JP3961809B2 - Magnetic sensor element - Google Patents

Description

[0001]
BACKGROUND OF THE INVENTION
The present invention relates to a magnetic proximity switch, and more particularly to a magnetic proximity switch for detecting an origin in a reciprocating operation.
[0002]
[Prior art]
Conventionally, a latch circuit, a latching relay, or the like has been a general method for performing a self-holding operation of the proximity switch detection signal.
[0003]
[Problems to be solved by the invention]
However, the conventional method using a latch circuit or a latching relay has a drawback that the previous state cannot be reproduced when the power is turned off and then on again.
The present invention has been made to cope with the above-described drawbacks, and the number of components necessary for the self-holding operation is small, and even after the power is turned off without using a component such as the latch circuit. An object of the present invention is to provide a magnetic sensor element for use in a self-holding magnetic sensor that can reproduce the previous state upon re-entry.
[0004]
[Means for Solving the Problems]
In order to solve the above-described problem, in the present invention according to claim 1, a magnetoresistive element in which a ferromagnetic thin film magnetoresistive pattern is bridge-connected in a substantially orthogonal direction, and the magnetoresistive pattern on the magnetoresistive element. In either case, a coercive force is applied in a direction that is close to the side of the magnetoresistive element and is substantially perpendicular to the magnetic pole direction of the bias magnet. Provided is a magnetic sensor element in which a magnetic material of 1000 to 3000 A / m is disposed.
According to a second aspect of the present invention, there is provided the magnetic sensor element according to the first aspect, wherein two or more magnetic materials are arranged with the magnetoresistive element interposed therebetween.
[0005]
DETAILED DESCRIPTION OF THE INVENTION
Hereinafter, embodiments of the magnetic sensor element of the present invention will be described with reference to the drawings.
[0006]
FIG. 1 is an exploded view of a magnetic sensor element according to the present invention. The magnetoresistive element (101) is formed in a bridge shape so that the elements of the magnetoresistive pattern (1011) are orthogonal to each other, and the magnetoresistive pattern (1011) is covered with a protective substance.
[0007]
The bias magnet (102) is attached and fixed on the magnetoresistive element (101) with an epoxy resin or the like so that a magnetic field of approximately 45 degrees is applied to any of the magnetoresistive patterns (1011).
[0008]
The magnetic material (1031, 1032) is attached to the magnetoresistive element (101) so as to be substantially in contact with the bias magnet (102) with the magnetoresistive pattern (1011) interposed therebetween, and is fixed with an epoxy resin or the like.
[0009]
FIG. 2 shows a magnetic sensor element (200) in which the magnetoresistive element (101), the bias magnet (102), and the magnetic material (1031, 1032) are integrated.
[0010]
FIG. 3 shows the magnetic sensor element (200) of FIG. 2 and the magnet (301) to be detected arranged at an interval d, and the direction in which the magnet (301) is moved is indicated by an arrow.
[0011]
FIG. 4 shows the magnetic flux density with respect to the distance from the magnetic pole center in the direction orthogonal to the magnetic pole direction, with the distance (d) from the magnetic pole surface of the single magnet to be detected (301) in FIG. 3 as a parameter. On the other hand, a detection output waveform of the magnetic sensor element (200) in FIG. 3 with respect to the detection target magnet (301) is shown in FIG.
[0012]
In FIG. 5, even when the distance (X) from the magnetic pole center in the direction orthogonal to the magnetic pole direction of the magnet is sufficiently far away, the magnetic sensor element output maintains a positive value on the positive X side, and the magnetic sensor on the negative X side. The element output has a characteristic of maintaining a negative value.
[0013]
The magnetic sensor element output graph shown in FIG. 5 is different from the graph of FIG. 4 because a magnetic material is added to the magnetoresistive element with a bias magnet, which will be described in more detail below.
[0014]
The output voltage waveform corresponding to FIG. 5 of the magnetoresistive element with a bias magnet when the magnetic material is not attached is as shown in FIG. 6, regardless of the magnitude of the magnetic field strength in the middle, and any magnetic field source magnet moves away. In this case, since the output is close to zero, the self-holding operation intended by the present invention is not achieved as it is.
[0015]
The operation when the magnetic material is mounted so as to sandwich the magnetoresistive element with a bias magnet differs depending on the magnetic characteristics of the magnetic material.
[0016]
(For soft magnetic materials)
As shown in FIG. 7, due to the magnetic material collection effect, the sensitivity increases, and the waveform rises sharply. However, when the magnet to be detected is moved away and the magnetic field is nearly zero, the magnetization of the magnetic material becomes smaller. As in the case of no material, the output approaches nearly zero, but the residual value of magnetization depends on the coercive force, and decreases as the coercive force decreases.
[0017]
(In the case of hard magnetic materials (materials for magnets))
As shown in FIG. 8, the characteristics are almost the same as in the case where there is no magnetic material (FIG. 6). (Generally, hard magnetic materials for magnets (for example, ferrite) have a very large coercive force (130 KA / m or more) and cannot be magnetized by ordinary magnetized ferrite magnets, etc., so that there is no magnetic material. Will be.)
[0018]
(For magnetic materials with intermediate magnetic hardness)
This corresponds to the case of the present invention shown in FIG. 5, and the target magnetic material is magnetized to the extent of a normal magnetized ferrite magnet and has an appropriate coercive force. A phenomenon in which magnetization remains in the target magnetic material is used.
An important point here is whether or not an operating magnetic material can be selected with a practical operating distance (around 5 mm) between the magnet to be detected and the sensor.
[0019]
FIG. 9 is a graph comparing the coercivity of various materials. From the graph of FIG. 4, a magnetic material that operates at a magnetic flux density of 5 to 10 mT is selected in consideration of the magnetic flux density with respect to the distance from a practical magnet. In order to magnetize a magnetic material, a magnetizing force that is 2.5 times or more of the coercive force is required. 40% of this value is 1600 to 3200 A / m, and a material having a coercive force equal to or less than this value cannot be used because it becomes unstable magnetization.
[0020]
In addition, if the coercive force is too small, there is a risk of malfunction such as magnetization reversal due to the influence of the peripheral magnetic field, so the coercive force is preferably in the range of 1000 to 3000 A / m. As such a magnetic material, for example, S60C or SUS631 can be used as shown in FIG. The material used in the embodiment of the present invention is S60C whose coercive force in the graph of FIG. 9 is approximately 1600 A / m.
[0021]
【The invention's effect】
The magnetic sensor element of the present invention includes a magnetoresistive element in which a ferromagnetic thin film magnetoresistive pattern is bridge-connected in a substantially orthogonal direction, and on the magnetoresistive element, the magnetoresistive pattern has an angle of approximately 45 degrees. A magnetic material having a coercive force of 1000 to 3000 A / m in a direction substantially perpendicular to the magnetic pole direction of the bias magnet, in proximity to the side of the magnetoresistive element, and a bias magnet mounted to apply a magnetic field in the direction. It is the arranged configuration.
Therefore, there is no need for parts such as a latch circuit, the number of components required for self-holding operation is small, and the self-holding type can reproduce the previous state when the power is turned on again after power-off. It can be used effectively for magnetic sensors.
[Brief description of the drawings]
FIG. 1 is an exploded view of a magnetic sensor element.
FIG. 2 is a perspective view of a magnetic sensor element.
FIG. 3 is a perspective view of a magnetic sensor element and a detection target magnet.
FIG. 4 is a diagram showing a magnetic flux density in a direction orthogonal to a magnetic pole direction of a detection target magnet.
FIG. 5 is a diagram showing a magnetic sensor element output (related to the present invention) in a direction orthogonal to a magnetic pole direction of a detection target magnet.
FIG. 6 is a diagram showing a magnetoresistive element output with a bias magnet in a direction orthogonal to a magnetic pole direction of a magnet to be detected.
FIG. 7 is a diagram showing a magnetic sensor element output in a direction perpendicular to the magnetic pole direction of a magnet to be detected (when the magnetic material is SPCC for comparison with the present invention).
FIG. 8 is a diagram showing a magnetic sensor element output in a direction orthogonal to a magnetic pole direction of a magnet to be detected (for comparison with the present invention, when a magnetic material is a ferrite for a magnet).
FIG. 9 is a diagram showing coercive force by type of magnetic material.
[Explanation of symbols]
101 Magnetoresistive element 102 Bias magnet 1011 Magnetoresistive pattern 1031 Magnetic material 1032 Magnetic material

Claims (2)

A magnetic field should be applied to the magnetoresistive element in which the ferromagnetic thin film magnetoresistive pattern is bridge-connected in a substantially orthogonal direction and to the magnetoresistive element at an angle of approximately 45 degrees. A magnetic sensor element in which a magnetic material having a coercive force of 1000 to 3000 A / m is disposed in a direction substantially perpendicular to the magnetic pole direction of the bias magnet in the vicinity of the attached bias magnet and the side of the magnetoresistive element. The magnetic sensor element according to claim 1, wherein two or more magnetic materials are arranged with the magnetoresistive element interposed therebetween.

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