Hereinafter referred to as proportional valve electro-hydraulic proportionalvalve. The ordinary hydraulic valve can only through the way of preset pressure,flow rate of liquid flow fixed value control. But when equipment requirements inthe process of work of hydraulic system pressure, flow parameters to adjust orcontinuous control, for example. Hold bench when the job is feed to the slow,fast, slow speed to realize continuous change of feed, or in a certain accuracysimulate a curve of optimal control force control. The ordinary hydraulic valveare not achieve them. At this moment can electricity fluid proportional valve tocontrol the hydraulic system.

Electro-hydraulic proportional valve is a kind of proportion according to theinput signals continuously, according to control the hydraulic system of theliquid flow direction, flow and pressure of the valve. Tashan electrical andmechanical scale conversion device and hydraulic control valve body of twoparts. The former continuously in proportion to the input signal is converted tomechanical force and displacement output, the latter after accepting themechanical force and displacement, continuous output pressure and flow rate inproportion.

The development of the electro-hydraulic proportional valve is there are twomain ways a proportional electromagnetic valve to replace the traditional manualadjusting device of hydraulic valve or replace ordinary electromagnet developed;Second, by the electro-hydraulic servo valve to simplify structure, lowerprecision. Below the proportional valves are for the former, it is themainstream of today's proportional valve. With the ordinary hydraulic valve areinterchangeable.

Proportional electromagnetic valve structure as shown in figure 5-27.Proportional electromagnetic valve is a dc electromagnet, but it is differentfrom ordinary dc electromagnet. Common dc electromagnet suction and armatureonly disconnect two working position, and almost no air gap in magnetic circuitin the right. The proportional electromagnet suction force or displacement isproportional with the given current. And all the work schedule on armature,keeping the air gap 'in the magnetic circuit. Its structure is mainly composedof pole shoe 1, 5 and armature coil 2, shell 10, etc. A magnetic field coil 2after electrify, because of the existence of copper. 4. Makes through thearmature magnetic line of force major part 1, 10, air gap and pole shoe formback to the crossing pole shoe suction door on the armature current must be inthe coil. Because of the size of the suction pole shoe distance varies between 1and the armature. But the armature in the air gap is moderate for a period oftrip, suction change with the location of the change is very small.

Proportional electromagnetic valve is made in the design of the armature of workin this journey. So. To change the current in the coil, can get rather than onarmature is proportional to the suction. Proportional electromagnetic valve isused instead of the spiral handle to adjust the hydraulic valve, can make theoutput ricard or flow with input current is proportional to the correspondingchange.

Proportional valves to control the simulation, is between ordinary switchcontrol and servo control control mode, it is also particularly suited to Theinnovation of equipment or modification. Has greatly improve equipmentautomation control level. The liquid in the modern female large percentage inthe system.