JPH02641Y2 - - Google Patents

Description

DETAILED DESCRIPTION OF THE INVENTION The present invention relates to a strain detector that is attached to an object to be measured, detects strain occurring in the object, and sends out an electrical output signal corresponding to the strain.

For example, when compressive strain is detected by this type of strain detector and measured by a strain meter, a buckling phenomenon occurs in the strain-generating plate, especially in the strain-generating part, making accurate strain measurement impossible. There is. Therefore, in some conventional strain detectors, the strain-generating part (sensing part) of the strain-generating plate is formed into a hollow thick-walled cylinder shape or a square cross-section to enlarge the cross-sectional shape. Some products are designed to prevent buckling.

However, in such conventional strain detectors, the strain-generating part has a large cross section, so if there are irregularities on the mounting surface of the object to be measured (for example, a rough surface such as the so-called black surface of a casting), strain may occur. When the detector is installed, bending force acts on the strain detector, and a considerable amount of the output from that bending force is included, making it impossible to accurately measure the tensile strain or compressive strain of the object to be measured. Not only was this not possible, but in extreme cases, the measurement range could be significantly exceeded during the installation stage, making measurement impossible. In order to avoid such a situation, conventionally, the strain detector mounting surface of the object to be measured was finished to be a smooth plane, and the mounting bolt holes or screw holes were precisely finished using a reamer or precision tap. Special jigs and tools are required for such work, which takes a lot of time and increases the cost of tools and personnel.

In addition, the conventional strain detectors described above have a large sensing section in order to prevent buckling, which increases the rigidity of the object to be measured. Since strain is supported by the rigidity of the strain detector itself, accurate strain detection has been difficult. Furthermore, in manufacturing the above-mentioned conventional strain detector, the strain-generating portion is formed by cutting a round bar or square material, which inevitably increases the processing cost.

The present invention was developed in view of the above circumstances, and is easy to manufacture and attach to the object to be measured, and has low rigidity against compression and tension.
It is resistant to buckling due to compression and is almost unaffected by bending, so there is no need to finish the strain detector mounting surface of the object to be measured very closely, and the strain detector itself can be manufactured at low cost. The purpose of the present invention is to provide a strain detector that can save on jigs and tools and labor costs associated with installation.

The purpose of this invention is to provide a thin strain plate in which a narrow strain generating part is formed in the center and circular holes are bored in the vicinity of both ends in the loading direction, and the surface of the strain generating part and Strain gauges attached to the back surface with their gauge axes oriented in the load direction and a direction perpendicular thereto, and a thin plate shape with a thinner wall than the strain plate and about the same size as the strain plate when viewed from the plane. A through hole sufficiently larger than the strain-generating portion is formed in the center of each plate, and a circular hole is bored at a position corresponding to the circular hole of the strain-generating plate in a direction perpendicular to the load direction. Both ends of the plate are bent at substantially right angles in the same direction to form reinforcing ribs to prevent buckling, and the surfaces on which the reinforcing ribs are formed are on the outside so as to sandwich the strain plate from the front and back sides. Two reinforcing plates of the same shape overlapped in this way,
The strain-generating plate stacked as described above and the second
A fixing member that is fitted into the circular holes drilled at both ends of the reinforcing plate to fix the two ends thereof, and has a bolt insertion hole drilled therein for attaching the reinforcing plate to the object to be measured; Covering at least each outer plate surface of the two reinforcing plates fixed by the member, the strain plate facing the through hole, and the plurality of strain gauges, and having a height that is approximately the same as the height of the reinforcing rib. This can be achieved by constructing a molded body made by filling and solidifying a filler and having a modulus of elasticity sufficiently smaller than that of the strain plate.

Embodiments of the present invention will be described in detail below with reference to the drawings.

Figures 1 to 5 all show the configuration of an embodiment of the present invention, of which Figure 1 is an exploded perspective view, Figure 2 is a plan view, and Figure 3 is Figure 2A. -A
4 is a front view, and FIG. 5 is a sectional view taken along the line BB in FIG. 2.

In FIGS. 1 to 5, reference numeral 1 denotes a strain plate made of a thin plate material. A portion 1a is provided, and the longitudinal direction (load direction)
Circular through-holes 1b, 1b are bored near both ends of the strain-generating portion 1a, respectively, and two strain gauges SG are attached to each of the front and back sides of the center of the strain-generating portion 1a by adhesive or other means. .

Reference numeral 2 denotes a reinforcing plate that is thinner than the strain plate 1 and has the same size as the strain plate 1 when viewed from above. A rectangular through hole 2a that is sufficiently larger than the attachment area of the strain gauge SG attached to the strain gauge 1 is bored,
Near both ends of the reinforcing plate 2 in the longitudinal direction (load direction), circular holes 2b having the same spacing and the same diameter as the two through holes 1b provided in the strain-generating plate 1 are bored. Reinforcing ribs 2c for preventing buckling are provided at both ends in the short side direction (direction perpendicular to the load direction), each bent at 90 degrees to the same side. As shown in the accompanying drawings, especially FIGS. 3 and 5, this reinforcing plate 2 is made of a thinner plate material than the strain-generating plate 1, and has through holes 2a and 2b punched out using a press machine, for example. The reinforcing rib 2c is formed by bending.

Reference numeral 3 denotes a fixing member, which has a cylindrical body 3a with a flange, which has a circular hole 3c as a bolt insertion hole for mounting a strain detector in the center, and an inner diameter that fits into the cylindrical part of the cylindrical body 3a with a flange. It consists of a ring body 3b having the same outer diameter as the flange, and serves to fix the strain plate 1 and the reinforcing plate 2 as described below.

In FIGS. 3 and 5, 4 is a molded body for buckling prevention made by hardening a hard filler such as epoxy resin or synthetic rubber, and the elastic modulus is sufficiently smaller than that of the strain plate 1, for example. , 1/10 of strain plate 1
The following will be selected.

The strain detector 5 having such a configuration is assembled as follows.

First, as can be inferred from FIG. 1, the surfaces of the two reinforcing plates 2 opposite to the surfaces on which the reinforcing ribs 2c are provided are brought into contact with the strain-generating plate 1, respectively. The strain plates 1 are stacked one on top of the other, and the cylindrical portion of the flanged cylindrical body 3a, which is one of the fixing members 3, is inserted into each circular hole 2b of the reinforcing plate 2 and each through hole 1 of the strain plate 1.
b, and make it protrude outward from the reinforcing plate 2 on the opposite side. Next, after fitting the ring body 3b into this protruding cylindrical part, the cylindrical part is caulked, and the strain plate 1 and the two reinforcing plates are 2 are fixed together near both ends thereof to be integrated.

Filler material such as the epoxy resin is placed on the surface of the two reinforcing plates 2 of the integrated strain detector 5 on which the reinforcing ribs 2c are provided, at a height that is approximately the same as the height of the reinforcing ribs 2c. The molded body 4 is formed by filling the molded body to the extent that it is thick and solidifying it. At this time, the filler also flows into the peripheral portions of the strain-generating portion 1a of the strain-generating plate 1, the strain gauge SG, and the fixing member 3, so that these are integrated via the mold body 4, so to speak. This state is shown in FIGS. 2 to 5.

To explain the operation of the present invention configured in this way, first, the strain detector 5 is placed on the object to be measured.
A hole or a screw hole is formed for a bolt (not shown) to attach the bolt, and the bolt is inserted into a circular hole 3c provided in the fixing member 3, and then screwed into, for example, the screw hole provided in the object to be measured. In some cases, the strain detector 5 is attached to the object to be measured.

If a compressive load is applied to the object to be measured, the strain plate 1, the two reinforcing plates 2 and the molded body are 4 and are compressed, contracting in the longitudinal direction (load direction) and expanding in the width direction (direction perpendicular to the load direction). As a result, the two strain gauges SG attached to the front and back surfaces of the strain-generating portion 1a of the strain-generating plate 1 also deform in accordance with the contraction or expansion of the strain-generating portion 1a. In general, strain gauges SG are attached to the front and back surfaces of the strain-generating portion 1a in the load direction and a direction perpendicular thereto, and these four strain gauges constitute a Wheatstone bridge. Therefore, from the output end of this bridge, an output signal corresponding to the strain (compressive strain in this case) in the strain-generating portion 1a is sent out, and this is measured by a strain measuring device (not shown) to measure the amount of strain. can be measured. When this compressive strain is detected by the strain detector according to the above-described embodiment, the reinforcement plate 2 is configured to receive the compressive force applied to the strain detector 5, so that the reinforcement plate 2 has a large bending rigidity. Buckling can be prevented by the ribs 2c.

In addition, the cross section of the portion of the strain detector 5 corresponding to the strain-generating portion 1a is formed to be large by a pair (both sides) of the molded body 4 having a height (thickness) that is approximately the same as the height of the reinforcing rib 2c. Therefore, this molded body 4 also has a much greater bending rigidity than the strain-generating portion 1a, and therefore this molded body 4 also acts effectively against buckling. Therefore, even when a large compressive strain occurs, buckling does not occur and the amount of strain can be detected accurately.

On the other hand, tensile strain can be measured in a similar manner (although buckling is not involved).

In addition, the strain-generating portion 1a is formed narrowly, and the reinforcing plate 2
As mentioned above, it has a thin plate material having a wall thickness thinner than that of the strain plate 1, and a through hole 2a is formed in the center (although the through hole 2a does not connect the reinforcing plate 2 and the strain plate 1). The molded body 4 has a much smaller elastic modulus than the strain plate 1 (for example, 1/10 (below) is made of a filler made of the following materials. For this reason, compared to conventional methods in which buckling is prevented by forming the strain-generating part into a hollow thick-walled cylindrical shape or a square cross-sectional shape to increase the cross-sectional shape, the buckling strength is The stiffness of the strain detector 5 as a whole is quite low, and therefore, it is possible to detect compressive strain in objects to be measured with low stiffness, such as thin plates and plastics.

Furthermore, when installing the strain detector 5 on the object to be measured, if the mounting surface is rough to some extent or the two bolt mounting holes provided in the object to be measured are not properly drilled in parallel, In this case, bending is applied to the strain detector 5, and the strain plate 1 is also bent, but the strain gauge SG is attached to the strain generating part 1a located at the center in the thickness direction of the strain detector 5 having a certain thickness. The strain plate 1 is stacked with two reinforcing plates 2, 2 in the shape of a sandwich arch, and the molded body 4 is also formed symmetrically on both sides (upper and lower surfaces in the figure), so that the strain plate 1 is at the center of the cross section, that is, the center of bending, and even if bending is applied, the bending stress is close to zero, so the strain gauge
Almost no bending output is sent out from the SG. Therefore, for example, the strain detector can be directly attached to the object to be measured, which has a somewhat rough surface, making the attachment work much easier. To explain this more specifically, for example, the above two bolt holes drilled in the object to be measured are not properly parallel,
Alternatively, if they become unparallel due to changes over time, the central axes of the fixing members 3 on both sides will also become unparallel.
The entire strain detector 5 is curved upwardly or downwardly in FIG. 4. For example, if the strain detector 5 is curved in an upwardly convex manner, the strain plates 1 and 2
Tensile strain (tensile stress) occurs on the upper surface of the strain detector 5, which has a considerable thickness and consists of two reinforcing plates 2 and the molded body 4, that is, the upper surface of the molded body 4, and the lower surface of the strain detector 5, That is, the mold body 4
Compressive strain (compressive stress) occurs on the lower surface of the plate, but the strain plate 1 (strain part 1a) is located at the center of the cross section, and its thickness is thin.
surface), that is, at the center of bending, so almost no compressive strain or tensile strain occurs. Therefore, no output due to bending is sent out from the strain gauges SG attached to the upper and lower surfaces of the strain-generating portion 1a located at the bending center. Therefore, this strain measuring instrument 5
can be directly attached to the object to be measured which has a somewhat rough surface, making the attachment work much easier.

Furthermore, since strain gauges SG are attached to the front and back surfaces of the strain generating section 1a with their gauge axes facing the load direction and a direction perpendicular thereto, the strain gauges SG are attached at corresponding positions on the front and back surfaces of the strain generating section 1a. By connecting the attached strain gauges to opposite sides of the Wheatstone bridge, even if the strain-generating portion 1a curves significantly, it is electrically canceled, so that the influence of the curvature does not occur.

Furthermore, since the strain gauge SG is covered by the molded body 4, it is possible to prevent insulation from deteriorating due to moisture absorption that is blocked from the outside air.

Furthermore, since the strain plate 1 and the reinforcing plate 2 only need to be formed by punching and bending thin plates, they can be easily processed using a press machine and the manufacturing cost can be reduced.

Note that the present invention is not limited to the above-described embodiments, but can be implemented with various modifications.

For example, the strain detector 5 itself can be used by being housed in a case 6 made of plastic, for example, as shown in FIGS. 6 and 7. In this case, the case 6 is sized to accommodate the strain detector 5 with plenty of room, and is provided with a circular through hole 6a through which a part of the fixing member 3 can protrude, and one end of the case 6 is designed to accommodate the strain sensor 5. Derive the strain output and
A cable 7 is connected to transmit the strain to the strain measuring device.

As described in detail above, according to the present invention, it is possible to provide a strain detector that exhibits various effects listed below.

First of all, both the strain plate and the reinforcing plate are in the form of a thin plate, and the shaping of the outer shape, the bending of the reinforcing ribs, and the drilling of circular holes and through holes can be easily performed using a press machine. Therefore, it can be manufactured at low cost.

Secondly, the strain plate itself has a thin plate shape, and the strain generating portion is formed narrowly, so the cross section is extremely small, and the reinforcing plate is thinner than the strain plate.
Moreover, the section facing the strain-generating part has a larger through-hole than the strain-generating part, so its cross section is even smaller than the strain-generating part, and the molded body has a cross section larger than the strain-generating part and the reinforcing plate. Since the elastic modulus is sufficiently lower than that of a strain plate, the rigidity against tension and compression is small. Therefore, it is possible to detect with high sensitivity the tensile strain and compressive strain of objects to be measured with low rigidity, such as thin plates and plastics, which was impossible with conventional devices.

Thirdly, since the two reinforcing plates are stacked so that their respective reinforcing ribs are on opposite sides of the strain plate, their bending rigidity is much greater than that of the strain plate. As mentioned above, the molded body is formed to have almost the same height as the reinforcing ribs of the reinforcing plate, and is much larger than the cross section of the strain plate, so its bending rigidity is much higher than that of the strain plate. big. Therefore, despite having low tensile and compressive rigidities, it has strong properties against buckling under compression.
Therefore, in particular, it is possible to detect compressive strain of an object to be measured with low rigidity, which has been considered difficult in the past, with high precision without causing buckling.

Fourth, since the structure is such that a pair of reinforcing plates are stacked on both sides of a thin strain plate at the center, with the reinforcing ribs on the outside, the strain plate has a cross-sectional center,
In other words, it is on the neutral plane of bending, and even if bending force is applied, the bending stress is close to zero.Therefore, even if the strain detector is installed on the object to be measured, which has a somewhat rough surface, it will not be possible to In this way, the output due to bending force is not mixed in the strain detection output, and an output corresponding only to tensile strain or compressive strain can be obtained, and therefore the strain detector mounting surface of the object to be measured can be finished very precisely. There is no need for this, and the labor costs associated with jigs and installation can be significantly reduced.

[Brief explanation of the drawing]

Figures 1 to 5 all show the configuration of one embodiment of the present invention, of which Figure 1 is an exploded perspective view, Figure 2 is a plan view, and Figure 3 is Figure 2A. -A
4 is a front view, FIG. 5 is a sectional view taken along line B-B in FIG. 2, and FIGS. 6 and 7 are
The figures are a plan view and a front view showing the strain detector according to the present invention housed in a case. 1...Strain plate, 1a...Strain part, 1b, 2a...
...Through hole, 2b...Round hole, 2...Reinforcement plate, 2c...
Reinforcement rib, 3...fixing member, 4...mold body,
5...Strain detector, 6...Case, 7...Cable.

Claims (1)

[Scope of utility model registration request] A thin strain-generating plate having a narrow strain-generating part formed in the center and having circular holes bored near both ends in the load direction; Strain gauges attached with their gauge axes oriented in orthogonal directions; and strain gauges each having a thin plate shape with a thinner wall than the strain plate and having the same size as the strain plate when viewed from the plane, and a central portion of each strain gauge. A through hole that is sufficiently larger than the strain-generating portion is formed in the strain-generating portion, and circular holes are bored at positions corresponding to the circular holes of the strain-generating plate, and both ends of the strain-generating plate are oriented in substantially the same direction in a direction perpendicular to the load direction. Reinforcing ribs are formed to prevent buckling by being bent at right angles, and the same shape is stacked so that the strain plate is sandwiched between the front and back surfaces with the surfaces on which the reinforcing ribs are formed facing outward. The two reinforcing plates forming a shape, the strain-generating plate stacked as described above, and the two reinforcing plates are fitted into the circular holes bored at both ends thereof, and both ends thereof are fixed. a fixing member having a bolt insertion hole for attaching it to the object to be measured; and at least each outer plate surface of the two reinforcing plates fixed by the fixing member, and the origin facing the through hole. A strain plate and a molded body having an elastic modulus sufficiently smaller than that of the strain plate, which is made by filling and solidifying a filler so as to cover the strain plate and the plurality of strain gauges and to have a height substantially the same as the height of the reinforcing ribs. A strain detector characterized by: