Views: 243 Author: Site Editor Publish Time: 2021-02-26 Origin: Site
From the perspective of existing hydraulic valve components, the narrowly defined digital valve specifically refers to the switch valve controlled by a digital signal and the valve island component integrated by the switch. The generalized digital valve includes hydraulic valves with parameter feedback and parameter control functions controlled by digital signals or digital pilots.
From the development history of digital hydraulic valves, the research on digital valves can be divided into two directions: incremental digital valves and high-speed switching digital valves.
The incremental digital valve combines a stepping motor with a hydraulic valve. The pulse signal is used to actuate the stepping motor through the driver. The stepping motor outputs a step angle proportional to the number of pulses, which is then converted into the displacement of the hydraulic valve spool.
The end of the last century was the golden age for the development of incremental digital valves. Many scientific research institutions and industries at home and abroad have successively introduced incremental digital valve products. However, due to the limitation of low frequency and out-of-step of stepper motors, incremental digital valves are not the current research focus.
The high-speed switch type digital valve is always in the fully open or fully closed working state, so the pressure loss is small, the energy consumption is low, and it is not sensitive to oil pollution. Compared with the traditional servo proportional valve, the high-speed switch valve can directly convert the ON/OFF digital signal into a flow signal, so that the digital signal is directly combined with the hydraulic system. In recent years, high-speed on-off digital valves have been a hot spot in the industry, mainly focusing on electro-mechanical actuators, high-speed on-off valve body structure optimization and innovation, high-speed on-off valve parallel valve islands, and new applications of high-speed on-off valves.
Since the middle of the last century, the research on high-speed switching electromagnets has always been the focus of high-speed switching valve research. The application of giant magnetostrictive materials and piezoelectric crystal materials provides new ideas for the development of high-speed switching valves.
Sweden has developed a high-speed fuel injection valve using giant magnetostrictive materials. By controlling the current of the driving coil, the super-magneto-hysteresis telescopic rod produces expansion and contraction displacement, and directly drives the valve port to open or close, so as to achieve the purpose of controlling the flow of fuel liquid. This structure eliminates the connection of mechanical parts and realizes fast and precise stepless control of the fuel and exhaust system.
The commonly used spool structures of high-speed on-off valves are hydraulic ball valve and poppet valve.
The threaded cartridge type high-speed switching valve (HSV) uses a ball valve structure. The push rod and the separating pin can adjust the opening of the ball valve and have the function of automatic centering. The valve adopts pulse width modulation signal control, the pressure can reach up to 20MPa, the flow rate is 2-9L/min, and the opening and closing time is ≤3.5ms. This high-speed switching valve represents the advanced level of domestic industrialized high-speed switching valves
The spool of the poppet-type high-speed on-off High Pressure Hydraulic Ball Valve is designed as a hollow structure, which reduces the movement quality and improves the response speed and acceleration. It moves the return spring from the armature position to the middle part of the spool, so that the spool receives electromagnetic force at the tail, and the middle part receives the spring restoring force, which is more stable during the movement.
However, this design makes the front and rear seats of the valve core have higher coaxiality requirements, and it is difficult to adjust the initial air gap and the valve core stroke. The opening and closing time of the valve is about 1ms, and it has been used in electronically controlled fuel injection systems.
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