Importance

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Abstract

A magnetic rotary encoder for detecting incremental angular displacement, angular velocity and rotating direction using magneto-resistors is disclosed. A drum, disk or cupshaped rotary member is attachable to a rotatable shaft. A magnetic medium is provided on a surface of the rotary member and is divided at a pitch p into a plurality of magnetic sections each of which has a magnetic signal recorded. The magnetic medium produces an alternating magnetic field as the rotary member revolves. Alternatively, a plurality of permanent magnets are provided on the surface of the rotary member to produce the alternating magnetic field of the rotary member revolves. A magnetic field detector includes at least one magneto-resistor having a stripe-like configuration with width D. The magneto-resistor is located in the vicinity of the rotary member so as to be spaced from the magnetic medium or the permanent magnets by equal to or less than p at its nearest portion and by equal to or less than 20p at its furthest portion. The width D is selected so as not to be in excess of 20p but to be equal or less than p .sec .phi., where .phi. is an angle defined by the nearest surfaces of the magneto-resistor and the magnetic medium or permanent magnets. The magneto-resistor is responsive to the alternating magnetic field to generate an analog signal representative of its electrical resistance change corresponding to the increment of the rotational angle of the rotary member. A rotary condition detector is electrically connected to the magnetic field detector to receive the analog signal and produce signals indicative of the rotating conditions of the rotatable shaft.

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First Claim