JP2000304628A - Load measuring method and load sensor - Google Patents

Abstract

PROBLEM TO BE SOLVED: To allow a load measuring method to measure for an extended period or under water or in bad weather by opening a small hole at specified points of a member, inserting a load sensor into the small hole, and measuring a load applied on the member using the load sensor. SOLUTION: A sensor 10 comprises a cylindrical main body 11 and lids 12 and 13 for sealing its both ends, with a cable 14 protruding outside of the sensor from the lid 13. The cable 14 protects a lead wire drawn from a strain gauge 17 provided inside the main body 11. At the central part of the main body 11, many irregularities 15 are provided along its outer perimeter. The irregularities 15 collectively bear the stress applied on the small hole for housing a sensor which is provided at a pillar and beam, etc., which are to be measured. Related to the strain gauge 17, four resistance elements 19 are provided on a substrate 18. Related to a diaphragm 16, four small holes 20 are provided among the resistance elements 19 of the strain gauge 17, and the small holes 20 allow easy reception of stress concentration here, for accurate detection of acting direction.

Description

DETAILED DESCRIPTION OF THE INVENTION

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to a method for measuring loads such as tension and compression applied to structures such as columns, beams and various machines, and a load sensor used for the method.

[0002]

2. Description of the Related Art A strain gauge or a load sensor (load cell) incorporating a strain gauge is conventionally used to measure loads such as tension and compression applied to various structures such as columns, beams, and various machines. ing. At the time of load measurement, a strain gauge is attached to the surface of the structure with an adhesive or the like, or a load cell is placed directly or at a predetermined position on the structure via a hydraulic jack, etc., and the strain caused by the load applied to the structure Is detected as a change in the electric resistance of the resistance element of the strain gauge, and thereby the load is obtained.

However, such a conventional load measuring method has the following problems. In other words, in the method of directly attaching the strain gauge, it is difficult to correctly attach the strain gauge to the surface of the structure in order to perform an accurate measurement. In the case where measurement cannot be performed in rainy or rainy conditions, or when a non-uniform stress distribution occurs due to a cross-sectional defect in a structure to be measured, a strain gauge must be attached to avoid the influence.

[0004] Further, the method using the load cell has a problem that the load cell body and the hydraulic jack become large, and the load cell itself is expensive. In addition, in any case, there is a problem that a relatively long-term measurement is difficult.

[0005]

SUMMARY OF THE INVENTION The present invention solves the above-mentioned problems, and uses a small and relatively low-cost load sensor to measure a load over a long period of time or underwater or in bad weather. It proposes a measurement method.

[0006]

Means for Solving the Problems and Actions and Effects Therefor, the present invention provides a method for measuring a load applied to a structure.
A hole is drilled at a predetermined position of the member, and then a load sensor for load measurement is inserted into the hole, and the load applied to the member is measured by the load sensor. .

According to this method, the load sensor can be easily attached to the structure, and the measurement can be performed without requiring a hydraulic jack or the like. Further, measurement under water or in bad weather, or measurement over a long period of time becomes possible. Moreover, since the load sensor is inserted inside the structure,
The force (stress) acting inside the member of the structure itself can be measured with high accuracy.

In the case of this method, since a hole is drilled in the structure to be measured, stress concentration may occur at the portion, which may affect the structure itself. The small holes are generally much smaller than the size of the structure itself, and are about the size of bolt holes, so their effects can be considered almost negligible.

The present invention also relates to a load sensor used in the above-described load measuring method.

A load sensor according to the present invention comprises a cylindrical main body and a lid for sealing both sides of the main body, and a partition wall-shaped central portion inside the main body, parallel to a plane perpendicular to the center axis of the main body. A load detection unit is provided, and strain gauges having a plurality of resistance elements arranged at predetermined positions and connected to form a bridge circuit are attached to both surfaces of the load detection unit.

This load sensor is easy to mount,
Also, no hydraulic jack or the like is required for measurement.
Further, since the strain gauge itself is not exposed to the outside, it is possible to prevent its deterioration and the like. Moreover, since the strain gauge itself has a structure similar to that of the conventional so-called two-gauge method from the beginning, it is not necessary to attach a plurality of strain gauges as in the related art and to perform a connection work for these.
Calibration prior to measurement can be easily performed. Further, since the sensor has a sealed structure, measurement under water or in bad weather is also possible, and measurement over a long period of time with the sensor attached to a structure is also possible.

In a preferred embodiment of the present load sensor, the strain gauge may include a cross-shaped substrate and four resistance elements arranged orthogonally on the substrate. As a result, a bridge circuit can be easily formed, and it is not necessary to mount a plurality of strain gauges and connect them as in the related art. In addition, since the resistance element has the above-described arrangement, it is possible to accurately measure the strain gauge in accordance with the direction of the load.

In a preferred embodiment of the present load sensor, a circular small hole may be provided in the load detecting portion between the places where the adjacent resistance elements of the strain gauge are arranged. As a result, stress concentration is easily applied to the small holes, and the direction of action can be accurately detected, so that the load can be measured with high accuracy.

Further, in a preferred embodiment of the present load sensor, a hermetic seal container in which the sensor body is sealed with a lid may be used. That is, by sealing the inside of the sensor, the strain gauge can be protected from a change in the external environment and the like, and therefore, measurement can be performed underwater or under bad weather.

In a preferred embodiment of the present load sensor, the central portion of the main body has a larger outer shape than both side portions thereof, and the surface thereof can be provided with a large number of irregularities in the circumferential direction. The stress applied to the hole in which the sensor is inserted can be intensively carried, and therefore, the load can be measured with high accuracy.

Further, the strain gauge according to the present invention comprises four resistive elements arranged orthogonally on a cross-shaped substrate, and has a configuration in which these are connected so as to form a bridge circuit. Can be measured by simply attaching one or a plurality of strain gauges to a structure as it is. In addition, since the resistance element has the above-described arrangement, it is possible to accurately measure the strain gauge in accordance with the direction of the load.

[0017]

Preferred embodiments of the present invention will be described below with reference to the accompanying drawings.

FIG. 1 shows the appearance of a load sensor according to the present invention. The illustrated load sensor 10 has a cylindrical main body.
11 and lids 12 and 13 for sealing both ends thereof. A cable 14 projects from the lid 13 to the outside of the sensor. cable
Reference numeral 14 protects a lead wire drawn from a strain gauge disposed inside the main body 11. In the center of the main body 11, a number of irregularities 15 are provided along the outer periphery. Due to the unevenness, stress applied to a small hole for storing a sensor provided in a column, a beam or the like to be measured can be intensively taken. The irregularities 15 can be formed by, for example, knurling.

FIG. 2 is an exploded view of the load sensor 10 shown in FIG. A partition (curing plate) 16 for attaching a strain gauge is provided at a central portion in the main body 11. When assembling the sensor 10, the lids 12 and 13 are attached to the main body 11
After covering the outer edges 12a and 13a of each lid,
The inside of the main body is sealed by a so-called hermetic seal that is bent and pressed to cover the edges 11a and 11b of the main body. Thereby, intrusion of water or foreign matter into the sensor 10 can be prevented.

FIG. 3 shows a state in which a strain gauge is arranged on the load sensor 10. The strain gauges 17 are attached to both sides of the cure plate 16 in the main body 11, respectively. The strain gauge 17 has a configuration in which four resistance elements 19 are arranged on a substrate 18 as described later. The cure plate 16 is provided with four small holes 20 between the resistance elements 19 of the strain gauge 17. The provision of the small holes 20 makes it easy to receive stress concentration in this portion and also enables the direction of action to be detected accurately, so that the load can be measured with high accuracy. When attaching the load sensor 10 to a structure, the direction of the resistance element 19 of the strain gauge 17 should be adjusted to, for example, the load direction (or the axial direction of the structure) indicated by the arrow in FIG. I do.

FIG. 4 shows the strain gauge 17. The strain gauge 17 arranges four resistance elements 19A to 19D on a cross-shaped substrate 18 so as to be orthogonal to each other. By arranging the resistance elements in this manner, the conventional so-called 2
The same measurement as a measuring method called a gauge method or a 4-gauge method can be performed. Note that these resistance elements 19A to 19D
Are connected to each other so as to form a bridge circuit, but the method is the same as that of the conventional measurement method, and a description thereof will be omitted.

FIGS. 5 and 6 schematically show measurements using the above-described load sensor 10. FIG. 5 shows tensile and compressive loads, FIG. 6 shows bending loads, and FIG. 7 shows shear forces. Here is an example.

FIG. 5 shows long members (for example, columns and beams) 21,
This shows a case where a tensile load and a compressive load (the directions are indicated by arrows) are applied to the respective members 22, and the load sensor 10 is embedded in each member for measurement. In addition,
The crosshair on the sensor 10 is the strain gauge 17 inside the sensor 10.
(And 17 '). As shown in the figure, the direction of the strain gauge 17 is set to the direction in which a load is applied.

FIG. 6 shows a case where a bending load is applied to the cantilever beams 24 and 26 projecting from the walls 23 and 25, respectively. FIG. 7 shows a case where a shear force is applied to a long member, here, the I-shaped steel 27. Also in these cases, similarly to FIG. 5, the sensor 10 is attached to each member so that the direction of the strain gauge 17 matches the direction in which a load is applied.

In the method according to the present invention, the load detection includes:
For example, this is performed as follows. In a conventional so-called 4-gauge method, that is, a load measuring method in which four strain gauges are arranged two on each side of a structure orthogonally to each other on both sides of a structure and a bridge circuit is formed by these strain gauges, The output signal is represented by the following equation.

(Equation 1) The strain is determined by this relational expression, and the load is obtained from the result.

On the other hand, in the method according to the present invention, since the strain gauges 17 and 17 'inside the load sensor 10 already have the same configuration as the arrangement according to the 4-gauge method described above, the load is directly applied by the output signal. Can be requested. That is,

W = a · e ₀ W: load a: coefficient. Here, the coefficient a is a value unique to the load sensor, and is obtained from a relationship between the load and the output voltage obtained by performing a preliminary test prior to actual measurement.

As described above, according to the load measuring method of the present invention, the mounting of the load sensor becomes easy,
In addition, measurement with high accuracy is possible. In addition, it is possible to perform measurements underwater structures and in bad weather, and continuous measurements over a long period of time.

Further, the load sensor according to the present invention can be easily attached to a structure, and does not cause deterioration of the strain gauge. Moreover, since a configuration in which a bridge circuit is formed from the beginning is adopted, measurement and calibration prior to the measurement can be easily performed. Further, since the sensor has a sealed structure, measurement under water or in bad weather is possible, and measurement over a long period of time with the sensor attached to a structure is also possible.

[Brief description of the drawings]

FIG. 1 is a view showing the appearance of a load sensor according to the present invention.

FIG. 2 is an exploded view of the load sensor shown in FIG.

FIG. 3 is a sectional view showing the inside of the present load sensor main body.

FIG. 4 is a plan view showing a strain gauge attached to the present load sensor.

FIG. 5 is a diagram schematically showing measurement of tensile / compression loads by the present load sensor.

FIG. 6 is a diagram schematically showing measurement of a bending load by the present load sensor.

FIG. 7 is a diagram schematically showing measurement of a shear force by the present load sensor.

[Explanation of symbols]

 10 Load sensor 11 Main body of load sensor 10 12, 13 Cover of load sensor 10 14 Cable 15 Irregularities on the surface of load sensor 10 16 Partition wall (cure plate) 17 Strain gauge 18 Strain gauge substrate 19 Resistance element 20 Small hole of partition 16 21,22 Long member 23,25 Wall 24,26 Cantilever 27 I-beam

Claims (7)

[Claims] When measuring a load applied to a structure, a small hole is drilled at a predetermined position of the structure, and then a load sensor for load measurement is inserted into the small hole. A load measuring method characterized by measuring a load applied to a member. 2. A load sensor for use in the method according to claim 1, comprising: a cylindrical body; and a lid for sealing both sides of the body, the center being inside the body and perpendicular to the center axis of the body. A strain gauge having a plurality of resistance elements arranged in parallel with each other and provided in a partition shape in a partition shape, and disposed at predetermined positions and connected to each other so as to form a bridge circuit, on both surfaces of the load detection section. A load sensor characterized by being attached. 3. The load sensor according to claim 2, wherein the strain gauge comprises a cross-shaped substrate and four resistance elements arranged orthogonally on the substrate. . 4. The sensor according to claim 2, wherein a circular small hole is provided in the load detecting portion between positions where the adjacent resistance elements of the strain gauge are arranged. Load sensor. 5. The sensor according to claim 2, wherein the main body is a hermetic seal container sealed with the lid. 6. The sensor according to claim 2, wherein the central portion of the main body has an outer shape larger than both side portions thereof, and a plurality of irregularities are provided on a surface thereof in a circumferential direction. A load sensor. 7. A strain gauge for use in a load sensor according to claim 2, wherein a cross-shaped substrate and four resistance elements arranged orthogonally on the substrate. A strain gauge, wherein the resistance elements are mutually connected so as to form a bridge circuit.