JPS6046424A - Composite load cell - Google Patents

Abstract

PURPOSE:To prevent abnormal deformation from being transmitted from an adjacent body and reduce the output error of a strain gauge by placing a flexible part with specific thickness at the boundary of a composite surface, and forming grooves which allow the composite boundary surface to deform freely across the flexible part. CONSTITUTION:A piercing round hole 12 is formed in the front and rear center surfaces of a strain inducing beam 10 which is fixed at the left terminal 18' and applied with downward force F at the right terminal 18'', and strain gauges 10' and 14'', and 16' and 16'' are installed at four corners of the round hole 12. A cylindrical sheath 20 is inserted into the round hole 12 so as to protect those strain gauges, and sealed by being welded at the front and read openings. In this case, the flexible part 24 having specific thickness is left at the outer circumference of the weld joint part and grooves which allow the flexible part 24 to deform freely are formed at the outer circumference.

Description

DETAILED DESCRIPTION OF THE INVENTION The present invention relates to prevention of errors caused by the influence of adjacent individuals in a strain-generating body formed by integrating individuals with different characteristics.

It is ideal to use an elastic body with uniform properties as a base for the strain-generating body of a load cell, but it is difficult to process a complex stress-concentrating part as a shore body, so it is made as a separate body and composited into a single body. Or, even if it is a single strain-generating body, it may be attached to its base, sealed with a cover for a fixed strain gauge, or attached to a load transmission button, etc., so it can be integrated with different characteristics, such as different coefficients of thermal expansion, hardness, and modulus of elasticity. It is often necessary to combine and integrate metals by press-fitting, welding, screwing, gluing, etc. Because the joints are integrated, permanent stress remains.When a force is applied to a composite strain-generating body, a single material deforms in proportion to its direction, but when a composite body made by joining different materials together, Since the respective characteristics differ at the boundary, the deformation is no longer proportional to the force, and therefore the strain gauge output placed near this boundary is also not proportional to the force to be measured, causing an error. Therefore, in the present invention, a flexible part of a predetermined thickness is placed next to the boundary surface, and a groove containing a gap that allows the composite boundary surface to deform freely is placed between the flexible parts, thereby reducing the resistance of adjacent bodies such as covers. This is to prevent the transmission of abnormal deformation that is not proportional to the force at the composite interface by penetrating the load cell into the strain body through the gap and to the strain gauge bonded to the strain body, thereby preventing output errors of the strain gauge. .

A preferred embodiment of a bending beam load cell will be described below with reference to the drawings.

Figure 1 10 shows a strain beam with a through-hole 12 on the front and rear sides of its center.
and strain gauges 14' at the top and bottom four corners of the round hole.
14', 16' and 16' are placed, the left end 18' of the beam is fixed, and when a downward force F is applied to the right end 18', the round hole is fixed at both ends.
When 8'1B' is a strong solid, 18'18'' remains horizontal and parallel, but the beam has an inflection point at the center and deforms close to a centrally symmetrical parallelogram, so 14'16' is expanded, 14' and 16' are compressed, and the right end 18'' is lowered.

In order to hold the strain gauge in such a bent beam, the strain gauge 14' 1 is pressure-bonded inside the through hole 12 as shown in Fig. 2.
Generally, the cylindrical sleeve 20 is sufficiently smaller in diameter than the through hole 12 and has a longer hole in order to provide a gap at 4'', 16' and 16''.

Generally, the cylindrical sleeve 20 is thin and flexible and has a structure that does not provide resistance to the deformation of the strain beam 10, but since the joint is hardened by welding or gluing, it does not become a strain beam. On the other hand, the resistance is not zero, so if there is a strain gauge nearby, the deformation resistance of the cylindrical sleeve 20 will be detected, resulting in an error.

The present invention provides a flexible section 24 with a predetermined thickness at the interface of the composite to prevent transmission of the resistance of the composite to the strain-generating body.
(shown by the dotted line in Figure 1), and a gap 826 is placed adjacent to it to prevent the deformation of the flexible portion 24 of the composite surface from the gap groove 2.
The purpose of the freeing at 6 is to deform and consume the resistance force of the composite body to prevent force from being transmitted beyond the groove 26 into the strain body 10.

In order to understand and clearly explain the operation of the present invention, the explanation will be given below assuming that the above-mentioned extreme sum sealing cylindrical sleeve 20 is a rigid body and does not deform.

Figure 2a is along the center of the strain gauge 16'16' of the single (uncompounded) load cell of Figure 1: lI -1r
In the cross-sectional view seen from the direction of the arrow, the dotted line shows the position of the flexure element with no load and no displacement (however, the deformation when there is no groove shown by the chain line used in the present invention), and the solid line shows the deformation when force F is applied. The cylindrical cannula 20 inserted into the through hole 12 for strain gauge optometry, which will be explained later, only shows the position before combination, so the deformation of the strain beam is that without the cylindrical cannula 20. shows.

FIG. 2b shows the through-hole 12 of the strain-flexible beam 10 without grooves 26 according to the present invention, which is shown by the dashed lines in FIG. The cylindrical sleeve 20 is caulked to the outer periphery of the side surface and welded at its outer ends 30'30',32'32''.In order to facilitate the explanation of the present invention, the cylindrical sleeve 20 is an immediate body with a high externality ratio and does not deform. strain beam 10
As shown in Figure 0, which shows the deformation of the anus-■ cross section, the cylindrical cannula 20 is a rigid body and does not deform, so the welded parts 30'30'' and 32'32'' of the cannula 20 do not deform. The middle of the cross section becomes concave as shown by the downward solid line due to the load.

However, the lowermost part 25' of the center part does not descend to the deformed position 25 of the inner diameter of the round hole 12 in FIG. If the elasticity is high, there will be an error. In this case, welding joint 30'30'
, 32'32' The flexible part 24t of a predetermined thickness is left on the outer periphery of the flexible part 24, and a groove 26 is placed on the outer periphery of the flexible part 24 to serve as a gap in which the flexible part 24 can freely deform. The deformation of the strained body is shown in FIG. 2C. In FIG. 2C, since the flexible portion 24 is freely deformed even if the cylindrical sleeve 20 is not deformed, the strain beam 10 outside the groove 26 can be freely deformed, and the strain gauge 16' 16
The center with ' is the position 25 in Figure 1a. Cylindrical cannula 2
Since the displacement is not constrained by zero, the strain gauges 16' and 16' display correct outputs.

The cylindrical cannula 20 has been described above as a completely rigid body in FIG. Even though there are differences, the trends are the same,
If there is a deformable groove in the joint as shown in Figure 2C, the force of the composite will not reach outside the groove, and the strain body 10 will deform itself in its own way, that is, deform in proportion to the force. Therefore, the composite part Even if the cylindrical sleeve 20, which is somewhat less flexible, is combined with the strain-generating body, it has a simple structure of just providing a groove to serve as a void near the boundary of the strain gauge. can be done easily and inexpensively.

The above-mentioned grooves do not necessarily have to extend over the entire circumference of the composite surface, but may be limited to a portion adjacent to the strain gauge perpendicular to the direction of strain on the composite surface. In the above explanation, the bending force detection beam was described, but the same applies to the shearing force detection beam.

[Brief explanation of the drawing]

FIG. 1 is a support surface view of a rectangular beam with round holes for detecting bending force. Second
The figure is a cross-sectional view taken in the direction of the arrow along the perpendicular line passing through the center of the pair of upper and lower strain gauges at the right corner of the M light passage hole, and Figure 2a is the state when both ends of the cylindrical sleeve are not joined to the strain body. Fig. 2b shows the state when they are joined to form a composite strain-generating body, and Fig. 2c shows the state after the grooves have been provided in accordance with the present invention. In the figure 10 Strain beam 12 Through round holes 14'14',16'16' Strain gauges 18' at the four corners
18' Left and right ends of the beam 20 Cylindrical mantle 22' Left and right ends of the 22' mantle 24 Flexible portion 25 Displacement position of the inner wall of the through hole 12 due to force F when there is no cylindrical mantle 25' When there is a cylindrical mantle Displacement position of the inner wall of the through hole 12 due to the force F 26 Groove 28 Gap 30'30' Left cylindrical sleeve welding location 32'32'' Right cylindrical sleeve welding location

Claims (1)

[Claims] A composite load cell comprising a load cell strain-generating body integrated by a composite of a plurality of solid bodies, and a groove constituting a gap provided adjacent to the boundary of the composite surface with a removable portion of a predetermined thickness separated.
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