# US 2019/0170692 A1 · Rail inspection system > Agents: this data is available as JSON from the patentgrep API and MCP server — see https://patentgrep.com/llms.txt - Number: US 2019/0170692 A1 - Document ID: US20190170692A1 - Status: Published application - Kind: A1 - Application number: 16/313,729 - Filed: 2017-06-09 - Published: 2019-06-06 - Earliest claimed: 2016-06-28 - Assignees: Hitachi High-Tech Fine Systems Corporation - Applicants: Hitachi High-Tech Fine Systems Corporation - Inventors: Ryuzo KAWABATA; Akihiko KANDORI - Web page: https://patentgrep.com/patent/US20190170692A1 ## CPC - G01N 27/72: by investigating magnetic variables - B61K 9/08: Measuring installations for surveying permanent way - B61L 23/042: {Track changes detection} - B61L 23/047: {Track or rail movements} - G01B 7/003: {for measuring position, not involving coordinate determination (coordinate measuring G01B7/004)} - G01B 7/31: for testing the alignment of axes - G01B 7/345: {for measuring evenness} - G01R 33/12: Measuring magnetic properties of articles or specimens of solids or fluids (involving magnetic resonance G01R33/20) - G01N 2291/0234: Metals, e.g. steel - G01N 2291/2623: Rails; Railroads - G01N: INVESTIGATING OR ANALYSING MATERIALS BY DETERMINING THEIR CHEMICAL OR PHYSICAL PROPERTIES (measuring or testing apparatus or processes other than immunoassay, involving enzymes or microorganisms C12M, C12Q) - B61K: AUXILIARY EQUIPMENT SPECIALLY ADAPTED FOR RAILWAYS, NOT OTHERWISE PROVIDED FOR - B61L: GUIDING RAILWAY TRAFFIC; ENSURING THE SAFETY OF RAILWAY TRAFFIC (brakes or auxiliary equipment B61H, B61K; point or crossing construction E01B) - G01B: MEASURING LENGTH, THICKNESS OR SIMILAR LINEAR DIMENSIONS; MEASURING ANGLES; MEASURING AREAS; MEASURING IRREGULARITIES OF SURFACES OR CONTOURS - G01R: MEASURING ELECTRIC VARIABLES; MEASURING MAGNETIC VARIABLES (indicating correct tuning of resonant circuits H03J3/12) ## Abstract In a rail inspection system, a positional deviation can be detected with accuracy. The rail inspection system includes a first sensor unit which is disposed to face a rail for a vehicle, and includes at least one receiver coil and at least one oscillation coil which are arranged in an arrangement direction intersecting with a layout direction of the rail, an AC voltage source which applies AC voltage to the oscillation coil, and a displacement detection unit which detects a displacement between the rail and the first sensor unit based on an induced voltage of the receiver coil. The first sensor unit is configured such that, when the displacement is a first displacement, a first maximum value appears in the induced voltage, and when the displacement is a second displacement, a second maximum value of which a phase is reversed against the first maximum value appears in the induced voltage. ## Claims ### Claim 1 A rail inspection system, comprising: a first sensor unit which is disposed to face a rail for a vehicle, and includes at least one receiver coil and at least one oscillation coil which are arranged in an arrangement direction intersecting with a layout direction of the rail; an AC voltage source which applies an AC voltage to the oscillation coil; and a displacement detection unit which detects a displacement between the rail and the first sensor unit based on an induced voltage of the receiver coil, wherein the first sensor unit is configured such that, when the displacement is a first displacement, a first maximum value appears in the induced voltage, and when the displacement is a second displacement, a second maximum value of which a phase is reversed against the first maximum value appears in the induced voltage. ### Claim 2 (depends on 1) The rail inspection system according to claim 1, wherein the rail inspection system is mounted in the vehicle which runs on the rail, and the rail inspection system includes: a chassis which stores the first sensor unit; and an attaching tool which is used to mount the chassis in a bottom surface of the vehicle such that the first sensor unit is disposed at a predetermined position of the bottom surface of the vehicle. ### Claim 3 (depends on 1) The rail inspection system according to claim 1, wherein the first sensor unit includes a first oscillation coil, a first receiver coil, and a second oscillation coil which are arranged along the arrangement direction, and the AC voltage source applies the AC voltage to the first oscillation coil and the second oscillation coil such that a reverse magnetic field is generated. ### Claim 4 (depends on 3) The rail inspection system according to claim 3, further comprising: a second sensor unit which is disposed to face the first sensor unit along the layout direction, wherein the second sensor unit includes a third oscillation coil which faces the first oscillation coil along the layout direction, a second receiver coil which faces the first receiver coil along the layout direction, and a fourth oscillation coil which faces the second oscillation coil along the layout direction, and the AC voltage source applies the AC voltage to the third oscillation coil and the fourth oscillation coil to cause the third oscillation coil to generate a magnetic field of the same direction as the second oscillation coil, and to cause the fourth oscillation coil to generate a magnetic field of the same direction as the first oscillation coil. ### Claim 5 (depends on 4) The rail inspection system according to claim 4, wherein a gap between the first oscillation coil and the third oscillation coil is larger than a diameter of the first oscillation coil. ### Claim 6 (depends on 1) The rail inspection system according to claim 1, further comprising: a second sensor unit which is disposed to face the rail, and includes at least one receiver coil and at least one oscillation coil which are arranged in an arrangement direction intersecting with the layout direction, wherein a distance between the second sensor unit and the rail is longer than a distance between the first sensor unit and the rail.