Improved Design And Experimental Study Of Near-Zero Friction Pneumatic Injection Valve

Pneumatic jet dispenser is of high research value and can be economically beneficial because of their ability to dispense micro-droplets of larger viscosity fluids and their wide range of applications.Based on the previous work in the laboratory,to meet the performance requirements of pneumatic jet dispensers in the industrial production,mechanical structure of a near-zero friction pneumatic double-acting jet dispenser is improved.And a near-zero friction pneumatic single-acting jet dispenser is redesigned.The dynamic performance and dispensing performance of the two pneumatic jet dispensers are analyzed and studied by establishing the dynamic simulation model and an experimental system.Structural design of pneumatic jet dispenser: Two design ideas of pneumatic jet dispenser are proposed and the principles are explained.For the previous generation of near-zero friction pneumatic double-acting jet dispenser,there are structural problems such as long gas pipelines and inconvenient installation of the solenoid valve,a jet dispenser with new connection method is designed in this paper,which connects the solenoid valve with the gas pipeline through threads.It can both shorten the length of the gas pipeline and further reduce the overall size of the jet dispenser.At the same time,a pneumatic single-acting jet dispenser is redesigned by using the existing structural parameters and taking into account the generality of the parts as much as possible.The cylinder parameters are optimized and the designs of the double spring system are completed for each of the two pneumatic injection schemes respectively.Finally,a new measurement structure and scheme are proposed to realize the acquisition of dynamic data of the pneumatic jet dispenser.Dynamic simulation analysis of pneumatic jet dispenser: the mathematical model of cylinder static filling and discharging of cylinder is established,and the driving force functions about pneumatic single-acting and double-acting jet dispensers respectively are created according to the results of mathematical analysis.The dynamic simulation models of pneumatic single-acting and double-acting jet dispensers are created by ADAMS.By inputting the corresponding driving force functions,and the force transfer relationships between piston-needle and needle-nozzle,as well as the influence of the needle speed by the relevant parameters.Experimental study of pneumatic jet dispenser: the pneumatic jet dispenser experimental system is built to verify the feasibility of the newly designed displacement measurement scheme.The comparison analysis between the simulation results and the experimental results of the jet dispenser shows that the established dynamic simulation model has certain reliability when the operating frequency is 100 Hz and the driving air pressure is 0.3MPa,0.4MPa and 0.5MPa respectively.The experimental study is divided into two parts.The first part is a pneumatic single-acting jet valve dispensing experiment,in which the effects of driving air pressure,operating frequency and needle stroke on the volume and consistency of the drops are investigated through parametric control.When the driving air pressure is 0.5MPa and the working frequency is200 Hz,the average volume of glue drops is 52.6nl,and the maximum absolute error of glue drops volume is 1.8nl,and the relative error can be controlled within 1.7%.The second part conducts experimental studies of pneumatic double-acting injection valves.The upper and lower solenoid valve power-on time ratio has a large impact on the dynamic performance of the jet dispenser,the result shows that the needle can obtain a better displacement curve and dynamic performance at 50% duty cycle merely.The displacement data of pneumatic double-acting jet dispenser are collected at the working frequency of 100 Hz ～ 250 Hz to study the dynamic performance of the needle at different frequencies.At the same time,the driving air pressure of the upper and lower chambers of the cylinder is changed by adjusting the precision regulator,and the influences of the driving air pressure and the driving differential pressure on the motion state of the jet dispenser are investigated.Finally,the dispensing performance of the pneumatic double-acting jet dispenser is evaluated.At the working frequency of 250 Hz,the average volume of the droplets ejected by the pneumatic double-acting jet dispenser is 52.7nl.Its relative error could be controlled within ±1.4%,which shows good droplet consistency.