Research On Piezoelectric Pump With Active Valve Drived By Round Piezoelectric Actuator And Piezoelectric-stack

The piezoelectric pump, using the deflection of piezoelectric diaphragm (PZT actuator) to transmit fluid, is a new-type fluidic device. Compared to the traditional pump, the piezoelectric pump has simple structure, small volume, light weight and weak noise. Compared to the other micro-pumps, the piezoelectric pump consumes small energy, isn't effected by electromagnetism, ease to be control and achieve miniaturization. At present, the research on piezoelectric pump is mainly focusing on the piezoelectric pump with passive valve. With the work frequency of the piezoelectric pump enhanced, the hysteresis of passive valve become pivotal factor affected the performance of piezoelectric pump. So, people design the piezoelectric pump with active valve.1. Analysis and experiments on the piezoelectric bimorphThe piezoelectric bimorph is the key part of the pump, so to find out its structure and working characters has the very important significance on improving the output performance of the pumps. The piezoelectric bimorph is made by bonding a piezoelectric element to one side of a passive elastic plate. It makes use of the piezoelectric material's reverse piezoelectric effect to transform the electric signal into the machine displacement, and engender oscillating of the whole piezoelectric actuator.By using the sheet vibration theory and the related piezoelectric knowledge,the vibration equation of the PZT bimorph is educed, and the central displacementformula is worked out.The experiments on the distortion of the piezoelectric bimorph show that the distortion of piezoelectric bimorph and the driving voltage present the linear relation, so adjusting the driving voltage can obtain the required distortion. Moreover, the distortion of piezoelectric bimorph can also be influenced by the actuated frequency and the shape of the driving signal. With different actuated signals, the distortions of piezoelectric bimorph are different as well. Comparing the three shape of the actuated signal, the sine wave gains the biggest distortion and the triangular wave gains the smallest distortion. Given the different actuated frequencies, the distortions of piezoelectric bimorph have remarkable distinction. Load also influences the distortion greatly. Without load, there is favorable linear relation between the distortions of piezoelectric bimorph and the actuated frequency; with load, there is the optimal corresponding point between the distortions of PZT actuator and the actuated frequency.2. The research on the characteristics of active valveIn this paper, the piezoelectric bimorph and piezoelectric-stack are selected respectively as actuated element of active valve, and two active valves are designed and fabricated. Also, static characteristic and dynamic characteristic of the two active valves are tested. The experiments show that the two active valve can all statisfy generally the requirement of piezoelectric pump, and general performance of active valve using piezoelectric bimorph is better. Because of high requirement on processing precision and assembly size, performance of active valve drived by piezoelectric-stack isn't displayed sufficiently.3. The design and theory of the piezoelectric pump with active valveFrom the structure optimization design angle,we propose the structure of the piezoelectric pump with the PZT actuated active valve. Through testing andresearching on the performance of the pumps, the optimal structure is selected.The piezoelectric pump belongs to micro-pump, and there are a lot of factors affected its output capability such as geometry parameters of actuator and position of the valve holes. To pump cavity height, there is the optimal height; to liquid fluid way, using the axial fluid way is favorable to improve output capability of the piezoelectric pump, and the output flux increases with valve hole diameter largen.4. The experiment and conclusion on the piezoelectric pump with active valve drived by round piezoelectric actuatorDesign and make the piezoelectric pump with active valve by myself. Through altering cavity height and valve hole diameter, performance of piezoelectric pump is tested and investigated, the factors of affecting performance of piezoelectric pump are analyzed. The conclusions are as follows:1. The outputs of the piezoelectric pump with active valve are different with different driving signals imposed on the piezoelectric bimorph. Experiments show that output performance of the pump is best with sine wave and is worst with triangular wave at the same voltage. Moreover, to achieve the optimal work status of the pump, phase difference between driving signal of actuated vibrator and valve vibrator must be selected correctly. Through the theoretical analysis and research, driving signal phase of import valve vibrator should be aheadπ/2 of that of actuated vibrator, and driving signal phase of export valve vibrator should dropπ/2 behind of that of actuated vibrator.2. To the piezoelectric pump with active valve, the relation between its output pressure and flux rate and actuated voltage is linear relation. In the permission scope of actuated voltage, the output pressure and flux of the piezoelectric pump increase with actuated voltage increasing.3. the output pressure and flux of the piezoelectric pump have similar frequency characteristic. The curves of pressure and flux all have"pinnacle and valley"shape, and there is a optimal working frequency and a section of linearworking space. So we can obtain the required output by adjusting the frequency.4. The output flux of the piezoelectric pump with valve pump is affected by many factors, such as the cavity height and valve hole diameter. There is a optimal cavity height, output flux of the piezoelectric pump in this paper is largest when cavity height is 0.5mm, and output flux of pump increases with valve hole diameter increasing.