JP3070022U - Welding type strain gauge - Google Patents

Abstract

(57) [Problem] To provide a welding type strain gauge capable of suppressing a shear stress at a fixing portion with a measurement object and reducing a variation in gauge characteristics. SOLUTION: A gauge base 1 having a void portion 13 formed therein.
0 and the first and second grooves 14 and 15 formed continuously on one surface of the gauge base 10 through the gap 13.
An optical fiber 11 fixedly extending in the first and second grooves 14 and 15, and a gap 13 extending in a direction orthogonal to the axial direction of the optical fiber 11 in the first and second grooves 14 and 15. Are formed in the gauge base 10 by step portions 16 formed on both sides of the thin portion 17, and a thin portion 17 located around the void portion 13 and a thick portion 18 thicker than the thin portion 17.
And a constricted portion 20 formed in the thin portion 17 of the gauge base 10, and by applying the (spot) welded portion 12 to the thin portion 17 along the step 16, the gauge base 10 and the object to be measured are provided. 19 are fixed.

Description

[Detailed description of the invention]

[0001]

[Technical field to which the invention belongs]

 The present invention relates to strain gauges, and more particularly to strain gauges used in industrial process measurement, strain measurement in linear motor cars, transmission lines, generators, etc., in strong electromagnetic field noise environments, and in civil engineering related measurements in lightning strike environments. .

[0002]

[Prior art]

 There are optical fiber type strain gauges as shown in FIGS. 8 and 9. The structure shown in FIG. 8 has an FBG (Fiber Bragg Grating) type optical fiber type strain gauge which detects a wavelength change of light due to strain. This is adopted in an FPI (Fabry Perot Interferometer) type optical fiber type strain gauge which detects a change in air gap between a fiber end and a mirror by light intensity or interference. The structure shown in FIG. 9 is employed in a microbend type optical fiber type strain gauge for detecting bending loss of an optical fiber. In these optical fiber strain gauges, conventionally, a gauge base 100 to which a sensing element 101 made of an optical fiber is attached is fixed to an object to be measured by performing spot welding along an axial direction of the sensing element 101. I was

[0003]

[Problems to be solved by the invention]

 Here, when the object to be measured is distorted, a force corresponding to the tensile rigidity of the gauge base 100 is applied, and the spot welded portion 102 bears the added load, so that the shear stress of the spot welded portion 102 increases. I do. Therefore, in order to transmit the strain of the measurement object to the sensing element 101 correctly, it is desirable to reduce the tensile rigidity of the gauge base 100 as much as possible. Certainly, as shown in FIG. 9, if the voids 103 are formed, the rigidity is reduced, but it is still insufficient to properly transmit the strain.

Further, in the conventional strain gauge, since a welding portion is provided in the axial direction as described above, a force other than a force balanced with an external force, that is, an internal force is generated.

[0005] As described above, in the conventional strain gauge, high shear stress is generated in the fixed portion, which is the spot welded portion 102, so that plastic deformation or peeling is liable to occur, and characteristics of the strain gauge vary. Such variations in characteristics were treated as differences in welding skills, and no specific countermeasures were taken.

[0006] An object of the present invention is to provide a strain gauge capable of suppressing a shear stress at a portion where the gauge is fixed to an object to be measured and reducing variations in gauge characteristics.

[0007]

[Means for Solving the Problems]

 In order to solve the above-mentioned object, a strain gauge according to the present invention includes a gauge base having a gap formed therein and first and second continuously formed through the gap on one surface of the gauge base. A groove, a sensing element extending fixedly in the first and second grooves, and a fixing means for fixing the gauge base and the object to be measured by the sensing element in the first and second grooves. It is characterized by having a welded part to which a fixing force can be applied along a direction perpendicular to the axial direction.

The strain gauge according to the present invention includes a gauge base having a gap formed therein, and first and second grooves formed continuously on one surface of the gauge base through the gap. A sensing element fixed to the first and second grooves and extending; and a welded portion provided in the first and second grooves along a direction orthogonal to an axial direction of the sensing element. It is characterized by.

Further, the strain gauge according to the present invention includes a gauge base having a gap formed therein, and first and second grooves formed continuously on one surface of the gauge base through the gap. A sensing element fixedly extended in the first and second grooves; and a sensing element extending in a direction orthogonal to an axial direction of the sensing element in the first and second grooves and formed on both sides of the gap. The gauge base is defined by a step, and has a thin portion located around the gap and a thick portion thicker than the thin portion.

[0010] Further, the strain gauge according to the present invention includes a gauge base having a gap formed therein, and first and second grooves formed continuously on one surface of the gauge base through the gap. A sensing element fixedly extended in the first and second grooves; and a sensing element extending in a direction orthogonal to an axial direction of the sensing element in the first and second grooves and formed on both sides of the gap. A thin portion positioned around the gap portion, a thick portion thicker than the thin portion, and a constricted portion formed in the thin portion of the gauge base. It is characterized by having.

The strain gauge according to the present invention includes a gauge base having a gap formed therein, and first and second grooves formed continuously on one surface of the gauge base through the gap. A sensing element fixed to the first and second grooves and extending, and a step portion extending in the width direction of the gauge base and formed on both sides of the gap portion, and formed in the gauge base in a partitioned manner; It has a thin portion located around the gap and a thick portion thicker than the thin portion, and extends along a direction orthogonal to the axial direction of the sensing element in the first and second grooves. The invention is characterized in that the gauge base and the object to be measured are fixed by a clip for applying a clamping force.

According to such a device, the strain gauge and the object to be measured are fixed by the fixing force acting along the direction orthogonal to the axial direction of the sensing element. This is the distance between the fixed portions. As a result, the tensile stiffness is reduced and the internal force is reduced, so that the shear stress at the portion fixed to the object to be measured is suppressed, and variations in gauge characteristics can be reduced.

[0013]

[Embodiment of the invention]

 Hereinafter, embodiments of the present invention will be described more specifically with reference to the drawings. Here, in the attached drawings, the same members are denoted by the same reference numerals, and duplicate description is omitted. The embodiment of the present invention is a particularly useful form in which the present invention is implemented, and the present invention is not limited to the embodiment.

FIG. 1 is a plan view showing a strain gauge according to an embodiment of the present invention, FIG. 2 is a side view showing the strain gauge of FIG. 1 together with an object to be measured, and FIG. 3 is a load on the strain gauge of FIG. FIG. 4 is a graph showing measurement results of load characteristics of a conventional strain gauge as a comparative example, and FIG. 5 is a shear force at a spot weld between the strain gauge of FIG. 1 and a conventional strain gauge. FIG. 6 is a plan view showing a strain gauge according to another embodiment of the present invention, and FIG. 7 is a side view showing the strain gauge of FIG. 6 together with an object to be measured.

As shown in FIGS. 1 and 2, a strain gauge according to the present embodiment has a gauge base 10 having an H-shaped void portion 13 formed therein and having a rectangular shape as a whole, and one surface of the gauge base 10. There are provided first and second grooves 14 and 15 formed continuously with a gap 13 therebetween, and an optical fiber (sensing element) 11 which is fixed to these grooves by, for example, an adhesive and extends. The optical fiber 11 is bent in the gap 13 and fixed to the first and second grooves 14 and 15.

The gauge base 10 has a step 16 formed in the first and second grooves 14 and 15 in a direction perpendicular to the axial direction of the optical fiber 11 and formed on both sides of the gap 13. A thin portion 17 located around the gap 13 and a thick portion 18 thicker than the thin portion 17 are defined. A welded portion 12 for fixing the gauge base 10 and a measurement object 19 such as a steel material by spot welding, for example, is formed along the step 16 on the thin portion 17 side.

Further, a constricted portion 20 is formed in the thin portion 17 of the gauge base 10. Thereby, the rigidity of the thin portion 17 is reduced, and the gauge base 10 is easily deformed according to the strain of the measurement object 19.

It should be noted that various forms can be adopted for welding for fixing the gauge base 10 and the measuring object 19, and not only welding such as spot welding and gas welding of the present embodiment but also welding. It is possible to fix both by various fusion welding and brazing techniques.

Here, in the present embodiment, the length of the gauge base 10 in the longitudinal direction is about 20 mm to 30 mm, the thickness of the thick portion 18 is 0.6 mm, and the thickness of the thin portion 17 is 0.2 mm. ing. The distance G between the first groove 14 and the second groove 15 is 3 mm. Note that the present invention is not limited to such dimensions.

Next, a method of using the strain gauge of the present embodiment will be described.

The strain gauge according to the present embodiment transmits the strain of the measurement object 19 to the bent portion A of the optical fiber 11 provided as a detection unit and detects the strain. That is, in order to use the strain gauge of the present embodiment, as shown in FIGS. 1 and 2, a gauge base 10 is fixed to an object 19 to be measured, and one end of an optical fiber 11 is connected to a light source side such as an LED (not shown). ), And the other end is connected to a light detection side (not shown) such as a PD.

When a stress is applied to the measurement object 19 to generate a strain, the gauge base 10 is similarly pulled or compressed. As a result, the gap G between the gaps 13 increases in the case of tension and decreases in the case of compression (see FIG. 3). When the gap G between the gaps 13 increases or decreases, the amount of bending of the optical fiber 11 in the gaps 13 changes, and the amount of transmitted light changes. That is, in the case of tension, the radius of curvature of the bent portion A increases, and the loss decreases. As a result, the amount of transmitted light increases. On the other hand, in the case of compression, the radius of curvature of the bent portion A decreases, and the loss increases. As a result, the amount of transmitted light decreases. Therefore, the amount of distortion can be measured by detecting this change in the amount of light with a detecting means including a PD or the like.

As described above, according to the strain gauge of the present embodiment, not only tensile strain but also compressive strain can be measured, and furthermore, crack displacement can be measured.

Note that the radius of curvature of the optical fiber 11 within the gap G between the gaps 13 may be changed to change the detection sensitivity according to the type of the measurement object 19. For example, when the measurement object 19 is concrete with small strain, the radius of curvature may be small, and when the measurement object 19 is iron with large strain, the radius of curvature may be large.

Here, in the strain gauge of the present embodiment, as shown in FIGS. 1 and 2, the strain gauge extends in a direction orthogonal to the axial direction of the optical fiber 11 in the first and second grooves 14 and 15. The gauge base 10 and the object 19 to be measured are fixed by performing spot welding on the welded portion 12 formed on the thin portion 17 side along the step portion 16 formed as described above.

When the strain gauge and the measuring object 19 are fixed by the fixing force acting in the direction orthogonal to the axial direction of the optical fiber 11 as described above, the gauge length is fixed in the axial direction of the optical fiber 11. It is the distance between clubs. As a result, the tensile stiffness is reduced and the internal force is reduced, so that the shear stress at the portion where the measurement object 19 is fixed is suppressed, and the variation in gauge characteristics is reduced.

Further, since the gauge length is the distance between the fixed portions in the axial direction of the optical fiber 11, the uncertainty of the gauge length in temperature compensation using linear expansion is eliminated.

Further, the welded portion along the direction orthogonal to the axial direction of the optical fiber 11 in the first and second grooves 14 and 15 only by moving the spot welder along the stepped portion 16, for example. Since 12 can be welded to the measurement object 19, the work of attaching the strain gauge can be facilitated.

Next, the following two types of experiments were performed on the strain gauge of the present embodiment to confirm its characteristics.

That is, the load characteristics of three strain gauges shown in FIG. 1 described above were manufactured by the same procedure. Here, as a comparative example, load characteristics of three conventional strain gauges shown in FIG. 9 manufactured by the same procedure were examined. The measurement results of the load characteristics of the strain gauge of FIG. 1 are shown in FIG. 3, and the measurement results of the load characteristics of the strain gauge of FIG. 9 are shown in FIG.

As is clear from these figures, it can be seen that the variation in characteristics of the strain gauge of the present embodiment is extremely smaller than that of the conventional strain gauge.

Further, the distribution of the shearing force in a weld between the strain gauge of FIG. 1 and the strain gauge of FIG. 9 was examined. The result is shown in FIG. In FIG. 5, T indicates the thickness (mm) of the gauge base, the perpendicular direction indicates the direction orthogonal to the axial direction of the optical fiber, and the free indicates that the central portion of the gauge base has been removed. . The circles in the graph indicate the data on the strain gauge of the present application, and the others are the measured data on the conventional strain gauge.

As is apparent from FIG. 5, it is understood that the shear force applied to the welded portion is much smaller in the strain gauge of the present embodiment than in the conventional strain gauge.

Regarding the reaction force when a strain amount of 1000 με is applied, in a conventional strain gauge, 7.5 kgf when the thickness of the gauge base is 0.2 mm and 3 kg when the thickness of the gauge base is 0.1 mm. When the central portion of the gauge base was shaved off at 7 kgf and 0.2 mm, it was 0 kgf and 0.2 mm at 10.2 kgf in the direction perpendicular to the axial direction of the optical fiber. Further, in the strain gauge of the present application, when the thickness of the gauge base was 0.2 mm, it was 0.42 kgf in the direction orthogonal to the axial direction of the optical fiber.

Thus, it can be seen that the strain gauge of the present embodiment has significantly reduced stress at the welded portion as compared with the conventional strain gauge.

Next, another embodiment of the present invention will be described with reference to FIGS. 6 and 7. FIG.

As shown in the drawing, a strain gauge according to another embodiment includes a gauge base 10 having a cavity 13 formed therein, and first and second grooves 14 formed continuously through the cavity 13. , 15, an optical fiber 11 fixed to the first and second grooves 14, 15, and a stepped portion 16 extending in the width direction of the gauge base 10 and formed on both sides of the gap 13. The gauge portion 10 includes a thin portion 17 and a thick portion 18, and a narrow portion 20 formed in the thin portion 17 of the gauge base 10.

The strain gauge according to the present embodiment is configured such that, for example, in a characteristic inspection of a product, a clip (fixing means) is provided along the direction perpendicular to the axial direction of the optical fiber 11 on the side of the thick portion 18 where clipping is easy. ) 21 is attached, and the gauge base 10 and the measurement object 19 are temporarily fixed by applying a clamping force.

As described above, as the fixing means for fixing the gauge base 10 and the object 19 to be measured, not only the welding and bonding described above but also the clip 21 can be used. If the clip 21 is used, the strain gauge is detached from the measurement object 19 just by removing the clip 21, and thus the strain gauge used for the characteristic inspection of the product can be reused. become. In FIG. 6, the clip (fixing means) 21 is attached to the thick portion 18, but it goes without saying that the clip 21 may be attached to the thin portion 17 along the step 16.

Further, in the present invention, the fixing means is not limited to the welding or the clip 21 alone, and various other members such as an adhesive can be applied. That is, the fixing means in the present invention applies a fixing force along the direction orthogonal to the axial direction of the optical fiber 11 in the first and second grooves 14 and 15 to apply the fixing force to the gauge base 10 and the object to be measured. 19 may be fixed.

As described above, the present invention has been described based on the embodiments. However, the present invention is not limited to the above-described embodiments, and can be variously changed without departing from the gist of the present invention.

For example, the thin portion 17 and the thick portion 18 defined by the constricted portion 20 and the stepped portion 16 may not be formed. However, if these are formed, the gauge base 10 is likely to be deformed due to the strain of the measurement object 19, so that a more accurate measurement of the strain amount can be performed.

Further, in this specification, the direction perpendicular to the axial direction of the optical fiber 11 does not mean only a direction that intersects the axial direction of the optical fiber 11 at right angles in a strict sense. That is, if the internal force due to the strain generated in the measurement object 19 is within an angle at which the gauge base 10 does not generate, the direction intersecting the axis direction of the optical fiber 11 at an angle close to a right angle is included.

Further, in the present embodiment, the continuous first and second grooves 14 and 15 are formed in the gauge base 10. However, in the present invention, the number of grooves is limited to the present embodiment. Not something. That is, another continuously formed groove may be further provided through the gap 13 to arrange a plurality of optical fibers 11.

Note that the first and second grooves 14 and 15 do not necessarily have to be formed in a straight line with each other as in the present embodiment. That is, the first and second grooves 14 and 15 may be formed on mutually different straight lines, or may be formed so as to be inclined with respect to the longitudinal direction of the gauge base 10.

In this embodiment, the optical fiber 11 is fixed to the first and second grooves 14 and 15 so as to be bent at the gap 13, but is fixed so as to be straight at the gap 13. May be.

Further, two optical fibers 11 on the light emitting side and the light receiving side are attached substantially in parallel with their end faces facing the gap 13, and the light emitting side of the light emitting side is positioned opposite the end face with the gap 13 interposed therebetween. It is also possible to mount a reflector that reflects the irradiation light from the optical fiber 11 and guides the irradiation light to the optical fiber 11 on the light receiving side, and measures the amount of distortion based on a change in the reflected light.

In the present embodiment, the optical fiber 11 is used as the sensing element, and an optical fiber type strain gauge using the bending loss of the optical fiber 11 is described. May be used. In this case, the amount of strain is measured using the change in the electrical resistance of the conductor caused by the strain transmitted from the measuring object 19.

[0049]

[Effect of the invention]

 As is clear from the above description, the present invention has the following effects.

That is, since the fixing force is applied along the direction orthogonal to the axial direction of the sensing element in the first and second grooves to fix the gauge base and the object to be measured, the gauge length is increased. Is the distance between the fixed parts in the axial direction of the sensing element, the tensile rigidity is reduced, and the internal force is reduced. Therefore, the shear stress at the fixed part with the object to be measured is suppressed, and the variation in gauge characteristics is reduced.

Further, since the gauge length is the distance between the fixed portions in the axial direction of the sensing element, the uncertainty of the gauge length in temperature compensation using linear expansion is eliminated.

If a constricted portion or a thin portion is formed, the gauge base is easily deformed in accordance with the distortion of the object to be measured, so that it is possible to measure the strain amount with higher accuracy.

By simply moving the welding machine along the step portion and moving the inside of the thin portion, the welding portion along the direction orthogonal to the axial direction of the sensing element in the first and second grooves can be welded. It becomes possible to facilitate the mounting work of the pendulum gauge.

In a product inspection or the like, if a clip is used as a temporary fixing means, the strain gauge is detached from the measurement target simply by removing the clip, so that the strain gauge can be reused. Will be possible.

[Brief description of the drawings]

FIG. 1 is a plan view showing a strain gauge according to an embodiment of the present invention.

FIG. 2 is a side view showing the strain gauge of FIG. 1 together with an object to be measured.

FIG. 3 is a graph showing measurement results of load characteristics of the strain gauge of FIG.

FIG. 4 is a graph showing measurement results of load characteristics of a conventional strain gauge as a comparative example.

FIG. 5 is a graph showing a shear force distribution in a spot weld between the strain gauge of FIG. 1 and a conventional strain gauge.

FIG. 6 is a plan view showing a strain gauge according to another embodiment of the present invention.

FIG. 7 is a side view showing the strain gauge of FIG. 6 together with an object to be measured.

FIG. 8 is a plan view showing an example of a conventional strain gauge.

FIG. 9 is a plan view showing another example of a conventional strain gauge.

[Explanation of symbols]

 Reference Signs List 10 Gauge base 11 Optical fiber (sensing element) 12 (Spot) welded part 13 Air gap part 14 First groove 15 Second groove 16 Step part 17 Thin part 18 Thick part 19 Object to be measured 20 Constricted part 21 Clip (fixed) Means) 100 Gauge base 101 Sensing element 102 Spot welded part 103 Void part A Bent part G Interval

Continued on the front page (72) Inventor Taro Uesugi 3-5-1, Chofugaoka, Chofu-shi, Tokyo Inside Kyowa Dengyo Co., Ltd. (72) Eriko Fujishima 3-5-1, Chofugaoka, Chofu-shi, Tokyo Kyowa Dengyo Co., Ltd.

Claims (5)

[Utility model registration claims] A gauge base having a gap formed therein; first and second grooves formed continuously on one surface of the gauge base through the gap; The sensing element fixed to the groove and the fixing means for fixing the gauge base and the measuring object reduce the fixing force along the direction orthogonal to the axial direction of the sensing element in the first and second grooves. A welding type strain gauge having a welded portion to be added. 2. A gauge base having a gap formed therein, first and second grooves formed continuously on one surface of the gauge base through the gap, and a first and a second groove formed on the gauge base. A sensing element fixed to the groove and extending;
And a welded portion provided along a direction orthogonal to the axial direction of the sensing element in the second groove. 3. A gauge base having a gap formed therein, first and second grooves formed continuously through the gap on one surface of the gauge base, and a first and second groove. A sensing element fixed to the groove and extending;
A thin portion extending in a direction orthogonal to the axial direction of the sensing element in the second groove and defined in the gauge base by a step formed on both sides of the gap, and located around the gap; And a thick part thicker than the thin part. 4. A gauge base having a gap formed therein, first and second grooves formed continuously on one surface of the gauge base through the gap, and a first and a second groove. A sensing element fixed to the groove and extending;
A thin portion extending in a direction orthogonal to the axial direction of the sensing element in the second groove and defined in the gauge base by a step formed on both sides of the gap, and located around the gap; And a thick part thicker than the thin part and a constricted part formed in the thin part of the gauge base. 5. A gauge base having a gap formed therein, first and second grooves formed continuously on one surface of the gauge base through the gap, and a first and second groove. A sensing element fixed to the groove and extending in the width direction of the gauge base, formed in the gauge base by a step formed on both sides of the gap, and a thin portion positioned around the gap; A thickness portion having a thickness greater than the thickness of the thin portion, and measuring the gauge base with the clip by applying a clamping force along a direction orthogonal to an axial direction of the sensing element in the first and second grooves. A welding type strain gauge, wherein an object is fixed.