JP6696026B1 - Load cell - Google Patents

Abstract

PROBLEM TO BE SOLVED: To improve workability of strain gauge mounting work and wiring work in a load cell, and to improve environment resistance. A load cell (1) includes a flexure element and a plurality of strain gauges attached to the flexure element and forming at least one bridge circuit. The flexure element is a flexure element body that is an elastic body, a plurality of holes that form an opening in the outermost surface of the flexure element body, and that extend inward of the flexure element body, and a plurality of holes, respectively. And a plurality of airtight members that seal the openings of the. The plurality of strain gauges are attached to the hole wall of the flexure element body that defines each of the plurality of holes. [Selection diagram] Figure 1

Description

  The present invention relates to load cells.

  In Patent Document 1, a columnar strain-generating body, a plurality of small-diameter holes having a predetermined depth extending from one end face side of the strain-generating body toward the other end face side, and bonded to the side peripheral surface of each hole And a load cell including the strain gauge described above. The hole is centered on the neutral axis of the stress so that the strain gauge does not detect bending strain at a position away from the neutral axis when an eccentric load is applied to the strain generating body. Gauge is installed.

  Patent Document 2 discloses a load cell including a columnar strain element and a plurality of strain gauges forming a Wheatstone bridge circuit. On the outer peripheral surface of the columnar strain body, a plurality of holes extending inward through the neutral surface of the stress in the columnar strain body are formed at predetermined intervals in the circumferential direction. The strain gauge is attached to the stress neutral axis so that the strain gauge does not detect bending strain at a position away from the neutral axis when an unbalanced load is applied to the columnar strain body. Further, in order to protect the strain gauge from a change in sensitivity due to moisture or the like and a damage due to an external force, a cylindrical outer cover and an inner cover are attached to the flexure element.

JP-A-59-174726 JP-A-6-207867

  In Patent Document 1, since it is necessary to attach the strain gauge to the small-diameter hole, it is difficult to perform the work of attaching the strain gauge to the strain element and the work of connecting the strain gauge to form the Wheatstone bridge circuit.

  Further, in Patent Document 2, when the outer cover and the inner cover are welded to the columnar flexure element, stress is concentrated on the welded portion, and the outer cover and the inner cover may be damaged from the welded portion depending on the use environment. This damage impairs the environmental resistance of the load cell.

  An object of the present invention is to improve workability of strain gauge mounting work and wiring work in a load cell, and to improve environment resistance.

One aspect of the present invention includes a flexure element and a plurality of strain gauges attached to the flexure element and forming at least one bridge circuit, the flexure element having a pressure receiving surface, and an elastic body. And a plurality of holes extending inwardly of the strain body, forming an opening in the outermost surface of the strain body, which is provided in a portion projecting outward from the pressure receiving surface. Section, and a plurality of airtight members for sealing the respective openings of the plurality of holes, the plurality of strain gauges, in the hole wall of the strain element body defining each of the plurality of holes. Provide the attached load cell.

  According to this configuration, the strain gauge is attached to the hole wall of the flexure element body that defines the hole that forms the opening on the outermost surface of the flexure element body. Therefore, since the work of attaching the strain gauge to the strain-flexing body can be performed from the opening formed on the outermost surface of the strain-flexing body, the workability of the work of attaching the strain gauge can be improved.

  Further, according to this configuration, since the opening for mounting the strain gauge is sealed by the airtight member, the strain gauge is suppressed from being exposed to the outside, so that the strain gauge is less likely to be affected by the outside. The environment resistance of the load cell can be improved.

  Further, for example, when fixing the airtight member to the opening provided in the strain body by welding, the welding length required for welding the airtight member to the opening that is a part of the outermost surface of the strain body is The welding length is shorter than the welding length required to weld the airtight member to the entire circumference of the outermost surface of the flexure body. According to this configuration, as compared with the case where the airtight member is welded around the outermost surface of the flexure body, stress is less likely to be concentrated in the welded portion, and the load cell is prevented from being damaged from the welded portion. Therefore, the environment resistance can be improved.

  The flexure element may include at least one connecting hole provided in the flexure element body and communicating with at least two of the plurality of holes.

  According to this configuration, when the bridge circuit is formed, the lead wire of the strain gauge is connected through the connecting hole provided in the strain-flexing body whose opening is sealed. The lead wire of the gauge is not exposed to the outside and the environment resistance can be improved.

  The at least one bridge circuit may include a first bridge circuit and a second bridge circuit connected in parallel with the first bridge circuit, the output from the first bridge circuit, and the second bridge circuit. There may be at least one adjusting resistor that adjusts the output from the circuit.

  According to this configuration, the output from the first bridge circuit and the output from the second bridge circuit are adjusted by the adjusting resistor, so that the strain gauge mounting position may be affected by the inaccuracy of the mounting position or the unbalanced load. Even if there is a difference in output sensitivity between the first bridge circuit and the second bridge circuit, the measurement accuracy can be improved.

  The plurality of strain gauges are provided in each of the plurality of holes, a first strain gauge disposed at a predetermined position in the depth direction of each of the plurality of holes, and each of the plurality of holes. A second strain gauge may be provided that is provided at a position different from the first strain gauge in the depth direction of each of the plurality of holes, and the first bridge circuit may include the plurality of holes. The second strain gauge may be formed by the first strain gauge provided in each of the portions, and the second bridge circuit may be formed by the second strain gauge provided in each of the plurality of holes.

  The plurality of holes extend from the first portion forming the opening toward the inside of the strain-flexing body main body, and at least one of the plurality of strain gauges is arranged. Two sections may be respectively provided, and a cross-sectional area of the first section in a cross section in the depth direction may be larger than a cross-sectional area of the second section in the cross section in the depth direction.

  According to this configuration, the second portion where the strain gauge is arranged is formed smaller than the first portion even when the opening is made large in order to facilitate the work of attaching or connecting the strain gauge. Therefore, the decrease in strength due to the hole can be suppressed. As a result, it is possible to suppress the decrease in the strength of the load cell while improving the workability of the strain gauge mounting work.

  The strain element may have a flat shape.

  The strain body may be disc-shaped.

  The strain element may be annular.

  The strain generating element may have a rectangular flat plate shape.

  According to the present invention, in the load cell, the workability of the strain gauge mounting work and the wiring work can be improved, and the environment resistance can be secured. Further, according to the present invention, the measurement accuracy can be improved in the load cell.

The perspective view of the load cell concerning a 1st embodiment of the present invention. The top view of the load cell which concerns on 1st Embodiment. Sectional drawing which followed the III-III line of FIG. The circuit diagram of the Wheatstone bridge circuit of the load cell concerning a 1st embodiment. The perspective view of the load cell which concerns on 2nd Embodiment of this invention. The top view of the load cell which concerns on 2nd Embodiment. Sectional drawing which followed the VII-VII line of FIG. The circuit diagram of the Wheatstone bridge circuit of the load cell concerning a 2nd embodiment. The perspective view of the load cell which concerns on the modification of 2nd Embodiment. The top view of the load cell which concerns on the modification of 2nd Embodiment. Sectional drawing which followed the XI-XI line of FIG. The perspective view of the load cell concerning a 3rd embodiment of this indication. The top view of the load cell which concerns on 3rd Embodiment.

  Hereinafter, a load cell according to an embodiment of the present invention will be described with reference to the accompanying drawings.

(First embodiment)
FIG. 1 is a perspective view of a load cell 1 according to the first embodiment of the present invention. FIG. 2 is a top view of the load cell 1 according to the first embodiment of the present invention. 3 is a sectional view taken along the line III-III in FIG.

[overall structure]
Referring to FIG. 1 to FIG. 3, the load cell according to the present embodiment includes a flexure element 10 and a plurality of (eight in this embodiment) strain gauges g11 to g14 and g21 to g24 attached to the flexure element 10. With.

  The flexure element 10 of the present embodiment has a substantially annular flat shape. In other words, the load cell 1 of this embodiment is a washer type load cell. The load cell 1 of this embodiment can be applied to, for example, measurement of a load applied to a rolling roll of a rolling mill. In the present invention, the flat shape refers to a value B / of the ratio of the maximum dimension B in the direction orthogonal to the height direction of the strain body 10 to the dimension A in the height direction of the strain body 10 as shown in FIG. A means a shape having 2 or more, for example. In the present embodiment, the maximum dimension B in the direction orthogonal to the height direction of the strain body 10 is the diameter of the strain body 10.

  The flexure body 10 includes a flexure body main body 20 that is an elastic body, and a plurality of (four in the present embodiment) holes 30A, 30B, 30C, and 30D provided in the flexure body main body 20. Further, as shown in FIGS. 1 and 2, the strain-flexing body 10 includes a cable 11 for connecting the strain gauges g11 to g14, g21 to g24 to a load indicator (not shown), and a strain-generating strain on the cable 11. A cable outlet fitting 12 for pulling to the outside of the body 20 is provided.

  The flexure body main body 20 of the present embodiment has a substantially annular flat shape. In other words, the flexure body main body 20 includes a cylindrical outermost surface 21 and a cylindrical inner surface 22 arranged coaxially with the outermost surface 21. The outermost surface 21 of the flexure body 20 has four openings 21a formed by the four holes 30A, 30B, 30C, and 30D. Further, as shown in FIG. 2, the outermost surface 21 of the flexure body 20 is provided with a cable drawing opening 21b to which the cable drawing metal fitting 12 is attached.

  The flexure body main body 20 of the present embodiment has a first pressure receiving surface 23 formed on one end surface (upper side in FIG. 3) and a second pressure receiving surface formed on the other end surface (lower side in FIG. 3). Surface 24. The first pressure receiving surface 23 and the second pressure receiving surface 24 are annular and are arranged coaxially with each other. The strain body main body 20 is an elastic body and generates strain in correlation with the load received by the first pressure receiving surface 23 or the second pressure receiving surface 24.

  As shown in FIG. 2, the holes 30A, 30B, 30C, 30D of the present embodiment extend from the outermost surface 21 of the strain-flexing body 20 toward the inner side in the radial direction of the strain-flexing body 20. .. The holes 30A, 30B, 30C, and 30D are provided so as to penetrate the outermost surface 21 of the strain-flexing body 20, so that the outermost surface 21 of the strain-generating body 20 has four openings 21a. Are formed. Further, the holes 30A, 30B, 30C, 30D are provided so as not to penetrate the inner side surface 22 of the flexure body 20. In other words, the holes 30A, 30B, 30C, 30D have bottoms on the inner surface 22 side of the flexure body 20. Further, in the present embodiment, the four hole portions 30A, 30B, 30C, 30D are provided at equal intervals in the circumferential direction of the flexure body main body 20. In other words, the four holes 30A, 30B, 30C, 30D are provided at intervals of 90 degrees in the circumferential direction of the flexure body main body 20.

  The hole portions 30A, 30B, 30C, 30D are defined by the hole wall 25 of the flexure body main body 20. The hole wall 25 of the flexure body 20 of the present invention defines a bottom wall 25a that defines the bottoms of the holes 30A, 30B, 30C, 30D and an outer periphery other than the bottoms of the holes 30A, 30B, 30C, 30D. The side wall 25b is included.

  The holes 30A, 30B, 30C, and 30D are the first portion 31 that forms the opening 21a formed in the outermost surface 21 of the strain body 20 and the radial direction of the strain body 20 from the first portion 31. A second portion 32 extending inward.

  As shown in FIG. 1, the first portion 31 and the second portion 32 of the holes 30A, 30B, 30C, 30D have a circular cross-sectional shape in a cross section orthogonal to the depth direction (in the present embodiment, the radial direction). have. In addition, the cross-sectional area of the cross section orthogonal to the depth direction (radial direction in this embodiment) of the first portion 31 of the holes 30A, 30B, 30C, 30D is the second portion 32 of the holes 30A, 30B, 30C, 30D. Is larger than the cross-sectional area of the cross section orthogonal to the depth direction (radial direction in this embodiment). Further, as shown in FIG. 2, the first portions 31 of the holes 30A, 30B, 30C, 30D are arranged so as not to overlap the first pressure receiving surface 23 of the flexure body main body 20 in a top view. There is.

  In the present embodiment, the four openings 21a are formed in the outermost surface 21 of the flexure body 20 by the four holes 30A, 30B, 30C and 30D as described above. As shown in FIG. 1, the opening 21a formed in the outermost surface 21 of the flexure body 20 has a circular shape corresponding to the cross-sectional shape of the holes 30A, 30B, 30C, and 30D. In addition, as shown in FIG. 2, the four openings 21a are provided at equal intervals in the circumferential direction of the flexure body main body 20 in correspondence with the positions of the four hole portions 30A, 30B, 30C, and 30D. In other words, the four openings 21a are provided on the outermost surface 21 of the flexure body 20 at intervals of 90 degrees in the circumferential direction of the flexure body 20.

  As shown in FIGS. 2 and 3, the flexure element 10 of the present embodiment has four metal diaphragms that seal the four openings 21a formed by the four holes 30A, 30B, 30C, and 30D, respectively. 40 is provided. In FIG. 1, the illustration of the metal diaphragm 40 is omitted. The metal diaphragm 40 according to the present embodiment is an example of the airtight member according to the present invention.

  The metal diaphragm 40 is welded to the strain-flexing body 20 so as to seal the opening 21a. The metal diaphragm 40 is made of a flexible material. In addition, as shown in FIG. 2, the metal diaphragm 40 is arranged so as not to overlap the first pressure receiving surface 23 in a top view.

  As shown in FIG. 2, the flexure element 10 according to the present embodiment includes at least one of the holes 30A, 30B, 30C, and 30D that communicates with two adjacent to the flexure element body 20 in the circumferential direction (the present embodiment). Has four) connecting holes 50A, 50B, 50C, 50D. Specifically, the connection hole 50A communicates with the first portion 31 of the hole portion 30A and the first portion 31 of the hole portion 30B that are adjacent to each other in the circumferential direction of the flexure body main body 20. The connecting hole 50B communicates with the first portion 31 of the hole portion 30B and the first portion 31 of the hole portion 30C that are adjacent to each other in the circumferential direction of the flexure body main body 20. The connecting hole 50C communicates with the first portion 31 of the hole portion 30C and the first portion 31 of the hole portion 30D that are adjacent to each other in the circumferential direction of the flexure body main body 20. The connecting hole 50D communicates with the first portion 31 of the hole portion 30D and the first portion 31 of the hole portion 30A that are adjacent to each other in the circumferential direction of the flexure body 20.

  The connecting holes 50A, 50B, 50C, 50D of the present embodiment extend linearly in a direction intersecting the radial direction of the strain body main body 20. The connecting hole 50A and the connecting hole 50C face each other and extend in parallel with each other. Similarly, the connecting hole 50B and the connecting hole 50D face each other and extend in parallel with each other. Further, the connecting hole 50A communicates with the connecting hole 50D at the hole 30A and communicates with the connecting hole 50B at the hole 30B. Further, the connecting hole 50C communicates with the connecting hole 50B at the hole portion 30C and communicates with the connecting hole 50D at the hole portion 30D. As a result, the connecting holes 50A, 50B, 50C, and 50D have a rectangular shape in a top view.

  In addition, as shown in FIG. 2, the flexure element 10 extends in the radial direction of the flexure element body 20 and is an extraction hole 13 provided so as to reach the coupling hole 50D from the cable extraction opening 21b of the flexure element body 20. Equipped with. The extraction hole 13 communicates with the cable extraction opening 21b and the connection hole 50D.

  The strain gauges g11 to g14 and g21 to g24 of the present embodiment are arranged in the hole portions 30A, 30B, 30C and 30D so as to detect strain in the thickness direction of the flexure body 20 (vertical direction in FIG. 3). Has been done. As shown in FIG. 2, the strain gauges g11 to g14 and g21 to g24 are arranged so as to overlap the first pressure receiving surface 23 in a top view. Further, the strain gauges g11 to g14 and the strain gauges g21 to g24 are arranged at different positions in the depth direction of the hole portions 30A, 30B, 30C, 30D. Specifically, the strain gauges g11 to g14 and the strain gauges g21 to g24 are an outer surface (outer diameter d1 (shown in FIG. 3)) and an inner surface of the annular first pressure receiving surface 23 and the second pressure receiving surface 24. (Inside diameter d2 (shown in FIG. 3)) and the center plane C are sandwiched. Here, the center plane C is a cylindrical surface, and the diameter dc (shown in FIG. 3) of the center plane C is (d1 + d2) / 2. The strain gauges g11 to g14 are arranged at approximately the same position in the radial direction of the strain body main body 20. The strain gauges g21 to g24 are arranged at approximately the same position in the radial direction of the strain-flexing body 20.

  In the hole portion 30A, a strain gauge g11 is arranged radially inward of the strain-flexing body 20 with respect to the center plane C of the first pressure-receiving surface 23 and the second pressure-receiving surface 24. A strain gauge g21 is arranged on the outer side in the radial direction of the strain-flexing body 20 with respect to the center plane C of the second pressure receiving surface 24. In other words, the strain gauge g21 is arranged outside the strain gauge body 20 in the radial direction with respect to the strain gauge g11. The strain gauges g11 and g21 are attached to the hole wall 25 of the strain-flexing body 20 that defines the second portion 32 of the hole 30A.

  In the hole portion 30B, a strain gauge g12 is arranged radially inward of the strain body main body 20 with respect to the center plane C of the first pressure receiving surface 23 and the second pressure receiving surface 24, and the first pressure receiving surface 23 and A strain gauge g22 is arranged outside the center plane C of the second pressure receiving surface 24 in the radial direction of the strain body main body 20. In other words, the strain gauge g22 is arranged outside the strain gage main body 20 in the radial direction with respect to the strain gauge g12. The strain gauges g12 and g22 are attached to the hole wall 25 of the strain-flexing body 20 that defines the second portion 32 of the hole 30B.

  In the hole portion 30C, a strain gauge g13 is arranged on the inner side in the radial direction of the strain-flexing body 20 with respect to the center plane C of the first pressure receiving surface 23 and the second pressure receiving surface 24. A strain gauge g23 is arranged outside the center of the second pressure receiving surface 24 in the radial direction of the flexure body 20. In other words, the strain gauge g23 is arranged on the outer side in the radial direction of the strain-flexing body 20 with respect to the strain gauge g13. The strain gauges g13 and g23 are attached to the hole wall 25 of the strain-flexing body 20 that defines the second portion 32 of the hole 30C.

  In the hole portion 30D, a strain gauge g14 is arranged inside the center of the first pressure receiving surface 23 and the second pressure receiving surface 24 in the radial direction of the strain-flexing body 20, and the first pressure receiving surface 23 and A strain gauge g24 is arranged outside the center plane C of the second pressure receiving surface 24 in the radial direction of the strain-flexing body 20. In other words, the strain gauge g23 is arranged on the outer side in the radial direction of the strain-flexing body 20 with respect to the strain gauge g13. The strain gauges g14 and g24 are attached to the hole wall 25 of the flexure body 20 that defines the second portion 32 of the hole 30D.

  As shown in FIG. 3, lead wires L are connected to the strain gauges g11 to g14 and g21 to g24. For clarity, the lead wire L is not shown in FIGS. 1 and 2, and only the lead wire L connected to the strain gauge g21 is shown in FIG.

  The lead wires L of the strain gauges g11 to g14 are connected through the connection holes 50A, 50B, 50C, 50D. Similarly, the lead wires L of the strain gauges g21 to g24 are connected through the connecting holes 50A, 50B, 50C and 50D. Further, the lead wires L of the strain gauges g11 to g14 and g21 to g24 are connected to the cable 11 through the extraction hole 13 and are drawn out from the cable flexure outlet fitting 12 to the outside of the flexure body main body 20. The cable 11 electrically connects the lead wires L of the strain gauges g11 to g14 and g21 to g24 and a load indicator (not shown).

[Circuit configuration of load cell]
FIG. 4 is a circuit diagram of the load cell 1 according to the first embodiment.

  Referring to FIG. 4, the strain gauges g11 to g14 are connected to each other so as to form a bridge circuit 60. More specifically, the bridge circuit 60 is formed by strain gauges g11 to g14 and temperature compensating dummy gauges d11 to d14. As described above, since the strain gauges g11 to g14 are arranged inside the center of the first pressure receiving surface 23 and the second pressure receiving surface 24 in the radial direction of the strain-flexing body 20, the bridge circuit 60 is provided. Outputs the strain of the strain-flexing body 20 inside the strain-generating body 20 in the radial direction with respect to the center plane C of the first pressure-receiving surface 23 and the second pressure-receiving surface 24 as an electric signal. 1 to 3, the dummy gauges d11 to d14 are not shown. The strain gauges g11 to g14 according to the present embodiment are examples of the first strain gauge or the second strain gauge according to the present invention. The bridge circuit 60 according to the present embodiment is an example of the first bridge circuit or the second bridge circuit according to the present invention.

  Further, the strain gauges g21 to g24 are connected to each other so as to form a bridge circuit 61. More specifically, the bridge circuit 61 is formed by strain gauges g21 to g24 and temperature compensating dummy gauges d21 to d24. As described above, since the strain gauges g21 to g24 are arranged on the outer side in the radial direction of the strain body main body 20 with respect to the center plane C of the first pressure receiving surface 23 and the second pressure receiving surface 24, the bridge circuit 61 is provided. Outputs the strain of the strain-flexing body 20 outside the strain-flexing body 20 in the radial direction with respect to the center plane C of the first pressure-receiving surface 23 and the second pressure-receiving surface 24 as an electric signal. 1 to 3, the dummy gauges d21 to d24 are not shown. The strain gauges g21 to g24 according to the present embodiment are examples of the first strain gauge or the second strain gauge according to the present invention. The bridge circuit 61 according to the present embodiment is an example of the first bridge circuit or the second bridge circuit according to the present invention.

  As shown in FIG. 4, the bridge circuit 60 and the bridge circuit 61 are electrically connected in parallel, and the output voltage of the bridge circuit 60 and the output voltage of the bridge circuit 61 are summed in parallel. Is output.

  A first output adjusting resistor Δr1 for adjusting the output of the bridge circuit 60 is provided on the output line on one side of the bridge circuit 60. Similarly, the output line on one side of the bridge circuit 61 is provided with a second output adjustment resistor Δr2 for adjusting the output of the bridge circuit 61. The first output adjustment resistor Δr1 and the second output adjustment resistor Δr2 of the present embodiment are examples of the adjustment resistor according to the present invention.

  The first output adjustment resistor Δr1 and the second output adjustment resistor Δr2 are provided to adjust the output sensitivity of the bridge circuit 60 and the output sensitivity of the bridge circuit 61. For example, even when an unbalanced load is applied to the first pressure receiving surface 23 (shown in FIG. 1) of the flexure body 20, there is no difference between the output voltage of the bridge circuit 60 and the output voltage of the bridge circuit 61. As described above, the size of the first output adjusting resistor Δr1 and the size of the second output adjusting resistor Δr2 are adjusted. Further, the size of the first output adjustment resistor Δr1 and the first output adjustment resistor Δr1 are set so that there is no difference between the output voltage of the bridge circuit 60 and the output voltage of the bridge circuit 61 due to variations in the bonding positions of the strain gauges g11 to g14 and g21 to g24. The magnitude of the two-output adjustment resistor Δr2 is adjusted.

  According to this embodiment, the strain gauges g11 to g14 and g21 to g24 are arranged in the hole portions 30A, 30B, 30C and 30D that form the opening 21a in the outermost surface 21 of the strain body main body 20, respectively. .. Therefore, since the work of attaching the strain gauges g11 to g14 and g21 to g24 to the strain body 10 can be performed from the opening 21a formed in the outermost surface 21 of the strain body body 20, the strain gauges g11 to g11 The workability of attaching g14 and g21 to g24 to the flexure element 10 can be improved.

  Further, according to the present embodiment, the openings 21a for mounting the strain gauges g11 to g14 and g21 to g24 are sealed by the metal diaphragm 40, so that the strain gauges g11 to g14 and g21 to g24 are exposed to the outside. Is suppressed. As a result, the strain gauges g11 to g14 and g21 to g24 are less likely to be affected by the external environment, and the environmental resistance of the load cell 1 can be improved.

  In the present embodiment, the metal diaphragm 40 is welded to the opening 21 a formed in a part of the flexure body 20. The welding length required to weld the metal diaphragm 40 to the opening 21a is the welding length required to weld an airtight member (for example, a cylindrical thin plate) to the entire circumference of the outermost surface 21 of the flexure body 20. Short compared to. As a result, stress is less likely to be concentrated in the welded portion, and damage to the load cell 1 from the welded portion is suppressed, as compared with the case where an airtight member is welded to the entire circumference of the outermost surface 21 of the strain-flexing body 20. Therefore, the environment resistance of the load cell 1 can be improved.

  Since the metal diaphragm 40 is flexible, when the load is applied to the first pressure receiving surface 23, it is unlikely to affect the deformation of the strain-flexing body 20. Further, since the metal diaphragm 40 is arranged so as not to overlap the first pressure receiving surface 23 in a top view, the load is supported by the metal diaphragm 40 when the load acts on the first pressure receiving surface 23. Hateful. As a result, the influence of the metal diaphragm 40 on the measurement accuracy of the load cell 1 can be suppressed.

  According to the present embodiment, the lead wires L of the strain gauges g11 to g14 for forming the bridge circuit 60 have the connecting holes 50A, 50B, 50C provided in the strain-flexing body main body 20 in which the opening 21a is sealed. , 50D. Similarly, the lead wires L of the strain gauges g21 to g24 for forming the bridge circuit 60 are connected through the connecting holes 50A, 50B, 50C, 50D provided in the strain-flexing body main body 20 in which the opening 21a is sealed. Has been done. As a result, the lead wire L for forming the bridge circuit 60 and the bridge circuit 61 is not exposed to the outside, and the bridge circuit 60 and the bridge circuit 61 are less likely to be affected by the external environment, so that the environmental resistance can be improved.

  According to the present embodiment, the output from the bridge circuit 60 and the output from the bridge circuit 61 are adjusted by the first output adjustment resistor Δr1 and the second output adjustment resistor Δr2. As a result, even if there is a difference in the output sensitivity between the bridge circuit 60 and the bridge circuit 61 due to inaccuracy of the mounting positions of the strain gauges g11 to g14, g21 to g24 or an unbalanced load, the measurement accuracy is improved. Can be improved.

  Further, when the flexure element 10 has a flat shape as in the present embodiment, when an eccentric load acts on the first pressure receiving surface 23 of the flexure element main body 20, the eccentric load of the flexure element main body 20 acts. There may be partial strain in some parts. Therefore, the flat flexure element 10 does not have a fixed stress neutral surface that is not affected by an unbalanced load. As described above, the load cell 1 of the present embodiment can improve the measurement accuracy even when an eccentric load is applied to the flexure element 10, and thus is particularly effective when the flexure element 10 has a flat shape. is there.

  The second portion 32 of the hole portions 30A, 30B, 30C, 30D in which the strain gauges g11 to g14, g21 to g24 are arranged is formed smaller than the first portion 31. Accordingly, the holes 21A, 30B, 30C are secured while the size of the opening 21a is secured for the work of attaching the strain gauges g11 to g14, g21 to g24 to the strain body 10 or the work of connecting the lead wire L. , 30D suppresses the decrease in strength of the load cell 1. As a result, the work of attaching the strain gauges g11 to g14, g21 to g24 to the strain element 10 or the work of connecting the lead wire L is facilitated, and the strength of the load cell 1 is reduced by the holes 30A, 30B, 30C, 30D. Can be suppressed.

  According to the present embodiment, the opening 21a formed in the outermost surface 21 of the strain-flexing body 20 is sealed by the metal diaphragm 40. Therefore, compared with the case where the opening 21a is sealed by resin or the like. , The environment resistance can be improved.

  In this embodiment, two bridge circuits, that is, the bridge circuit 60 and the bridge circuit 61, are formed, but the widths of the first pressure receiving surface 23 and the second pressure receiving surface 24 (dimensions in the radial direction of the flexure body 20). If is small, only one bridge circuit may be provided. In other words, the strain gauges g21 to g24 may not be provided. In this case, the strain gauges g11 to g14 are preferably arranged on the center plane C of the first pressure receiving surface 23 and the second pressure receiving surface 24.

(Second embodiment)
The load cell 101 of the second embodiment has the same configuration as that of the load cell 1 of the first embodiment, except for the shape of the flexure element 110, the configuration of the connecting hole, and the provision of strain gauges g31 to 34. In the second embodiment, components similar to those in the first embodiment are designated by the same reference numerals as those in the first embodiment, and detailed description thereof will be omitted.

  FIG. 5 is a perspective view of the load cell 101 according to the second embodiment of the present invention. FIG. 6 is a top view of the load cell 101 according to the second embodiment of the present invention. FIG. 7 is a sectional view taken along the line VII-VII of FIG.

[overall structure]
Referring to FIG. 5 to FIG. 7, the load cell 101 of the present embodiment has a substantially disk-shaped flat strain element 110, and strain gauges g11 to g14, g21 to g24, g31 to attached to the strain element 110. and g34. The load cell 101 of this embodiment is a disk type load cell. The load cell 101 of this embodiment is applicable to, for example, measurement of rolling load of a rolling mill.

  As shown in FIG. 6 and FIG. 7, the inner side surface 22 of the flexure body main body 120 of the present embodiment is a space which is a space for facilitating the wiring work of the strain gauges g11 to g14, g21 to g24, g31 to g34. A hole 126 is defined.

  As shown in FIG. 7, the flexure body main body 120 of the present embodiment includes a first opening 126a formed by the through hole 126 on one end surface (upper side in FIG. 7) of the flexure body main body 120. Further, the strain-flexing body main body 120 includes a second opening 126b formed in the end face on the other side (lower side in FIG. 7) of the strain-flexing body main body 120 by the through hole 126. The first opening 126a and the second opening 126b are sealed by a metal diaphragm 141. The metal diaphragm 141 is welded to the flexure body main body 120. The metal diaphragm 141 of the present embodiment is an example of the airtight member according to the present invention.

  As shown in FIG. 6, the flexure element 110 of the present embodiment includes a connecting portion 150A communicating with the hole 30A and the through hole 126, and a connecting portion 150B communicating with the hole 30B and the through hole 126. Equipped with. Further, the flexure element 110 of the present embodiment includes a connecting portion 150C communicating with the hole 30C and the through hole 126, and a connecting portion 150D communicating with the hole 30D and the through hole 126. The connecting portion 150A is coaxially aligned with the hole 30A. The connecting portion 150B is coaxially aligned with the hole 30B. The connecting portion 150C is coaxially aligned with the hole 30B. The connecting portion 150D is aligned with the hole 30D coaxially. Further, the connecting portions 150A, 150B, 150C and 150D radially extend from the through hole 126 in the radial direction of the strain-flexing body 120. Further, the extraction hole 13 of the present embodiment communicates with the through hole 126.

  In the present embodiment, the through hole 126 extending in the axial direction of the flexure body main body and two of the four connecting portions 150A, 150B, 150C, 150D extending in the radial direction of the flexure body main body 120 provide the present invention. The connecting hole is formed. Specifically, the connecting hole formed by the connecting portions 150A and 150B and the through hole 126 communicates with the hole portion 30A and the hole portion 30B. The connecting hole formed by the connecting portions 150A and 150C and the through hole 126 communicates with the hole portion 30A and the hole portion 30C. The connecting hole formed by the connecting portions 150A and 150D and the through hole 126 communicates with the hole portion 30A and the hole portion 30D. The connecting hole formed by the connecting portions 150B and 150C and the through hole 126 communicates with the hole portion 30B and the hole portion 30C. The connecting hole formed by the connecting portions 150B and 150D and the through hole 126 communicates with the hole 30B and the hole 30D. The connecting hole formed by the connecting portions 150C and 150D and the through hole 126 communicates with the hole 30C and the hole 30D.

  The strain gauges g11 to g14, g21 to g24, g31 to g34 of the present embodiment have holes 30A, 30B, 30C so as to detect strain in the thickness direction (vertical direction in FIG. 7) of the strain body main body 120. , 30D. As shown in FIG. 6, the strain gauges g11 to g14, g21 to g24, g31 to g34 are arranged so as to overlap the first pressure receiving surface 23 in a top view. The strain gauges g11 to g14, the strain gauges g21 to g24, and g31 to g34 are arranged at different positions in the depth direction of the hole portions 30A, 30B, 30C, 30D. The strain gauges g11 to g14 are arranged at approximately the same position in the radial direction of the strain body main body 120. The strain gauges g21 to g24 are arranged at approximately the same position in the radial direction of the strain-flexing body 120. The strain gauges g31 to g34 are arranged at approximately the same position in the radial direction of the strain body main body 120.

  In the hole portion 30A, a strain gauge g11 is arranged radially inward of the strain body main body 120 with respect to the center plane C of the first pressure receiving surface 23 and the second pressure receiving surface 24, and the first pressure receiving surface 23 and The strain gauge g21 is arranged so as to overlap the center plane C of the second pressure receiving surface 24. Further, in the hole portion 30A, a strain gauge g31 is arranged outside the center plane C of the first pressure receiving surface 23 and the second pressure receiving surface 24 in the radial direction of the strain-flexing body 120. In other words, the strain gauges g11, g21, g31 are arranged in this order from the radial inner side to the outer side of the flexure body main body 120.

  In the hole portion 30B, a strain gauge g12 is arranged radially inward of the strain-flexing body 120 with respect to the center plane C of the first pressure-receiving surface 23 and the second pressure-receiving surface 24. The strain gauge g22 is arranged so as to overlap the center plane C of the second pressure receiving surface 24. Further, in the hole 30B, a strain gauge g32 is arranged outside the center plane C of the first pressure receiving surface 23 and the second pressure receiving surface 24 in the radial direction of the strain-flexing body 120. In other words, the strain gauges g12, g22, g32 are arranged in this order from the radial inner side to the outer side of the flexure body main body 120.

  In the hole portion 30C, a strain gauge g13 is arranged radially inward of the strain body main body 120 with respect to the center plane C of the first pressure receiving surface 23 and the second pressure receiving surface 24, and the first pressure receiving surface 23 and The strain gauge g23 is arranged so as to overlap the center plane C of the second pressure receiving surface 24. Further, in the hole 30C, a strain gauge g33 is arranged outside the center plane C of the first pressure receiving surface 23 and the second pressure receiving surface 24 in the radial direction of the strain-flexing body 120. In other words, the strain gauges g13, g23, g33 are arranged in this order from the radial inner side to the outer side of the strain-flexing body 120.

  In the hole portion 30D, a strain gauge g14 is arranged radially inward of the strain body main body 120 with respect to the center plane C of the first pressure receiving surface 23 and the second pressure receiving surface 24, and the first pressure receiving surface 23 and The strain gauge g24 is arranged so as to overlap the center plane C of the second pressure receiving surface 24. Further, in the hole 30D, a strain gauge g34 is arranged outside the center plane C of the first pressure receiving surface 23 and the second pressure receiving surface 24 in the radial direction of the strain-flexing body 120. In other words, the strain gauges g14, g24, g34 are arranged in this order from the radial inner side to the outer side of the strain-flexing body 120.

  As shown in FIG. 7, lead wires L are connected to the strain gauges g11 to g14, g21 to g24, g31 to g34. For clarity, the lead wire L is not shown in FIGS. 5 and 6, and only the lead wire L connected to the strain gauge g11 is shown in FIG. 7.

  The lead wires L of the strain gauges g11 to g14 are connected through the connecting portions 150A, 150B, 150C, 150D and the through hole 126. Similarly, the lead wires L of the strain gauges g21 to g24 are connected to the connecting portions 150A, 150B, 150C, 150D and the through hole 126. The lead wires L of the strain gauges g31 to g34 are connected through the connecting portions 150A, 150B, 150C, 150D and the through hole 126. Further, the lead wires L of the strain gauges g11 to g14, g21 to g24, g31 to g34 are connected to the cable 11 through the take-out hole 13, and are pulled out from the cable pull-out fitting 12 to the outside of the strain-flexing body 120. Has been.

[Circuit configuration of load cell]
FIG. 8 is a circuit diagram of the load cell 101 according to the second embodiment.

  The strain gauges g31 to g34 are connected to each other so as to form a bridge circuit 162. More specifically, the bridge circuit 162 is formed by strain gauges g31 to g34 and temperature compensating dummy gauges d31 to d34. 5 to 7, the illustration of the dummy gauges d31 to d34 is omitted. The strain gauges g31 to g34 according to the present embodiment are examples of the first strain gauge or the second strain gauge according to the present invention. The bridge circuit 162 according to this embodiment is an example of the first bridge circuit or the second bridge circuit according to the present invention.

  As shown in FIG. 8, the bridge circuit 60, the bridge circuit 61, and the bridge circuit 162 are electrically connected in parallel, and the output voltage of the bridge circuit 60, the output voltage of the bridge circuit 61, and the bridge circuit The output voltage of the circuit 162 is parallel summed and output.

  A third output adjusting resistor Δr3 for adjusting the output of the bridge circuit 162 is provided on the output line on one side of the bridge circuit 162. The third output adjustment resistor Δr3 of the present embodiment is an example of the adjustment resistor according to the present invention.

  The second embodiment has the same effects as the first embodiment.

[Modification]
FIG. 9 is a perspective view of a load cell 201 according to a modified example of the second embodiment. FIG. 10 is a top view of the load cell 201 according to the modified example of the second embodiment of the present invention. 11 is a cross-sectional view taken along the line XI-XI of FIG.

  Referring to FIG. 9 to FIG. 11, the flexure element 210 according to the present modification includes four working holes 280 that communicate with the hole portions 30A, 30B, 30C, and 30D and extend in the axial direction of the flexure element body 220. .. As shown in FIG. 10, the four work holes 280 are arranged so as to overlap the strain gauges g11 to g14 in a top view. As shown in FIG. 11, the flexure body main body 220 of the present modified example includes a work opening 280 a formed in an end face on one side (upper side in FIG. 11) of the flexure body main body 220 by a work hole 280. The work opening 280a is sealed by a metal diaphragm 242. The metal diaphragm 242 is welded to the flexure body main body 220. The metal diaphragm 242 of the present embodiment is an example of the airtight member according to the present invention. Note that the metal diaphragm 242 is not shown in FIGS. 9 and 10.

  According to this modification, since the work of attaching the strain gauges g11 to g14 can be performed from the work hole 280, the workability of attaching the strain gauges g11 to g14 to the strain generating element 210 can be improved.

(Third Embodiment)
The load cell 301 of the third embodiment has the same configuration as the load cell 101 of the second embodiment, except for the shape of the flexure element 310. In the third embodiment, components similar to those in the second embodiment are designated by the same reference numerals as those in the second embodiment, and detailed description thereof will be omitted. FIG. 8 is referred to in the third embodiment.

  FIG. 12 is a perspective view of the load cell 301 according to the third embodiment of the present invention. FIG. 13 is a top view of the load cell 301 according to the second embodiment of the present invention.

  Referring to FIG. 12, the flexure element 310 of the present embodiment has a substantially rectangular flat plate-like flat shape. As shown in FIG. 12, in the present embodiment, the maximum dimension B in the direction orthogonal to the height direction of the flexure element 310 is the diagonal dimension of the flexure element 310.

  The flexure element 310 of the present embodiment includes a flexure element body 320 that is an elastic body, and a plurality of (three in the present embodiment) holes 330A, 330B, and 330C provided in the flexure element body 320. ..

  The flexure body main body 320 of the present embodiment includes a first outermost surface 321 extending along the longitudinal direction of the flexure body main body 320 and a first outermost surface 321 extending along the longitudinal direction of the flexure body main body 320. And a second outermost surface 322 (shown in FIG. 13) arranged on the opposite side. The first outermost surface 321 of the flexure body 320 has three openings 321a formed by the three holes 330A, 330B, and 330C, respectively. As shown in FIG. 13, three openings 322a are formed in the second outermost surface 322 of the flexure body 320 by the three holes 330A, 330B, and 330C, respectively. In addition, the first outermost surface 321 of the strain-flexing body 320 is provided with a cable pull-out opening 321b for pulling out the cable 11 to the outside of the strain-flexing body 320.

  The flexure body main body 320 of the present embodiment has a first pressure receiving surface 323 formed on one end side (upper side in FIG. 12) and a second pressure receiving surface 323 formed on the other side (lower side in FIG. 12). A surface (not shown). The first pressure receiving surface 323 and the second pressure receiving surface of this embodiment are rectangular flat plates.

  The holes 330A, 330B, and 330C of the present embodiment extend from the first outermost surface 321 of the flexure body 320 toward the second outermost surface 322. The holes 330A, 330B, and 330C are provided so as to penetrate the first outermost surface 321 and the second outermost surface 322 of the flexure body main body 320. As a result, three openings 321a are formed in the first outermost surface 321 of the flexure body 320, and three openings 322a are formed in the second outermost surface 322 of the flexure body 320. .. The three openings 321a formed in the first outermost surface 321 of the flexure body 320 and the three openings 322a formed in the second outermost surface 322 are sealed by a metal diaphragm 340. The metal diaphragm 340 is welded to the flexure body main body 320. Note that in FIG. 12, the illustration of the metal diaphragm 340 is omitted.

  The holes 330A, 330B, and 330C include a first portion 331 that forms an opening 321a in the first outermost surface 321 of the flexure body 320, and a second outermost surface 322 of the flexure body 320 from the first portion 331. And a second portion 332 extending toward. Further, the holes 330A, 330B, and 330C of the present embodiment include the third portion 333 that forms the opening 322a on the second outermost surface 322 of the flexure body 320. The first portion 331, the second portion 332, and the third portion 333 of the holes 330A, 330B, and 330C of this embodiment are in communication with each other.

  The first portion 331, the second portion 332, and the third portion 333 of the holes 330A, 330B, and 330C have a circular cross-sectional shape in a cross section orthogonal to the depth direction. The cross-sectional area of the first portion 331 and the third portion 333 of the holes 330A, 330B, and 330C that are orthogonal to the depth direction is larger than the cross-sectional area of the second portion 332 that is orthogonal to the depth direction. Further, as shown in FIG. 13, the first portion 331 and the third portion 333 of the holes 330A, 330B, 330C are arranged so as not to overlap with the first pressure receiving surface 323 of the flexure body 320 in a top view. ing.

  As shown in FIG. 13, the flexure element 310 of the present embodiment has a connecting portion 350A that communicates with the holes 330A and 330B and a connecting portion 350B that communicates with the holes 330B and 330C. The connecting portions 350A and 350B of this embodiment form a connecting hole according to the present invention.

  The connecting portion 350A communicates with the first portion 331 of the hole portion 330A of the flexure body 320 and the first portion 331 of the hole portion 330B. The connecting portion 350B communicates with the first portion 331 of the hole portion 330B and the first portion 331 of the hole portion 330C. The connecting portions 350A and 350B have openings formed on the outermost surfaces on both sides in the longitudinal direction of the flexure body main body 320. The openings formed by the connecting portions 350A and 350B on the outermost surfaces on both sides in the longitudinal direction of the flexure body 320 are closed by the plug 351.

  Further, the strain-flexing body 310 is provided with an extraction hole 313 provided so as to reach the connecting portion 350A from the cable pull-out opening 321b of the strain-flexing body main body 320. The extraction hole 313 connects the cable extraction opening 321b and the connecting portion 350A.

  The strain gauges g11 to g14, g21 to g24, g31 to g34 of the present embodiment are arranged in the hole portions 330A, 330B and 330C so as to detect strain in the thickness direction of the strain body main body 320. As shown in FIG. 13, the strain gauges g11 to g14, g21 to g24, g31 to g34 are arranged so as to overlap the first pressure receiving surface 323 in a top view. The strain gauges g11 to g14 of this embodiment are arranged in the hole portion 330A. The strain gauges g21 to g24 of the present embodiment are arranged in the hole portion 330B. The strain gauges g31 to g34 of the present embodiment are arranged in the hole portion 330C.

  As described above, the strain gauges g11 to g14 are arranged in the hole portion 330A. The strain gauges g11 to g14 of the present embodiment are arranged in this order from the first portion 331 to the third portion 333 of the hole portion 330A.

  As described above, the strain gauges g21 to g24 are arranged in the hole portion 330B. The strain gauges g21 to g24 of this embodiment are arranged in this order from the first portion 331 to the third portion 333 of the hole portion 330B.

  As described above, the strain gauges g31 to g34 are arranged in the hole portion 330C. The strain gauges g31 to g34 of the present embodiment are arranged in this order from the first portion 331 to the third portion 333 of the hole portion 330C.

  The lead wires of the strain gauges g11 to g14, g21 to g24, g31 to g34 are connected to the cable 11 through the extraction hole 313, and are drawn out of the strain body main body 320 from the cable drawing metal fitting 12. ..

  The third embodiment has the same effects as the first and second embodiments.

  Although specific embodiments of the present invention have been described above, the present invention is not limited to the above-described embodiments, and various modifications can be made within the scope of the present invention.

  For example, in the first embodiment, the circuit formed in the load cell has two adjustment resistors, but the present invention is not limited to this, and one adjustment resistor may be provided. In the second embodiment and the third embodiment, the circuit formed in the load cell has three adjustment resistors, but the present invention is not limited to this, and the two adjustment resistors may be provided.

  Further, in the first to third embodiments, the metal diaphragm is used to seal the opening, but other airtight member such as resin may be used. In this case, the load cell can be applied to applications where the usage environment is not severe.

DESCRIPTION OF SYMBOLS 1 ... Load cell 10 ... Strain element 11 ... Cable 12 ... Cable drawing metal fitting 13 ... Ejection hole 20 ... Strain element body 21 ... Outermost surface 21a ... Opening 21b ... Cable drawing opening 22 ... Inner side surface 23 ... First pressure receiving surface 24 ... 2nd pressure receiving surface 25 ... Hole wall 25a ... Bottom wall 25b ... Side wall 30A, 30B, 30C, 30D ... Hole part 31 ... 1st part 32 ... 2nd part 40 ... Metal diaphragm (airtight member)
50A, 50B, 50C, 50D ... Connection hole 60, 61 ... Bridge circuit 101 ... Load cell 110 ... Strain element 120 ... Strain element main body 126 ... Through hole 126a ... First opening 126b ... Second opening 142 ... Metal diaphragm ( (Airtight member)
150A, 150B, 150C, 150D ... Connection part 162 ... Bridge circuit 201 ... Load cell 210 ... Strain element 220 ... Strain element main body 242 ... Metal diaphragm (airtight member)
280 ... Work hole 280a ... Work opening 301 ... Load cell 310 ... Strain element 313 ... Ejection hole 320 ... Strain element body 321 ... First outermost surface 321a ... Opening 321b ... Cable drawing opening 322 ... Second outermost surface 323 ... 1st pressure receiving surface 324 ... 2nd pressure receiving surface 330A, 330B, 330C ... Hole part 331 ... 1st part 332 ... 2nd part 333 ... 3rd part 350A, 350B ... Connection part g11, g12, g13, g14 ... Strain gauge g21 , G22, g23, g24 ... Strain gauge g31, g32, g33, g34 ... Strain gauge

Claims (5)

Strain element,
A plurality of strain gauges attached to the strain body and forming at least one bridge circuit;
The strain body is
Having a pressure receiving surface , a strain-flexing body that is an elastic body,
An opening is formed in the outermost surface of the strain-flexing body main body provided in a portion projecting outward from the pressure-receiving surface, and a plurality of holes extending inward of the strain-flexing body main body,
A plurality of airtight members for sealing the respective openings of the plurality of holes,
The load cell, wherein the plurality of strain gauges are attached to hole walls of the flexure body that define the plurality of holes, respectively.   The load cell according to claim 1, wherein the flexure element includes at least one connection hole provided in the flexure element body and communicating with at least two of the plurality of holes. The at least one bridge circuit is
A first bridge circuit,
A second bridge circuit connected in parallel with the first bridge circuit,
The load cell according to claim 1, further comprising at least one adjusting resistor that adjusts an output from the first bridge circuit and an output from the second bridge circuit. The plurality of strain gauges,
A first strain gauge that is provided in each of the plurality of holes, and is disposed at a predetermined position in the depth direction of each of the plurality of holes,
A second strain gauge that is provided in each of the plurality of holes, and that is arranged at a position different from the first strain gauge in the depth direction of each of the plurality of holes,
The first bridge circuit is formed by the first strain gauge provided in each of the plurality of holes,
The load cell according to claim 3, wherein the second bridge circuit is formed by the second strain gauge provided in each of the plurality of holes. The plurality of holes,
A first portion forming the opening;
And a second portion extending from the first portion toward the inside of the strain-flexing body main body, in which at least one of the plurality of strain gauges is arranged,
The load cell according to any one of claims 1 to 4, wherein a cross-sectional area of a cross section of the first portion that intersects in the depth direction is larger than a cross-sectional area of a cross section of the second portion that intersects in the depth direction.

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