Strain measurement device

Abstract

To provide a strain measurement device that can easily and accurately measure a strain in the axial direction of a rod-shaped body such as a link rod or a column without modifying an existing facility.SOLUTION: A strain measurement device according to the present invention includes a plate-shaped strain inducer and a holder that detachably secures the plate-shaped strain inducer to a rod-shaped body. The plate-shaped strain inducer has a convex section that is convexly formed on one side and a concave section that is concavely formed on the opposite side so as to be positioned on the reverse side of the convex section. The concave section has a strain sensor arrangement part that is flat or nearly flat for attaching a strain sensor that measures a strain in the axial direction of the rod-shaped body. The strain sensor is attached to the strain sensor arrangement part. The strain measurement device includes the two strain inducers, and the respective concave sections may be fixed to the rod-shaped body so as to face each other.SELECTED DRAWING: Figure 7

Description

[Technical field]

[0001] The present invention relates to a strain measuring device for measuring the axial strain of a rod-shaped body. [Background technology]

[0002] When measuring the axial compressive or tensile load of a rod-shaped body such as a link rod or a support, the conventional method is to attach a load converter called a load cell in series coaxially with the axis of the rod to measure the load.

[0003] In addition, the strain of the rod may be measured by directly attaching a strain sensor such as a strain gauge to the surface of the rod. The strain is measured and converted into a load using material mechanics or experimental methods.

[0004] There are also displacement transducers that are designed to measure the strain of rod-shaped test pieces used in material testing of metals, etc. For example, clip-type displacement transducers are attached to grooves pre-drilled in two places on the test piece to measure the strain. The material properties, such as the elastic modulus, are investigated using the strain measured in this way and the load measured by a separate load transducer.

[0005] Additionally, for example, Patent Document 1 describes an apparatus for measuring strain in a measured object component that is mechanically distorted in response to an applied stress, the strain measuring device comprising: a mechanical strain amplification mechanism that is mechanically coupled to the measured object component and has a strain amplification portion that, when the above-mentioned stress is applied to the measured object component, either distorts significantly with a strain amplification factor greater than 1 or distorts slightly with a strain amplification factor less than 1 relative to the degree to which the measured object component is distorted; and a strain sensor that converts the mechanical strain of the strain amplification portion into a timing signal or an electrical signal.

[0006] Patent Document 2 describes a method for measuring strain electrically and magnetically by utilizing the magnetostriction phenomenon, in which both ends of a plate-shaped or thin-film element are fixed to the object to be measured for strain, and the magnetostriction of the unfixed part of the element is measured to determine the strain of the object. It also describes a strain sensor consisting of a plate-shaped or thin-film element made of magnetic metal or amorphous material, both ends of which are metallurgically or mechanically fixed to the object to be measured.

[0007] Patent document 3 describes a load measuring sensor for a rod-shaped body, characterized by comprising a stress transfer member having a portion that is tightly fixed to a rod-shaped body that deforms under load at two longitudinal locations and a portion that is not tightly fixed to the rod-shaped body, and a plurality of strain gauges attached to multiple circumferential locations at least at two longitudinal locations of the stress transfer member, and a load measuring system for a rod-shaped body, characterized by comprising a calculation unit that calculates the load of the rod-shaped body based on the signals output by the plurality of strain gauges.

[0008] Patent Document 4 describes a strain measuring device for measuring strain on a rotating body, the strain measuring device comprising: a main body portion having both ends fixed to the rotating body along the axial direction of the rotating body; a central weak portion having low rigidity within the main body portion formed in the longitudinal center of the main body portion; end weak portions having low rigidity within the main body portion formed at both longitudinal ends of the main body portion; and a link mechanism connecting the central weak portion and the end weak portions; and strain detection means attached to the central weak portion and the end weak portions for detecting strain in the axial direction, wherein the central weak portion is formed at a position different from the end weak portions in the direction perpendicular to the longitudinal direction. [Prior art documents] [Patent documents]

[0009] [Patent Document 1] JP 4-9631 [Patent Document 2] JP 4-143601 [Patent Document 3] Patent Publication No. 2011-85514 [Patent Document 4] Patent Publication No. 2020-139282 Summary of the Invention [Problem to be solved by the invention]

[0010] When measuring the axial compressive or tensile load of a rod-shaped body such as a link rod or a support, if a load cell (load converter) is attached in series coaxially with the axis of the rod, the overall length including the rod-shaped body will be longer. If the existing equipment needs to be modified in order to change the overall length of the rod-shaped body, additional costs such as modification costs will inevitably occur. In addition, since these devices cannot be easily attached or detached, a measuring device must be installed for each piece of equipment. Therefore, this method has the problem that the total cost for measurement tends to be high and it is difficult to achieve cost-effectiveness.

[0011] The method of measuring strain by directly attaching a strain sensor such as a strain gauge to the surface of a rod-shaped body involves pretreatment such as removing the paint from the sensor attachment area and polishing it, attaching a strain gauge, and setting up various measuring equipment. However, these tasks require skilled techniques and electrical expertise, making them difficult to carry out.

[0012] Clip-type displacement transducers require pre-processing, such as groove processing on the surface of the rod for mounting, making them difficult to implement. In addition, these displacement transducers are generally used for destructive testing of materials, and are intended to measure relatively large strains, with the strain of the material at the time of destruction being at most a few percent, or tens of thousands of με in με units. Therefore, they do not have the measurement accuracy or resolution to measure a measurement range of up to a few tens of με of plus minus with a resolution of 1 με or 0.1 με, and there is a problem that the measurement range does not match.

[0013] The strain measuring device described in Patent Document 1 is said to be capable of measuring minute strains of up to ±0.02%, or ±200 με in με units. However, devices capable of measuring a maximum measurement range of up to ± several tens of με with a resolution of 1 με or 0.1 με units have not yet been put into practical use due to technical, precision, and economic reasons.

[0014] The strain measurement method and the strain sensor used therein described in Patent Document 2 utilize the magnetostriction phenomenon and are described as consisting of a plate-shaped or thin-film magnetic metal or amorphous element, but such sensors have not been put to practical use for technical, precision, and economic reasons.

[0015] The load measurement sensor and load measurement system for a rod-shaped body described in Patent Document 3 utilize a divided enclosing block to attach multiple strain gauges to the rod-shaped body, but this tends to increase the limit value for reducing the rigidity of the stress conversion member, which hinders deformation of the rod-shaped body and makes it difficult to obtain sufficient measurement accuracy in an extremely small strain range of up to ± several tens of με.

[0016] Patent Document 4 describes a strain measurement method in which strain detection means attached to the end weak parts detects strain in the rotational direction, and strain detection means attached to the central weak part detects strain in the axial direction. However, there are problems with this method, such as the link mechanism being large and complex, which can easily impose installation constraints, and making the design and production expensive.

[0017] Thus, most of the conventional strain measurement means are intended to measure relatively large strains. Using them to measure minute or extremely minute strains of up to ± several tens of με is neither realistic nor practical, since the mechanisms are complex and large, there are restrictions on installation, and in many cases skilled skills and specialized knowledge are required.

[0018] Furthermore, conventional means for measuring minute strains require modifying existing equipment or providing a measuring device for each piece of equipment, making them difficult to use casually.

[0019] If there were a means for easily measuring extremely minute strains applied to a rod-shaped body in the axial direction with sufficient accuracy, it would be possible to periodically measure the operating load of, for example, a butterfly valve or globe valve, thereby understanding changes in the operating load of the valve and judging the need for maintenance, such as whether the valve can be continued in use. However, such a means has not yet been proposed.

[0020] The present invention has been made in consideration of the above points, and has as its objective the provision of a strain measuring device that can easily and accurately measure minute strains of up to ± several tens of με in the axial direction of rod-shaped bodies such as link rods and supports, with a resolution of 1 με or 0.1 με, without making any changes to existing equipment. [Means for solving the problem]

[0021] In order to solve the above problems, the present invention provides The first aspect is: A strain measuring device for measuring axial strain of a rod-shaped body, A plate-shaped strain body, a holder for removably fixing the plate-shaped strain element to the rod-shaped element; having the plate-like strain element has a convexly shaped portion on one side and a concavely shaped portion on the other side so as to be located on the back side of the convexly shaped portion, The concave molded portion has a flat or nearly flat strain sensor arrangement portion for mounting a strain sensor that measures the axial strain of the rod-shaped body, and the strain sensor is mounted on the strain sensor arrangement portion. A strain measuring device characterized by to provide.

[0022] In a second aspect, the present invention provides a method for producing a method for manufacturing a semiconductor device comprising the steps of: The plate-like strain generating body has a uniform or substantially uniform plate thickness over its entire length, and when the plate thickness is t and the height of the convex molded portion is h, the value of h / t is 0.5 or more and 4 or less. to provide.

[0023] In a third aspect, the present invention provides a method for producing a method for manufacturing a semiconductor device comprising the steps of: The above-mentioned measuring device includes two plate-shaped strain bodies to which the strain sensor is attached, and the two plate-shaped strain bodies are fixed to the rod-shaped body so that their respective concave formed portions face each other. to provide. Effect of the Invention

[0024] According to the present invention, the axial strain of a rod-shaped body such as a link rod or a support can be measured without making any changes to existing equipment.

[0025] In addition, one device can be attached to a rod-shaped body, measurements can be taken, and then removed and attached to another rod-shaped body for measurements, making it possible to measure strain without having to install a measuring device for each piece of equipment.

[0026] And, despite its simple structure that allows for such easy handling, it can accurately measure minute strains of up to ± several tens of με with a resolution of 1 με or 0.1 με. [Brief description of the drawings]

[0027] [Figure 1] FIG. 13 is a schematic diagram showing a case where the rigidity of the strain body is excessively high. [Diagram 2] FIG. 13 is a schematic diagram showing a case where the rigidity of the strain body is excessively low. [Diagram 3] FIG. 1 is a side view of a conventional strain measuring device. [Figure 4] FIG. 13 is a schematic diagram showing a conventional strain body displaced by a compressive load. [Diagram 5] FIG. 5 is a schematic diagram showing the case where the load in FIG. 4 is a tensile load. [Figure 6] 5A and 5B are schematic diagrams illustrating the relationship between the strain of a rod-shaped body and the strain of a strain sensor. [Figure 7] FIG. 2 is a side view of the strain measuring device of the present invention. [Figure 8] 4 is a schematic diagram showing a case where a distortion body of the present invention is displaced by a compressive load. FIG. [Figure 9] FIG. 5 is a schematic diagram showing the case where the load in FIG. 4 is a tensile load. [Figure 10] 2 is a schematic diagram illustrating the definition of the thickness t and bending height h of the flexure element of the present invention. FIG. [Figure 11] 1 is a graph showing the relationship between the h / t value and the strain value of the strain sensor under compressive load, obtained by FEM analysis. [Figure 12] FIG. 1 is a schematic diagram showing the case where a strain body with h / t=10 is displaced. [Figure 13] 11A and 11B are schematic diagrams illustrating a load reversal phenomenon and a case where there is no unmeasurable area. [Figure 14] FIG. 2 is a side view of the strain measuring device of the present invention. [Figure 15] FIG. 2 is a front view of a flexure body according to an example of the present invention and a comparative example. [Figure 16] FIG. 2 is a perspective view of the strain measuring device of the present invention. [Figure 17] FIG. 4 is a side view of a strain measuring device according to a comparative example. [Figure 18] FIG. 4 is a projection view of a strain measuring device according to a comparative example. [Figure 19] This is a device that generates load and strain on a rod-shaped body and measures the strain. [Figure 20] 4 is an example of a strain measurement graph of the strain measuring device of the present invention and a comparative example. [Figure 21] FIG. 1 is a diagram showing an application example 1 (butterfly valve) of the strain measuring device of the present invention. [Figure 22] FIG. 13 is a diagram showing an application example 2 (globe valve) of the strain measuring device of the present invention. [Diagram 23] FIG. 13 is a diagram showing an application example 3 (scaffolding) of the strain measuring device of the present invention. DETAILED DESCRIPTION OF THE PREFERRED EMBODIMENTS

[0028] The strain measuring device of the present invention will be described in detail below with reference to the drawings. Note that the embodiments and application examples described below are merely examples, and the present invention is not limited thereto.

[0029] The strain measuring device of the present invention has a holder that is detachably fixed to at least two places of a rod-shaped body. A compressive or tensile load applied to the rod, or a displacement caused by the load, is transmitted to this holder. In addition, both ends of a strain-generating body to which a strain sensor is attached are attached between the holders. As a result, the displacement caused in the rod is transmitted to the strain-generating body via the holder. Then, a strain sensor is placed on the strain-generating body to measure the strain of the strain-generating body. The strain of the strain-generating body is macroscopically proportional to the compressive or tensile load applied to the rod, or a strain caused by the load, and the measurement value measured by the strain sensor is converted into a load using either a material mechanics method or an experimental method, or both.

[0030] In the strain measuring device of the present invention, in order to prevent the overall length including the rod-shaped body from becoming too long and to avoid the need to modify existing equipment, a strain sensor is attached to the rod-shaped body and a flexure body is arranged in parallel to the rod-shaped body to measure strain. In this case, if the rigidity of the flexure body is excessively large, the load received by the rod-shaped body itself is distributed to the rod-shaped body and the flexure body, the generated strain becomes small, and the strain that should be measured cannot be measured accurately (measurement sensitivity decreases). This is undesirable because there is a possibility that sufficient accuracy cannot be obtained when measuring minute strains. There is also a risk that extremely minute strains cannot be measured.

[0031] Furthermore, if the stiffness of the strain generating body is large, the load received by the holder will be large, and when a particularly high load is applied, gripping problems such as reduced measurement accuracy and misalignment due to deformation of the holder will occur.

[0032] Figure 1 is a schematic diagram showing an example of a phenomenon that occurs when the rigidity of the strain body of the holder and strain sensor, which measures the strain of a rod-shaped body when a compressive load is applied, is excessively high. When a load (5) is applied to the rod-shaped body (1), the holder (2) and the strain body (30), which has high rigidity, deform as shown by the two-dot chain line. The load (5) is distributed to the rod-shaped body (1) and the strain body (30), and the strain generated in the strain body (30) becomes small as shown by the two-dot chain line. The holder (2) also displaces as shown by the two-dot chain line.

[0033] In order to avoid the above problems, it is better for the stiffness of the strain body to be low. However, if the stiffness of the strain body is made too small, the effect of the stiffness of the sensor itself cannot be ignored, and the sensor itself cannot be deformed sufficiently, which also reduces the measurement sensitivity. For example, if the stiffness of the strain body is made extremely weak, the strain body will expand and deform under tensile load, reducing the sensitivity of the sensor, and will buckle under compressive load, transmitting almost no force to the sensor and making measurement impossible.

[0034] Figure 2 is a schematic diagram showing an example of a phenomenon that occurs when the rigidity of the strain body of the holder and strain sensor that measure the strain of a rod-shaped body under a compressive load is excessively low. When a load (5) is applied to the rod-shaped body (1), the strain body (31) with low rigidity buckles as shown by the two-dot chain line.

[0035] In this way, when using a strain sensor to measure the strain of a flexure body arranged in parallel with a rod-shaped body, a flexure body having a rigidity suitable for the rigidity of the strain sensor to be used is required. Therefore, it is conceivable to obtain a flexure body having the above-mentioned appropriate rigidity by constructing the flexure body from a plate-shaped member having an appropriate thickness or an appropriate thickness and width.

[0036] In recent years, semiconductor strain sensors have been put into practical use as strain sensors capable of measuring minute strains with a resolution of 0.1με. Compared to conventional strain gauges, these sensors can measure minute strains of several tens of με with high accuracy, while the sensor itself has a metal or ceramic base plate, which gives it a high rigidity. Strain gauges are generally foil-shaped and have low rigidity, but the sensor itself has a high rigidity due to the influence of adhesives and coating materials used to attach the sensor to the object to be measured or to protect the sensor itself. In other words, it is necessary to select a plate-shaped member that is neither too thick nor too thin as a strain generating element, taking into consideration the rigidity of the sensor itself.

[0037] However, for example, the influence of the rigidity of the strain sensor cannot be reduced to zero simply by using a plate-like member that is neither too thick nor too thin. For example, when a rod-like body is subjected to a compressive load, the strain body is subjected to the compressive load and also bends. If the bend becomes convex toward the strain sensor, the strain sensor deforms in the elongation direction, generating a tensile load in a direction that cancels the compressive load, increasing the load transmission loss and reducing the strain detection sensitivity of the strain sensor, making it difficult to measure extremely small strain areas.

[0038] FIG. 3 is a schematic diagram showing an example of a phenomenon that occurs when the strain of the strain body of the holder and strain sensor, which measure the strain of a rod-shaped body when a small compressive load is applied, is small. When a load (5) is applied to the rod-shaped body (1), the strain body (32) is bent so that it is convex toward the strain sensor side, as shown by the two-dot chain line. FIG. 4 is a schematic diagram showing an enlargement of the sensor area of ​​the strain body in FIG. 3. The strain body (32) is deformed by bending as shown by the symbol 32', and the sensor (4) is displaced and deformed as shown by the symbol 4', so that the transmission loss of the load increases and the strain detection sensitivity of the strain sensor decreases. Note that if the plate thickness of the strain body is too thin compared to the rigidity of the sensor, a reverse phenomenon may occur in which the load (5) is actually compressed but is measured as a tensile load.

[0039] Such a load reversal phenomenon can also occur when a tensile load is applied. When the bending of the strain body (32) becomes concave toward the strain sensor (4) due to a tensile load (55) (32''), the strain sensor (4) is displaced and deformed toward the contraction side (4'') as shown in the schematic diagram of Figure 5, which increases the load transmission loss and reduces the strain detection sensitivity of the strain sensor. In addition, if the plate thickness of the strain body is too thin compared to the rigidity of the sensor, a reversal phenomenon may occur in which a load that is actually a tensile load (55) is measured as a compressive load.

[0040] If the load transmission loss increases and the strain detection sensitivity of the strain sensor decreases, the measurement accuracy of the small strain area of ​​about 10με decreases, and it becomes difficult to measure the extremely small strain area of ​​about 1με, which is undesirable. Furthermore, if the reversal phenomenon occurs, the measurement itself becomes difficult to establish. Even if the reversal phenomenon occurs partially only in the area of ​​small load, the area where the load reversal phenomenon occurs still becomes an area that cannot be measured, or it is one of the causes of the decrease in measurement accuracy due to the decrease in linearity, which is undesirable.

[0041] Fig. 6 is a schematic diagram illustrating the load transmission loss and load reversal phenomenon, and also illustrating the relationship between the strain of the rod-shaped body and the strain of the strain sensor. When the load transmission loss is large, the strain of the strain sensor becomes small relative to the strain of the rod-shaped body, and the slope of the graph becomes small. On the other hand, when the load reversal phenomenon occurs, the direction of expansion and contraction of the strain of the rod-shaped body is reversed, resulting in a negative slope.

[0042] As a result of extensive research into methods for suppressing or preventing the load reversal phenomenon, which results in a decrease in measurement accuracy or makes it impossible to measure, the inventors have discovered that this problem can be solved simply and effectively by forming the plate-like member that serves as the strain body into a convex shape in advance and attaching a strain sensor to the concave surface, which is the surface opposite the convex portion of the strain body.

[0043] FIG. 7 is a schematic diagram of a state in which a compressive load is applied to a strain measuring device (100) using a flexure body according to an embodiment of the present invention described later. FIG. 8 is a schematic diagram of an enlarged view of the vicinity of the sensor of the flexure body in FIG. 7. In the present invention, when a compressive load (5) is applied to the rod-shaped body (1), the flexure body (3) is strained and deformed as shown by the two-dot chain line (3'). The flexure body (3) is formed in advance into a convex shape, and the strain sensor (4) is attached to the concave surface opposite to the convex shape, so that a convex bend toward the strain sensor side is suppressed, and a load reversal phenomenon under a compressive load is prevented. In addition, by setting the convex shape of the flexure body within an appropriate range, it is possible to effectively generate a concave bend toward the strain sensor side when a compressive load (5) is applied. This bend acts in a direction that increases the compressive strain of the strain sensor, thereby reducing the load transmission loss and improving the strain detection sensitivity of the strain sensor.

[0044] FIG. 9 shows an enlarged schematic diagram of the strain sensor of the flexure body under tensile load. When a tensile load (55) is applied to the rod-shaped body (1), the flexure body (3) deforms as shown by the two-dot chain line (3''). The flexure body (3) is formed in advance into a convex shape, and the strain sensor (4) is attached to the concave surface opposite the convex shape (back side). This suppresses bending that is concave toward the strain sensor, and prevents the load reversal phenomenon, as in the case of compressive load. By setting the convex shape of the flexure body within an appropriate range, it is possible to effectively generate a convex bend toward the strain sensor when a tensile load (55) is applied. This bend acts in the direction of increasing the tensile strain of the strain sensor, thereby reducing the load transmission loss and improving the strain detection sensitivity of the strain sensor, as in the case of compressive load.

[0045] The strain sensor placement portion (7) for mounting the strain sensor on the strain body (3) is made flat or nearly flat. The shape of the strain body has a large effect on the strain detection characteristics, so high precision is required for the dimensions and molding shape, but if it is flat, it is easier to manufacture than, for example, a curved surface, and it is therefore easier to obtain a strain body with good precision.

[0046] Furthermore, when the aforementioned semiconductor strain sensor is used as the strain sensor, it becomes possible to measure minute strains with a high degree of precision equal to or greater than that of a film-shaped so-called strain gauge. However, unlike a strain gauge, this has a base plate made of metal or ceramic, and therefore, by making the strain sensor placement area flat or substantially flat, installation can be made easier.

[0047] The strain sensor arrangement portion of the present invention does not need to be completely flat, but only needs to be approximately flat to the extent that the strain sensor can be attached.

[0048] The flexure element of the present invention can be formed by bending a single metal plate so that convex and concave shapes are formed on the front and back sides.

[0049] In addition to the above, the inventors have intensively studied and examined the degree to which the effect changes depending on the degree of the convex shape, and as a result have found the optimal range for the flexure body. Figure 10 is a schematic diagram of only the flexure body of the present invention, and shows the definitions of the plate thickness t and bending height h. t is the thickness when the flexure body has a constant thickness, and h is the length (bending height) from the convex side surface that is not convexly formed to the outer surface (apex) of the convexly formed part of the flexure body.

[0050] Next, an example of a graph obtained by FEM analysis of the relationship between the amount of strain in the strain sensor generated under compressive load when h / t is changed is shown in Figure 11. As is clear from Figure 11, when h / t is 0.2 or less, that is, when the amount of convexity is small and it is close to flat, the strain in the strain sensor is on the plus side, that is, on the elongation side, and the load reversal phenomenon is not eliminated, which is not desirable.

[0051] An example of a flexure body with h / t of 10 is shown in Figure 12. When the amount of convexity in the flexure body (300) increases, the load reversal phenomenon becomes less likely to occur, but a load transmission loss occurs at the bend, making it difficult to effectively measure strain with a strain sensor. When h / t exceeds 20, the transmission loss due to this phenomenon becomes too large to be ignored, and the measurement accuracy decreases, which is undesirable.

[0052] As a result of such investigation, it was found that a more preferable value of h / t is 0.5 or more and 4 or less, and further preferably 0.8 or more and 2 or less. Fig. 13 is a schematic diagram of a graph explaining the situation in which the load reversal phenomenon is eliminated by the strain element of the present invention, the load transmission loss is reduced, and the strain detection sensitivity of the strain sensor is improved.

[0053] When a rod-shaped object is subjected to a load, the rod expands and contracts macroscopically, but if the rod is long or the load is uneven in the circumferential direction of the cross section, bending may occur. In particular, when the load applied to the rod-shaped object is small, the influence of the expansion and contraction due to bending is relatively large, and problems such as the positive and negative of the measured strain being reversed and the measurement accuracy being reduced are likely to occur.

[0054] In order to eliminate the effect of bending, it is preferable to have at least two flexure bodies equipped with strain sensors, and to arrange the flexure bodies in a pair at diagonal positions in the cross-sectional direction of the rod. In this case, when bending occurs, one expands and the other contracts, but the absolute values ​​are almost equal, so by averaging the measurement values ​​of the two sensors, the effect of bending can be offset and pure expansion and contraction strain can be measured.

[0055] FIG. 14 shows a strain measuring device in which a pair of devices similar to the strain measuring device of the present invention shown in FIG. 7 are arranged diagonally across a rod-shaped body (1).

[0056] When a strain measuring device is attached to a rod-shaped body and a flexure body is simply attached in parallel, the strain of the flexure body should be about the same as that of the rod-shaped body. In reality, however, transmission loss is likely to occur in the holder, and the strain of the flexure body is likely to be smaller than that of the rod-shaped body, which is one of the causes of reduced measurement accuracy when measuring minute strain. In this invention, the rigidity of the flexure body near where the strain sensor is attached is made smaller than the rigidity of the flexure body near where the holder is attached. This makes it possible to mechanically amplify the strain and measure compressive and tensile loads with high accuracy.

[0057] There are several possible means of mechanical amplification, but a simple and effective method is to reduce the width of the plate-shaped flexure body by making the sensor attachment area smaller. Figure 15 shows a front view of an example of a flexure body intended to amplify mechanical strain. The width (W2) of the flexure body (301) near where the strain sensor is attached is made smaller than the width (W1) of the flexure body (301) near where the holder is attached.

[0058] Any type of strain sensor can be used as long as it can measure strain, but since the strain generated in the flexure body can be extremely small, on the order of a few με, it is desirable to have a sensor that can measure minute strains. Strain gauges are generally used to measure minute strains, but as mentioned above, semiconductor strain sensors are more preferable because they can measure minute strains with the same or higher precision as the strain gauges they are measuring. Furthermore, among semiconductor strain sensors, those with built-in thermometers are even more preferable because they can correct deviations caused by temperature changes, allowing them to measure extremely minute strains with high precision and stably for a relatively long period of time.

[0059] The strain measuring device of the present invention has a holder that can be attached and detached to the rod-shaped body, and therefore can easily measure strain without modifying existing equipment or providing a device for each facility. If the holder is divided into at least two parts, it can be easily attached and detached to and from the rod-shaped body without removing one end of the rod-shaped body. For example, as shown in FIG. 14, one of the holders may be threaded and fixed to the other holder with a bolt (holder fixing screw (8)). The holder is attached to at least two places in the longitudinal direction of the rod-shaped body, and the strain generating body of the present invention having a strain sensor attached thereto is disposed between the holders, thereby forming the basic configuration of the strain measuring device of the present invention. The super-strain body may be fixed to the holder (2) by a super-strain body fixing screw (9) or the like. Although two super-strain bodies (3) are attached in the example of FIG. 14, the structure of the holder can be the same when there is only one super-strain body.

[0060] A wide variety of holder structures are applicable. For example, as a means for gripping the rod-shaped body, in addition to bolts and nuts, a hinge and lever lock can be used for fixing. Also, as a means for fixing the holder and the strain body, in addition to bolts and nuts, a wide variety of means can be applied, and as long as the holder and the strain body are substantially firmly fixed, fixing by welding or adhesive is also possible, for example.

[0061] The strain measuring device of the present invention is attached to a rod-shaped body, and the load can be displayed on a load indicator (18) connected to the strain sensor by an electric signal wiring (17) (see FIG. 21). A load indicator is not necessarily required for a load meter, and instead of a load indicator, it is possible to record the strain measurement value once in a data logger (21) or the like, and convert the recorded value into a load using Excel software on a PC (see FIG. 22). Depending on restrictions such as the measurement location, wired electric signal wiring is not necessarily required, and it is also possible to wirelessly collect data measured by the strain sensor from a remote location using a transmitter (23) and receiver (24) (see FIG. 23).

[0062] The rod-shaped body to which the strain measuring device of the present invention is attached may be either a rotating body or a non-rotating body. In the case of a rotating body, if the torsion caused by the generated torque is large, the strain body may also be torsioned, which may affect the measurement accuracy. Therefore, generally, a higher measurement accuracy can be obtained when a rod-shaped body that does not rotate is used as the target. However, even when a rotating body is used as the target, if the influence of torsion is small, the same measurement accuracy as in the case of a non-rotating body can be obtained. In addition, even if the influence of torsion occurs, if a separate device that takes this into account is installed, the same measurement accuracy as in the case of a non-rotating body can be obtained regardless of the influence of torsion. EXAMPLES

[0063] Fig. 16 shows a projection view (perspective view) of one embodiment of the present invention. The strain measuring device (102) of this embodiment has a strain element bent into a convex shape as shown in the side view of Fig. 14.

[0064] As a comparative example, a strain element (200) that has not been subjected to bending processing is shown in FIG. 17 (side view) and FIG. 18 (projection view).

[0065] Measurements were performed on these strain measuring devices using an evaluation device shown in FIG. 19. The evaluation device has load cells (11) arranged in series in the longitudinal direction of the rod-shaped body (1) to measure the load on the rod-shaped body (1), and a strain gauge (10) is directly attached to the surface of the rod-shaped body (1) to measure the strain of the rod-shaped body (1) itself. In addition to the strain gauge, the strain measuring device (102) of the present invention or a strain measuring device (200) of a comparative example is attached in parallel to the rod-shaped body (1) (FIG. 19 shows the strain measuring device of the present invention). The measured values ​​of the strain measuring device (102) of the present invention, the comparative example (200), and the strain gauge (10) are compared to evaluate the characteristics and accuracy of the measuring device. Note that rod ends (12) are arranged on both ends of the rod to minimize the influence of bending during tension and compression. One end of the rod end (12) is fixed to a fixed surface (13), and the other end is pushed and pulled to apply expansion and contraction strain to the rod-shaped body.

[0066] The details of the fabrication example and the evaluation results of FIG. 16 of the present invention, FIG. 18 of the comparative example, and FIG. 19 of the evaluation device will be described below.

[0067] First, as the flexure body of the present invention, a flat plate of SUS304 with a thickness of 3 mm was cut by laser cutting into the shape shown in FIG. 15. The total length was about 150 mm, and holes with a diameter of φ9 were provided at both ends to attach the plate to a holder with bolts. The distance between the centers of the holes was about 120 mm. The width W1 of the plate was 24 mm, the length of the central part where the strain sensor was attached was 20 mm, and the width W2 of the plate was 12 mm. A similar flexure body was also created for the comparative example. However, while the flexure body in the comparative example was left as cut out, that is, in a flat state, in the example of the present invention, it was bent as shown in FIG. 10 to have a shape with a plate thickness of t3 mm and a bending height h3 mm, that is, h / t=1. Two of these flexure bodies were produced for each of the examples of the present invention and the comparative example.

[0068] In the present invention example, the strain sensor was attached to the reverse side of the convex surface, i.e., the concave surface. In the comparative example, the strain sensor was attached to one arbitrary surface. A semiconductor strain sensor was used as the strain sensor, and one strain sensor was prepared for each strain generating body, and each was attached in the specified manner with an adhesive. The dimensions of the strain sensor are 10.5 mm in width and length, and approximately 1 mm in thickness.

[0069] Next, a 20A standard SGP carbon steel pipe for piping was prepared as a rod-shaped body and cut to a length of approximately 400 mm. It had an outer diameter of φ27.2 mm, a plate thickness of 2.8 mm, and an inner diameter of approximately φ21.6 mm. A ring was divided into two parts and bolted together as a holder to be attached to the rod-shaped body. The ring was made of iron, with an outer diameter of φ55 mm, an inner diameter of φ30 mm, and a length of 15 mm. One side of the divided ring was flattened to an arc length of approximately 29 mm in order to attach the strain body, and an M8 female thread was machined in the center of the flat part. The holder was machined to allow for clearance so that the rings would not interfere with each other when the holder was attached to the rod-shaped body, preventing it from being firmly attached to the rod-shaped body.

[0070] Nuts were welded to both ends of the rod-shaped body, and load cells were attached in series in the longitudinal direction. Furthermore, rod ends were arranged at both ends, one of which was fixed to a fixed surface. Next, a pair of strain gauges was directly attached diagonally to the surface of the rod-shaped body at a position approximately 100 mm from one end, making it possible to measure the strain of the rod-shaped body itself. Furthermore, the strain measuring device (102) of the present invention or the strain measuring device (200) of the comparative example was assembled as shown in FIG. 19. The position of the strain sensor (4) of the strain measuring device of the present invention in the longitudinal direction was approximately 100 mm from one end of the rod-shaped body (1) and on the side where the strain gauge (10) was not attached. One of the rod ends (12) was fixed to a fixed surface (13), and the other end was pushed and pulled to apply a compressive and tensile load to the rod-shaped body (1), and the expansion and contraction strain caused by the load was measured by the strain gauge (10) and the strain sensor (4).

[0071] The measurement results thus obtained are integrated and graphed in FIG. 20. In FIG. 20, the horizontal axis shows the load of the load cell, and the vertical axis shows the strain of each sensor. Line A shows the strain of the rod-shaped body measured by directly attaching a strain gauge to the surface of the rod-shaped body. The rod-shaped body expands due to a tensile load, and contracts due to a compressive load, and the relationship is almost linear. According to the evaluation device, when the rod-shaped body was stretched with 500N, an expansion strain of 12.5με was measured, and when the rod-shaped body was compressed with -500N, a contraction strain of -12.5με was measured. First, the strain measuring device of the comparative example showed a line B. Although the load reversal phenomenon did not occur in line B, it can be seen that the load transmission loss was large, with a loss of more than 80% compared to the strain of the rod-shaped body, and it was reduced to about one fifth. On the other hand, the strain measuring device of the present invention showed the result of line C. In the example of the present invention, the load reversal phenomenon does not occur, and the load transmission loss is small, reducing the loss to about 20% relative to the strain of the rod-shaped body, which is approximately 80%.

[0072] The results in FIG. 20 demonstrate that the present invention makes it possible to measure extremely minute strains of about 10 με occurring in a rod-shaped body with a resolution of 0.1 με.

[0073] An example of application to an actual device is shown below.

[0074] (Application example 1) FIG. 21 shows an example of application of a butterfly valve in a fluid flow control device. The butterfly valve (14) is driven to swing in combination with a hydraulic actuator that has excellent ability to maintain its opening. Arms (16) are attached to the shafts of the butterfly valve (14) and the hydraulic actuator (15), and the arms (16) are connected by a link rod to transmit the driving force. The driving force is measured by installing the strain measuring device (101) of the present invention at the midpoint of the link rod. In the example of FIG. 21, the load is displayed on the load indicator (18) via the electric signal wiring (17) from the strain sensor.

[0075] (Application example 2) Figure 22 shows an example of application of a fluid flow control device using a globe valve (19). The globe valve is combined with a diaphragm actuator (20) powered by air pressure or a spring to perform reciprocating motion. The driving force is measured by installing a strain measuring device (100) of the present invention at any position on the rod-shaped body (1) connecting the valve stem of the globe valve (19) and the diaphragm actuator (20). In the example of Figure 22, the strain value is recorded by a data logger (21) via an electric signal wiring (15) from the strain sensor.

[0076] (Application example 3) The rod to which the strain measuring device of the present invention is attached is not necessarily limited to a rod that transmits driving force, but can also be a statically installed object such as a support. For example, as shown in Fig. 23, by installing the strain measuring device (100) of the present invention on a rod-shaped body (1) that supports a scaffolding, it is possible to measure the force received from the scaffolding. In the example of Fig. 23, data is first sent from the strain sensor to a transmitter (23) via an electric signal wiring (17), and then the data is received by a receiver (24). [Industrial Applicability]

[0077] Valves such as butterfly valves and globe valves may experience changes in driving force due to deterioration from long-term use or unexpected events such as the ingestion of foreign objects, and depending on the severity of the event, malfunctions may occur, requiring emergency maintenance or replacement. By periodically measuring the operating load of the valve, it is possible to grasp changes in the operating load of the valve and determine whether maintenance is required, such as whether it can be used continuously. This makes it possible to prevent unexpected malfunctions and extend the lifespan by optimizing the replacement time.

[0078] Some valves are required to have specifications that require a pressure load to be applied in the fully closed position to prevent leakage when fully closed. If the pressure load is too small, leakage when fully closed occurs, but if it is too large, the valve or actuator will be overloaded, shortening the machine's lifespan and causing sudden failures. In the past, there was no load meter to measure the pressure load, so it was necessary to rely on experience and intuition, but by using the strain measuring device of the present invention, it is easy to set the pressure load within the appropriate range.

[0079] The strain measuring device of the present invention can also monitor the condition by constantly measuring. By monitoring the condition, it is possible to respond to sudden changes during operation, and by analyzing the data, it is also possible to optimize the timing of maintenance. For long-term measurements, it is preferable to perform temperature compensation to reduce the effects of temperature drift.

[0080] Furthermore, the strain measuring device of the present invention can be used not only for industrial equipment but also for research purposes. When the rod-shaped object to be measured is a standard steel material such as JIS standard, it is possible to convert the strain of the strain sensor into a load using dimensional information such as Young's modulus and cross-sectional area of ​​the material described in the standard, and it is possible to measure extremely small loads in parts that have been difficult to measure up to now with relative ease and precision.

[0081] As described above, the present invention has extremely high industrial applicability. [Explanation of symbols]

[0082] 1 Rod-shaped body 2 Holder 3, 30, 31, 32, 300, 301 strain body 4 Strain Sensor 5, 55 Load 6. Strain-generating body holder attachment part 7 Strain sensor arrangement section 8 Holder fixing screw 9. Strain body fixing screw 10 Strain Gauge 11 Load Cell 12 Rod end 13 Fixed surface 14 Butterfly valve 15 Hydraulic Actuator 16 Arm 17 Electrical signal wiring 18 Load indicator 19 Globe valve 20 Diaphragm Actuator 21 Data Logger 22 Scaffolding 23 Transmitter 24 Receiver 100, 101, 200 Strain measuring device

Claims

1. A strain measuring device for measuring axial strain of a rod-shaped body, A plate-shaped strain body, a holder for removably fixing the plate-shaped strain element to the rod-shaped element; having the plate-like strain element has a convexly shaped portion on one side and a concavely shaped portion on the other side so as to be located on the rear side of the convexly shaped portion, The concave molded portion has a flat or nearly flat strain sensor arrangement portion for mounting a strain sensor that measures the axial strain of the rod-shaped body, and the strain sensor is mounted on the strain sensor arrangement portion. A strain measuring device characterized by the above.

2. 2. The strain measuring device according to claim 1, wherein the plate-like strain generating body has a constant or substantially constant plate thickness over its entire length, and the value of h / t is 0.5 or more and 4 or less, where t is the plate thickness and h is the height of the convexly formed portion.

3. 3. The strain measuring device according to claim 1 or 2, comprising two plate-shaped strain elements to which the strain sensors are attached, and the two plate-shaped strain elements are fixed to the rod-shaped body so that their respective concave formed portions face each other.

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