Arrangement for determining the position of a motion sensor element influencing the formation of a magnetic field of a working magnet along its motion coordinate

• US 6,956,366 B2
• Filed: 03/04/2003
• Issued: 10/18/2005
• Est. Priority Date: 03/07/2002
• Status: Active Grant

• Current Assignee: NXP B.V. (NXP Semiconductors NV)
• Original Assignee: Koninklijke Philips Electronics N.V. (Koninklijke Philips N.V.)
• Inventors: Butzmann, Stefan
• Primary Examiner(s): PATIDAR, JAY M
• Application Number:
  US10/379,321
• Publication Number:
  US 20030222642A1
• Time in Patent Office: 959 Days
• Field of Search: 324/207.21, 324/207.25, 324/207.12, 324/207.13, 324/207.15, 324/207.16, 324/207.17, 338/32.R
• US Class Current: 324/207.21
• CPC Class Codes: G01D 5/147 influenced by the movement of a third element, the position of Hall device and the source of magnetic field being fixed in respect to each other
• CPC Class Codes: G01D 5/24438 Special design of the sensing element or scale
• CPC Class Codes: G01P 3/488 delivered by variable reluctance detectors
• CPC Class Codes: G01R 33/07 Hall effect devices
• CPC Class Codes: H03F 2200/261 Amplifier which being suitable for instrumentation applications

Abstract

An arrangement can determine the position of a motion sensor element influencing the formation of a magnetic field of a working magnet periodically along its motion co-ordinate. Such an arrangement includes

• • a sensor arrangement, sensitive along a measuring direction aligned parallel to the motion co-ordinate of the motion sensor element.

The motion sensor element includes; periodically recurrent areas alternately influencing the measuring field which is being formed parallel to the main surface.

The magnetic field of the working magnet is aligned perpendicular to the main surface of the motion sensor element.

The sensor arrangement is formed as a magnetoresistive sensor arrangement with at least one half bridge.

The arrangement according to the invention provides the possibility of a reliable operation, with a simple structure, also under said conditions and, in connection with a great freedom from interference, it is also quite insensitive to manufacturing tolerances.

Claims

1. An arrangement for determining the position of a motion sensor element influencing the formation of a magnetic field of a working magnet periodically along its motion co-ordinate, the arrangement comprising

a sensor arrangement, impressed with the magnetic field of the working magnet, wherein said magnetic field is sensitive along a measuring direction aligned at least substantially parallel to the motion co-ordinate of the motion sensor element to at least the polarity of the magnetic field of the working magnet impressed on the sensor arrangement and is adapted to supply a measuring signal in dependence upon a field component of the magnetic field of the working magnet impressed on the arrangement, denoted as measuring field and measured in the measuring direction,

wherein the motion sensor element, arranged in zone of a surface, said zone extending along the motion co-ordinate of the motion sensor element, comprises periodically recurrent areas alternately influencing the measuring field which is being formed parallel to the main surface and is at least substantially parallel to the motion co-ordinate of the motion sensor element, and the measuring direction of the sensor arrangement is aligned at least substantially parallel to the surface of the motion sensor element,

wherein the magnetic field of the working magnet impressed on the sensor arrangement is aligned substantially perpendicular to the main surface of the motion sensor element with its main component determined by the principal direction of the magnetic field lines,

wherein the sensor arrangement is formed as a magnetoresistive sensor arrangement with at least one half bridge comprising at least two magnetoresistive sensor elements, which sensor elements are sensitive along the measuring direction to the magnetic field strength of the magnetic field of the working magnet and are adapted to supply the measuring signal in dependence upon the measuring field, at least two sensor elements in each half bridge having barberpole structures with mutually different alignments,

characterized by

an arrangement for generating an additional magnetic field having a variable magnetic field strength, which additional magnetic field is aligned, at least substantially in the area of the extension of the sensor elements, substantially parallel to the magnetic field of the working magnet with its main component determined by the principal direction of its magnetic field lines, and for superimposing the magnetic field of the working magnet with said additional magnetic field so as to form a resultant magnetic field producing a resultant measuring field,

an arrangement for temporally varying the magnetic field strength of the additional magnetic field for detecting values of the measuring signal in dependence upon these variations of the additional magnetic field and for storing these values of the measuring signal, and

an evaluation unit for forming an output signal representing a measure of the motion co-ordinate of the motion sensor element by subtracting at least two consecutively detected values of the measuring signal.

2. An arrangement as claimed in claim 1, characterized in that the arrangement for generating the additional magnetic field comprises a coil arrangement which can be impressed with a temporally variable coil current.

3. An arrangement as claimed in claim 2, characterized in that the coil arrangement at least substantially encloses the sensor elements along their spatial extension parallel to the main surface of the motion sensor element.

4. An arrangement as claimed in claim 2, characterized in that the coil arrangement is formed at least substantially parallel to the main surface of the motion sensor element.

5. An arrangement as claimed in claim 2, characterized in that the coil arrangement and at least the sensor elements are arranged on a common substrate.

6. An arrangement as claimed in claim 1, characterized in that the sensor arrangement is formed with one half bridge comprising two bridge branches, each of which comprises at least one of the magnetoresistive sensor elements.

7. An arrangement as claimed in claim 1, characterized in that the sensor arrangement is formed with two half bridges each comprising two bridge branches, each of which comprises at least one of the magnetoresistive sensor elements.

8. An arrangement as claimed in claim 1, characterized in that the sensor elements have corresponding co-ordinates in the direction of at least a further co-ordinate axis which is substantially parallel to the main surface of the motion sensor element and at least substantially perpendicular to the measuring direction.