| Die casting is important basic technical equipment in casting process. For die casting, speed and pressure real-time control play a significant role in improving the casting quality and accuracy. Two-way large flow electro-hydraulic servo cartridge valves(LFEHSCV for short) have been widely used in die casting due to their good response and large flow capacity, which can precisely control displacement and speed of shot hammer, to ensure the consistency of parameters in multiple die casting process. However, the valve still can’t control the injection pressure in pressurization process with closed-loop system. Currently, the standard three-way electro-hydraulic servo cartridge valve can control pressure with closed-loop, but still can’t fully meet the demands of high speed and large flow in large tonnage die casting due to its symmetrical design in main valve stroke. This paper focused on optimizing the self-developed 80-diameter two-way LFEHSCV, resolving the creeping in low speed and jittering in high speed during die casting. Based on the 80-diameter two-way LFEHSCV, this paper exerted to design three-way LFEHSCV to match die-casting system’s demand and realize continuous closed-loop control injection speed and injection pressure.In the first chapter, the die casting process and application of LFEHSCV in die casting system was introduced briefly. Then current research situation glabally about two-way and three-way LFEHSCV was summarized. Finally my research content and goal was proposed based on the shortage of self-developed two-way LFEHSCV in die casing process.In the second chapter, the creeping in two-way LFEHSCV was specifically analyzed and evaluated with ANSYS simulation, then validated the best tolerance in valve port. In the next, the disturbance force on the annulus area of spool was analyzed, and simulation model of injection system and two-way LFEHSCV was built. Through the simulation we find that the disturbance force is the key factor of spool vibration in high pressure and large flow working condition. Taking the less leakage demanding in low speed in account, the main valve port with the form of spool was designed, which further decrease the main spool chamber area to improve main valve response speed.In the third chapter, the three-way electro-hydraulic servo cartridge valve based on the die casting crafts’s demand was designed, and the key parameters was calculated. The hydraulic power suffered by main spool was analysed by Fluent software to guide design of main valve chamber area. Then the simulation models of three-way servo cartridge valve, injection system, and pressurization system were established to simulate the injection pressure with closed-loop control. Resulting that the injection pressure can reach the desired setting in 30ms. And we can also set the boost slope and final value for injection pressure based on demands.In the forth chapter, the two-way & three-way LFEHSCV was tested in injection test bed. Comparing to the original valve, the two-way LFEHSCV’s response speed was obviously increased and also low speed creeping and high speed vibration didn’t exist anymore. Testing the step response and hysteresis for three-way LFEHSCV, the result meet the demand, low speed creeping and high speed vibration didn’t exist anymore. So the valve structure design was validated to be reasonable.In the fifth chapter, a comprehensive summary was made, also both the research problems and the focal points for the future research were put forward. |
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