JPS605890B2 - Orthogonal two-component force detection beam with shared shear stress concentration hole - Google Patents

Description

DETAILED DESCRIPTION OF THE INVENTION The present invention concentrates two component forces perpendicular to each other on a hole on one stress concentration section perpendicular to the beam axis, and separately detects the component forces in each direction. This article relates to a compact two-direction force detection method.

To simplify the explanation below, it is assumed that the beam is placed horizontally on the left and right, and the beam axis is the Z direction, the vertical direction perpendicular to Z is Y, and the horizontal front-rear direction perpendicular to the ZY plane is x.

It was common for a beam to be fixed at one end, and the strain caused by the force applied to the other end to be collected and amplified in a reduced section in the middle of the beam, and then detected with a strain gauge.

However, there are two methods: one uses the bending strain of the beam to detect the force and uses it as the bending moment, and the other uses the uneven shear strain and calculates it as the nada shear force.
There was a way. The former bending moment has been mainly used so far because it is easy to detect, while the latter has been rarely used because its detection sensitivity is poor. However, bending strain is often caused when a force is applied in the direction of force, for example in the vertical Y direction, and the strain that occurs is inversely proportional to the thickness of the beam, that is, the dimension h in the Y direction, and is
The problem is the direction in which the cross-sectional area is reduced due to stress concentration, and as the thickness is reduced, distortion occurs in inverse proportion to the square of the thickness. If stress concentration holes are provided to effectively concentrate stress in the Y direction, stress will hardly be concentrated in the is only used to detect force in one direction, and the force must pass through the beam axis and be perpendicular to it; if it deviates from the beam axis, it will be twisted, and if there is a component force other than at right angles, it will cause distortion as described above. Until now, it was unthinkable to use a single stress concentration hole for concentrating forces in multiple directions, as this would cause large errors due to interference. Therefore, up until now, force detection was mainly used based on bending moment, but the same applies to cutting stress.
The holes on the two deep stress concentration cross sections should only be used for concentrating force in one direction, and if they were shared for concentrating force in two directions, there would be a lot of errors, so they were never used. However, when a scale shear force (for example, a force in the Y direction) is applied to a beam, the scale strain is not the bending of adjacent cross sections, but the displacement of the cross sections, and therefore the strain is proportional to the density of force per unit area, that is, the stress. Unlike bending moment strain, it is not the height h in the force direction, but it is inversely proportional to h, and it is also inversely proportional to b, so it is not inversely proportional to bh2, but only inversely proportional to the cross-sectional area, so the shape and direction of the cross-section , that is, the shape direction of the stress concentration hole is irrelevant.

In other words, it is considered that the stress concentration hole in the X direction also functions in the same way in the Y direction, and the force in the Y direction is also concentrated in the same way.
Therefore, it is clear that the stress concentration hole in the By reducing the number of stress concentration holes, the length of the beam can be reduced, and the thickness of the beam required to withstand the force applied by sliding can also be reduced, providing a compact load cell. Preferred embodiments of the present invention will be described below with reference to the drawings.

Figure 1 shows an example in which the present invention is applied to a hexahedral beam surrounded by rectangular surfaces.As explained at the beginning, the beam 10 is placed in the left and right horizontal Z direction, and its center vertical direction is in the Y horizontal front-back direction. x
Then, the plane passing through the center 0 of the beam and including the XY axis perpendicular to the beam axis Z direction is the stress concentration plane, and the line where it intersects with the beam surface is AB.
CD. Assuming that the height of the beam is h, the width b in the front and back -d
)b, and when the component force Fy in the Y direction of the force F applied to the beam acts, the average value 7y of the deep stress in the Y direction is 7y=Fy/b(
h-d), the shear strain yx is proportional to 7y.

To detect this 7y, the stress concentration cross section ABCD intersects with the ABCD plane A on the front and rear vertical side surfaces 14'14'' of the beam.
When cross-gauges such as 16' and 16'' of 450 are provided on the BCD symmetrically with respect to the beam center, the elements 16p, 16
'', (shown in Figure 1) are tension 16'2, 16''2 are under compression, so 16',, 16'', and 16'2, 16
If you create a dragon bridge with ``2'' on the opposite side, the strain gauge will increase the strain and detect it. However, the crossed gauges 16', 16〆2 and 16''
,,16″2 means 1 on one side of the hole 12 without crossing over.
6′, 16′2 and 16″, 16″2 can be separated and glued centrally symmetrically above and below the hole 12 by dividing the cross gauge into two and forming four sets of layers above and below the hole 12. is also free. Furthermore, the average stress value 7x due to the component force Fx of F in the X direction is the value obtained by substituting Fx in place of Fy in the above equation, and the breaking strain yx is proportional to 7x.

Although the proportionality constants of yx and yy differ somewhat depending on the direction of the hole, as described above, they are not as affected by the direction of the hole as the bending strain, and therefore there is little mutual interference between strains in different directions. To detect the strain yx in the
A pair of cross strain gauges 20', 20'2 and 20 that intersect 5o
'', 20''2 (see Figure 1), y. can be detected. Also each crossover gauge is 16k, 16
'2, 16'', 16''2 detects only the force in the AB and CD directions, that is, the vertical direction, and does not detect the force in the horizontal direction Fx because it is perpendicular to the gauge surface, but only detects Fy regardless of Fx, and the gauge 20 Similarly, since it detects only Fx, it is optimal for orthogonal component force detection.

However, when there is a component force Fz in the Z direction, each cross gauge 16'
, 16'2, 16'', 16''2, the sea bream cutting force is applied on the horizontal plane passing through the center of the intersection, so the intersection gauge is Fy and F on the same aircraft.
z will also be detected. However, there is a force application part at the end of the beam in the direction of Fz, and the cross-sectional area in the Z-axis direction is significantly larger than the cross-sectional area ABCD including the x and Y-axes, and the contraction of the cross-sectional area in the Z direction is small in the direction of the stress concentration hole 12. So crossover gauge 16
′, 16′2, 16″, 16″2 has little stress concentration F
z is not detected, i.e. the cross gauge on the vertical plane detects only the vertical force, and the upper and lower cross gauges also detect the X perpendicular to the beam axis.
Only direction Fx is detected. In the above example, the stress concentration hole 12 was a hole that penetrated the beam axis in the Either divide the stress concentration hole 12 into two halves by leaving a vertical bottom wall 30 orthogonal to the rattan in the middle of the stress concentration hole 12, as shown in Figure 2, and make two flat-bottomed holes along the x axis. It is also possible to provide cross strain gauges of 16' and 16'' on the bottom surface 30' and 30'', respectively. In this case, the cross strain gauges 16 and 16 for Fx and Fy will cause a difference in sensitivity depending on the direction of the hole bottom 30. The difference is slight and can be easily adjusted by increasing the gauge output.

Previously, stress concentration holes were provided separately in each direction in a fixed relationship with the direction of force, but shear force detection is now based primarily on the area and axial length of the stress concentration cross section, regardless of the direction or shape of the hole. By combining the fact that the cross-gauge only detects force in the direction of the central axis of the gauge, the hole on one stress concentration cross section can be used in common for stress concentration in multiple directions, which is not necessary until now. By reducing the number of stress concentration holes, the length of the beam can be reduced, and the thickness of the beam, which is proportional to the length, can be reduced in order to make the beam capable of withstanding the force to be detected. The industrial effect of providing a compact force detector is significant.

In the above example, the stress concentration hole is shown as a round hole in the drawing because it is simple, but as explained repeatedly, the shape of the stress concentration hole has little effect on scale shear force detection, so the shape of the hole can be freely chosen as long as it is symmetrical about the center. It is. Also, although the holes were placed in the x direction and the gauges were arranged accordingly, it is also possible to place them in the y direction. In addition, although the stress concentration section was set at the center of the beam, the location does not matter as long as it is perpendicular to the beam axis. Further, although only an example in which the cross gauge is bonded to the outer surface of the beam is shown, it is also possible to bond it to the inner surface of the stress concentration hole in a structure that allows it to be bonded.

BRIEF DESCRIPTION OF THE DRAWINGS FIG. 1 is a perspective view of a two-way stress detector using one stress concentration hole. FIG. 2 shows a perspective view of an example in which a vertical bottom is placed in the center of the stress concentration hole for the same purpose. In the figure, 10...beams,
12...Stress concentration hole, 14'14''...Vertical front and rear surfaces of the beam, 16...Cross gauge, 16', 16''...Cross gauge on front and rear surfaces, 16', 16'2...Cross of 16' Gauge elements intersecting ,6〃,16''2...16''18'18''...Horizontal top and bottom surfaces of beams, 20'20''
...Cross gauge on top and bottom surface, 20', 20'2...
...・20' crossed gauge element, 20'', 20''2...
...20" crossed gauge element, 30'30"...
...Bottom wall placed in the middle of the stress concentration hole. Figure U1 Figure 62

Claims (1)

[Claims] 1. A through hole parallel to the center of a set of two parallel lines of intersection between a predetermined stress concentration cross section perpendicular to the axis of a beam having a rectangular cross section and the plane of the beam, or Two flat-bottomed blind holes divided into two halves are provided, and a pair of shear force detection cross-strain gauge elements that intersect at 45 degrees are placed on each line of intersection between the stress concentration cross section and the surface of the beam. An orthogonal two-component force detection beam for common use with shear stress concentration holes, characterized in that the stress concentration cross section is reduced by the holes to form a common shear stress concentration surface for two component forces perpendicular to the axis. 2. A shared orthogonal shear stress concentration hole according to claim 1, characterized in that the sensitivity is adjusted by dividing or doubling each set of shear force detection cross strain gauge elements placed in symmetrical relation to the axis. Two-component force detection beam.