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AssigneeKayaba Kogyo Kabushiki Kaisha
InventorsMasakazu Nakazato, Youichi Shimoura, Masamichi Sugihara
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A first magnetic scale consisting of a plurality of non-magnetic parts are arranged axially at equidistant intervals, and a second magnetic scale consisting of a plurality of non-magnetic parts arranged axially at unequal intervals, are formed parallel to each other on a rod consisting of a magnetic material which can be displaced in the axial direction. The non-magnetic parts of the second scale are symmetrically disposed on both side of a predetermined position on the rod. First and second magnetic sensors are disposed in fixed positions facing the scales. A memory which individually memorizes the absolute position of each non-magnetic part on the second magnetic scale in advance, a mechanism which detects the interval between non-magnetic parts passing the second sensor, and a mechanism for distinguishing on which side the second sensor is situated with reference to the aforesaid predetermined position are provided, together with a mechanism for identifying a non-magnetic part which has passed based on the distinguishing result of the distinguishing mechanism and the detected interval, a mechanism for calculating the displacement amount of the rod from the identified magnetic part to its current position based on the output signal from the first sensor, and a mechanism for calculating the current position of the rod from the absolute position of the identified magnetic part and the calculated displacement. In this way, the displacement distance of the rod required to obtain absolute position information is reduced.
An axial position detector for a rod made of magnetic material, comprising a first magnetic scale comprising a plurality of non-magnetic parts arranged axially on the rod at equidistant intervals, a second magnetic scale parallel to said first scale comprising a plurality of non-magnetic parts arranged axially on the rod at unequal intervals, a first magnetic sensor for outputting a signal according to a positional change of the non-magnetic parts of said first magnetic scale, a second magnetic sensor for outputting a signal according to a positional change of the non-magnetic parts of said second magnetic scale, said magnetic sensors being respectively disposed in fixed positions facing said magnetic scales, means for separately memorizing absolute positions of the non-magnetic parts on said second magnetic scale in advance, means for detecting an interval between the non-magnetic parts passing said second sensor based on the output signal from said second sensor, means for identifying a non-magnetic part which has passed based on said detected interval, means for calculating a displacement amount of the rod from said identified non-magnetic part to its current position based on the output signal from said first sensor, and means for calculating the current position of the rod from the absolute position of the identified non-magnetic part and the calculated displacement, characterized in that:
Dependencies are inferred from the claim text.