Two-Dimensional Three-Position Four-Way Electro-Hydraulic Directional Valve Based on Permanent Magnet Spring

Electrohydraulic control systems are widely used in aerospace, marine, engineering machinery, robotics, etc. Electrohydraulic directional valves are the core components of electrohydraulic control systems. Traditional electro-hydraulic directional valves utilize mechanical springs for zero positioning and power loss reset. In this study, a two-dimensional (2D) three-position four-way electro-hydraulic directional valve is proposed that utilizes a permanent magnet spring to replace the mechanical spring. The valve requires only one electro-mechanical converter to drive the spool reciprocating motion to realize the function of a three-position four-way valve. The valve is characterized by its simple structure, high power-to-weight ratio, and easy zero-point positioning. Firstly, the structure and working principle of the valve are described and the working principle of the permanent magnet spring is illustrated. Secondly, the circumferential restoring moment of the claw-pole magnetic levitation torque motor is analyzed based on the energy method, and the effects of auxiliary slots of different forms and structural parameters on the circumferential and axial permanent magnet springs are investigated. It is shown that the vertical auxiliary slot can significantly improve the stiffness of the circumferential permanent magnet spring, and the effect on the stiffness of the axial permanent magnet spring is small. When the width of the auxiliary slot is 10° and the depth is 0.5 mm, the circumferential permanent magnet spring stiffness can reach 68.5 mNm/°. And the reversing reliability of the reversing valve is analyzed, which shows that the reversing valve can drive the spool to move to the specified position sensitively after receiving the reversing signal.