Bulletin hy14-1450-M1/us installation and Service Guide
Parker Hannifin Corporation
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- Figure 2. Servovalve Operation - Command for Flow from Control Port C2
| Parker Hannifin Corporation
Hydraulic Valve Division Elyria, Ohio, USA Contamination Resistant Electrohydraulic Servovalves The Parker BD series servovalves are ruggedly designed for use in the industrial market place. From its inception, the first stage amplifier (pilot valve) has established a solid history of trouble-free operation in very harsh environments. Minimum orifice diameters up to 20 times larger than other servovalve models substantially increase reliability by reducing problems due to contamination. The second stage is a closed center, four-way spool and sleeve assembly which features rectangular slots in the sleeve. The spool metering edges exactly match the flow slot edges in the sleeve to provide linear flow with respect to electri- cal input. The valves have rated flows up to 40 GPM. Operation The BD series servovalves operate on a force feed- back principle between the second stage spool meter- ing valve and the first stage pilot valve torque motor. The pilot valve is a single jet pressure recovery unit that directs a continuing stream of control fluid into a receiver. The receiver has two outlets that are ported to the ends of the valve main spool, PC1, and PC2. The pressure in these ports is equal when the fluid jet is centered in the receiver opening. The feedback spring attached to the armature mea- sures spool position as a force. This force and the force of the torque motor armature provide the error displacement of the armature and its diverter blade window. The window edges divert the jet stream to the proper receiver outlet to position the spool to the electrically commanded position. Figure 2. Servovalve Operation - Command for Flow from Control Port C2 An electrical signal applied to the pilot valve coil generates a magnetic force on the armature/diverter blade assembly, pivoting the assembly and allowing fluid to flow into PC1. See Figure 2. This positions the main power spool to the left until the force from the feedback spring matches the magnetic force. At this time the diverter blade is re-centered over the receiv- ing orifices, and the spool motion stops at this position. Flow, proportional to the input electrical current, is then metered out the C2 port. Removal of the electrical signal to the coil unbalances the forces, which re- verses the armature deflection and drives the spool to the zero current or null position, as shown in Figure 3. Changing the polarity of the current to the coil causes a magnetic force in the opposite direction that results in flow from the C1 port. tải về 0.84 Mb. Chia sẻ với bạn bè của bạn:
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