JPH11183274A - Strain detecting apparatus - Google Patents

Abstract

PROBLEM TO BE SOLVED: To obtain a strain detecting apparatus having a high sensitivity to measure a shearing strain, and easy in maintenance. SOLUTION: The strain detecting apparatus is provided with a shearing strain measuring unit 10 for shearing to deform a member to be measured corresponding to a shearing strain γ(=dX/dY) to detect the strain of the member, a pair of stays 11a 11b extended from the unit 10 substantially in a Y-axis direction, a holder 20 for elastically pressing the stays 11a, 11b to a seat 3a of the member 1 from an X-axis direction, and a bolt 30 for pressing the holder 20 via a belleville spring 24.

Description

DETAILED DESCRIPTION OF THE INVENTION

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention is used for, for example, a load cell for preventing overloading of a truck, and measures a force applied to a member to be measured by detecting a shear strain of the member to be measured. The present invention relates to a mounting structure for a distortion detecting device.

[0002]

2. Description of the Related Art As an example of an apparatus for measuring a force applied to a member to be measured by detecting a shear strain, there is an apparatus described in Japanese Patent Application No. 8-325203 by the present applicant. The mounting structure of the distortion detecting device will be described with reference to the drawings.

FIG. 7 is a side sectional view showing a state in which a distortion detecting device is attached to a member to be measured. In the figure, a hole 2 is formed near the center axis of a member 1 to be measured such as a shackle pin, and a strain detecting device is provided in the hole 2 located at a boundary between a bracket of a vehicle and a leaf spring (not shown). 100 is fixed. The distortion detection device 100 uses the XY
It comprises a shear strain measuring unit 10 for detecting the shear strain γ of the surface, and stays 11a and 11b extending from the shear strain measuring unit 10 in the vertical direction (Y direction). The stays 11a and 11b of the distortion detecting device 100 are fixed to a seat 3 provided in the hole 2 of the measured member 1 and having a surface perpendicular to the X axis.

FIG. 8A is a partial front sectional view showing a fixing portion of the distortion detecting device to a member to be measured, and FIG.
It is a top view showing AA section of (a). In the figure,
A stay 11 extending in the Y direction from the shear strain measuring unit 10
a and b have grooves 12a and 12b extending in the Y direction, respectively.
The grooves 12a and 12b are irradiated with a laser beam by a laser welding machine to melt the thin portions at the bottoms of the grooves 12a and 12b and fixed by welding to the seat 3 of the member 1 to be measured. I have.

Next, the measuring operation by the distortion detecting device 100 will be described. When a cargo is loaded on a vehicle such as a truck, a load F is applied to the shackle pin as the measured member 1 as shown in FIG. 7, and the measured member 1 bends as shown in FIG. At the same time, a shear strain γ = dX / dY is generated in the strain detection device 100 installed in the hole 2 of the member 1 to be measured. The shear strain γ is transmitted to the shear strain measuring unit 10 by the stays 11a and 11b, and shifts the X-direction positions of the upper and lower sides of the substantially rectangular shear strain measuring unit 10 by dX, thereby shearing the whole into a parallelogram shape. The shear strain measuring unit 10 detects the load acting on the member to be measured that caused the deformation by extracting the magnitude of the shear deformation as an electric signal.

[0006]

Since the conventional distortion detecting device is configured as described above, once the distortion detecting device 100 is fixed to the member 1 to be measured, the member 1
If it is difficult to remove the shackle pin or the shear strain measuring unit 10 without damaging it, and a failure occurs in the shear strain measuring unit 10 at the time of fixing work or after fixing the strain detecting device, the entire member 1 to be measured has to be replaced. Was a maintenance problem.

In order to make it possible to remove the strain detecting device, the present applicant has to attach the stays 11a and 11b of the strain detecting device to a holder 2 having no elastic member as shown in FIG.
A structure for fixing the member to be measured 1 by pressing it against the seat 3 of the member 1 to be measured by a bolt 30 via a test piece 00 was tested, and an experiment was performed in which a load was applied to the member to be measured 1. As a result, the sensor output of the shear strain measuring unit 10 is 1/3 of the calculated output.
Only a degree was obtained. This is because the rigidity of the legs 210a, b of the holder 200 for pressing the stays 11a, b of the distortion detecting device against the seat 3 is high, and therefore the stays 11a, b are to be kept linear as shown in FIG. Power works,
It was found that the stay 11a, b did not follow the shear deformation even when the member under test 1 was sheared and the stays 11a, b did not follow the shear deformation, so that the sensor sensitivity was lowered.

Further, since there is no seat in the bolt 30 shown in FIG. 10, it is difficult to control the pressing force, and depending on the method of tightening the bolt, a sufficient pressing force cannot be obtained, or conversely, the tightening force cannot be obtained. Is too strong to break the holder 200 and the stays 11a and 11b.

The present invention has been made in order to solve the above-mentioned problems, and is easy to maintain.
In addition, it is an object of the present invention to obtain a highly sensitive strain detecting device for measuring the shear strain.

[0010]

According to the first aspect of the present invention,
In a strain detecting device for measuring a shear strain generated in a member to be measured, a shear strain measuring section for detecting a shear strain of the member to be measured by performing a shear deformation in accordance with the shear strain of the member to be measured; A stay for attaching the detection unit to the member to be measured, a holder for elastically pressing the stay against a seat of the member to be measured, and a fastening member for supporting the holder to the member to be measured are provided. .

According to a second aspect of the present invention, there is provided a shearing device wherein the displacement in the X-axis direction between two surfaces separated by dY in the Y-axis direction is dX with respect to the X-axis and the Y-axis orthogonal to each other. A strain detecting device for measuring a strain γ (γ = dX / dY), comprising: a shear strain measuring unit for detecting a shear strain of a member to be measured by performing a shear deformation corresponding to the shear strain of the member to be measured; A pair of stays extending substantially in the Y-axis direction from the strain detection unit, a holder for elastically pressing the stay against the seat of the measured member from the X-axis direction, and a fastening member for supporting the holder to the measured member. It is characterized by having.

As described above, the distortion detecting device can be detached by pressing the stay not by welding or the like but by the holder and the fastening member. In addition, the stay is elastically pressed against the seat of the member to be measured by the holder that can flexibly deform, so that the shear deformation of the member to be measured is accurately transmitted to the shear strain measuring unit.

According to a third aspect of the present invention, the holder is provided with a flexible leg extending in the X-axis direction, so that the pressing portion of the holder can easily follow the shear deformation of the member to be measured.

According to a fourth aspect of the present invention, an elastic member that expands and contracts in the X-axis direction, for example, a disc spring, is provided between the holder and the fastening member to stabilize the force for pressing the holder.

According to a fifth aspect of the present invention, a bolt is used as a fastening member, a point having a small contact area is provided on a center line of the bolt, and a pressing force by the bolt is transmitted to the holder through the point. The rotation force of the bolt is prevented from being transmitted to the holder and rotating the holder. Usually, when a shear deformation occurs in the measured member, the bending also occurs at the same time. However, since only the shear strain is desired to be measured by the shear strain measuring unit, the bending of the measured member is absorbed by the point portion. Thereby, the influence of the bending did not affect the output of the shear strain measurement.

The invention described in claim 6 is characterized in that the pressing force of the holder against the seat of the member to be measured of the stay is concentrated only at both ends of the pressing surface of the stay and the seat. Specifically, the contact pressure between the stay and the seat or holder of the member to be measured is provided by providing a recess near the center of the contact surface between the stay and the seat of the member to be measured or the contact surface between the stay and the holder. Focus only on both ends of the surface. When a load or vibration is applied to the member to be measured, a force may be applied to lift or shift the stay from the seat of the member to be measured. It is. Therefore, the stay is prevented from floating or shifting by concentrating the contact pressure on that portion.

The invention according to claim 7 is characterized in that pins are provided between the holder and the fastening member, each pin having a point where the contact portion is small.

[0018]

DESCRIPTION OF THE PREFERRED EMBODIMENTS Embodiment 1 (Structure of Embodiment 1) FIG. 1 shows Embodiment 1 of the present invention.
FIG. 2 is a side sectional view showing a mounting structure of the distortion detecting device according to the first embodiment, and FIG. 2 is a detailed side view of FIG.

In the figure, a cylindrical shackle pin or the like is used as a member to be measured 1 for detecting distortion.
It is installed so as to penetrate through holes provided in brackets such as trucks and leaf springs, so that a load F0 and a load F1 shown in the figure are applied. A hole 2 is formed in the center axis of the member 1 to be measured, and the strain detecting device 100 is fixed near a boundary between the load F0 and the load F1. The strain detecting device 100 includes a shear strain measuring unit 10 for detecting the shear strain γ on the XY plane, and stays 11a and 11b extending from the shear strain measuring unit 10 in the vertical direction (Y direction). The stays 11a and 11b of the distortion detecting device 100 are provided with seats 3 having a surface perpendicular to the X axis provided in the hole 2 of the member 1 to be measured.
a.

The holder 20 serves to press the stays 11a and 11b of the distortion detecting device 100 against the seat 3a of the member 1 to be measured, and a pair of pressing portions 22a and 22b for directly pressing the stays 11a and 11b. It is composed of a pair of elongated rod-like legs 21a and 21b extending in the X-axis direction from the pressing portion, and a base end 20a for engaging the holder with the retainer 23. The legs 21a, b are flexible, and recesses 25a, b are provided near the center of the surface of the pressing portions 22a, b pressing the stays 11a, b against the seat 3a. ing. A disc spring 22 is held between the base end portion 20a of the holder 20 and the retainer 23, and the retainer 23 is configured such that the distal end portion of the bolt 30 is inserted into its inner peripheral space, and the center of the bolt is It is supported with a small contact area by a point 31 having a curved surface provided on the shaft. Bolt 3
0 is screwed along the hole 2 of the member 1 to be measured,
It comes into contact with a seat 3b having a surface parallel to a.

FIG. 3A is a side view showing details of a distortion detecting apparatus 100 preferably used in the first embodiment, and FIG. 3B is a cross-sectional view taken along line BB of FIG. 3A. The figure is shown. The details of the distortion detection device 100 are described in Japanese Patent Application No. 8-325203 of the present applicant.

In FIG. 3, the shear strain measuring section 10 includes a strain detecting section 700 for detecting a shear strain, and a strain detecting section 70.
0 is mounted on the inner side of the detector. The detection unit outer frame 120 forms a substantially rectangular, preferably square, frame composed of two main horizontal beams 121a and 121b parallel to the X axis and two main vertical beams 122a and 122b parallel to the Y axis. And is made of a magnetic material such as iron. In addition, auxiliary horizontal beams 125a and 125b parallel to the X axis are connected between the two main vertical beams 122a and 122b. Low rigidity portions 123a to 123d having reduced cross-sectional areas are provided near both ends of the main cross beams 121a and 121b, and low rigid portions 123i to 123d in the same manner near both ends of the sub-cross beams 125a and 125b.
1 and low rigidity portions 123e to 123h having reduced cross-sectional areas are provided near both ends of the main vertical beams 122a and 122b.

The distortion detecting section 700 is composed of a cross-shaped magnetostrictive element 111 also serving as a core, and coils 110a and 110b wound around the magnetostrictive element 111 serving also as a core. The magnetostrictive element 111 serving also as a core is provided so as to be surrounded by the outer frame 120 of the detection unit, and is preferably arranged in a 45 ° direction with respect to the X axis.
It has legs that extend in four directions: 35 °, 225 °, and 315 °. In the X-axis direction at the center of the core 111, the first
And a second coil 110b is wound around the center of the core 111 in the Y-axis direction. The magnetostrictive element 111 has a welded portion 116 at the tip of the four feet.
It is fixed in the detection unit outer frame 200 by a to d.

The measurement of the shear strain by the strain detector 100 will be described with reference to FIG. Since the low-rigidity portions 123a to 123l are provided near the four vertices of the detection unit outer frame 120 and near both ends of the sub-beams 125a and 125b, the detection unit outer frame 200 is easily deformed into a substantially parallelogram. Due to this shearing deformation, the strain detector 700 moves in the 45 ° direction (L in FIG. 4).
In two directions, the tensile stress is 135 ° (L1 in FIG. 4).
Direction), a compressive stress is generated. Due to this stress, anisotropy occurs in the magnetic permeability of the magnetostrictive element 111 serving also as the core, and
The magnetic permeability in the 5 ° direction increases, and the magnetic permeability in the 135 ° direction decreases. Then, a change in the magnetic characteristics of the magnetostrictive element 111 is detected by the coils 110a and 110b, so that the load and the like are measured.

(Operation of First Embodiment) Next, the mounting operation of the distortion detecting device of the first embodiment will be described. First, when attaching the distortion detecting device 100 to the member 1 to be measured,
The bolt 30 is screwed until the flange 32 of the bolt 30 makes strong contact with the seat 3b of the member 1 to be measured. Then, the disc spring 24 between the holder 20 and the retainer 23 is compressed, and a force for pressing the holder 20 is generated. At this time, since the bolt 30 and the retainer 23 are in contact with each other at the point 31 having a small contact area, the rotational torque from the bolt 30 is hardly transmitted to the retainer 23 side, and the rotational force acts on components other than the bolt, particularly on the holder 20. do not do. In addition, the influence of the bending of the member to be measured 1 is not transmitted to the distortion detection device 100.

Since the compression force generated by the disc spring 22 is determined by the size of the compression allowance determined by the length of each component in the axial direction, the variation can be reduced. Therefore, the force for pressing the holder 20 can be more stable than when the bolt 30 is used to directly tighten the holder 20 without using the disc spring 24.

Since the recesses 25a and 25b are provided at the center of the surfaces of the holder pressing portions 22a and 22b for pressing the stays 11a and 11b, the force for pressing the stays 11a and 11b is at both ends of the pressing surface against the seat 3a. Only focus on it. The deviation is likely to occur due to excessive stress or vibration.
Since it is the both ends of the holding surfaces 1a and 1b, the holding force is concentrated on these portions, so that the displacement between the stays 11a and 11b and the seat 3a caused by vibration or external force can be prevented.

When a load is applied to the member 1 to be measured as shown in FIG. 1, bending and shear strain γ = dX / dY occur in the member 1 to be measured as shown in FIG. In order to accurately transmit the shear strain γ to the shear strain measuring unit 10 of the strain detection device 100, the stays 11a and 11b follow the deformation of the member 1 to be measured by changing the step by dX as shown in FIG. It is necessary to have a stepped shape. Since the legs 21a and 21b of the holder 20 are in the form of flexible and elongated rods, the member 1 to be measured 1
Deformed into a gradual S-shape due to the shear deformation of the target member 1 and can faithfully follow the deformation of the member 1 to be measured. Thereby, the shear strain γ is transmitted to the shear strain measuring unit 10 with high accuracy, and the X-direction positions of the upper and lower sides of the shear strain measuring unit 10 are shifted by dX to be deformed into a parallelogram. Then, the shear strain measuring unit 10 detects the load acting on the member to be measured causing the deformation by extracting the magnitude of the shear deformation as an electric signal.

Embodiment 2 In the first embodiment, a point 31 is provided on the bolt 30 to prevent the rotational force of the bolt 30 from being transmitted to the holder 20 and to eliminate the influence of the bending of the member 1 to be measured. However, the same effect can be obtained with the structure shown in FIG.

FIG. 6 is a side sectional view showing a mounting structure of the distortion detecting device according to the second embodiment. In the drawing, a spring portion 35 that bends in the X-axis direction is provided on the tip side of the bolt 30, and a pin 40 is provided between the spring portion 35 and the holder 60.
Is provided. Both ends of the pin 40 have curved points 41a and 41b, and are respectively supported by the holder 60 and the spring portion 35 with a small contact area. With this configuration, the rotational force of the bolt 30 is not transmitted to the holder 60, and the influence of the bending of the measured member 1 is not transmitted to the distortion detecting device. The holder 60 includes flexible legs 61a and 61b extending in the X-axis direction, and pressing portions 62a and 62b for pressing the stays 11a and 11b against the seat 3a of the member to be measured. The above points 41a,
41b and the spring portion 35 are the same as those in the first embodiment.
Point 31a and the role of the disc spring.

Furthermore, in the first embodiment, the recesses 25a and 25b are provided at the center of the surface of the holder 20 which presses the stay at the tip of the leg. However, both sides of the surface of the stay 11a and b which are pressed by the seat 3a are provided. Even if the recesses 26a, b, c, d are provided,
The force for pressing the stays 11a, b concentrates only on both ends of the pressing surface against the seat 3a, and it is possible to prevent the stays 11a, b from being displaced from the seat 3a due to vibration or external force.

[0032]

As described above, according to the first or second aspect of the present invention, when the distortion detecting device is attached to the member to be measured, there is an effect that the distortion detecting device can be simply and easily removed and maintenance can be facilitated.

According to the third aspect of the present invention, it is possible to easily follow the shear deformation of the member to be measured, and obtain a distortion detecting device with high transmission efficiency and high accuracy.

According to the fourth aspect of the present invention, by providing an elastic member that expands and contracts in the X-axis direction, for example, a disc spring, between the holder and the fastening member, the force for pressing the holder can be stabilized. Furthermore, even if the dimensional accuracy of the mounting portion is not so high, there is an effect that the mounting portion can be fixed with a stable fastening force.

According to the fifth aspect of the invention, the torque of the bolt is prevented from being transmitted to the shear strain measuring section during the mounting operation, and the influence of the bending generated on the member to be measured at the time of measuring the shear strain. There is no effect on the output of the shear strain measuring unit, and there is an effect that a highly accurate strain detecting device can be obtained.

According to the sixth aspect of the present invention, the contact pressure of the stay against the pressing seat can be concentrated to prevent the stay from lifting or shifting, and an effect of obtaining a highly accurate distortion detecting device can be obtained.

According to the seventh aspect of the present invention, it is not necessary to process the tip of a fastening member such as a bolt into a point shape having a curved surface having a small direct contact area. The shape of the member (bolt) is simplified, and a distortion detection device with low manufacturing cost can be obtained.

[Brief description of the drawings]

FIG. 1 is a side sectional view showing a mounting structure of a distortion detection device according to a first embodiment.

FIG. 2 is a detailed side sectional view of FIG.

FIGS. 3A and 3B are a side view and a cross-sectional view illustrating details of a distortion detection device used in the first embodiment; FIGS.

FIG. 4 is a side view showing a distortion measurement operation of the distortion detection device.

FIG. 5 is a side sectional view for explaining the operation of the distortion detection device according to the first embodiment.

FIG. 6 is a side cross-sectional view illustrating a mounting structure of a distortion detection device according to a second embodiment.

FIG. 7 is a side cross-sectional view showing a state where a conventional distortion detecting device is attached to a member to be measured.

FIG. 8 is a front partial cross-sectional view showing a fixing portion of a conventional strain detection device to a member to be measured, and a plan view showing an AA cross section.

FIG. 9 is a view showing a state in which a conventional member to be measured and a distortion detection device are bent.

FIG. 10 is a side cross-sectional view showing a prototype distortion detection device of the present applicant.

[Explanation of symbols]

DESCRIPTION OF SYMBOLS 1 To-be-measured member, 2 holes, 3a, b seat, 10 shear strain measurement part, 11a, b stay, 20 holder, 20a
Base end portion, 22a, b pressing portion, 21a, b leg portion, 23
Retainer, 24 disc springs, 30 bolts, 31 points, 35 springs, 40 pins, 41a, b points, 60 holders, 100 strain detector.

Claims (7)

[Claims] In a distortion detecting apparatus for measuring a shear strain generated in a member to be measured, a shear strain measuring unit for detecting a shear strain of the member to be measured by performing a shear deformation in response to the shear strain of the member to be measured. A stay for attaching the shear strain detecting section to the member to be measured, a holder for elastically pressing the stay against a seat of the member to be measured, and a fastening member for supporting the holder to the member to be measured. A distortion detecting device characterized by the above-mentioned. 2. A shear strain γ (γ = dX) such that a displacement in the X-axis direction between two surfaces separated by dY in the Y-axis direction is dX with respect to the X-axis and the Y-axis orthogonal to each other of the measured member. / DY)
In a strain detector for measuring the shear strain, a shear strain measuring unit that detects the shear strain of the member to be measured by shearing in response to the shear strain of the member to be measured, and substantially in the Y-axis direction from the shear strain detecting unit. Distortion comprising a pair of stays extending, a holder for elastically pressing the stay against the seat of the member to be measured from the X-axis direction, and a fastening member for supporting the holder to the member to be measured. Detection device. 3. The distortion detecting device according to claim 2, wherein the holder has a flexible leg extending in the X-axis direction. 4. An X between the holder and the fastening member.
4. The distortion detecting device according to claim 2, wherein an elastic member that expands and contracts in an axial direction is provided. 5. The fastening member is formed by a bolt having a point having a small contact area on a center line of the bolt,
The distortion detecting device according to any one of claims 2 to 4, wherein a pressing force by a bolt is transmitted to the holder through the point. 6. The structure according to claim 2, wherein the pressing force of the holder against the seat of the member to be measured of the stay is concentrated only at both ends of the pressing surface of the stay and the seat. The distortion detection device according to claim 5. 7. A pin according to claim 2, further comprising a pin between the holder and the fastening member, the pin having a point where a contact portion is small. 3. The distortion detection device according to 1.