CN103029440B - Piezoelectric ultrasonic drive liquid ejection device - Google Patents

Abstract

The invention provides a piezoelectric ultrasonic-driven liquid injection device, which includes a vibrator, a connecting screw, a horn, a piezoelectric ceramic sheet, an annular copper electrode, a compression screw, a compression ring, a compression washer and a container; The screw is concentrically connected with one end of the vibrator, and the center of the other end of the vibrator is processed with a threaded hole. The compression nut and the center hole of the end face of the vibrator are connected through threads. The compression nut presses the piezoelectric ceramic vibration unit on the end of the vibrator through a compression washer. The container and The pressure ring is fixed on the vibrator node flange through the screw rod. The present invention is different from piezoelectric ceramic pumps such as cavity type, peristaltic type and traveling wave type in the past, as well as centrifugal liquid pumps and piston-type injection devices. The end of the rod is projected outward, suitable for high-frequency vibration mode drive. The invention has certain applications in the fields of chemistry, medicine, inkjet printing, fountains and the like.

Description

A Piezoelectric Ultrasonic Driven Liquid Injection Device

technical field

The invention belongs to the technical field of liquid pumps in precision machinery, and relates to an ultrasonic piezoelectric-driven liquid injection device that uses high-frequency vibration inertial force to eject liquid, and particularly relates to the specific structural design and piezoelectric driving method of the device.

Background technique

Liquid delivery devices based on piezoelectric actuation mainly include piezoelectric actuation liquid injection devices and piezoelectric ceramic liquid pumps. The traditional piezoelectric actuated liquid injection device is mainly a piston structure, including a piezoelectric drive structure, a piston mechanism, and a micro outlet orifice. Under the action of the electric field, the expansion and contraction deformation of the piezoelectric ceramic driving structure makes the piston mechanism move back and forth, thereby causing the volume of the cavity to change, and driving the liquid to be ejected from the micro-outlet orifice. However, due to the small driving displacement of piezoelectric ceramics under the action of an electric field, the volume change of the cavity is also small, and the liquid flow rate of a single injection is small. To make the liquid have a certain injection flow rate, the micro-outlet orifice must be sufficiently large. At the same time, the sealing requirements of the piston mechanism are also correspondingly increased, which increases the difficulty of manufacturing the device. In addition, due to the structural characteristics of the piston, the piston generally moves at a low frequency, and the amount of liquid pumped per unit time is limited, and the efficiency is low. Therefore, the traditional piezoelectric liquid ejection device is generally used in the occasion of quantitative delivery of trace liquid.

The pump body of a traditional piezoelectric ceramic fluid pump is mainly composed of a shell surface, a cavity, an inlet and an outlet, and the shell surface is generally a piezoelectric ceramic actuator plate bonded with a metal elastic sheet. Ceramic laminate construction. Under the action of an electric field, the expansion and contraction deformation of the piezoelectric ceramic actuator plate causes the piezoelectric ceramic laminate to produce bending deformation, thereby causing the volume change of the cavity, so that the liquid in the inlet and outlet ports forms during the volume change of the cavity. Movement in and out of the cavity. In order to allow the liquid to flow in a certain direction, a basic approach is to add a check valve device at the inlet and outlet of the pump. When the volume of the cavity expands, the inlet valve opens and the outlet valve closes; when the volume of the cavity shrinks, the inlet valve closes and the outlet valve opens, so as to force the liquid to flow in a specific direction the goal of. In order to improve the operating efficiency of the pump, it is generally hoped that the driving voltage frequency of the piezoelectric ceramic pump is the resonant frequency of the cavity structure. At this time, the volume change of the cavity is much larger than other states, and the output power also reaches the maximum value. However, for cavity-type piezoelectric ceramic pumps, the resonance frequency of the piezoelectric ceramic laminate is generally above several hundred Hz; The vibration of the shell surface of the pump is matched to realize the simultaneous opening and closing of hundreds of times per second. Under such restrictive conditions, the performance of cavity-type piezoelectric ceramic pumps at high frequencies is not outstanding, and the best operating frequency is generally below 100 Hz, so its efficiency has not been fully utilized. Although the new one-way valve manufactured by MEMS technology has excellent high-frequency characteristics, this technology is still in the research stage, and the MEMS manufacturing process is complicated and the cost is high, so it is not realistic to promote it for practical use. Some novel valveless piezoelectric ceramic pumps using special inlet and outlet structures, such as V-shaped nozzles, three-way nozzles, variable flow resistance tube nozzles and other inlet and outlet structures, although their structural performance is affected by the frequency The influence is small, so that the cavity piezoelectric ceramic pump using this type of inlet and outlet structure is suitable for working at a higher frequency, but because the mechanism of these inlet and outlet structures is mainly to use the liquid to reciprocate through the inlet and outlet in a single cycle The difference in the flow rate realizes the overall unidirectional flow, so it is not a unidirectional flow in a complete sense. The volume change of the piezoelectric ceramic cavity cannot be fully utilized, and the actual characteristic parameters such as the flow rate and hydraulic pressure of the piezoelectric ceramic pump No substantial improvement has been achieved. Some new piezoelectric pumps that have appeared in recent years, such as peristaltic pumps using a continuous series piezoelectric ceramic cavity structure, adjust the phase relationship between the periodic volume changes between piezoelectric ceramic cavities, so that there is no need for unidirectional pumps. Under the conditions of valve or special inlet and outlet structure, the one-way flow of liquid can be realized; the driving form of piezoelectric pump made by traveling wave principle is similar to that of traveling wave motor, and the elastic layer is driven by the vibration of piezoelectric ceramic unit. Traveling wave fluctuations are generated to provide a driving force in a certain direction for the liquid on the elastic layer to realize flow. Although the performance of these new piezoelectric ceramic pumps has been improved, the structure and control methods tend to be complicated; Electroceramic pumps, whose piezoelectric ceramics produce telescopic deformation under a certain excitation drive, realize metal tube vibration and drive liquid flow. The pump has a simple structure, is easy to control, and is suitable for high-frequency drive. It is not easy to control the direction of liquid flow during vibration.

The various types of piezoelectric ceramic pumps mentioned above include different piezoelectric ceramic drive forms and pump body structures. Although each has certain advantages, the overall performance of each structure is not ideal. The improvement of piezoelectric ceramic pumps And the invention of the new piezoelectric ceramic pump is of great significance.

Contents of the invention

In order to obtain an ideal piezoelectric liquid delivery device and overcome some problems existing in existing piezoelectric ceramic pumps, an ultrasonic piezoelectric-driven liquid injection device that uses the inertial force generated by high-frequency vibration to eject the liquid is proposed. It has the advantages of simple structure, good reliability, convenient control, long range and suitable for high-frequency drive.

The technical solution adopted in the present invention: a piezoelectric ultrasonic-driven liquid injection device, including a horn, a container, a connecting screw, a compression ring, a vibrator, a compression screw, an annular copper electrode, a compression washer and a piezoelectric ceramic vibration unit; The horn is concentrically connected with one end of the vibrator through the connecting screw, and the center of the end face of the other end of the vibrator is processed with a threaded hole. The compression screw is connected with the threaded hole in the center of the end face of the vibrator through threads, and the compression washer and the piezoelectric ceramic vibration unit are ring-shaped. The compression screw presses the piezoelectric ceramic vibration unit in series on the end of the vibrator through the compression washer, and the container and the compression ring are fixed on the flange of the vibrator node through the screw; wherein, the piezoelectric ceramic vibration unit includes a piezoelectric ceramic sheet and a ring Copper electrodes, the piezoelectric ceramic sheet is installed opposite to the end surface of the piezoelectric ceramic sheet, the annular copper electrode is installed on both sides of the end surface of the piezoelectric ceramic sheet, the piezoelectric ceramic sheet and the annular copper electrode are installed in series at intervals, and are compressed on the end of the vibrator by a compression screw; Ring-shaped copper electrodes of the same polarity are connected in series.

The horn must be designed according to the requirements of the pure axial vibration mode of the overall structure of the device, and its structure can be designed as a stepped, conical, catenary or exponential structure.

The vibrator structure needs to be designed according to the requirements of pure axial vibration mode for the overall structure of the device.

The horn can be designed as an independent structure, or can be designed as a horn with an integrated structure with the vibrator.

The piezoelectric ceramic sheet adopts a ring structure, the outer diameter is the same as that of the vibrator, electrodes are plated on both ends, the thickness is 0.2-10 mm, and the number is 2n, where n is a natural number.

The shape of the annular copper electrode is the same as that of the piezoelectric ceramic sheet, and the thickness is 0.01-1 mm.

The container connects the pressure ring to the vibrator node flange through a screw rod and a nut.

The container is installed on the vibration node flange of the vibrator, and its structure can be designed according to different installation occasions and realized functions.

Design idea of the present invention:

The piezoelectric ultrasonic liquid injection device of the present invention, the piezoelectric ceramic vibration unit generates stretching vibration under the excitation of a certain signal, the vibration is amplified and transmitted to the horn through the vibrator, and the horn is immersed in a certain distance under the liquid surface, and the specially designed variable When the horn is excited at a certain frequency, the free end generates pure axial vibration, and the high-frequency vibration throws the liquid on the end surface of the horn.

The advantage of the present invention compared with prior art is:

The piezoelectric ultrasonic liquid injection device of the present invention utilizes the vibration amplification principle of the horn, and can utilize different pump body structures and driving frequencies to realize the pure axial stretching vibration of the horn and eject the liquid. For different driving frequency schemes, the structure of the horn and the vibrator is different, and the number of piezoelectric ceramic pieces required may also be different. The structure of the horn and the vibrator can be integrated or separated. For different applications, the structure of the pump can also be different.

Description of drawings

Fig. 1 is a front sectional view of a piezoelectric ultrasonic liquid ejecting device of the present invention. Label names in the figure: 1 is the horn, 2 is the container, 3 is the connecting screw, 4 is the pressure ring, 5 is the vibrator, 6 is the pressure screw, 7 is the ring copper electrode, 8 is the pressure washer, 9 is the pressure Electric ceramic sheet, 10 is a nut, and 11 is a screw rod.

Figure 2 shows the integral structure of the horn and the vibrator, and the outer contour of the horn is an exponential function.

Figure 3 shows the stage conical horn, that is, the outer contour of the horn part is conical.

Fig. 4 is a front sectional view of a self-balancing piezoelectric ultrasonic liquid ejection device. Label name among the figure: 12 is container.

Detailed ways

The present invention will be further described below in conjunction with the accompanying drawings and specific embodiments.

Embodiment 1: A piezoelectric ultrasonic-driven liquid injection device, including a horn 1, a container 2, a connecting screw 3, a pressure ring 4, a vibrator 5, a compression screw 6, an annular copper electrode 7, a compression washer 8 and a compression ring. Electric ceramic vibration unit; the horn 1 is concentrically connected with one end of the vibrator 5 through the connecting screw 3, the center of the other end of the vibrator 5 is processed with a threaded hole, the compression screw 6 is connected with the center hole of the end face of the vibrator 5 through threads, the compression washer 8 is connected with the pressure The electric ceramic vibration unit is ring-shaped, and the compression screw 6 presses the piezoelectric ceramic vibration unit in series on the end of the vibrator 5 through the compression washer 8. The piezoelectric ceramic vibration unit is composed of a piezoelectric ceramic sheet 9 and an annular copper electrode 7. The container 2 It is connected to the vibrator 5 node flange through the pressure ring 4.

The structure of the present invention is different from piezoelectric ceramic pumps such as cavity type, peristaltic type, and traveling wave type in the past, as well as centrifugal liquid pumps and piston-type injection devices, and does not need valves to control the flow of liquid and input and output ports with special structures. Projected outwards through the end of the horn, suitable for high frequency vibration form drive.

The piezoelectric ceramic vibration unit is composed of multiple piezoelectric ceramic sheets 9 and annular copper electrodes 7, the annular copper electrodes 7 and the piezoelectric ceramic sheets 9 are stacked at intervals, and the electrodes are connected with the same pole. The electroceramic vibrating unit has a ring structure and is strung on the compression screw 6. The compression screw 6 passes through the compression washer 8 and the piezoelectric ceramic vibration unit to compress it with the end face of the vibrator 5; the container 2 is used to hold the liquid , the end face of the vibrator 5 is submerged under the liquid surface; the pressure ring 4 fixes the container 2 on the vibration node flange of the vibrator 5 .

The piezoelectric ceramic sheet 9 of the piezoelectric ceramic vibration unit adopts a ring-shaped structure; the piezoelectric ceramic sheet 9 used can be made of lead zirconate titanate piezoelectric ceramics or lead-free piezoelectric ceramic materials.

The structure of the vibrator 5 is specially designed according to the vibration mode of the rod, and the centers of the two end faces are respectively processed with threaded holes. According to the vibration and wave transmission theory, the vibrator is modeled in ANSYS finite element analysis software, and the modal analysis and structural parameter optimization design are carried out. In this example, the vibrator material is aluminum alloy. First, the vibration mode of the piezoelectric vibrator is analyzed based on the piezoelectric equation. In this example, the thickness of the piezoelectric ceramic is 2mm, the outer diameter is Ф15.84mm, the inner diameter is Ф6mm, and 4 pieces of the same pole are installed opposite to each other; the annular copper electrode is 0.08mm thick, the shape is consistent with the piezoelectric ceramic, and it is installed at intervals with the piezoelectric sheet; in ANSYS The assembly structure model of piezoelectric ceramic sheet, ring-shaped copper electrode, compression washer, compression screw is established in the software, and the vibration mode analysis of the piezoelectric vibration unit is carried out, and the pure axial vibration frequency of the piezoelectric vibration unit is about 55.9kHz . Second, determine the structural parameters of the vibrator. The structural parameters of the vibrator mainly include: outer diameters D ₁ , D ₄ , D ₅ , D ₆ and rod lengths l ₁ , l ₂ , l ₃ , as shown in Figure 2. Among them, take D ₆ =15.84mm, which is the same as the outer diameter of the piezoelectric sheet; the length of the rod is taken as half of the ultrasonic length, and the ultrasonic length can be obtained from theoretical calculations as 90mm, and l ₂ =2l ₁ =2l ₃ =45mm. In the finite element analysis software ANSYS, the model is established with the stepped shaft structure and the vibration unit, with D ₁ , D ₄ , and D ₅ as parameters, and the mode shape of the overall structure doing pure axial vibration at a frequency of about 55.9kHz as the objective function. By optimizing the structural parameters of the vibrator, D ₁ =6.35mm, D ₄ =11.95mm, and D ₅ =11.43 can be obtained. Considering that the abrupt change from D ₄ to D ₁ will cause excessive stress concentration, take D ₃ =10.5mm, and the transition arc radius is 20mm, so that the vibrator structure shown in Figure 2 can be determined. The structural parameters of the vibrator obtained by the optimal design are analyzed in the ANSYS software and the vibration unit for the overall vibration mode, and the vibration frequency of the pure axial vibration mode is 55.6kHz.

The structure of the horn 1 described above is specially designed according to the vibration mode, and one end is processed with a threaded hole. Taking the exponential horn as an example, when the shape of the vibrator is determined, the overall device composed of the vibrator and the like is required to be in a certain position. When the vibration frequency is pure axial vibration, the material is titanium alloy. The exponential section curve function is: D=D1·e ^-2βx , where 0<x<l, D is the diameter of the exponential section, D ₁ is the diameter of the large end, D ₂ is the diameter of the end, l is the length of the horn, the structural parameters are shown in Figure 2, and can be changed by changing D ₁ , D ₂ and The size of l changes the resonant frequency of the vibrator. In this example, the length of the horn is taken as half-wave l=45mm; the initial value of the diameter of the large end is D ₁ =6.35mm, which is the same as the diameter of the vibrator; according to the design theory of the horn, modeled in ANSYS software, the vibrator and the The resonant frequency of the pure axial vibration of the beam is the objective function, and the modal analysis and parameter optimization are carried out in the finite element analysis software, when the frequency and mode shape meet the overall design requirements. According to software analysis, the mode shape of the overall structure of the horn, vibrator and vibration unit at a frequency of 55.5KHz is pure axial vibration, and the structural dimensions of the horn are l=45mm, D ₁ =6.36mm, D ₂ =1.26mm .

The ring-shaped copper electrode 7 has a thickness of 0.01-1 mm, and the shape is the same as that of the piezoelectric ceramic sheet 9 .

The structure of the compression screw 6 is designed according to the size of the inner hole of the piezoelectric ceramic sheet 9 and the number of sheets, and the thread is a standard thread, which is made of titanium alloy material.

The container 2 is used to hold the liquid with the pump to ensure that the liquid level exceeds a certain distance from the end surface of the horn 1. The shape and size of the container 2 vary according to the application occasion and installation conditions, and can be made of metal or plastic materials.

One end surface of the compression washer 8 has the same shape as the piezoelectric ceramic sheet 9, and the other end surface has a large chamfer in the inner hole, which is made of metal materials such as stainless steel.

Further, the container 2 connects the pressure ring 4 to the node flange of the vibrator 5 through the screw rod 11 and the nut 10 . The screw rod 11 and the nut 10 are standard parts. The fixed part of the container 2 is sealed.

The number of piezoelectric ceramic sheets is 4, as shown in Figure 1, after a certain frequency of periodic excitation signal is applied, the piezoelectric ceramic sheets are stretched and deformed along the axial direction, and the vibrator amplifies the axial vibration and transmits it to the horn. The rod amplifies the vibration and performs pure axial vibration, and the inertial force of the vibration of the horn ejects the liquid on its end surface out of the container to realize liquid transportation.

For the piezoelectric ultrasonic liquid injection device of the present invention, there are also some specially designed links, which are summarized as follows:

1) Since the liquid is only immersed in the end of the horn, the vibration inertia force of the end of the horn can eject the liquid on the end, but if the liquid level is too high, due to the resistance between the liquids, the horn will The liquid at the end cannot be thrown out of the liquid surface due to the resistance between the liquids. Therefore, the piezoelectric ultrasonic spraying device of the present invention must make the liquid level higher than the end surface of the horn by about 0.5~3mm, so that the liquid will not be hindered by the liquid resistance. Shot out while also having enough liquid at the end of the horn for continuous throwing.

2) The vibrator and the horn in the piezoelectric ultrasonic injection device of the present invention can be made into a separate structure as shown in Figure 1, or can be made into an integral structure as shown in Figure 2, and its structure needs to be based on the vibration of the entire pump body. Modal design, that is, the structure of the horn must meet the pure axial vibration mode of the overall structure of the pump.

3) The vibration unit of the piezoelectric ceramic sheet in the piezoelectric ultrasonic injection device of the present invention is axially polarized, and multiple sheets are connected to the same pole when installed in series, and the number is 2n, where n is a natural number.

4) The excitation signal of the piezoelectric ultrasonic injection device of the present invention is a periodic signal. The excitation signal can be a sinusoidal signal, a triangular signal or a rectangular signal, and the signal frequency must meet the vibration frequency of the pure axial vibration mode of the overall structure of the pump.

Embodiment 2: The number of piezoelectric ceramic sheets is 6, and the vibrator and the horn are made into a whole horn. Its structure is shown in Figure 2. After a periodic excitation signal is applied, the piezoelectric ceramic sheets expand and contract along the axial direction Deformation, the horn amplifies the vibration and performs pure axial vibration, and the inertial force of the horn vibration ejects the liquid on its end face out of the container to realize liquid transportation.

Other structures are with embodiment 1.

Example 3: The number of piezoelectric ceramic sheets is 4, and the radial size of the container is relatively large. As shown in Figure 4, after a periodic excitation signal is applied, the piezoelectric ceramic sheets are stretched and deformed along the axial direction, and the horn amplifies the vibration and makes Pure axial vibration, the inertial force of the vibration of the horn throws the liquid on its end surface out of the container, the liquid is thrown to a certain height and then falls into the container due to the action of gravity, the liquid level in the container always maintains a certain height, and so on Circulation is formed, and the liquid does not need to be replenished.

Other structures are with embodiment 1.

The structure of the present invention is different from piezoelectric ceramic pumps such as cavity type, peristaltic type and traveling wave type in the past, and does not require valves to control the flow direction of liquid or input and output ports with special structures, nor does it require complicated piezoelectric ceramic vibration units and drivers. circuit, suitable for high-frequency vibration forms. The invention has certain application prospects in the fields of medicine, chemistry, inkjet printing, fountain decoration and the like.

The parts not described in detail in the present invention belong to the well-known technology in the art.

Claims (7)

1. a piezoelectric ultrasonic drive liquid ejection device, is characterized in that: comprise ultrasonic transformer (1), container (2), joint bolt (3), pressure ring (4), oscillator (5), clamping screw (6), packing washer (8) and piezoelectric ceramic vibrator moving cell; Ultrasonic transformer (1) is connected with oscillator (5) one end is concentric by joint bolt (3), oscillator (5) other end end face center is processed with screwed hole, clamping screw (6) passes through thread connection with the described end face screwed hole of centre of oscillator (5), packing washer (8) and piezoelectric ceramic vibrator moving cell are annular, piezoelectric ceramic vibration unit strings is pressed in oscillator (5) end by packing washer (8) by clamping screw (6), and container (2) and pressure ring (4) are fixed on oscillator node flange by screw rod; Wherein, described piezoelectric ceramic vibrator moving cell comprises piezoelectric ceramic piece (9) and annular copper electrode (7), described piezoelectric ceramic piece (9) homopolarity end face is mounted opposite, annular copper electrode (7) is arranged on piezoelectric ceramic piece (9) end face both sides, and piezoelectric ceramic piece (9) and annular copper electrode (7) are installed in series and use clamping screw (6) to be pressed on oscillator end; The annular copper electrode (7) of same polarity is connected in series mutually.

2. piezoelectric ultrasonic drive liquid ejection device according to claim 1, it is characterized in that: described ultrasonic transformer must do the requirement design of pure axial vibration mode according to device overall structure, its structure is designed to notch cuttype, taper shape, stretched wire type or exponential type structure.

3. piezoelectric ultrasonic drive liquid ejection device according to claim 1 and 2, is characterized in that: described oscillator structure need do the requirement design of pure axial vibration mode according to device overall structure.

4. piezoelectric ultrasonic drive liquid ejection device according to claim 1, is characterized in that: described piezoelectric ceramic piece adopts loop configuration, and external diameter is identical with oscillator external diameter, and both ends of the surface are coated with electrode, and thickness is 0.2 ~ 10mm, and quantity is 2n, n is natural number.

5. the piezoelectric ultrasonic drive liquid ejection device according to claim 1 or 4, is characterized in that: described annular copper electrode shape is identical with piezoelectric ceramic piece, and thickness is 0.01 ~ 1mm.

6. the piezoelectric ultrasonic drive liquid ejection device according to claim 1 or 4, it is characterized in that: pressure ring (4) is connected on oscillator (5) node flange by screw rod (11) and nut (10) by container (2), and described screw rod (11) and nut (10) are standard component.

7. piezoelectric ultrasonic drive liquid ejection device according to claim 1 and 2, is characterized in that: described container is arranged on oscillator vibration node flange, and its structure can design according to installation occasion and the different of practical function.