WO2024135549A1

WO2024135549A1 - Flexible sensor and measuring device

Info

Publication number: WO2024135549A1
Application number: PCT/JP2023/044982
Authority: WO
Inventors: 淳士野村; 利夫瓶子; 和延林
Original assignee: 日置電機株式会社
Priority date: 2022-12-23
Filing date: 2023-12-15
Publication date: 2024-06-27

Abstract

The present invention further increases measurement precision.　This flexible sensor (10), which detects a physical quantity of an object to be measured while surrounding the object to be measured, comprises: an elastic detector (1) that detects a physical quantity of an object to be measured; a first holding part (2) that holds one end of the detector; and a second holding part (3) that holds the other end of the detector, wherein, during detection of the physical quantity, a portion (13) where the detector is not held by the first holding part and the second holding part has a length where the portion (13) where the detector is not held conforms to a true circle (C), and portions (11, 12) where the detector is held by the first holding part and the second holding part are arranged in a state extending from a pair of contacts (s1, s2) on a pair of tangential lines in contact with the true circle in a linear direction along the pair of tangential lines, the portions intersecting each other.

Description

Flexible sensor and measuring device

The present invention relates to a flexible sensor and a measuring device that detects a physical quantity of a measurement object.

2. Description of the Related Art A current sensor that detects a value of a current flowing through a measurement object has been disclosed (see, for example, Japanese Patent Application Laid-Open No. 2003-233634).
The current sensor includes a coil body in which a conductive wire is wound in a spiral shape around a hollow flexible member having insulating properties, and a holding part that holds the coil body. When using the current sensor to detect the value of a current flowing through an object to be measured, the coil body is bent into a ring shape to surround the object to be measured, and the coil body is held by the holding part. In this way, the coil body forms a Rogowski coil, and the value of a current flowing through the object to be measured can be detected.

JP 2019-196962 A

In current sensors, the measurement accuracy varies depending on how the coil body surrounds the measurement target, so there is a demand for current sensors with a structure that can improve measurement accuracy.

The present invention was made in consideration of the above problems, and provides a flexible sensor and measuring device that can further improve measurement accuracy.

In order to solve the above problem, there is provided a flexible sensor that detects a physical quantity of a measurement object while surrounding the measurement object,
A detection body having elasticity and detecting a physical quantity of the measurement target;
A first holding portion that holds one end of the detection body;
A second holding portion that holds the other end of the detection body,
The portion of the detection body that is not held by the first holding portion and the second holding portion has a length that follows a perfect circle, and the portion of the detection body that is held by the first holding portion and the second holding portion is arranged in a state in which it extends in a straight line direction along the pair of tangents from a pair of contact points on a pair of tangents that are tangent to the perfect circle and intersects with each other.

Furthermore, it is preferable that the portion of the detection body held by the first holding portion and the second holding portion is arranged along a straight line extending from the tangent points of the regular n-gon circumscribing the perfect circle to the vertices of the regular n-gon between the tangent points.

Furthermore, it is preferable that the portions of the detection body held by the first holding portion and the second holding portion each have a length from the tangent point of a regular n-gon circumscribing the perfect circle to the vertex of the regular n-gon between the tangent points.

Furthermore, the portions of the detection body held by the first holding portion and the second holding portion are arranged along a straight line from a tangency between adjacent perfect circles of a regular n-gon circumscribing the perfect circle to a vertex of the regular n-gon between the tangency points, and the portions of the detection body held by the first holding portion and the second holding portion each have a length from a tangency between adjacent perfect circles of the regular n-gon to a vertex of the regular n-gon between the tangency points, and the length of the detection body is, when the radius of the perfect circle is r,

It is preferable that:

Furthermore, it is preferable that the portions of the detection body held by the first holding portion and the second holding portion each have a length extending from a pair of contact points on a pair of tangents that are tangent to the perfect circle to a point where the pair of tangents extend in a straight line along the pair of tangents and intersect with each other.

Furthermore, the portions of the detection body held by the first holding portion and the second holding portion are lengths from a pair of tangents on a pair of tangents that are tangent to a perfect circle surrounding the measurement target to a point at which the tangents extend in a linear direction along the pair of tangents and intersect with each other, and the length of the detection body is expressed as follows, when the angle between a pair of line segments from the center of the perfect circle to the pair of tangents is θ (θ < π/2) and the radius of the perfect circle is r:

It is preferable that:

Furthermore, it is preferable that at least one of the first holding portion and the second holding portion has an opening at one end and a storage portion into which one end or the other end of the detection body can be freely inserted.

It is also preferable that the storage section is formed to extend along a single linear direction.

Furthermore, it is preferable that at least one of the first holding portion and the second holding portion has a hole that communicates with the storage portion from the surface.

Furthermore, it is preferable that the hole is formed at a position facing the end of the detection body contained in the container.

Furthermore, it is preferable that the end of one end of the detection body and the end of the other end of the detection body are arranged so as to overlap one another.

One aspect of the present invention is a measuring device comprising the flexible sensor described above and a measuring unit that measures a physical quantity of the measurement target based on a detection signal detected by the flexible sensor.

According to this aspect of the present invention, measurement accuracy can be further improved.

FIG. 1 is a diagram showing a configuration of a measuring device equipped with a flexible sensor. FIG. 2 is a plan view of the flexible sensor when not in measurement. FIG. 2 is a plan view of the flexible sensor during measurement. FIG. 4 is an enlarged perspective view of both ends of the detection body during measurement. FIG. 2 is a perspective view showing the internal structure of the flexible sensor during measurement. FIG. 4 is a perspective view of a second holding portion. 13 is a perspective view showing a state in which a tip portion of a detection body is inserted into a second holding portion. FIG. FIG. 4 is a diagram for explaining the arrangement of each part of the detection body during measurement. 5A to 5C are diagrams illustrating a method for calculating the length of a detection object according to the first embodiment. 13A to 13C are diagrams illustrating a method for calculating the length of a detection object according to a second embodiment.

A first preferred embodiment of the present invention will be described with reference to the drawings. Note that the embodiment described below is merely an example, and various forms are possible within the scope of the present invention.

<Measurement Equipment>
First, the measurement device will be described.
As shown in FIG. 1, the measuring device 100 includes a flexible sensor 10 that detects a physical quantity of the object to be measured, an integration circuit 30 that integrates the detection signal output from the flexible sensor 10, and a measuring unit 40 that measures the physical quantity of the object to be measured based on the signal output from the integration circuit 30.
Measurement objects include power lines through which AC current flows, terminals of electronic components mounted on a circuit board, etc. Physical quantities of the measurement object include the value of the AC current flowing through the measurement object, the value of the AC power, the value of the AC magnetic field generated around the measurement object, etc.

(flexible sensor)
1 to 5, the flexible sensor 10 detects an alternating current flowing through a measurement object while surrounding the measurement object. The flexible sensor 10 is formed to be elastically deformable and includes a detection body 1 that detects an alternating current flowing through the measurement object, a first holding part 2 that holds one end (base end) 11 of the detection body 1, and a second holding part 3 that holds the other end (tip end) 12 of the detection body 1.

The detection body 1 is flexible and can bend when surrounding the measurement target. The detection body 1 is elastic and returns to its original shape or nearly its original shape when an external force is removed. The base end 11 of the detection body 1 is the portion that is inserted into and held by the first holding part 2, and is formed in a straight line.
The tip portion 12 of the detection body 1 is the portion that is inserted into and held by the second holding portion 3, and is formed in a straight line.
The intermediate portion 13 between the base end portion 11 and the tip end portion 12 of the detection body 1 is formed in a shape having a predetermined curvature so as to easily surround the measurement object. For example, when detecting the physical quantity of the measurement object, the intermediate portion 13 is disposed so as to follow a perfect circle C shown in FIG. 8 when surrounding the measurement object.
Therefore, both ends of the detection body 1 in the longitudinal direction (axial direction) are formed straight, and the remaining portion is curved to have a predetermined curvature. In other words, the detection body 1 has an inflection point at the boundary between the straight portion and the curved portion.
The base end 11 and the tip end 12 of the detection body 1 do not necessarily have to be formed straight, but may be formed curved. The middle portion 13 of the detection body 1 does not necessarily have to be curved, but may be formed straight like the both end portions.

As shown in FIG. 8 , the base end 11 and the tip end 12 of the detection body 1 are arranged in a straight line extending from the tangent points t1, t2 of a regular n-gon P circumscribing a perfect circle C formed by the middle portion 13 to the vertex v of the regular n-gon P between the tangent points t1, t2, with the detection body 1 surrounding the target, for example, when detecting a physical quantity of the target.
The length of the base end 11 and the tip end 12 of the detection body 1 (the length over which the detection body 1 is held by the first holding part 2 and the length over which the detection body 1 is held by the second holding part 3) is the length from the tangent points t1, t2 of the regular n-gon P with the adjacent perfect circles C to the vertex v of the regular n-gon P between the tangent points t1, t2.

The detection body 1 has a Rogowski coil formed along the longitudinal direction (extension direction), that is, the detection body 1 is a flexible current sensor of the Rogowski coil type.
A Rogowski coil is a flexible member having insulating hollowness and a conductive wire wound in a spiral shape. The flexible member is made of, for example, FEP resin, PEEK resin, etc. FEP resin has a flexural modulus of about 0.55 to 0.67 GPa, and PEEK resin has a flexural modulus of about 3.7 GPa, making them preferable flexible members for use in Rogowski coils.
The wound conductive wire extends from the base end 11 to the tip end 12 of the detection body 1 , and is wound so as to be folded back at the tip end 12 and return to the base end 11 .
In the Rogowski coil, in a state where the base end 11 is held by the first holding part 2 and the tip end 12 is held by the second holding part 3 (the state shown in Figs. 3 to 5), both ends are close to each other overlapping and facing each other to form a ring. That is, the detection body 1 is held by the first holding part 2 and the second holding part 3 such that the end face of the base end 11 and the end face of the tip end 12 face each other with a small gap in the overlapping direction while surrounding the measurement object, for example, in the case of detecting a physical quantity of the measurement object.
This allows the gap between the base end 11 and tip end 12 of the detection body 1 that forms the Rogowski coil to be reduced, thereby reducing the effects of noise caused by magnetic flux generated from other conductors close to the detection body 1.

The entire detection body 1 is covered with a resin material such as fluororesin. This prevents the detection body 1 from getting caught on the measurement object or other adjacent parts when surrounding the measurement object, which can cause damage to the detection body 1.

As shown in FIGS. 3 to 5, the first holding portion 2 is a portion that is operated by an operator when the detection body 1 surrounds the measurement target.
The first holding portion 2 holds the base end portion 11 of the detection body 1. The first holding portion 2 is formed in a box shape and is elongated in one direction. In the first holding portion 2, a pair of

side walls

21, 22 opposed to each other along the longitudinal direction are formed with

openings

21a, 22a, respectively.
A cable 50 that connects the matching circuit 20 and the integrating circuit 30 housed in the first holding portion 2 is inserted into the opening 21a.
The base end 11 of the detection body 1 held by the first holding part 2 is inserted into the opening 22a. Here, the base end 11 of the detection body 1 inserted into the first holding part 2 from the opening 22a is a portion that is formed in a straight line at one end of the detection body 1, as described above.
The first holding part 2 has a second holding part 3 provided on its surface. With the detection body 1 surrounding the measurement target, the tip 12 of the detection body 1 is inserted into and held in the second holding part 3, thereby making it possible to detect the physical quantity of the measurement target.
The longitudinal direction of the first holding portion 2 intersects with the longitudinal direction of the second holding portion 3. Specifically, as shown in Fig. 8, the longitudinal direction of the first holding portion 2 is arranged along a straight line extending from a tangent point t1 to a vertex v of the regular n-gon P between tangent points t1 and t2 of the regular n-gon P circumscribing the perfect circle C formed by the middle portion 13 of the detection body 1 and adjacent perfect circles C.
The matching circuit 20 is a circuit for matching the impedance of the detection body 1 side with the impedance of the measurement unit 40 side. The base end portion 11 of the detection body 1 and the matching circuit 20 are electrically connected by a cable 51 (see FIG. 1 ).

As shown in FIGS. 3 to 7, the second holding portion 3 is a portion that is operated by an operator when the detection body 1 surrounds the measurement target.
The second holding portion 3 holds the tip portion 12 of the detection body 1. The second holding portion 3 is formed in a cylindrical shape having a hollow portion, and is formed to be long in one direction. The second holding portion 3 has an opening 3a formed at one end along the longitudinal direction, and a storage portion 31 extending along the axial direction (one straight line direction) from one end to the other end.
The tip 12 of the detection body 1 held by the second holding part 3 is inserted into the accommodation part 31. Here, the tip 12 of the detection body 1 inserted from the accommodation part 31 into the second holding part 3 is the part formed in a straight line at the other end of the detection body 1, as described above.
The accommodation portion 31 is formed to a size that allows the tip portion 12 of the detection body 1 to be freely inserted therein. In other words, when the tip portion 12 of the detection body 1 is inserted into the accommodation portion 31, it is preferable that the boundary between the tip portion 12 and the middle portion 13 is located at the opening 3a of the second holding portion 3.
At the end of the accommodation portion 31 opposite the opening 3a, a hole 32 is formed which communicates from the accommodation portion 31 to the surface of the second holding portion 3. That is, the hole 32 is formed at a position facing the tip portion 12 of the detection body 1 accommodated in the accommodation portion 31, and the tip portion 12 of the detection body 1 inserted in the accommodation portion 31 can be visually confirmed through the hole 32. The hole may be slit-shaped.
The second holding portion 3 is fixed to the first holding portion 2 such that its longitudinal direction intersects with the longitudinal direction of the first holding portion 2. Specifically, as shown in Fig. 8, the second holding portion 3 is disposed in a state in which its longitudinal direction is aligned with a straight line extending from the tangent point t2 to the vertex v of the regular n-gon P between the tangent points t1 and t2 of the regular n-gon P circumscribing the perfect circle C formed by the middle portion 13 of the detection body 1 and adjacent perfect circles C.
The second holding portion 3 may be formed integrally with the first holding portion 2, or may be fixed to the first holding portion 2 by adhesion or the like.

(Integration circuit)
1, the integrating circuit 30 converts a detection signal indicating a voltage induced in the conductive wire of the detection body 1 by a current flowing through the object to be measured into a signal proportional to the amplitude of the current flowing through the object to be measured. The integrating circuit 30 outputs the converted signal to the measuring unit 40 as a detection signal.

(Measuring unit)
As shown in Fig. 1, the measurement unit 40 measures a physical quantity related to the measurement object based on a detection signal from the integration circuit 30. For example, when the measurement unit 40 receives a detection signal from the integration circuit 30, it measures an AC current flowing through the measurement object based on the detection signal. The measurement unit 40 may measure other physical quantities such as AC power or magnetic field strength based on the received detection signal. The measurement unit 40 displays a waveform of the measured physical quantity on a screen. The measurement unit 40 is configured by, for example, an oscilloscope, a power meter, or an ammeter.

<Usage of flexible sensors>
Next, a usage form of the flexible sensor 10 will be described.
2, the flexible sensor 10 is in an open state when the tip 12 of the detection body 1 is not overlapped with the base end 11, i.e., when the tip 12 of the detection body 1 is not held by the second holding portion 3. From this state, the operator surrounds the measurement target with the detection body 1 and inserts the tip 12 of the detection body 1 into the second holding portion 3 to hold the tip 12 with the second holding portion 3, resulting in the state shown in FIG.
As shown in Figures 3 to 5, when the tip portion 12 of the detection body 1 is held by the second holding portion 3, the tip of the tip portion 12 of the detection body 1 is arranged so as to overlap the tip of the base portion 11, and the middle portion 13 is arranged so as to follow the perfect circle C, as shown in Figures 3 and 8. Furthermore, the tip portion 12 and the base portion 11 of the detection body 1 are arranged so that the angle θ formed by the straight lines extending in the respective extension directions is the same as the interior angle of a regular n-gon P circumscribing the perfect circle C. Note that n in the regular n-gon P varies depending on the lengths of the first holding portion 2 and the second holding portion 3.
In other words, when the tip 12 of the detection body 1 is held by the second holding portion 3, the majority of the detection body 1 is along the perfect circle C, and the base end 11 and tip end 12 located at both ends are arranged in a straight line extending from the tangent points t1, t2 of the regular n-gon circumscribing the perfect circle C to the adjacent perfect circles C toward the vertex v of the regular n-gon P between the tangent points t1, t2.
When the tip 12 of the detection body 1 is removed from the second holding part 3, the detection body 1, which has elasticity, returns to its original shape as shown in FIG.

<Mechanism for improving measurement accuracy>
Next, a mechanism for improving the measurement accuracy using the flexible sensor 10 having the above configuration will be described.
The detection body 1 of the flexible sensor 10 is a Rogowski coil, in which a conductive wire is wound in a spiral shape around a hollow flexible member having insulating properties. Therefore, in order to improve detection accuracy, it is preferable to make the intervals between the conductive wires as uniform as possible, and it is preferable to arrange the detection body 1 in a perfect circle C that does not have an inflection point while surrounding the measurement target. In addition, in order to improve detection accuracy, it is preferable to reduce the gap between the ends of the detection body 1 as much as possible.
On the other hand, taking into consideration the workability when measuring physical quantities, it is preferable to form both ends of the detection body 1 in a straight line. Therefore, it is necessary to make the detection body 1 as a whole as close to a perfect circle C as possible, while keeping the straight portions at both ends of the detection body 1 within a range that does not interfere with the work.

In consideration of the above, it is preferable that the middle portion 13 of the detection body 1, when surrounding the measurement target, has a length that follows a perfect circle C as shown in FIG. 8, and that the linear base end portion 11 and tip end portion 12 held by the first holding portion 2 and the second holding portion 3 have a shape that follows a linear direction from the tangent points t1, t2 of the regular n-gon P (a regular polygon, n≧4 is preferable) circumscribing the perfect circle C formed by the middle portion 13 to the vertex v of the regular n-gon P between the tangent points t1, t2. It is also preferable that the lengths of the base end portion 11 and tip end portion 12 of the detection body 1 are each the length from the tangent points t1, t2 of the regular n-gon P with the adjacent perfect circles C to the vertex v of the regular n-gon P between the tangent points t1, t2.

The length of the detection body 1 can be calculated by the following formula.
As shown in FIG. 9 , if the radius of a perfect circle C is r, the line connecting the center O of the perfect circle C and a vertex v of a regular n-gon P is q, and the angle between the radius r and the line q is θa, then θa can be expressed by the following Equation 1.
(Equation 1)

Here, the length of the base end 11 of the detection body 1 (the length of the straight line connecting the tangency t1 and the vertex v) corresponds to half the length ln of one side of the regular n-gon P, and is therefore expressed by the following equation 2.
(Equation 2)

The length of tip 12 of detection body 1 (the length of the straight line connecting t2 and vertex v) corresponds to half the length ln of one side of regular n-gon P, and is therefore expressed by the above formula 2. In other words, the sum of the length of base end 11 and the length of tip 12 of detection body 1 corresponds to the length ln of one side of regular n-gon P.
Furthermore, the length lc of the middle portion 13 of the detection body 1 is obtained by subtracting the length of the arc connecting the tangent points t1 and t2 from the circumferential length 2πr of the perfect circle C, and is therefore expressed by the following equation 3.
(Equation 3)

Therefore, the length l of the detection body 1 is the sum of the length ln, which is the sum of the length of the base end 11 and the length of the tip end 12, and the length lc of the middle portion 13, and can be expressed by the following equation 4.
(Equation 4)

As n (the number of corners) of a regular n-gon circumscribing the perfect circle C becomes smaller, the lengths of the base end 11 and the tip end 12 of the detection body 1 become larger, and the detection accuracy of the detection body 1 decreases.
As n (the number of corners) of a regular n-gon circumscribing a perfect circle C increases, the lengths of the base end 11 and the tip end 12 of the detection body 1 decrease, so that the detection body 1 can be brought closer to the perfect circle C. However, the lengths of the first holding part 2 and the second holding part 3 also decrease, so that the workability during measurement decreases. In addition, the friction between the base end 11 and the first holding part 2 and the friction between the tip end 12 and the second holding part 3 also decrease, so that it becomes difficult to fix the detection body 1 to each holding

part

2, 3 by frictional force alone. In addition, the angle between the base end 11 and the tip end 12 increases, so that the detection bodies 1 may overlap and interfere with each other.
Furthermore, if the length of the base end 11 and the tip end 12 is too short or too long, the gap between both ends of the detection body 1 will become large, and the measurement accuracy will decrease.
In consideration of the above, it is preferable that the angle θ between the straight lines extending in the direction in which the tip end 12 and the base end 11 of the detection body 1 extend is approximately 120° to 150°, and therefore the regular n-gon circumscribing the perfect circle C is preferably a regular hexagon, regular octagon, or regular decagon, and in particular, a regular octagon.

As described above, according to the flexible sensor 10 and the measuring device 100, when the tip 12 of the elastic detection body 1 is inserted into the second holding part 3 and the tip 12 is held by the second holding part 3 to surround the measurement target, the middle part 13 of the detection body 1 has a length along the perfect circle C, and the base end part 11 and the tip part 12 are arranged in a state along a straight line from the tangent points t1, t2 of the regular n-gon P circumscribing the perfect circle C to the vertex v of the regular n-gon P between the tangent points t1, t2. This can also be said to mean that the detection body 1 is arranged in a state in which it extends in a straight line from a pair of tangent points t1, t2 on the tangent line of the perfect circle C and intersects with each other. By arranging in this way, the shape of the part of the detection body 1 that is not held can be made closer to the perfect circle C, so that the measurement accuracy of the physical quantity of the measurement target can be further improved.
Furthermore, by making the lengths of the base end 11 and tip end 12 of the detection body 1 equal to the lengths from the tangent points t1, t2 of the regular n-gon P with the adjacent perfect circles C to the vertex v of the regular n-gon P between the tangent points t1, t2, the tip of the base end 11 and the tip of the tip end 12 can be brought closest to each other. This makes it possible to minimize the gaps at both ends of the detection body 1 and eliminate any part of the detection body 1 that deviates from the perfect circle C and the regular n-gon P, thereby further improving the measurement accuracy of the physical quantity of the object to be measured.

In addition, since the second holding part 3 has a storage part 31 into which the tip part 12 of the detection body 1 is inserted, when the detection body 1 attempts to return to its original shape due to its elastic force, the elastic force brings the tip part 12 into contact with the inner wall of the storage part 31, thereby fixing the tip part 12 within the storage part 31. This makes it possible to attach the tip part 12 of the detection body 1 to the second holding part 3 with a simple mechanism of inserting the tip part 12 into the storage part 31.
Furthermore, since the receiving portion 31 is formed so as to extend along its axial direction (a single linear direction), the tip portion 12 of the detection body 1 can be easily inserted into the receiving portion 31 .
Furthermore, since the second holding portion 3 is formed with a hole 32 that communicates from the storage portion 31 to the surface, it is possible to easily check whether or not the tip portion 12 of the detection body 1 is inserted into the storage portion 31. In particular, by forming the hole 32 at a position facing the tip portion 12 of the detection body 1 stored in the storage portion 31, it is possible to check whether or not the tip portion 12 is securely inserted all the way into the storage portion 31, and variation in the insertion depth of the detection body 1 into the storage portion 31 by the operator can be reduced.
Furthermore, since the tip 12 of the detection body 1 is formed in a straight line, the tip 12 can be inserted into the second holding part 3 more easily than if it were formed in a curved line.
In addition, because the base end 11 of the detection body 1 is formed in a straight line, when the first holding part 2 is pushed toward the measurement target by the operator's finger, the force can be easily transmitted to the detection body 1. Furthermore, because the base end 11 of the detection body 1 is formed in a straight line, the structure of the first holding part 2 can be simplified.
In addition, since both ends 12, 11 of the detection body 1 are formed in a straight line, the shape formed by the detection body 1 after the tip 12 of the detection body 1 is inserted into the second holding portion 3 is symmetrical. Therefore, even if the position of the measurement object is shifted in the symmetrical direction, this is canceled out by the symmetry, and the effect on the measured current value is reduced, so the current value can be measured with high precision.
Furthermore, since the length required for the detection body 1 can be calculated using the above formula 4, the flexible sensor 10 can be designed easily.

Next, a second preferred embodiment of the present invention will be described with reference to the drawings. Note that the embodiment described below is merely an example, and various forms are possible within the scope of the present invention.

<Usage of flexible sensors>
A usage form of the flexible sensor 10 in the second embodiment will be described. Note that the same configuration as the flexible sensor in the first embodiment will not be described in detail to avoid duplication.
As shown in Figures 3 to 5, when the tip portion 12 of the detection body 1 is held by the second holding portion 3, the tip of the tip portion 12 of the detection body 1 is arranged to overlap the tip of the base end portion 11 of the detection body 1, and the middle portion 13 has a length along the perfect circle C, as shown in Figures 3 and 10. The tip portion 12 and the base end portion 11 of the detection body 1 are arranged such that the angle φ = π - θ formed by straight lines along the extension direction of each other is the same as the interior angle formed by straight lines extending from a pair of contact points on a pair of tangent lines tangent to the perfect circle C and extending along the pair of tangent lines. The angle φ varies depending on the lengths of the first holding portion 2 and the second holding portion 3.
In other words, when the tip 12 of the detection body 1 is held by the second holding portion 3, the majority of the detection body 1 is along the perfect circle C, and the base end 11 and tip end 12 located at both ends are arranged so that they extend in a straight line along a pair of tangents to the perfect circle C from the points of contact s1, s2 with the perfect circle C and the tangents toward the vertex w.
When the tip 12 of the detection body 1 is removed from the second holding part 3, the detection body 1, which has elasticity, returns to its original shape as shown in FIG.

<Mechanism for improving measurement accuracy>
Next, a mechanism for improving the measurement accuracy using the flexible sensor 10 according to the second embodiment will be described.
The detection body 1 of the flexible sensor 10 is a Rogowski coil, in which a conductive wire is wound in a spiral shape around a hollow flexible member having insulating properties. Therefore, in order to improve detection accuracy, it is preferable to make the intervals between the conductive wires as uniform as possible, and it is preferable to arrange the detection body 1 in a perfect circle C that does not have an inflection point while surrounding the measurement target. In addition, in order to improve detection accuracy, it is preferable to reduce the gap between the ends of the detection body 1 as much as possible.
On the other hand, taking into consideration the workability when measuring physical quantities, it is preferable to form both ends of the detection body 1 in a straight line. Therefore, it is necessary to make the detection body 1 as a whole as close to a perfect circle C as possible, while keeping the straight portions at both ends of the detection body 1 within a range that does not interfere with the work.

Taking the above into consideration, it is preferable that the middle portion 13 of the detection body 1, when surrounding the measurement target, has a length that follows a perfect circle C as shown in FIG. 10, and that the linear base end portion 11 and tip end portion 12 held by the first holding portion 2 and the second holding portion 3 have a shape that extends in a straight line along a pair of tangents from a pair of contact points s1, s2 on a pair of tangents tangent to the perfect circle C and intersects with the pair of tangents. It is also preferable that the length of the base end portion 11 and tip end portion 12 of the detection body 1 is the length from a pair of contact points s1, s2 on a pair of tangents tangent to the perfect circle C to a point w where the pair of tangents extend in a straight line along the pair of tangents and intersect.

The length of the detection body 1 can be calculated by the following formula.
As shown in FIG. 10 , if the radius of the perfect circle C is r and the interior angle between the line segment extending from the center O of the perfect circle C to the tangent point s1 and the line segment extending from the center O of the perfect circle C to the tangent point s2 is θ (θ < π/2), the sum of the length of the base end 11 and the length of the tip end 12 of the detection body 1, that is, length 2x (the sum of the length of the straight line connecting the tangent point s1 and point w and the length of the straight line connecting the tangent point s2 and point w), is expressed by the following equation 6.
(Equation 6)

Furthermore, the length l of the middle portion 13 of the detection body 1 is obtained by subtracting the length of the arc connecting the tangent points s1 and s2 from the circumferential length 2πr of the perfect circle C, and is therefore expressed by the following equation 7.
(Equation 7)

Therefore, the length L of the detection body 1 is the sum of the length 2x, which is the sum of the length of the base end 11 and the length of the tip end 12, and the length l of the middle portion 13, and can be expressed by the following equation 8.
(Equation 8)

The larger the interior angle θ between the line segment extending from the center O of the perfect circle C to the tangent point s1 and the line segment extending from the center O of the perfect circle C to the tangent point s2, the longer the base end 11 and the tip end 12 of the detection body 1 become, and the detection accuracy of the detection body 1 decreases.
As the interior angle θ between the line segment extending from the center O of the perfect circle C to the tangent point s1 and the line segment extending from the center O of the perfect circle C to the tangent point s2 becomes smaller, the length of the base end 11 and the tip end 12 of the detection body 1 becomes smaller, so that the detection body 1 can be brought closer to the perfect circle C, but the length of the first holding part 2 and the second holding part 3 also becomes smaller, so that the workability during measurement decreases. In addition, the friction between the base end 11 and the first holding part 2 and the friction between the tip end 12 and the second holding part 3 also becomes smaller, so that it becomes difficult to fix the detection body 1 to each holding

part

2, 3 by friction force alone. In addition, since the angle formed by the base end 11 and the tip end 12 becomes larger, there is a risk that the detection bodies 1 will overlap and interfere with each other.
Furthermore, if the length of the base end 11 and the tip end 12 is too short or too long, the gap between both ends of the detection body 1 will become large, and the measurement accuracy will decrease.

As described above, according to the flexible sensor 10 and the measuring device 100, the tip 12 of the elastic detection body 1 is inserted into the second holding part 3, and the tip 12 is held by the second holding part 3, and the middle part 13 of the detection body 1 has a length along the perfect circle C, and the base end 11 and the tip 12 located at both ends are arranged in a state in which they extend linearly from a pair of tangents tangent to the perfect circle C and contact points s1, s2 with the perfect circle C along the tangents toward the apex w. In other words, the elastic detection body is arranged in a state in which they extend linearly from a pair of contact points s1, s2 on a pair of tangents to the perfect circle C and intersect with each other. This arrangement allows the shape of the unheld part of the detection body 1 to be closer to the perfect circle C, thereby further improving the measurement accuracy of the physical quantity of the measurement target.
Furthermore, by making the lengths of the base end 11 and the tip end 12 of the detection body 1 equal to the pair of tangents to the perfect circle C and the vertex w extending in a linear direction along the tangents from the contact points s1, s2 with the perfect circle C, the tip of the base end 11 and the tip of the tip end 12 can be brought closest to each other. This makes it possible to minimize the gaps at both ends of the detection body 1, and eliminates any part of the detection body 1 that deviates from the perfect circle C and the regular n-gon P, thereby further improving the measurement accuracy of the physical quantity of the object to be measured.

＜Other＞
Although the preferred embodiments of the present invention have been described above, the present invention is not limited to the above embodiments, and includes all aspects included in the concept and scope of the claims of the present invention. In addition, each configuration may be appropriately and selectively combined so as to achieve at least a part of the above-mentioned problems and effects. In addition, for example, the shape, material, arrangement, size, etc. of each component in the above embodiments may be appropriately changed depending on the specific usage mode of the present invention.
For example, a perfect circle in this specification may be a slightly distorted perfect circle (one whose diameter is increased or decreased by up to about 10% from a perfect circle).
Further, the straight line in this specification may be a slightly distorted straight line (a part of the straight line deviating from the true position of the straight line by up to about 10% of the length of the straight line).
In addition, the regular n-gon P circumscribing the perfect circle C formed by the middle part 13 of the detection body 1 is not limited to the regular octagon given as an example, and any regular polygon can be selected. However, as described above, when n is small, such as in a regular quadrangle, the base end 11 and the tip end 12 of the detection body 1 become long and the shape becomes farther from the perfect circle C, which is not preferable, and when n is large, such as in a regular icosagon, the base end 11 and the tip end 12 of the detection body 1 become short, and the holding

parts

2 and 3 become small, making it difficult for the operator to grasp them and reducing workability, which is not preferable. Therefore, it is necessary to select a regular n-gon P that is well-balanced and satisfies both requirements.
In addition, the base end 11 and the tip end 12 of the detection body 1 are overlapped in a direction perpendicular to the planar direction of the perfect circle C formed by the detection body 1, but they may also be overlapped so as to minimize gaps within the same plane.
Also, the base end 11 and the tip end 12 of the detection body 1 may be formed along the perfect circle C formed by the middle portion 13. In this case, the first holding portion 2 and the second holding portion 3 may be formed to match the curved base end 11 and tip end 12, or only the internal storage portions of the first holding portion 2 and the second holding portion 3 may be formed to match the base end 11 and tip end 12, respectively.
Further, the accommodation portion 31 is not limited to being provided in the second holding portion 3, but may be provided in the first holding portion 2. That is, it is sufficient that the accommodation portion 31 is provided in at least one of the first holding portion 2 and the second holding portion 3. The same applies to the hole 32 communicating with the accommodation portion 31.
Also, the second holding part 3 may be attached to the tip 12 of the detection body 1, and the second holding part 3 may be configured to be detachable from the first holding part 2. In this case, the first holding part 2 may be provided with a recess for accommodating the second holding part 3 and a locking part for locking the second holding part 3, and the physical quantity of the measurement target may be measured with the second holding part 3 locked to the first holding part 2.
Furthermore, the accommodating portion 31 does not necessarily have to be capable of receiving the tip 12 of the detection body 1, but a groove may be provided in the first holding portion 2 or the second holding portion 3 so that the tip 12 can be fitted into the groove.
Furthermore, the end of the base end 11 of the detection body 1 and the end of the tip end 12 of the detection body 1 may be arranged so as to be in contact on the same surface without being vertically overlapping.

REFERENCE SIGNS LIST 1 detection body 11 base end 12 tip end 13 middle portion 2 first holding portion 21 side wall portion 22 side wall portion 21a opening 22a opening 3 second holding portion 31 storage portion 32 hole 10 flexible sensor 20 matching circuit 30 integrating circuit 40 measuring portion 100 measuring device C perfect circle P regular n-gon t1, t2 tangent point v vertex

Claims

A flexible sensor that detects a physical quantity of a measurement target in a state in which the measurement target is surrounded,
A detection body having elasticity and detecting a physical quantity of the measurement target;
A first holding portion that holds one end of the detection body;
A second holding portion that holds the other end of the detection body,
A current sensor characterized in that the portion of the detection body that is not held by the first holding portion and the second holding portion has a length that follows a perfect circle, and the portion of the detection body that is held by the first holding portion and the second holding portion is arranged in a state in which it extends in a straight line direction along the pair of tangents from a pair of contact points on a pair of tangents that are tangent to the perfect circle and intersects with each other.
The flexible sensor described in claim 1, characterized in that the portion of the detection body held by the first holding portion and the second holding portion is arranged along a straight line from the tangent points of the regular n-gon circumscribing the perfect circle to the vertices of the regular n-gon between the tangent points.
The flexible sensor according to claim 1 or 2, characterized in that the portions of the detection body held by the first holding portion and the second holding portion are lengths from the tangent points of the regular n-gons circumscribing the perfect circle to the vertices of the regular n-gons between the tangent points.
the portions of the detection body held by the first holding portion and the second holding portion are arranged along a straight line direction from a tangency between adjacent perfect circles of a regular n-gon circumscribing the perfect circle to a vertex of the regular n-gon between the tangency points,
the portions of the detection body held by the first holding portion and the second holding portion each have a length from a tangent point between the adjacent perfect circles of the regular n-gon to a vertex of the regular n-gon between the tangent points,
The length of the detection body is, when the radius of the perfect circle is r,

2. The flexible sensor according to claim 1 .
The flexible sensor according to claim 1, characterized in that the portions of the detection body held by the first holding portion and the second holding portion are lengths extending from a pair of contact points on a pair of tangents that are tangent to the perfect circle to a point where the pair of tangents extend in a straight line along the pair of tangents and intersect with each other.
The portions of the detection body held by the first holding portion and the second holding portion each have a length from a pair of contact points on a pair of tangent lines that are tangent to a perfect circle surrounding the measurement target to a point where the pair of tangent lines extend in a linear direction along the pair of tangent lines and intersect with each other, and the length of the detection body is expressed as follows, when the interior angle of the pair of contact points from the center of the perfect circle is θ (θ < π/2) and the radius of the perfect circle is r:

6. The flexible sensor according to claim 1 or 5,
The flexible sensor according to any one of claims 1 to 6, characterized in that at least one of the first holding portion and the second holding portion has an opening at one end and a housing portion into which one end or the other end of the detection body can be freely inserted.
The flexible sensor according to any one of claims 1 to 7, characterized in that the housing portion is formed to extend along one linear direction.
The flexible sensor according to any one of claims 1 to 8, characterized in that at least one of the first holding portion and the second holding portion has a hole that communicates from the housing portion to the surface.
The flexible sensor according to claim 9, characterized in that the hole is formed at a position opposite the end of the detection body contained in the container.
The flexible sensor according to any one of claims 1 to 10, characterized in that the end of one end of the detection body and the end of the other end of the detection body are arranged so as to overlap one another.
A flexible sensor according to any one of claims 1 to 11;
a measurement unit that measures a physical quantity of the measurement object based on a detection signal detected by the flexible sensor;
A measuring device comprising: