor also produces noise and vibration similar to the above stepping motor, but moves 100 times slower and maintains its posture even when the power is turned off. Resolutions better than 50 nanometers are achieved with a stroke greater than 25 millimeters.

  Ultrasonic motors use piezoelectric vibrations to achieve high-speed, high-torque, small and quiet continuous motion.

  One of the earliest ultrasonic piezoelectric motors is disclosed in US Pat. No. 3,176,167. The entire disclosure is hereby incorporated by reference. This motor, which rotates in a single direction, uses a crystal oscillator to move a thin bar and drive the pinwheel for the purpose of driving the clockwork.

  An example of a standing wave ultrasonic motor is disclosed in US Pat. No. 5,453,653, the entire disclosure of which is hereby incorporated by reference. This motor uses a rectangular PZT plate and generates ultrasonic vibration at a contact point preloaded on the movable surface. The electrode pattern on the PZT plate is connected to an AC signal and generates a two-dimensional vibration at the contact with the required amplitude and phase in order to generate a net (true) force on the mating surface. This ultrasonic motor is quiet, moves 100 times faster than a stepping motor, and produces about a third of the force. In general, ultrasonic motors are difficult to stop and start, which is a cause of lack of precision. To achieve sub-micrometer resolution typically requires an encoder with closed loop control.

  A screw-type rod driving device using ultrasonic vibration is described in, for example, US Pat. No. 6,147,435. The entire disclosure is hereby incorporated by reference. In this patent, “a screw rod having a spiral groove formed in the axial direction, a pair of stands that rotatably hold both opposing ends of the screw rod, and the shaft partially surrounding the screw rod. A work rack slidable in a direction, at least one first screw rod rotating device fixed to one side of the work rack and extending from the work rack to the screw rod, and fixed to the other side of the work rack, At least one second screw rod rotating device extending from the rack to the screw rod, wherein the first screw rod rotating device is in contact with the groove portion of the screw rod at a first specific angle; A first spring that urges the first vibrator toward the groove of the screw rod with a specific pressure, A first piezoelectric actuator that vibrates the first vibrator to rotate the screw rod in a first rotation direction, and the second screw rod rotating device includes a groove portion of the screw rod and a first specific angle. A second vibrator that makes contact at a second specific angle opposite to the first vibrator, a second spring that urges the second vibrator toward the groove of the screw rod with a specific pressure, and the first activation by electrical activation. A screw rod drive mechanism by ultrasonic vibration having a second piezoelectric actuator that vibrates two vibrators and rotates the screw rod in a second direction is described and claimed.

  In the apparatus of the above-mentioned US Pat. No. 6,147,435, both the “first screw rod rotating device” and the “second screw rod rotating device” are indispensable. In FIG. 3 of the patent, these are the elements 16a ′ and 16d ′ (which constitute the first screw rod rotating device), the elements 16b ′ and 16c ′ (these constitute the second screw rod rotating device). ). When the element 16a ′ and the element 16d ′ are activated by ultrasonic vibration, the screw rod 2 rotates in one direction, and when the element 16b ′ and the element 16c ′ are activated by ultrasonic vibration, the screw rod 2 is Rotate in the opposite direction.

  Elements 16a 'and 16d' and elements 16b 'and 16c' are not activated simultaneously. It will be a waste of energy to activate at the same time, and the screw rod 2 remains stationary.

  However, even if the elements 16a ′ and 16d ′ and the elements 16b ′ and 16c ′ are not activated at the same time, energy is wasted. This is because the pair of elements that are not activated remain in contact with the screw of the screw rod 2 and drag friction occurs.

  This drag friction is a problem with the device of US Pat. No. 6,147,435. In order to solve this problem to some extent, claim 2 of the patent states, “When one of the first and second piezoelectric actuators is electrically activated, a small amount of current is applied to the other piezoelectric actuator. Although it is proposed to “apply”, the device of the patent is nevertheless highly efficient.

  The object of the present invention is substantially higher performance than the apparatus described in US Pat. No. 6,147,435, which is higher power than is normally achievable with prior art ultrasonic motors of comparable magnitude. Therefore, it is to provide a precise threaded shaft drive mechanism by high-speed ultrasonic vibration.

  In accordance with the present invention, an apparatus is provided for driving a threaded shaft assembly having a threaded shaft and a nut threadably engaged therewith. The assembly of the present invention includes means for applying ultrasonic vibration to the nut, rotating the shaft and simultaneously moving in the axial direction, and means for applying an axial force to the shaft.

  In one embodiment of the present invention, a small ultrasonic linear motor rotates a lead screw to cause a linear motion. The cylinder supports the screw nut at the resonance frequency of the first bending mode in the ultrasonic region. The cylinder and nut are excited by the transducer at the resonance frequency, which causes the nut to orbit at the end of the cylinder. The transducer can be piezoelectric, electrostrictive, electrostatic, electromagnetic, or any other device that causes resonant vibration. At least two transducers are required to excite the right-angle bending mode cylinder with a phase shift of ± 900 degrees and simultaneously cause circular orbital motion. The nut is fitted with a tightly threaded shaft. A resilient axial load is applied to the shaft via a low friction coupling. The nut orbits at its resonant frequency and the inertia of the shaft keeps it in the center. The orbital motion (circular motion) of the nut generates torque, rotates the shaft, and causes linear motion. The converter requires at least two AC drive signals. The driving frequency must excite the mechanical frequency and control the phase so that the nut orbits in a circular path. Adjustment of the amplitude and duration of the drive signal controls the speed. The phase shift of the drive signal may be either positive or negative, which reverses the orbiting direction of the nut and the direction of rotation and movement of the shaft. This and other embodiments are described in more detail below.

  Without being bound to a particular theory, the principle of operation of an ultrasonic linear actuator related to the present invention is that the cylindrical tube is excited with a first bending resonance, which causes one or both ends of the tube to be The present inventor believes that the orbit is performed without rotating around. In this example, a nut that orbits around a threaded tube and produces a tangential component that rotates the shaft is housed in one end of the tube. The frictional resistance between the screws is beneficial because it drives the screws directly. This is a significant difference from the conventional lead screw drive mode. The frictional resistance of the screw in the conventional driving mode is parasitic, and windup, play, and response delay occur. A further advantage of the helical screw used in the present invention is that it can directly convert rotational motion into parallel motion with great mechanical benefit, which can amplify axial force and reduce linear velocity, As a result, accuracy can be increased.

  In embodiments of the present invention, it is preferred to use a transducer to excite the first bending mode. Usable transducers include piezoelectric materials including plates and stacks, magnetostrictive materials, electrostatic materials and the like. What is illustrated here does not include all converters that can be used in the present invention. Any material or mechanism that can cause orbiting at one or both ends of the tube by exciting the first bending resonance in a cylindrical tube or similarly shaped block can be used in the present invention. In the specific example described here, a piezoelectric material is used, but the present invention can also be embodied using another transducer material as described above.

Hereinafter, the present invention will be described in detail with reference to the accompanying drawings.
1-6 illustrate an ultrasonic linear motor 10 in a preferred embodiment of the present invention. In the example shown, four rectangular piezoelectric plates are used to generate ultrasonic vibrations. Although not shown, ultrasonic vibrations can be generated using other means.

  In this specification, ultrasound refers to an operating frequency exceeding 20,000 hertz. One example is an operating frequency of at least about 25,000 hertz, another example is frequency, and another example is an operating frequency of at least about 50,000 hertz. In yet another example, there is ultrasound with an operating frequency of at least about 100,000 hertz.

  The linear motor referred to in this specification refers to an actuator that generates a substantially linear motion by generating force or causing substitution. Regarding ultrasonic linear motors, see US Pat. Nos. 5,982,075, 5,134,334, 5,036,245, 4,857,791, and the like. The entire disclosure of each of these US patent specifications is incorporated herein by reference.

  In the preferred embodiment shown in FIGS. 1-6, the situation is shown where a threaded shaft 12 with a spherical ball tip 26 rotates to generate axial forces and motions.

  The threaded shaft 12 is preferably installed so that it can move within the housing 14. The length 15 (see FIG. 5) of the threaded shaft 12 is preferably at least about 10 mm longer than the length 13 of the housing 14. In one embodiment, length 15 is at least about 25 mm longer than length 13. In another embodiment, length 15 is at least about 50 mm longer than length 13.

  In one embodiment, the first natural frequency of threaded shaft 12 is about 0.2 times that of housing 14. In another embodiment, the threaded shaft 12 has a first natural frequency that is approximately 0.1 times less than the first natural frequency of the housing 14.

  In this specification, the first natural frequency or the first natural frequency refers to the frequency or frequency of the first reference vibration mode. See McGraw-Hill Dictionary of Scientific and Technical Terms, 4th edition, page 1253 (McGraw-Hill Book Company, New York, New York, 1989). Also, pages 5 to 59 and 5 to 70 of “Mark's Standard Handbook for Mechanical Engineers” by Eugene A. A, et al. (McGraw-Hill Book Company, New York, New York) 1978), US Pat. Nos. 6,125,701, 6,591,608, 6,525,456, 6,439,282, 6,170,202. , No. 6,101,840. The disclosures of each of these US patent specifications are hereby incorporated by reference in their entirety.

  In the illustrated embodiment, the orbital motion of the nut 16 occurs because there are two normal vibration modes that act orthogonally to each other in a plane parallel to the axis of the shaft, as shown in FIG. These two orthogonal normal vibration modes are caused by the interaction of the activated transducers (such as plates 18, 20, 22 and 24) and the housing 14, and these interactions result in the orbital motion of the nut 16. And causes the threaded shaft 12 to rotate and translate.

  In one embodiment, the first natural resonance frequency or natural vibration frequency of the nut 16 is preferably at least five times the operating frequency of the motor 10. Therefore, it is desirable that the nut 16 is substantially rigid.

  In one embodiment, the threaded shaft 12 is made of metal, substantially stainless steel. In this embodiment, the threaded shaft 12 engages a metal, substantially brass nut 16.

  The material of the threaded shaft 12 and the screw nut 16 is preferably used in combination with materials that minimize wear.

  As shown in FIG. 1, the threaded shaft 12 has a number of thread grooves 17, preferably notched threads. According to one embodiment, the thread pitch is, in one embodiment, no more than about 250 threads per inch, and preferably no more than about 200 thread grooves per inch. In another embodiment, the pitch of the screws 17 is no more than about 100 threads per inch, and in another example, there are about 40-80 threads per inch.

  As shown in FIG. 18, the screw 17 engages with an inner screw 19 of the nut 16. In a preferred embodiment, the pitch of the inner threads 19 is substantially equal to the pitch of the outer threads 17.

  For convenience of illustration, except for FIGS. 5A, 5B, and 18, the screw 17 and the inner screw 19 are shown in a completely engaged state, but there is a radial gap between them. Preferably, the spacing is less than about 0.5 times the thread groove depth 35 of the screw 17 and / or the thread groove depth 33 of the inner screw 19. This radial gap is shown in FIG. 5A. Means for measuring the radial spacing are well known. U.S. Patent Nos. 6,145,805, 5,211,101, 4,781,053, 4,277,948, 6,257,845, 6, See 142,749. The entire disclosure of each of these US patent specifications is hereby incorporated by reference. Other references include pages 8-9 (mechanical elements) of the aforementioned "Mark's Standard Handbook for Mechanical Engineers".

  In FIG. 5A, the preferred engagement of screw 17 and internal screw 19 is illustrated. As is apparent from this figure, each of the screws has a tip portion 29 and each of the other screws has a tip portion 31. Each screw has a thread groove with a depth 33 and a depth 35.

  As can be seen from the preferred embodiment shown in FIG. 1, the rotation of the shaft with the track is caused by the ultrasonic track of the nut 16 connected to the vibration housing 14. In the illustrated embodiment, the threaded nut 16 is connected to the housing 14 and this is illustrated in FIG.

  As can be seen from FIG. 2, the nut 16 is disposed in the opening 11, and the nut is fixed in the opening by press fitting or adhesive means.

  In the preferred embodiment shown in FIGS. 1 and 2, the nut 16 is a cylindrical nut, but in other embodiments not shown, the nut may be a polygonal nut such as a square, hexagon, or octagon.

  In the embodiment of FIGS. 1 and 2, a number of ceramic plates (see 18 and below) are attached to the outer surface 37 of the housing 14.

  It is desirable that each ceramic plate be changed in length in accordance with the voltage applied thereto, particularly in accordance with the change. In this specification, the ceramic plate used in the present invention may be referred to as an “active ceramic plate”. In one embodiment, the active ceramic plate is selected from the group consisting of a piezoelectric plate, an electrostrictive plate, and combinations thereof. For simplicity of description, at least in the embodiment shown in FIGS. 1 and 2, this plate is described as a piezoelectric plate.

  In the embodiment of FIG. 2, four piezoelectric plates 18, 20, 22, 24 are bonded to the outer surface 37 of the housing, and these piezoelectric plates alternate electrical drive signals to the respective electrodes 21 and 23. When excited by this, orbit vibration of the nut 16 is generated (see FIG. 4).

  The number of piezoelectric plates used may be two, for example, like plates 18 and 20, or may be eight or more piezoelectric plates. The number of piezoelectric plates used is sufficient to excite motion in orthogonal planes 39, 40 (see FIG. 2).

  In order to simplify the explanation, a case where four piezoelectric plates 18, 20, 22, 24 are used is taken as an example. These plates are preferably intimately bonded to the outer surface 37 of the housing 14.

  As shown in FIG. 4, the piezoelectric plate 18 is connected to a voltage source through electrodes 21 and 23. For simplicity of explanation, the electrodes 21 and 23 are shown only for the piezoelectric plate 20, but similar electrodes are also provided for the other piezoelectric plates.

  In the preferred embodiment shown in FIG. 4, all four inner electrodes 23 are grounded. The piezoelectric material in this example is a commonly available “hard” composition with low dielectric loss and high depolarization voltage. One example is a piezoelectric material sold under the trade name “PZT-4” by Morgan Matroc company in Bedsford, Ohio. This material generally has several important properties.

  The dielectric loss factor of the preferred piezoelectric material described above is less than about 1%, preferably less than 0.5%, at a frequency of approximately 20,000 hertz or higher. As an example, at a frequency of approximately 20,000 hertz or higher, the dielectric loss factor of a certain piezoelectric material is about 0.4%.

  Accordingly, preferred piezoelectric materials have a piezoelectric charge coefficient d33 of at least about 250 picocoulombs / newtons, preferably at least about 270 picocoulombs / newtons. In one example, a preferred piezoelectric material has a piezoelectric charge coefficient d33 of about 285 picocoulombs / Newton.

  Preferred piezoelectric materials have a piezoelectric charge coefficient d31 of at least about −90 picocoulombs / newtons, preferably at least about −105 picocoulombs / newtons. In one example, a preferred material has a piezoelectric charge coefficient d31 of about −115 picocoulombs / newtons.

  One preferred piezoelectric material is a single crystal material having a piezoelectric charge coefficient d33 of at least about 2500 picocoulombs / newtons and a piezoelectric charge coefficient d31 of at least about 900 picocoulombs / newtons.

  Other suitable piezoelectric materials are described, for example, in US Pat. Nos. 3,736,532 and 3,582,540. The entire disclosure of these US patent specifications is hereby incorporated by reference.

  Furthermore, piezoelectric materials with low dielectric loss are well known to those skilled in the art and thus are described in US Pat. No. 5,792,379. The entire disclosure of this US patent specification is hereby incorporated by reference.

  One of the piezoelectric materials used in the present invention is a single crystal piezoelectric material. These materials are well known in the art, such as US Pat. Nos. 5,446,330, 5,739,624, 5,814,917, 5,763,983, etc. Are listed. The entire disclosure of these US patent specifications is hereby incorporated by reference.

  In the preferred embodiment of the invention shown in FIG. 4, the axial length of the piezoelectric plates 18, 20, 22, 24 varies in proportion to the applied voltage (Vx / 86 and Vy / 88) and the piezoelectric charge coefficient d31.

  As can be seen from FIG. 4, the piezoelectric plates 18 and 20 and the piezoelectric plates 22 and 24 act in pairs to bend the housing 14 (see FIGS. 1-2) and excite orbital resonance. AC drive signals 86 and 88 are applied to the piezoelectric plates 20 and 24 and the piezoelectric plates 18 and 22 having the polling direction 43, respectively. As is well known to those skilled in the art, the poling direction 43 is the direction of the dipole that aligns in the material during the manufacturing process of the piezoelectric material. US Pat. Nos. 5,605,659, 5,663,606, and 5,045,747 are cited as references for the polling method. The entire disclosure of each of these US patent specifications is hereby incorporated by reference.

  For each pair of plates 18, 22 and plates 20, 24, the electric field is positive with respect to the poling direction 43 of one plate and negative with respect to the poling direction of the other plate. The drive signal Vx86 is preferably applied to the plates 20 and 24, simultaneously extending one plate and contracting the other plate. As a result, the housing 14 bends in the X direction 72a / 72b (see FIG. 18) on the plane 39 (see FIG. 2). Similarly, the drive signal Vy88 is applied to the plates 18 and 22, and the housing 14 bends in the Y direction 74a / 74b (see FIG. 18) on the plane 41 (see FIG. 2).

  The housing end 45 facing the screw nut 16 is preferably supported by a guide bushing 28, but there is a slight gap between the inner diameter of the bushing and the outer diameter of the threaded shaft 12 (see FIG. 2). . The threaded shaft 12 supports the axial force 27 applied through the spherical ball tip 26 on a hard flat surface with low friction (see FIGS. 5 to 6).

  The axial force 27 transmitted through the ball tip 26 during operation of the motor 10 is preferably about 0.1-100 Newton. The axial force 27 is preferably about the same as the drive output.

  The spherical ball tip 26 (see FIG. 2) is one of the means for connecting the threaded shaft 12 to a low friction torque load 27 (see FIG. 5). One skilled in the art will appreciate that other means can be employed to transfer motion from a rotating shaft to a moving load. For example, in some cases, rolling bearings can be used, and in some cases, arcuate loads that contact the flat surface of the threaded shaft 12 can be utilized. Reference examples of coupling means include US Pat. Nos. 5,769,554 and 6,325,351. The entire disclosure of these US patent specifications is hereby incorporated by reference.

  1 and 2, the end 45 of the housing 14 facing the screw nut 16 is provided with a flange against which the stationary cover 58 (see FIG. 21) abuts. The thread pitch of the shaft 12 and nut 16 converts tangential forces and movements on the track into axial forces and movements. This pitch can be arbitrarily selected to optimize force magnification, deceleration, resolution improvement, holding power when the power is shut off, and the like.

  In the ultrasonic linear motor 30 shown in FIGS. 7 to 12, preferably, four piezoelectric stacks 36, 38, 40, and 42 (see FIGS. 7 to 8) are used to generate ultrasonic vibrations. The threaded shaft 12 with the spherical ball tip 26 rotates to produce axial force and motion. The rotation is caused by the ultrasonic orbital motion of the nut 16 connected to the vibration cylinder 32. The four piezoelectric stacks 36, 38, 40, 42 are coupled to the end of the cylinder facing the nut 16 and the base ring 34. These four stacks are assembled using known assembly and electrical connection methods, and the inner leads of the stack are preferably connected together with a common ground 35. The axial length of each stack changes in proportion to the applied voltage and the piezoelectric charge coefficient d33. Piezoelectric materials are commonly available “hard” compositions with low dielectric loss and high depolarization voltage. AC electrical drive signals 86 and 88 are connected to the outer leads of each piezoelectric stack 44 to excite the orbital vibration of the nut. The stacks 36, 38, 40, and 42 each work in pairs and rotate the tube to excite the orbital resonance. AC electrical drive signals Vx86 and Vy88 are applied to stacks 38 and 42 and stacks 36 and 40, respectively, in polling direction 43. For each pair of stacks 38 and 42 and stacks 36 and 40, the electric field of one stack is positive with respect to the polling direction 43 and the electric field of the other stack is negative with respect to the polling direction. A drive signal Vx86 is applied to the stacks 38 and 42 to stretch one stack and simultaneously shrink the other stack. As a result, the tube rotates in the X direction 72a / 72b (see FIG. 18). Similarly, a drive signal Vy 88 is applied to the stacks 36 and 40 to move the end of the tube in the Y direction 74a / 74b (see FIG. 18). The base ring 34 facing the nut 16 supports the guide bushing 28, and a slight gap exists between the inner diameter of the bushing and the outer diameter of the shaft. The threaded shaft 12 supports an axial force 27 applied through the spherical ball tip 26 using a low friction hard flat surface. The base ring 34 is a contact point of the stationary cover 58 (see FIG. 21). The thread pitch of the shaft 12 and nut 16 converts the tangential force and motion of the track into axial force and motion. This pitch can be selected appropriately in order to optimize the power magnification, deceleration, resolution improvement, holding power when the power is cut off, and the like.

  In the ultrasonic linear motor 50 shown in FIGS. 13 to 17, a piezoelectric tube 54 having a quadrant electrode is used to generate ultrasonic vibration. The threaded shaft 12 with the spherical ball tip 26 rotates to produce axial force and motion. This rotation is generated when the nut 16 connected to the vibrating piezoelectric tube 54 orbits with ultrasonic waves. The inner diameter of the piezoelectric tube is an electrode 61 continuously, and this electrode is grounded 63. On the other hand, the outer diameter of the piezoelectric tube is divided into four separate electrodes 60, 62, 64, 66. Piezoelectric materials are commonly available “hard” compositions with low dielectric loss and high depolarization voltage. The axial length of the piezoelectric tube below the electrodes 60, 62, 64, 66 changes in proportion to the applied voltage and the piezoelectric charge coefficient d31. Electrodes 60 and 64 and electrodes 62 and 66 act in pairs to bend the tube and excite orbital resonance. AC electrical drive signals 86 and 88 are applied in the poling direction to electrodes 60 and 64 and electrodes 62 and 66, respectively. For electrode pairs 60 and 64 and 62 and 66, the electric field of one electrode is positive with respect to the poling direction and the electric field of the other electrode is negative with respect to the poling direction. The drive signal Vx86 is applied to the electrodes 60 and 64, and expands one electrode and simultaneously contracts the other electrode. Thereby, the tube bends in the X direction 72a / 72b (see FIG. 18). Similarly, a drive signal Vy88 is applied to the electrodes 62 and 66 to bend the tube in the Y direction 74a / 74b (see FIG. 18).

  The tube end facing the nut 16 is joined to the base flange 52 to support the guide bushing 28. There is a slight gap between the threaded shaft and the bushing. The threaded shaft 12 supports the axial force applied through the spherical ball tip 26 using a low-friction hard flat surface. The base flange is a contact point of the stationary cover 58 (see FIG. 21). The thread pitch of the shaft 12 and nut 16 converts the force and motion in the tangential direction of the track into axial force and motion. This pitch can be arbitrarily selected in order to optimize force magnification, deceleration, resolution improvement, holding power when the power is cut off, and the like.

  18 and 19 show the operation of the motor 10 shown in FIG. 1 and the corresponding drive signals 86 and 88 used to perform this operation. The piezoelectric plates work in pairs, as one 70 expands, the other 69 contracts 69 at the same time to bend the housing. The AC drive signals Vx86 and Vy88 are preferably sinusoidal waves of equal amplitude (see symbols 90 and 91) and a phase shift of 90 degrees (see symbol 92), generating a circular orbit. The positive phase shift 92 imparts a positive orbital motion to the nut 16 and causes a positive rotation 96 and a positive movement 98 on the shaft 12. On the other hand, the negative phase shift 92 imparts negative orbital motion to the nut, causing negative rotation and negative movement of the shaft. FIG. 19 shows that for a rotation in one direction, the single trajectory cycle of the motor and the corresponding drive signal amplitudes 90 and 91 are continuous every 90 degrees increments 76, 78, 80, 82 and 84. Is shown in In FIG. 18, the bending state and the orbital motion of the cylinder are shown in the X direction (see symbols 72a and 72b) and the Y direction (see symbols 74a and 74b). When the nut contacts the side of the shaft at a certain position 73a, a gap 73b is created at the opposite position (see FIG. 5B), but this contact imparts tangential force and motion, and each shaft cycle has a shaft. 12 is rotated to a small scale (see reference numeral 96 in FIG. 18) and moved (see also reference numeral 98). The amount of rotation and movement per cycle depends on many factors, including the amplitude of the track, the magnitude of the force 27 acting on the shaft, the coefficient of friction, the surface finish of the screw, and the like. If there is no slip at the contact portion 73a between the nut and the shaft, the movement for each cycle is nominally proportional to the size of the gap in the warp direction between the screws. In general, as drive amplitudes 90 and 91 increase, the diameter of the track also increases, the standard contact force between shaft 12 and nut 16 also increases, the degree of slip decreases, the speed increases, torque and force also increase. Increase.

  The ultrasonic frequency is the reciprocal of the period (see period 94a and period 94b in FIG. 19), which is preferably the same for both signals and coincides with the first resonant frequency that bends the housing 14.

  20 to 25, the motor assembly 100 is obtained by integrating the motor 10, the cover 58, and the knurled knob 102. The threaded shaft 112 is located inside the motor 10. The threaded shaft 112 shown in FIG. 21 is similar to the threaded shaft 12 shown in FIG. 1, but differs from that of FIG. 1 in that a smooth spindle 113 is incorporated. The spindle 113 can be connected to the knurled knob 102. The cover 58 is attached to the motor 10 with a flange 45. The knurled knob 102 rotates and translates with the shaft 112 without contacting the cover 58.

  FIG. 21 is an exploded view of the motor assembly 100, and FIG. 22 is a cross-sectional view of the motor assembly 100.

  23A, 23B and 23C illustrate the motor assembly 100. FIG. FIG. 23A is a perspective view of the motor assembly shown in FIG. 20 viewed from the reverse side. FIG. 23B illustrates that the motor assembly 100 including the knob 102 and the shaft 112 rotates in the clockwise direction indicated by reference numeral 103 and translates in the direction of the arrow 105. For comparison, FIG. 23C shows a state in which the motor assembly 100 rotates in the counterclockwise direction 107 and translates in the direction of the arrow 109.

  For the sake of brevity, electrical connection means to the various components of the motor assembly are not shown.

  The attachment of the knurled knob 102 is convenient for operating the motor assembly 100 manually or in combination with manual and electric means. Therefore, the assembly 100 can be used as a fine drive alternative that can be used for both normal manual adjustment and motorized automatic preparation.

  Although not shown, it is also possible to mechanically attach an external motor to the knurled knob 102 and to carry a second means for mechanically moving the assembly.

  24A and 24B show an adjustable linear stage 106 that includes a motor assembly 100 and linear movement stages 104a and 104b connected thereto. In the illustrated example, the motor assembly cover 58 is attached to the bottom stage 104b, and the ball chip 26 is in contact with the upper stage 104a. As the knurled knob 102 moves clockwise, a linear movement in the direction of the arrow 105 is born. Conversely, when the knurled knob 102 moves counterclockwise, a linear movement in the direction of arrow 109 occurs.

  In the embodiment shown in FIGS. 24A and 24B, a spring assembly 111 with pins 115 and 116 (shown schematically with dashed lines) biases the moving stage 104a / 104b in the direction of arrow 109. In the illustrated example, the pin 115 is attached to the movable part 104a at the upper part of the assembly, and the pin 116 is attached to the stationary part 104b at the lower part of the assembly. The spring assembly 111 is used to generate an axial force 27 (see FIGS. 5-6).

  FIG. 25 is a perspective view of the micromanipulator 120 that can be moved. The stages 106a, 106b, and 106c can move along the X axis, the Y axis, and the Z axis.

  The above is a description of the preferred embodiments of the present invention in some detail. However, the details of the structure, the combination of bahts, the arrangement of parts, etc. in these embodiments are not departed from the technical idea of the present invention. Can be changed.

  This specification describes an apparatus for driving a shaft assembly comprising a threaded shaft having a rotating shaft and a nut engaged therewith, the assembly causing ultrasonic vibrations in the nut to produce the shaft. Is rotated in the axial direction at the same time. From the teachings of this specification, those skilled in the art will be able to make similar devices that vibrate the threaded shaft to rotate and move the nut at the same time.

FIG. 4 is a perspective view of a motor having four rectangular piezoelectric plates. The exploded view of the motor shown in FIG. FIG. 2 is an end view of the motor shown in FIG. 1. FIG. 2 is an electrical connection diagram of the motor shown in FIG. 1. Sectional drawing along the AA line (30) of FIG. Enlarged view of 47 in FIG. 5 (when the motor is powered off and there is an external load) Enlarged view similar to FIG. 5A (when the motor is operating) Sectional drawing along the BB line (32) of FIG. The perspective view of the motor which has four piezoelectric stacks. FIG. 8 is an exploded view of the motor shown in FIG. 7. FIG. 8 is an end view of the motor shown in FIG. 7. FIG. 8 is an electrical connection diagram of the motor shown in FIG. 7. Sectional drawing along the AA line (48) of FIG. Sectional drawing along the BB line (46) of FIG. The perspective view of the motor which has four piezoelectric tubes with an external electrode. FIG. 14 is an exploded view of the motor shown in FIG. 13. FIG. 14 is an end view of the motor shown in FIG. 13. FIG. 14 is an electrical connection diagram of the motor shown in FIG. 13. Sectional drawing along the AA line (56) of FIG. Explanatory drawing which shows the orbital motion of the nut of a motor shown in FIG. 1, and rotation and movement of a shaft. FIG. 19 is a schematic diagram of an electrical drive signal necessary to produce the motion shown in FIG. The perspective view of the motor assembly which integrated the motor and linear stage of FIG. FIG. 21 is an exploded view of the motor assembly shown in FIG. 20. FIG. 21 is a cross-sectional view of the motor assembly shown in FIG. 20. Rear view of the motor assembly shown in FIG. FIG. 21 is an explanatory diagram showing rotation and forward movement of the motor assembly shown in FIG. 20. FIG. 21 is an explanatory diagram showing movement in a direction opposite to the rotation of the motor assembly shown in FIG. 20. Drawing of a motor assembly integrated with a linear stage moving in the forward direction. Drawing of a motor assembly integrated with a linear stage operating in the opposite direction. Drawing of motor assembly integrated with 3-axis stage system.

Claims (20)

A device for driving a threaded shaft assembly having a threaded shaft having a rotation axis and a nut screwed to the shaft;
a) the assembly includes means for applying ultrasonic vibration to the nut, thereby rotating the threaded shaft and simultaneously moving in the axial direction;
b) the threaded shaft is operatively connected to a load;
c) The drive apparatus further comprising means for the assembly to apply an axial force to the threaded shaft.   The apparatus of claim 1 wherein said assembly comprises means for moving said nut in an orbital direction.   The apparatus of claim 1, wherein the nut is substantially rigid.   The apparatus of claim 1, wherein the threaded shaft assembly further comprises a housing disposed therein.   The apparatus of claim 4, wherein the nut is attached to a housing.   6. The apparatus of claim 5, wherein the housing has a first bending resonance frequency greater than 20,000 cycles / second and the first bending mode is in a plane parallel to the axis of rotation.   The apparatus of claim 6, wherein the housing has a second bending resonance frequency equal to the first bending resonance frequency, and the second bending mode is in a plane orthogonal to the first bending mode.   7. The apparatus of claim 6, further comprising means for orbiting the nut at a frequency of at least about 20,000 laps / second.   9. The apparatus of claim 8, further comprising means for moving the threaded shaft in a direction substantially parallel to the axis of rotation.   The apparatus of claim 8, further comprising means for rotating the threaded shaft while moving the threaded shaft in a direction substantially parallel to the axis of rotation.   The apparatus of claim 8, wherein the means for orbiting the nut comprises at least two transducers for converting electrical energy into force.   The apparatus of claim 11, wherein the transducer is selected from the group consisting of a piezoelectric transducer, an electrostrictive transducer, a magnetostrictive transducer, an electrostatic transducer, an electromagnetic transducer, or a combination thereof.   The apparatus of claim 12, wherein the transducer is a piezoelectric transducer.   The apparatus of claim 13, wherein the piezoelectric transducer is a piezoelectric plate.   The apparatus of claim 14, wherein the piezoelectric plate comprises a piezoelectric material having a dielectric loss factor of less than about 1% at a frequency greater than about 20,000 hertz.   The apparatus of claim 14, wherein the piezoelectric plate comprises a piezoelectric material having a dielectric loss factor of less than about 0.5% at a frequency greater than about 20,000 hertz.   The apparatus of claim 1, wherein the threaded shaft has a thread pitch of about 40-250 per inch.   The apparatus of claim 1, wherein the threaded shaft is disposed within a housing and coupled to a knob.   19. The apparatus of claim 18, further comprising a movable stage that connects the threaded shaft and connected to the housing.   20. An apparatus comprising at least two movable stages in contact with each other, each of the movable stages comprising the apparatus of claim 19.

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