JP6202673B2 - load cell - Google Patents

Description

  The present invention relates to a load meter that receives a load on two parallel pressure-receiving surfaces of a plate and measures a displacement between both pressure-receiving surfaces due to the load, and the plate.

  For example, in the ground anchor method for stabilizing the slope and supporting the structure stably, the tension is applied to the tension material such as a PC strand with one end fixed to the underground anchor body, and the slope is formed on the other end side. Stabilizing plates and structures are fixed. At this time, a load meter is installed on the other end-side fixing portion for measurement of tension fluctuation during construction of the tendon and long-term tension monitoring after construction (see Patent Document 1, paragraph 0031, FIG. 8). . A load meter for measuring tension is also installed on the cable of the suspended structure. As the load cell, a capacitive load cell has been studied.

As an example of the capacitance type load cell, a circular hole is formed between two parallel pressure receiving surfaces of an annular plate that receives a load (hereinafter, “between both pressure receiving surfaces” is appropriately referred to as “upper and lower”). In some cases, a pair of electrodes are provided facing each other on the inner peripheral surface of the circular hole. When this load cell receives a load on both pressure receiving surfaces of the plate, it detects a change in capacitance due to a change in the distance between the electrodes due to a displacement (thickness deformation) between the upper and lower sides of the plate due to the load. Then, the load is measured based on the detected value (see Patent Document 1, paragraph 0009, FIG. 9). That is, this load meter measures the load on the pressure receiving surface of the plate by the vertical displacement of the plate circular hole.

JP 2009-53095 A

In such a load meter plate, with reference to FIG. 5, when a load P is applied to the upper and lower pressure receiving surfaces 1 and 2, the columnar circular hole h is reduced in the vertical direction (Z direction), The front-rear direction (X direction) and the left-right direction (Y direction) are enlarged.
At this time, while the axis c ₁ direction of the circular hole h, the inner peripheral side of the peripheral wall (in) and the outer (out) one surface (front and rear surfaces In FIG. 5) is opened, The middle part (mid) has high rigidity because both sides are complete. For this reason, in the displacement (deformation) in the Y direction, the inner peripheral side, the outer peripheral side, and the central portion have large variations. This variation and thus deteriorating the accuracy when measuring the load on the plate displacement (deformation) degree over the axis c ₁ substantially the entire length in the circular hole h circumference. In particular, capacitance type leads to a decrease in the measurement accuracy because measuring the load with a capacitance change of the axis c ₁ substantially the entire length in the circular hole h circumference.

Further, when the plate is annular, the thickness in the Y direction is gradually increased from the inner side to the outer side (outward in the X direction) (the rigidity is increased). The displacement on the inner peripheral side, the central part and the outer peripheral side in the direction is not uniform (variation).
Since these displacements in the Y direction affect the displacement in the Z direction (because the constraint in the Y direction also affects the rigidity in the Z direction), measurement of the displacement in the Z direction, that is, the displacement in the vertical direction of the center of the plate circular hole This also causes a decrease in the accuracy of the load measurement on the pressure receiving surfaces 1 and 2 due to the measurement.

  This invention makes it a subject to improve the precision of the load meter which measures the said load P by the deformation | transformation of the through-hole formed between two parallel pressure-receiving surfaces which receive a load under the above actual condition.

In order to achieve the above object, the present invention includes a plate having two parallel pressure receiving surfaces that receive a load, and a through hole formed in the plate and having a circular cross section or a regular polygonal cross section in the direction of the orthogonal axis of the pressure receiving surface. A configuration of the plate of a load cell provided in the through-hole and having a displacement gauge measuring element for measuring the displacement of the through-hole, in which slits are formed around the through-hole, is adopted.

  Since the present invention is configured as described above, and the load is detected by the displacement (deflection) of the through hole side portion of the plate separated by the slit, the load appears as the displacement of the through hole side portion, The load can be measured appropriately.

It is a partially divided partial perspective view of one embodiment of a capacitance type load cell which is one of the load cells according to the present invention. It is a partial front view of the embodiment. It is a relationship figure of load and amount of deformation, (a) is a relation figure of Z direction, and (b) is a relation figure of Y direction. It is a general | schematic partial front view of each other Example. It is action | operation explanatory drawing of a load.

A load cell according to an embodiment of the present invention includes a plate having two pressure receiving surfaces in parallel to receive a load, and a through-hole formed in the plate and having a circular cross section or a regular polygonal cross section in the orthogonal axis direction of the pressure receiving surface, In a configuration having a displacement meter provided in the through hole and measuring the displacement of the through hole, a slit is formed along the periphery of the through hole.
If comprised in this way, a part of plate wall around a through-hole (the through-hole side part of the plate cut | disconnected by the said slit) will be connected with the other part of the plate up and down, and the other part will cut off by the slit. It becomes a pipe shape. When receiving a force from above and below its cross section (when receiving a load P), the pipe bends evenly and easily over its entire length in the axial direction and the entire circumference. For this reason, if the load is measured by the displacement of the pipe portion, the measurement accuracy becomes high.
If a pipe-like wall is formed, the above-mentioned effects are exhibited. Therefore, if a pipe is inserted into the through hole and the upper and lower sides of the pipe are fixed to the inner surface of the through hole by welding or the like, the pipe and the inner surface of the through hole are provided. A slit is formed between the two. For this reason, this invention includes the case where such a pipe is inserted and fixed.

  Conventionally, when the displacement between the pressures received by the plate due to the load is in units of microns or nanometers, it is difficult to measure the displacement due to the load because the displacement (deflection) due to the temperature change is larger than the displacement due to the load. However, as described above, if the measurement accuracy is high by measuring the load with the displacement of the pipe portion, the displacement due to the temperature change can be predicted by the pipe shape and the displacement due to the load also increases. Therefore, the displacement due to the load can be accurately measured in consideration of the predicted displacement due to the temperature change. In other words, the conventional characteristic is “temperature sensitivity (displacement due to temperature change)”> “displacement due to load”, whereas “temperature sensitivity” <“displacement due to load” can be obtained. Furthermore, since the displacement characteristics are uniform (uniform) on the inner circumferential side, the central portion, and the outer circumferential side of the through hole in the axial center direction, the stability of the output (measured value) due to repeated loads is also increased.

  As long as the said plate has a pressure receiving surface up and down, the planar view shape is arbitrary, but circular members, such as a circle, are preferable. This is because the load on both pressure receiving surfaces can be evenly received around the axis if the shape is circular.

  The through hole having a regular polygonal cross section preferably has an axis of symmetry that is perpendicular to the pressure receiving surface. This is because the displacement is symmetrical between the left and right sides of the through hole, and the displacement of the entire through hole is uniform. In this respect, the through hole is most preferably circular in cross section. The number of the through holes and the circumferential distance of the plate may be appropriately determined in consideration of the displacement (deflection) characteristics of the plate, but in the plan view of the plate, it is symmetrical left and right and up and down with respect to the axis. It is preferable that they are positioned so that the distance between them is equal.

The pipe-like portion facilitates the displacement of the through-holes by not only the left and right sides of the through-holes. For this reason, the slit may be only one of the left and right sides of the through-hole, but if it is formed symmetrically with respect to the axial center of the through-hole (formed on the left and right), the pipe-shaped part is formed on almost the entire circumference of the through-hole. Therefore, the displacement of the through hole becomes smoother. At this time, it is preferable that the slit is vertically symmetric with respect to the axial center of the through hole. This is because the pipe-shaped portion approaches the pipe shape that is connected to the entire circumference, and the upper, lower, left, and right sides become symmetrical pipe shapes, and the displacement in the thickness direction around the pipe portions becomes uniform.
Moreover, it is preferable that the said slit becomes the same width along the circumference | surroundings of the said through-hole. This is because when the slit width is uniform, there is little change in the shape of the other part of the plate with respect to the plate wall around the through hole, and unevenness in the displacement (deflection) between the pressure receiving surfaces of the plate hardly occurs. In addition, compared with the case where a width | variety is varied, formation with a drill and a wire is easier for the same width (refer FIG. 2, FIG. 4).

  Furthermore, the surface (inner side surface) along the circumference of the through hole of the slit has the same interval with respect to the inner peripheral surface of the through hole over the entire length, and the pipe-shaped portion has the same thickness over the entire length. It is preferable that This is because the displacement of the pipe-like portion due to the load becomes uniform over the entire length, and the load detection accuracy is improved by the uniformization.

  In addition, since the capacitance type load cell is detected by a non-contact sensor (measuring element), it is characterized in that the sensor part having a fear of failure can be replaced while the plate receives a compressive force. For this reason, if the deformation of the through hole is uniform over the entire circumference, the variation in the hole deformation due to the processing accuracy of the through hole and the non-uniformity of the material is suppressed, and the sensor having a fear of failure is removed. In addition, a sensor calibrated with another through hole can be installed with good reproducibility.

The plate of each configuration can be a load meter that measures the load on both pressure receiving surfaces by incorporating various measuring elements of displacement gauges of the holes into the through holes.
As the displacement meter, a conventionally known one may be employed, and for example, an electric resistance strain sensor, a laser displacement sensor, a capacitance sensor, or the like can be used. In the case of the capacitance sensor, for example, it is composed of one electrode provided on the inner peripheral surface of the through hole and another electrode having a gap in the electrode, and the capacitance change between both electrodes A configuration for measuring the displacement between both pressure receiving surfaces is adopted.

1 and 2 show an embodiment of a capacitive load meter according to the present invention, and this capacitive load meter G is installed at the other end side fixing portion of the tension material in the ground anchor method. .
The load meter G includes a substantially annular plate 10 made of stainless steel (for example, SUS630) and a capacitance detection probe (measuring element) 20 incorporated in the plate 10.

The inner and outer diameters and thicknesses of the plate 10 may be set as appropriate according to the object to be measured. For example, the outer diameter is 128 mm, the inner diameter is 65 mm, and the thickness is 38 mm. Further, the periphery of the plate 10, 60 degrees equally spaced in diameter: 20mm circular hole 13 is formed in each circular hole 13 opening on its inner peripheral surface is the axis c ₁ is the radial direction of the plate 10 doing. The circular holes 13 weaken the rigidity in the thickness direction of the plate 10 and are easily deformed (bent) in the thickness direction by the load on the pressure receiving surfaces 11 and 12. The number and diameter of the circular holes 13 may be appropriately determined in consideration of the deformation characteristics.

The capacitance detection probes 20 can be provided in all the circular holes 13, but are preferably provided symmetrically in FIG. In this embodiment, four probes 20 are provided symmetrically.

Around each circular hole 13, a slit 14 which is a feature of the present invention is formed. This slit 14 is necessarily formed in the circular hole 13 into which the probe 20 is incorporated. That is, it is not necessary to provide the slit 14 in the circular hole 13 in which the probe 20 is not incorporated.
The slit 14 has an arc shape concentric with the circular hole 13 and opens on the inner and outer peripheral surfaces of the plate 10 (see FIG. 1). The inner peripheral surface is located on the circumference of a diameter of 25 mm, and its radial direction. Width t: 0.3 mm. Further, the central angle θ of the arc-shaped portion 16b is 120 degrees. The width t is arbitrary as long as the following pipe-shaped portion 16b can be formed, but is appropriately set in consideration of the displacement (deflection) characteristics of the pipe-shaped portion 16b.
For example, the slit 14 is formed with a hole 15 having a diameter of 3 mm at both ends and a space between the holes 15 and 15 is formed by wire cutting, but may be formed by other means such as a drill.

When the slit 14 is formed around the circular hole 13 along the inner periphery in this way, the plate wall around the circular hole 13 is connected to the other portion 16a of the plate 10 in the vertical direction by the slit 14, and the other is The separated arc-shaped portion 16b becomes a pipe shape. The pipe-shaped portion 16b receives a force from above and below (when under load), readily flex in the vertical direction uniformly and easily with bent along its axis c ₁ direction length. For this reason, when measuring the load with the displacement of the pipe-like portion 16b, the amount of displacement due to the compressive force is larger than that without the slit 14, and the sensitivity is improved.

  In the plate 10 in which such slits 14 are formed, a load is applied to the upper and lower pressure receiving surfaces 11, 12, and the inner peripheral side (in), the central part (mid), and the outer peripheral side (out) of the circular hole 13. ) Between the top and bottom (Z direction) and between the left and right (Y direction) was determined by stress analysis. The relationship between the load (horizontal axis: kN) and the amount of deformation (vertical axis: nm) is shown in FIG. Further, the same analysis is performed for the plate 10 in which the slit 14 is not formed, and the result is shown in FIG. 3, in which (a) is a Z direction and (b) is a relationship diagram in the Y direction. It is.

  From this analysis result, if the slit 14 is formed, the difference in displacement amount between the inner peripheral side, the central portion, and the outer peripheral side of the pipe-shaped portion 16b is reduced and the displacement amount in the Z direction is increased, while the displacement in the Y direction is increased. You can see that the amount is getting smaller. From this, it can be understood that if the slit 14 is formed, the pipe-like portion 16b is easily deformed and the sensitivity and accuracy with respect to the load P are improved.

  Based on the above test results, a capacitance type load meter G is obtained by providing a capacitance detection probe 20 in the circular hole 13 as shown in FIG. The probe 20 may be the one described in Patent Document 1, but can be the one shown in FIG. The probe 20 has one electrode made of a metal such as silver paste formed on the surface of a cylindrical body 21 made of the same material as the plate 10 with an insulating layer interposed therebetween, and a sealing material such as an O-ring 24 is fitted to both ends thereof. Further, nitrogen gas or the like is sealed between the sealing materials to prevent rust, and the mounting piece 25 is fixed to the rear end. If the plate 10 and the cylindrical body 21 are made of the same material, measurement errors due to temperature changes can be minimized.

The mounting piece 25 is fixed to the plate 10 by passing a screw 26 through its upper end and screwing the screw 26 into the screw hole 26a, and the hole 27 at the lower end of the mounting piece 25 is vertically and horizontally moved to the pin 28 of the plate 10. It fits so that it can move (it fits pin 28 in fool hole 27). At this time, the axial centers of the circular hole 13 and the cylindrical body 21 are matched. In this attachment mode, even when the plate 10 receives the load P in the vertical direction, the probe 20 hardly receives the load. Therefore, the probe 20 can be replaced even in a loaded state by loosening the screw 26.
In addition, the attachment aspect of this probe 20 can be employ | adopted also in the attachment aspect of patent document 1, etc. which do not provide the slit 14, For example, the probe may be other than an electrostatic capacitance type.

Another electrode is formed on the inner surface of the circular hole 13 so as to face the one electrode formed on the probe 20 as in the prior art. The other electrode may be formed by polishing the inner surface of the circular hole 13, but may be formed by applying a metal paste in the same manner as the electrode formed on the probe 20.
As described above, when the pair of electrodes facing the inner surface of the pipe-shaped portion 16b and the outer surface of the probe 20 are positioned, when a load is applied to the pressure receiving surfaces 11 and 12 of the plate 10, the pipe-shaped portion 16b on the outer periphery of the circular hole 13 is Deformation (displacement) in the vertical and horizontal directions changes the capacitance between the electrodes. In the same way as in the prior art, the change is electrically led to a detector composed of an external IC or the like via a lead wire 29 or the like, and the capacitance change measurement value is applied to the plate 10 measured in advance. Measurement (calculation) is performed by comparison with a database indicating the relationship between the load and the deformation amount of the capacitance.

In this embodiment, the length (angle θ), the same width t, etc. of the slit 14 are appropriately determined by experiments or the like. The shape of the slit 14 is arbitrary as long as the effects of the present invention can be exhibited. For example, the slit 14 may be a straight line in the vertical direction instead of an arc shape (see FIG. 4C). It may be vertically symmetric with respect to c ₁ (see (a) to (d) in the same figure), or its width may change (see (a) and (b) in the same figure). Further, only one of the left and right slits 14 is used (see (d) in the figure), the left and right are symmetrical and the top and bottom are asymmetric (see (e) in the same figure), the top and bottom are symmetrical and the left and right are asymmetric can do. Further, the gap between the inner peripheral surface of the circular hole 13 and the inner peripheral surface of the slit 14 may be different in the vertical direction (see FIGS. 2B and 2C).
In either embodiment, the electrode of the probe 20 is opposed to the pipe-shaped portion 16b.

Although the said Example was installed in the other end side fixing | fixed part of the tension material in a grand anchor construction method, the load meter of this invention can be employ | adopted as a place which measures the load in another various aspect. Of course.
Further, according to the present invention, in a plate having a pressure receiving surface, a load on the pressure receiving surface can be regarded as a displacement of the pipe-like portion 16b formed in the plate, and the load can be measured by measuring the displacement. As long as the displacement meter can capture the displacement of the pipe-like portion 16b, other displacement meters such as an electric resistance strain sensor, a laser displacement sensor, and the like can be employed without being limited to the capacitive sensor.

  Thus, it should be thought that embodiment disclosed this time is an illustration and restrictive at no points. The scope of the present invention is defined by the terms of the claims, and is intended to include any modifications within the scope and meaning equivalent to the terms of the claims.

DESCRIPTION OF SYMBOLS 10 Plate 11, 12 Pressure-receiving surface 13 Circular hole 14 Slit 15 Hole 16a Connection part 16b Pipe-shaped part 20 Capacitance detection probe 21 Capacitance detection probe cylinder 24 O-ring 25 fitted to a cylinder body Cylinder attachment piece 26 Probe mounting screw 26a Screw hole 27 Hole 28 Pin

Claims (7)

An annular plate having two parallel pressure receiving surface for receiving the load in the vertical direction up and down,
Cross-sectional circular or regular polygonal through- holes that penetrate the annular plate in the radial direction ;
Provided in said through hole, and the one electrode of the inner peripheral surface of the through hole, the electrostatic capacitance detection for detecting a change in capacitance between the other electrode facing at a gap on one of the electrodes thereof A load meter having a probe ,
A slit along the periphery of the through hole is formed so that a through hole side portion of the plate cut by the slit and a portion facing the through hole side portion across the slit receive the load, respectively . Load cell . The slit is vertically and horizontally symmetrical with respect to the axial center of the through-hole, and the surface along the periphery of the through-hole of the slit is the same as the inner peripheral surface of the through-hole over the entire length. The load cell according to claim 1, which has an interval of The load meter according to claim 1, wherein the slit is vertically symmetric with respect to the axis of the through hole. The load meter according to claim 1, wherein the slit is symmetrical with respect to the axis of the through hole. 5. The load cell according to claim 1, wherein the surface along the periphery of the through hole of the slit has the same distance from the inner peripheral surface of the through hole over the entire length. . The load meter according to claim 1, wherein the slit has the same width along the periphery of the through hole. Wherein around annular central axis of the plate, a load meter according to any one of claims 1 to 6, wherein the through holes are provided at equal intervals.

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