JP2007516437A - Magnet sensor device - Google Patents

Abstract

  A magnet sensor device having at least one magnetic field sensitive sensor layer in an integrated GMR spin valve multilayer system, wherein the magnetic field sensitive sensor elements (2, 3 ,; 4, 5; 10, 11; 12, 13) are one A magnet sensor device is proposed which is connected to a measuring bridge and whose resistance (R) of the sensor element varies depending on the external magnetic field. The sensor elements are each formed from at least one substantially linear measuring stripe (10, 11, 12, 13), each extending perpendicular to the direction of the magnetic field (H) to be detected. Yes.

Description

Prior Art The present invention relates to a magnet sensor device for sensing the movement of a linear or rotary element according to the superordinate concept of claim 1.

It is known that a so-called GMR sensor (GMR = Giant Magneto Resistance) as a magnetic field detection component can be applied as a relatively robust sensor when detecting a rotation angle in an automobile.
The action that occurs in a suitable layer system consisting of alternately magnetized and unmagnetized thin film metal layers is referred to as GMR. Here, the magnetic field to which the electrical resistance of the layer system is applied depends largely on spin-dependent electron scattering.

  For example, DE 10128135A1 describes the placement of a hard magnetic layer in the vicinity of, ie above and / or below, a magnetoresistive layer stack. This hard magnetic layer is exclusively coupled to the magnetoresistive layer by its stray magnetic field and at this time forms a so-called bias magnetic field. This bias magnetic field acts as a magnetic field offset, and even if the external magnetic field superimposed on the internal magnetic field changes very weakly, it can be measured well with the original measurement value, causing a relatively large change, which is the resistance in the layer system. Detected as a change.

It is also known from DE 1994 714 A1 to configure such a sensor as a so-called spin valve layer system. Here, the soft magnetic detection layer is separated from the hard magnetic layer by a non-magnetized intermediate layer.
Here, the non-magnetized intermediate layer has the following layer thickness. That is, the layer thickness is such that only a slight magnetic coupling occurs between the two magnetic layers via the non-magnetized intermediate layer. As a result, the magnetization direction of the soft magnetic detection layer can be determined by a very small external magnetic field.

As a GMR spin valve, there is basically a layer stack composed of at least four layers. Here the layer takes on the following roles:
1. A fully free layer following the applied magnetic field;
2. A non-magnetized intermediate layer between two magnetic layers involved in GMR action;
3. A fixed layer that is a magnetic layer and does not approach an external magnetic field to the limit;
4). One or more layers for fixing the fixing layer. The fourth layer can be an antiferromagnetic material, a plastic antiferromagnetic material, a combination thereof, a hard magnetic layer, or the like.

  The sensors described above are, as is known per se, often constituted by so-called magnetic field gradiometer systems, for example for rotational speed detection in automotive technology. That is, each two branches of the Wheatstone measurement bridge are arranged at a predetermined interval, so that a homogeneous magnetic field does not act on the bridge signal. On the other hand, a change in the magnetic field in a predetermined interval region forms a bridge signal. This causes the sensor to measure only the magnetic pole wheel signal. The pole pair interval of the pole wheel substantially corresponds to a predetermined magnetic field gradient meter interval.

  The same is true when using a steel wheel that is not itself ferromagnetic but modulates the magnetic field of a magnet mounted in the vicinity of the sensor with the magnetic susceptibility. Examples for such sensor wheels are toothed wheels or sensor wheels with protrusions and notches. Again, only the modulation of the magnetic field is measured on a scale of the magnetic gradient meter interval.

  In order to construct a magnetic field gradient meter based on a GMR spin valve, four measurement stripes made of GMR material are constructed in thin film technology. In order to make the bridge resistance appropriate for the evaluation electronics on the order of 1 kΩ, measurement stripes that are arranged in a meander shape are usually selected.

  Such a resistance change of the GMR spin valve structure is performed in a very narrow magnetic field region. This allows the spin valve structure itself to measure very small field strength modulations. However, when such a rotational speed sensor is used at a large operating interval, a homogeneous external magnetic field shifts the operating point of the GMR sensor, and the spin valve structure may not detect small magnetic field changes in the pole wheel or sensor wheel. Problems arise.

Advantages of the Invention Having at least one magnetic field sensitive sensor layer in an integrated spin valve multilayer system, the magnetic field sensitive sensor element is connected to a measurement bridge, the electrical resistance of the measurement bridge varying depending on the external magnetic field In an improvement of the magnet sensor device of the type mentioned at the outset, the invention advantageously provides that each sensor element is formed from at least a substantially linear measuring stripe, each measuring stripe being in each direction of the magnetic field to be detected. It extends vertically.

  According to an advantageous embodiment, each of the four sensor elements of GMR material mentioned at the beginning of the description is connected to the Wheatstone measuring bridge by thin film technology. Here, it is also advantageous if a plurality of measuring stripes are each connected in parallel for the formation of one sensor element. The measuring stripe here preferably has a width of about 2 to 10 μm.

  Therefore, the object of the present invention is that the direction of the magnetic field to be measured as a measuring stripe with a small width of several μm, in which the sensor element which depends on the magnetic field in terms of ohmic resistance is sufficiently linear instead of the usual meander shape in the prior art Orienting perpendicular to.

It is well known that the magnetic field in the magnetic body is different from the external magnetic field. This is because each magnetic body acts against the external magnetic field by its magnetization, and in particular, the internal magnetic field existing in the magnetic body acts so as to depend on the geometry of the magnetic body. In particular, the magnetic field penetrates weakly in a direction in which the spread is the smallest in a magnetic material whose dimensions vary greatly in three dimensions. Thereby, the magnetization advantageously points in the direction of the largest spread in the absence of an external magnetic field. As a result, the magnetization characteristic curve of a magnetic material that is normally magnetized completely homogeneously depends on the direction of the magnetic field with reference to its geometric shape.
In particular, in a thin film magnetic layer, it can be assumed that the characteristic curve of the magnetic field in the layer plane and the characteristic curve of the magnetic field perpendicular to the layer plane are clearly different. For this reason, decreasing the width of the measurement stripe in the direction perpendicular to the direction of the measurement magnetic field similarly changes the characteristic curve shape.

  The resistance change of the GMR spin valve structure described at the beginning occurs in a very narrow magnetic field region as described above. This allows the spin valve structure to measure very small magnetic field strength modulations. When the spin valve structure is used with a rotational speed sensor, this means that it has a very high sensitivity to the signal formed by the pole wheel or sensor wheel. In particular, magnetic field modulation can be reliably detected even when the operation interval is large.

  However, when such a rotational speed sensor is used at a large operation interval, a homogeneous external magnetic field shifts the operating point of the GMR sensor, and the spin valve structure cannot detect a small magnetic field change of the pole wheel or sensor wheel. Arise. The configuration of the measuring stripe according to the invention causes the characteristic curve to be inclined, which enlarges the sensitive area and at the same time reduces the maximum sensitivity corresponding to a small gradient of the characteristic curve.

  This advantageously allows the magnetic field sensor of the present invention to function reliably even if the disturbing magnetic field is homogeneous up to a predetermined maximum value. In particular, insensitivity to disturbance magnetic fields of ± 1 kA / m is guaranteed.

Drawings Next, embodiments of the present invention will be described in detail with reference to the accompanying drawings.
FIG. 1 is a basic diagram showing a layer structure of a measurement bridge circuit for a magnetic field sensor having a meander-shaped measurement stripe according to the prior art as a sensor element.
FIG. 2 is a diagram showing a characteristic curve of the electrical resistance of the sensor element, which depends on the magnetic field by a scheme that electromagnetically converts the modulated magnetic field into an electrical signal.
FIG. 3 is a diagram showing how the characteristic curve according to FIG. 2 is shifted by an external obstacle magnetic field.
FIG. 4 is a schematic diagram showing the magnetic field sensor of the present invention having a linear measurement stripe unlike FIG.
FIG. 5 is a schematic diagram showing another embodiment having a plurality of linear measurement stripes connected in parallel as a sensor element.
FIG. 6 is a diagram showing the characteristic curve of the inventive GMR spin valve measurement stripe according to FIG. 4 or 5, where the gradient is small and the characteristic curve is shifted by an external disturbing magnetic field.

DESCRIPTION OF EMBODIMENTS FIG. 1 shows a basic structure of a GMR magnetic field sensor 1 known in the prior art, and this magnetic field sensor is made of a multilayer structure or a multilayer structure. In order to sense the magnetic field changes mentioned at the beginning of the specification, known meandering measuring stripes 2, 3, 4 and 5 are provided as sensor elements, which are integrated and connected to a Wheatstone bridge circuit. Yes. Thereby, the resistance change depending on the magnetic field of the measurement stripes 2, 3, 4, 5 can be evaluated accordingly.

  FIG. 2 shows a characteristic curve 6 of the electrical resistance R of the measurement stripes 2, 3, 4, 5 depending on the magnetic field H. Therefore, in the characteristic curve 6, the signal 7 is converted into an electrical signal 8 corresponding to the modulated magnetic field to be sensed by the GRM spin valve structure of FIG.

  From FIG. 3, when the operation interval is excessively large in the rotational speed sensor (not shown), the homogeneous external magnetic field shifts the characteristic curve 6 and consequently the operating point of the GMR sensor as shown by the arrow 9, and the spin valve of FIG. It can be seen that the structure cannot detect small magnetic field changes due to the pole wheel of the rotational speed sensor or the signal 7 of the sensor wheel.

  The construction of the present invention with the linear measurement stripes 10, 11, 12, 13 as sensor elements is shown in FIGS. Here, the embodiment of FIG. 5 differs from the embodiment of FIG. 4 in that a parallel circuit of a plurality of individual measurement stripes is provided as a sensor element. The measurement stripes 10, 11, 12, 13 are made of giant magnetoresistive material (GMR) as described at the beginning of the specification and are connected to the Wheatstone measurement bridge in the same way as in the prior art by thin film technology. The individual measuring stripes 10, 11, 12, 13 preferably each have a width of about 2 to 10 μm.

  The characteristic curve 14 in FIG. 6 shows how the resistance R of the measurement stripes 10, 11, 12, 13 of the present invention shown in FIGS. It can be seen that the slope of the characteristic curve 14 is relatively small, unlike the characteristic curve 16 of FIGS. Due to this flat progress, even when the characteristic curve 14 is shifted by the external obstruction magnetic field as indicated by the arrow 15, the high sensitivity region is expanded.

FIG. 1 is a basic diagram showing a layer structure of a measurement bridge circuit for a magnetic field sensor having a meander-shaped measurement stripe according to the prior art as a sensor element. FIG. 2 is a diagram showing a characteristic curve of the electrical resistance of the sensor element, which depends on the magnetic field by a scheme for electromagnetically converting the modulated magnetic field into an electrical signal. FIG. 3 is a diagram showing how the characteristic curve according to FIG. 2 is shifted by an external obstacle magnetic field. FIG. 4 is a schematic diagram showing the magnetic field sensor of the present invention having a linear measurement stripe unlike FIG. FIG. 5 is a schematic diagram showing another embodiment having a plurality of linear measurement stripes connected in parallel as a sensor element. FIG. 6 is a diagram showing the characteristic curve of the inventive GMR spin valve measurement stripe according to FIG. 4 or 5, where the gradient is small and the characteristic curve is shifted by an external disturbing magnetic field.

Claims (5)

Magnet sensor device having at least one magnetic field sensitive sensor layer in an integrated spin-valve multilayer system, wherein the magnetic field sensitive sensor elements (2, 3 ,; 4, 5; 10, 11; 12, 13) have one measurement. In a magnet sensor device of a type that is connected to a bridge and whose resistance (R) of the sensor element changes depending on an external magnetic field (H),
Each sensor element is formed of at least one substantially linear measuring stripe (10, 11, 12, 13), each extending perpendicular to the direction of the magnetic field (H) to be detected. A magnet sensor device characterized by that. The magnet sensor device according to claim 1,
Magnet sensor device in which four measuring stripes (10, 11, 12, 13) each made of a giant magnetoresistive material (GMR) are connected to a Wheatstone measuring bridge. The magnet sensor device according to claim 1 or 2,
A magnet sensor device in which a plurality of measuring stripes (10, 11, 12, 13) are respectively connected in parallel to form a sensor element. In the magnet sensor device according to any one of claims 1 to 3,
Magnet sensor device in which the measurement stripes (10, 11, 12, 13) each have a width of about 2 to 10 μm. In the magnet sensor device according to any one of claims 1 to 4,
The magnet sensor device (1) is a magnet sensor device arranged as a magnetic field gradient meter for detecting the number of revolutions in a rotating component of an automobile.

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