SENSOR ARRANGEMENT FOR POSITION SENSING

• US 20180120129A1
• Filed: 12/27/2017
• Published: 05/03/2018
• Est. Priority Date: 03/12/2015
• Status: Active Grant

• Current Assignee: International Business Machines Corporation
• Original Assignee: International Business Machines Corporation
• Inventors: Haeberle, Walter, Pantazi, Angeliki, Sebastian, Abu, Tomas, Tuma
• Granted Patent: US 10,551,214 B2
• Time in Patent Office: Days
• CPC Class Codes: G01B 7/14 for measuring distance or clearance between spaced objects or spaced apertures G01B7/30 takes precedence
• CPC Class Codes: G01D 5/16 by varying resistance
• CPC Class Codes: G01R 33/09 Magnetoresistive devices
• CPC Class Codes: G01V 3/081 the magnetic field is produced by the objects or geological structures characterised by the method of magnetic field measurement G01R33/00

Abstract

A sensor arrangement for position sensing comprises a row of multiple magnetoresistive elements. A magnetic field source (3) provides a magnetic field with a first magnetic pole (N) and a second magnetic pole (S). The magnetic field source (3) is arranged such that magnetoresistive elements of the row face one of: the first magnetic pole (N) or second magnetic pole (S). The first magnetoresistive element is arranged in the magnetic field and provides a first output signal dependent on a position of the magnetoresistive element relative to the magnetic field source (3). A measurement unit is configured to determine a position of the magnetic field source (3) relative to the magnetoresistive elements of the row dependent on the first output signals of the magnetoresistive elements.

Claims

1. A sensor arrangement for position sensing, comprising

a magnetic field source providing a magnetic field with a first magnetic pole (N) and a second magnetic pole (S), and

two or more magnetoresistive elements arranged in the magnetic field in a row along a longitudinal axis (X) and having a gap between each magnetoresistive element in the row, said row of two or more magnetoresistive elements facing the first magnetic pole (N);

a measurement unit,

wherein the row of two or more magnetoresistive elements is arranged in the magnetic field and each providing an output signal dependent on a position of the magnetoresistive elements relative to the magnetic field source,

wherein the measurement unit is configured to determine a position of the magnetic field source (3) relative to the row of two or more magnetoresistive elements dependent on the output signals.

2. The sensor arrangement of claim 1, wherein each of the two or more magnetoresistive elements of the row comprises a stack of layers including at least a conductive layer in between two magnetic layers which layers have a longitudinal extension (L) along a longitudinal axis (X) and a lateral extension along a transverse axis (Y), wherein the magnetic field source has a dipole axis (DA) defined by the first and the second magnetic pole (N, S) extending along a vertical axis (Z) orthogonal to a plane defined by the longitudinal axis (X) and the transverse axis (Y).

3. The sensor arrangement of claim 2, wherein the magnetic field source is movable relative to the row of two or more magnetoresistive elements along the longitudinal axis (X), a position (x) thereof along the longitudinal axis (X) is to be sensed by the sensor arrangement, and wherein the measurement unit is configured to determine the position (x) along the longitudinal axis (X) by computing a difference between each said provided output signal.

4. The sensor arrangement of claim 1, comprising additional two or more magnetoresistive elements arranged in the magnetic field in an additional row along the longitudinal axis and having a gap between each magnetoresistive element in the additional row, said additional row of additional two or more magnetoresistive elements facing the second magnetic pole (S).

5. The sensor arrangement of claim 1, wherein the magnetic field source is dimensioned relative to the row of two or more magnetoresistive elements such that the magnetic affects a single magnetoresistive element of the two or more magnetoresistive elements at a time but not adjacent first magnetoresistive elements of the row, and wherein the magnetic field source is a permanent magnet which has a width (W) less than the longitudinal extension (L) of a magnetoresistive element in the row.

6. The sensor arrangement of claim 1, wherein the measurement unit is configured to identify the single first magnetoresistive element out of the two or more magnetoresistive elements that shows a change in its first output signal which change results from the magnetic field source passing by the single first magnetoresistive element, and wherein the measurement unit is configured to derive the position (x) along the longitudinal axis (X) from a known position of the single first magnetoresistive element within the row of the two or more first magnetoresistive elements.

7. The sensor arrangement of claim 1, wherein the magnetic field source is dimensioned relative to the two or more magnetoresistive elements such that the magnetic field not only affects a single of the two or more first magnetoresistive elements but also adjacent first magnetoresistive elements, and wherein the magnetic field source is a permanent magnet which has a width (W) along the longitudinal axis (X) exceeding the longitudinal extension (L) of a magnetoresistive element in the row.

8. The sensor arrangement of claim 3, wherein a magnetization orientation of both of the magnetic layers of each the two or more magnetoresistive elements of the row is unpinned, wherein the measurement unit is configured to subtract first output signals (R1) of adjacent first magnetoresistive elements (1) from each other, and wherein the measurement unit is configured to determine the position (x) along the longitudinal axis (X) dependent on a resulting difference signal.

9. The sensor arrangement of claim 1, comprising multiple magnetoresistive elements arranged in the row, said multiple magnetoresistive elements being offset from each other along the vertical axis (Z).

10. The sensor arrangement of claim 9, wherein a middle first magnetoresistive element (1m) is arranged at a closest vertical distance from the magnetic field source (3) amongst the multiple magnetoresistive elements of the row, and wherein outmost first magnetoresistive elements (1) are arranged at a farthest vertical distance from the magnetic field source (3) amongst the multiple first magnetoresistive elements of the row.

11. The sensor arrangement of claim 1, wherein one of the magnetoresistive elements of the row and the magnetic field source (3) is coupled to an object (5), the position of which object (5) is to be sensed by the sensor arrangement.

17. The method as claimed in claim 1, wherein the magnetic field source (3) is dimensioned relative to the two or more magnetoresistive elements of the row such that the magnetic field only affects a single (1a) of the multiple first magnetoresistive elements (1) at a time but not adjacent first magnetoresistive elements (1b, 1c), the magnetic field source (3) being a permanent magnet which has a width (W) less than the longitudinal extension (L) of a magnetoresistive element, said method further comprising:

identifying, by the measurement unit, the single magnetoresistive element out of the two or more magnetoresistive elements of the row that shows a change in its first output signal (R1) which change results from the magnetic field source (3) passing by the single first magnetoresistive element (1a), and

deriving, by the measurement unit, the position (x) along the longitudinal axis (X) from a known position of the first magnetoresistive element within the row of magnetoresistive elements.

12. A method for determining the position of an object, comprising:

coupling one of

a magnetic field source (3) providing a magnetic field with a first magnetic pole (N) and a second magnetic pole (S) and

two or more magnetoresistive elements with the object, said two or more magnetoresistive elements arranged in the magnetic field in a row along a longitudinal axis (X) and having a gap between each magnetoresistive element in the row, said row of two or more magnetoresistive elements facing the first magnetic pole (N);

arranging the magnetic field source (3) such that the first magnetic pole (N) faces the two or more magnetoresistive elements of the row to form a sensor arrangement,

receiving, at a measurement unit, an output signal from each of the two or more magnetoresistive elements dependent on their position (x) relative to the magnetic field source (3), and

determining, by the measurement unit, a position of the object (5) dependent on the received output signals.

13. The method as claimed in claim 12, wherein each of the magnetoresistive elements of the row comprises a stack of layers including at least a conductive layer in between two magnetic layers which layers have a longitudinal extension (L) along a longitudinal axis (X) and a lateral extension along a transverse axis (Y), said method comprising:

defining a dipole axis (DA) of the magnetic field source by the first and the second magnetic pole (N, S) extending along a vertical axis (Z) orthogonal to a plane defined by the longitudinal axis (X) and the transverse axis (Y).

14. The method as claimed in claim 13, further comprising:

moving the magnetic field source (3) relative to the first row of two or more magnetoresistive elements along the longitudinal axis (X), a position (x) thereof along the longitudinal axis (X) is to be sensed by the sensor arrangement, and

determining, by the measurement unit, the position (x) along the longitudinal axis (X) by computing a difference between each said provided output signal.

15. The method as claimed in claim 13, further comprising:

arranging additional two or more magnetoresistive elements in the magnetic field in an additional row along the longitudinal axis and having a gap between each magnetoresistive element in the additional row, said additional row of additional two or more magnetoresistive elements facing the second magnetic pole (S).

16. The method as claimed in claim 15, further comprising:

moving the magnetic field source (3) relative to the first row of two or more magnetoresistive elements along the longitudinal axis (X), a position (x) thereof along the longitudinal axis (X) is to be sensed by the sensor arrangement, and

determining, by the measurement unit, the position (x) along the longitudinal axis (X) by computing a subtraction of each said provided output signal of a magnetoresistive element in a common row and adding the results of the subtractions.

18. The method as claimed in claim 13, wherein the magnetic field source (3) is dimensioned relative to the multiple first magnetoresistive elements (1) such that the magnetic field not only affects a single (1a) of the multiple first magnetoresistive elements (1) but also adjacent first magnetoresistive elements (1b, 1c), the magnetic field source (3) being a permanent magnet which has a width (W) along the longitudinal axis (X) exceeding the longitudinal extension (L) of the first magnetoresistive element (1), and a magnetization orientation of both of the magnetic layers of the two or more magnetoresistive elements of a row is unpinned, said method further comprising:

subtracting, by the measurement unit, first output signals (R1) of adjacent first magnetoresistive elements (1) from each other, and

determining, by the measurement unit, the position (x) along the longitudinal axis (X) dependent on a resulting difference signal.

19. The method as claimed in claim 13, wherein a magnetization orientation of one of the magnetic layers of the two or more magnetoresistive elements (1) is pinned, said method further comprising:

adding, by the measurement unit, the first output signals (R1) of adjacent first magnetoresistive elements (1), and

determining, by the measurement unit, the position (x) along the longitudinal axis (X) dependent on a resulting sum signal.

20. The method as claimed in claim 13, further comprising:

arranging multiple first magnetoresistive elements (1) in the row offset from each other along the vertical axis (Z), wherein a middle magnetoresistive element is situated at a closest vertical distance from the magnetic field source amongst the multiple first magnetoresistive elements of the row, and outmost magnetoresistive elements of the row are arranged at a farthest vertical distance from the magnetic field source amongst the multiple magnetoresistive elements of the row.