Encoder

Abstract

Provided is an encoder capable of improving the detection accuracy of a moving amount with a gap between it and a magnetic medium. The magnetic medium is magnetized at a predetermined pitch λm in the above-mentioned relative movement direction, and the magnetic sensor has a plurality of magnetoresistive effect elements whose resistance values ​​change according to the magnetic field of the place where they are arranged so as to configure The position of the magnetoresistance effect element is the reference position, and in addition to the magnetoresistance effect element at the reference position, the magnetoresistance effect elements as the high-order harmonic reduction pattern are respectively arranged at the following positions: Let P(n) be the nth A prime number, using a natural number N > 3, a position away from λm / (2·P(n)) (where N≥n>1) from the above-mentioned reference position to at least one side of the above-mentioned relative movement direction; and a position away from λm / The position of (2·P(L)) (where 1<L<N) is further deviated from the position of λm / (2·P(L+1)).

Description

technical field [0001] The present invention relates to encoders, and particularly to the reduction of higher harmonics. Background technique [0002] A magnetic encoder is known that uses a magnetic medium in which N poles and S poles are alternately arranged, and detects a change in leakage magnetic field from the magnetic medium by a magnetic sensor that moves relative to the magnetic medium , thereby detecting the amount of movement (Patent Document 1). [0003] The smaller the pitch λ of the different magnetizing directions, the higher the detection accuracy of the encoder, but the smaller the pitch λ, the smaller the leakage magnetic field from the surface of the magnetic medium. Therefore, the magnetic sensor contacts the magnetic medium. It is difficult to obtain a sufficient output signal if it is too close to slide on the magnetic medium. [0004] exist Figure 15 (a) shows an example of the output signal when the magnetic sensor moves on the magnetic medium. If...

AI Technical Summary

Problems solved by technology

Making the distance between the magnetic medium and the magnetic sensor close means that the sensor output is likely to fluctuate greatly with respect to the distance, and the degree of freedom in device design may be narrowed

In addition, in the case of using a magnetic scale (magnetic medium) long in the direction of relative movement, if the magnetic sensor is kept in contact and moved over a long distance, the drive device (motor, etc.) needs a large rotational speed due to frictional resistance. torque, it is difficult to cope with a small motor, which hinders the miniaturization of the device

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