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电液放大器是一种高品质的放大器。它被广泛地应用于各种工业部门的自动控制系统中。它一般由电气——机械转换器、液压预放大器和液压功率放大器三部分组成。四边滑阀常被采用作为液压功率放大器。电气——机械转换器有功圈、电磁及磁电三种型式，动圈式的优点为没有磁滞，而磁电式的优点为结构紧凑和动特性好。液压预放大器型式很多，常用的有针阀、小滑阀、喷嘴一板阀、剪口、射流等型式。此外电液放大器又可分为用弹簧联系、位置反馈，流量反馈、负载反馈等型式。合理选择电液放大器的型式和参数，能获得良好的静特性和动特性。 对几种电液放大器进行试验的结果表明：由于针阀式电液放大器一般做成单边控制，控制油路进油压力的变化将引起零点漂移。位置反馈的针阀式电液放大器具有同样缺点。小滑阀式电液放大器能做成对称控制，因而可克服上述缺点。但小滑阀付间的液压摩擦力使电液放大器具有较大死区，并且压力稍高、滑阀很易卡死。四边滑阀（功率放大级）的摩擦力很大，在滑阀上的非工作部分开槽并给滑阀以振荡后此问题得到解决。上述几种电液放大器在工艺、材料上并无苛刻的要求，工作压力较低时工作可靠，因之适用于结构重量不受限制、低压、特性要求不高的情况下。高压、结构紧凑、及动特性要
Electro-hydraulic amplifier is a high-quality amplifier. It is widely used in various industrial sectors of the automatic control system. It generally consists of three parts of the electro-mechanical converter, hydraulic pre-amplifier and hydraulic power amplifier. Four-sided spool valve is often used as a hydraulic power amplifier. Electrical - mechanical converter active coil, electromagnetic and magneto-three types of moving coil has the advantage of no hysteresis, while the magnetic advantages of compact structure and good dynamic characteristics. Many types of hydraulic pre-amplifier, commonly used needle valve, a small spool valve, a nozzle plate, notches, jets and other types. In addition, electro-hydraulic amplifier can be divided into spring contact, position feedback, flow feedback, load feedback and other types. Reasonable choice of electro-hydraulic amplifier type and parameters, can get good static characteristics and dynamic characteristics. Several kinds of electro-hydraulic amplifier test results show that: As the needle valve type electro-hydraulic amplifier is generally made unilateral control, control oil into the oil pressure changes will cause zero drift. Position feedback of the needle valve type electro-hydraulic amplifier has the same disadvantage. Small slide valve electro-hydraulic amplifier can be made symmetrical control, which can overcome the above shortcomings. But the small slide valve to pay the hydraulic friction between the electro-hydraulic amplifier has a larger dead zone, and the pressure is slightly higher, the slide valve is very stuck. The friction of the four-sided spool valve (power amplifier stage) is great and the problem is solved after the non-working part of the spool is grooved and the spool is oscillated. The above several electro-hydraulic amplifiers in the process, materials, there is no demanding requirements, working pressure is low, reliable, therefore suitable for structural weight unrestricted, low pressure, the characteristics of less demanding situations. High pressure, compact structure, and dynamic characteristics