基于空间微螺线管的金属颗粒检测研究

Research on the metallic particle detection based on spatial micro coil

目前电感式线圈检测方式均是基于线圈的电感信号,对铁磁性颗粒的检测精度可达到粒径19μm,但对非铁磁性金属颗粒一直在100μm以上。基于颗粒在通过电感式线圈的时候能同时引起线圈电感和电阻的变化,以及二者都随线圈激励电源频率变化而改变原理,建立粒径为108μm的球形铁、铜颗粒在1 V、1 MHz的激励电源下的磁场模型,分析阻抗信号随线圈电流频率的变化,研究利用电阻信号提高非铁磁性颗粒的检测精度,并通过实验验证:当频率由0.2 MHz增加到2 MHz,铜颗粒电阻信号由0.005 5Ω增加到0.6Ω,电感信号由-0.000 4μH降低到-0.011 5μH,铁颗粒电阻信号由0.008Ω增加到0.3Ω,电感信号由0.43μH降低到0.38μH;相同频率变化范围内,铜颗粒的电阻变化为铁颗粒的2.04倍,铜颗粒的电感变化为铁颗粒的22.2%;利用2 MHz激励电源检测电阻值变化提高了非铁磁性颗粒的检测精度,检测得到最小粒径为20μm的铜颗粒。

Current inductive coil detection methods are all based on the coil inductance signal. A minimum size limit of 19μm has been achieved for ferrous particles; however,the sensitivity to non-ferrous particles has been limited to 100μm. When metallic particles pass through an inductive coil,the inductance and resistance of the coil will both change; and the inductance and resistance of the coil change with the frequency of the coil excitation source. Based on this principle,the magnetic field model for the spherical iron and copper particles with the diameter of 108μm under the excitation source of 1V,1MHz was built,and the changing trend of the impedance vs. coil current frequency was analyzed; the method using the resistance signal to improve the detection sensitivity for non-ferrous metallic particles was studied,and experiment was conducted. Experiment results indicate that when the frequency changes from 0. 2MHz to 2MHz,the resistance signal of copper particle increases from 0. 0055Ω to 0. 6Ω,the inductive signal of copper particle decreases from- 0. 0004μH to- 0. 0115μH; the resistance signal of iron particle increases from0. 008Ω to 0. 3Ω,the inductive signal of copper particle decreases from 0. 4μH to 0. 38μH. Within the same frequency change range,the resistance change of copper particle is 2. 04 times of that for iron particle; and the inductive change of copper particle is22. 2% of that for iron particle. The method using 2MHz excitation source to detect resistance change improves the detection sensitivity of non-ferrous magnetic particles,the copper particles with minimum size of 20μm have been detected.