Load cell

Abstract

To provide a load cell capable of detecting fatigue generated on a strain body in an early stage.SOLUTION: A load cell for detecting load applied in a tension direction comprises a strain body, a load detection strain gauge attached to the strain body, and a fatigue detection strain gauge attached to the strain body. The strain body includes: a first base part and a second base part arrayed in the tension direction; a connection part connecting the first base part to the second base part; and a stress increased section configured to connect the first base part to the second base part, and generate, according to load applied in the tension direction, tension stress greater than tension stress generated in the connection part according to the load. The connection part and the stress increased section are arrayed in a crossing direction crossing the tension direction. The fatigue detection strain gauge is attached to the stress increased section.SELECTED DRAWING: Figure 1

Description

[Technical field]

[0001] The present invention relates to a load cell. [Background technology]

[0002] Various structural members such as beams and columns suffer fatigue when repeatedly subjected to stress. Patent Document 1 discloses a fatigue detection strain gauge that can predict signs of fatigue failure occurring locally in a structural member in advance. [Prior art documents] [Patent documents]

[0003] [Patent Document 1] Patent No. 5802101 Specification Summary of the Invention [Problem to be solved by the invention]

[0004] A load cell having a function for detecting fatigue of a flexure body can be constructed by attaching a strain gauge having a fatigue detection function as described in Patent Document 1 to the flexure body. In such a load cell, by detecting fatigue of the flexure body by the strain gauge at an earlier stage, it is possible to secure a sufficient time before replacing the load cell, for example.

[0005] An object of the present invention is to provide a load cell that can detect the occurrence of fatigue in a strain element at an earlier stage. [Means for solving the problem]

[0006] According to a first aspect of the present invention, A load cell for detecting a load applied in a tensile direction, A strain body, A strain gauge for detecting a load attached to the strain body; a strain gauge for detecting fatigue attached to the strain body, The strain body is A first base portion and a second base portion aligned in the tensile direction; a connecting portion that connects the first base portion and the second base portion; a stress increasing portion that connects the first base portion and the second base portion and is configured to generate a tensile stress in response to a load applied in the tensile direction that is greater than a tensile stress generated in the connecting portion in response to the load, the connecting portion and the stress increasing portion are aligned in a cross direction crossing the tensile direction, A load cell is provided in which the fatigue detection strain gauge is affixed to the stress increase portion.

[0007] According to a second aspect of the present invention, A load cell for detecting a load applied in a tensile direction, A strain body, A strain gauge attached to the strain body, The strain body is A first base portion and a second base portion aligned in the tensile direction; a connecting portion that connects the first base portion and the second base portion; a stress increasing portion that connects the first base portion and the second base portion and is configured to generate a tensile stress in response to a load applied in the tensile direction that is greater than a tensile stress generated in the connecting portion in response to the load, the connecting portion and the stress increasing portion are aligned in a cross direction crossing the tensile direction, A load cell is provided having the strain gauge affixed to the stress increase portion. Effect of the Invention

[0008] According to the load cell of the present invention, the occurrence of fatigue in the strain element can be detected at an earlier stage. [Brief description of the drawings]

[0009] [Figure 1] FIG. 1 is a perspective view of a load cell according to an embodiment. [Diagram 2] FIG. 2 is a plan view of the load cell according to the embodiment. [Diagram 3] FIG. 3 is a plan view of the strain gauge. [Figure 4] FIG. 4 is a schematic diagram of a crane. [Diagram 5] 5(a), 5(b), 5(c), and 5(d) are plan views of modified strain bodies, respectively. [Figure 6] FIG. 6 is a perspective view of a strain generating body according to a modified example. [Figure 7] FIG. 7 is a perspective view of a load cell according to a modified example. DETAILED DESCRIPTION OF THE PREFERRED EMBODIMENTS

[0010] <Embodiment> A load cell LC according to an embodiment of the present invention will be described with reference to Figures 1 to 4. In this embodiment, the load cell LC will be described using as an example a case in which it is used inside a crane CR (Figure 4).

[0011] [Structure of LC load cell] As shown in FIG. 1, the load cell LC mainly comprises a strain element 100, a strain gauge 200, and mounting screws 310 and 320.

[0012] In the following description, the direction in which the flexure body 100 and the mounting screws 310, 320 are aligned is referred to as the tensile direction, the side where the mounting screw 310 is located relative to the flexure body 100 is referred to as the upper side, and the side where the mounting screw 320 is located relative to the flexure body 100 is referred to as the lower side. In addition, the direction in which the stress increase portion 20, the first connecting portion 31, and the second connecting portion 32 (all of which will be described later) of the flexure body 100 are aligned is referred to as the width direction (an example of a cross direction), the side where the first connecting portion 31 is located relative to the stress increase portion 20 is referred to as the left side, and the side where the second connecting portion 32 is located relative to the stress increase portion 20 is referred to as the right side. In addition, the direction perpendicular to the tensile direction and the width direction is referred to as the thickness direction.

[0013] [Strain element 100] The strain body 100 is a member that generates strain in response to a load applied from a measurement target when the load cell LC is in use. In this embodiment, the strain body 100 is a thick rectangular plate.

[0014] 1 and 2, five parts are defined in the flexure body 100 via a first through hole TH1 and a second through hole TH2 that penetrate the flexure body 100 in the thickness direction. The five parts are a first base portion 11, a second base portion 12, a stress increase portion 20, a first connecting portion 31, and a second connecting portion 32.

[0015] The first through hole TH1 is arch-shaped when viewed in the thickness direction. The first through hole TH1 is defined by a plane P1 extending in a plane including the tensile direction and the thickness direction, and a curved surface C1 extending in the thickness direction and protruding to the right in the width direction.

[0016] The second through hole TH2 is arch-shaped when viewed in the thickness direction. The second through hole TH2 is defined by a plane P2 extending in a plane including the tensile direction and the thickness direction, and a curved surface C2 extending in the thickness direction and protruding to the left in the width direction.

[0017] The first through hole TH1 and the second through hole TH2 have the same shape and size. One of the first through hole TH1 and the second through hole TH2 is provided at a position rotated 180° from the other of the first through hole TH1 and the second through hole TH2 about the central axis X that extends in the tensile direction through the center of the width direction and thickness direction of the strain body 100.

[0018] 2, the first base portion 11 is a portion above the upper ends of the first through hole TH1 and the second through hole TH2. The first base portion 11 is a rectangular flat plate whose long side direction is the width direction and whose short side direction is the tensile direction.

[0019] The second base portion 12 is a portion below the lower ends of the first through hole TH1 and the second through hole TH2. The second base portion 12 is a rectangular flat plate whose long side direction is the width direction and whose short side direction is the tensile direction.

[0020] The stress increase portion 20 is a portion surrounded by the first through hole TH1, the second through hole TH2, the first base portion 11, and the second base portion 12. The stress increase portion 20 is columnar and extends in the tensile direction. The width dimension of the stress increase portion 20 is large at both ends in the tensile direction, and gradually decreases from both ends toward the center in the tensile direction. That is, the stress increase portion 20 is configured such that the cross-sectional area of ​​a cross section perpendicular to the tensile direction is largest at both ends in the tensile direction, and gradually decreases toward the center in the tensile direction. This configuration increases the tensile stress generated in the stress increase portion 20 (described in detail later).

[0021] The first connecting portion 31 is a portion surrounded by the first through hole TH1, the first base portion 11, and the second base portion 12. The first connecting portion 31 is columnar and extends in the tensile direction. The cross-sectional area of ​​the cross section perpendicular to the tensile direction of the first connecting portion 31 is constant throughout the entire area in the tensile direction.

[0022] The second connecting portion 32 is a portion surrounded by the second through hole TH2, the first base portion 11, and the second base portion 12. The second connecting portion 32 is columnar and extends in the tensile direction. The cross-sectional area of ​​the cross section perpendicular to the tensile direction of the second connecting portion 32 is constant throughout the entire area in the tensile direction.

[0023] The first connecting portion 31 and the second connecting portion 32 have the same shape and dimensions. One of the first connecting portion 31 and the second connecting portion 32 is provided at a position rotated 180° around the central axis X of the strain body 100 from the other of the first connecting portion 31 and the second connecting portion 32.

[0024] Here, when a tensile load (a load that pulls the strain body 100 upward and downward in the tensile direction) is applied to the strain body 100, the tensile stress generated in the stress increasing portion 20 is increased and becomes larger than the tensile stress generated in the first connecting portion 31 and the second connecting portion 32. The reason for this is as follows.

[0025] When a tensile load of F [N] is applied to the strain body 100, the load is distributed and applied to the stress increasing section 20, the first connecting section 31, and the second connecting section 32 so that the tensile stresses generated at the ends in the tensile direction of each section are equal to each other.

[0026] For example, the cross-sectional area (area of ​​a cross section perpendicular to the tensile direction) at the end 20e (FIG. 2) of the stress increase portion 20 in the tensile direction is A 20 [mm 2 ], the cross-sectional area of ​​the end 31e of the first connecting portion 31 in the tensile direction (the area of ​​a cross section perpendicular to the tensile direction) is A 31 [mm 2 ], the cross-sectional area of ​​the end 32e of the second connecting portion 32 in the tensile direction (the area of ​​a cross section perpendicular to the tensile direction) is A 32 [mm 2 At this time, the tensile load F [N] is A 20 :A 31 :A 32 is applied to the stress increasing portion 20, the first connecting portion 31, and the second connecting portion 32 in a ratio of 0.1 to 1.0. Therefore, the tensile stress (=tensile load / cross-sectional area) generated at the end 20e of the stress increasing portion 20, the tensile stress generated at the end 31e of the first connecting portion 31, and the tensile stress generated at the end 32e of the second connecting portion 32 are equal to each other.

[0027] As described above, the first connecting portion 31 and the second connecting portion 32 have the same cross-sectional area over the entire area in the tensile direction. Therefore, the tensile stress (=tensile load / cross-sectional area) generated in the first connecting portion 31 and the second connecting portion 32 is constant over the entire area in the tensile direction.

[0028] On the other hand, the stress increasing portion 20 is configured such that the cross-sectional area of ​​the cross section perpendicular to the tensile direction is largest at both ends in the tensile direction and becomes smaller toward the central portion 20c in the tensile direction. Therefore, the tensile stress (=tensile load / cross-sectional area) generated in the stress increasing portion 20 becomes larger toward the central portion 20c in the tensile direction, and becomes larger than the tensile stress generated in the first connecting portion 31 and the second connecting portion 32. Moreover, the tensile stress generated in the stress increasing portion 20 is largest at the central portion 20c where the cross-sectional area is the smallest.

[0029] [Strain gauge 200] The strain gauge 200 detects (senses) the strain occurring in the stress increase portion 20 and also detects (senses) the occurrence of fatigue in the stress increase portion 20 .

[0030] 3, the strain gauge 200 has a substrate 210, connection terminals 221 and 222, and a pattern 230. The connection terminals 221 and 222 and the pattern 230 are formed on the substrate 210.

[0031] The substrate 210 is a film-like member that is attached to a detection object (the strain generating body 100 in this embodiment). The substrate 210 is made of an insulating resin material. In this embodiment, the substrate 210 is rectangular in plan view.

[0032] The connection terminals 221 and 222 are terminals to which wiring (not shown) that connects the pattern 230 and a calculation unit (not shown, which can be provided inside or outside the load cell LC) is fixed. The connection terminals 221 and 222 are formed of metal foil. In this embodiment, each of the connection terminals 221 and 222 is approximately rectangular in plan view.

[0033] The pattern 230 is configured such that the resistance value changes in response to the strain of the detection object. The pattern 230 is formed of metal foil. In this embodiment, the pattern 230 includes a strain detection pattern 231, a fatigue detection pattern 232, and a conductive pattern 233.

[0034] The strain detection pattern 231 has a shape in which a linear metal foil is folded back in a zigzag pattern, and has multiple strands 231s each extending linearly and folded back tabs 231t connecting two adjacent strands 231s in the width direction. Hereinafter, the direction in which the strands 231s extend is referred to as the detection direction of the strain gauge 200, and the direction in which the multiple strands 231s are lined up is referred to as the width direction of the strain gauge 200.

[0035] The shape of the inner part of the folded tab 231t where the strand 231s and the folded tab 231t are connected is a curved shape whose curvature changes continuously and gradually. As a result, in the strain detection pattern 231, breaks due to fatigue of the metal foil are less likely to occur than in the fatigue detection pattern 232.

[0036] The fatigue detection pattern 232 has a shape in which linear metal foil is folded back in a zigzag pattern, similar to the strain detection pattern 231. The fatigue detection pattern 232 has a plurality of strands 232s each extending in the detection direction and aligned in the width direction, and a folded tab 232t connecting two adjacent strands 232s in the width direction.

[0037] The conductive pattern 233 has a shape in which a linear metal foil is folded back in a zigzag pattern, similar to the strain detection pattern 231. The conductive pattern 233 has a plurality of strands 233s each extending in the detection direction and aligned in the width direction, and a folded tab 233t connecting two adjacent strands 233s in the width direction.

[0038] The shape of the inner part of the folded tab 233t where the strand 233s and the folded tab 233t are connected is a curved shape whose curvature changes gradually and continuously. As a result, in the conductive pattern 233, breaks due to fatigue of the metal foil are less likely to occur than in the fatigue detection pattern 232.

[0039] The strain detection pattern 231 is connected to the connection terminal 221 at one end, and is connected to the fatigue detection pattern 232 and the conductive pattern 233 at the other end. The fatigue detection pattern 232 is connected to the strain detection pattern 231 at one end, and is connected to the connection terminal 222 at the other end. The conductive pattern 233 is connected to the strain detection pattern 231 at one end, and is connected to the connection terminal 222 at the other end. That is, in the pattern 230, the fatigue detection pattern 232 and the conductive pattern 233 are connected in parallel, and the strain detection pattern 231, the fatigue detection pattern 232, and the conductive pattern 233 are connected in series. If the resistance value of the strain detection pattern 231 is R1, the resistance value of the fatigue detection pattern 232 is R2, and the resistance value of the conductive pattern 233 is R3, the resistance value R of the pattern 230 is R=R1+{R2×R3 / (R2+R3)}.

[0040] When a strain occurs in the detection direction in the detection object to which the strain gauge 200 is attached, strain also occurs in each of the strands 231 of the strain detection pattern 231 and each of the strands 232 of the fatigue detection pattern 232, causing a change in the overall length of the pattern 230 and in turn in the resistance value R of the pattern 230. Based on this change in the resistance value R, the magnitude of the strain occurring in the detection object (the magnitude of the load applied to the detection object) is detected. Note that each of the strands 233s of the conductive pattern 233 is short, so that the effect on the change in the overall length of the pattern 230 (i.e., the change in the resistance value R) is small.

[0041] When fatigue occurs in the detection object to which the strain gauge 200 is attached, fatigue also occurs in the fatigue detection pattern 232, causing breakage in the fatigue detection pattern 232. This breakage occurs mainly at the connection between the strand 232s and the folded tab 232t. As described above, the strain detection pattern 231 and the conductive pattern 233 are configured to be less susceptible to breakage due to fatigue of the metal foil compared to the fatigue detection pattern 232. Therefore, breakage of the pattern 230 due to fatigue of the detection object, and therefore of the pattern 230 (i.e., breakage due to fatigue of the metal foil) occurs in the fatigue detection pattern 232.

[0042] Here, if fatigue detection pattern 232 is broken, the resistance between strain detection pattern 231 and connection terminal 222 becomes resistance R3 of conductive pattern 233, which is a combined resistance in parallel of resistance R2 of fatigue detection pattern 232 and resistance R3 of conductive pattern 233. As a result, the resistance between strain detection pattern 231 and connection terminal 222 increases, and resistance R of pattern 230 also increases. Based on this increase in resistance R, fatigue is detected in the detection object.

[0043] Even after the fatigue detection pattern 232 is broken, the strain gauge 200 can continue to detect the strain (load) by using the strain detection pattern 231 and the conduction pattern 233.

[0044] The strain gauge 200 is attached to the center portion 20c of the stress increase portion 20 (i.e., the portion of the stress increase portion 20 where the cross-sectional area of ​​the cross section perpendicular to the tensile direction is the smallest) on both sides in the thickness direction of the strain body 100. When the strain gauge 200 is attached to the stress increase portion 20, the detection direction of the strain gauge 200 coincides with the tensile direction of the load cell LC, and the width direction of the strain gauge 200 coincides with the width direction of the load cell LC.

[0045] Specifically, the strain gauge 200 may be a fatigue detection strain gauge as described in Japanese Patent No. 5802101 (Patent Document 1) and Japanese Patent No. 5893337 issued to the applicant of the present application.

[0046] [Mounting screws 310, 320] The mounting screws 310 and 320 are each a rod-shaped screw for attaching the load cell LC to a device (a crane CR in this embodiment) that is the target of use. The mounting screw 310 extends in the tensile direction, and its lower end is fixed to the center of the upper surface of the flexure body 100. The mounting screw 320 extends in the tensile direction, and its upper end is fixed to the center of the lower surface of the flexure body 100. The central axes of the mounting screws 310 and 320 coincide with the central axis X of the flexure body 100.

[0047] [How to use the load cell LC] When using the load cell LC, the load cell LC is installed in the crane CR (FIG. 4) using mounting screws 310, 320.

[0048] The crane CR in which the load cell LC is installed (built-in) mainly includes a main body portion MB, an arm AM, a hoisting drum DR, a load cell LC, a wire rope WR, and a hook structure HS, as shown in FIG.

[0049] The main body MB is provided with a power source, a steering unit, a control unit, etc. for operating the crane CR. The arm AM is pivotable relative to the main body MB. The hoisting drum DR is a drum that hoists the wire rope WR and is provided on the main body MB. The load cell LC is attached near the tip of the arm AM. One end of the wire rope WR is connected to the load cell LC and the other end is connected to the hoisting drum DR. The hook structure HS is suspended from the wire rope WR.

[0050] Specifically, the load cell LC is installed by, for example, fitting the mounting screw 310 into a screw hole provided near the tip of the arm AM of the crane, and connecting the mounting screw 320 to the wire rope WR of the crane CR. Specifically, the mounting screw 320 and the wire rope WR can be connected by, for example, fitting an eye nut to the mounting screw 320 and passing the wire rope WR through the eye nut.

[0051] With the load cell LC attached to the arm AM, the strain gauge 200 of the load cell LC can be connected, for example, by wiring to a calculation unit (not shown) provided on the arm AM.

[0052] When the crane CR lifts a load via the hook structure HS, the load of the load is applied to the load cell LC via the wire rope WR. As a result, the strain body 100 receives a tensile load in the tensile direction, and an elongation strain occurs in the stress increasing section 20. The strain gauge 200 outputs a signal according to the amount of this elongation strain to the calculation unit. The calculation unit calculates the load of the load based on the output of the strain gauge 200. The calculation unit sends the calculated load to a control unit (not shown) of the main body section MB via wire or wirelessly.

[0053] The load cell LC is subjected to the load of the suspended load when the crane CR is in use, and also to the load of the hook structure HS when the crane CR is not in use. Fatigue occurs in the strain body 100 of the load cell LC in response to the load of the hook structure HS, which is continuously applied, and the load of the suspended load, which is intermittently applied. The calculation unit determines that fatigue has occurred in the stress increasing portion 20 of the strain body 100 based on the output of the strain gauge 200 (specifically, the increase in the resistance value described above). The calculation unit sends the determination result to a control unit (not shown) of the main body unit MB via wire or wirelessly.

[0054] The user of the crane CR can replace the load cell LC based on the detection of fatigue in the stress increase portion 20 of the strain body 100. As described above, the stress increase portion 20 is the portion of the strain body 100 where the tensile stress is the largest. Therefore, even if fatigue is detected in the stress increase portion 20, fatigue is not generated in the first base portion 11, the second base portion 12, the first connecting portion 31, and the second connecting portion 32 other than the stress increase portion 20. In this way, even after fatigue is generated in the stress increase portion 20, the load cell LC of this embodiment connects the arm AM and the wire rope WR using the first base portion 11, the second base portion 12, the first connecting portion 31, and the second connecting portion 32 that are not fatigued.

[0055] The effects of the load cell LC of this embodiment are summarized below.

[0056] In the load cell LC of this embodiment, the strain body 100 has a stress increasing section 20 configured to increase the tensile stress. A strain gauge 200 is attached to the stress increasing section 20. Therefore, based on the increased tensile stress, it is possible to detect fatigue in the strain body 100 at an earlier stage. Also, based on the increased tensile stress, it is possible to detect the strain occurring in the strain body 100 with higher accuracy.

[0057] The load cell LC of this embodiment has a first connecting portion 31 and a second connecting portion 32 that are aligned with the stress increasing portion 20 in the width direction and connect the first base portion 11 and the second base portion 12. Therefore, even after fatigue occurs in the stress increasing portion 20, the first base portion 11 (and the mounting screw 310) and the second base portion 12 (and the mounting screw 320) can be satisfactorily maintained in a connected state by using the first connecting portion 31 and the second connecting portion 32. Therefore, after fatigue is detected in the stress increasing portion 20, a sufficient time can be secured before replacement work of the load cell LC is performed.

[0058] In the load cell LC of this embodiment, the mounting screws 310, 320 and the stress increasing portion 20 are aligned along the central axis X (tensile direction), and the first connecting portion 31 and the second connecting portion 32 are arranged to have 180° rotational symmetry with respect to the central axis X. Therefore, even after fatigue (and even cracks, etc.) occurs in the stress increasing portion 20, the bending moment due to the tensile load is suppressed from occurring in the first connecting portion 31 and the second connecting portion 32. Therefore, it is possible to ensure more time until replacement work of the load cell LC is performed after fatigue has been detected in the strain body 100.

[0059] <Modification> In the load cell LC of the above embodiment, the following modifications may also be used.

[0060] In the above embodiment, the shape of the strain body 100 can be modified in various ways.

[0061] The stress increasing portion 20 of the strain generating body 100 can have any configuration in which the tensile stress is increased in a portion of the tensile direction. Such a configuration can be realized by making the cross-sectional area (area of ​​a cross section perpendicular to the tensile direction) of the stress increasing portion 20 in a portion of the tensile direction smaller than the cross-sectional area (area of ​​a cross section perpendicular to the tensile direction) of the stress increasing portion 20 at the end portion (one end or both ends) in the tensile direction. In this specification and the present invention, the portion in which the cross-sectional area (area of ​​a cross section perpendicular to the tensile direction) of the stress increasing portion 20 is smaller than the cross-sectional area (area of ​​a cross section perpendicular to the tensile direction) of the stress increasing portion 20 at the end portion (one end or both ends) in the tensile direction is called a "neck portion."

[0062] 5(a), the first through hole TH1 may have an arch shape when viewed in the thickness direction, and the second through hole TH2 may have a rectangular shape when viewed in the thickness direction. In this case, the cross-sectional area of ​​the stress increase portion 20 gradually decreases from both ends in the tensile direction toward the center in the tensile direction.

[0063] 5(b), the shape of the first through hole TH1 when viewed in the thickness direction may be an isosceles triangle with its apex located to the right of the base, and the shape of the second through hole TH2 when viewed in the thickness direction may be an isosceles triangle with its apex located to the left of the base. In this case as well, the cross-sectional area of ​​the stress increase portion 20 gradually decreases from both ends in the tensile direction toward the center in the tensile direction.

[0064] 5(c), the shape of the first through hole TH1 as viewed in the thickness direction may be a rectangle having a protruding part protruding to the right at the center in the tensile direction, and the shape of the second through hole TH2 as viewed in the thickness direction may be a rectangle having a protruding part protruding to the left at the center in the tensile direction. In this case, the cross-sectional area of ​​the stress increase portion 20 at the center in the tensile direction is smaller than the cross-sectional area of ​​the stress increase portion 20 at both ends in the tensile direction.

[0065] 5(d), the shape of the first through hole TH1 as viewed in the thickness direction may be a trapezoid whose upper and lower bases extend in the tensile direction and whose lower leg in the tensile direction is perpendicular to the upper and lower bases, and the shape of the second through hole TH2 as viewed in the thickness direction may be a shape that is axisymmetric to the first through hole TH1 with respect to the central axis X. In this case, the cross-sectional area of ​​the stress increase portion 20 gradually decreases from one end portion in the tensile direction toward the center portion in the tensile direction.

[0066] The first connecting portion 31 and / or the second connecting portion 32 of the strain body 100 may have a configuration in which the tensile stress is increased in a part of the tensile direction. In this case as well, if the tensile stress generated in the stress increasing portion 20 is larger than the tensile stress generated in the first connecting portion 31 and / or the second connecting portion 32, it is possible to ensure a sufficient time until replacement of the load cell LC is performed after fatigue is detected in the strain body 100.

[0067] In the above embodiment, the strain-flexing part 100 is in the shape of a thick flat plate, but is not limited to this. The strain-flexing part 100 may be in any shape, such as a cylindrical shape, a rectangular column shape, or a block shape.

[0068] In the above embodiment, the shape of the flexure body 100 when viewed in the thickness direction is rectangular, but is not limited to this. The shape of the flexure body 100 when viewed in the thickness direction may be any shape, such as a square, a circle, an ellipse, or the like.

[0069] In the above embodiment, the cross-section perpendicular to the tensile direction of each of the stress increasing portion 20, the first connecting portion 31, and the second connecting portion 32 is rectangular, but is not limited to this. At least one of the stress increasing portion 20, the first connecting portion 31, and the second connecting portion 32 may have any shape such as a square, a circle, or an ellipse in cross-section perpendicular to the tensile direction.

[0070] In the above embodiment, the stress increase portion 20 is located at the center in the width direction, and the first connecting portion 31 and the second connecting portion 32 are located on both sides of the stress increase portion 20 in the width direction, but this is not limited to this. The stress increase portion 20, the first connecting portion 31, and the second connecting portion 32 may be arranged in any position in the width direction. Also, in the above embodiment, the stress increase portion 20, the first connecting portion 31, and the second connecting portion 32 are arranged in the width direction perpendicular to the tensile direction, but this is not limited to this. It is sufficient that the stress increase portion 20, the first connecting portion 31, and the second connecting portion 32 are arranged in a cross direction that crosses the tensile direction.

[0071] In the flexure body 100, one of the first connecting portion 31 and the second connecting portion 32 may be omitted. Alternatively, the flexure body 100 may be provided with three or more connecting portions similar to the first connecting portion 31 and the second connecting portion 32. When a plurality of connecting portions are provided, the connecting portions are arranged on both sides in the width direction of the central axis X (i.e., on both sides of a line connecting a point where a tensile load is applied to the first base portion 11 and a point where a tensile load is applied to the second base portion 12), thereby making it possible to suppress the generation of a moment in the connecting portions even after fatigue (and even cracks, etc.) occurs in the stress increase portion 20.

[0072] Fig. 6 shows a modified example of a flexure body having a single stress increasing portion and a single connecting portion. The flexure body 500 shown in Fig. 6 has four portions defined by through holes TH penetrating the flexure body 500 in the thickness direction. The four portions are a first base portion 61, a second base portion 62, a stress increasing portion 70, and a connecting portion 80.

[0073] The through hole TH is circular when viewed in the thickness direction. The central axis of the through hole TH extends in the thickness direction and passes through the center of the tensile direction and width direction of the strain body 500. The first base portion 61 is a portion located above the upper end of the through hole TH, and the second base portion 62 is a portion located below the lower end of the through hole TH.

[0074] The stress increase portion 70 is a portion surrounded by the through hole TH, the first base portion 61, and the second base portion 62. The stress increase portion 70 is configured so that the cross-sectional area of ​​the cross section perpendicular to the tensile direction is largest at both ends in the tensile direction and gradually decreases toward the center in the tensile direction. In addition, a recess RC1 recessed to the right from the through hole TH and a recess RC2 recessed to the left from the right end of the strain body 500 are provided in the center in the tensile direction of the stress increase portion 70.

[0075] The connecting portion 80 is a portion surrounded by the through hole TH, the first base portion 61, and the second base portion 62. The connecting portion 80 is configured so that the cross-sectional area of ​​a cross section perpendicular to the tensile direction is largest at both ends in the tensile direction and gradually becomes smaller toward the center in the tensile direction.

[0076] When comparing the tensile stress occurring at the point of the stress increase section 70 with the tensile stress occurring at the point of the connecting section 80 with the smallest cross-sectional area, the tensile stress occurring at the point of the stress increase section 70 with the smallest cross-sectional area is greater because of the recesses RC1 and RC2.

[0077] In the above embodiment, the cross-sectional area (cross-sectional area of ​​a cross section perpendicular to the tensile direction) of the first connecting portion 31 and / or the second connecting portion 32 may be larger than the cross-sectional area (cross-sectional area of ​​a cross section perpendicular to the tensile direction) at the center portion 20c of the stress increase portion 20. Alternatively, the cross-sectional area (cross-sectional area of ​​a cross section perpendicular to the tensile direction) of the first connecting portion 31 and / or the second connecting portion 32 may be larger than the cross-sectional area (cross-sectional area of ​​a cross section perpendicular to the tensile direction) at the end portion 20e of the stress increase portion 20. Alternatively, the cross-sectional area (cross-sectional area of ​​a cross section perpendicular to the tensile direction) of the first connecting portion 31 and / or the second connecting portion 32 may be larger than the cross-sectional area (cross-sectional area of ​​a cross section perpendicular to the tensile direction) of the stress increase portion 20 in the entire region in the tensile direction. By increasing the cross-sectional area of ​​the first connecting portion 31 and / or the second connecting portion 32, it is possible to secure a longer time margin until the load cell LC is replaced after fatigue (further cracks, etc.) occurs in the stress increase portion 20.

[0078] In the above embodiment, any structure for attaching the load cell LC to the crane CR can be used instead of the bar-shaped mounting screws 310 and 320. Specifically, for example, as shown in FIG. 7, the mounting screws 310 and 320 may be threaded holes.

[0079] In the above embodiment, the strain gauges 200 are attached to both sides of the flexure body 100 in the thickness direction, but this is not limited to this. The number of strain gauges 200 attached to the flexure body 100 is arbitrary, and may be one.

[0080] In the above embodiment, the strain gauge 200 has both a function of detecting the strain of the flexure body 100 (the load applied to the flexure body 100) and a function of detecting the occurrence of fatigue in the flexure body 100, but is not limited thereto. Instead of the strain gauge 200, a strain detection gauge (i.e., a load detection strain gauge for detecting a load applied to a load cell) for detecting the strain of the flexure body 100 and a fatigue detection gauge (fatigue detection strain gauge) that is separate from the strain detection gauge (load detection strain gauge) and detects the occurrence of fatigue in the flexure body 100 may be used. In this case, only the fatigue detection gauge may be attached to the stress increase portion 20, and the strain detection gauge may be attached to a portion other than the stress increase portion 20, for example, the first connecting portion 31 and / or the second connecting portion 32.

[0081] The fatigue detection gauge may be configured, for example, by omitting the strain detection pattern 231 and the conductive pattern 233 from the pattern 230 in the strain gauge 200. Any other strain gauge configured so that the pattern breaks earlier than the strain detection gauge can be used as the fatigue detection gauge. The output of the fatigue detection strain gauge does not need to be used to detect the load applied to the load cell.

[0082] In the above embodiment, a strain gauge designed to have a desired fatigue life may be used as the strain gauge 200. In this case, the strain gauge detects a load and detects fatigue of the strain body 100 by breaking the pattern of the strain gauge. In this embodiment, the occurrence of fatigue in the strain body 100 can be detected early by attaching the strain gauge to the stress increasing portion 20. Furthermore, even after fatigue is detected, the first base portion 11 and the second base portion 12 can be well maintained in a connected state by the first connecting portion 31 and the second connecting portion 32.

[0083] In the above embodiment, the load cell LC is used in a crane CR, but the use of the load cell LC is not limited to this. The load cell LC can be used for any purpose of detecting a tensile load (specifically, for example, detection of a suspended load in a hoist, a chain block, etc.). The tensile direction of the load cell LC is not limited to the up-down direction, but can be any direction.

[0084] As long as the characteristics of the present invention are maintained, the present invention is not limited to the above-described embodiments, and other forms conceivable within the scope of the technical idea of ​​the present invention are also included within the scope of the present invention. [Explanation of symbols]

[0085] 11, 61 First base part; 12, 62 Second base part; 20, 70 Stress increasing part; 31 First connecting part; 32 Second connecting part; 80 Connecting part; 100, 500 Deformable body; 200 Strain gauge; 310, 320 Mounting screw CR Crane; LC Load cell

Claims

1. A load cell for detecting a load applied in the tensile direction, Strain-generating body and, A strain gauge for load detection is attached to the aforementioned strain-generating body, The system comprises a strain gauge for fatigue detection attached to the strain generating body, The strain-generating body is The first base and the second base are aligned in the tensile direction, A connecting part that connects the first base and the second base, It has a stress-increasing section that connects the first base and the second base, and is configured such that a tensile stress greater than the tensile stress generated in the connecting section in response to a load applied in the tensile direction is generated in response to the load, The connecting portion and the stress-increasing portion are aligned in a direction that intersects the tensile direction, A load cell in which the strain gauge for fatigue detection is attached to the stress-increasing portion.

2. The cross-sectional area of ​​the stress-increasing portion perpendicular to the tensile direction is smaller in the constricted portion, which is at least a part of the tensile direction, than at the end in the tensile direction. The load cell according to claim 1, wherein the strain gauge for fatigue detection is attached to the constricted portion.

3. The cross-sectional area of ​​the stress-increasing portion perpendicular to the tensile direction gradually decreases from both ends of the stress-increasing portion toward the center in the tensile direction. The load cell according to claim 1 or 2, wherein the strain gauge for fatigue detection is attached to the center of the stress-increasing portion in the tensile direction.

4. The load cell according to claim 1, wherein the strain gauge for load detection is attached to the stress increase portion.

5. The load cell according to claim 4, wherein the strain gauge for load detection and the strain gauge for fatigue detection are configured as an integrated gauge.

6. The connecting portion comprises a first connecting portion provided on one side of the stress-increasing portion in the intersecting direction, The load cell according to claim 1, further comprising a second connecting portion provided on the other side of the stress-increasing portion in the aforementioned intersecting direction.

7. The load cell further comprises a mounting section for attaching it to the target device, The mounting portion includes a first mounting portion provided on the first base of the strain generating body and a second mounting portion provided on the second base of the strain generating body. The load cell according to claim 1, wherein the stress-increasing portion, the first mounting portion, and the second mounting portion are aligned in the tensile direction.

8. A load cell for detecting a load applied in the tensile direction, Strain-generating body and, The device comprises a strain gauge attached to the strain generating body, The strain-generating body is The first base and the second base are aligned in the tensile direction, A connecting part that connects the first base and the second base, It has a stress-increasing section that connects the first base and the second base, and is configured such that a tensile stress greater than the tensile stress generated in the connecting section in response to a load applied in the tensile direction is generated in response to the load, The connecting portion and the stress-increasing portion are aligned in a direction that intersects the tensile direction, A load cell in which the strain gauge is attached to the stress-increasing portion.

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