Two-dimensional magnetic sensor

• US 20030155913A1
• Filed: 10/21/2002
• Published: 08/21/2003
• Est. Priority Date: 02/19/2002
• Status: Active Grant

• Current Assignee: Aichi Micro Intelligent Corporation (Toyota Motor Corporation)
• Original Assignee: Aichi Micro Intelligent Corporation (Toyota Motor Corporation)
• Inventors: Yamamoto, Michiharu, Honkura, Yoshinobu, Mori, Masaki, Koutani, Yoshiaki
• Granted Patent: US 6,831,457 B2
• Time in Patent Office: Days
• US Class Current: 324/249
• CPC Class Codes: G01R 33/02 Measuring direction or magnitude of magnetic fields or magnetic flux G01R33/20 takes precedence

Abstract

The present invention is a two-dimensional magnetic sensor, comprising two miniaturized MI elements and an integrated circuit, which boasts a wide magnetic field measurability range, low power consumption, and an extremely small size, which is suitable for use as an electronic compass in, for instance, mobile devices like mobile phones.

Claims

1. A two-dimensional magnetic sensor which detects external magnetic fields comprising:

a first magneto-impedance sensor element, called the first MI element, provided to detect the first axial component of said external magnetic field, and which comprises a first magneto-sensitive element less than 2 mm long and a first electromagnetic coil which is wound around said first magneto-sensitive element;

a second magneto-impedance sensor element, called the second MI element, provided to detect the second axial component of said external magnetic field and which comprises a second magneto-sensitive element less than 2 mm long and a second electromagnetic coil which is wound around said second magneto-sensitive element; and

an integrated circuit comprising an oscillating means which supplies a pulse or high-frequency current, a means for switching current alternatingly between said first MI element and said second MI element, a means for detecting the output voltage from the electro-magnetic coils of said first and second MI elements, and an amplifier which amplifies the output voltage of said detection means.

2. A two-dimensional magnetic sensor as defined in claim 1, wherein, in said first and second MI elements, there is no substrate fixing the magneto-sensitive element in the space between the magneto-sensitive element and the electromagnetic coil and only insulation is used around the magneto-sensitivity element so that the inside diameter is less than 200 μ

m, and said first electromagnetic coil has a coil spacing per unit length of less than 100 μ

m/turn.

3. A two-dimensional magnetic sensor as defined in claim 1, wherein said first and second electromagnetic coils have a two-layer structure comprising one side placed in the inner wall face of a short groove in a substrate, and the other side is placed on the upper face of said groove.

4. A two-dimensional magnetic sensor as defined in claim 3, comprising the side of said electro-magnetic coil placed in the inner wall face of the groove in said substrate and an insulator which fills the space between the side of said electromagnetic coil that is placed on the upper face of said groove and in which said first and second magneto-sensitive elements are held.

5. A two-dimensional magnetic sensor as defined in claim 4, in which said first and second magneto-sensitive elements held in said insulator are made of amorphous wire.

6. A two-dimensional magnetic sensor as defined in claim 5, wherein said insulator is resin.

7. A two-dimensional magnetic sensor as defined in claim 6, wherein said amorphous wire is made of a CoFeSiB alloy.

8. A two-dimensional magnetic sensor as defined in claim 7, wherein an electrode is placed on the upper face of the substrate and comprises an electromagnetic coil terminal connected to the two ends of electromagnetic coil 3 and a magneto-sensitive element terminal which is connected to the two ends of said amorphous wire which comprises said magneto-sensitive element.

9. A two-dimensional magnetic sensor as defined in claim 8, wherein said first MI element is mounted in the X direction of said device mount board and said second MI element is mounted in the Y direction of said device mount board, orthogonal to said X direction, while said integrated circuit is integrally mounted on another part of the device mount board.

10. A two-dimensional magnetic sensor as defined in claim 3, wherein the size of said substrate is 0.5 mm wide, 0.5 mm high, and 2 mm long, and said groove 11 formed on said substrate is 50 μ

m deep, 70 μ

m wide, and 2 mm long.

11. A two-dimensional magnetic sensor as defined in claim 3, wherein said first and second electromagnetic coils have an average equivalent inside diameter (the area formed by the height and width and the circular diameter which determines that area) of 66 μ

m, and a coil spacing per unit length of 50 μ

m/turn.

12. A two-dimensional magnetic sensor as defined in claim 9, wherein said device mount board is 5 mm by 5 mm.

13. A two-dimensional magnetic-sensor which detects external magnetic field comprising;

a first magneto-impedance sensor element, called the first MI element, mounted on a device mount board to detect a first axial component of the external magnetic field, comprises a first magneto-sensitive element and a first electromagnetic coil which is wound around said first magneto-sensitive element, a second magneto-impedance sensor element, called the second MI element, mounted on said device mount board to detect a second axial component of the external magnetic field and which comprises a second magneto-sensitive element and a second electromagnetic coil which is wound around said second magneto-sensitive element, said first and second electromagnetic coils have a two-layer structure comprising one side placed in the inner wall face of a short groove on said substrate and the other side is placed on the upper face of said groove, said first and second magneto-sensitive elements which are placed in the insulator which fills the space between said two sides of the electromagnetic coil are amorphous wires, and said two-dimensional magnetic sensor comprises a means for detecting which passes current to the first and second MI sensors and detects the output voltage of the electromagnetic coils of said first and second MI sensors.

14. A two-dimensional magnetic sensor as defined in claim 13, wherein said detecting means comprises a means for passing current alternatingly between the first and second MI elements.

15. A two-dimensional magnetic sensor as defined in claim 14, wherein said detecting means comprises an integrated circuit and is mounted on said device mount board.