JPH0194234A - Load converter - Google Patents

Abstract

PURPOSE:To obtain large strain output and a load-strain characteristic having good linearity, by providing a pair of counter bores on a sensitive part by drilling so as to reach the vicinity of a load shaft from the mutually opposite side surfaces thereof and forming a strain generating part between the bottom parts of said bores to bonds strain gauges thereto. CONSTITUTION:Counter bores 14, 15 having the same depth are provided to a sensitive part 10 from the front and back surfaces thereof by drilling so as to leave a strain generating part 16. Further, adjusting holes 17, 20 are provided to the strain generating part 16 by drilling in the vicinities of the lateral parts of the bonding regions of strain gauges SG 3a, SG 3b, SG 4a, SG 4b for detecting lateral strains. When load is applied to a load introducing part 9, said load is concentrated to small regions through constricted parts 12, 13 to act on the upper and lower parts of the holes 14, 15 and, as a result, the sensitive part 10 is deformed so that the holes 14, 15 are deformed into an oval shape. By this constitution, gauges SG 1a, SG 2a, SG 1b, SG 2b for detecting longitudinal strains mainly receive only the longitudinal strains and the strain gauges SG 3a, SG 4a, SG 3b, SG 4b mainly receive lateral strains. By this method, a load- strain characteristic is set so as to show good linearity and the miniaturization of an outer shape can be achieved.

Description

Detailed Description of the Invention (a) Technical Field The present invention relates to a load converter, and more particularly, a load introduction section, a sensing section, and a load support section are successively connected along a load axis, and the load introduction section The present invention relates to a load converter that converts a load to be measured applied to a load into an electrical quantity using a strain gauge and detects it.

(b) Prior Art A conventional load transducer using this type of strain gauge has a load axis ( The strain gauge SG1. Oa and 5G20a and strain gauges 5G10b and 5G20b, which are not shown in the figure, are attached, and these strain gauges 5G10a, 5G10b, 5G20a are attached.
.

A Wheatstone bridge circuit (not shown) is configured by the S G 20b, and an electric signal (output) corresponding to the load applied to the load introducing section], a is obtained from this Wheatstone bridge circuit.

However, the columnar type load converter shown in FIG. 5 has the following drawbacks.

First, there is a drawback that a large strain output cannot be obtained.

That is, the load introducing portion 1a and the load supporting portion 1b of this strain body 1
When it is assumed that a compressive load is applied between Strain in the direction (sometimes referred to as "longitudinal strain") occurs in the direction perpendicular to the load axis direction (left and right direction in the figure).
is expanded, resulting in tensile strain (hereinafter, strain in the direction perpendicular to the load axis direction may be referred to as "transverse strain"). The transverse strain/longitudinal strain at this time is determined by the Poisson's ratio specific to the material of the strain body, and is, for example, 0.3 in the case of steel. Therefore, strain gauge 5G10a detects longitudinal strain.

5G10b and strain gauge S G that detects lateral strain
Even if a Wheatstone bridge circuit is constructed with SG 20a and SG 20b, the output is only 2.6 times the output obtained with one strain gauge for detecting longitudinal strain, which is not sufficient as a strain output.

The second drawback is that the load-strain (stress) characteristics exhibit nonlinearity.

This is because when, for example, a compressive load is applied to the load introducing portion 1a of the strain-generating body 1 as described above, the strain-generating portion 1c contracts in the direction of the load axis, and accordingly expands in the direction perpendicular to the load axis (the cross-sectional area (increases), which acts to reduce the strain in the axial direction of the load.

Thirdly, it has the disadvantage that it is greatly influenced by lateral loads and eccentric load components that act from a direction different from the load axis direction, and this is mixed in as an error component in the load measurement value in the load axis direction. .

That is, strain gauges (SG 10a-SG 20b
) is attached to the outer surface of the strain-generating part IC that is away from the central axis (load axis), and when the strain-generating body 1 bends under the lateral load (or uneven load), one of the outer surfaces is compressed and 180°
Since the other outer surface on the opposite side is stretched, the corresponding strain gauges (S G 10a...5G20b) are also compressed or stretched.

It is possible to configure a circuit so that the compression and expansion of the strain gauge are canceled by a Wheatstone bridge circuit, but the compressive strain and tensile strain on the outer surface of the strain generating part IC are not necessarily theoretical. In the end, components of the lateral load and unbalanced load are mixed into the load component in the axial direction of the load, reducing measurement accuracy.

By the way, Figures 6 and 7 show a front view and a side view of a load transducer designed to improve the solid (empty) columnar strain body type load transducer, which has many drawbacks. There is a load converter as shown (hereinafter sometimes referred to as "reference example converter").

In the load converter 2 shown in this reference example, a load introducing section 3, a sensing section 4, and a pedestal section 5 as a load supporting section are successively connected.
It is integrally formed as a whole.

The sensing part 4, the load introducing part 3, and the pedestal part 5 are connected to each other.
The constricted portions 6 and 7 are formed by drilling and slotting so that the cross-sectional area is smaller than that of each cross-sectional area. A circular hole 4a is bored in the central part of the sensing part 4, and the circular hole 4a is centered on the central part of the sensing part 4 in the direction of the load axis X on the load axis X. Strain gauges 5G40a for transverse strain detection are installed on the upper and lower wall surfaces through which X passes.
.

Strain gauges 5G30a for detecting longitudinal strain are provided on the left and right wall surfaces through which an axis perpendicular to the load axis X on the inner wall surface of the circular hole 4a passes through 40b.

30b are glued together.

The operation of the reference example having such a configuration will be explained.

When a load to be measured (for example, a compressive load) is applied to the load introduction section 3, the load is concentrated at the constriction section 6 and then transferred to the sensing section 4.
It acts concentratedly on the vicinity of the upper end of the circular hole 4a. On the other hand, the reaction force against the applied load is generated from the pedestal part 5 to the constriction part 7.
, and acts on the vicinity of the lower end of the circular hole 4a of the sensing section 4. Then, the force is concentrated on the sensing parts 4 near the upper end and the lower end of the circular hole 4a, so the sensing parts 4 are pressed and the circular hole 4a is deformed into an elliptical shape. Therefore, the strain gauges 5G30a and 30b for detecting longitudinal strain are contracted, and the strain gauges 5G40a and 5G40b for detecting transverse strain are expanded. As a result, an electrical signal corresponding to the applied load can be extracted from the output end of the Wheat's 1 Henbridge circuit (not shown), which is composed of strain gauges 5G30a and 5G30b and strain gauges 5G40a and 5G40b.

Reference example load converter 2 that is configured and operates in this way
For example, when a compressive load is applied, the left and right sides 4b of the circular hole 4a in the sensing section 4.

4c is deformed so as to curve outward while being compressed, so there is almost no change in cross-sectional area, and as in the case of the conventional example shown in Fig. 5, longitudinal strain due to increase in cross-sectional area does not occur. Since there is almost no suppressing effect, the load-strain characteristics come to show extremely good linearity.

In addition, in the load transducer 2 shown in this reference example, the upper and lower ends of the circular hole 4a to which the strain gauges 40a and 40b are glued, and the left and right ends to which the strain gauges 30a and 30b are glued are almost the same. As a result, the ratio of longitudinal strain to transverse strain is approximately the same, and as a result, the strain output obtained by four strain gauges is equal to the strain output obtained by one strain gauge. The output is increased to nearly four times the output.

However, the load transducer of the reference example having such advantages also has the following drawbacks.

First, for the same reason as the load converter shown in Fig. 5, it is easily affected by lateral loads and unbalanced loads, and this has the disadvantage that it causes an error in the load measurement value in the load axis X direction. be.

Second, since the strain gauges 5G30a and the like are bonded to the inner circumferential surface of the circular hole 4a, that is, the arcuate surface, it is difficult to bond the strain gauges 5G30a and the like, and it is difficult to place the strain gauges 5G30a and the like in precise positions. In addition to the problem that it is difficult to bond, there are also drawbacks such as shortened fatigue life because it is bonded in a pre-curved state, and easy to change over time, reducing measurement accuracy.

Thirdly, there is a drawback that the outer shape of the sensing section 4 tends to increase in size.

That is, the thinner the shape (cross-section) of the constrictions 6 and 7 (the smaller the cross-sectional area), the better for deforming the sensing part 4 so that its circular hole 4a changes from a circular shape to an elliptical shape. , the cross-sectional area of the constrictions 6, 7 cannot be made smaller than the limit regulated by the rated load. Therefore, in order to make the ratio of longitudinal strain and transverse strain almost equal, circular hole 4
There is no other way than to increase the diameter of a. However, if the circular hole 4a is made larger, the cross-sectional area of the left and right sides 4b and 4c of the sensing section 4 that supports the load must also be made to a size that is regulated by the rated load, so the external shape of the sensing section 4 will inevitably change. This leads to the disadvantage of increasing the size.

(c) Purpose The present invention was made in view of the above-mentioned circumstances, and its purpose is to obtain a large strain output, exhibit good linearity in load-strain characteristics, and suppress lateral loads and unbalanced loads. It is hardly affected by strain gauges, the work of attaching strain gauges is easy, aging and fatigue failure are less likely to occur, and in addition, the load is much smaller than the reference examples shown in Figures 6 and 7. The purpose is to provide a converter.

(d) Structure In order to achieve such an object, the first invention (the invention set forth in claim 1) has a structure in which a load introduction part, a sensing part, and a load support part are sequentially arranged along a load axis. In a load converter that converts the load to be measured applied to the load introduction part into an electrical quantity and detects the load, the sensing part is connected between the sensing part and the load introduction part and the load support part, respectively. The cross-sectional area perpendicular to the load axis is smaller than that and forms a transmitting part coaxial with the load axis, and is transmitted along an axial direction perpendicular to the load axis from mutually opposite sides of the columnar sensing part. By drilling a pair of counterbore holes reaching near the load axis, a strain-generating portion is formed between the bottoms of the pair of counterbore holes, and a sensing axis is formed in the direction of the load axis of the strain-generating portion. A strain gauge for detecting longitudinal strain is attached with the sensitive axis facing the direction perpendicular to the load axis of the strain generating part, and a strain gauge for detecting transverse strain is attached with the sensitive axis facing in the direction perpendicular to the load axis of the strain generating part. The cross-sectional shape of the strain-generating portion is formed such that the ratio of the amount of strain at the attached portion of the strain gauge to the amount of strain at the attached portion of the strain gauge for longitudinal strain detection is equal to or higher than Poisson's ratio, and the strain gauge is used to measure the load. It is configured to convert the magnitude of the load to be measured applied to the introduction part into an electrical quantity and detect it, and also according to the second invention (
In the invention described in claim 2, a load introduction section, a sensing section, and a load support section are successively connected along a load axis, and the load to be measured applied to the load introduction section is converted into an electrical quantity. In the load transducer that detects the load, the sensing part, the load introducing part, and the load supporting part each have a smaller cross-sectional area perpendicular to the load axis than the sensing part and are coaxial with the load axis. A pair of counterbore holes are formed from opposite sides of the pillar-shaped sensing part to form a transmission part and reach near the load axis along an axial direction perpendicular to the load axis. A strain-generating portion is formed between the bottoms of a pair of counterbore holes, and a strain gauge for longitudinal strain detection is attached with the sensing axis of the strain-generating portion facing in the direction of the load axis. A strain gauge for transverse strain detection is attached with the sensitive axis directed in a direction perpendicular to the load axis, and the transverse strain detection strain gauge is attached to the strain generating portion in the vicinity of the side of the attachment portion of the strain gauge for transverse strain detection. A small-diameter adjustment hole is drilled to adjust the ratio of the strain amount at the attachment site of the strain gauge for vertical strain detection to the strain amount at the attachment site of the strain gauge for longitudinal strain detection to be equal to or higher than Poisson's ratio. The load to be measured applied to the load introduction part is converted into an electrical quantity and detected.

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

FIG. 1, FIG. 2, and FIG. 3 all show the configuration of an embodiment of the load converter according to the present invention, and FIG.
A front view, FIG. 2 is a cross-sectional view taken along the line A--A in FIG. 1, and FIG. 3 is a cross-sectional view taken along the line B--B in FIG.

In FIGS. 1 to 3, the load converter 8 has a load introducing section 9, a sensing section 10, and a pedestal section 11 as a load supporting section arranged in sequence from above, and is made entirely of one material (a round bar). ) is formed in one piece by cutting away.

The sensing part 10, the load introduction part 9, and the pedestal part 11- are connected to each other so that the cross-sectional area is smaller than that of the sensing part 10, the load introduction part 9, and the pedestal part 11, respectively. The constricted part as a transmission part is cut from the side circumferential surface on the 180° opposite side to a depth that leaves a predetermined thickness, that is, a thickness that can ensure a cross-sectional area that can sufficiently withstand when the rated load is applied. 12 and 13 are formed.

At the center of the front of the sensing section 10, there are lines on the load axis
A pair of counterbore holes 14 and 15 whose circular center is the intersection of the load axis and the axis Y perpendicular to the load axis X, passing through the center in the direction of the load axis A strain-generating portion 16 having a predetermined uniform thickness is formed between the bottoms of the pair of counterbore holes 14-, 15 by drilling from the outer peripheral surface on the opposite side to a depth reaching near the load axis X. .

On both sides of the circular strain-generating portion 16 (bottoms of the counterbore holes 14 and 15), on the load axis Strain gauges 5G1a, 5G2a, and 5G1b for longitudinal strain detection, one pair each on the front and back (total 2 pairs), with the sensitive axis facing
, 5G2b is applied by gluing, vapor deposition, sputtering, or other means.

On the other hand, a pair of strain gauges 5G3a for detecting transverse strain (two pairs in total), one pair each on the front and back sides (two pairs in total), are placed at symmetrical positions with respect to the load axis X, with their sensing axes facing the axis Z direction perpendicular to the load axis.
5G4a and gauge 5G3b, SG4. Attach b.

Strain gauges 5G3a, 5G3b, and 5G4a for detecting lateral strain in the above-mentioned strain generating section 16.

A strain gauge 5G1 for detecting the longitudinal strain is installed near the side of the attached part of 5G4b (on both sides in the direction orthogonal to the sensitive axis).
a, 5G2a, 5Gib, and 5G2b attachment parts, and the strain gauges 5G3a and 5G for detecting the strain in the tank.
4a, 5G3b, and 5G4b, the cross section of the strain-generating part (in particular,
In this case, the small diameter adjustment hole 17.18 for adjusting the width dimension)
and 19.20.

FIG. 4 is a circuit diagram showing a Wheatstone bridge circuit configured with the strain gauges in the embodiment described above.

In the same figure, strain gauge 5G1a for detecting longitudinal strain
and 5G2a, 5G1b, and 5G2b are connected separately to one opposite side of the bridge, and strain gauges 5G3a, 5G4a, 5G3b, and 5G for transverse strain detection are connected separately to one opposite side of the bridge.
4b are distributed and connected to the other opposite side adjacent to the opposite side of the one bridge.

Next, the operation of this embodiment configured as described above will be explained.

The load to be measured applied to the load introducing section 9 and the reaction force transmitted from the pedestal section 11 to resist the load are converted into loads (forces) through the constricted sections 12 and 13, respectively.
are concentrated in small areas, counterbore holes 14 and 1, respectively.
As a result, the sensing portion 10 is deformed such that its counterbore holes 14 and 15 are deformed from a circular shape to an elliptical shape.

Then, strain gauge SG1a, 5 for longitudinal strain detection
G2a and strain gauge 5G1b.

5G2b mainly receives only longitudinal strain, and the other strain gauges 5G3a, 5G4a and 5G3b, 5G4b mainly receive lateral strain.

Therefore, also in the case of this embodiment, the sensing portion 10 is deformed so that the counterbore holes 14 and 15 change from a circular shape to an elliptical shape. In this respect, it is the same as the reference example shown in FIGS. 6 and 7. Therefore, it goes without saying that the load-strain characteristics of this example also show good linearity. Without drilling a circular hole penetrating from the front to the back, the side peripheral surfaces opposite to each other 1 (that is,
Counterbore holes 14 and 15 of the same depth are bored from the front and rear sides), and secondly, strain gauges 5G3a and 5G3b and SG4.
Adjustment holes 17.18 and 19.20 are respectively drilled in the lateral vicinity of the attachment portions a and 5G4b.

Due to the above-mentioned first and second differences, this embodiment can realize a smaller external shape.

That is, in the reference example, when trying to obtain a large strain output for the reasons already mentioned, the circular hole 4a becomes larger with respect to the constriction part 6.7, and the sensing part 4 as a whole becomes larger.
However, in this example, although the cross-sectional area of the constricted portion 12.13 is determined by the rated load as in the reference example, the counterbore is A major feature is that the diameter of the hole 14°], 5 can be made smaller than the value that satisfies the condition that the longitudinal strain and the transverse strain are comparable.

The reason for this is that by making the hole diameters of the counterbore holes 14 and 15 smaller than the above condition values, the transverse strain becomes smaller than the longitudinal strain, but the diameter of the adjustment holes 17.18 and 1.9.20 By setting the spacing to the optimal value,
It is possible to change the cross-sectional area of the strain-generating portion 16 that causes longitudinal strain and transverse strain, and therefore, it is possible to bring transverse strain closer to longitudinal strain so that both have approximately the same value.

Therefore, the counterbore hole 14. , 15 can be made small in diameter, so
Even if both ends 21 and 22 have a cross-sectional area that can sufficiently withstand the rated load, the sensing section 10 as a whole can be made smaller.

Further, in the above embodiment, strain gauges 5G1a to 5G4b
is attached along the load axis X and on the thin strain-generating part 1-6, so even if a lateral load or an uneven load is applied to the load introducing part 9 and the sensing part 10 is bent... Strain gauges attached near the neutral axis (in this case, the load axis) of the humidifier hardly expand or contract, and outputs of lateral load and unbalanced load components are unlikely to occur. Even if a small amount occurs, the fourth
This is electrically canceled by the Wheatstone bridge circuit shown in the figure, and it is possible to obtain an electrical signal corresponding only to the load component in the load axis direction.

In addition, since the strain-generating portion 16 in this embodiment has a planar shape, it is easy to attach the strain gauge, and it has the advantage that it can be attached accurately at a predetermined position. It has a longer fatigue life than when it is attached to a surface that has been stained, and load detection can be performed with stable accuracy over a long period of time.

It should be noted that the present invention is not limited to the embodiments described and illustrated above, and various modifications can be made without departing from the gist thereof.

For example, the sensing portion is not limited to a cylindrical shape, and may be a prismatic (polygonal prism) shape or an elliptical columnar shape.

The counterbore holes 14 and 15 are not limited to circular holes, but may be elliptical or oblong holes.

Also, strain gauge 5G3a for transverse strain detection.

The adjustment holes 17, 18, 19, 20 drilled near the sides of 5G3b and 5G4a and 5G4b are not limited to circular holes, but may be square holes, elliptical holes, etc., in short.

It is only necessary that the distance between the adjustment holes 17 and 18 and the adjustment holes 19 and 2o be set to appropriate values so that the ratio of longitudinal strain to transverse strain can be adjusted as close to 1 as possible.

Therefore, in this sense, instead of drilling the adjustment holes 17 to 2 degrees, the plate thickness of the strain generating portion 16 may be made to be different.

In other words, since transverse strain is generally smaller than longitudinal strain,
For example, strain gauges 5G1a, 5 for detecting longitudinal strain
From the wall thickness of the part where Glb and 5G2a and 5G2b are attached, strain gauges 5G3a and 5 for transverse strain detection are used.
G3b and 5G4a.

SG4. The thickness of the strain-generating portion 16 at the portion to which b is attached may be made thinner. Further, drilling the adjustment holes 17 to 20 and varying the plate thickness of the strain-generating portion 16 may be used together.

(e) Effects As is clear from the above detailed description, according to the present invention, a large strain output can be obtained, and the load-strain characteristics exhibit good linearity, and are resistant to lateral loads and unbalanced loads. It is almost unaffected by electrical output that accurately corresponds to the load in the axial direction of the load, and it is also easy to attach strain gauges, making it stable over a long period of time without causing deterioration or fatigue failure. Accuracy can be ensured, and in addition, Figures 6 and 7
Compared to the reference example shown in the figure, it is possible to provide a considerably/IX type load transducer.

[Brief explanation of the drawing]

Figures 1 to 3 show the configuration of an embodiment of the load converter according to the present invention, of which Figure 1 is a front view and Figure 2 is a front view.
The figure is a sectional view taken along the line A-A in Figure 1, and Figure 3 is a cross-sectional view of the Figure 1
4 is a circuit diagram showing an example of the load detection wheel 1 to stone bridge circuit configured with strain gauges used in the same embodiment, and FIG. , a front view showing the configuration of a conventional solid columnar type load converter, and FIGS. 6 and 7 are a front view and a side view showing the external configuration of a load converter according to a reference example. 8...Load converter, 9...Load introducing section, 10...Sensing section, 11...
Pedestal part, 12.13... Constriction part (transmission part),
14,. 15...Counterbore hole, 16...Strain generating part, 17-20...Adjustment hole, 21.22...
Side part, 5G1a, 5G1b, 5G2a, 5G2b
- Strain gauges for longitudinal strain detection, 5G3a, 5G3b, 5G4a, 5G4b
- Strain gauge for transverse strain detection, X: Load axis, Y: Axis orthogonal to the load axis. Patent applicant Kyowa Den Ryoshita Co., Ltd.

Claims (2)

[Claims] (1) A load converter in which a load introduction part, a sensing part, and a load support part are successively connected along a load axis, and the load to be measured applied to the load introduction part is converted into an electrical quantity and detected,
forming a transmission section between the sensing section, the load introducing section, and the load supporting section, each having a smaller cross-sectional area perpendicular to the load axis than the sensing section and coaxial with the load axis;
The pair of counterbore holes are formed by drilling a pair of counterbore holes that reach near the load axis along an axial direction perpendicular to the load axis from opposite side surfaces of the columnar sensing section. A strain-generating part is formed between the bottoms of the strain-generating part, and a strain gauge for longitudinal strain detection is attached with the sensitive axis directed in the direction of the load axis of the strain-generating part, and the strain gauge is perpendicular to the load axis of the strain-generating part. A strain gauge for transverse strain detection is attached with the sensitive axis directed in the direction, and the ratio of the amount of strain at the attachment site of the strain gauge for transverse strain detection to the amount of strain at the attachment site of the strain gauge for longitudinal strain detection is determined. The cross-sectional shape of the strain-generating portion is formed such that the strain is greater than or equal to Poisson's ratio, and the strain gauge is configured to convert the magnitude of the load to be measured applied to the load introducing portion into an electrical quantity and detect it. A load converter characterized by: (2) A load converter in which a load introduction part, a sensing part, and a load support part are successively connected along a load axis, and the load to be measured applied to the load introduction part is converted into an electrical quantity and detected,
forming a transmission section between the sensing section, the load introducing section, and the load supporting section, each having a smaller cross-sectional area perpendicular to the load axis than the sensing section and coaxial with the load axis;
The pair of counterbore holes are formed by drilling a pair of counterbore holes that reach near the load axis along an axial direction perpendicular to the load axis from opposite side surfaces of the columnar sensing section. A strain-generating part is formed between the bottoms of the strain-generating part, and a strain gauge for longitudinal strain detection is attached with the sensitive axis directed in the direction of the load axis of the strain-generating part, and the strain gauge is perpendicular to the load axis of the strain-generating part. A strain gauge for transverse strain detection is attached with the sensitive axis directed in the direction, and the strain gauge for transverse strain detection is attached in the vicinity of the side of the attachment portion of the strain gauge for transverse strain detection in the strain generating part. A small-diameter adjustment hole is drilled to adjust the ratio of the strain amount at the portion to the strain amount at the attachment portion of the strain gauge for longitudinal strain detection to be equal to or higher than Poisson's ratio, and the strain gauge is applied to the load introduction portion. A load converter characterized in that it is configured to convert a measured load into an electrical quantity and detect it.