Patent ID: 9097749
Filing Date: 2015-08-04
Classification: G01N,G01R,G03G

Abstract:
1. A differential transformer type magnetic sensor comprising: a board formed of a printed circuit board that includes a first surface and a second surface located on the opposite side of the first surface; a reference coil that is formed as a three-dimensional conductor pattern on the board by repeating a first linear pattern that is formed on the first surface, penetrates the board, is formed on the second surface, penetrates a through-hole formed in the board, and returns to the first surface; a detection coil that is formed as a three-dimensional conductor pattern on the board by repeating a second linear pattern that is formed on the first surface, penetrates the board, is formed on the second surface, penetrates a through-hole formed in the board, and returns to the first surface; and a drive coil that is formed as a three-dimensional conductor pattern on the board by repeating a third linear pattern that is formed on the first surface, penetrates the board, is formed on the second surface, penetrates a through-hole formed in the board, and returns to the first surface, wherein the reference coil is disposed at a side of one end of the drive coil, and the detection coil is disposed at a side of the other end of the drive coil; induced current flows to each of the reference coil and the detection coil due to magnetic flux generated as drive current flows to the drive coil; the reference coil and the detection coil are electrically connected so that a direction of the induced current flowing along the reference coil and a direction of the induced current flowing along the detection coil are opposite to each other, and thus the differential transformer type magnetic sensor provides an output corresponding a height of toner contained in a development part of an image forming apparatus; the reference coil, the drive coil, and the detection coil are arranged so that a central portion of the reference coil, a central portion of the drive coil, and a central portion of the detection coil are located in a straight line; and the differential transformer type magnetic sensor is disposed relative to the development part so that the central portion of each of the reference coil, the detection coil, and the drive coil is located at a position of a reference height of the toner contained in the development part.