Showing papers on "Piezoelectric motor published in 1998"

Contact mechanics of piezoelectric ultrasonic motors

Abstract: Piezoelectric ultrasonic motors are driven by tangential stresses in the interface between stator and rotor. These stresses are generated by the elliptical motion of the material points of the stator or rotor surface and depend on frictional processes in the contact area. The contact mechanics of piezoelectric ultrasonic motors determines the operational characteristics, like rotational speed and torque or transmitted mechanical power and efficiency. Wear properties and lifetime of piezoelectric ultrasonic motors are also determined by contact mechanics. The goal of the present paper is to summarize the state of the art in the understanding of some fundamental processes governing the contact mechanics of piezoelectric ultrasonic motors. After a short introduction, a survey of publications devoted to the subject will be given. Then, an attempt will be made to classify the mechanical models, which were developed in order to explain the contact mechanics of piezoelectric ultrasonic motors, according to the physical effects which have been taken into account in their derivation. Some results concerning the choice of proper contact materials, wear and lifetime of ultrasonic motors will be addressed in a separate section. Finally a summary and outlook will be given and open questions for future research will be formulated.

Ink-jet recording head with piezoelectric device and method for manufacturing the same

Abstract: A piezoelectric device for an ink jet print head that has a greater displacement at a low drive voltage The ink-jet recording head includes a vibration plate, on which is mounted one or more piezoelectric devices that change the volumes of pressure chambers upon application of a voltage The device is mounted at least on one face of a pressure chamber substrate that is to be filled with ink Such piezoelectric device includes a second piezoelectric layer having a piezoelectric constant g of a constant value or higher; and a first piezoelectric layer having a dielectric constant of a specific value or higher Since the piezoelectric constant d of the piezoelectric device correlates with the product of the largest piezoelectric constant g and the largest dielectric device of the piezoelectric devices, a piezoelectric constant d larger than in the conventional case, ie, having a greater displacement, can be obtained

The Measurement of High-Power Characteristics for a Piezoelectric Transducer Based on the Electrical Transient Response

Abstract: In this paper, the theoretical and experimental considerations on the high-power characteristics of a piezoelectric transducer are presented. First, we propose a new measurement method for the large vibration amplitude region using an electrical transient response to eliminate the effect of temperature rise. Then, a new loss mechanism concerning the piezoelectric effect is explained by observing the relationship between the vibration velocity and the current and their harmonics. A `piezoelectric loss' is newly introduced in the equivalent circuit model to describe the real loss phenomena clearly.

Fabrication process of high aspect ratio elastic and SU-8 structures for piezoelectric motor applications

Abstract: We report on recent advances in micro fabrication technology using micromolding and high aspect ratio structuring of photopolymer. The direct application is the realization of components for millimeter-size, ultrasonic piezoelectric motors. A new fabrication process using a thick epoxy-based material (SU-8) and the electroplating of nickel is demonstrated. Photopolymer structures have also been realized and released using a positive tone resist as sacrificial layer. The main advantages over past fabrication methods are better design flexibility, simplicity of the fabrication process, the capability to combine metallic materials (Ni) with polymeric materials ( SU-8), and the use of positive tone resist as a sacrificial layer. (C) 1998 Elsevier Science S.A. All rights reserved.

Non-disturbing electric field sensor using piezoelectric and converse piezoelectric resonances

Abstract: This invention relates to an electric field sensor for near field measurement. The electric field sensor of the present invention uses both piezoelectric and converse piezoelectric resonances. Composed of no metallic parts, the probe of the sensor minimizes field disturbance. The most distinguished feature of this probe is that a signal is transmitted outside neither electrically nor optically, but mechanically.

A linear piezoelectric motor

Abstract: The development of a linear hybrid transducer type piezoelectric motor is shown. This design has the advantages of light weight, macro- and micro-positioning, and large force/velocity output. The motor consists of a longitudinal actuator that provides output displacement and force, and two alternating clamping actuators which provide the holding force. The advantages of this design over other types of piezoelectric motor are shown. Significant design considerations for the development of a piezoelectric motor (including material choices, shear loads on piezoelectric materials, and contact surface interaction) are discussed. A simulation, including a finite element analysis of the system, is used to predict the motor response to various input sets. A prototype motor is built and its characteristics are compared to theoretical predictions.

Piezoelectric assembly for micropositioning a disc drive head

Abstract: An assembly and method for micropositioning a disc drive head is described. An implementation of the assembly includes a gimbal, a piezoelectric element bonded to the gimbal and electrically connected to a voltage source, and a slider connected to the piezoelectric element. The assembly may also include at least a second piezoelectric element bonded to the gimbal and connected to the slider. The piezoelectric elements may be made of PZT material, and each may be in a monomorph or bimorph configuration.

Optical scanner having piezoelectric drive

Abstract: A piezoelectric circuit drives mirror movement along a scan path. The scanner includes a support, a reflective surface and a piezoelectric circuit. The support alternately rotates about an axis of rotation in a first direction and a second direction. The reflective surface moves with the support. The piezoelectric circuit is mechanically coupled to the support, and includes a first piezoelectric volume and a second piezoelectric volume. During a first portion of a drive cycle drive signals of opposite polarity cause the volumes to deform in opposing manner. The deformation causes the support to rotate in the first direction. During a second portion of the drive cycle the polarity of the drive signals switches again causing the volumes to deform, but in opposite manner than during the first portion of the drive cycle. The deformation causes the support to rotate in the second direction.

Footwear incorporating piezoelectric spring system

Abstract: An article of performance enhancing footwear having a piezoelectric spring apparatus in the sole member. Walking or running applies a first force deforming a piezoelectric actuator, thereby generating electrical energy. An energy storage circuit stores electrical energy generated by the piezoelectric actuator. Sensing means is provided to sense the release of a second force greater than the first force, which triggers the release of stored electrical energy back into the piezoelectric actuator. The resulting deformation of the piezoelectric actuator imparts a force into the bottom contact surface of the sole member.

A piezoelectric motor using flexural vibration of a thin piezoelectric membrane

Abstract: This paper describes a new implementation of a disk-type piezoelectric motor, whose stator is a commercial available piezomembrane composed of a nickel alloy disk to which a piezoceramic disk is bonded. The two disks are concentric, and the total thickness is very small. Ultrasonic motors are based on the concept of driving a rotor by mechanical vibration excited on a stator, via the piezoelectric effect. The rotor is in contact with the stator, and the driving force is the frictional force between rotor and stator. To transform the mechanical vibration of the stator in the rotor rotation, a traveling wave must be excited on the stator surface. The proposed motor can be regarded as a disk-type, single wavelength motor in which the traveling wave is due to the natural flexural vibration of the piezomembrane at low frequency. The behavior of the stator is analyzed both theoretically, by using the theory of isotropic and homogeneous vibrating plates, and by means of a commercial finite element computer code, finding a good agreement with the experimental results. The main features of the motor are very small thickness, appreciable torque, and high speed, obtained with low input power at low voltage; the intended application is to substitute the moving-coil in analogic instrumentation.

A new low voltage piezoelectric micromotor based on stator precessional motion

Abstract: In this work a piezoelectric motor is described whose stator is composed of a cylindrical steel axle fitted at the center of a thin piezoelectric membrane. The rotor consists of a cylindrical permanent magnet, pressed in contact with the top surface of the axle, by means of magnetic forces. A travelling wave, at the natural flexural vibration of the thin piezoelectric membrane, is excited via the piezoelectric effect. The vertical displacement of the membrane is geometrically amplified by the central axle, obtaining a wide precessional motion of the axle. On this motion is based the transmission mechanism of the proposed motor. The motor is able to give a relatively high speed (/spl ap/3500 rpm) and torque (1.8/spl middot/10/sup -5/ N/spl middot/m) by using a commercial piezoelectric membrane (diameter 32 mm, thickness 0.2 mm), driven at relatively low voltage (18 V P-P). The very small thickness of the stator makes this motor suitable for microsystem applications. A simple analytical model of the transmission mechanism is discussed, and the predicted results are compared with experimental measurements, with a satisfactory agreement.

Shear mode piezoelectric microactuator for magnetic disk drives

Abstract: We developed a new piezoelectric microactuator for dual-stage actuator systems in magnetic disk drives. This actuator exploits the shear mode of piezoelectric elements and drives the head suspension assembly. This paper describes the structure of our piezoelectric actuator, its mechanical characteristics, and the experimental results of a life test after driving the piezoelectric elements in an atmosphere of high temperature and humidity.

Development and characterization of a rotary motor driven by anisotropic piezoelectric composite laminate

Abstract: A new actuation principle is introduced in this paper to drive a rotary motor by an anisotropic piezoelectric composite laminate. The driving element is a three layer laminated beam with piezoceramics sandwiched between two anti-symmetric composite laminae. By taking advantage of material anisotropy, torsional motion can be induced from in-plane strain actuation. With this structural coupling, a rotary motor can be implemented. In addition to analytical formulation and conceptual design, a prototype has been fabricated. Actual motion was observed in the laboratory to verify the proposed actuation principle. The prototype was characterized for rotating speed, torque, power output, efficiency and stability. The performance of this new piezoelectric motor is discussed in detail.

Inside indicating device for a vehicle

Abstract: The indicating device has a pair of piezoelectric elements (20) fitted to the rim (35) of a steering wheel (13) at diametrically-opposed portions (35a, 35b) gripped by the driver of the vehicle; and a drive unit (22) for driving the piezoelectric elements (20). The piezoelectric elements (20) are bimorph ceramic plate elements of series or parallel type, each have a pair of terminals (21) connected to the drive unit (22), and, when activated, generate mechanical vibrations perceivable by touch and ear by the driver. The drive unit (22) driving the piezoelectric elements (20) generates a first and second alternating-voltage control signal (C1, C2), each of which is applied between a respective pair of terminals (21) of the piezoelectric elements (20), and has a frequency substantially equal to the resonance frequency of the respective piezoelectric element (20).

A high bandwidth piezoelectric suspension for high track density magnetic data storage devices

Abstract: Maintaining the trend towards higher track densities and data rates in magnetic recording devices requires track following servo systems of increasing bandwidth for reliable storage and retrieval of data. The increase in bandwidth is limited by the presence of mechanical resonance modes and other nonlinearities in the voice coil motor (VCM) actuators. One approach to overcoming the problem is by using a dual-stage servo mechanism. In such a mechanism, a VCM is used as a primary stage while a microactuator is used as a secondary stage. The paper proposes a planar piezoelectric actuator design and a piezoelectric suspension made of the planar piezoelectric actuator. The design has a high bandwidth, simple structure and low cost. A prototype of the piezoelectric suspension is designed, fabricated and tested. The experimental results demonstrate that the piezoelectric suspension can satisfy the requirements for the dual-stage servo system.

Actuator using electromechanical transducer and apparatus employing the actuator

Abstract: A linear actuator using a piezoelectric element having high mechanical strength, high driving efficiency and high reliability in which left and right end portions of the piezoelectric element in a tubular shape whose major component is PZT are fixedly supported by supporting members and a slider is frictionally coupled to the piezoelectric element, the slider frictionally coupled to the piezoelectric element is moved by causing elongation displacement and contraction displacement respectively to electrodes at the left and right end portions of the piezoelectric element when drive pulses each in a saw tooth wave having gradual rise portion and steep fall portion are applied to the electrodes at the left and right end portions of the piezoelectric element in a tubular shape and the slider can continuously be moved by continuously applying the drive pulses.

Resonant piezoelectric ring transformer

Abstract: We have investigated experimentally the factors which influence electrical and mechanical losses as well as harmonic generation in a piezoelectric ceramic. To this end, we have used a piezoelectric ring transformer. The experiments were done for rings with different dimensions of electrodes. The secondary circuit was open, short circuited or loaded by a small resistance. The results obtained can be used as a basis for the theoretical analysis of physical phenomena in piezoelectric ceramics under high power excitation. They can also be used to differentiate mechanical and electrical losses during transformer operation. This can have large practical importance when elaborating new ceramic compositions for various applications (actuators, sensors, etc.).

Thickness vibrations of rotating piezoelectric plates

Abstract: Thickness vibrations of a piezoelectric plate rotating at a constant angular velocity about its normal are studied using the equations of linear piezoelectricity. The transcendental equation that determines the resonant frequencies is derived for materials with general anisotropy and solved for specific materials of polarized ceramics and rotated Y-cut quartz. The results are useful in the understanding and analysis of plate piezoelectric gyroscopes.

Bimorph-based piezoelectric air acoustic transducer: model

Abstract: A new type of bimorph-based piezoelectric air transducer with the working frequency range of 200–1000 Hz has recently been developed [B. Xu, Q. Zhang, V.D. Kugel, L.E. Cross, Piezoelectric air transducer for active noise control, Proc. SPIE, 2717 (1996) 388–398]. In the present work, basic acoustic characteristics of this device and its piezoelectric elements are analyzed. To model the vibration spectrum of the transducer, a one-dimensional approach is developed where inertia, elastic and damping forces are included. Analytical equations describing mechanical vibrations and electrical impedance of piezoelectric bimorph cantilevers under external forces are derived. In order to describe various losses in the transducer, complex piezoelectric, dielectric, and elastic constants are used. Results of the modeling are in good accord with experimental data. The suggested model can be used for device optimization.

Transducer for an ultrasonic linear motor with flexible driving part

Abstract: An ultrasonic motor using two sandwich-type vibrators is a high-speed and large-thrust motor. The maximum speed is 3.5 m/s and the maximum thrust is 51 N. But the maximum efficiency is low, 28%. We thought a slip between the driving part and the rotor was a cause of the low efficiency. The slip is caused by a speed difference between the driving part whose speed changes like a sine curve and the rotor whose speed is almost constant. Then we made a transducer for an ultrasonic linear motor with a flexible driving part. The flexible driving part has 4 cuts and can bend slightly so that the speed difference should decrease. The decrease was verified by a distortion of the sine curve of the flexible driving part and meant a decrease of the slip.

Effect of Pressing Force Applied to a Rotor on Disk-Type Ultrasonic Motor Driven by Self-Oscillation

Abstract: In this paper the relationship between the pressing force applied to a rotor and the rotation characteristic of an ultrasonic motor driven by self-oscillation are discussed. The motor used here is an in-phase drive-type ultrasonic motor using two degenerate bending vibration modes of a disk. The picking-up electrical signal caused by self-oscillation is positively fed back into the piezoelectric ceramics for driving through an operational amplifier and a step-up transformer. The pressing force applied to a rotor was measured using a force gauge coupled to the shaft of the ultrasonic motor. As a result, it was confirmed that the selection of the picking-up position for the feedback signal is important for a stable starting and running of the disk-type ultrasonic motor driven by self-oscillation.

Piezoelectric resonator adapted to generate a harmonic wave in a thickness extensional vibration mode

Abstract: A piezoelectric resonator adapted to generate a harmonic wave in a thickness extensional vibration mode includes a piezoelectric member, a plurality of excitation electrodes disposed on or within the piezoelectric member and superposed on one another in the thickness direction of the piezoelectric member with piezoelectric layers of the piezoelectric member interposed therebetween, lead-out electrodes respectively connected to the excitation electrodes and extending to side surfaces of the piezoelectric member at the same vertical positions as the excitation electrodes, and a dummy electrode disposed at least one of the vertical positions at which the excitation electrodes are disposed and at such a position so as to have a symmetrical relationship relative to the corresponding excitation electrode with the lead-out electrode connected to the excitation electrode.

Dual axial gyroscope with piezoelectric ceramics

Abstract: A piezoelectric device is used in an dual axial gyroscope system and includes a piezoelectric exciter for generating a linear velocity on a first axis; a first piezoelectric detector element, placed on a surface of the piezoelectric exciter in a direction orthogonal to the first axis, for detecting a first Coriolis force provided in a direction orthogonal to the first detector; and as second piezoelectric detector element, placed on the surface of the piezoelectric exciter in a direction orthogonal to the first axis and the first detector, for detecting a second Coriolis force provided in a direction orthogonal to the second detector element.

A piezoelectric pseudoshear multilayer actuator

Abstract: A type of high strain piezoelectric ceramic actuator, namely, pseudoshear multilayer actuator, is described. In this structure, a stack of prepoled rectangular piezoelectric transducer ceramic sheets are conductively bonded at alternate ends, while the bottom layer bonded on a fixed base. When driven, alternate layers elongate or shrink in the same direction through converse piezoelectric effect, which results in the actuator structure developing a strong shear motion about the face perpendicular to the bonding direction. Experimental results indicate that more than 50 μm displacement can be achieved from the top layer for an actuator consisting of 18 layers with dimensions of 25.57 mm×4.02 mm×0.51 mm (1×w×t). By reducing ceramic sheet thickness and using more layers, even large displacement can be obtained, and driving voltage can also be reduced while keeping the same field level. Nonlinear piezoelectric response under high driving field further enhances the displacement level.

Generation device and electronic equipment

Abstract: PROBLEM TO BE SOLVED: To prevent a piezoelectric body or the like from deterioration due to friction and wear by applying a medium to the piezoelectric body in pulse-like manner for vibrating it by a vibration means. SOLUTION: A piezoelectric body 110 is formed into a disk-shaped bimorph type and is provided with electrodes 114 and 115, that are formed on the surface of two piezoelectric plates 112 and 113 adhering to the front and rear surfaces of an intermediate electrode that is connected to a recharging system 180. A vibration means 120 is provided with a medium-giving means 121 and a drive force transfer means 122 for transferring a drive force from a drive system 160. In this case, the vibration means 120 gives a medium to the piezoelectric body 110 in pulse like manner for generating power. Therefore, since the piezoelectric body vibrates due to the non-contact interaction with the vibration means, deterioration due to the friction and wear of the piezoelectric body can be eliminated. COPYRIGHT: (C)1999,JPO

Piezoelectric transformer having a high energy-conversion efficiency and high reliability

Abstract: A piezoelectric transformer is described that features high energy-conversion efficiency and high reliability. Four driver piezoelectric ceramic plates are provided on the upper and lower surfaces at both ends of a generator piezoelectric ceramic plate having a rectangular shape, the driver piezoelectric ceramic plates having the same width and one-third the length of the generator piezoelectric ceramic plate. Vibration is not hindered and the energy-conversion efficiency is therefore increased in this construction because the draw-out positions of the four input electrodes and three output electrodes are all positioned at the nodes of mechanical vibration. In addition, the reliability of lead wire connections is improved because vibration places no load on the lead wires. Finally, input capacitance and step-up capabilities can be raised by adopting a multilayer construction for the driver piezoelectric ceramic plates.

Thickness extensional vibration mode piezoelectric resonator and piezoelectric resonator component

Abstract: A thickness extensional piezoelectric resonator utilizes harmonics of a thickness extensional vibration mode and has a significantly reduced size and significantly increased capacitance while not being susceptible to the effects of the stray capacitance of a circuit board upon which the resonator is mounted. The resonator includes a piezoelectric strip, first and second excitation electrodes located on one of two respective major surfaces of the piezoelectric strip, and internal electrodes disposed inside the piezoelectric strip. The first and second excitation electrodes are located on opposite sides of the piezoelectric strip. The internal electrodes are located opposite to the first and second excitation electrodes to thereby define a vibrating portion. Vibration-attenuating portions are located on opposite sides of the vibrating portion only along the longitudinal direction of the piezoelectric strip. No vibration-attenuating portions are located in the lateral direction of the piezoelectric strip.

Vibration communication system by means of piezoelectric element

Abstract: PROBLEM TO BE SOLVED: To desirably decrease the number of components of a communication system, used for small-sized electronic equipment, so as to facilitate the electronic equipment main body small-sized and lower the cost secondarily and to lower the power consumption of small-sized portable equipment to realize long-time operation by a battery power source. SOLUTION: The communication system has on its transmission side a data modulating means 1, a piezoelectric element driving means 2 which is connected to the voltage output of the data modulating means 1, and the piezoelectric element 3 which is driven by the piezoelectric element driving means 2 and on its reception side a piezoelectric element and a data demodulating means 6 which inputs a voltage from the piezoelectric element, propagates the pressure vibration generated by the piezoelectric element 3 having received the voltage output of the modulating means 1 of the transmission-side system to the piezoelectric element of the reception-side system through a transmission medium which can propagate the pressure vibration or a vibration transmission part 14 which efficiently transmits a frequency component used to communicate the piezoelectric element vibration to the transmission medium, and converts the vibration into a voltage signal by the piezoelectric element of the reception-side system and demodulates it.

Some analytical results on piezoelectric gyroscopes

Abstract: Equations for linear piezoelectricity are formulated in a reference frame rotating at a small, constant angular velocity. Propagation of plane waves in an infinite rotating body is examined. Thickness vibration of infinite plates rotating about their normal are discussed. The equations are then simplified by a perturbation procedure based on the small angular velocity. The perturbation procedure simplifies the problem and shows the mechanism of piezoelectric gyroscopes. Specific gyroscopes of plates in thickness shear-thickness shear motion, beams in flexure-flexure motion, and circular cylindrical shells in torsional-axisymmetric radial motion are studied by equations of piezoelectric beams, plates, and shells in conjunction with the perturbation procedure. Free vibration frequencies and modes as well as conditions for double resonance are obtained. Forced vibration is also studied which yields simple expressions for the sensitivity of the gyroscopes. The propagation of surface waves on a rotating half space is also discussed which suggests the possibility of surface mode piezoelectric gyroscopes.