JP2010181242A - Load cell - Google Patents

Abstract

<P>PROBLEM TO BE SOLVED: To provide a load cell for simplifying a constitution, and accurately measuring a load. <P>SOLUTION: The load cell 100 includes: a first both end fixed beam 110 having a region P0 for receiving the load, and a region to which a strain gauge unit 150 is attached; and a pair of second both end fixed beams 120, 130 disposed on both sides of the first both end fixed beam 110, and having regions R1, R2 for receiving a reaction force corresponding to the load. Both the ends of the first both end fixed beam 110 and both the ends of a pair of the second both end fixed beams 120, 130 are integrally fixed. <P>COPYRIGHT: (C)2010,JPO&amp;INPIT

Description

  The present invention relates to a load cell.

  Generally, as a device for measuring a load, a device using a load cell is widely known. Hereinafter, a load cell having a plate-like planar structure according to a conventional example will be described.

(Conventional example 1)
A load cell according to Conventional Example 1 will be described with reference to FIGS. FIG. 13 is a plan view of a load cell according to Conventional Example 1. FIG. FIG. 14 is a side view showing a state when receiving a load in the load cell according to Conventional Example 1. FIG. 15: is a front view which shows a mode when the load in the load cell which concerns on the prior art example 1 is received.

  The load cell 600 according to the conventional example 1 has a U-shaped slit S6 formed in a plate-like member, whereby a cantilever portion 610 and a pair of both ends fixed arranged on both sides of the cantilever portion 610. It is the structure provided with the beam parts 620 and 630.

  In the load cell 600, a portion P0 that receives a load is provided in the cantilever beam portion 610, and strain gauges 651, 652, 653, and 654 are attached to the pair of both-end fixed beam portions 620 and 630. In addition, bolt through holes 641 and 642 for fixing the load cell 600 are provided further to the distal end side than the free end of the cantilever portion 610.

  In the load cell 600 configured as described above, the portions of the pair of bolt through holes 641 and 642 are fixed by the bolt B as shown in FIG. When receiving the load P, the cantilever beam portion 610 bends around a fixed portion on one side. As a result, the pair of both-end fixed beam portions 620 and 630 receives a force in the load P direction and generates a bending moment on the side where the cantilever beam portion 610 is fixed. In addition, along with this, on the side where the load cell 600 is fixed in the pair of both-end fixed beam portions 620 and 630, a support reaction force acts and a fixing moment is generated. Therefore, as shown in FIG. 14, the pair of both-end fixed beam portions 620 and 630 bend to form an S shape.

  For this reason, in the pair of both-end fixed beam portions 620 and 630, there are portions where compressive strain occurs and portions where tensile strain occurs on the front side, and portions where tensile strain occurs and tensile strain occur on the back side. There is a site to do. In the load cell 600 according to the conventional example 1, the strain gauges 651 and 653 are disposed at the site where the compressive strain is generated, and the strain gauges 652 and 654 are disposed at the site where the tensile strain is generated. Thereby, a load can be measured with a Wheatstone bridge circuit.

  However, in the load cell 600 according to the conventional example 1, since the both-end fixed beam portions 620 and 630 function as both-end fixed beams, the parts of the pair of bolt through holes 641 and 642 must be securely fixed. Therefore, in order to perform stable measurement, it is necessary to firmly fix this part and to take measures against the loosening of the bolt B over time.

  In the load cell 600 according to the conventional example 1, the load is received at the center in the width direction, and the electrical resistance value is detected by the strain gauges 651, 652, 653, and 654 at positions away from the center in the width direction. Therefore, there is a problem that a measurement error is likely to occur. This point will be described with reference to FIG.

  When a load is received at the center in the width direction, not only bending in the longitudinal direction of the beam but also bending in the width direction of the beam occurs. That is, as shown in FIG. 15, in the both-end fixed beam portions 620 and 630, bending occurs in the load P direction around the respective end portions on both sides in the width direction. Therefore, the electrical resistance values detected by the strain gauges 651, 652, 653, and 654 are affected by the bending in the width direction, and measurement errors are likely to occur. Therefore, in the case of the load cell 600 according to the conventional example 1, in order to reduce the influence of this measurement error, it is essential to dispose a strain gauge in each of the pair of both-end fixed beam portions 620 and 630. Usage is also limited. In addition, when a load is applied in an oblique direction, the bending direction in the width direction is different between the case of the both-end fixed beam portion 620 and the case of the both-end fixed beam portion 630, and the measurement error is further increased. In addition, since the load cell 600 is twisted depending on how the load is applied, the measurement error is further increased in this case.

(Conventional example 2)
A load cell according to Conventional Example 2 will be described with reference to FIGS. 16 and 17. FIG. 16 is a plan view of a load cell according to Conventional Example 2. FIG. 17: is a side view which shows a mode when the load in the load cell which concerns on the prior art example 2 is received.

  The load cell 700 according to the conventional example 2 is obtained by cutting a plate-shaped member into a shape shown in FIG. 16, thereby fixing the both-end fixed beam portions 710 and a pair of both-end fixed beam portions 710. The structure includes cantilever portions 720 and 730 and a pair of both-end fixed beam portions 740 and 750 disposed outside the pair of cantilever portions 720 and 730.

  The both-end fixed beam portion 710 is fixed integrally with the pair of cantilever portions 720 and 730 on one end side, and is fixed integrally with the pair of both-end fixed beam portions 740 and 750 on the other end side. ing.

  In the load cell 700, the pair of cantilever portions 720 and 730 are provided with portions P1 and P2 that receive loads, respectively, and the strain gauge 770 is attached to the both-end fixed beam portion 710. In addition, bolt through holes 761 and 762 for fixing the load cell 700 are provided in the pair of both-end fixed beam portions 740 and 750, respectively.

  In the load cell 700 configured as described above, the portions of the pair of bolt through holes 761 and 762 are fixed by the bolt B as shown in FIG. When receiving the load P, the pair of cantilever portions 720 and 730 bend around the fixed portion on one side. As a result, the both-end fixed beam portion 710 receives a force in the load P direction and generates a bending moment on the side where the pair of cantilever portions 720 and 730 are fixed. Accordingly, a force in the load P direction is received and a bending moment is generated on the side where the pair of both end fixed beam portions 740 and 750 of the both end fixed beam portion 710 is fixed.

  Here, the bending moments generated at both ends of the both-end fixed beam portion 710 have opposite signs. Therefore, as shown in FIG. 17, the both-ends fixed beam part 710 bends so that it may become S shape.

  Thereby, in the both ends fixed beam part 710, while the site | part which a compressive strain generate | occur | produces on the surface side, and the site | part which a tensile strain generate | occur | produce, the site | part which a compressive strain generate | occur | produces also on a back surface side Exists. Accordingly, the strain gauge 770 provided on the both-end fixed beam portion 710 can detect the electrical resistance value at the site where the compressive strain is generated and the electrical resistance value at the site where the tensile strain is generated.

  In the case of the load cell 700 according to the conventional example 2, since the strain gauge 770 is arranged at the center position in the width direction (intermediate position between the parts P1 and P2 receiving the load), as in the case of the conventional example 1. There is no problem of measurement error due to bending in the width direction of the beam.

  However, in the case of the load cell 700 according to the conventional example 2, since there are two portions P1 and P2 that receive the load, a mechanism that evenly applies the load to them is necessary. Further, also in the load cell 700 according to the conventional example 2, the parts of the pair of bolt through holes 761 and 762 must be securely fixed.

  In addition, there exists a technique disclosed by patent document 1, 2 as a related technique.

Japanese Patent No. 3493410 Japanese Patent No. 2977278

  An object of the present invention is to provide a load cell capable of measuring a load with high accuracy with a simple configuration.

  The present invention employs the following means in order to solve the above problems.

That is, the load cell of the present invention includes a first both-end fixed beam portion having a portion that receives a load and a portion to which a strain gauge is attached,
A pair of second both-end fixed beam portions that are disposed on both sides of the first both-end fixed beam portion and each have a portion that receives a reaction force against the load;
A load cell comprising:
Both ends of the first both-end fixed beam portions and both ends of the pair of second both-end fixed beam portions are integrally formed, respectively.

  In the present invention, “both sides” means both sides of the beam in the width direction, and “both ends” means both ends of the beam in the longitudinal direction. Further, the “both end fixed beam portion” in the present invention means a part where both ends function as a fixed beam. Here, “fixed beam” means a beam on which both a vertical reaction force and a fixed moment (reaction moment) act. Therefore, “fixed” in the “both end fixed beam portion” does not mean that the beam is fixed to another member or the like.

  According to the present invention, when a load is applied to the first both-end fixed beam portion, a reaction force against the load acts on each of the pair of second both-end fixed beam portions. Since both ends of the first both-end fixed beam portion are integrally formed with both ends of the pair of second both-end fixed beam portions, the load receiving portion is positive or negative at the both end portions. Produces the opposite moment. Thereby, in this 1st both ends fixed beam part, it bends so that the site | part which receives a load and the both ends may become S shape, respectively. Therefore, in this first both-end fixed beam portion, there are a portion where compressive strain is generated on the front side and a portion where tensile strain is generated, and a portion where compressive strain is generated on the back side and a portion where tensile strain is generated. Exists. Therefore, the electric resistance value of the portion where compressive strain is generated by the strain gauge and the electric force of the portion where tensile strain is generated by the strain gauge only on either the front side or the back side of the first both-end fixed beam portion. The resistance value can be detected.

  Moreover, in this invention, the structure by which the both ends of a 1st both ends fixed beam part and the both ends of a pair of 2nd both ends fixed beam part is each formed integrally is employ | adopted. Therefore, the free end side of the beam portion is securely fixed as in the case of a load cell that includes a beam portion that is configured with a free end at one end and that functions as the beam fixing portion. There is no problem that must be kept.

Here, the portion receiving the load and the portion receiving the reaction force are provided so as to be located on a straight line extending in a direction perpendicular to the longitudinal direction of the beam,
The distance between the part receiving the reaction force and the part receiving the load in one of the pair of second both-end fixed beam portions, and the distance between the part receiving the reaction force and the part receiving the load in the other are It may be configured to be equal.

  By doing so, the bending deformation in the width direction of the load cell can be made symmetric with respect to the portion receiving the load.

  The part that receives the load and the part to which the strain gauge is attached may be provided so as to be positioned in a straight line extending in the longitudinal direction of the beam.

  By doing so, the influence of the bending deformation in the width direction of the load cell can be suppressed when the electrical resistance value is detected by the strain gauge.

  By forming a pair of slits on the plate-like member, a portion between the pair of slits constitutes a first both-end fixed beam portion, and both sides of the pair of slits respectively form a second both-end fixed beam portion. Configure.

  Thereby, a load cell is obtained only by forming a pair of slits with respect to the plate-like member.

  The portion receiving the load is provided at a position biased toward one end of the first both-end fixed beam portion, and the position where the strain gauge is attached is between the portion receiving the load and the other end. It may be provided at a position.

  Thereby, when receiving a load in the first both-end fixed beam portion, the length in the longitudinal direction of one S-shaped portion among the S-shaped portions formed on both sides of the portion receiving the load is As compared with the case where the part to receive is set at the center in the longitudinal direction, it can be made longer. And by attaching the strain gauge to the side where the length of the longitudinal direction of this S-shaped part was lengthened, the length of the S-shaped part was the same, and the part which receives a load was set as the center of the longitudinal direction. The measurement accuracy can be increased compared to that of the device.

  In addition, said each structure can be employ | adopted combining as much as possible.

  As described above, according to the present invention, it is possible to measure a load with high accuracy with a simple configuration.

FIG. 1 is a plan view of a load cell according to an embodiment of the present invention. FIG. 2 is a side view of the load cell according to the embodiment of the present invention. FIG. 3 is a side view showing a state when a load is applied to the load cell according to the embodiment of the present invention. 4 is a shear force diagram (SFD) and a bending moment diagram (BMD) of the first both-end fixed beam portion when a load is applied to the load cell according to the embodiment of the present invention. . FIG. 5 shows a shear force diagram (SFD) and a bending moment diagram (BMD) of the second both-end fixed beam portion when a load is applied to the load cell according to the embodiment of the present invention. . FIG. 6 is a Wheatstone bridge circuit diagram. FIG. 7 is a schematic plan view of a weight scale according to the embodiment of the present invention. FIG. 8 is a circuit diagram for measuring body weight in the scale according to the embodiment of the present invention. FIG. 9 is a perspective view of the load cell according to the first embodiment of the present invention. FIG. 10 is a plan view of the load cell according to the first embodiment of the present invention. FIG. 11 is a cross-sectional view of the load cell according to the first embodiment of the present invention. FIG. 12 is a plan view of a load cell according to the second embodiment of the present invention. FIG. 13 is a plan view of a load cell according to Conventional Example 1. FIG. FIG. 14 is a side view showing a state when receiving a load in the load cell according to Conventional Example 1. FIG. 15: is a front view which shows a mode when the load in the load cell which concerns on the prior art example 1 is received. FIG. 16 is a plan view of a load cell according to Conventional Example 2. FIG. 17: is a side view which shows a mode when the load in the load cell which concerns on the prior art example 2 is received.

  The best mode for carrying out the present invention will be exemplarily described in detail below based on the embodiments and examples with reference to the drawings. However, the dimensions, materials, shapes, relative arrangements, and the like of the components described in these embodiments and examples are intended to limit the scope of the present invention only to those unless otherwise specified. Is not.

(Embodiment)
With reference to FIGS. 1-8, the load cell which concerns on embodiment of this invention is demonstrated.

<Configuration of load cell>
With reference to FIG.1 and FIG.2, the structure of the load cell which concerns on embodiment of this invention is demonstrated. FIG. 1 is a plan view of a load cell according to an embodiment of the present invention. FIG. 2 is a side view of the load cell according to the embodiment of the present invention.

  The load cell 100 according to the embodiment of the present invention includes a first both-end fixed beam portion 110 and a pair of second both-end fixed beam portions 120 and 130 disposed on both sides of the first both-end fixed beam portion 110.

  In the load cell 100 according to the present embodiment, a pair of slits S1 and S2 extending in parallel to each other are formed in a rectangular plate-like member (metal plate or the like). Thereby, the part between a pair of slits S1 and S2 constitutes a first both-end fixed beam part 110, and both sides of the pair of slits S1 and S2 constitute a second both-ends fixed beam part 120 and 130, respectively. Thus, both ends of the first both-end fixed beam portion 110 and both ends of the pair of second both-end fixed beam portions 120 and 130 are integrally formed.

Further, the load cell 100 according to the present embodiment is configured to be symmetric with respect to the center line M1 with respect to the longitudinal direction and also symmetric with respect to the center line M2 with respect to the lateral direction.

  And it is comprised so that the site | part P0 which receives a load, and the site | part in which the strain gauge unit 150 is attached may be provided in the 1st both ends fixed beam part 110. FIG. In this embodiment, the part P0 that receives the load is configured to be a position where the center line M1 and the center line M2 intersect. Further, the part to which the strain gauge unit 150 is attached is configured to be located on the center line M2. Accordingly, the portion P0 that receives the load and the portion to which the strain gauge unit 150 is attached are provided so as to be positioned in a straight line extending in the longitudinal direction of the beam in the first both-end fixed beam portion 110.

  Moreover, it is comprised so that site | part R1, R2 which receives the reaction force at the time of the load P with respect to the 1st both ends fixed beam part 110 may be provided in the 2nd both ends fixed beam part 120,130. In FIG. 2, reference numeral 200 denotes a support portion of a support member that supports the load cell 100 at the portions R <b> 1 and R <b> 2 that receive the reaction force and applies the reaction force to the load cell 100.

  Here, site | part R1, R2 which receives these reaction force is comprised so that it may be located on the centerline M1. Therefore, the part P0 receiving the load and the parts R1 and R2 receiving the reaction force are provided so as to be located on a straight line extending in a direction perpendicular to the longitudinal direction of the beam. Further, the distance between the part R1 that receives the reaction force in the second both-end fixed beam part 120 and the part P0 that receives the load, the part R2 that receives the reaction force in the second both-end fixed beam part 130, and the part P0 that receives the load Are configured to be equal in distance.

  In the present embodiment, as shown in FIG. 1, a case where the regions R1 and R2 that receive the reaction force are configured by straight portions extending across the entire width direction of the second both-end fixed beam portions 120 and 130. Indicated. However, for example, the reaction force may be received at one point in the center in the width direction of the second both-end fixed beam portions 120 and 130.

<Load cell mechanism>
In particular, the mechanism of the load cell 100 will be described with reference to FIGS. FIG. 3 is a side view showing a state when a load is applied to the load cell according to the embodiment of the present invention. 4 is a shear force diagram (SFD) and a bending moment diagram (BMD) of the first both-end fixed beam portion when a load is applied to the load cell according to the embodiment of the present invention. . FIG. 5 shows a shear force diagram (SFD) and a bending moment diagram (BMD) of the second both-end fixed beam portion when a load is applied to the load cell according to the embodiment of the present invention. .

  According to the load cell 100 according to the present embodiment, when a load P is applied to the first both-end fixed beam portion 110, a reaction force R against the load P acts on the pair of second both-end fixed beam portions 120 and 130, respectively. .

  Since both ends of the first both-end fixed beam portion 110 are fixed, a moment having a polarity opposite to that of the portion P0 receiving the load is generated at the both ends. Note that a moment M in FIG. 4 indicates a fixed moment.

  As described above, in the first both-end fixed beam portion 110, since the bending moment generated at both ends thereof is opposite to the moment at the portion P0 that receives the load, the positive and negative are reversed. The space is bent so as to have an S shape (see FIGS. 3 and 4). Therefore, in this first both-end fixed beam portion 110, there are a portion where compressive strain occurs and a portion where tensile strain occurs on the front side, and a portion where tensile strain occurs and tensile strain also occur on the back side. The site exists.

  Therefore, the electrical resistance value of the part where compressive strain is generated and the electrical resistance value of the part where tensile strain is generated are detected by the strain gauge only on either the front side or the back side of the first both-end fixed beam portion 110. can do. That is, as shown in FIG. 3, by attaching a strain gauge unit 150 having a pair of strain gauges in the vicinity of the center of the S-shaped portion of the first both-end fixed beam portion 110, a portion where compressive strain occurs is generated. It is possible to detect the electrical resistance value and the electrical resistance value at the site where tensile strain occurs. Note that, for example, the strain gauge unit 150 uses, for example, a thin film that serves as a base and a pair of strain gauges fixed, and one strain gauge is disposed at a position where compressive strain occurs, and the other strain gauge is formed. The gauge may be arranged at a position where tensile strain occurs.

  In addition, a reaction force R opposite to the load P acts on the second both-end fixed beam portions 120 and 130. Since both ends of the second both-end fixed beam portions 120 and 130 are also fixed, moments having positive and negative opposite to those of the portions R1 and R2 receiving the reaction force are generated at both ends. Note that a moment M in FIG. 5 indicates a fixed moment.

  In this way, also in the second both-end fixed beam portions 120 and 130, the bending moment generated at both ends thereof is opposite in positive and negative to the moment in the portions R1 and R2 that receive the reaction force. The space between R2 and both ends thereof is bent so as to have an S shape (see FIGS. 3 and 5).

  In addition, in this embodiment, it comprises so that the bending deformation in the 1st both ends fixed beam part 110 and the bending deformation in the 2nd both ends fixed beam part 120,130 may become symmetrical. More specifically, the lateral width of the first both-end fixed beam portion 110 is set to be approximately equal to the sum of the lateral width of the second both-end fixed beam portion 120 and the second laterally fixed beam portion 130. That is, the horizontal width of the first both-end fixed beam portion 110 is set to be approximately twice the horizontal width of each of the second both-end fixed beam portions 120 and 130. Thereby, the sum of the strength of the first both-end fixed beam portion 110, the strength of the second both-end fixed beam portion 120, and the strength of the second both-end fixed beam portion 130 is approximately equal, and the first end-fixed beam portion 110 is bent. The deformation and the bending deformation in the second both-end fixed beam portions 120 and 130 are symmetric.

<Load measurement with load cell>
In particular, with reference to FIG. 6, load measurement by the load cell 100 according to the embodiment of the present invention will be described. FIG. 6 is a Wheatstone bridge circuit diagram.

  When performing load measurement using a load cell, the Wheatstone bridge circuit shown in FIG. 6 is generally used. Since the load measuring method using the Wheatstone bridge circuit is a well-known technique, a detailed description thereof will be omitted.

  In FIG. 6, R1, R2, R3, and R4 in the figure indicate resistance values of the strain gauges, respectively. E represents the input voltage, and e represents the output voltage. In a state where the load P is not applied and the load cell 100 is not deformed, R1 = R2 = R3 = R4. The strain gauges corresponding to R1 and R3 are provided at the site where tensile strain occurs, and the strain gauges corresponding to R2 and R4 are provided at the site where compressive strain occurs. When the load P is applied to the load cell 100, compressive strain and tensile strain are generated as described above, and the resistance value of each strain gauge changes slightly. Thereby, the amount of strain is detected using the Wheatstone bridge circuit, and the load can be measured from the amount of strain. In FIG. 6, reference numerals 150a and 150b correspond to the strain gauge unit 150 having a pair of strain gauges.

<Application example>
In particular, a case where the load cell according to the embodiment of the present invention is used for a weight scale will be described with reference to FIGS. FIG. 7 is a schematic plan view of a weight scale according to the embodiment of the present invention. FIG. 8 is a circuit diagram for measuring body weight in the scale according to the embodiment of the present invention.

  In the case of the weight scale 300, generally, it is comprised from a rectangular parallelepiped housing | casing part and the leg part provided in the four corners, and load cell 100a, 100b, 100c, 100d is arrange | positioned at four leg parts, respectively. In the weight scale according to the present embodiment, one strain gauge unit 150a, 150b, 150c, and 150d is provided for each load cell 100a, 100b, 100c, and 100d.

  Here, in the circuit shown in FIG. 8, the electrical resistance value of the pair of strain gauges in the strain gauge unit 150a corresponds to R1 ′ and R2 ′, and the electrical resistance value of the pair of strain gauges in the strain gauge unit 150b is R2 ″, It corresponds to R3 ″, the electrical resistance value of the pair of strain gauges in the strain gauge unit 150c corresponds to R3 ′, R4 ′, and the electrical resistance value of the pair of strain gauges in the strain gauge unit 150d corresponds to R4 ″, R1 ″. To do. Further, when the load P is not applied and the load cell 100 is not deformed, all the electric resistance values are configured to be equal.

  Strain gauges corresponding to R1 ′, R1 ″, R3 ′, and R3 ″ are provided at a site where tensile strain occurs, and strain gauges corresponding to R2 ′, R2 ″, R4 ′, and R4 ″ generate compressive strain. It is provided at the site to be

Here, if R1 = R1 ′ + R1 ″, R2 = R2 ′ + R2 ″, R3 = R3 ′ + R3 ″, and R4 = R4 ′ + R4 ″, it is equivalent to the Wheatstone bridge circuit shown in FIG. Therefore, it goes without saying that the load (body weight) can be measured using the circuit shown in FIG.

<Excellent point of load cell according to this embodiment>
The load cell 100 according to the present embodiment employs a configuration in which both ends of the first both-end fixed beam portion 110 and both ends of the pair of second both-end fixed beam portions 120 and 130 are integrally fixed. . Therefore, the free end side of the beam portion is securely fixed as in the case of a load cell that includes a beam portion that is configured with a free end at one end and that functions as the beam fixing portion. There is no problem that must be kept.

  That is, in the load cell 100 according to the present embodiment, a structure and a mechanism for fixing the first both-end fixed beam portion 110 and the second both-end fixed beam portions 120 and 130 as the both-end fixed beams are used. do not need. Therefore, basically, it is only necessary to support the load cell 100 so that the reaction force is generated at the portions R1 and R2 receiving the reaction force in the second both-end fixed beam portions 120 and 130. Thereby, the structure for fixing the load cell 100 may be simple, and a measure for maintaining stable fixation is not necessary. Therefore, the durability is excellent and the measurement accuracy can be stabilized.

  Further, in the load cell 100 according to the present embodiment, the portion P0 that receives the load and the portion to which the strain gauge unit 150 is attached are positioned in a straight line extending in the longitudinal direction of the beam in the first both-end fixed beam portion 110. Provided. Therefore, when the electrical resistance value is detected by the strain gauge, the influence of the bending deformation in the width direction of the load cell 100 can be suppressed.

Furthermore, in the load cell 100 according to the present embodiment, the portion P0 that receives the load and the portions R1 and R2 that receive the reaction force are provided so as to be positioned on a straight line extending in a direction perpendicular to the longitudinal direction of the beam. And the distance between site | part R1 which receives the reaction force in the 2nd both ends fixed beam part 120, and the site | part P0 which receives load, site | part R2 which receives the reaction force in 2nd both ends fixed beam part 130, and site | part P0 which receives load Are configured to be equal in distance.

  Thereby, the bending deformation of the load cell 100 in the width direction can be made symmetric with respect to the portion P0 that receives the load. Therefore, when the electrical resistance value is detected by the strain gauge, the influence of the bending deformation in the width direction of the load cell 100 can be further suppressed.

  Further, the load cell 100 according to the present embodiment can be obtained simply by forming a pair of slits S1 and S2 extending in parallel with each other with respect to the plate-like member. Therefore, the configuration is simple and the manufacture is easy. In addition, the number of parts can be reduced, and thinning and miniaturization can be easily realized.

(Example)
Next, a more specific example of the load cell according to the embodiment of the present invention described above will be described. Since the basic configuration and mechanism are the same as those in the above-described embodiment, the description thereof will be omitted as appropriate.

<Example 1>
9 to 11 show a load cell according to Embodiment 1 of the present invention. FIG. 9 is a perspective view of the load cell according to the first embodiment of the present invention. FIG. 10 is a plan view of the load cell according to the first embodiment of the present invention. FIG. 11 is a cross-sectional view of the load cell according to the first embodiment of the present invention. FIG. 11 is a cross-sectional view taken along AA in FIG.

  The load cell 100X according to the present embodiment is also configured by a plate-like member (metal plate or the like), and a pair of slits S1X and S2X extending in parallel with each other are formed. A portion between the pair of slits S1X and S2X constitutes a first both-end fixed beam portion 110X, and both sides of the pair of slits S1X and S2X constitute a second both-end fixed beam portion 120X and 130X, respectively. Similarly to the above embodiment, both ends of the first both-end fixed beam portion 110X and both ends of the pair of second both-end fixed beam portions 120X and 130X are integrally formed. is there.

  Further, the load cell 100X according to the present embodiment is also configured to be a target with respect to the center line with respect to the short direction. However, the load cell 100X according to the present embodiment is not configured to be symmetric with respect to the center line with respect to the longitudinal direction. This point will be described later.

  And in the load cell 100X which concerns on a present Example, the taper hole 111 used as the site | part which receives a load is provided in the 1st both ends fixed beam part 110X. By applying a load to the sphere with the sphere fitted in the tapered hole 111 or applying a load with a spherical (hemispherical) tip, the position where the load is applied to the load cell 100X is shifted. Can be suppressed.

  In the load cell 100X according to the present embodiment, the pair of second both-end fixed beam portions 120 and 130 are provided with projecting portions 121 and 131 that project on both sides, respectively. The pair of protrusions 121 and 131 are provided with through holes 121a and 131a, respectively. These through holes 121a and 131a are provided for fixing or positioning the load cell 100X, such as bolts and pins.

Thus, after providing the protrusion parts 121 and 131, the reason why the through holes 121a and 131a for fixing the load cell 100X to the protrusion parts 121 and 131 are provided will be described.

  In the load cells 100 and 100X according to the embodiments and examples of the present invention, when a load is applied, as shown in FIG. 3 referred to in the above embodiment, the portions other than the portion receiving the reaction force are in the direction in which the load is applied. It must be installed in a deformable state.

  Therefore, when the configuration in which the portions R1 and R2 that receive the reaction force are provided on the main body of the beam portion in the second both-end fixed beam portions 120 and 130 as in the load cell 100 according to the above embodiment, the position of the load cell 100 is adopted. Deviation countermeasures are required. That is, as described above, in the load cell 100 according to the above embodiment, the load cell 100 may be supported by the portions R1 and R2 that receive the reaction force in the second both-end fixed beam portions 120 and 130. If only the load cell 100 is supported, the load cell 100 rotates in the plane direction or the load cell 100 rotates around the center line M1. Therefore, it is necessary to prevent these rotations. For example, when the load cell 100 tries to rotate around the load cell 100, a stopper that prevents the end of the load cell 100 from abutting and preventing the load cell 100 from rotating must be provided.

  On the other hand, in the case of the load cell 100X according to the present embodiment, only the protruding portions 121 and 131 are supported, and the direction in which the load is applied in the other portions only needs to be set as a space region. As a result, the load cell 100X can be flexibly deformed at portions other than the protruding portions 121 and 131 in the first both-end fixed beam portions 110X and the pair of second both-end fixed beam portions 120 and 130 without being displaced. Become.

  Further, in the load cell 100X according to the present embodiment, the portion receiving the load (corresponding to the position of the tapered hole 111) is biased to one end side (upper side in FIG. 10) of the first both-end fixed beam portion 110X. In the position. The strain gauge unit 150X is configured to be attached at a position between the portion receiving this load and the other end.

  By configuring in this way, in the first both-end fixed beam portion 110X, when receiving a load, among the S-shaped portions formed on both sides of the portion that receives the load, the longitudinal direction of one S-shaped portion Can be made longer than the case where the portion receiving the load is set at the center in the longitudinal direction. And a measurement gauge can be further improved by attaching a strain gauge to the side which lengthened the length of the longitudinal direction of this S-shaped part.

  That is, the shorter the length of the portion that becomes S-shaped when subjected to a load, the greater the rate of change in strain with respect to the longitudinal direction and the rate of change in electrical resistance value associated therewith. The longer the length, the smaller the rate of change. Here, the error in the mounting position of the strain gauge affects the rate of change thereof, and the smaller the rate of change, the smaller the effect of the error in the mounting position. Therefore, the longer the length of the S-shaped portion, the less the influence of the strain gauge mounting position error, and the measurement accuracy can be increased.

  From the above, in the case of the load cell 100X according to the present embodiment, even when the load cell 100X is downsized, it is possible to ensure the length of the S-shaped portion when receiving a load. It is possible to achieve both downsizing and measurement accuracy.

Also in the case of the load cell 100X according to the present embodiment, the portion that receives the load (corresponding to the position of the tapered hole 111) and the portion that receives the reaction force (corresponding to the positions of the through holes 121a and 131a) It is provided so as to be positioned on a straight line extending in a direction perpendicular to the direction. The distance between the through hole 121a and the tapered hole 111, the through hole 131a, and the tapered hole 11 are as follows.
The distance between 1 is equal to each other. Therefore, as in the case of the load cell 100 according to the above-described embodiment, when the electrical resistance value is detected by the strain gauge, the influence of the bending deformation in the width direction of the load cell 100X can be suppressed.

<Example 2>
FIG. 12 shows a second embodiment of the present invention. FIG. 12 is a plan view of a load cell according to the second embodiment of the present invention. As described in the application example of the above-described embodiment, when the load cell is used for a weight scale, it is common to provide load cells at four locations. Therefore, for example, a configuration using four load cells 100X according to the first embodiment can be employed. However, as described above, the load cell can be configured by forming a pair of slits extending in parallel with each other on the plate-like member. That is, if a plurality of slits are formed in the plate-like member, a plurality of load cells can be formed in one plate-like member.

  Therefore, in this embodiment, a case will be described in which load cells are formed at four locations on one plate-like member and applied to a weight scale.

  That is, in the load cell 400 for weight scale according to the present embodiment, four load cells 100a, 100b, 100c, and 100d are provided on one plate-like member (metal plate or the like).

  These four load cells 100a, 100b, 100c, and 100d include a pair of slits S1 and S2 extending in parallel with each other and a pair of U-shaped slits S3 provided so as to surround them. Provided by forming S4. In the load cells 100a, 100b, 100c, and 100d according to the present embodiment, the portion between the pair of slits S1 and S2 constitutes the first both-end fixed beam portion 110, and both sides of the pair of slits S1 and S2 are respectively The second both-end fixed beam portions 120 and 130 are configured. Thus, the basic configuration is the same as that of the load cell 100 according to the above embodiment.

  In the case of the load cells 100a, 100b, 100c, and 100d according to the present embodiment, the second both-end fixed beam portions 120 and 130 are positioned and fixed. No positioning measures are required.

100, 100a, 100b, 100c, 100d, 100X Load cell 110, 110X First fixed beam portion 111 Tapered hole 120, 130, 120X, 130X Second fixed beam portion 121, 131 Protruding portion 121a, 131a Through hole 150, 150a , 150b, 150c, 150d, 150X Strain gauge unit 300 Weight scale 400 Weight scale load cell M1 Center line M2 Center line P Load P0, P1, P2 Part receiving load R Reaction force R1, R2 Part receiving reaction force S1, S2 , S1X, S2X slit S3, S4 slit

Claims (5)

A first both-end fixed beam portion having a portion to receive a load and a portion to which a strain gauge is attached;
A pair of second both-end fixed beam portions that are disposed on both sides of the first both-end fixed beam portion and each have a portion that receives a reaction force against the load;
A load cell comprising:
A load cell characterized in that both ends of the first both-end fixed beam portions and both ends of the pair of second both-end fixed beam portions are integrally formed. The portion receiving the load and the portion receiving the reaction force are provided so as to be positioned on a straight line extending in a direction perpendicular to the longitudinal direction of the beam,
The distance between the part receiving the reaction force and the part receiving the load in one of the pair of second both-end fixed beam portions, and the distance between the part receiving the reaction force and the part receiving the load in the other are The load cell of claim 1, wherein the load cells are configured to be equal.   3. The load cell according to claim 1, wherein the portion receiving the load and the portion to which the strain gauge is attached are provided so as to be positioned in a straight line extending in the longitudinal direction of the beam.   By forming a pair of slits on the plate-like member, a portion between the pair of slits constitutes a first both-end fixed beam portion, and both sides of the pair of slits respectively form a second both-end fixed beam portion. The load cell according to claim 1, 2 or 3, wherein the load cell is configured.   The portion receiving the load is provided at a position biased toward one end of the first both-end fixed beam portion, and the position where the strain gauge is attached is between the portion receiving the load and the other end. The load cell according to any one of claims 1 to 4, wherein the load cell is provided at a position.

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