The Key Technology Research Of The Piston Ring’s Vision Inspection Under Free State

Piston ring is an important part of the engine,that plays seal effect between the piston and the cylinder, so that its quality directly affects the engine performance and exhaust emissions.Piston ring end gap size and the outer round degree is the most important mechanical processing technology indicator, and it ask for product inspection.At present, it usually rely on manual inspection, existing problems such as large labor intensity, low efficiency and poor accuracy and so on.In recent years following product quality requirements and the rising cost of labor force, enterprises urgently need a higher quality, higher efficiency and lower the cost of inspection technology and equipment. Based on machine vision detection technology grows up in recent years and is becoming more and more mature technology, and its application areas covers almost the modern manufacturing industry, that the technology becomes the ideal means of replace artificial test product quality by its feature of accurately precise, fast efficient and non-contact.Our research group has successfully developed a full automatic machine vision inspection system of piston ring, which is applied to a piston ring manufacturing enterprises.The system simulates the work environment of piston rings, that is, pressing the piston ring in gauge,and directly measuring the gap size and roundness (light-leaking) size.its weakness is low efficiency and complex machinery.Aiming at these problems, this paper research the visual detection technology of piston ring under the free state, mainly include three aspects:First, it detect and judge the closed edge defect that is affected piston ring end gap size,and it use the morphological image processing including opening and closing operation to "close" and "erase" the defection of convex-concave closed edge. Researching the matching method based on eigenvalue, using the image pyramid for defect detection. Second,Research and design the algorithm of the measurement of end clearance.and carrying out the experiment. Applying the sub-pixel edge detection algorithm and developing the sub-pixel edge detection algorithm based on two order polynomial interpolation to extract the edge of piston ring.Studied the segmented circular curve fitting using least squares method to calculate the length of the paragraphs of arc and the edge of the long piston ring, so that silent gap size is calculated. One of the key factors influencing the precision and efficiency is the number of section arc. Experimental results show that,Dividing the edge into three segments can meet the accuracy requirements, and higher efficiency. Third, researching the light leak detection of piston ring under the free state. Starting from outer length and curvature law of piston ring, and researching the feasibility of detecting light leakage of piston ring.