JP2021004865A - Multi-component force gauge - Google Patents

Abstract

PROBLEM TO BE SOLVED: To provide a force meter having increased bending rigidity. Perhaps a force meter comprises a substrate. Perhaps the force gauge is a plurality of cylinders arranged on the substrate, the central axis of which is perpendicular to the surface of the substrate. Perhaps the force gauge has strain gauges located on each of a plurality of cylinders. Perhaps the force gauge has a top plate that is commonly connected to the top of a plurality of cylinders and is arranged parallel to the substrate. A plurality of cylinders are arranged apart from each other. [Selection diagram] Fig. 2

Description

The techniques disclosed herein relate to a maybe force meter capable of measuring forces in the X, Y, Z axis directions.

Perhaps a force meter capable of measuring forces in the X, Y, and Z axis directions of an object on which a force is acting and moments around three axes is known. Patent Document 1 discloses a maybe force meter in which one cylinder is arranged between two flat plates. A plurality of strain gauges are attached to the side surface of one cylinder.

Japanese Unexamined Patent Publication No. 3-51732

When a force gauge is used in a part where a relatively large bending moment is applied (eg, the top of a rigidly connected pier), it is necessary to increase the allowable moment by increasing the bending rigidity. In the existing multi-force meter as shown in Patent Document 1, it is necessary to increase the cross-sectional shape in order to increase the bending rigidity. However, when the cross-sectional shape is increased, the compressive rigidity is also increased proportionally, so that the strain detection sensitivity with respect to the compressive force is lowered.

One embodiment of the maybe force meter disclosed herein comprises a substrate. Perhaps the force gauge is a plurality of cylinders arranged on the substrate, the central axis of which is perpendicular to the surface of the substrate. Perhaps the force gauge has strain gauges located on each of a plurality of cylinders. Perhaps the force gauge has a top plate that is commonly connected to the top of a plurality of cylinders and is arranged parallel to the substrate. A plurality of cylinders are arranged apart from each other.

In the above-mentioned maybe force meter, a plurality of cylinders are arranged. In addition, the cylinders are arranged apart from each other. As a result, the flexural rigidity can be increased without increasing the cross-sectional shape of each cylinder. In other words, the strain detection sensitivity with respect to the compressive force can be improved while maintaining the flexural rigidity. It is possible to realize a maybe force meter having resistance to a large bending moment without lowering the sensitivity of detecting strain with respect to compressive force.

The central axes of a plurality of cylinders may be arranged at point-symmetrical positions with respect to the center point of the substrate when the substrate is viewed from above vertically. Details of the effect will be described in Examples.

The central axes of a plurality of cylinders may be located on the circumference centered on the center point of the substrate when the substrate is viewed from above vertically. Details of the effect will be described in Examples.

The central axes of a plurality of cylinders may be located on the sides of a quadrangle centered on the center point of the substrate when the substrate is viewed from above vertically. Details of the effect will be described in Examples.

The vertical projection position of the strain gauge on the substrate is at least one of the two intersections where the line passing through the center point of the substrate and the center point of the cylinder when the substrate is viewed from above vertically intersects the cylinder. It may be the corresponding position.

The vertical projection position of the strain gauge on the substrate may be a position corresponding to the intersection of the two intersections farther from the center point of the substrate. Details of the effect will be described in Examples.

Perhaps the force gauge may include a bridge circuit. The bridge circuit may be formed by a combination of a plurality of strain gauges arranged in a plurality of cylinders located symmetrically with respect to the center point of the substrate when the substrate is viewed from above vertically. The bridge circuit may be formed by a combination of a plurality of strain gauges arranged symmetrically with respect to the center point of the substrate.

The diameters of the plurality of cylinders may be the same.

It is a schematic perspective view of the maybe force meter 1 which concerns on Example 1. FIG. It is a cross-sectional top view of the line II-II of FIG. It is sectional drawing side view in line III-III of FIG. This is an example of a bridge circuit. This is an example of a bridge circuit. This is an example of a bridge circuit. It is sectional drawing top view of the maybe force meter 100 which concerns on a comparative example. This is a trial calculation example of geometric dimensions, axial strain, and bending strain. It is sectional drawing top view of the maybe force meter 1a which concerns on Example 2. FIG. It is sectional drawing top view of the multi-component force meter 1b which concerns on Example 3. FIG. It is sectional drawing top view of the maybe force meter 1c which concerns on Example 3. FIG.

(Maybe the configuration of force meter 1)
FIG. 1 shows a schematic perspective view of the maybe force meter 1 according to the first embodiment. FIG. 2 shows a top view of a cross section taken along line II-II of FIG. FIG. 3 shows a cross-sectional side view taken along the line III-III of FIG. In FIGS. 1 to 3, the wiring and the like connected to the strain sensor are not shown. As shown in FIG. 1, the force meter 1 is an instrument capable of measuring the forces Fx, Fy, Fz in the X, Y, Z axis directions and the moments Mx, My, Mz around the X, Y, Z axes. is there. The force meter 1 includes a substrate 10, cylinders 21 to 24, an upper plate 30, strain gauges 41a to 41d, 42a to 42d, 43a to 43d, and 44a to 44d. The substrate 10 and the upper plate 30 are steel plates formed in a thick flat plate shape. In this example, the thickness was 50 mm. The substrate 10 and the upper plate 30 are square when viewed from above (+ Z direction) vertically. The substrate 10 and the upper plate 30 are arranged parallel to each other with the cylinders 21 to 24 interposed therebetween. As shown in FIG. 2, the center when the substrate 10 is viewed from above vertically is defined as the substrate center point BP. The substrate center point BP coincides with the intersection of the diagonal lines of the substrate 10.

The cylinders 21 to 24 are arranged on the substrate 10. The cylinders 21 to 24 are made of steel. As shown in FIG. 2, the cylinders 21 to 24 are arranged apart from each other. The cylinders 21 to 24 have the same radius R, plate thickness t, and height H. The diameter-thickness ratio (ratio of plate thickness to diameter) of cylinders 21 to 24 is determined at 2 R / t. The diameter-thickness ratio is preferably increased so that buckling does not occur due to the assumed maximum load. The central axes CA1 to CA4 of the cylinders 21 to 24 are arranged at positions symmetrical with respect to the substrate center point BP. Specifically, the central axes CA1 and CA3 are point-symmetrical, and the central axes CA2 and CA4 are point-symmetrical. As shown in FIG. 3, the central axes CA1 to CA4 are perpendicular to the surface of the substrate 10.

A flange portion 21a is formed at the lower end of the cylinder 21, and a flange portion 21b is formed at the upper end. The flange portion 21a is fixed to the substrate 10 by bolts 51a. The flange portion 21b is fixed to the upper plate 30 by bolts 51b. Since the cylinders 22 to 24 have the same structure as the cylinder 21, the description thereof will be omitted. As a result, a structure is realized in which the cylinders 21 to 24 are rigidly connected by sufficiently rigid upper and lower steel plates. Therefore, the strain generated in the cylinders 21 to 24 can fully satisfy the assumption of cross-section retention.

Strain gauges 41a to 41d are attached to the cylinder 21. Specifically, as shown in FIGS. 2 and 3, strain gauges 41a to 41d are attached to the inner wall of the cylinder 21 in the region where the flange portions 21a and 21b are not formed. The strain gauges 41a to 41d are arranged so that the arrangement directions with respect to the central axis CA1 are every 90 degrees in the top view (FIG. 2). That is, the strain gauges 41a to 41d are arranged in the positive and negative directions of the X-axis and the positive and negative directions of the Y-axis with respect to the central axis CA1. The strain gauges 41a to 41d are 3-axis gauges. That is, one gauge can measure the strains of the vertical component, the 45 ° component, and the 135 ° component. The vertical component is a component in the Z-axis direction. The 45 ° direction component is a component in a direction inclined by 45 ° with respect to the positive direction of the Z axis. The 135 ° direction component is a component in a direction inclined by 135 ° with respect to the positive direction of the Z axis. As the strain gauges 41a to 41d, a metal foil strain gauge or a metal wire strain gauge can be used.

Strain gauges 42a to 42d are attached to the cylinder 22 in the same manner. Strain gauges 43a to 43d are attached to the cylinder 23. Strain gauges 44a to 44d are attached to the cylinder 24. Since the arrangement positions of these strain gauges are the same as those of the strain gauges 41a to 41d of the cylinder 21, the description thereof will be omitted. As a result, a total of 16 strain gauges are attached. Since three strain measurement values (vertical component, 45 ° direction component, 135 ° direction component) are output from each gauge, a maximum of 48 strain measurement values can be obtained.

(Bridge circuit)
A plurality of strain gauges are combined to form a bridge circuit. At this time, strain gauges arranged on a plurality of cylinders located symmetrically with respect to the substrate center point BP are combined. Further, strain gauges arranged at positions symmetrical with respect to the substrate center point BP are combined.

A specific example will be described. FIG. 4 is an example of a bridge circuit for obtaining the average axial strain of the cylinders 21 and 23. As shown in FIG. 4, eight vertical components 41a [v] to 41d [v] of the strain gauges 41a to 41d and eight vertical components 43a [v] to 43d [v] of the strain gauges 43a to 43d. One bridge circuit is composed of directional components. The strain gauges 41a to 41d and 43a to 43d constituting the bridge circuit of FIG. 4 are gauges arranged on cylinders 21 and 23 located symmetrically with respect to the substrate center point BP. Further, the strain gauges 41a to 41d and 43a to 43d are gauges arranged at positions symmetrical with respect to the substrate center point BP.

FIG. 5 is an example of a bridge circuit for obtaining bending strain (curvature × distance between gauges) around the X axis. As shown in FIG. 5, one bridge circuit is composed of four vertical components of strain gauges 41d, 42d, 43b, and 44b. The strain gauges 41d, 42d, 43b, and 44b constituting the bridge circuit of FIG. 5 are gauges arranged in each of the cylinders 21 to 24 located symmetrically with respect to the substrate center point BP. Further, the strain gauges 41d and 43b and the strain gauges 42d and 44b are gauges arranged at positions symmetrical with respect to the substrate center point BP.

FIG. 6 is an example of a bridge circuit for obtaining shear strain in the X direction. As shown in FIG. 6, four 45 ° direction components 41b [d1] to 44b [d1] of strain gauges 41b to 44b and four 135 ° direction components 41b [d2] to 44b [d2] of strain gauges 41b to 44b. , Four 45 ° direction components 41d [d1] to 44d [d1] of strain gauges 41d to 44d, and four 135 ° direction components 41d [d2] to 44d [d2] of strain gauges 41d to 44d, for a total of 16 components. One bridge circuit is configured. The strain gauges 41b to 44b and 41d to 44d constituting the bridge circuit of FIG. 6 are gauges arranged in each of the cylinders 21 to 24 located symmetrically with respect to the substrate center point BP. Further, the strain gauges 41b and 43d, 42b and 44d, 42d and 44b, 41d and 43b are gauges arranged at positions symmetrical with respect to the substrate center point BP.

(Calculation result)
The geometric dimensions when the multi-component force meter 1 (FIG. 2) of this example and the multi-component force meter 100 (FIG. 7) of the comparative example are used for a portion where a large bending moment is applied are estimated. As an example, it is assumed that a force gauge is placed at the top of the pier of the continuous viaduct. As an equivalent to the actual size, the acting force was set to a vertical force N = 11MN and a bending moment M = 74MN · m. The cross-sectional top view (FIG. 7) of the multi-component force meter 100 of the comparative example is a drawing corresponding to the cross-sectional top view (FIG. 2) of the multi-component force meter 1 of this embodiment. The multi-component force meter 100 of the comparative example is different from the multi-component force meter 1 of the present embodiment only in that it includes one cylinder 121, and has the same other structure. The central axis of the cylinder 121 coincides with the substrate center point BP. The diameter-thickness ratio of the cylinders 21 to 24 = 2R / t (FIG. 2) and the diameter-thickness ratio of the cylinder 121 = 2R _c / t _c are both assumed to be the same value of “8”. Further, in the maybe force meter 1 (FIG. 2) of this embodiment, when the distance between the center of gravity CT and the central axes CA1 to CA4 is L, the distance L is twice the radius R. Perhaps the materials of the force meters 1 and 100 were carbon steel for machine structure (S45CN), and the allowable stress σ _a was 210 MPa.

The radius, plate thickness, axial strain ε _N , and bending strain ε _M of the cylinder obtained under these conditions are shown in the table of FIG. It can be seen that the radius R of the multi-component force meter 1 of this embodiment can be reduced to half or less as compared with the multi-component force meter 100 of the comparative example. Further, in the maybe force meter 1 of this embodiment, the bending strain ε _M can be reduced (that is, the bending rigidity is increased) and the axial strain ε _N is increased (that is, the detection sensitivity of the compressive force is increased). You can see that you can.

ここで、下式（２）、（３）の感度に関する条件を満たすよう、断面積Ａ（すなわち半径Ｒと板厚ｔ）を定める。式（２）は、作用軸力Ｎによって生じる直ひずみが、所要の直ひずみの感度ε_０以上となる条件である。式（３）は、作用せん断力Ｓによって生じるせん断ひずみが、所要のせん断ひずみの感度γ_０以上となる条件である。

ここでＥは円筒２１〜２４のヤング率であり、Ｇは円筒２１〜２４のせん断弾性係数である。 (Relationship between distance L and radius R)
The formula for determining the relationship between the distance L and the radius R shown in FIG. 2 will be described below. In FIG. 2, the cross-sectional area A of the cylinders 21 to 24 is obtained by the following formula (1).

Here, the cross-sectional area A (that is, the radius R and the plate thickness t) is determined so as to satisfy the conditions relating to the sensitivities of the following equations (2) and (3). Equation (2) is a condition under which the direct strain generated by the acting axial force N has a required direct strain sensitivity of ε ₀ or more. Equation (3) is a condition in which the shear strain generated by the acting shear force S has a required shear strain sensitivity of γ ₀ or more.

Here, E is the Young's modulus of the cylinders 21 to 24, and G is the shear modulus of the cylinders 21 to 24.

Next, the distance L can be determined so that the cylinders 21 to 24 having the radius R and the plate thickness t determined by the above equation have an allowable stress σ _a or less with respect to the acting axial force N and the acting bending moment M. it can. Specifically, the distance L can be approximately obtained by using the following equations (4) and (5).

(effect)
When a force gauge is used in a part where a relatively large bending moment is applied (eg, the top of a rigidly connected pier), it is necessary to increase the allowable moment by increasing the bending rigidity. In the comparative force meter 100 (FIG. 7) including one cylinder, it is necessary to increase the cross-sectional shape in order to increase the bending rigidity. However, when the cross-sectional shape is increased, the compressive rigidity is also increased proportionally, so that the strain detection sensitivity with respect to the compressive force is lowered. In the maybe force meter 1 of this embodiment, a plurality of cylinders 21 to 24 are arranged. Further, the cylinders 21 to 24 are arranged apart from each other. As a result, the flexural rigidity can be increased without increasing the cross-sectional shape of the cylinders 21 to 24. In other words, the strain detection sensitivity with respect to the compressive force can be improved while maintaining the flexural rigidity. It is possible to realize a maybe force meter having resistance to a large bending moment without lowering the sensitivity of detecting strain with respect to compressive force.

Since the force meter 1 is provided with 16 triaxial strain gauges, a maximum of 48 strain measurement values can be obtained. However, the number of channels of the data logger is limited, and it is difficult to allocate as many as 48 channels. The multi-component force meter 1 of this embodiment is characterized in that the central axes CA1 to CA4 of the cylinders 21 to 24 are arranged at point-symmetrical positions with respect to the substrate center point BP. Utilizing this symmetry, a bridge circuit is constructed using strain gauges arranged symmetrically with respect to the substrate center point BP, so that the sum and difference of the resistance values of the strain gauges can be calculated in an analog manner. Can be done. Since it is sufficient to provide one data logger channel for one bridge circuit, it is possible to reduce the number of channels used.

Since the cylinders 21 to 24 are required to have high processing accuracy and no internal cracks, they are generally formed by machining. In the machining of a cylinder, the cross-sectional area increases in proportion to the square of the radius of the cylinder. Therefore, as the radius increases, the material cost and the processing cost increase exponentially. In the multi-component force meter 1 of the present embodiment, the radius R of the cylinder can be reduced to half or less while maintaining the flexural rigidity as compared with the multi-component force meter 100 (FIG. 7) of the comparative example. This makes it possible to reduce the material cost and processing cost of the cylinder.

FIG. 9 shows a top view of a cross section of the multi-component force meter 1a according to the second embodiment. The cross-sectional top view of the multi-component force meter 1a of the second embodiment is a drawing corresponding to the cross-sectional top view (FIG. 2) of the multi-component force meter 1 of the present embodiment. The multi-component force meter 1a of the second embodiment is different from the multi-component force meter 1 of the first embodiment only in the number of strain gauges and the attachment position. The description will be omitted by assigning a common reference numeral to the portion common to the multi-component force meter 1a of the second embodiment and the multi-component force meter 1 of the first embodiment.

Strain gauges 141 to 144 are attached to each of the cylinders 21 to 24. The vertical projection positions of the strain gauges 141 to 144 on the substrate 10 are four diagonal positions centered on the substrate center point BP. Specifically, the vertical projection position of the strain gauge 141 is far from the substrate center point BP of the two intersections IP1a and IP1b where the line passing through the substrate center point BP and the cylinder center axis CA1 intersects the cylinder 21. This is the position corresponding to the intersection IP1a. Similarly, the vertical projection positions of the strain gauges 142 to 144 are positions corresponding to the intersections IP2a to IP4a farther from the substrate center point BP.

(effect)
The strain gauges 141 to 144 are arranged at diagonal positions about the substrate center point BP. Since this arrangement position is the position farthest from the substrate center point BP, the strain sensitivity is high. This is because the bending strain is proportional to the distance from the substrate center point BP. By selectively attaching the strain gauge to such a position with high strain sensitivity, the number of sheets to be attached can be increased while maintaining the strain measurement accuracy as compared with the attachment mode (FIG. 2) of the strain gauge of Example 1. It can be reduced. It is possible to reduce the number of channels used by the data logger.

The strain gauges 141 and 144 can be arranged symmetrically with respect to the X-axis, and the strain gauges 142 and 143 can be arranged symmetrically. Further, the strain gauges 141 and 142 can be arranged symmetrically with respect to the Y axis, and the strain gauges 143 and 144 can be arranged symmetrically. That is, the arrangement positions of the strain gauges 141 to 144 can be set to positions symmetrical with respect to the X-axis and the Y-axis. Thereby, the anisotropy of the measured strain value can be eliminated.

Top views of the cross sections of the multi-component force meters 1b and 1c according to the third embodiment are shown in FIGS. 10 and 11. The cross-sectional top view of the multi-component force meter 1b and 1c of the third embodiment is a drawing corresponding to the cross-sectional top view (FIG. 2) of the multi-component force meter 1 of the present embodiment. The multi-component force meters 1b and 1c of the third embodiment differ only in the number and arrangement positions of the cylinders from the multi-component force meter 1 of the first embodiment. The description will be omitted by assigning a common reference numeral to the parts common to the multi-component force meters 1b and 1c of the third embodiment and the multi-component force meter 1 of the first embodiment.

In the maybe force meter 1b of FIG. 10, cylinders 221 to 228 are arranged. The central axes CA11 to CA18 of the cylinders 221 to 228 are located on the circumferential CR centered on the substrate center point BP. In the multi-component force meter 1b of FIG. 10, the distance from the substrate center point BP to the central axes CA11 to CA18 can be increased as compared with the multi-component force meter 1 (FIG. 2) of the first embodiment. It is possible to increase the sensitivity of the bending moment. Further, since the cylinders 221 to 228 are arranged on the circumferential CR, the anisotropy of the strain measurement value can be eliminated.

In the maybe force meter 1c of FIG. 11, cylinders 321 to 322 are arranged. Specifically, the central axes CA21 to CA32 of the cylinders 321 to 32 are located on the sides of the quadrangle SQ centered on the substrate center point BP. Here, as an example of the "quadrangle centered on the substrate center point BP", there is a quadrangle in which the intersection of the diagonal lines coincides with the substrate center point BP. In the multi-component force meter 1c of FIG. 11, the distance from the substrate center point BP to the central axes CA21 to CA32 can be increased as compared with the multi-component force meter 1 (FIG. 2) of the first embodiment, so that the bending moment can be increased. It is possible to increase the sensitivity. Further, by arranging the cylinder on the quadrangle SQ, the degree of freedom in the layout of the force meter 1c can be increased with respect to the structure composed of straight lines.

Although specific examples of the present invention have been described in detail above, these are merely examples and do not limit the scope of claims. The techniques described in the claims include various modifications and modifications of the specific examples illustrated above. The technical elements described herein or in the drawings exhibit their technical usefulness alone or in various combinations, and are not limited to the combinations described in the claims at the time of filing. In addition, the techniques illustrated in the present specification or drawings can achieve a plurality of purposes at the same time, and achieving one of the purposes itself has technical usefulness.

(Modification example)
The position where the strain gauge is attached to the cylinder is not limited to the inner wall, but may be the outer wall.

The bridge circuits of FIGS. 4 to 6 are examples. Any bridge circuit having any configuration can be used as long as it is a bridge circuit having the symmetry described in the present specification.

The maybe force meters described in the present specification are not limited to the mode used alone, and a plurality of them may be used side by side.

In this embodiment, the case where a plurality of cylinders are arranged point-symmetrically with respect to the substrate center point BP has been described, but the present invention is not limited to this embodiment. For example, the arrangement direction from the substrate center point BP may be three points every 120 °, and the three cylinders may be arranged at three points having the same distance from the substrate center point BP.

The plurality of cylinders are not all limited to the same diameter. They may have different diameters as long as they have the symmetry described herein.

The material of the force meter is not limited to steel, and can be appropriately selected from the viewpoint of strength and strain. For example, it may be stainless steel, an aluminum alloy, or the like.

1: Probability meter 10: Substrate 21 to 24: Cylinder 30: Top plate 41a to 44d: Strain gauge CA1 to CA4: Central axis

Claims (8)

With the board
A plurality of cylinders arranged on the substrate, the plurality of cylinders whose central axis is perpendicular to the surface of the substrate, and the plurality of cylinders.
Strain gauges arranged in each of the plurality of cylinders and
An upper plate that is commonly connected to the upper part of the plurality of cylinders and is arranged in parallel with the substrate,
With
The plurality of cylinders are arranged apart from each other, perhaps a force meter. The maybe force meter according to claim 1, wherein the central axes of the plurality of cylinders are arranged at point-symmetrical positions with respect to the center point of the substrate when the substrate is viewed from above vertically. The maybe force meter according to claim 1 or 2, wherein the central axes of the plurality of cylinders are located on a circumference centered on a center point of the substrate when the substrate is viewed from above vertically. The maybe force meter according to claim 1 or 2, wherein the central axes of the plurality of cylinders are located on the sides of a quadrangle centered on the center point of the substrate when the substrate is viewed from above vertically. The vertical projection position of the strain gauge on the substrate is one of two intersections where the line passing through the center point of the substrate and the center point of the cylinder when the substrate is viewed from above vertically intersects the cylinder. The maybe dynamometer according to any one of claims 1 to 4, which is a position corresponding to at least one intersection. The maybe force meter according to claim 5, wherein the vertical projection position of the strain gauge on the substrate is a position corresponding to the intersection of the two intersections farther from the center point of the substrate. It is a combination of a plurality of strain gauges arranged in a plurality of cylinders located symmetrically with respect to the center point of the substrate when the substrate is viewed from above vertically.
The maybe force meter according to any one of claims 1 to 6, further comprising a bridge circuit formed by a combination of a plurality of strain gauges arranged symmetrically with respect to the center point of the substrate. The maybe force meter according to any one of claims 1 to 7, wherein the plurality of cylinders have the same diameter.

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