JP2019211334A - Core structure and strain detector for detecting change of magnetic permeability - Google Patents

Abstract

To provide a core structure and a strain detector which can be manufactured more easily for detecting a change of the magnetic permeability of a detection target member for all over the periphery of the member.SOLUTION: The core structure includes an annular core 30 containing a magnetic body and a detection coil 42. The core structure is used to detect a change of the magnetic permeability of a magnetic strain part 22. The core 30 can be defined in the axial direction, the radial direction, and the circumferential direction. The core 30 has at least four teeth protruding in the radial direction. A plurality of magnetic paths are formed through the magnetic strain part 22 and two teeth. The magnetic paths cover the entire magnetic strain part 22 in the circumferential direction.SELECTED DRAWING: Figure 3

Description

  The present invention relates to a core structure and a strain detection device, and more particularly to a device used for detecting a change in magnetic permeability of a detection target member.

  Devices that detect changes in magnetic permeability and operate using them are known. For example, a torque applied to the magnetostrictive material can be detected based on a change in the magnetic permeability of the magnetostrictive material using a magnetostrictive material and utilizing the Villari effect.

  In such a device, characteristics such as sensitivity may vary greatly in the circumferential direction due to the influence of variations in the circumferential direction due to eccentricity and characteristics of the magnetostrictive material. In such a case, a configuration for detecting a change in permeability of the detection target member over the entire circumference is known in order to relax the variation condition and increase the detection accuracy. For example, in the configuration of Patent Document 1, U-shaped cores are arranged in the circumferential direction to detect the magnetic permeability of the entire circumference of the rotating shaft, and the value of distortion generated on the rotating shaft is calculated.

JP 2010-8296 A

  However, the conventional method has a problem that it is difficult to manufacture the core. For example, in the configuration of Patent Document 1, since the U-shaped cores are separate members, a large number of cores need to be precisely aligned and arranged, which complicates the core assembly process.

  The present invention has been made to solve such problems, and a core structure and strain detection device for detecting a change in permeability of a detection target member over the entire circumference can be more easily manufactured. The purpose is to provide.

A core structure according to the present invention is a core structure that includes an annular core including a magnetic body and a detection coil, and is used to detect a change in magnetic permeability of a detection target member.
Axial direction, radial direction and circumferential direction can be defined for the core,
The core includes at least four teeth protruding in a radial direction,
A plurality of magnetic paths through the detection target member and the two teeth are formed,
The plurality of magnetic paths are formed so as to cover the entire circumferential range in the detection target member.
According to a specific aspect, the plurality of teeth constitutes a plurality of tooth stages provided at different positions in the axial direction, and each tooth is provided at equal intervals in the circumferential direction.
According to a particular aspect,
The first teeth stage and the second teeth stage are arranged so that the circumferential positions of the teeth are staggered,
For each tooth of the first teeth stage, a first magnetic path is formed between the teeth and the teeth of the second teeth stage adjacent to one side in the circumferential direction of the teeth, and the teeth and A second magnetic path is formed between the teeth of the second teeth step adjacent to the opposite side of the teeth in the circumferential direction,
The portions of the first magnetic path and the second magnetic path that pass through the tooth of the first tooth stage have the same direction.
According to a specific aspect, each tooth is disposed such that a portion of each magnetic path formed in the detection target member forms an angle of 45 degrees with respect to the axial direction.
According to a particular aspect,
The core structure further includes an exciting coil,
The plurality of teeth constitute a plurality of teeth rows provided at different positions in the circumferential direction,
The detection coil is wound around each tooth of the first tooth row,
The detection coil is not wound around each tooth of each tooth row adjacent to both sides in the circumferential direction of the first tooth row, and the exciting coil is wound.
According to a specific aspect, three or more teeth stages are provided, and the teeth stages are provided at equal intervals in the axial direction.
In addition, a strain detection apparatus according to the present invention includes the above-described core structure and the detection target member including a cylindrical or cylindrical magnetostrictive member.

  According to the core structure and the strain detection device according to the present invention, the core can be manufactured more easily.

It is a figure which shows the example of a structure of the distortion detection apparatus which concerns on Embodiment 1 of this invention. It is a perspective view of the core of FIG. It is the schematic which shows the positional relationship of each teeth and a magnetic path. It is a figure which shows the example of the outline of the magnetic path formed in a magnetostriction part. FIG. 10 is a schematic diagram showing a positional relationship between each tooth and a magnetic path in a modification of the first embodiment. 6 is a schematic diagram showing a positional relationship between each tooth and a magnetic path in Embodiment 2. FIG. FIG. 10 is a schematic diagram showing a positional relationship between each tooth and a magnetic path in a modified example of the second embodiment.

Embodiments of the present invention will be described below with reference to the accompanying drawings.
Embodiment 1 FIG.
FIG. 1 shows an example of the configuration of a strain detection apparatus 10 according to Embodiment 1 of the present invention. FIG. 1 is an end view of a cut portion by a plane including the axis A of the shaft member 20. The strain detection apparatus 10 includes a shaft member 20 and a core 30. In this embodiment, the shaft member 20 is formed in a substantially cylindrical shape, and is configured so that at least a part thereof can be distorted around the axis A. For example, in the shaft member 20, when the other end rotates around the axis A with respect to one end in the axial direction, distortion occurs so as to be twisted.

  The shaft member 20 includes a magnetostrictive material. In the present embodiment, the magnetostrictive material is molded as the magnetostrictive portion 22. In the example of FIG. 1, the shaft member 20 includes a shaft 21, and the magnetostrictive portion 22 is provided on the outer side in the radial direction of the shaft 21 so as to surround the shaft 21. The magnetostrictive portion 22 is formed, for example, in a cylindrical shape or a cylindrical surface shape.

  The shaft member 20 and the magnetostrictive portion 22 are detection target members whose distortion is detected. In accordance with the distortion of the magnetostrictive portion 22, the magnetization state of the magnetostrictive portion 22 changes due to the barrier effect. In particular, the magnetic permeability of the magnetostrictive portion 22 in a specific direction changes, and this change can be detected. Further, by detecting a change in the magnetic permeability in the magnetostrictive portion 22, for example, the magnitude of the distortion of the shaft member 20 can be calculated, and for example, the magnitude of the torque applied to the shaft member 20 can be calculated. Can do.

  The core 30 is formed in an annular shape. An axial direction, a radial direction, and a circumferential direction can be defined for the core 30. In the present embodiment, the axial direction of the core 30 coincides with the axial direction of the shaft member 20, and in particular, the axis of the core 30 and the axis of the shaft member 20 coincide (the axis of the core 30 is the axis A).

  In a state where there is no distortion (for example, a state where no torque is applied to the shaft member 20), the magnetostrictive portion 22 is relatively strongly magnetized in a direction parallel to the axis A (or a magnetic domain magnetized in that direction grows). . Here, when the shaft member 20 is distorted due to the torque being applied to the shaft member 20, the magnetostrictive portion 22 is relatively strongly magnetized in a direction not parallel to the axis A (or magnetized in that direction). Magnetic domains grow). Thus, when the direction of magnetization of the magnetostrictive portion 22 changes, the magnetic permeability of the magnetostrictive portion 22 in a specific measurement direction changes accordingly. It can be said that the strain detection apparatus 10 is an apparatus that detects such a change in magnetic permeability.

  FIG. 2 is a perspective view of the core 30. The core 30 includes a magnetic body at least in part, and includes a substantially cylindrical surface-shaped yoke 31 and at least four teeth. The teeth are formed so as to protrude from the yoke 31 in the radial direction (in the present embodiment, radially inward). The yoke 31 and each tooth are integrally formed in the present embodiment, but may be formed and combined as separate members. It should be noted that the shapes of the yoke 31 and the teeth shown are not strict.

  The core 30 is a multistage slot core and includes a plurality of teeth stages. For example, in the example of FIG. 2, a teeth stage T1 (first teeth stage; see also FIG. 3 etc.) including teeth T11, teeth T12, teeth T13, teeth T14, teeth T15 and teeth T16, teeth T21, teeth T22, teeth. A tooth stage T2 (second tooth stage, see FIG. 3 and the like) including T23, teeth T24, teeth T25, and teeth T26 is configured. Of these, the teeth T11 and the teeth T14 also appear in the cut end view of FIG.

  Each tooth stage is provided at a different position in the axial direction. Teeth belonging to the same tooth stage are provided at the same axial position. When viewed in the direction shown in FIG. 1, the teeth stage T1 (the teeth T11 and teeth T14 in FIG. 1) is arranged on the upper side of the sheet, and the teeth stage T2 (not appearing in FIG. 1) is arranged on the lower side of the sheet. Further, each tooth stage is provided with equal intervals in the circumferential direction. In the example of FIG. 2, each tooth stage includes six teeth, and therefore the interval between adjacent teeth in the circumferential direction (for example, the interval between the teeth T11 and T12) is 60 degrees.

  Moreover, in this embodiment, the teeth stage T1 and the teeth stage T2 are arrange | positioned so that the circumferential direction position of teeth may become alternate. That is, at the circumferential position, the tooth T21 of the teeth stage T2 is disposed at a position separated by 30 degrees from both the teeth T11 and the teeth T12 of the teeth stage T1.

  FIG. 3 schematically shows the positional relationship between each tooth and the magnetic path. FIG. 3 shows a state in which the core 30 is developed in the circumferential direction, and the circumferential direction of the core 30 corresponds to the horizontal direction of the drawing. Each tooth forms a pair of teeth as indicated by a double-pointed arrow (however, one tooth forms a different tooth and a plurality of pairs of teeth). Each pair of teeth forms one magnetic path. As a result, a plurality of magnetic paths through the magnetostrictive portion 22 and the two teeth are formed. In the present embodiment, pairs of teeth forming one magnetic path belong to mutually different tooth stages. In the core 30, an exciting coil 41 and a detection coil 42 are wound around each tooth, thereby forming a core structure.

  The functions of the excitation coil 41 and the detection coil 42 are well known. For example, the excitation coil 41 is a coil for generating a magnetic field in order to detect a change in magnetic permeability in the magnetostrictive portion 22, and the detection coil 42 is This is a coil for detecting a magnetic field generated by the exciting coil 41 in order to detect a change in magnetic permeability in the magnetostrictive portion 22. Using these coils, it is possible to detect a circumferential distortion with respect to the shaft member 20.

  The magnetic path is formed so as to cover the entire circumferential range in the magnetostrictive portion 22 (strictly speaking, the position where the teeth are arranged may be removed according to the thickness of the teeth). For example, regarding the tooth T12 of the teeth stage T1 (first teeth stage), between this tooth T12 and the teeth T21 of the teeth stage T2 (second teeth stage) adjacent to one side in the circumferential direction (for example, the left side in FIG. 3) Thus, the magnetic path M1 (first magnetic path) is formed. On the other hand, a magnetic path M2 (second magnetic path) is formed between the tooth T12 and the tooth T22 of the tooth stage T2 adjacent to the opposite side in the circumferential direction (for example, the right side in FIG. 3). Similarly, two such magnetic paths are formed for each tooth of the tooth stage T1. In the example of FIG. 3, since the tooth stage T1 and the tooth stage T2 are symmetrical, it can be said that two magnetic paths are formed for each tooth of the tooth stage T2.

  Of these two magnetic paths (for example, magnetic paths M1 and M2 passing through the teeth T12), the portions passing through the teeth T12 have the same magnetic flux direction. A specific coil winding method and voltage application method for forming such a magnetic path can be appropriately designed by a person skilled in the art based on a known strain detection device or the like, and an example will be described below. . For example, if the exciting coil 41 is wound around each tooth of the tooth stage T1 so as to have a different phase between adjacent teeth, and the detection coil 42 is wound around each tooth of the tooth stage T2 so as to have a different phase, Parts of the magnetic path M1 and the magnetic path M2 that pass through the teeth T12 are in the same direction. In this way, five magnetic paths (12 magnetic paths including those not shown in FIG. 3) are formed as shown in FIG.

  Thus, the core 30, the exciting coil 41, and the detection coil 42 constitute the core structure according to the first embodiment. A change in the magnetic permeability of the shaft member 20 can be detected using this core structure.

  FIG. 4 shows a schematic example of the magnetic path M <b> 1 formed in the magnetostrictive portion 22. Actually, the entire magnetic path M1 is not included in the paper surface, but FIG. 4 shows that the magnetic path M1 is projected onto the paper surface (that is, a plane including the axis A). Further, the shaft member 20 has a substantially cylindrical shape and is rounded. However, since the shaft member 20 is regarded as a flat surface in FIG.

  The teeth T12 and the teeth T21 schematically show only the positions of the tips. As described above, since the teeth stage T1 and the teeth stage T2 are arranged so that the circumferential positions of the teeth are staggered, the magnetostrictive portion 22 of the magnetic path M1 formed through the teeth T11 and the teeth T21. As shown in the drawing, the portion formed inside extends in an oblique direction with respect to the axial direction (that is, a direction that is neither parallel nor perpendicular to the axial direction). In particular, in this embodiment, the part formed in the magnetostriction part 22 among the magnetic paths M1 makes 45 degree | times with respect to an axial direction. This direction is a measurement direction for measuring the magnetic permeability of the magnetostrictive portion 22. That is, if the magnetostrictive portion 22 is magnetized in a direction close to this direction, the magnetic permeability measured through the magnetic path M1 increases, and the magnetostrictive portion 22 is magnetized in a direction different from this direction (for example, a direction orthogonal). If it does so, the magnetic permeability measured via the magnetic path M1 will become small.

  As described above, according to the strain detection apparatus 10 according to the first embodiment of the present invention, since the number of parts of the core 30 is relatively small (for example, since it is a single member), the manufacture of the core 30 becomes easier. . Further, there is a possibility that the core 30 can be made more compact, and there is a possibility that the shape accuracy of the core 30 can be improved.

  In addition, according to the strain detection device 10, the magnetic path is formed in a manner that is as uninterrupted as possible so as to cover the entire circumferential range in the magnetostriction portion 22, so that the permeability change of the magnetostriction portion 22 is detected over the entire circumference. be able to. For this reason, the influence by the variation of the circumferential direction by the characteristic of eccentricity or a magnetostrictive material is reduced.

  Further, the magnetic paths adjacent to each other (for example, the magnetic path M1 and the magnetic path M2) are formed so as to be inclined opposite to each other with respect to the axial direction. In the present embodiment, as shown in FIG. 3, the magnetic path M1 forms an angle of 45 degrees with respect to the axial direction, and the magnetic path M2 forms an angle of 45 degrees on the opposite side of the magnetic path M1 with respect to the axial direction. It is arranged as follows. For this reason, the influence of the change in the magnetic permeability in a certain direction on the magnetic path M1 is different from the influence on the magnetic path M2 (for example, the increase and decrease of the magnetic flux are opposite to each other), and the direction and magnitude of the distortion are correctly detected. Can do. Therefore, an additional configuration (such as a configuration for imparting magnetic anisotropy to the detection target member) for detecting the strain direction is unnecessary, and cost and man-hours can be saved.

In the first embodiment, the following modifications can be added.
In Embodiment 1, six teeth are provided in each tooth stage, but the effect of the present invention can be obtained if there are at least two teeth in each tooth stage.

  In Embodiment 1, two teeth stages are formed, but three or more teeth stages may be formed. When three or more teeth stages are provided, the teeth stages may be provided at equal intervals in the axial direction.

  FIG. 5 schematically shows a configuration of teeth and magnetic paths in the case where four or more teeth stages are provided in such a modification. In FIG. 5, a square represents a tooth, and a bidirectional arrow represents a magnetic path.

  In the first embodiment, as shown in FIG. 4, the portion of each magnetic path formed in the magnetostrictive portion 22 forms 45 degrees with respect to the axial direction. Is possible. In other words, the portion formed in the magnetostrictive portion 22 of the magnetic path only needs to extend in a direction that is neither parallel nor perpendicular to the axis A. However, the magnetic paths adjacent to each other (for example, the magnetic path M1 and the magnetic path M2) need to be formed to form equal angles opposite to each other in the axial direction.

Embodiment 2. FIG.
The second embodiment changes the arrangement of teeth and coils in the first embodiment. Hereinafter, differences from the first embodiment will be described.

  FIG. 6 schematically shows the positional relationship between each tooth and the magnetic path. FIG. 6 illustrates a state in which the core according to the second embodiment is developed in the circumferential direction in the same manner as in FIG. 3, and the circumferential direction of the core corresponds to the horizontal direction of the drawing. Each tooth forms a pair of teeth as shown by a bidirectional arrow, and each pair of teeth forms one magnetic path. As will be described later, in the present embodiment, magnetic paths that are not used for detecting a change in magnetic permeability are not shown.

  The core according to Embodiment 2 is a multi-stage slot core and includes a plurality of teeth stages. FIG. 6 shows teeth stages T5 and T6. Teeth stage T5 includes teeth T5a, teeth T5b, teeth T5c and teeth T5d, and teeth stage T6 includes teeth T6a, teeth T6b, teeth T6c and teeth T6d.

  The core according to the second embodiment includes a plurality of tooth rows. FIG. 6 shows a teeth row Ta, a teeth row Tb, a teeth row Tc, and a teeth row Td. The teeth row Ta includes the teeth T5a and the teeth T6a, the teeth row Tb includes the teeth T5b and the teeth T6b, the teeth row Tc includes the teeth T5c and the teeth T6c, and the teeth row Td includes the teeth T5d and the teeth T6d.

  Each tooth row is provided at a different position in the circumferential direction. Further, the teeth belonging to the same tooth row are provided at the same circumferential position. Thus, in Embodiment 2, the teeth are arranged in a lattice pattern.

  An excitation coil 41 and a detection coil 42 are alternately wound around each tooth row. For example, the exciting coil 41 is wound around the odd-numbered tooth row, and the detection coil 42 is wound around the even-numbered tooth row. More specifically, the exciting coil 41 is wound around the teeth T5a and T6a, the detection coil 42 is wound around the teeth T5b and the teeth T6b, and the exciting coil 41 is wound around the teeth T5c and the teeth T6c. The detection coil 42 is wound around the teeth T5d and T6d.

  Here, paying attention to the tooth row Tb, the detection coil 42 is wound around each tooth of the tooth row Tb (first tooth row) (that is, the teeth T5b and T6b), and the adjacent teeth on both sides in the circumferential direction of the tooth row Tb. The detection coil 42 is not wound around each tooth of the teeth row (that is, the tooth rows Ta and Tc), but the exciting coil 41 is wound. More specifically, the exciting coil 41 is wound around each tooth (that is, teeth T5a and T6a) of the tooth row Ta (second tooth row) adjacent to the circumferential direction side (left side in FIG. 6) of the tooth row Tb. It can be said that the exciting coil 41 is wound around each tooth (that is, teeth T5c and T6c) of the teeth row Tc (third teeth row) adjacent to the teeth row Tb on the opposite side in the circumferential direction (right side in FIG. 6). .

  Further, the exciting coil 41 is wound so that the phases are alternated in each row. For example, when the exciting coil 41 is wound around the odd-numbered tooth row, the exciting coil 41 is wound around the (4n + 1) th tooth row with the positive phase, and the opposite is applied to the (4n + 3) th tooth row. The exciting coil 41 is wound in phase. More specifically, the exciting coil 41 of the tooth row Tc is wound with a phase opposite to that of the exciting coil 41 of the tooth row Ta. For this reason, a magnetic path passing through the tooth row Ta, the magnetostrictive portion 22, the tooth row Tc, and the yoke of the core is formed. Since this magnetic path does not pass through the tooth (for example, the tooth row Tb or the tooth row Td) around which the detection coil 42 is wound, it is not a detection target, and is not shown in FIG.

  When distortion occurs in the magnetostrictive portion 22, the magnetic permeability in a specific oblique direction (for example, the direction from the teeth T5b toward the lower left tooth T6a) is orthogonal to the direction (for example, from the teeth T5b to the lower right tooth T6c). Direction). For this reason, as indicated by a bidirectional arrow in FIG. 6, a magnetic flux is generated that passes through the tooth (for example, the tooth T5b) around which the detection coil 42 is wound. By detecting this magnetic flux, a change in the magnetic permeability in the magnetostrictive portion 22 can be detected.

  As described above, the strain detection apparatus according to the second embodiment of the present invention also makes it easier to manufacture the core because the number of core components is relatively small (for example, a single member). Moreover, there is a possibility that the core can be made more compact, and there is a possibility that the shape accuracy of the core can be improved.

  Also in the second embodiment, the magnetic path is formed in a manner that is as uninterrupted as possible so as to cover the entire circumferential range in the magnetostrictive portion 22, so that the permeability change of the magnetostrictive portion 22 can be detected over the entire circumference. it can. For this reason, the influence by the variation of the circumferential direction by the characteristic of eccentricity or a magnetostrictive material is reduced.

  Also in the second embodiment, since magnetic paths that are inclined opposite to each other in the axial direction are formed, the direction and magnitude of distortion can be detected correctly. Therefore, an additional configuration (such as a configuration for imparting magnetic anisotropy to the detection target member) for detecting the strain direction is unnecessary, and cost and man-hours can be saved.

In the second embodiment, the following modifications can be added.
In the second embodiment, the effect of the present invention can be obtained if there are at least 2 stages × 4 rows of teeth, but three or more teeth stages may be formed. When three or more teeth stages are provided, the teeth stages may be provided at equal intervals in the axial direction. Further, five or more teeth rows may be formed.

  FIG. 7 schematically shows the configuration of teeth and magnetic paths when three or more teeth stages are provided in such a modification. In FIG. 7, a square represents a tooth, and a bidirectional arrow represents a magnetic path.

  Also in the second embodiment, a portion of each magnetic path formed in the magnetostrictive portion 22 forms 45 degrees with respect to the axial direction, but this angle can be arbitrarily changed as long as it is in an oblique direction. In other words, the portion formed in the magnetostrictive portion 22 of the magnetic path only needs to extend in a direction that is neither parallel nor perpendicular to the axis A. However, the magnetic paths adjacent to each other need to be formed so as to form equal angles opposite to each other in the axial direction.

  In the first and second embodiments and the modifications thereof, the use of the strain detection apparatus 10 is arbitrary, but it can be applied to various sensors that detect a change in magnetic permeability due to an external force, for example.

  10 strain detection device, 20 shaft member (detection target member), 22 magnetostriction part (detection target member), 30 core, M1 magnetic path (first magnetic path), M2 magnetic path (second magnetic path), A axis, T1 Teeth stage (first teeth stage), T2 teeth stage (second teeth stage), Ta teeth row (second teeth row), Tb teeth row (first teeth row), Tc teeth row (third teeth row), Td Teeth row, T11-16, T21-26, T5a-T5d, T6a-T6d Teeth.

Claims (7)

A core structure that includes an annular core including a magnetic body and a detection coil, and is used to detect a change in magnetic permeability of a detection target member,
Axial direction, radial direction and circumferential direction can be defined for the core,
The core includes at least four teeth protruding in a radial direction,
A plurality of magnetic paths through the detection target member and the two teeth are formed,
The plurality of magnetic paths are formed so as to cover the entire circumferential range in the detection target member.
Core structure. The plurality of teeth constitutes a plurality of teeth stages provided at different positions in the axial direction,
In each tooth stage, each tooth is provided at equal intervals in the circumferential direction.
The core structure according to claim 1. The first teeth stage and the second teeth stage are arranged so that the circumferential positions of the teeth are staggered,
For each tooth of the first teeth stage, a first magnetic path is formed between the teeth and the teeth of the second teeth stage adjacent to one side in the circumferential direction of the teeth, and the teeth and A second magnetic path is formed between the teeth of the second teeth step adjacent to the opposite side of the teeth in the circumferential direction,
The portions of the first magnetic path and the second magnetic path that pass through the teeth of the first tooth stage have the same orientation.
The core structure according to claim 2.   Each tooth is arrange | positioned so that the part formed in the said detection target member among each said magnetic paths may make an angle of 45 degree | times with respect to an axial direction. The core structure described. The core structure further includes an exciting coil,
The plurality of teeth constitute a plurality of teeth rows provided at different positions in the circumferential direction,
The detection coil is wound around each tooth of the first tooth row,
The detection coil is not wound on each tooth of each tooth row adjacent to both sides in the circumferential direction of the first tooth row, and the excitation coil is wound.
The core structure as described in any one of Claims 1-4.   The core structure according to any one of claims 2 to 5, further comprising three or more teeth stages, wherein the teeth stages are provided at equal intervals in the axial direction.   A strain detection apparatus comprising: the core structure according to any one of claims 1 to 6; and the detection target member including a cylindrical or cylindrical magnetostrictive member.

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