JPH0226036Y2 - - Google Patents

Description

[Detailed Description of the Invention] <Industrial Application Field> The present invention relates to a so-called load cell scale that measures the load by applying strain to the load cell due to the load to be measured.

<Prior art> Generally, scales place the object to be measured on its tray and weigh it, but the error in the weighing value caused by the position of the tray on which the object is placed, that is, the eccentricity error, is minimized as much as possible. Preferably small.

In order to eliminate this eccentricity error, conventional load cell scales use a Roberval type load cell in which a strain gauge S is attached to a Roberval mechanism, as shown in FIG. 1.

<Problem to be solved by the invention> In the conventional load cell scale as described above, in order to obtain measurement results without eccentricity errors no matter where it is placed on the tray D, the parallelogram of the Roberval mechanism must be completely It has to be a real thing, and it is difficult to make it, so in the end, Figure 2 shows A- in Figure 1.
As shown in cross-sectional view A, it is necessary to correct the eccentricity error by manually cutting the black part in the figure little by little while changing the load position from W ₁ to W ₅ . The problem was that it required skill.

In addition, in order to ensure the accuracy of the parallelogram, the height of the Roberval mechanism in the load application direction must be greater than a certain value, and in order to obtain a flat scale with a small thickness in the load application direction. has reached its limit.

The present invention has been made in view of the above points, and aims to provide a flat load cell scale that has a simple structure, does not require the work of correcting eccentricity errors by cutting.

<Means for Solving the Problems> The configuration for achieving the above object will be explained with reference to FIGS. 3 to 5 corresponding to the embodiment. 9 and
The strain-generating bodies 3 to 6 each have a flexible portion 10 that can absorb expansion and contraction in the longitudinal direction, and a strain detection portion 11 that detects strain by attaching a strain gauge, in a positional relationship that forms four vertices of a rectangle. Arrange with. In addition, the surfaces to which the strain gauges S1 to S4 are attached to the four strain detection sections are two on the top surface and the remaining two on the bottom surface, for a total of four strain gauges S1 to S4.
A bridge circuit is formed in S4, and a variable resistor Z for unbalance adjustment is inserted into the bridge.
Furthermore, each strain gauge S1 to S in the bridge circuit
4 are connected in parallel to circuits in which variable resistors VR1 to VR4 and fixed resistors R1 to R4 are connected in series, respectively.

<Operation> Two of the strain detecting parts of the flexure generating bodies 3 to 6 arranged at the positions forming the four vertices of the rectangle are on the top surface, and the other two are on the top surface.
One is to attach a strain gauge to the bottom surface, and the total of these is 4.
By assembling a bridge circuit with two strain gauges S1 to S4, the whole forms one load cell, and the strain gauge S of the bridge circuit
1 to S4, variable resistors VR1 to VR4, respectively.
By connecting in parallel a circuit in which fixed resistors R1 to R4 are connected in series, variable resistors VR1 to VR
4 and the variable resistor Z that adjusts the unbalance of the bridge by the adjustment, it is possible to adjust the purely electrical eccentricity error, and the desired purpose can be achieved.

<Embodiment> FIG. 3 is a front view of an embodiment of the present invention, and FIG. 4 is a perspective view of only the load cell portion thereof.

A load-receiving tray 1 is fixed to a coupling member 2 via a spacer 12. A first strain-generating body 3 and a second strain-generating body 4 are arranged at both ends of the surface of the coupling member 2 that is perpendicular to the load application direction and opposite to the surface to which the receiving plate 1 is fixed. The midsection of the first beam 7 is fixed, and a second strain body 5 and a fourth strain body 6 are arranged on the same surface parallel to the first beam 7 at both ends thereof. The midsection of the beam 8 is fixed. As a result, the first to fourth strain bodies 3,
4, 5, and 6 are arranged on the same plane so as to surround the coupling member 2 and form the apexes of a rectangle.

The first to fourth strain-generating bodies 3, 4, 5, and 6 are each provided with a fixing part 9 fixed to the outside via a seat plate 14 at the end thereof, and a load is applied to the inside of the fixing part 9. Strain detection that detects strain against a load by attaching a flexible part 10 consisting of two notches from above and below whose cross section becomes thinner in the receiving direction, and strain gauges S1, S2, S3, and S4, respectively. 11. Here, the flexible portion 10 is for absorbing expansion and contraction in the longitudinal direction of the flexure body perpendicular to the load application direction due to deflection displacement of the flexure body.

In addition, as shown in FIGS. 7a, b, and c, this flexible part 10 has two notches from above and below, one or both of which are parallel to the notches so that the cross section of the flexible part becomes thinner. A structure with additional round holes may also be used.

The strain detecting sections 11 of the first strain body 3 and the fourth strain body 6 have strain gauges S1 and S4 on the lower surface.
Further, strain gauges S2 and S3 are attached to the upper surfaces of the second strain body 4 and the third strain body 5 strain detection section 11.

FIG. 5 is a circuit configuration diagram of the above embodiment of the present invention.

A bridge circuit is formed by the four strain gauges S1 to S4 described above, and each side of the bridge, that is, each strain gauge S1 to S4, is equipped with a variable resistor.
Circuits in which VR1 to VR4 and fixed resistors R1 to R4 are connected in series are connected in parallel.
Here, fixed resistances R1 to R4 are variable resistances VR1 to
This is to limit the amount of adjustment of the resistance value on each side by VR4. In addition, in this circuit, a zero point temperature adjustment resistor α ₀ is inserted on one side of the bridge, and a variable resistance type unbalance adjustment resistor Z is inserted in the bridge, and the bridge output is controlled through this resistor Z. is configured to be retrieved. Furthermore, a sensitivity temperature coefficient adjusting resistor αs is inserted between the bridge and the power source.

In the embodiment of the present invention configured as described above, the eccentricity error is caused by the difference in the outputs of the strain gauges S1, S2, S3, and S4 of the four strain bodies 3, 4, 5, and 6. , the difference can be eliminated by adjusting the variable resistors VR1, VR2, VR3, or VR4. Here, variable resistor VR1
The loss of zero balance of the bridge due to the adjustment of ~VR4 can be corrected by adjusting the variable unbalance adjustment resistor Z. Therefore, in order to correct the eccentricity error in the embodiment of the present invention, while changing the load application position on the receiving tray 1, the variable resistors VR1 to VR4 and, if necessary, the unbalance adjustment resistor Z are adjusted. Therefore, it can be performed using a purely electrical method.

In addition, the flexible portion 10 of each strain-generating body in the above embodiments
As shown in the front view in FIG.
and the strain detection section 11 may be connected by an elastic band 13 that is formed of a thin plate, has almost no extension in its longitudinal direction, and is easily bent in a direction perpendicular thereto.

Furthermore, in the above-mentioned embodiment, two of the four strain-generating bodies are connected by beams and fixed to the connecting member 2, but the four strain-generating bodies may be cut out of one material or individually separated. Of course, it is also possible to connect the receiver plate 1 to the connecting member 2 in the above-mentioned embodiment, and fix the fixing part 9 of each strain body to the outside. It goes without saying that the receiving tray 1 may be fixed to the fixing portion 9 of each strain-generating body and the coupling member 2 may be fixed to the outside.

<Effects of the invention> As explained above, according to the invention, strain-generating bodies are arranged in a positional relationship that forms the four vertices of a rectangle, and strain gauges are installed on the upper surfaces of two of them and the lower surfaces of the other two. By pasting these four strain gauges together to form a bridge circuit, the four strain-generating bodies form one load cell, and a variable resistor for unbalance adjustment is installed in the bridge circuit. At the same time, each strain gauge was connected in parallel with a circuit in which a variable resistor and a fixed resistor were connected in series. Therefore, with a relatively simple configuration using four strain gauges, each side of the bridge could be By adjusting a total of five variable resistors, including variable resistors and variable resistors for unbalance adjustment, it is possible to correct the eccentricity error of the scale purely electrically, eliminating the need for skill as in the past. do not have. Moreover, it is only necessary to affix a total of four strain gauges, one at each location, making it possible to achieve cost reductions in terms of both material costs and affixing man-hours. As such, there is no need to provide a height above a certain level in the load application direction, and a flat scale can be easily obtained, making it easy to load and unload objects to be measured, making it particularly suitable for bed scales. .

[Brief explanation of the drawing]

Fig. 1 is an explanatory diagram of a conventional Roberval type load cell scale, Fig. 2 is a cross-sectional view thereof, Fig. 3 is a front view of an embodiment of the present invention, Fig. 4 is a perspective view of its main parts, Fig. 5
The figure is a bridge connection diagram of an embodiment of the present invention, FIG. 6 is a front view of another embodiment of the present invention, and FIG. be. 1... saucer, 2... coupling member, 3, 4, 5,
6... Strain body, 9... Fixed part, 10... Flexible part,
11...Distortion detection section, S1, S2, S3, S4...
Strain gauge, VR1, VR2, VR3, VR4...variable resistance, R1, R2, R3, R4...fixed resistance,
Z...variable resistor for unbalance adjustment.

Claims (1)

[Claims for Utility Model Registration] (1) It has a fixed part that is fixed to the outside, a flexible part that can absorb expansion and contraction in the longitudinal direction, and a strain detection part that detects strain by attaching a strain gauge. The strain-generating bodies are arranged in a positional relationship forming four vertices of a rectangle, and the surfaces to which the strain gauges are attached to the four strain detection sections are two on the top surface and the remaining two on the bottom surface, A total of four strain gauges form a bridge circuit,
In addition, a variable resistor for unbalance adjustment is inserted into the bridge, and each strain gauge is connected in parallel with a circuit in which a variable resistor and a fixed resistor are connected in series. (2) The load cell scale according to claim 1, wherein the flexible portion of the strain-generating body is a cut portion from above and below. (3) The load cell scale according to claim 2 of the utility model registration, characterized in that a round hole is added to both or one of the upper and lower notch portions, which are the flexible portions of the strain-generating body. (4) The load cell scale according to claim 1 of the utility model registration, characterized in that a fixed part of the strain-generating body and a strain detection part are connected by an elastic band to form a flexible part.