Research On Lubricant Wear Debris Detecting Technology Based On Capacitance Sensor

Engine friction pair's abnormal operation is an important reason of engine fault. The debris produced by wear contains information of engine's wear and tear. Debris in lubricant can change lubricant's dielectric constant. So we can measure debris' s characteristic by detecting lubricant's dielectric constant, and measure engine's wear and tear. Lubricant's dielectric constant can't detect easily, but it's change can exhibit by lubricant's capacitance.This paper study on detecting technology of lubricant's debris based on capacitance sensor. It introduces theory of detecting lubricant's characteristic based on lubricant's dielectric constant, designs a capacitance sensor with three ring electrode, designs a detecting system's hardware circuit and testing procedure based on capacitance-to-digital converter AD7746 and SCM, experiments lubricant with different wear debris.The main contents of this thesis are as follows:1. Introduce theory of detecting lubricant's characteristic based on lubricant's dielectric constant, designs a capacitance sensor with three ring plate, and analyses this capacitance sensor's characteristic by using theory analysis and simulation analysis.2. Introduce several tiny capacitance detecting methods, design tiny capacitance detecting system based on capacitance-to-digital converter AD7746 and SCM, introduce it's procedure design and hardware design, introduce AD7746's detecting principle and method briefly, and introduce several digital filtering methods.3. Analy the detecting system by experiments, study on excursion of sensor's output, validate based on fixed value capacitance, study on debris' s impact on lubricant's dielectric constant by different size and amount based capacitance sensor.With experiment validate and data analysis, we can know that the lubricant's wear debris detecting system designed by this paper can detect impact on lubricant's dielectric constant caused by debris' s size quantificationally, and distinguish lubricant with different mount qualitatively. This experiment results can prove monitoring engine's friction and wear feasibility by using dielectric constant.