Pretension - Limit Pneumatic Digital Piezoelectric Ball Valve Structure And Characteristics

Piezoelectric(PZT) actuator with its fast response, wide operating frequency, easy to control, etc., has been widely used in pneumatic proportional valve. This thesis is based on the original free through-hole(FH) type piezoelectric ball valve, analyses its disadvantage, proposes a new structure of pretightening limit type(PL-l) piezoelectric ball valve, in addition, researches the ball's vibration displacement and the ball valve's flow.Firstly, analyses the disadvantage of the FH type piezoelectric ball valve, proposes a program that using the spring pretightening for PZT actuator, at the same time, in order to avoid the ball breaking away from the spool, increases a horizontal limit-displacement structure. Designing a new pretightening limit type piezoelectric ball valve to research.Secondly, the thesis researches the theory model with the different importing signal, and it is focus on the resonance model when pulse signal is inputted, the ball's vibration displacement and valve's flow is analyzed by simulation, which shows that the ball valve's flow is proportional to the signal frequency ,we can control the flow through adjusting the frequency, it gives a basis for experiment. It also proves that this model is right through comparing the trial with the simulation.Thirdly, the vibration amplitude of PZT have been studied in experiment and the vibration capacity of the ball as well. Meanwhile, the influencing factors relative to the vibration capacity of the ball, which primarily involve pressure differential, pulse frequence, diameter of the ball, spool displacement of valve and supply voltage, were tested respectively. And the results of experiment indicates that the vibration displacement of the ball is proportional to the signal frequency. In addition, the vibration displacement of the ball tends to be smaller if spool displacement of valve and the pressure differential are larger or the diameter of the ball is smaller.At last, testing and measurement have been implemented under various conditions, including different signal frequency of voltage, pressure differential, diameter of the ball and valve core, in order to obtain the flow characteristic of the PL-1 type piezoelectric ball valve. And the results of experiment indicated that the valve's flow is proportional to the signal frequency when the frequency is low. The ball valve's flow reaches the maximum that is 7L/min(the diameter of ball is 7mm, the pressure differential is 0.05MPa and the frequency is 500Hz). However, great fluctuation occurred with high frequency.The research demonstrates that the vibration displacement of the ball and the flow of ball valve of PL-1 type piezoelectric ball valve have been great improved compareing with FH type piezoelectric ball valve. And this piezoelectric ball valve will have a great prospects.