Yong Liu

The Structure of Wheel Check Valve Influence on Air Block Phenomenon of Piezoelectric Micro-Pump

To improve the stability and reliability of the piezoelectric micro-pump, the cause of air block phenomenon is analyzed on the structure of wheel check valve. During the movement of the bubble in the micro-channel, pressure drop occurs, the main factor which influences the bubble going through is opening height of the wheel check valve. Five groups of wheel check valves with different structures are used to test the wheel check valve opening height and air block probability. The experiment results show that reducing the wheel check valve thickness or diameter ratio can both increase the wheel check valve opening height, and decrease the air block probability. Through experiment, the optimum combination of the wheel check valve structure is obtained within the samples: as the thickness is 0.02 mm, the diameter ratio is 1.2, the wheel check valve opening height gets 252 µm, and within the given bubble volume, the air block probability is less than 2%.

Experiment on dual-chamber parallel piezoelectric stack pump for electrorheological fluids

In order to achieve the accurate delivery for electro rheological (ER) fluids, dual chamber parallel piezoelectric stack pump (PESP) is designed. Firstly, working principle of dual chamber parallel PESP is analyzed, and its output performance is discussed in different working modes. Next, based on the characteristic of piezoelectric stack that the output pressure is large but the volume change is little, a new passive check valve is designed. According to finite element analysis of flow field in chamber, asymmetric flow channel is adopted. Finally, the prototype pump is manufactured, and the output performance is tested in both synchronous mode and asynchronous mode. As is shown in the experimental result, comparing with single chamber pump, dual chamber parallel piezoelectric stack pump cannot improve output pressure, but it can raise the output flow rate. In synchronous mode, the output flow rate of dual chamber has been increased to twice as compared with single chamber, but pulsation is large, while in asynchronous mode the output flow rate of dual chamber has been increased to three times as compared with single chamber and pulsation is little.

A normally-closed piezoelectric micro-valve with flexible stopper

In the field of controlled drug delivery system, there are still many problems on those reported micro-valves, such as the small opening height, unsatisfactory particle tolerance and high cost. To solve the above problems, a novel normally-closed piezoelectric micro-valve is presented in this paper. The micro-valve was driven by circular unimorph piezoelectric vibrator and natural rubber membrane with high elasticity was used as the valve stopper. The small axial displacement of piezoelectric vibrator can be converted into a large stroke of valve stopper based on hydraulic amplification mechanism. The experiment indicates that maximum hydraulic amplification ratio is up to 14, and the cut-off pressure of the micro-valve is 39kPa in the case of no working voltage. The presented micro valve has a large flow control range (ranging from 0 to 8.75mL/min).

Structural Design and Experimental Analysis of a Piezoelectric Vibration Feeder with a Magnetic Spring

A piezoelectric vibration feeder with a magnetic spring is discussed in this paper. The feeder can keep resonance frequency relatively stable under changing loading. Through the analysis on the working principle and magnetic spring stiffness characteristic of this feeder, the dynamic model was established and the relationship among system resonance frequency, loading and magnetic spring stiffness was obtained. The analysis showed that, as the loading changed, the magnetic spring stiffness changed accordingly, which maintained a trend of stability in the system resonance frequency. A prototype was made for the experiment, and the relationship among the loading, magnetic spring axial clearance and system resonance frequency was obtained. The result showed that, when the loading changes, the resonance frequency and feeding speed tended to be stable, which matched the theoretical analysis. Through comparison with a traditional vibration feeder, within nominal loading, this new feeder has more stable resonance frequency and feeding speed.

The effect of surface wettability on the performance of a piezoelectric membrane pump

In this paper, we studied the effect of surface wettability on the bubble tolerance of a piezoelectric membrane pump, by applying the super-hydrophilic or super-hydrophobic surface to the key elements on the pump. Wettability for the flow passage surface has a direct influence on the air bubbles flowing in the fluid. Based on the existing research results, we first analyzed the relationship between the flow passage surface of the piezoelectric pump and the bubbles in the fluid. Then we made three prototypes where pump chamber walls and valve plate surfaces were given different wettability treatments. After the output performance test, results demonstrate that giving super-hydrophilic treatment on the surface of key elements can improve the bubble tolerance of piezoelectric pump; in contrast, giving super-hydrophobic treatment will reduce the bubble tolerance.

A Resonant Piezoelectric Diaphragm Pump Transferring Gas with Compact Structure

In order to improve the output capacity of a piezoelectric pump when transferring gas, this paper presents a compact resonant piezoelectric diaphragm pump (hereinafter referred to as the piezoelectric diaphragm pump), which is driven by a rectangular piezoelectric vibrator. The compact structure can effectively release the vibrating constraints of the vibrator, and enlarge its center output displacement, so as to increase the volume change rate of the pump chamber. Based on the structure and the working principle of this piezoelectric diaphragm pump, a dynamic model for the diaphragm system is established in this paper, and an analysis on factors affecting the resonant frequency of the system is then conducted. We tested on the prototype under the driving voltage of 260 Vpp. The results show that the diaphragm system reaches resonance under the driving frequency of 265 Hz, which is very close to the fundamental frequency of check valve. Compared with the rectangular piezoelectric vibrator’s amplitude, the diaphragm’s amplitude is double amplified. At this time, the piezoelectric diaphragm pump achieves the maximum gas flow rate as 186.8 mL/min and the maximum output pressure as 56.7 kPa.

The Experimental Study on the Influence Factors in Adhesive Dispensing Dot Diameter of Impact Jetting Valve

To obtain much higher accurate jetting dispensing, an investigation on a jetting valve with ball needle and conical nozzle is done in this paper. The theoretical model on the relationship among needle, nozzle, and adhesive during the impact process is established first. The experiments are done on a jetting valve prototype, and the results show that there are two factors that influence the ball needle impact speed: the spring compression and the impact stroke. The spring compression has little influence on the dispensing dot diameter from jetting, while the impact stroke greatly influences the dispensing dot diameter. Within a certain range, the dispensing dot diameter increases with stroke until the impact stroke reaches a certain value, then the dispensing dot diameter remains stable. Besides, when the nozzle structure stays the same, increasing the ball diameter of the needle will also increase the dispensing dot. The experimental result matches the theoretical model well. After the needle structure and impact parameter optimization on the prototype, the dispensing diameter can achieve Φ0.22 mm, while the jetting viscosity is 1200 cps, the nozzle diameter Φ0.06 mm, impact needle diameter Φ1.5 mm, and stroke 0.06 mm. Therefore, the investigation, in this paper, can be used as the design basis for a high-accuracy jetting valve.

Design of a New Piezoelectric Vibrating Feeder

With two upper and nether piezoelectric vibrators to provide excitation in the same time, vertical double driven piezoelectric feeder (vertical double driven feeder for short in the paper) has smaller piezoelectric ceramics (PZT), and lower driving voltage to prolong the lifetime of the PZT, meanwhile, its carrying capacity gets stronger, compared with vertical single driven piezoelectric feeder (vertical single driven feeder for short in the paper). Vibration analysis was carried out on the feeder system, and the affection factors on the system natural frequency and feeder tray amplitude were received. Based on the modal analysis, the system theoretical resonant frequency was got as 135.95Hz. In the end, the prototype was tested to analyze the relationships among the feeding speed, feeder tray amplitude, driving voltage and driving frequency.

Theoretical Analysis & Experimental Research on Piezoelectric Vibration Feeder by Vertical Driving

The Present Electromagnetic/piezoelectric Vibration Feeder can’t be Compressed along the Height Direction, and the Application is Limited because of the Small Assembly Area. Therefore, a New Structure Piezoelectric Vibration Feeder was Brought up in this Paper, which had Cirque Piezoelectric Vibrator for Vertical Driving, and the Dimension of the Height can be Reduced to below 30% of the Present Feeder. Based on the Structure Character of the Feeder, the Vibration Model was Built up, and the Calculation Method of the System Resonance Frequency, the Stiffness Matching Relationship of the Supporting Spring and Piezoelectric Vibrator were Confirmed through Theoretical Analysis and Experimental Research. Experiments were Done to the Prototypes, which Turned out that, under the Sine Voltage of 220V, the Feeder could have 0.5kg Stuff for Experiment (samples), which were Columns with Dimension Φ3mm×5mm, and the Feeding Speed can be up to 145mm/s. the Measured Resonance Frequency was 187Hz, which had High Coherency with Theoretical Calculation Value.

Simulation Analysis on Sucking Process Outflow Phenomenon in Piezoelectric Pump

: The author has found the sucking process outflow phenomenon existing in piezoelectric pump during the outflow experiment. To explain the reason of outflow in sucking process, the fluid-structure interaction model of piezoelectric vibrator, fluid and check valve is founded. The simulation analysis turns out that the pump chamber pressure increases sharply in the later of sucking process because of the flow inertia, which is the root cause of sucking process outflow. The output flow should include two part, bulk flow and inertial flow, which will provide theoretical reference to piezoelectric pump outflow control.