Load cell

The present invention relates to a parallelogram type, so-called reverbal type load cell used in various measuring devices such as a measuring hopper, a measuring conveyor, and a measuring tank.

As a parallelogram type load cell, for example, as shown in Patent Document 1, a fixed portion fixedly supported by a base of a weighing device and a movable portion receiving a load are provided as an upper beam portion and a lower beam portion. It is known that thin-walled strain-causing portions are formed at both ends of the upper beam portion and the lower beam portion, and strain gauges are attached to each strain-causing portion.

<p num="0003"><patcit num="1"><text>Japanese Unexamined Patent Publication No. 2012-63307</text></patcit></p>

<p num="0004"> For example, the central axis in the extending direction of the vertical beam extending over the fixed portion and the movable portion of the parallelogram load cell on the measuring table mounted on the movable portion of the parallelogram load cell used for the platform scale. When an article is placed at a position distant from the left and right direction, a large torsional force acts on the strain-causing portion formed between the fixed portion and the movable portion, and this twisting force causes torsional strain in the strain-causing portion, resulting in a weight value. There will be an error.</p><p num="0005"> The present invention has been made by paying attention to such a situation, and a large eccentric load acts on a measuring table mounted on a movable part of a parallelogram load cell such as a measuring hopper at a position away from the center. However, it is an object of the present invention to provide a load cell having a small torsional strain generated in the strain-causing portion.</p>

<p num="0006"> In order to achieve the above object, the present invention is configured as follows.</p><p num="0007"> (1) In the present invention, a fixed portion that is fixedly supported, a movable portion that receives a load, an upper beam portion that connects the fixed portion and the upper portion of the movable portion, and a lower portion of the fixed portion and the movable portion are connected. A lower beam portion is provided, and in each of the upper and lower beam portions, strain-causing portions for load detection are formed at two locations, one near the fixed portion and the other near the movable portion, and the strain-causing portions are formed. It is a parallelogram type load cell to which strain gauges are attached. In each of the strain-causing portions, a plurality of split strain-causing portions are formed in parallel along a direction orthogonal to the extending direction of each of the beam portions extending over the fixed portion and the movable portion. ..</p><p num="0008"> According to the present invention, the strain-causing portions provided on the upper and lower beams are composed of a plurality of split strain-causing portions arranged along a direction orthogonal to the extending direction of the upper and lower beams, and the extending direction of the upper and lower beams. By providing a split strain generating portion at a position away from the central axis of the above and supporting the biased load at a position closer to the application point of the eccentric load than when only one strain generating portion is provided, each strain generating portion is provided. The load measurement accuracy is improved by reducing the twisting force acting and reducing the torsional strain of each strain generating portion.</p><p num="0009"> (2) In a preferred embodiment of the present invention, each of the strain-causing portions has three split strain-causing portions formed in parallel along the orthogonal directions. More preferably, the strain gauge is attached to the central divided strain generating portion of the three split strain raising portions.</p><p num="0010"> Further, it is preferable that the spring constants of the two split raising and straining portions on both sides are equal.</p><p num="0011"> The amount of deflection of the load cell with respect to the load is balanced by forming the divided strain generating portions having the same spring constant on both sides of the split strain generating portion in the central portion in parallel along the orthogonal direction. , The load cell does not twist, and there is no error due to it.</p><p num="0012"> (3) In a preferred embodiment of the present invention, the central split straining portion has connecting portions for connecting the split straining portion and the rigid body portion at both ends along the extending direction. The width of the connecting portion along the orthogonal direction is formed to be narrower than the width of the attachment portion of the strain gauge along the orthogonal direction.</p><p num="0013"> According to this embodiment, when a load is applied unevenly in the movable portion and a torsional load is applied to the entire load cell, the split strain-causing portion in the central portion connected to the rigid body portion by the narrow connecting portion is subjected to. The twisting force is less likely to act, and the load measurement accuracy is higher.</p><p num="0014"> (4) In another embodiment of the present invention, the plurality of divided strain-causing portions are formed by circular through holes penetrating vertically in a direction orthogonal to the extending direction of each beam portion.</p><p num="0015"> According to this embodiment, the division of the strain generating portion for forming the plurality of split strain generating portions is performed by the circular through holes formed in the vertical direction perpendicular to the extending direction of the beam portion. , It is easy to manufacture a plurality of split raising and straining portions.</p>

<p num="0016"> As described above, according to the present invention, a highly accurate weight value can be obtained by easily forming a strain-causing portion having a small torsional strain.</p>

<figref num="1">It is a perspective view which shows the load cell which concerns on embodiment of this invention.</figref><figref num="2">It is a top view which shows the load cell of FIG.</figref><figref num="3">It is a cross-sectional view of AA in FIG.</figref><figref num="4">It is a perspective view which shows the modification of the load cell of Embodiment of FIG.</figref><figref num="5">It is a top view which shows the load cell of FIG.</figref><figref num="6">It is a figure which shows the cross section of the straining part of the load cell of FIG. 1 and the cross section of the straining part of a conventional load cell.</figref><figref num="7">It is a top view which shows the modification of the load cell of embodiment of FIG.</figref>

Hereinafter, embodiments of the present invention will be described in detail with reference to the drawings.

(Embodiment 1) FIG. 1 is a perspective view of a load cell according to an embodiment of the present invention, FIG. 2 is a plan view thereof, and FIG. 3 is a sectional view taken along the line AA in FIG.

The load cell 1 of this embodiment is a parallelogram type load cell that cuts through the inside of a metal material such as a square block-shaped aluminum alloy or SUS in the lateral direction. The load cell 1 horizontally connects the vertically long fixed portion 2 fixedly supported by the base of the weighing device, the vertically elongated movable portion 3 that receives the measured load, and the upper and lower parts of the fixed portion 2 and the movable portion 3, respectively. It includes a beam unit 4 and a lower beam unit 5. The upper and lower beam portions 4 and 5 extend over the fixed portion 2 and the movable portion 3, and are closer to both ends in the extending direction (horizontal direction in FIG. 2), that is, closer to the fixed portion 2 and the movable portion 3. Thin-walled strain-causing portions 6 are formed by curved cutting from the internal space side at each of the two locations near each other, and strain gauges 7 are attached to the outer surfaces of the strain-causing portions 6.

Circular through holes 8 and 8 penetrating in the vertical direction are formed at two locations in each strain generating portion 6 in the direction orthogonal to the beam extending direction (vertical direction in FIG. 2 and horizontal direction in FIG. 3), respectively. Each of the strain generating portions 6 is composed of three split strain generating and straining portions 6a, 6b, and 6c which are divided and paralleled in the orthogonal directions. Since the strain-causing portion is divided by a circular through hole, it is easy to manufacture.

Next, the cross section of the split strain-causing portion of the load cell shown in FIG. 1 and the strain-causing portion of the conventional parallelogram load cell in Patent Document 1 (Japanese Patent Laid-Open No. 2012-63307) are compared in FIG.

The moment of inertia of area I1 and the section modulus Z1 of the strain-causing part of the conventional load cell are I1 = (1/12), (2b1 + b2), h1 respectively.³, Z1 = (1/6) (2b1 + b2) h1²It is assumed that the geometrical moment of inertia of area I2 and the synthetic cross-section coefficient Z2 of the split strain portion of the load cell shown in FIG. 1 are also the same values as I1 and Z1, respectively.

When an article is placed at a position p away from the central axis L in the extending direction of the vertical beam extending over the fixed portion and the movable portion of the parallelogram load cell in the left-right direction, the fixed portion and the movable portion become A large twisting force acts on the strain-causing portion formed between them.

In order to manufacture a load cell having the same rated load but having a strain-causing portion having a high yield strength against a torsional force F in a conventional load cell, the thickness h1 of the strain-causing portion is reduced to h1'as shown by the dotted line in FIG. Instead, the width is increased from (2b1 + b2) to (2b1 + b2)', and the position of the strain generating part is brought closer to the eccentric load F acting on the weighing table. However, if the thickness h1'is reduced, the processing accuracy of the strain-causing portion will vary, so the thickness of the strain-causing portion of the load cell to be produced will vary, and the magnitude of the load signal with respect to the rated capacity will vary. Expands. Therefore, there is a limit to the expansion of the width of the strain generating portion.

On the other hand, when a load cell having the same rated capacity, that is, a load cell that outputs a load signal of the same magnitude when a rated load is applied, is manufactured, the width of one strain generating portion is before forming the split strain generating portion. Is wider than that of a load cell that has a strain-bearing part with high yield strength against conventional torsional force, and instead, a circular penetration that penetrates in the vertical direction at the left and right positions across the central axis L of one strain-bearing part. Holes 8 and 8 are provided, respectively, and the combined moment of inertia of area I2 and the combined section coefficient Z2 in the divided strain-causing portion divided into a plurality of through holes 8 and 8 are held in one strain-causing portion of the load cell having a high yield strength. Equal to the moment of inertia of area I1 and the moment of inertia Z1 of.

Since a circular hole is provided and the strain-causing portion is divided into a plurality of parts, when manufacturing a load cell having the same rated capacity, the thickness of the divided strain-causing part is a conventional load cell having a high torsional strength composed of one strain-causing part. The thickness in the case of can be maintained.

That is, although the rated load of the load cell is the same, the strain generating portion is formed at a position farther than the central axis L without making the thickness of the strain generating portion too thin, and the torsional force composed of one straining portion is formed. By supporting the eccentric load at a position closer to the application point of the eccentric load than the conventional load cell having high resistance, a load cell having higher resistance to torsional force can be manufactured.

(Embodiment 2) 4 and 5 show perspective views and plan views of the load cell according to another embodiment of the present invention, and the parts corresponding to FIGS. 1 and 3 are designated by the same reference numerals.

This load cell 1₁Is basically configured in the same manner as in the above embodiment, and cuts through the inside of a square block-shaped metal material to hold a vertically long fixed portion 2 fixedly supported by a base of a weighing device and a measured load. The upper and lower parts of the vertically long movable part 3 to be received are connected by the horizontal upper beam part 4 and the lower beam part 5, respectively. Both ends of the upper beam portion 4 and the lower beam portion 5 are curved and cut from the internal space side to create a thin-walled strain generating portion 6.₁And each strain generating part 6₁It is configured in a parallelogram shape with a strain gauge 7 attached to the outer surface of the.

Each strain generating part 6₁At two locations in the direction orthogonal to the beam extension direction (vertical direction in FIG. 5), there are partial arc-shaped through holes 8 with respect to the load cells shown in FIGS. 1 and 2.₁Is formed, and each strain generating part 6₁However, the three split generating and straining portions 6 divided and paralleled in the orthogonal direction₁a, 6₁b, 6₁It consists of c.

In addition, the split raising and straining part 6₁a, 6₁b, 6₁Divided strain generating part 6 in the center of c₁A strain gauge 7 is attached to the outer surface of b.

Load cell 1 configured in this way₁Exhibits the performance of having high resistance to twisting force, as in the above embodiment. Furthermore, the split raising and straining part 6₁a, 6₁b, 6₁Through hole 8 that divides c₁Is a partial arc shape, so the central split-strain portion 6₁At both ends of the beam extending direction (horizontal direction in FIG. 5) of b, connecting portions 14 having a width narrower in the direction orthogonal to the gauge attachment portion (vertical direction in FIG. 5) are formed. .. Each connecting portion 14 is a split raising / straining portion 6₁b is connected to the fixed portions 2, the movable portions 3, or the beam portions 4 and 5, which are rigid bodies on both sides thereof.

In this embodiment, the torsional stress generated by the eccentric load applied to the movable portion 3 of the load cell 1 is absorbed by the narrow connection 14, and the split strain generating portion 6₁It becomes difficult to be transmitted to the strain gauge 7 of b, and the error of the load signal due to the torsional stress can be reduced.

FIG. 7 shows the through hole 8₁Is formed by a circular through hole to facilitate processing.

1,1₁ Load cell 2 Fixed part 3 Moving parts 4 Upper beam part 5 Lower beam part 6,6₁ Distortion part 6a,6₁a Divided distortion section 6b, 6₁b Divided strain 6c, 6₁c Divided strain 7 Strain gauge 8,8₁ Through hole 9 space 14 Connection