JP2023124388A - magnetic sensor - Google Patents

Abstract

To provide a magnetic sensor suitable for applications which require high detection sensitivity such as a foreign matter detection system.SOLUTION: A magnetic sensor S1 includes: a sensor chip 40 having magnetic sensing elements R1 to R4 whose magnetic sensing direction is a y direction; a magnetism collecting body 51 which is arranged on an element forming surface 41 of the sensor chip 40 and whose longitudinal direction is an x direction; and a magnetic field generating conductor 20 which is arranged so as to surround the sensor chip 40 and the magnetism collecting body 51 and applies an AC magnetic field in a z direction to a detection object. Thus, since the AC magnetic field applied to the magnetic sensing elements R1 to R4 is reduced, saturation of the magnetic sensing element is made possible to be prevented even when the strong AC magnetic field is applied to the detection target.SELECTED DRAWING: Figure 2

Description

The present invention relates to a magnetic sensor, and more particularly to a magnetic sensor suitable for use in a foreign object detection system.

Patent Document 1 discloses a magnetic sensor including a sensor chip in which a magnetic collector is arranged on an element formation surface, and a magnetic field generating conductor that is provided so as to surround the sensor chip and applies an alternating magnetic field to an object to be detected. It is If a magnetic sensor having such a configuration is used, the strength of the alternating magnetic field changes depending on the presence or absence of the detection target, and by detecting this with the sensor chip, it is possible to detect the presence or absence of the detection target. Become.

WO2017/073280

However, in the magnetic sensor described in Patent Literature 1, the application direction of the AC magnetic field is the same as the magnetic collection direction of the magnetic collector, so a strong AC magnetic field is applied to the sensor chip. For this reason, in applications where a strong alternating magnetic field needs to be applied to an object to be inspected, such as when applied to a foreign matter detection system, the sensor chip becomes saturated, making it difficult to obtain high detection sensitivity. Ta.

SUMMARY OF THE INVENTION Accordingly, it is an object of the present invention to provide a magnetic sensor suitable for applications requiring high detection sensitivity, such as foreign object detection systems.

A magnetic sensor according to the present invention includes a sensor chip provided on an element forming surface and having a magnetosensitive element whose magnetic sensing direction is parallel to the element forming surface; and a magnetic field generating conductor disposed so as to surround the sensor chip and the first magnetic collector and applying an AC magnetic field to the object to be detected. The application direction is characterized by intersecting with the longitudinal direction of the first magnetic collector.

According to the present invention, since the alternating magnetic field applied to the magneto-sensitive element is reduced, it is possible to prevent saturation of the magneto-sensitive element even if a strong alternating magnetic field is applied to the object to be detected. Therefore, it can be suitably used for applications requiring high detection sensitivity, such as a foreign object detection system.

The magnetic sensor according to the present invention further includes a second magnetic collector disposed on the element forming surface of the sensor chip, and the first magnetic collector and the second magnetic collector are arranged in the first direction on the element forming surface. The longitudinal direction of the first magnetic collectors is the second direction perpendicular to the element forming surface, and the magneto-sensitive elements have the first direction as the magneto-sensitive direction and the second direction. It may be disposed between the first magnetic flux collector and the second magnetic collector when viewed from above, and the direction of application of the alternating magnetic field may be a third direction perpendicular to the first and second directions. According to this, the magneto-sensing direction of the magneto-sensing element, the magnetism-collecting direction of the first magnet collector, and the application direction of the alternating magnetic field are orthogonal to each other, so that saturation of the magneto-sensing element can be effectively prevented. Become.

In the present invention, the first magnetic collector has an upper surface extending in the first and second directions, and the upper surface may be substantially flush with the upper end of the magnetic field generating conductor in the third direction. . According to this, it is possible to obtain high detection sensitivity while suppressing the influence of disturbance noise.

The magnetic sensor according to the present invention may further comprise a compensating coil wound around the first magnetic collector so that the second direction is the coil axis direction. According to this, it becomes possible to perform so-called closed loop control.

Thus, according to the present invention, it is possible to provide a magnetic sensor that is suitable for applications that require high detection sensitivity, such as foreign object detection systems.

FIG. 1 is a schematic diagram for explaining the configuration of a foreign object detection system 1 according to one embodiment of the present invention. FIG. 2 is a schematic perspective view showing the appearance of the magnetic sensor S1. FIG. 3 is a schematic perspective view for explaining the structure of the sensor main body 10. As shown in FIG. FIG. 4 is a schematic exploded perspective view for explaining the structure of the sensor body 10. As shown in FIG. FIG. 5 is a schematic perspective view showing a state in which the magnetic yokes M1 to M3 are removed from the sensor chip 40. FIG. FIG. 6 is a schematic diagram for explaining the influence of metallic foreign matter. FIG. 7 is a schematic perspective view showing the appearance of a magnetic sensor S2 according to a modification.

Preferred embodiments of the present invention will now be described in detail with reference to the accompanying drawings.

FIG. 1 is a schematic diagram for explaining the configuration of a foreign object detection system 1 according to one embodiment of the present invention.

As shown in FIG. 1, the foreign matter detection system 1 according to the present embodiment conveys an object 3 to be inspected by a conveying mechanism consisting of a plurality of motor rollers 2 arranged in the x direction, while the object 3 to be inspected is metallized. This is a system that detects whether foreign matter is mixed in or not. The motor roller 2 is a roller that rotates around the y direction as a rotation axis, and the object to be inspected placed on the motor roller 2 is rotated in one direction by rotating the plurality of motor rollers 2 arranged in the x direction. 3 are transported in the x direction. In the example shown in FIG. 1, the object to be inspected 3 is conveyed using the motor roller 2, but the method of conveying the object to be inspected 3 is not limited to this, and other conveying methods such as a belt conveyor and a linear motor can be used. A mechanism may be used to transport the object 3 to be inspected.

A plurality of magnetic sensors S<b>1 are arranged in the middle of the transport path composed of a plurality of motor rollers 2 . As will be described later, the magnetic sensor S1 includes a magnetic field generating conductor for generating an alternating magnetic field and a sensor chip. Therefore, if the object to be inspected 3 contains a metallic foreign object such as iron (Fe), which is an object to be detected, a change occurs in the alternating magnetic field. contamination can be detected.

In the example shown in FIG. 1, a plurality of magnetic sensors S1 are arranged in the y direction, so that the inspection object 3 can be inspected over the entire width in the y direction. The number of magnetic sensors S1 may be appropriately selected according to the width of the motor roller 2 in the y direction. Instead of transporting the inspection object 3 using a transport mechanism such as the motor roller 2, the inspection may be performed by scanning the magnetic sensor S1 while the inspection object 3 is stationary. .

FIG. 2 is a schematic perspective view showing the appearance of the magnetic sensor S1.

As shown in FIG. 2, the magnetic sensor S1 includes a sensor main body 10 and magnetic field generating conductors 20 arranged to surround the sensor main body 10 . The magnetic field generating conductor 20 is a coil that applies an alternating magnetic field to the object 3 to be inspected, and the sensor main body 10 is arranged in the inner diameter region thereof. The coil axis direction of the magnetic field generating conductor 20 is the z direction.

3 and 4 are diagrams for explaining the structure of the sensor body 10. FIG. 3 is a schematic perspective view, and FIG. 4 is a schematic exploded perspective view.

As shown in FIGS. 3 and 4, the sensor body 10 includes a sensor chip 40 mounted on the surface of the sensor substrate 30 and magnetic collectors 51-53. The sensor chip 40 has a substantially rectangular parallelepiped shape, and has an element formation surface 41 and a back surface 42 forming a yz plane, an upper surface 43 and a lower surface 44 forming an xy plane, and side surfaces 45 and 46 forming an xz plane. The element forming surface 41 is a surface on which the magneto-sensitive element is formed. The sensor chip 40 is mounted on the sensor substrate 30 such that the lower surface 44 faces the sensor substrate 30 and the element forming surface 41 is perpendicular to the surface of the sensor substrate 30 . Magnetic yokes M1 to M3 made of permalloy or the like are formed on the element forming surface 41 of the sensor chip 40, and the magneto-sensitive elements are arranged in the vicinity of the magnetic gap formed by the magnetic yoke M1 and the magnetic yokes M2 and M3. be. As a result, magnetic flux passing through the magnetic gap is applied to the magneto-sensitive element.

FIG. 5 is a schematic perspective view showing a state in which the magnetic yokes M1 to M3 are removed from the sensor chip 40. FIG.

As shown in FIG. 5, on the element forming surface 41 of the sensor chip 40, magneto-sensitive elements R1 to R4 are formed. The magneto-sensitive elements R1 to R4 all have the magneto-sensitive direction in the y direction. The magneto-sensitive elements R1 and R2 are arranged near the magnetic gap formed by the magnetic yoke M1 and the magnetic yoke M2, and the magneto-sensitive elements R1 and R2 are arranged near the magnetic gap formed by the magnetic yoke M1 and the magnetic yoke M3. are placed in the vicinity of The magneto-sensitive elements R1 to R4 are bridge-connected between terminal electrodes 61 and 62, and a differential signal corresponding to the magnetic field appears at terminal electrodes 63 and 64. FIG.

The magnetic collectors 51 to 53 are blocks made of a magnetic material such as ferrite, and all of them serve to collect the magnetic field emitted from the object 3 to be inspected to the sensor chip 40 . The magnetic collectors 51 to 53 overlap the magnetic yokes M1 to M3, respectively, when viewed from the x direction. That is, the magnetic collectors 51 to 53 are arranged in the y-direction on the element forming surface 41, the magnetic sensing elements R3 and R4 are arranged between the magnetic collectors 51 and 52 as seen from the x direction, and the magnetic collector 51 is arranged as seen from the x direction. , 53, the magneto-sensitive elements R1 and R2 are arranged.

The magnetic flux collector 51 has its longitudinal direction in the x direction, and mainly serves to collect the magnetic field in the x direction to the magnetic yoke M1. The magnetic flux collector 52 has a portion covering the side surface 45 and the rear surface 42 of the sensor chip 40 , and the magnetic flux collector 53 has a portion covering the side surface 46 and the rear surface 42 of the sensor chip 40 . As a result, the x-direction magnetic field collected by the magnetic flux collector 51 is bent in the y-direction by the magnetic yoke M1 and flows to the magnetic flux collectors 52 and 53 via the magnetic yokes M2 and M3. Magnetic fields passing through the magnetic gaps between the magnetic yoke M1 and the magnetic yokes M2 and M3 are detected by the magneto-sensitive elements R1 to R4. In the examples shown in FIGS. 3 and 4, a compensating coil C is wound around the magnetic collector 51 . A canceling current flows through the compensating coil C so that the magnetic fields applied to the magneto-sensitive elements R1 to R4 are cancelled.

With such a configuration, the magnetic collecting direction (x direction) of the magnetic collecting bodies 51 to 53, the magnetic sensing direction (y direction) of the magnetic sensing elements R1 to R4, and the application direction (z direction) of the alternating magnetic field by the magnetic field generating conductor 20 are perpendicular to each other. This makes it difficult for the magneto-sensitive elements R1 to R4 to saturate due to the alternating magnetic field from the magnetic field generating conductor 20, so that a strong alternating magnetic field can be applied to the inspected object 3, and high detection sensitivity can be obtained. becomes.

Here, the direction of the alternating magnetic field applied by the magnetic field generating conductor 20 is the z direction, but as shown in FIG. , the x-direction component of the circulating magnetic flux can be collected by the magnetic collectors 51-53 and applied to the magneto-sensitive elements R1-R4. In FIG. 6, a point indicated by reference numeral 4 indicates a metallic foreign matter such as iron (Fe) contained in the inspection object 3, and an arrow indicated by reference numeral 5 indicates the direction and strength of the magnetic field generated by the metallic foreign matter. there is

In order to detect metal foreign matter such as iron (Fe) contained in the inspected object 3 with higher sensitivity, it is preferable to shorten the distance between the inspected object 3 and the magnetic sensor S1 in the z direction as much as possible. In particular, the xy upper surface 51a of the magnetic flux collector 51 and the upper end 20a (see FIG. 2) of the magnetic field generating conductor 20 in the z direction form substantially the same plane, thereby efficiently applying the AC magnetic field to the inspection object 3. It is possible to reduce the influence of disturbance noise.

FIG. 7 is a schematic perspective view showing the appearance of a magnetic sensor S2 according to a modification.

As shown in FIG. 7, in the magnetic sensor S2 according to the modification, the direction of magnetism collection by the magnetism collectors 51 to 53 is the x direction, the magnetism sensing direction of the magnetism sensing elements R1 to R4 and the application direction of the alternating magnetic field by the magnetic field generating conductor 20. 1 is different from the magnetic sensor S1 described above in that the sensor body 10 and the magnetic field generating conductor 20 are arranged so that the direction is in the z direction. Even with such a configuration, since the direction in which the alternating magnetic field is applied is different from the direction in which the magnetism collectors 51 to 53 collect magnetism, the magnetosensitive elements R1 to R4 are less likely to saturate.

Although the preferred embodiments of the present invention have been described above, the present invention is not limited to the above-described embodiments, and various modifications can be made without departing from the gist of the present invention. Needless to say, it is included within the scope.

1 foreign matter detection system 2 motor roller 3 object to be inspected 4 metal foreign matter 5 magnetic field 10 sensor body 20 magnetic field generating conductor 20a upper end 30 of magnetic field generating conductor sensor substrate 40 sensor chip 41 element forming surface 42 rear surface 43 upper surface 44 lower surface 45, 46 Sides 51-53 Magnetic collector 51a Magnetic collector top 61-64 Terminal electrode C Compensation coils M1-M3 Magnetic yokes R1-R4 Magneto-sensitive elements S1, S2 Magnetic sensors

Claims (4)

a sensor chip having a magneto-sensitive element provided on an element-formed surface and having a magneto-sensing direction parallel to the element-formed surface;
a first magnetic collector disposed on the element forming surface of the sensor chip and having a longitudinal direction intersecting with the element forming surface;
a magnetic field generating conductor arranged to surround the sensor chip and the first magnetic collector and applying an alternating magnetic field to an object to be inspected;
A magnetic sensor, wherein a direction in which the alternating magnetic field is applied intersects the longitudinal direction of the first magnetic collector. further comprising a second magnetic collector disposed on the element forming surface of the sensor chip;
the first magnetic flux collector and the second magnetic flux collector are arranged in a first direction on the element forming surface;
the longitudinal direction of the first magnetic collector is a second direction perpendicular to the element forming surface,
The magneto-sensitive element has the first direction as a magnetism-sensing direction, and is disposed between the first magnetic collector and the second magnetic collector when viewed from the second direction,
2. The magnetic sensor according to claim 1, wherein the application direction of said alternating magnetic field is a third direction perpendicular to said first and second directions. The first magnetic collector has an upper surface extending in the first and second directions,
3. The magnetic sensor according to claim 1, wherein the upper surface forms substantially the same plane as the upper end of the magnetic field generating conductor in the third direction. 4. The magnetic sensor according to any one of claims 1 to 3, further comprising a compensating coil wound around the first magnetic collector so that the second direction is the axial direction of the coil.

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