US 9,810,747 B2
Magnetic sensor and magnetic encoder
Kunihiro Ueda, Tokyo (JP); Yoshiyuki Mizoguchi, Tokyo (JP); Hiroshi Yamazaki, Tokyo (JP); and Suguru Watanabe, Tokyo (JP)
Assigned to TDK Corporation, Tokyo (JP)
Filed by TDK Corporation, Tokyo (JP)
Filed on Jan. 15, 2016, as Appl. No. 14/996,536.
Claims priority of application No. 2010-67499 (JP), filed on Mar. 27, 2015.
Prior Publication US 2016/0282145 A1, Sep. 29, 2016
Int. Cl. G01B 7/14 (2006.01); G01R 33/09 (2006.01); G01R 33/00 (2006.01); H01L 21/00 (2006.01); G01R 1/00 (2006.01)
CPC G01R 33/09 (2013.01) [G01R 33/0052 (2013.01); G01R 33/093 (2013.01); G01R 1/00 (2013.01); H01L 21/00 (2013.01); H01L 2221/00 (2013.01)] 12 Claims
OG exemplary drawing
 
11. A magnetic encoder, comprising:
a magnetic sensor, and
a scale part that has an absolute signal track where absolute magnetic signals are recorded and an incremental signal track where incremental magnetic signals are recorded, wherein
the scale part is movable relative to the magnetic sensor,
the magnetic sensor comprises at least a first magnetoresistive effect element and a second magnetoresistive effect element that can detect an external magnetic field,
the first magnetoresistive effect element and the second magnetoresistive effect element each include at least a magnetization direction change layer where a direction of magnetization is changed according to the external magnetic field, respectively,
width W1 of the magnetization direction change layer in an initial magnetization direction of magnetization direction change layer of the first magnetoresistive effect element, length L1 in a direction that is orthogonal to the width W1, width W2 of the magnetization direction change layer in an initial magnetization direction of magnetization direction change layer of the second magnetoresistive effect element, and length L2 in a direction that is orthogonal to the width W2 have relationships shown by formulas (3) and (4) below,
sensitivity of the first magnetoresistive effect element to the external magnetic field is higher than that of the second magnetoresistive effect element to the external magnetic field,
the magnetic sensor and the scale part are placed to face each other to allow the first magnetoresistive effect element and the absolute signal track to face each other and to allow the second magnetoresistive effect element and the incremental signal track to face each other,
W1=W2  (3); and
W1/L1>W2/L2  (4).