| It has been over30years for research and development of micro-piezoelectric pump (take "micro-pump" for short) up to now. With the appearance of new materials and process, micro-pump dimensions have been reduced, and the output performances have been improved in the same time. Recently, some kinds of micro-pump have been produced as product, which goes to variance of application, e.g. biological medicine, fine chemicals, civil consumption and so on, with a bright future. However, new requirements are brought up with the rapid development of portal MEMS devices, especially the requirements of power consumption micro-pump, efficiency, lifetime, etc. Based on micro-pump research status home and aboard, the important point of study stays in the improvement for structure innovation and output performances. Systematical and deep study on the working principles, characteristics and design theory is rare. Because of lack of theoretical conduction, it’s common to see high power consumption and low efficiency.Combined with the technical specification of national high-tech research and development program (namely863program):MICRO SYSTEM OF BLOOD GLUCOSE DETECTION AND INSULIN INJECTION with the No.2011AA040406, in the premise of miniaturization, the internal factors for micro-pump performances, power consumption and efficiency are clarified through the analysis on all components, system working principles and characteristics of micro-pump, which are the theoretical and technical support for the development to satisfy the requirements of micro-pump products of portable micro fluid control devices.Micro-pump, which determines the maximum output performance of micro-pump, is the driving element of the pump. And driving capacity is determined by the piezoelectric ceramics (PZT), which makes the choice for PZT very important. PZT5, with high coupling coefficient together with the piezoelectric constant of low power consumption, big amplitude, is chosen in the paper through the comparison of PZT electronic and mechanical characteristics in Chapter2. Regarding to the theoretical calculation methods of the round piezoelectric vibrator (take "piezo-vibrator" for short) structure parameter matching and optimization have been already mature, but too many parameters involved in the calculation makes the real application difficult. Piezo-vibrator equivalent fixate concept is introduced, which is corresponding with piezo-vibrator’s output force directly. Through the theoretical calculation, the linear relationship among piezo-vibrator center point displacement, equivalent fixate and driving voltage is proved, and at last, the formula between equivalent fixate and driving voltage is educed. The expressions of maximum flow and maximum force of micro-pump are educed through piezo-vibrator center point displacement and equivalent fixates, and moreover, the relationship between limit performances and voltage are received. When it comes to the optimization for the piezo-vibrator, the output force and displacement characteristics can be the direct estimating index for the driving capacity. To reduce the development time for piezo-vibrator, and decrease the development cost in the same time, FEA simulation for electronic coupling which can well matched the theoretical calculation result is brought up. Furthermore, experiments are carried out to evaluate the veracity, and it turns out to be feasible.The micro valve is the key control part in micro-pump. Micro passive cut-off valve has more advantages compared with other valves in dimension, cost and power consumption. Ultimately, wheel valve is chosen in the micro-pump as the micro valve through the advantages and disadvantages comparison of the common micro passive cut-off valve in Chapter3. Firstly, common wheel valve’s equivalent rigidity is calculated in theory, and the feasible measurement methods are put forward. Then, statistic characteristics of wheel valve are analyzed, in particular, wheel valve critical working pressure and cut-off phenomena induced by capillarity, which is called capillarity cut-off phenomena are discussed. This phenomena guarantees complete cut-off capacity in micro-pump, which can increase micro-pump practicability.Because of the existence of the valve sub-base, the motion status of wheel valve plate is vibro-impact in most instances. It turns out from the experiment that the impact mode of the valve sub-base and valve plate changes from retention collision to non-retention collision, which is analyzed in the paper in theory, and the boundary conditions of different impact modes are defined, periodic net flow and accumulated net flow expressions are educed in different impact modes. It indicates that the flow change rule shown in the expression is common through research.During working, the energy loss of wheel valve can be divided into water head loss, collision loss and flow loss. Thereinto, water head loss is related with wheel valve and its mounting structure, and the collision loss is related with wheel valve rigidity, frequency, and so on.It is found that there is cubage flow caused by pump chamber cubage change, and in addition, the inertia flow caused by the piezo-vibrator working on the fluid has big influence on the output flow, through theoretical and simulation analysis from Chapter4, starting from sucking outflow phenomena. The flow calculation formula educed from traditional micro-pump working principle has big deviation with the reality. Based on the valve overflow characteristics, new flow calculation formula is educed in this paper, and inertia flow is involved, so it expresses the micro-pump flow change tendency well and truly, which tallies with the experiment well.The electrical energy is changed into mechanical energy in vibration form, which the pump chamber, valve and the accessory structure changes into the fluid’s flow energy. Suppose electric power, mechanical power and flow power are used to express the three kinds of energy above, if the electric power has no change, flow power can be the criterion of the micro-pump working efficiency. The flow power can be estimated directly from the micro-pump pressure-flow characteristic curve. Meanwhile, the pressure-flow linear characteristic and change rule shows that the working frequency of micro-pump is not constant, but is related with the frequency, load and pipe-system characteristics. Therefore, except increase piezo-vibrator electromechanical transformation efficiency and decrease the valve working consumption into maximum extent, the micro-pump working frequency and driving voltage can be adjusted based on pressure-flow characteristics and pipe-system characteristics, to make the operating point appear in the maximum efficiency point of the pressure-flow characteristics’curve.The research on piezo-vibrator, passive cut-off valve and micro-pump working principle and characteristics, has provided theoretical basis for high efficiency and low power consumption of the micro-pump. In Chapter5, experiments on micro-pump driving voltages are done, and the results are as stated in Chapter2, output flow and pressure have linear relationship with driving voltage. The driving waveform experiment indicates when it’s sine wave the micro-pump is driven, it has higher working efficiency compared with square wave. However, since square wave drive electric circuit has the advantages of simple structure, high efficiency, easy to be miniaturized and so on, square wave is adopted as the driving signal of micro-pump finally, and miniaturized, low power consumption micro-pump driving circuit is developed.Based on the factors of wheel valve working characteristics and energy consumption, the structure parameters like the rigidity of the wheel valve, the matching dimension between valve plate and valve hole, the height of the preload boss, are mated, in the end, micro-pump integrated with driving circuit, with the power consumption of11mW is made. The maximum output force is30kPa, and the maximum flow is25ml/min. Moreover, the output characteristics with the micro-pump in series and in parallel are studied in Chapter5, and the basis for the selection for in series and in parallel is introduced.Lifetime test is an important part in product development, in order to shorten development time for micro-pump product, based on the failure mechanism of the micro-pump product,100micro-pumps manufactured in series production processes are tested in accelerated stress level for3400hours under accelerated life test with failure truncation constant-stress accelerated life test according to GB2689.1-81. The experimental data are analyzed with best linear unbiased estimation method regulated in GB2689.4-81. The result shows that the life time of the micro-pump under normal stress level is around5800hours with the reliability of0.95. |
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