Study of Novel Oil-Immersed Torque Motor for Two-Dimensional Valve

Abstract

The electro-mechanical converters of valves are mostly dry type, which cannot work for a long time under high currents due to heat dissipation. This paper presents a novel oil-immersed torque motor (OTM) that can carry out the 2D motion. The OTM has a separate wet working chamber and heat dissipation structure, and the coil is external to prevent oil contamination from causing short circuits. The equations of motion were established based on the equivalent magnetic circuit (EMC) method and its own characteristics, and the effect of oil damping in the working chamber on the dynamic characteristics of the novel OTM was studied. After analyzing its working principle and dynamic and static characteristics by finite element and numerical analysis software, a prototype was designed and machined, which could be operated in dry and immersed mode by adding parts. In addition, a dynamic and static test bench and a temperature rise test bench were established, and comparison experiments with a conventional dry-type torque motor (CDTM) were conducted. Experimental results showed that the prototype had a good thermal resolution in immersed mode, and when the coil was fully loaded (2.4 A), it still worked in the safe temperature range. The prototype had good current-torque characteristics and hysteresis linearity at a coil magnetomotive force (MMF) of 0–450 A. The output torque could reach 0.7 Nm when MMF exceeds 1000 A. The prototype had an approximately 4% faster step response in immersed mode and about 17.8% wider bandwidth than in dry mode, while the torque motor system was more stable due to the increased damping ratio. The measured open-loop dynamic and static characteristics met the requirements of the electro-mechanical converter of 2D servo valves.