US 2006/0052928 A1Published application

Wheel speed detection system

AssigneeCentral Japan Railway Company

InventorsNorifumi Kawasaki, Hideo Kita

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Abstract

In a wheel speed detection system wherein an eddy current displacement sensor is used, even when a distance between the eddy current displacement sensor and a convex portion of a rotator changes due to a change in load on a wheel, an error in a wheel assembly during a maintenance or other reasons, wheel speed can be detected accurately. Sensor detection voltage corresponding to an impedance change of a detection coil (11) generated in association with wheel rotation is inputted into a signal processing device (20). In a signal level determination unit (22), threshold voltages (VTH and VTL) are calculated based on sensor detection voltage after A/D conversion. Specifically, the difference between the average of sensor detection voltage, when the facing distance between a sensor head (10a) and a convex portion (7a) is a preset default facing distance (d0), and the average of actual sensor detection voltage is obtained, and preset threshold voltages are shifted for the difference. Thereby, irrelevant to a change in the above-mentioned facing distance, sensor detection voltage can be converted into pulse signals by the constantly appropriate threshold voltages.

Claims9

Dependent claims

A wheel speed detection system comprising:

a rotator which rotates on an axle center of a wheel together with the wheel, and plural concave and convex portions formed on a periphery of the rotator along a rotational direction with predetermined intervals therebetween;
a sensor head disposed so as to face a surface of the convex portion with certain distance therebetween, and constituted with a coil to generate alternate current magnetic field therearound under supply of alternate current;
a detector which excites the coil by supplying alternate current to generate eddy current on the concave and convex portions, and outputs alternate current detection signals corresponding to a change in an amount of the eddy current generated with rotation of the rotator;
a pulse converter which converts the alternate current detection signals into pulse signals according to preset threshold levels;
and
a speed calculator which calculates rotational speed of the wheel based on the pulse signals,
the wheel speed detection system further comprising a threshold shifter which shifts the threshold levels corresponding to actual facing distance between the surface of the convex portion and the sensor head,
wherein when the threshold levels are shifted by the threshold shifter, the pulse converter conducts conversion into the pulse signals according to the shifted threshold levels.

5 more elements

A wheel speed detection system comprising:

a rotator which rotates on an axle center of a wheel together with the wheel, and plural concave and convex portions formed on a periphery of the rotator along a rotational direction with predetermined intervals therebetween;
a sensor head disposed so as to face a surface of the convex portion with certain distance therebetween, and constituted with a coil to generate alternate current magnetic field therearound under supply of alternate current;
a detector which excites the coil by supplying alternate current to generate eddy current on the concave and convex portions, and outputs alternate current detection signals corresponding to a change in an amount of the eddy current generated with rotation of the rotator;
a pulse converter which converts the alternate current detection signals into pulse signals according to preset threshold levels;
and
a speed calculator which calculates rotational speed of the wheel based on the pulse signals,
the wheel speed detection system further comprising a detection signal shifter which shifts the alternate current detection signals outputted by the detector for some level corresponding to an actual facing distance between the surface of the convex portion and the sensor head, and
wherein when the alternate current detection signals are shifted by the detection signal shifter, the pulse converter converts the alternate current detection signals after the shifting into pulse signals.

5 more elements

Dependencies are inferred from the claim text.