Strain gauge and strain measuring structure

Abstract

To provide a strain gauge and a strain measuring structure that are difficult to reinforce a subject article.SOLUTION: A strain gauge 20 comprises a resistor 22 which changes a resistance value thereof by a strain, a gauge base 24 on which the resistor 22 is fixed, and a plurality of spikes 26 which is provided on the other surface of the gauge base 24 and which can bite into a subject article 10 for which the strain is measured.SELECTED DRAWING: Figure 1

Description

[Technical field]

[0001] The present invention relates to strain gauges and strain measuring structures. [Background technology]

[0002] The following Patent Document 1 describes a strain gauge formed by attaching fine aggregate to the surface of glass fiber reinforced plastic. The fine aggregate enhances the integration between the strain gauge and the concrete that measures the strain. [Prior art documents] [Patent documents]

[0003] [Patent Document 1] JP 2002-22437 A Summary of the Invention [Problem to be solved by the invention]

[0004] As in Patent Document 1, a structure has been conventionally required for a strain gauge to behave integrally with the measurement object whose strain is being measured. For example, a strain gauge that measures the strain on the surface of a measurement object may be attached to the surface of the measurement object using an adhesive to behave integrally with the measurement object. However, in such a structure, the adhesive may penetrate into the measurement object and reinforce the measurement object. In this case, it is difficult to accurately measure the strain of the measurement object.

[0005] In consideration of the above, the present invention provides a strain gauge and a strain measuring structure that make it difficult for an object to be reinforced. [Means for solving the problem]

[0006] The strain gauge of claim 1 comprises a resistor whose resistance value changes with strain, a gauge base having the resistor fixed to its surface, and a plurality of spikes provided on the back surface of the gauge base and capable of penetrating into an object whose strain is to be measured.

[0007] In the strain gauge of claim 1, the spikes on the back surface of the gauge base dig into the object, and the object and the gauge base become one. When strain occurs in the object in this state, the spacing between the spikes changes in response to the strain, and the gauge base expands and contracts. The resistor fixed to the gauge base then distorts, changing the resistance value of the resistor. By measuring this change in the resistance value of the resistor, the strain in the object can be detected.

[0008] In this way, the strain gauge becomes one with the object by the spikes digging into it, so there is no need to use adhesive when fixing it to the object, and the adhesive is prevented from penetrating and solidifying into the porous object, which would reinforce the surface of the object.

[0009] This improves the accuracy of detecting the strain of the object compared to a strain gauge that is fixed to the object using an adhesive.

[0010] A strain gauge according to a second aspect of the present invention is the strain gauge according to the first aspect, wherein the spikes are provided on the gauge base on both sides in the direction in which the resistor is strained.

[0011] In the strain gauge of claim 2, the spikes are provided on both sides of the resistor in the direction of strain, so there are fewer fixing points for the gauge base compared to when the spikes are provided across the entire direction of strain. This prevents the strain gauge itself from reinforcing the target object. Also, the strain gauge can be easily fixed.

[0012] The strain gauge of claim 3 is the strain gauge of claim 2, further comprising a coating film in contact with the surfaces of the gauge base and the resistor and adhered to the object.

[0013] In the strain gauge of claim 3, the coating film in contact with the surface of the gauge base and resistor is adhered to the object. Therefore, when the object is compressed and deformed, and the interval between the spikes is shortened, the gauge base is prevented from floating up from the object. This improves the detection accuracy of the strain of the object when the object is compressed.

[0014] The strain gauge of claim 3 may be the strain gauge of claim 1 or 2, further comprising a coating film in contact with the surfaces of the gauge base and the resistor and adhered to the object.

[0015] The strain measuring structure of claim 4 comprises an object whose strain is to be measured, and the strain gauge according to any one of claims 1 to 3, and the elastic modulus of the gauge base is equal to or less than (1 / 4) the elastic modulus of the object.

[0016] In the strain measurement structure of claim 4, the elastic modulus of the gauge base is smaller than the elastic modulus of the object. Therefore, the object is less likely to be reinforced by the gauge base. This improves the accuracy of detecting the strain of the object. Effect of the Invention

[0017] According to the strain gauge and strain measuring structure of the present invention, the object is unlikely to be reinforced. [Brief description of the drawings]

[0018] [Figure 1] FIG. 2A is a top view showing a strain gauge according to an embodiment of the present invention, FIG. 2B is a cross-sectional view showing the strain gauge attached to an object, and FIG. 2C is a bottom view of the strain gauge. [Diagram 2] FIG. 2A is a top view showing a strain gauge relating to a modified spike example, FIG. 2B is a cross-sectional view showing the strain gauge fixed to an object, and FIG. 2C is a bottom view of the strain gauge. [Diagram 3] 1 is a graph showing the relationship between the elastic modulus ratio and the strain ratio of an object and a strain gauge. [Figure 4]FIG. 1A is a top view showing a modified strain gauge using a coating film, FIG. 1B is a cross-sectional view showing the strain gauge attached to an object, and FIG. 1C is a bottom view of the strain gauge. [Diagram 5] FIG. 2A is a bottom view showing an example of the arrangement of spikes in a strain gauge according to an embodiment of the present invention, and FIG. DETAILED DESCRIPTION OF THE PREFERRED EMBODIMENTS

[0019] Hereinafter, a strain gauge and a strain measurement structure according to an embodiment of the present invention will be described with reference to the drawings. Components indicated by the same reference numerals in each drawing are the same components. However, unless otherwise specified in the specification, each component is not limited to one, and may be present in multiples.

[0020] In addition, explanations of configurations and symbols that are duplicated in each drawing may be omitted. Note that the present disclosure is not limited to the following embodiments, and may be implemented by making appropriate modifications, such as omitting configurations, replacing them with different configurations, or combining one embodiment and various modified examples, within the scope of the purpose of the present disclosure.

[0021] In each drawing, the directions indicated by the arrows X and Y are directions along a horizontal plane and are perpendicular to each other. The direction indicated by the arrow Z is a direction along the vertical direction (up and down direction). The directions indicated by the arrows X, Y, and Z in each drawing are assumed to be mutually consistent.

[0022] <Strain gauge> 1(A) to 1(C) show a strain gauge 20 (hereinafter referred to as a gauge 20) according to an embodiment of the present invention. The gauge 20 includes a resistor 22, a gauge base 24, and a spike 26.

[0023] The resistor 22 is a metal wire whose resistance (electrical resistance) changes with strain. When the resistor 22 is pulled, its cross-sectional area decreases and its length increases, increasing its resistance. On the other hand, when the resistor 22 is compressed, its resistance decreases. The resistor 22 is fixed to the gauge base 24 by, for example, soldering. The resistor 22 may be formed of metal foil that has been photoetched onto the gauge base 24.

[0024] The resistors 22 are laid out in a zigzag pattern in which portions extending along one direction (X direction) are repeatedly arranged on the surface of the gauge base 24. Both ends of the resistors 22 are connected to gauge leads 22A extending outside the gauge base 24. The gauge leads 22A can be connected to, for example, a Wheatstone bridge circuit (not shown).

[0025] The gauge base 24 is a resin base made of an electrical insulator, and has the resistor 22 fixed to its surface. The gauge base 24 has a rectangular shape in a plan view. The longitudinal direction of the gauge base 24 coincides with the direction along which the resistor 22 extends (the X direction).

[0026] A plurality of spikes 26 are formed on the back surface of the gauge base 24. The spikes 26 are cone-shaped protrusions formed integrally with the gauge base 24 from the same material, and protrude in a direction away from the back surface of the gauge base 24. The spikes 26 have sufficient rigidity to be able to bite into the object 10 whose strain is to be measured.

[0027] Here, the intervals and sizes of the spikes 26 can be set, for example, as follows.

[0028] The dimension of the gauge base 24 along the X direction is "L", and the dimension from the center point of the spike 26 at both ends in the X direction to the ends of the gauge base 24 in the X direction is "b x ", and the number of regions between the spikes 26 at both ends in the X direction that are divided by other spikes 26 is "n".

[0029] The dimension of the gauge base 24 along the Y direction is "W", and the dimension from the center point of the spike 26 at both ends in the Y direction to the ends of the gauge base 24 in the Y direction is "b y ", and the number of regions between the spikes 26 at both ends in the Y direction that are divided by other spikes 26 is "m".

[0030] At this time, "b x ", "b y " are, as an example, the following dimensions:

[0031] b x =b y =0.05L

[0032] In addition, the interval between the spikes 26 in the W direction, "g x " and the spacing "g y " are, as an example, the following dimensions:

[0033] g x =(L-0.1L) / n=0.9L / n g y =(W-0.1L) / m

[0034] Moreover, the diameter "φ" and height "h" of the base end of the spike 26 are, for example, as follows:

[0035] φ=L / 100 h=L / 20

[0036] As in the gauge 20 shown in Figures 1(A) to (C), the spikes 26 can be arranged at equal intervals over the entire back surface of the gauge base 24. Alternatively, as in the gauge 30 shown in Figures 2(A) to (C), the spikes 26 may be arranged partially on the back surface of the gauge base 24. In the gauge 30, the spikes 26 are provided on both sides of the gauge base 24 in the direction in which the resistor 22 is distorted. In other words, the spikes 26 are provided on both ends of the gauge base 24 in the longitudinal direction.

[0037] <Strain measurement structure> 1(B), the spikes 26 of the gauge base 24 bite into the target object 10, thereby forming a unit between the target object 10 and the gauge base 24. Examples of the target object 10 include porous materials such as gypsum board and craft paper.

[0038] In this state, when strain occurs in the object 10, the interval between the spikes 26 changes in response to the strain, and the gauge base 24 expands or contracts. Then, the resistor 22 fixed to the gauge base 24 is strained, and the resistance value of the resistor 22 changes.

[0039] The strain of the object 10 can be detected by measuring the change in resistance of the resistor 22 using a Wheatstone bridge circuit to which the gauge lead 22A is connected.

[0040] Thus, the strain measurement structure according to the embodiment of the present invention includes the object 10 for measuring strain, and the gauge 20. In this strain measurement structure, the elastic modulus of the gauge base 24 is equal to or less than ¼ of the elastic modulus of the object 10. The elastic modulus of the gauge base 24 used in the gauge 30 shown in FIG. 2(B) is also equal to or less than ¼ of the elastic modulus of the object 10.

[0041] <Action and Effects> As described above, the gauges 20 (see FIG. 1) and 30 (see FIG. 2) are integrated with the object 10 by the bite of the spikes 26, so there is no need to use an adhesive when fixing them to the object 10. Therefore, when a porous material is used as the object 10, the adhesive is prevented from penetrating and solidifying inside the object 10, thereby preventing the surface of the object 10 from being reinforced.

[0042] If the surface of the object 10 were reinforced with an adhesive, the relationship between the stress and strain of the object 10 would change, decreasing the detection accuracy of the strain of the object 10 itself. The gauge 20 or 30 according to this embodiment improves the detection accuracy of the strain of the object 10 compared to a strain gauge fixed to the object 10 with an adhesive.

[0043] In addition, in the gauge 30, the spikes 26 are provided on both sides of the resistor 22 in the direction in which the resistor 22 is distorted, so there are fewer fixing points for the gauge base 24 compared to when the spikes are provided across the entire direction of the distortion. This prevents the gauge 30 itself from reinforcing the target object 10. Also, the gauge 30 is easy to fix.

[0044] Here, Figure 3 shows a coordinate system in which the horizontal axis represents the ratio of the elastic modulus Ebase of the gauge base (including gauge base 24) to the elastic modulus Etarget of the object (including object 10) (elastic modulus ratio: Ebase / Etarget), and the vertical axis represents the ratio of the gauge base strain εbase to the object strain εtarget (strain ratio: εbase / εtarget).

[0045] In this coordinate system, the relationship between the elastic modulus ratio and the strain ratio for the combination of the object 10 and the gauge 20 (see FIG. 1) is shown by white dots, while the relationship between the elastic modulus ratio and the strain ratio for the combination of the object 10 and the gauge 30 (see FIG. 2) is shown by black dots.

[0046] As shown by these points, when comparing gauge 20 and gauge 30, when the elastic modulus ratio is equal (for example, 3 / 2), the strain ratio of gauge 20 (approximately 0.9) is greater than the strain ratio of gauge 30 (approximately 0.7) and is closer to "1."

[0047] On the other hand, when the elastic modulus ratio is (1 / 4), the strain ratio of gauge 20 (about 1.0) is greater than the strain ratio of gauge 30 (about 0.9), but both are close to "1."

[0048] In the strain measurement structure of the present invention, the elastic modulus of the gauge base 24 is ¼ or less than the elastic modulus of the object 10. In other words, the ratio of the elastic modulus Ebase of the gauge base 24 to the elastic modulus Etarget of the object 10 (elastic modulus ratio: Ebase / Etarget) is ¼ or less.

[0049] This results in a strain ratio of approximately 0.9 or greater in both the gauge 20 in which the spikes 26 are disposed across the entire back surface of the gauge base 24, and the gauge 30 in which the spikes 26 are disposed partially on the back surface of the gauge base 24.

[0050] In this way, the elastic modulus Ebase of the gauge base 24 is smaller [(1 / 4) or less] than the elastic modulus Etarget of the object 10. For this reason, the object 10 is unlikely to be reinforced by the gauge base 24. This improves the accuracy of detecting the strain of the object 10.

[0051] <Other embodiments> The gauges 20 and 30 may include a coating film 40 that is in contact with the surfaces of the gauge base 24 and the resistor 22 and is adhered to the object 10. For example, the coating film 40 shown in Figures 4(A) to (C) is in contact with the surfaces of the gauge base 24 and the resistor 22 and is disposed so as to cover the gauge base 24. It is preferable to use a material having a higher elastic modulus than the gauge base 24 for the coating film 40.

[0052] Furthermore, the coating film 40 is point-bonded to the object 10 by an adhesive 42. "Point bonding" refers to a state in which the coating film 40 and the object 10 are fixed together by the adhesive 42 that is applied in dots to the back surface of the coating film 40 or the front surface of the object 10.

[0053] By using such a coating film 40 and adhesive 42, when the object 10 is compressed and deformed, reducing the interval between the spikes 26, the gauge base 24 is prevented from lifting off the object 10. This improves the accuracy of detecting the strain of the object 10 when the object 10 is compressed.

[0054] The coating film 40 may be fixed to the object 10 using an adhesive. When an adhesive is used, the adhesive may be applied in a dotted or linear manner to the rear surface of the coating film 40 or the front surface of the object 10.

[0055] In the above embodiment, the spikes 26 are cone-shaped protrusions, but the present invention is not limited to this embodiment. For example, the spikes 26 may be pyramids (polygonal pyramids such as triangular pyramids and square pyramids), cylinders, or prisms (polygonal prisms such as triangular prisms and square prisms). Spikes 26 of various shapes may be used in combination.

[0056] In the above embodiment, the spikes 26 are integrally formed from the same material as the gauge base 24 (i.e., resin), but the present invention is not limited to this embodiment. For example, the spikes 26 may be formed from a material with higher rigidity than the gauge base 24 [e.g., metal (iron, aluminum, etc.), hard resin, ceramic, glass, etc.] and adhesively fixed to the gauge base 24. If the spikes 26 are formed from such a material, the gauges 20 and 30 can be fixed to the object 10 even if the object 10 has a hard surface. In other words, the material of the spikes 26 can be appropriately selected depending on the object 10. [Explanation of symbols]

[0057] 10. Object 20 Strain Gauge 24 Gauge Base 26 Spike 30 Strain Gauge 40 Coating membrane 42 Adhesive

Claims

1. A resistor whose resistance value changes depending on strain; a gauge base having the resistor fixed to its surface; a plurality of spikes provided on a rear surface of the gauge base and capable of penetrating into an object to be measured for strain; A strain gauge having a

2. The spikes are The resistor is provided on both sides of the gauge base in the strain direction.

2. The strain gauge according to claim 1.

3. a coating film in contact with surfaces of the gauge base and the resistor and adhered to the object; 3. The strain gauge according to claim 2.

4. An object for measuring strain; A strain gauge according to any one of claims 1 to 3, Equipped with The gauge-based elastic modulus is equal to or less than ¼ of the elastic modulus of the object. Strain measurement structure.

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