JPH0933366A - Load cell and load cell balance - Google Patents

Abstract

PROBLEM TO BE SOLVED: To make the improvement of nonlinearity by offset load and the assembling working property such as installation of a strain gauge compatible. SOLUTION: Using paired first and second distorting bodies 12, 13 having quasi-Roberval mechanism, a load cell structure 14 formed into substantially U-shape by connecting a fixed support part 23 to a movable support part 18 within the horizontal plane is constituted as a base, thereby, the state where contrary stresses of tension and compression are generated in the first and second distorting bodies 12, 13, even if a moment by offset load acts thereon, is formed, so that the same canceling function of a bad effect by offset load as in the case where strain gauges are installed to distorting parts in four upper and lower positions of a single distorting body is ensured only in one surface of the upper surface (or lower surface) of the load cell structure 14, strain gauges R11 , R12-41 , R42 are arranged on distorting parts 20a, 20b, 26a, 26b in four positions of one surface of the upper surface (or lower surface) of the load cell structure 14, and the sum of strain outputs of the strain gauges R11 , R12-41 , R42 is outputted by a bridge arithmetic circuit.

Description

Detailed Description of the Invention

[0001]

TECHNICAL FIELD The present invention relates to a load cell and a load cell balance.

[0002]

2. Description of the Related Art At present, load cell scales that utilize strain gauges to output the weight of an article as electrical data are widely used in commercial or industrial applications.

An example of such a load cell balance is shown in FIG. This load cell scale is configured based on a rectangular strain element 1 that converts a load into a strain amount. That is, the flexure element 1 has a fixed support portion 4 and a movable support portion 5 which are integrally connected by a pair of vertically opposed beams 2 and 3 at both ends, and these beams 2 and 3 are provided. Of the pseudo-Roberval mechanism having strain-flexing portions 7a to 7d formed by thin semi-circular thin-walled notches 6 at four locations which are vertically symmetrical. The fixed support portion 4 of the strain body 1 is a main body base 8 of the balance main body.
A weighing pan 9 is connected to a movable support portion 5 which is fixed to a part of the above and is supported by a cantilever and receives an actual load.

Here, the upper surface of the flexure element 1 (the outer surface of the beam 2)
A total of four strain gauges r ₁₁ , r ₁₂ , r ₂₁ , r ₂₂ are attached to each of the two strain generating portions 7 a, 7 b on the side in pairs in the strain body width direction. These strain gauges r ₁₁ , r ₁₂ , r ₂₁ , r
₂₂ is a pair of strain gauges r ₁₁ , r ₁₂ , strain gauges r ₂₁ , r ₂₂
Are connected adjacent to each other to form a bridge circuit.

With such a configuration, when the load of the article mounted on the weighing pan 9 is applied to the strain-flexing body 1 through the movable supporting portion 5, the strain-flexing portions 7a to 7d are deformed so as to be stretched or compressed according to the load. By generating, the load is converted into the amount of strain. Here, the strain generating portions 7a, deformation in 7b causes electrical resistance change of the strain gauge _{r 11, r 12, r 21} , r 22. Therefore, these strain gauges r ₁₁ , r ₁₂ , r ₂₁ , r
Weighing is performed by taking out the change in resistance value of _{22 as} a voltage signal by the bridge circuit.

In the case of the load cell balance shown in FIG. 15, the strain gauges r ₁₁ , r ₁₂ , r ₂₁ , r ₂₂ and the wiring (lead wire) for the bridge circuit are beamed as a thin film by a thin film technique such as a sputtering method. It can be formed integrally on two surfaces and is easy to manufacture. This is the strain-flexing parts 7a, 7b.
Instead of the side, the strain-flexing portions 7c and 7d side outer surface (the lower surface of the beam 3)
The same applies when forming two pairs of strain gauges.

[0007]

However, according to the load cell balance shown in FIG. 15, when an eccentric load is applied to the flexure element 1, it is affected by the moment due to the eccentric load and is obtained from the bridge circuit. There is a problem that the linearity of the output deteriorates.

This point will be described in detail with reference to FIGS. 15 and 16. Note that FIG. 16 is a schematic diagram showing the amount of strain at each of the strain gauges r ₁₁ , r ₁₂ , r ₂₁ , r ₂₂ with respect to the load change. In FIG. 16, T _S is a tensile stress in the shear mode, C _S is a compressive stress in the shear mode, T _M is a tensile stress based on a moment due to an unbalanced load,
C _M indicates a compressive stress based on the moment due to the unbalanced load.

First, a load position a, which is the stress center of the flexure element 1,
When a load is applied to the strain gauge r
Shear mode tension is generated in ₁₁ and r _12, and shear mode compression is generated in the strain gauges r ₂₁ and r ₂₂ of the strain-flexing portion 7b, but a moment due to an unbalanced load is not generated. Therefore, the amount of strain with respect to changes in load exhibits linearity.

However, the load position b deviated from the stress center
When a load is applied to the strain generating portions 7a and 7b, a tensile stress and a compressive stress are generated on the basis of the moment due to the unbalanced load. Therefore, as shown in the characteristic of the load position b in FIG. 16, the strain amount with respect to the load change in each of the strain gauges r ₁₁ , r ₁₂ , r ₂₁ , and r ₂₂ shows non-linearity. As a result, the output value of the bridge circuit that obtains the combined output of the strain gauges r ₁₁ , r ₁₂ , r ₂₁ , and r ₂₂ also shows non-linearity, and the unbalanced load causes an adverse effect. This is because even when a load is applied to the load position c deviated from the stress center in the opposite direction, the same phenomenon is exhibited only by the deformation direction (changes from the lower bulge to the upper bulge), so that the unbalanced load adversely affects Comes out (Fig. 16
Refer to the characteristics of the load position c inside).

In this respect, the strain-flexing body 1 is originally formed as a pseudo-Roberval mechanism for canceling an eccentric load error. For example, strain gauges are attached to the respective strain-flexing portions 7a to 7d formed at four upper and lower positions, It is conventionally known that the influence of a moment due to an unbalanced load is canceled by extracting the resistance value change of these strain gauges as a voltage signal through a bridge circuit.

However, when a strain gauge is attached to each of the strain-flexing parts 7a to 7d, it is necessary to attach the strain gauges to both upper and lower surfaces of the strain-generating element 1 and lead between the upper and lower surfaces of the strain-generating element 1 is obtained. Since it is necessary to connect the wires to form a bridge circuit, assembly and workability are poor. Therefore, as described above, it is impossible to integrally form the strain gauge and the wiring for the bridge circuit by the thin film by using the thin film technology.

Therefore, the improvement of the non-linearity due to the unbalanced load and the assembling / workability are not compatible at present.

[0014]

A load cell and a load cell balance according to the present invention use a pair of first and second flexure elements having a pseudo-Roberval mechanism, and a movable support portion of the first flexure element. The fixed support part of the second flexure element is connected in a horizontal plane to form a U-shaped load cell structure as a base, and the fixed support part of the first flexure element is fixed to the main body base. When a weighing tray is connected to the movable support portion of the second flexure element and a load is applied, even if a moment due to an unbalanced load acts, the first flexure element side and the second flexure element side do not Opposing stresses of tension and compression are generated. That is, the adverse effect caused by the moment due to the unbalanced load similar to the case where the strain gauges are attached to the upper and lower four strain generating portions of one strain generating body on only one of the upper surface and the lower surface of the load cell structure is adversely affected. The function of offsetting is obtained. Therefore, strain gauges are arranged at four strain generating portions on either one of the upper surface and the lower surface of the load cell structure, these strain gauges are electrically connected, and the strain of these strain gauges is corrected by the bridge arithmetic circuit. By outputting the sum of the outputs, the non-linearity of the output characteristics based on the moment due to the unbalanced load is improved by canceling the contradictory stresses on the first flexure body side and the second flexure body side,
Since the amount of strain with respect to load changes becomes linear and wiring processing for strain gauges and bridge circuits is completed on one side, assembly and workability are also improved.

In particular, in a load cell balance, strain gauges are arranged in pairs at each of four strain generating portions in the strain generating element width direction to form a bridge circuit for each strain generating element, and the outputs of these bridge circuits are formed. By using the sum of the strain output as the sum of the strain output, it is possible to obtain a virtually double output result for the same load, making it possible to improve the non-linearity due to the unbalanced load and the assembly / workability at the same time. At the same time, the weighing accuracy is improved. In addition, by disposing one strain gauge for each of the four strain generating portions, forming one bridge circuit between the two strain generating bodies, and setting the output value of this bridge circuit as the total strain output. With a simpler structure, improvement of non-linearity due to eccentric load and assembly / workability are compatible.

[0016]

FIG. 1 shows a first embodiment of the present invention.
This will be described with reference to FIG. The load cell balance 11 shown in the present embodiment is configured by using a load cell based on a load cell structure 14 in which a pair of flexure elements 12 and 13 are combined.

First, the flexure element 12, which is the first flexure element, is
It is of a rectangular shape having a fixed support portion 17 and a movable support portion 18 which are integrally connected by a pair of vertically facing beams 15 and 16 at both ends, and these beams 15 and 16 are vertically symmetrical. This is a pseudo-roberval mechanism having strain-flexing portions 20a to 20d formed by four semicircular arc-shaped thin notches 19 at four locations. Strain element 1 as the second strain element
3 is also the same, and a pair of vertically facing beams 21, 2
It has a rectangular shape having a fixed support portion 23 and a movable support portion 24, which are integrally connected by two, at both ends, and thin semi-circular cutout portions at four positions which are vertically symmetrical with respect to these beams 21 and 22. Strain-flexing portions 26a to 26d formed by
(In the drawing, only 26a and 26b are shown) of the pseudo-Roberval mechanism.

These flexure elements 12 and 13 are for converting a load into a strain amount, and are made of duralumin or a stainless material. Here, the flexures 12, 13
Is integrally formed so that the movable support portion 18 of the flexure element 12 and the fixed support portion 23 of the flexure element 13 are connected next to each other in a horizontal plane, thereby forming a substantially U-shape in plan view. The eggplant load cell structure 14 is configured. That is, the upper surfaces of the beams 15 and 21 are formed flush with each other, and the lower surfaces of the beams 16 and 22 are also formed flush with each other.

In such a load cell structure 14, the fixed supporting portion 17 of the strain-flexing body 12 is fixed to a part of the main body base 27 of the balance main body, and the movable supporting portion 24 of the strain-flexing body 13 receives an actual load. A weighing pan 28 is connected to the.

Further, four strain-generating portions 2 are formed on the upper surface of the load cell structure 14 (the upper surfaces of the beams 15 and 21).
The strain gauges R ₁₁ , R ₁₂ , R ₂₁ , R ₂₂ , R ₂₂ , which are paired in the strain element width direction, are arranged at 0a, 20b, 26a, and 26b.
₃₁ , R ₃₂ , R ₄₁ , and R ₄₂ are attached. These strain gauges R _{11 to} R ₄₂ are provided with the strain generating portions 20 a, 20 b, 26.
The electric resistance changes according to the amount of strain generated in a and b. These strain gauges R _{11 to} R ₄₂ form a bridge arithmetic circuit 30 by appropriately connecting with lead wires 29 on the upper surface of the load cell structure 14, and the sum of strain outputs of all the strain gauges R _{11 to} R _42. Is configured to be obtained. 31 is an input terminal portion formed at the end of the beam 15;
32 is an output terminal section.

The bridge arithmetic circuit 30 includes a strain-generating element 12
The first bridge circuit 33 formed by the four strain gauges R ₁₁ , R ₁₂ , R ₂₁ , and R ₂₂ on the side, and the four strain gauges R ₃₁ , R ₃₂ , R ₄₁ , and R ₄₂ on the strain body 13 side. And a second bridge circuit 34 formed by. Here, the first bridge circuit 33 is formed by connecting paired strain gauges R ₁₁ , R ₁₂ and strain gauges R ₂₁ , R ₂₂ so as to be adjacent to each other as shown in FIG. Power supply 35 through 31
It is connected to the. The same applies to the second bridge circuit 34 side, and as shown in FIG. 3, a pair of strain gauges R ₃₁ , R ₃₂ ,
The strain gauges R ₄₁ and R ₄₂ are connected and formed so as to be adjacent to each other, and are connected to the power supply 35 via the input terminal portion 31. Output terminal section 3 of these bridge circuits 33, 34
The output obtained in 2 is input to an arithmetic unit 36 including an adder, and the arithmetic unit 36 is configured to obtain an output as the load cell balance 11.

These strain gauges R _{11 to} R ₄₂ are of a general adhesive type and each strain generating portion 20 a, 20 b, 26 a, 2 is formed.
A general coated copper wire that does not affect the stress may be used as the lead wire 29 that is mounted on the 6b and forms the bridge circuits 33 and 34, or a flexible wiring board having flexibility may be used. , Here these strain gauges R
_{All of 11 to} R ₄₂ and the lead wire 29 need only be processed on the same plane, and are therefore formed using thin film technology. Namely, a sputtering method, using a thin film technique deposition method, a strain gauge R ₁₁ to R ₄₂ and the lead wire 29 previously formed as a thin film layer, the strain gauge R ₁₁ to R ₄₂ and the lead wire 29 by selective etching Each is formed integrally by etching into a desired pattern. At this time, the bridge circuit 3
A correction resistor may be included for 3, 34.

In such a configuration, the load cell balance 1
1 is a pair of flexure elements 12 and 1 having a pseudo-Roberval mechanism
Load cell structure 14 in which 3 is integrated into a substantially U shape
Therefore, even if a moment due to an unbalanced load is applied, tensions and compressions which are opposite to each other are generated between the strain generating body 12 side and the strain generating body 13, so that the first bridge The output of the circuit 33 and the output of the second bridge circuit 34 each show non-linearity.
When the output of 34 is added by the adder in the arithmetic unit 36,
The non-linearities of the respective outputs cancel each other out, and as a result, the final output obtained from the calculator 36 exhibits a linearity that is not affected by the unbalanced load. That is, the strain generating portions 20a and 20b of the strain generating body 12 and the strain generating portions 26a and 26 of the strain generating body 13
When strain gauges are attached at four positions b and b, the effect of canceling the unbalanced load equivalent to the case where strain gauges are attached at the upper and lower four strain generating portions of a single strain generating body is obtained.

Here, the principle by which the load cell balance 11 improves the non-linearity under an eccentric load will be described in detail. First,
Consider a case where a load is applied to a load position A corresponding to the center of stress at the center position between the strain generating portions 20a and 20b of the strain generating body 12 and the center position between the strain generating portions 26a and 26b of the strain generating body 13. . In this case, tensile stress due to the shear mode is generated in the strain gauges R ₁₁ and R _{12 of} the strain generating portion 20a and the strain gauges R ₄₁ and R ₄₂ of the strain generating portion 26b.
Strain gauges R ₂₁ and R _{22 of} 0b and strain gauge R of the strain-flexing portion 26a.
A compressive stress due to shear mode is generated in ₃₁ and R ₃₂ , but a moment due to an unbalanced load is not generated. The strain amount with respect to the tensile and compressive stress in the shear mode shows linearity with respect to the change of the load. Therefore, the bridge circuit 3
The outputs of 3, 34 both show linearity, and the added value of the outputs of these bridge circuits 33, 34 in the arithmetic unit 36 also shows linearity.

FIG. 5 shows the strain amounts of the strain gauges R ₁₁ , R ₂₁ , R ₃₁ , and R ₄₁ at the respective strain generating portions 20a, 20b, 26a, and 26b when the load is changed at the load position A. The results of analysis by converting to (strain gauges R ₁₂ , R ₂₂ , R ₃₂ , and R ₄₂ also show the same characteristics). The horizontal axis represents the load amount and the vertical axis represents the positive and negative strain amounts. In this case, as described above, all strain generating units 20
strain gauges R ₁₁ , R at a, 20b, 26a, 26b
₂₁ , R ₃₁ and R ₄₁ show linearity with respect to changes in load.

Next, consider the case where a load is applied to the load position B deviated from the stress center. In this case, a moment stress is generated due to an unbalanced load, a tensile stress is generated on the upper surface of the flexure element 12, and a compressive stress is generated on the upper surface of the flexure element 13. Further, as in the case where the stress is applied to the stress center, tensile stress due to the shear mode is generated in the strain gauges R ₁₁ and R _{12 of} the strain generating section 20a and the strain gauges R ₄₁ and R ₄₂ of the strain generating section 26b, and conversely. A compressive stress due to the shear mode is generated in the strain gauges R ₂₁ and R _{22 of} the strain generating portion 20b and the strain gauges R ₃₁ and R ₃₂ of the strain generating portion 26a. Therefore, when these are combined, the strain gauges R ₁₁ and R ₁₂ of the strain-flexing portion 20 a generate a strain that is a combination of the tensile stress due to the shear mode and the tensile stress due to the unbalanced load, and the strain-generating portion 2
The strain gauges R ₂₁ and R ₂₂ of 0b generate a strain that is a combination of the compressive stress due to the shear mode and the tensile stress due to the unbalanced load, and the strain gauges R ₃₁ and R ₃₂ of the strain-flexing portion 26a have the tensile stress due to the shear mode. A strain that is a combination of the stress and the compressive stress due to the eccentric load is generated, and a strain that is a combination of the compressive stress due to the shear mode and the compressive stress due to the eccentric load is generated at the strain gauges R ₄₁ and R ₄₂ of the strain-flexing portion 26b. To do.

In FIG. 6, the strain amounts of the strain gauges R ₁₁ , R ₂₁ , R ₃₁ , R ₄₁ at the respective strain generating portions 20a, 20b, 26a, 26b when the load is changed at the load position B are weighted. The results of analysis by converting to (strain gauge R ₁₂ , R ₂₂ , R
₃₂ and R ₄₂ also show the same characteristics). Each strain gauge R ₁₁ , R ₂₁ ,
The strain amount with respect to the load change of R ₃₁ and R ₄₁ shows individual non-linearity as shown in the figure. First, the strain gauges R ₁₁ and R ₂₁ on the strain-generating body 12 both show non-linearity of upward swelling with respect to the amount of strain with respect to a change in the load, and the strain gauges R ₁₁ and R ₂₁ formed on the strain-generating body 12 side are the first
Similarly, the output of the bridge circuit 33 of No. 2 also exhibits upward non-linearity. On the other hand, the strain gauges R ₃₁ and R ₄₁ on the strain-generating body 13 both show non-linearity of downward bulge in the strain amount with respect to the change of the load, and the strain gauges R ₃₁ and R ₄₁ of the second bridge circuit 34 formed on the strain-generating body 13 side. The output also exhibits a non-linear bulge. However, when the outputs of the first and second bridge circuits 33 and 34 are added by the adder in the arithmetic unit 36, the nonlinearities of the two cancel each other out, and the final output is the same as when the stress center is loaded. It will show similar linearity.

Further, consider a case where a load is applied to a load position C deviated from the stress center in the opposite direction. In this case, a moment stress is generated due to an eccentric load in the opposite direction to the case of the load position B, and the compressive stress and strain element 1 are generated on the upper surface of the strain element 12.
A tensile stress is generated on the upper surface of 3. Further, similarly to the case where the stress is applied to the stress center, the strain gauges R ₁₁ , R of the strain-flexing portion 20a are
₁₂ , tensile stress due to shear mode is generated in the strain gauges R ₄₁ and R ₄₂ of the strain generating portion 26b, and conversely, the strain gauges R ₂₁ and R _{22 of} the strain generating portion 20b, and the strain gauge R ₃₁ of the strain generating portion 26a, A compressive stress due to shear mode is generated in R ₃₂ . Therefore, when these are combined, the strain gauges R ₁₁ , R ₁₂ of the strain-flexing part 20a are
In the strain gauges R ₂₁ and R ₂₂ of the strain generating part 20 b, the compressive stress due to the shear mode and the compressive stress due to the unbalanced load are generated. The combined strain is generated, and the strain generating portion 26a
Strain gauges R ₃₁ and R ₃₂ generate a strain that is a combination of the tensile stress due to the shear mode and the tensile stress due to an unbalanced load, and the strain gauges R ₄₁ and R ₄₂ of the strain-flexing portion 26 b have compressive stress due to the shear mode. A strain is generated by the combination of the tensile stress due to the unbalanced load and the tensile stress.

In FIG. 7, the strain amounts of the strain gauges R ₁₁ , R ₂₁ , R ₃₁ , and R ₄₁ at the respective strain generating portions 20a, 20b, 26a, and 26b when the load is changed at the load position C are weighted. The results of analysis by converting to () are shown in accordance with FIGS. 5 and 6 (strain gauges R ₁₂ , R
₂₂ , R ₃₂ and R ₄₂ also show the same characteristics). Each strain gauge R ₁₁ ,
The strain amounts with respect to load changes of R ₂₁ , R ₃₁ , and R ₄₁ show individual non-linearity as shown in the figure. First, the strain gauges R ₁₁ and R ₂₁ on the flexure element 12 both show a downward bulging non-linearity in the amount of strain with respect to a change in the load, and the strain gauges R ₁₁ and R ₂₁ of the first bridge circuit 33 formed on the flexure body 12 side. The output also exhibits a non-linear bulge. On the other hand, strain gauges R ₃₁ , R on the flexure element 13
Reference numeral ₄₁ shows the non-linearity of upward swelling with respect to both changes in load, and the output of the second bridge circuit 34 formed on the side of the flexure element 13 also shows non-linearity of upward swelling.
However, when the outputs of the first and second bridge circuits 33 and 34 are added by the adder in the arithmetic unit 36, the nonlinearities of the two cancel each other out, and the final output obtained from the arithmetic unit 36 is stressed. It will show the same linearity as when loaded in the center.

Therefore, the load position A,
If the above-mentioned characteristics of the amount of strain in the strain gauges of the respective parts when loads are respectively applied in B and C are collectively illustrated, it can be represented as shown in FIG. In FIG. 8, T _S is tensile stress due to shear mode, C _S is compressive stress due to shear mode, T _M is tensile stress due to moment due to unbalanced load, and C _M is compressive stress due to moment due to unbalanced load.

That is, when the load position A is the stress center, the moment stresses T _M and C _M due to the eccentric load do not occur, only the stresses T _S and C _S due to the shear mode, and each strain gauge R
_{11 to} R ₄₂ show the linearity of the strain amount with respect to the load change, and the respective outputs of the first and second bridge circuits 33 and 34 and the addition output also show the linearity. On the other hand, at the load positions B and C, moment stresses T _M and C _M due to unbalanced loads occur,
Non-linearity with (T _S + T _M ), slightly upward bulge characteristic, (C _S + T _M ) with large upward bulge characteristic, (C _S + C _M ) with slightly downward bulge characteristic, and (T _S + C _M ) with large downward bulge characteristic Shows sex. In the case of the load position B, the output of the first bridge circuit 33 on the side of the strain generating body 12 swells upward, and the output of the second bridge circuit 34 on the side of the strain generating body 13 bulges downward, which is non-linear. However, the added value of the outputs of the bridge circuits 33 and 34 by the calculator 36 shows linearity. The load position C is similar to the load position B except that the direction of non-linearity is different. In this way, in the case of the load cell balance 11, it is apparently not affected by the unbalanced load under the condition that the strain gauge or the like can be formed on the same surface and the assembling / workability can be improved, Non-linearity due to eccentric load is improved.

Particularly, in this load cell balance 11,
The strain gauges R _{11 to} R ₄₂ are provided at the four strain generating portions 20a, 20b,
26a and 26b are arranged in pairs in the width direction of the flexure element, and bridge circuits 33 and 34 are formed for each of the flexure elements 12 and 13. The added value of the outputs of these bridge circuits 33 and 34 is distorted and output. Therefore, each bridge circuit 33,
In 34, substantially double the output result is obtained for the same load, and the weighing accuracy is further improved.

The strain-generating parts 20a, 20b, 26a, 2
6b instead of 6b, which is the lower surface side of the load cell structure 14
Strain gauges may be attached to the strain-flexing portions 20c, 20d, 26c, 26d at the locations.

Further, the load cell structure 14 is not limited to the one in which the pair of flexure elements 12 and 13 are integrally formed and connected to each other. For example, as shown in FIG. 9, the movable support portion 18 of the flexure element 12 is provided. A spacer 37 is interposed between the fixing member 23 and the fixed supporting portion 23 of the flexure body 13 and is connected by a screw 38 or the like, so that a load cell structure 39 having a substantially U-shape in plan view is configured. Good.

A second embodiment of the present invention will be described with reference to FIGS. Portions having the same functions as those shown in FIGS. 1 to 9 are denoted by the same reference numerals, and description thereof will be omitted. Load cell balance 41 shown in the present embodiment
Is configured by using a load cell based on the same load cell structure 14 as in the case of the load cell balance 11 described above, but the configuration of the bridge arithmetic circuit including the strain gauge is different.

First, on the upper surface of the load cell structure 14, strain gauges R ₁ , R ₂ , R ₃ and R ₄ are attached to the _four strain generating portions 20a, 20b, 26a and 26b, respectively. These four strain gauges R _{1 to} R ₄ form a bridge circuit 42 forming a bridge arithmetic circuit by appropriately connecting the lead wires 29 on the upper surface of the load cell structure 14, and the output value of the bridge circuit 42 is It is configured to be the sum of the strain outputs of all strain gauges R _{1 to} R ₄ . That is, only one bridge circuit 42 is formed across the flexure elements 12 and 13.

Here, as shown in FIG. 13, the bridge circuit 42 includes strain gauges in the same flexure element 12 and 13,
That is, the strain gauges R ₁ and R ₂ are adjacent to each other, and the strain gauges R ₃ and R ₄ are adjacent to each other, and the strain gauges R on the side of the fixed support portions 17 and 23.
₁ and R ₃ , strain gauges R ₂ and R on the movable supporting portions 18 and 24 side
₄ are connected to each other so that they are located on opposite sides, respectively. The input terminal portion 31 of the bridge circuit 42 is connected to the power supply 35. The output side of the bridge circuit 42 is connected to a computing unit 43 that outputs the output of the load cell balance 41. This calculator 43 does not need an adder.

In the case of these strain gauges R _{1 to} R ₄ as well, the strain generating portions 20a, 20b, 2 are of the general adhesive type.
A general coated copper wire that does not affect the stress may be used as the lead wire 29 that is mounted on the wires 6a and 26b and forms the bridge circuit 42, or a flexible wiring board having flexibility may be used. Here, since all of these strain gauges R _{1 to} R ₄ and the lead wire 29 need only be processed on the same plane, they are formed using the thin film technique.

In such a configuration, the load cell balance 4
1 is a pair of flexure elements 12 and 1 having a pseudo-Roberval mechanism
Load cell structure 14 in which 3 is integrated into a substantially U shape
Basically, even if a moment due to an eccentric load acts, tensions and compressions in opposite directions are generated between the strain element 12 side and the strain element 13, and the strain elements 12, 13 Since the non-linearities shown on the side are also contradictory, the outputs of the bridge circuit 42, which are the combined output of the two, cancel each other out, and as a result, the linearity is not affected by the unbalanced load. That is, the flexure portions 20a, 20b of the flexure body 12
When strain gauges are mounted at four places, namely, the strain generating parts 26a and 26b of the strain generating body 13, a strain gauge equivalent to the case where the strain gauges are mounted at four upper and lower strain generating parts of a single strain generating body. The effect of canceling the load is obtained.

Here, the principle by which the load cell balance 41 improves the non-linearity under an eccentric load will be described in detail. First,
Consider a case where a load is applied to the load position A corresponding to the stress center. In this case, tensile stress due to shear mode occurs in the strain gauges R ₁ and R ₄ of the strain-flexing portions 20a and 26b,
On the contrary, compressive stress due to shear mode occurs in the strain gauges R ₂ and R ₃ of the strain-flexing portions 20b and 26a, but no moment due to eccentric load occurs. The strain amount with respect to the tensile and compressive stress in the shear mode shows linearity with respect to the change of the load. Therefore, the output of the bridge circuit 42 or the output obtained from the calculator 43 exhibits linearity. The analysis result is the same as that shown in FIG.

Next, consider the case where a load is applied to the load position B deviated from the stress center. In this case, a moment stress is generated due to an unbalanced load, a tensile stress is generated on the upper surface of the flexure element 12, and a compressive stress is generated on the upper surface of the flexure element 13. Further, similarly to the case where the strain is applied to the stress center,
A tensile stress due to shear mode is generated in the strain gauges R ₁ and R ₄ of b, and conversely, the strain gauges R of the strain generating portions 20 b and 26 a are
₂ and R ₃ generate compressive stress due to shear mode.
Therefore, when these are combined, the strain gauge R ₁ of the strain-flexing portion 20 a generates a strain that is a combination of the tensile stress due to the shear mode and the tensile stress due to the unbalanced load, and the strain gauge R ₂ of the strain-generating portion 20 b is at the strain gauge R ₂ . The combined strain of the compressive stress due to the shear mode and the tensile stress due to the eccentric load causes a strain, and the strain gauge R ₃ of the strain-flexing portion 26a has a strain resulting from the combination of the tensile stress due to the shear mode and the compressive stress due to the eccentric load. Occurs, and the strain generating portion 26
In the strain gauge R _{4 of} b, a strain that is a combination of the compressive stress due to the shear mode and the compressive stress due to the unbalanced load is generated.

Therefore, when the load is changed at the load position B, the strain amount of the strain gauges R ₁ , R ₂ , R ₃ , and R ₄ at the respective strain generating portions 20a, 20b, 26a, and 26b is weighted. The results of conversion and analysis are the same as those shown in FIG. 6, and the strain amount with respect to the load change of each strain gauge R ₁ , R ₂ , R ₃ , R ₄ shows individual non-linearity. That is, referring to FIG. 6, the strain gauges R ₁ and R ₂ on the flexure element 12 both show upward swelling nonlinearity in the amount of strain with respect to a change in load, and the strain on the flexure element 13 is increased. The gauges R ₃ and R ₄ both show a downward bulging non-linearity in the amount of strain with respect to a change in load. However, considering the sum of the strain amounts of these strain gauges R _{1 to} R ₄ as the combined output, the output of the bridge circuit 42 or the computing unit 43 cancels the nonlinearity of the upward bulge and the nonlinearity of the downward bulge. Together, the combined output shows the same linearity as when the stress center is loaded.

Further, consider a case where a load is applied to a load position C deviated from the stress center in the opposite direction. In this case, a moment stress is generated due to an eccentric load in the opposite direction to the case of the load position B, and the compressive stress and strain element 1 are generated on the upper surface of the strain element 12.
A tensile stress is generated on the upper surface of 3. Further, as in the case where the stress is applied to the stress center, tensile stress due to shear mode is generated in the strain gauges R ₁ and R ₄ of the strain-flexing portions 20a and 26b,
Conversely, compressive stress due to shear mode is generated in the strain gauges R ₂ and R ₃ of the strain-flexing portions 20b and 26a. Therefore, when these are combined, the strain gauge R ₁ of the strain-flexing part 20a is
In the strain gauge R ₂ of the strain-flexing portion 20 b, the compressive stress due to the shear mode and the compressive stress due to the unbalanced load are combined. distortion occurs, the strain generating portions 26a strain gauges R _3, the strain tensile stress and the tensile by unbalanced load stress is synthesized is generated by Shieamodo, the strain gauges R ₄ of the strain generating unit 26b, Shieamodo A strain is generated by the combination of the compressive stress due to the stress and the tensile stress due to the unbalanced load.

Therefore, when the load is changed at the load position C, the strain amount of the strain gauges R ₁ , R ₂ , R ₃ , and R ₄ at the respective strain generating portions 20a, 20b, 26a, and 26b is weighted. The result of conversion and analysis is the same as that shown in FIG. 7, and the strain amount with respect to the load change of each strain gauge R ₁ , R ₂ , R ₃ , R ₄ shows individual non-linearity. That is, referring to FIG. 7, the strain gauges R ₁ and R ₂ on the flexure element 12 both show a downward bulging nonlinearity in the amount of strain with respect to a change in load, and the strain on the flexure element 13 is reduced. The gauges R ₃ and R ₄ both show upward swelling non-linearity in the amount of strain with respect to changes in load. However, considering the output of the bridge circuit 42 or the arithmetic unit 43 that uses the total sum of the strain amounts of the strain gauges R _{1 to} R ₄ as a combined output, the nonlinearity of the lower bulge and the nonlinearity of the upper bulge cancel each other out. Together, the combined output shows the same linearity as when the stress center is loaded.

Therefore, the load position A,
If the above-mentioned characteristics of the strain amount in the strain gauges of the respective parts when loads are respectively applied in B and C are summarized in the diagram of FIG.
Can be expressed as That is, when the load position A is the stress center, the moment stresses T _M and C _M due to the eccentric load do not occur, only the stresses T _S and C _S due to the shear mode, and the strain gauges R _{1 to} R ₄ respond to the load change. The amount of distortion exhibits linearity, and the combined output of the bridge circuit 42 also exhibits linearity. On the other hand, a load position B, in C, unbalanced load by moment stress T _M, and C _M is generated, (T _S + T _M) in bulge slightly above characteristics, (C _S + T _M) larger on bulge characteristics, (C _S + C _M ) slightly lower bulge characteristics, (T _S +
C _M ) shows non-linearity with a large downward swelling characteristic. However, in the case of the load position B, the nonlinear output of the bridge circuit 42 or the combined output of the calculator 43 cancels out these nonlinearities and shows linearity. The load position C is similar to the load position B except that the direction of non-linearity is different. In this way, in the case of the load cell balance 41, the influence of the unbalanced load is apparent under the condition that the strain gauges can be formed on the same surface and the assembling / workability can be improved.
It will not be received, and the nonlinearity due to the unbalanced load will be improved. In particular, in the load cell balance 41, one strain gauge R ₁ , R ₂ , R ₃ , R ₄ is arranged for each of the four strain generating parts 20a, 20b, 26a, 26b, and the strain generating body 12 is provided. , 13, and only one bridge circuit 42 is formed so as to straddle 13 and 13, so that a simple configuration is sufficient.

Even in the case of the load cell balance 41, instead of the strain-flexing parts 20a, 20b, 26a, 26b,
Four strain generating parts 2 on the lower surface side of the load cell structure 14
Strain gauges may be attached to 0c, 20d, 26c and 26d. In addition, the load cell structure 14 is replaced with the strain generating elements 12, 13 like the load cell structure 38 shown in FIG.
May be a separate body.

[0047]

According to the load cell and the load cell balance of the present invention, a pair of first and second pairs having a pseudo-Roberval mechanism is provided.
The second strain is applied to the movable support portion of the first strain body by using the strain body of
Since the fixed supporting portions of the strain generating element of No. 1 are connected in a horizontal plane to form a U-shaped load cell structure as a base, the fixed supporting portion of the first strain generating element is fixed to the main body base. When a weighing tray is connected to the movable support portion of the strain generating body to apply a load, even if a moment due to an unbalanced load acts, the first
In the strain element side and the second strain element side of the load cell structure, opposite tensions and compression stresses are generated, and the upper and lower sides of the load cell structure have only one upper and lower sides of the single strain body. It is possible to secure the function of canceling the adverse effect caused by the moment due to the unbalanced load similar to the case where strain gauges are attached to the four strain generating parts, and therefore, the four positions on either one of the upper surface or the lower surface of the load cell structure. Strain gauges are placed in the strain-generating part of, the strain gauges are electrically connected, and the sum of the strain outputs of these strain gauges is output by the bridge arithmetic circuit. Non-linearity can be improved by canceling out the opposing stresses on the first and second strain generating body sides, and the wiring process for the strain gauge and bridge circuit can be completed on one side. Business property can also be improved.

[Brief description of drawings]

FIG. 1 is an external perspective view of a load cell balance showing a first embodiment of the present invention.

FIG. 2 is a plan view thereof.

FIG. 3 is a circuit diagram showing a bridge arithmetic circuit.

FIG. 4 is an external perspective view showing a load position on the load cell balance.

FIG. 5 is a characteristic diagram showing a result of analyzing a state of change in strain amount in each strain gauge when the load is changed at the load position A.

FIG. 6 is a characteristic diagram showing a result of analysis of changes in strain amount in each strain gauge when the load is changed at the load position B.

FIG. 7 is a characteristic diagram showing a result of analysis of changes in strain amount in each strain gauge when a load is changed at a load position C.

FIG. 8 is an explanatory diagram schematically showing how the amount of strain in each strain gauge changes when the load is changed at load positions A, B, and C in a diagram.

FIG. 9 is an external perspective view showing a modified example of the load cell structure.

FIG. 10 is an external perspective view of a load cell balance according to a second embodiment of the present invention.

FIG. 11 is a plan view thereof.

FIG. 12 is a circuit diagram showing a bridge circuit.

FIG. 13 is an external perspective view showing a load position on the load cell balance.

FIG. 14 is an explanatory diagram schematically showing how the amount of strain in each strain gauge changes when the load is changed at load positions A, B, and C in a diagram.

FIG. 15 is an external perspective view showing a conventional load cell balance.

FIG. 16 is an explanatory diagram schematically showing how the strain amount changes in each strain gauge when the load is changed at the load positions a, b, and c.

[Explanation of symbols]

12 1st strain body 13 2nd strain body 14 Load cell structure 15, 16 Beam 17 Fixed support part 18 Movable support part 19 Thin notch 20a-20d Strain part 21 and 22 Beam 23 Fixed support part 24 Movable support 25 thin notch 26a~26d strain generating portion 27 the main body base 28 weighing dish 30 bridge arithmetic circuit 33 first bridge circuit 34 and the second bridge circuit 39 load cell structure 42 bridge circuit (bridge operation circuit) R ₁₁ to R ₄₂ , R ₁ ~ R ₄ strain gauge

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[Procedure amendment]

[Submission date] November 15, 1995

[Procedure amendment 1]

[Document name to be amended] Statement

[Correction target item name] 0026

[Correction method] Change

[Correction contents]

Next, consider the case where a load is applied to the load position B deviated from the stress center. In this case, a moment stress is generated due to the unbalanced load, and the upper surface of the flexure element 12 is compressed.
A force C _M and a tensile stress T _M are generated on the upper surface of the flexure element 13.
Further, as in the case where the strain is applied to the stress center,
a strain gauges R ₁₁ and R ₁₂ , strain gauges 26 a strain gauges
Tensile stress due to shear mode is generated in R ₃₁ and R ₃₂ ,
On the contrary, the strain gauges R ₂₁ , R _{22 of} the strain-flexing portion 20b and the strain-flexing portion 26
Compressive stress due to shear mode is generated in the strain gauges R ₄₁ and R ₄₂ of b . Therefore, when these are put together, the strain generating section 2
The strain gauge R _11, R ₁₂ of 0a, strain tensile stress and the compressive stress caused by the unbalanced load is synthesized is generated by Shieamodo, the strain gauges R _21, R ₂₂ of the strain generating part 20b, the Shieamodo according strain and compressive stress is synthesized by the compression stress and unbalanced load occurs, the strain gauges R _31, R ₃₂ of the strain generating portion 26a, the tensile response <br/> force by unbalanced load and the tensile stress due to Shieamodo DOO distortion synthesized occurs, the strain gauge R _41, R ₄₂ of the strain generating portion 26b, strain and tensile stress due to unbalanced load and compressive stress due to Shieamodo is synthesized are generated.

[Procedure amendment 2]

[Document name to be amended] Statement

[Correction target item name] 0028

[Correction method] Change

[Correction contents]

Further, consider a case where a load is applied to a load position C deviated from the stress center in the opposite direction. In this case, a moment stress is generated due to an eccentric load in the opposite direction to the case of the load position B, and a tensile stress T _M is generated on the upper surface of the flexure element 12 and a compressive stress C _M is generated on the upper surface of the flexure element 13. Also, as in the case where the load on the stress center, the strain gauges R _11, R ₁₂ of the strain generating part 20a, a tensile stress is generated by Shieamodo the strain gauges R _31, R ₃₂ of the strain generating portion 26 a, reverse In addition, the strain-flexing part 20
b strain gauges R ₂₁ and R ₂₂ , strain gauges 26 b strain gauges
Compressive stress due to shear mode is generated in R ₄₁ and R ₄₂ . Therefore, Taken together, the strain generating portions 20a strain gauge R _11, R _12, and strain tensile stress and the tensile by unbalanced load stress is synthesized is generated by Shieamodo strain gauge of the strain generating portion 20b the R _21, R ₂₂ are, occurs strain compressive stress and the tensile by unbalanced load stress is synthesized by Shieamodo, the strain gauges R _31, R ₃₂ of the strain generating unit 26a, a tensile stress due to Shieamodo A strain that is a combination of the compressive stress due to the unbalanced load is generated, and the strain gauges R ₄₁ and R ₄₂ of the strain-flexing portion 26b are generated.
, The strain and compressive <br/> stress due unbalanced load and compressive stress due to Shieamodo is synthesized are generated.

[Procedure 3]

[Document name to be amended] Statement

[Correction target item name] 0041

[Correction method] Change

[Correction contents]

Next, consider the case where a load is applied to the load position B deviated from the stress center. In this case, a moment stress is generated due to the unbalanced load, and the upper surface of the flexure element 12 is compressed.
A force C _M and a tensile stress T _M are generated on the upper surface of the flexure element 13.
Further, as in the case where the strain is applied to the stress center,
Tensile stress due to shear mode is generated in the strain gauges R ₁ and R ₃ of a and 26 a , and conversely, compressive stress due to shear mode is generated in the strain gauges R ₂ and R ₄ of the strain-flexing portions 20 b and 26 b . Therefore, Taken together, the strain gauges R ₁ strain generating portion 20a, the strain and the compressive stress is synthesized by unbalanced load and the tensile stress due to Shieamodo occurs, the strain generating portion 2
The strain gauges R ₂ = 0b, distortion and compressive stress is synthesized by the compression stress and unbalanced load is generated by Shieamodo, the strain gauges R ₃ of the strain generating portion 26a, unbalanced load and the tensile stress due to Shieamodo strain and tensile stress is synthesized is generated by, the strain generating portion 26b strain gauges R ₄ of strain and tensile stress due to compressive stress and unbalanced load by <br/> the Shieamodo is synthesized are generated.

[Procedure amendment 4]

[Document name to be amended] Statement

[Correction target item name] 0043

[Correction method] Change

[Correction contents]

Further, consider a case where a load is applied to a load position C deviated from the stress center in the opposite direction. In this case, a moment stress is generated due to an eccentric load in the opposite direction to the case of the load position B, and a tensile stress T _M is generated on the upper surface of the flexure element 12 and a compressive stress C _M is generated on the upper surface of the flexure element 13. Also, as in the case where the load on the stress center, the tensile stress is generated by Shieamodo the strain gauges R _1, R ₃ of the strain generating portion 20a, 26 a, conversely, the strain of the strain generating portion 20b, 26 b Gauge R ₂ ,
A compressive stress due to shear mode is generated in R ₄ . Therefore, when these are combined, the strain gauge R ₁ of the strain-flexing part 20a is
The generates distortion of the tensile <br/> stress due unbalanced load and the tensile stress due to Shieamodo is synthesized, the strain gauges R ₂ of the strain generating portion 20b, tensile by unbalanced load and compressive stress due to Shieamodo strain and the stress are combined is generated, the strain gauges R ₃ of the strain generating portion 26a, the strain and the compressive stress is synthesized by unbalanced load and the tensile stress due to Shieamodo occurs, the strain generating portion 2
The 6b strain gauges R ₄ of distortion and compressive stress due to unbalanced load and compressive stress due to Shieamodo is synthesized are generated.

Claims (5)

[Claims] 1. A raised support having a fixed support portion and a movable support portion connected by a pair of vertically opposed beams and formed by thin cutouts at four symmetrical positions in the vertical direction of the beam. A pair of first and second strain-generating bodies having a strained portion are provided, and the second member is provided on the movable support portion of the first strain-generating body.
A U-shaped load cell structure in which the fixed support portions of the strain element are connected in a horizontal plane, and the fixed support portion of the first strain element is fixed to the main body base, and the second strain element is fixed. Of the load cell structure in which a weighing dish is connected to the movable support portion of the strain cell, and strain gauges arranged at four strain generating portions on one of the upper surface and the lower surface of the load cell structure. 2. A raised support having a fixed support portion and a movable support portion connected by a pair of vertically opposed beams and formed by thin cutouts at four symmetrical positions in the vertical direction of the beam. A pair of first and second strain-generating bodies having a strained portion are provided, and the second member is provided on the movable support portion of the first strain-generating body.
A U-shaped load cell structure in which the fixed support portions of the strain element are connected in a horizontal plane, and the fixed support portion of the first strain element is fixed to the main body base, and the second strain element is fixed. Of the load cell structure in which the weighing pan is connected to the movable support part of the strain gauges arranged at four strain generating parts on one of the upper surface and the lower surface of the load cell structure, and these strain gauges are electrically connected. And a bridge arithmetic circuit that outputs the sum of the strain outputs of the strain gauges arranged at each of the four strain generating sections. 3. Strain gauges are arranged in pairs in the width direction of the strain-generating body for each of the four strain-generating portions, and the bridge arithmetic circuit has two pairs in two strain-generating portions of the first strain-generating body. And a second bridge circuit formed by two pairs of strain gauges at two strain generating portions of the second strain generating body. The load cell balance according to claim 2, wherein an added value of the output of the first bridge circuit and the output of the second bridge circuit is output as a sum of distortion outputs. 4. Strain gauges are arranged one by one at each of the four strain generating portions, and the bridge arithmetic circuit is arranged so that the strain gauges at the four strain generating portions are adjacent to each other. The load cell balance according to claim 2, further comprising a bridge circuit to which a strain gauge is connected, and an output value of the bridge circuit is output as a sum of strain outputs. 5. The load cell balance according to claim 3, wherein the strain gauge and the wiring for the bridge circuit are formed as a thin film on one surface of the load cell structure by a thin film technique.