CN204633636U - A Micro Ultrasonic Motor Driven by Electrostatic Force - Google Patents

Abstract

The utility model discloses a kind of Miniature ultrasonic motor of static-electronic driving, comprising: silica-based stator, rotor, bearing and elastic forepressure device, described silica-based stator upper surface is provided with a detent projection; One end of described rotor is sheathed in bearing and rotates, and described rotor contacts with the detent projection of described silica-based stator; Described elastic forepressure device applies precompression vertically in rotor, makes to produce normal pressure between rotor and silica-based stator, and described silica-based stator produces ultrasonic vibration under driving voltage effect, and the detent projection of silica-based stator is rotated by frictional force drives rotor.The features such as the utility model meets that volume is little, structure is simple, material and mature preparation process.

Description

A Micro Ultrasonic Motor Driven by Electrostatic Force

technical field

The utility model belongs to the technical field of ultrasonic motors, in particular to a miniature ultrasonic motor based on the electrostatic force exciting the ultrasonic vibration of the structure.

Background technique

Compared with conventional electromagnetic motors, especially in the small size (mm-cm) range, ultrasonic motors have shown many unique advantages, such as relatively high power density, large driving force, and relatively high efficiency. Traditional electromagnetic motors have become difficult to manufacture in the order of several millimeters, and its efficiency is only a few percent (<8%) at several millimeters, because it lacks a strong enough magnetic field . The ultrasonic motor uses the ultrasonic vibration of the structure (stator) and the interface friction to drive the movement of the rotor (mover), and its efficiency is basically independent of the size, and there is no magnetic field problem. Ultrasonic motors maintain the characteristics of low speed and high torque even in millimeter size. As precision driving components, ultrasonic motors are used in key components of some high-tech products such as mobile phones, medical imaging systems and other miniature medical equipment. Many new driving technologies, such as voice coil motors, piezoelectric drivers, ultrasonic motors, etc., have been developed rapidly and successfully applied in many fields. Among these micro-drive technologies, ultrasonic motors have shown obvious advantages in terms of motion stroke, driving force, driving accuracy and power consumption.

The idea of using high-frequency vibration and interface friction of structures to output motion and force was proposed in the 1960s. Japan's Toshiiku Sashida proposed a rotary traveling wave ultrasonic motor (US Patent US 4562374A) in the early 1980s. This type of ultrasonic motor has a large torque and low speed, and is widely used in cameras to drive lens movement to achieve automatic focus. Japan's Seiko Corporation (Seiko) developed a rotating standing wave ultrasonic motor with a diameter of 8mm in 1996, and it was used for vibration timekeeping of watches (A.Iino, K.Suzuki, M.Kasuga, M.Suzuki, T.Yamanaka . Development of self-oscillating ultrasonic micro-motor and its application to a watch. Ultrasonics 38, 54-59, 2000.). By further improving the structure and reducing the size, Seiko developed an ultrasonic motor with a diameter of 4.5mm and a thickness of 2.5mm, and applied it to drive the calendar in watches to simplify the mechanism. The above ultrasonic motors use piezoelectric ceramics to excite the ultrasonic vibration of the stator. During the preparation process, epoxy resin is needed to bond the piezoelectric ceramics and the metal structure to form a stator. It is difficult to further miniaturize and ensure the bonding. quality consistency.

It is possible to further miniaturize the motor by fabricating micro-ultrasonic motors on silicon wafers by micromachining. G.-A.Racine and others prepared ultrasonic micromotors by silicon micromachining [G.-A.Racine, R.Luthier, and N.F.de Rooij, Hybrid ultrasonic micromachined motors, Proceedings of Micro Electro Mechanical Systems, 1993. ], a zinc oxide film material (ZnO film, thickness 4.5 μm) was deposited on one side of the silicon diaphragm (Si, thickness 9.2 μm), and the ZnO/Si composite diaphragm produced bending vibration under the action of voltage. The rotor (with inclined flexible teeth prepared on the rotor) contacts and outputs unidirectional rotational motion. The film preparation method and silicon etching method are used in the preparation process of the stator of the motor. The size of the prepared motor is 6×6×2mm3, the speed is 600rpm, and the torque is 50nNm. P.Muralt and M.-A.Dubois prepared an ultrasonic micromotor with a similar working principle [M.-A.Dubois and P.Muralt, PZT thin film actuated elasticfin micromotor, IEEE Transactions on Ultrasonics, Ferroelectrics, and Frequency Control 45, 1169-1177,1998.], using PZT piezoelectric film material with stronger piezoelectric properties (Pb(Zr,Ti)O3 abbreviated as PZT, thickness 1μm) to replace ZnO material, the size of the silicon diaphragm is 5.2mm in diameter, The thickness is 34μm. The test results show that the vibration of the PZT/Si composite diaphragm is stronger than that of the ZnO/Si composite diaphragm, and the performance of the motor is significantly improved. The output torque is 0.94μNm and the speed is 1020rpm. G.L.Smith and R.Q.Rudy et al prepared a rotary traveling wave ultrasonic micromotor based on PZT/Si composite diaphragm A 188,305-311,2012.R.Q.Rudy,G.L.Smith,D.L.DeVoe,and G.Polcawich,Millimeter-scale traveling wave rotary ultrasonic motors,Journal of Microelectromechanical Systems 24,108-114,2015.] Experiments confirm that the stator can generate a uniform amplitude The traveling wave, the maximum speed can reach 2300rpm. Although the above research work demonstrates the micro-ultrasonic motor based on PZT/Si composite diaphragm, it is difficult to obtain high-quality PZT piezoelectric film (the preparation process of PZT film requires high-temperature heat treatment in an oxygen-containing atmosphere, which is different from the silicon semiconductor process. Incompatibility, and PZT is difficult to control the film performance and consistency due to the complex composition and the volatility of the lead element. In addition, the etching process of the PZT film is also to be studied), and the performance and consistency of the ultrasonic motor are difficult to guarantee.

Contents of the invention

Aiming at the deficiencies in the prior art, the purpose of this utility model is to provide a micro-ultrasonic motor driven by electrostatic force. A stator with a silicon diaphragm-cavity-silicon substrate plate capacitor structure is prepared on a silicon chip, and the electrode between the two electrodes of the plate capacitor is used. The electrostatic attraction excites the ultrasonic resonance of the silicon diaphragm of the motor stator, and outputs the torque through the friction between the stator and the rotor, without using piezoelectric materials, which can improve the performance consistency of the ultrasonic micro-motor.

In order to achieve the above object, a micro-ultrasonic motor driven by electrostatic force of the present utility model includes: a silicon-based stator, a rotor, a bearing and an elastic pre-pressure device, the upper surface of the silicon-based stator is provided with a tooth-shaped protrusion; One end of the rotor is sleeved in the bearing for rotational movement, and the rotor is in contact with the tooth-shaped protrusions of the silicon-based stator; the elastic pre-pressure device applies a pre-pressure to the rotor in the axial direction, so that the rotor and the silicon-based stator A normal pressure is generated between them, and the silicon-based stator generates ultrasonic vibration under the action of a driving voltage, and the tooth-shaped protrusions of the silicon-based stator drive the rotor to rotate through friction.

Preferably, the silicon-based stator is a composite structure, the substrate of which is a low-resistivity silicon wafer, an annular groove is etched on the upper surface of the substrate, and the upper surface of the substrate and the inner surface of the annular groove are covered with carbon dioxide. Silicon insulating layer, a high-resistivity silicon diaphragm is bonded to the upper surface of the substrate and seals the groove to form a vacuum chamber, the upper surface of the high-resistivity silicon diaphragm is provided with the first metal electrode and the tooth-shaped protrusions .

Preferably, a parallel plate capacitor is formed between the base of the silicon-based stator, the vacuum cavity, and the first metal electrode. Under the action of an AC voltage, the electrostatic force that changes between the first metal electrode and the base causes the silicon diaphragm to vibrate. vibration.

Preferably, the annular silicon diaphragm on the vacuum cavity of the silicon-based stator has traveling waves of bending vibration propagating in the circumferential direction, and drives the rotor to rotate through contact friction.

The beneficial effects of the utility model:

The utility model adopts the silicon chip as the base material to prepare the stator of the miniature ultrasonic motor, utilizes the electrostatic force between the two electrodes of the parallel plate capacitor to excite the ultrasonic vibration of the stator structure, and utilizes the mature materials and techniques of the current technical level in the preparation process of the stator, which can The size of the motor is further reduced, and the performance consistency of the motor can be ensured.

Description of drawings

FIG. 1 is a schematic diagram of the structure of the micro-ultrasonic motor driven by electrostatic force of the present invention.

FIG. 2 is an axonometric view of the structure of the silicon-based stator in the present invention.

FIG. 3 is a cross-sectional view of the structure of the silicon-based stator in the present invention.

FIG. 4 is a structural deformation diagram of the third-order bending vibration mode of the free annular part of the silicon diaphragm in the utility model.

Fig. 5 shows the Z-direction displacement nephogram of the third-order bending vibration mode of the free annular part of the silicon diaphragm in the utility model.

Detailed ways

In order to facilitate the understanding of those skilled in the art, the utility model will be further described below in conjunction with the embodiments and accompanying drawings, and the contents mentioned in the implementation modes are not limitations of the utility model.

With reference to shown in Figure 1, a kind of micro-ultrasonic motor 1 driven by electrostatic force of the present utility model comprises: silicon-based stator 2, rotor 3, bearing 4 and elastic pre-pressure device 5, and described silicon-based stator 2 upper surface is provided with a Evenly distributed tooth-shaped protrusions 24; one end of the rotor 3 is sleeved in the bearing 4 for rotational movement, and the rotor 3 is in contact with the tooth-shaped protrusions 24 of the silicon-based stator 2; the elastic pre- The pressure device 5 exerts a pre-pressure F on the rotor 3 in the axial direction, so that a normal pressure is generated between the rotor 3 and the silicon-based stator 2, and the silicon-based stator 2 generates ultrasonic vibration under the action of the driving voltage, and the teeth of the silicon-based stator 2 The protrusion 24 drives the rotor 3 to rotate through friction.

Referring to Figures 2-3, the silicon-based stator 2 is a composite structure, and its base 21 is a low-resistivity silicon wafer. An annular groove is etched on the upper surface of the base 21, and the base is formed by oxidation. Prepare a layer of silicon dioxide (SiO ₂ ) insulating layer 22 on the upper surface and the inner surface of the annular groove, and a high-resistivity silicon diaphragm 23 is bonded to the upper surface of the substrate 21 and seals the groove to form a vacuum cavity. The upper surface of the resistivity silicon diaphragm 23 is provided with the tooth-shaped protrusions 24 and the first metal electrode 25 , and the lower surface of the low-resistivity silicon substrate 21 is provided with a second metal electrode 26 for welding wires. The low-resistivity silicon substrate 21, the vacuum cavity, and the first metal electrode 25 form a parallel plate capacitor, and under the action of an AC voltage, the electrostatic force that changes between the first metal electrode 25 and the substrate 21 causes the high-resistivity silicon Vibration of the free part of the diaphragm 23. The first metal electrode 25 is divided into 12 fan-shaped electrodes 25a, 25b, 25c, 25d, 25e, 25f, 25g, 25h, 25i, 25j, 25k, 25l distributed uniformly along the circumference, and connected to the peripheral 12 pads. The shape of the first metal electrode 25 is set to excite the third-order bending vibration mode of the free part of the high-resistivity silicon diaphragm 23 (the upper annular region of the vacuum cavity) (as shown in FIGS. 4 and 5 ). The frequency f of the AC driving voltage applied to the ultrasonic motor 1 is equal to or close to the natural frequency of the third-order bending vibration mode of the high-resistivity silicon diaphragm 23 The driving voltage is applied in the following manner: the second metal electrode 26 is grounded, and the electrodes 25a, 25b, 25c, 25d...25l apply an AC voltage with a phase increment or decrement of 90° (i.e. respectively apply the voltage V _ac sin (2πft)+V _bias , V _ac cos(2πft)+V _bias , -V _ac sin(2πft)+V _bias , -V _ac cos(2πft)+V _bias ... -V _ac cos(2πft)+V _bias , or V _ac sin(2πft)+V _bias , -V _ac cos(2πft)+V _bias , -V _ac sin(2πft)+V _bias , V _ac cos(2πft)+V _bias ...V _ac cos(2πft)+V _bias , where V _bias is the bias voltage), there will be bending vibration traveling waves propagating clockwise or counterclockwise in the free annular part of the high-resistivity silicon diaphragm 23, and the silicon-based stator 2 will drive the rotor 3 counterclockwise through contact friction clockwise or clockwise.

There are many specific application ways of the utility model, and the above descriptions are only the preferred implementation modes of the utility model. Improvements, these improvements should also be regarded as the protection scope of the present utility model.

Claims (4)

1. A micro-ultrasonic motor driven by electrostatic force, it is characterized in that, comprising: a silicon-based stator, a rotor, a bearing and an elastic preloading device, the upper surface of the silicon-based stator is provided with a toothed protrusion; one end of the rotor Sleeved in the bearing for rotating movement, the rotor is in contact with the tooth-shaped protrusions of the silicon-based stator; the elastic pre-pressure device applies a pre-pressure to the rotor in the axial direction, so that the rotor and the silicon-based stator produce a The silicon-based stator generates ultrasonic vibration under the action of the driving voltage, and the tooth-shaped protrusions of the silicon-based stator drive the rotor to rotate through friction. 2. The micro-ultrasonic motor driven by electrostatic force according to claim 1, characterized in that, the silicon-based stator is a composite structure, and its base is a low-resistivity silicon chip, and the upper surface of the base is etched a An annular groove, the upper surface of the substrate and the inner surface of the annular groove are covered with a silicon dioxide insulating layer, and a high-resistivity silicon diaphragm is bonded to the upper surface of the substrate and seals the groove to form a vacuum chamber. The high-resistivity silicon membrane The upper surface of the chip is provided with the first metal electrode and the tooth-shaped protrusions. 3. The micro-ultrasonic motor driven by electrostatic force according to claim 2, characterized in that, a parallel plate capacitor is formed between the base of the silicon-based stator, the vacuum cavity, and the first metal electrode, and under the action of alternating voltage, The changing electrostatic force between the first metal electrode and the substrate causes the silicon diaphragm to vibrate. 4. The micro-ultrasonic motor driven by electrostatic force according to claim 2, characterized in that, there is a traveling wave of bending vibration propagating in the circumferential direction in the annular silicon diaphragm on the vacuum chamber of the silicon-based stator, through contact Friction drives the rotor to rotate.