An iron filter is provided to attract iron powder in lubricating oil, thereby preventing the deterioration of the lubricating oil, by improving the arrangement of permanent magnets disposed on an inner surface of the iron filter. An iron filter comprises a circular collar(100) having an inner surface and an outer surface, a plurality of magnet structures(156) arranged along a circumferential direction of the inner surface of the collar, and air gaps(205) each positioned between neighboring magnet structures. Each of the magnet structures is composed of two magnets adjacent to each other. The two magnets of each magnet structures have opposite polarities in contact with the inner surface of the collar so that a magnet field formed by the two magnets heads toward the center of the collar. The magnet structures are arranged in parallel with one another while two adjacent magnets of neighboring magnet structures have the opposite polarities. The air gap between neighboring magnet structures make the magnet field infiltrate an inside of the circular collar deeply, thereby attracting iron moving away from the filer.
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