Patent ID: 7737685
Filing Date: 2010-06-15
Classification: F15B,F16F,G01D,G11B,H01F

Abstract:
1. A piston rod position sensing system, comprising: a cylinder; a piston rod arranged in the cylinder for movement with respect thereto; a magnetically hard layer formed on the piston rod to provide a recording medium, the magnetically hard layer being made of a cobalt-phosphorous (Co—P)-based alloy, a magnetic pattern being recorded in the magnetically hard layer, wherein the magnetic pattern comprises a plurality of tracks recorded in the magnetically hard layer lengthwise of the piston rod in a direction of motion of the piston rod, each track comprising magnetically written regions that are used to uniquely identify a current position of the piston rod; and a magnetic field sensor for each track of the plurality of tracks, each magnetic field sensor being located proximate to one of the tracks to sense the magnetically written regions of information recorded in that track while the piston rod is moving with respect to the cylinder and to generate signals in response to the sensed magnetically written regions that are used to determine the particular position of the piston rod.