The Research Of A New Type Digital Proportional Pilot Operated Electron-hydraulic Valve For The Loader

With the rapid development of national economy, as the main construction equipment, the engineering machinery are playing an more and more important role in our country's economic construction. And at the same time people putting forward higher request for engineering machinery such as light, safe, comfortable to handle, high dependability etc. Meanwhile, with the integrated application of mechanics technology in hydraulic technology, the mode that electronic component control the hydraulic component directly will adopt extensively As a new digital valve, High-speed switch valve have many advantage such as having simple structure, reacting fast, resisting pollution and so on. It is still not generally used at home, but it has already been applied to the engineering machinery and agricultural machinery rifely abroad, and is paid to more attention day by day. In order to follow the development trend of this kind of technology abroad, we tried this new type electro-hydraulic proportional valve in the engineering vehicle pilot operated in the theme, replacing the traditional electron-hydraulic proportional valve in the loader. The traditional electron-hydraulic proportion valve have disadvantage such as complicated structure, require the liquid have good purity, expensive in price, and professional maintenance, bad adaptability to poor vehicle environment, so there is certain restriction in applying it to engineering vehicles. Digital electro-hydraulic proportion control system has many merits such as excellent repetitiveness, small, cheap, simple structure, good flexibility to pollution, convenient interface with computer, etc., so there are wide application prospects of it. The high-speed switch valve work on two states: on and off. An ordinary solenoid can control it, so the expensive proportion electro-magnet can be saved. The main executive structures of the loader, scraper bowl and shaking arms are all controlled by cylinders. The integrate components of the digital electron-hydraulic proportion control system are instruction selection switch, handle resistance, electronic control module, pilot proportion valve, pilot operated proportional valves, and the controlling cylinder. The control principle of the electronic system is that at first we init the control the instruction selection switch, so the electronic module can judge that the control instruction comes from the handle or comes from the data interface; Then gather parameters from corresponding passway that indicated by the switch, and generate PWM signal with some rule by the parameters. Finally after the amplification circuit on the electronic control module the signal has enough power to drive the high-speed switch valve to work. The core of the plural channels valve will move when there are differential pressures between its two controlling cavities, so we can realize the controlling of the of the plural channels valve by make the pilot high-speed switch valve to control the pressure of controlling cavities. And the high-speed switch valve here we used is of 2/2-way slip-in valves. When the high-speed switch valve is powered, the controlling cavity connects the oil source and the oil enterer the controlled cavity, so the controlling cavity is rising. But when the high-speed switch valve is out of power, the controlled cavity connect the oil tank, and the oil is flow outwards, the pressure of the controlled cavity is reducing. When input continuous PWM signals, we can see the average cavity pressure will round a certain invariable value. While when the width of the PWM signal pulse changed, the cavity pressure will be changed too. So we can control the working device of the loader by tuning up the width of the PWM signal that drives the high-speed switch valve. Then, the problem needed to solve mainly in this subject is how to control the cavity pressure with the high-speed switch valve, and to realize this object we should make a mathematics model of the cavity and simulate on some software.(1) Dynamic character analysis with the high-s...