JP6474642B2 - ROBERVAL TYPE LOAD CELL AND MANUFACTURING METHOD THEREOF - Google Patents

Description

  The present invention relates to a so-called Robertal type load cell, and more particularly to a load cell having an overload prevention mechanism for preventing damage due to overload and a method for manufacturing the same.

  A so-called Robarval type load cell employs a Roberval mechanism that is not affected by the position of an object to be weighed, and is widely used for weighing. As such a load cell, there exists a thing of patent document 1, for example. The load cell described in this document includes a rectangular frame-shaped load cell main body and a rod-shaped stopper member having a circular cross section attached to the load cell main body. The load cell body includes an upper beam part located at the upper part, a lower beam part located at the lower part, a fixed part fixed to a stationary body such as the apparatus main body, and a movable part that receives external force in the vertical direction. Are combined to form a rectangular frame. A total of four strain gauges are attached to both ends of the outer wall surfaces of the upper beam portion and the lower beam portion.

  Further, a first through hole extending in parallel with the upper beam portion and the lower beam portion is formed in the fixing portion of the load cell body. On the other hand, a second through hole coaxial with the first through hole is formed in the movable part. One end portion of the stopper member is fixed to the first through hole, and the other end portion of the stopper member is inserted into the second through hole. Further, a gap of a predetermined size is formed between the outer peripheral surface of the other end of the stopper member and the inner peripheral surface of the second through hole.

  The load cell formed in this way is used as follows. First, when a load is applied to the movable part of the load cell body, the entire load cell is distorted. Along with this strain, strain gauges attached at four locations are near the connecting portion between the upper beam portion and the fixed portion, and near the connecting portion between the lower beam portion and the movable portion. extend. On the other hand, the strain gauges adhered near the connecting portion between the upper beam portion and the movable portion and near the connecting portion between the lower beam portion and the fixed portion are shrunk. Of course, as the load applied to the load cell increases, the degree of strain of the strain gauge also increases. Further, the strain gauge has a characteristic that the electric resistance changes depending on the degree of elongation or shrinkage. Therefore, if the electrical resistance of a strain gauge is converted into a voltage using a Wheatstone bridge circuit and this voltage value is acquired, the magnitude of the load applied to the load cell can be detected.

  However, since the Rovalval type load cell has the above-described configuration, when an excessive load is applied, the load cell is greatly distorted, which may damage the strain gauge. In order to prevent this, when an excessive load is applied to the movable part, the inner wall surface of the second through hole of the movable part is in contact with the stopper member, and the movable part is no longer displaced. Yes. This prevents an excessive load from being applied to the load cell.

JP 2010-249731 A

  By the way, in the above load cell, the stopper member is provided with a large-diameter portion having an outer diameter larger than that of the first through hole, and the large-diameter portion is fixed to the first through-hole. At that time, there are mainly two methods for fixing the large diameter portion to the first through hole. One is a shrink fitting method, in which the load cell body is heated to expand the diameter of the first through hole, and then the large diameter portion of the normal temperature or low temperature stopper member is inserted into the first through hole. Thereafter, when the temperature of the load cell body is lowered, the inner diameter of the first through hole is restored, so that the large diameter portion is fixed to the first through hole. Another method is a method of hitting the stopper member and press-fitting the large diameter portion of the stopper member into the first through hole.

  However, shrink fitting has a problem that it takes time to work because it is necessary to heat the load cell body. Further, the press-fitting has a problem that it is difficult to adjust the direction of the stopper member with respect to the load cell body, such as the stopper member being inserted obliquely with respect to the first through hole. In particular, in such a load cell, since the outer peripheral surface of the tip end portion of the stopper member must be arranged at a predetermined distance from the inner wall surface of the second through hole, if the direction of the stopper member is not adjusted accurately, There is a possibility that the tip portion contacts the inner wall surface of the second through hole and does not operate as a load cell.

  The present invention has been made to solve the above problems, and is a load cell having a stopper member for preventing overload that prevents damage due to overload, and the stopper member can be attached with high accuracy and ease. It is an object of the present invention to provide a robust load cell and a method for manufacturing the same.

  A first Roverval type load cell according to the present invention has a first beam portion having a first end portion and a second end portion and extending in a first direction, a first beam portion having a first end portion and a second end portion. A second beam portion extending in parallel with the first beam portion, a first connection portion connecting the first end portions of the first beam portion and the second beam portion, and a second end portion of the first beam portion and the second beam portion connected to each other. A load cell main body formed in a rectangular shape and having a first end portion and a second end portion and formed in a circular cross section extending in the first direction. A first through hole having a circular cross section extending in the first direction is formed in the first connecting portion, and the first end of the stopper member is fixed to the first through hole, A second through hole having a circular cross section coaxial with the first through hole is formed in the second connecting portion, and a stopper member is formed in the second through hole. The two end portions are inserted, and at the second end portion of the stopper member, the portion inserted into the second through hole of the second connecting portion is arranged so that a predetermined gap is generated from the inner wall surface of the second through hole, The first end portion of the stopper member has a fixed portion having a diameter larger than the inner diameter of the first through hole, is adjacent to the fixed portion and the second end portion in the axial direction, and is slightly smaller in diameter than the inner diameter of the first through hole. The stopper member is inserted into the first through hole of the load cell main body from the second end side, and the guide part has passed through the first through hole. Then, when the fixing portion is pressed into the first through hole to be fixed to the load cell main body, and the guide portion is inserted into the first through hole, the axis of the stopper member coincides with the axis of the first through hole. It is configured as follows.

  According to this configuration, the stopper member has the fixed portion having a diameter larger than the inner diameter of the first through hole and the guide portion having a diameter slightly smaller than the inner diameter of the first through hole. Have the following advantages. When the second end portion of the stopper member is inserted into the first through hole and the stopper member is advanced to the second through hole side, the guide portion is inserted into the first through hole. As described above, since the guide portion has a diameter slightly smaller than the inner diameter of the first through hole, when the guide portion is inserted into the first through hole, the axis of the stopper member is the axis of the first through hole. Match with the heart. When the stopper member is pressed toward the second connecting portion in this state, the fixed portion is press-fitted into the first through hole. Therefore, prior to press-fitting the fixed portion, the guide portion causes the axis of the stopper member to coincide with the first through hole, so that the stopper member is inserted obliquely without causing a mounting failure. The fixing part can be press-fitted. As a result, the mounting failure of the stopper member is improved and the yield is improved. In addition, it is possible to eliminate the re-installation work and the re-creation work, and the productivity can be improved. Therefore, the attaching operation of the stopper member can be performed accurately and easily. When the guide portion is inserted into the first through-hole, “the axis of the stopper member coincides with the axis of the first through-hole” does not require a complete coincidence. Sometimes, the stopper members need only coincide as long as they can be prevented from being inserted obliquely. This is the same in the following.

  In the first load cell, the difference between the inner diameter of the first through hole and the outer diameter of the guide portion can be 0.03 to 0.13 mm.

  In any of the first load cells described above, the length of the guide portion in the axial direction can be 50% or more of the length of the first through hole in the first direction.

  In any one of the first load cells, a protrusion extending in the first direction is formed on the outer peripheral surface of the guide portion, and the protrusion extending in the first direction is engaged with the inner wall surface of the first through hole. Grooves can be formed.

  In any one of the first load cells, a protrusion extending in the first direction is formed on the inner wall surface of the first through hole, and the protrusion is extended in the first direction on the outer peripheral surface of the fixing portion and the guide portion. A groove can be formed that engages with.

  A second robust load cell according to the present invention includes a first beam portion having a first end portion and a second end portion and extending in a first direction, and a first beam portion having a first end portion and a second end portion. A second beam portion extending in parallel with the first beam portion, a first connection portion connecting the first end portions of the first beam portion and the second beam portion, and a second end portion of the first beam portion and the second beam portion connected to each other. A load cell main body formed in a rectangular shape and having a first end portion and a second end portion and formed in a circular cross section extending in the first direction. A first through hole extending in the first direction is formed in the first connecting portion, and the first through hole has a circular cross section that opens to the outer wall surface of the first beam portion. The guide hole is formed adjacent to the guide hole in the axial direction on the second end side, smaller in diameter than the inner diameter of the guide hole, and coaxial with the guide hole. And a second through hole having a circular cross section coaxial with the first through hole is formed in the second connecting portion, and the second end of the stopper member is formed in the second through hole. The stopper member is provided at the first end, has a slightly smaller diameter than the inner diameter of the guide hole of the first through hole, and a larger diameter than the inner diameter of the fixed hole, and the fixed portion And a main body portion having a diameter smaller than the inner diameter of the fixing hole, and a portion inserted into the second through hole in the second end portion of the stopper member is an inner portion of the second through hole. The stopper member is inserted from the second end side into the first through hole of the load cell body, and after the fixing portion has passed through the guide hole, the fixing portion becomes the fixing hole. It is fixed to the load cell body by being press-fitted, and when the fixed part is inserted through the guide hole, Heart is configured to match the axis of the first through hole.

  According to this configuration, the first through hole of the first connecting portion has a guide hole having an inner diameter slightly larger than the outer diameter of the fixing portion of the stopper member, and a fixing hole having an inner diameter smaller than the outer diameter of the fixing portion. Therefore, there are the following advantages. When the left end portion of the stopper member is inserted into the first through hole and the stopper member is advanced to the second through hole side, the fixed portion is inserted into the guide hole. As described above, since the guide hole has an inner diameter slightly larger than the outer diameter of the fixed portion, the axis of the stopper member coincides with the axis of the first through hole when the fixed portion is inserted into the guide hole. To do. When the stopper member is pressed toward the second connecting portion in this state, the fixing portion is press-fitted into the fixing hole. Therefore, prior to the press-fitting of the fixed portion, the guide hole causes the axis of the stopper member to coincide with the first through-hole, so that the stopper member is inserted obliquely without causing a mounting failure. The fixing part can be press-fitted. As a result, the mounting failure of the stopper member is improved and the yield is improved. In addition, it is possible to eliminate the re-installation work and the re-creation work, and the productivity can be improved. That is, the attaching operation of the stopper member can be performed accurately and easily.

  In the second load cell, the difference between the outer diameter of the fixed portion and the inner diameter of the guide hole can be 0.03 to 0.13 mm.

  In any one of the second load cells, the second through-hole can be formed with a tapered surface that opens to the inner wall surface of the second connecting portion and increases in diameter as the inner wall surface is approached.

  The first method for manufacturing a load cell according to the present invention includes a first beam portion, a first end portion, and a second end portion having a first end portion and a second end portion and extending in a first direction. A second beam portion extending in parallel with the first beam portion; a first connection portion for connecting first ends of the first beam portion and the second beam portion; and a second end portion of the first beam portion and the second beam portion. A load cell body having a second connection portion that is connected to each other and extends in parallel with the first connection portion, and is formed in a rectangular shape, and the first connection portion includes a first circular cross-section extending in the first direction. A step of preparing a load cell body in which a second through-hole having a circular cross-section coaxial with the first through-hole is formed in the second connecting portion; and a first end and a second end A stopper member having a circular cross section, the first end portion of which is a fixed portion having a diameter larger than the inner diameter of the first through hole Preparing a stopper member having a guide portion coaxially adjacent to the fixed portion and the second end side in the axial direction, slightly smaller than the inner diameter of the first through hole, and coaxial with the fixed portion; After the second end portion of the stopper member is inserted into the first through hole of the load cell body, the stopper member is advanced through the first connecting hole side while the stopper member is advanced to the second connecting portion side. And a step of press-fitting the fixed portion into the first through hole in a state where the guide portion is inserted through the first through hole. .

  In the first load cell manufacturing method, the difference between the inner diameter of the first through hole and the outer diameter of the guide portion can be set to 0.03 to 0.13 mm.

  In any one of the first load cell manufacturing methods described above, the length of the guide portion in the axial direction can be 50% or more of the length of the first through hole in the first direction.

  The second method for manufacturing a load cell according to the present invention includes a first beam portion, a first end portion, and a second end portion having a first end portion and a second end portion and extending in a first direction. A second beam portion extending in parallel with the first beam portion; a first connection portion for connecting first ends of the first beam portion and the second beam portion; and a second end portion of the first beam portion and the second beam portion. A load cell body having a second connection portion that is connected to each other and extends in parallel with the first connection portion, and is formed in a rectangular shape, and the first connection portion includes a first circular cross-section extending in the first direction. A through hole is formed, and the first through hole is adjacent to the guide hole having a circular cross-section that opens to the outer wall surface of the first beam portion, and the guide hole and the second end side in the axial direction. A fixed hole having a circular cross section that is smaller than the inner diameter and formed coaxially with the guide hole, and the second connecting portion includes a first through hole and A step of preparing a load cell body in which a second through hole having a circular cross section of the shaft is formed, and a stopper member having a first end portion and a second end portion and formed in a circular cross section, A fixed portion that is provided at the end, slightly smaller than the inner diameter of the guide hole of the first through-hole and larger than the inner diameter of the fixed hole, and a fixed hole extending from the fixed portion toward the second end portion; A step of preparing a stopper member having a main body portion having a diameter smaller than the inner diameter of the second through-hole, and a second end portion of the stopper member inserted into the first through-hole of the load cell main body, The step of making the axis of the stopper member coincide with the axis of the first through hole by inserting the fixing portion into the guide hole while moving forward to the second connecting portion side, and the fixing portion is inserted into the guide hole. And pressing the fixing part into the fixing hole in a state. .

  In the second load cell manufacturing method, the difference between the outer diameter of the fixed portion and the inner diameter of the guide hole can be set to 0.03 to 0.13 mm.

  In any one of the above-described second load cell manufacturing methods, a tapered surface that opens to the inner wall surface of the second connecting portion and increases in diameter as it approaches the inner wall surface can be formed in the second through hole. .

  According to the present invention, the attaching operation of the stopper member can be performed accurately and easily.

1 is a perspective view of a load cell according to a first embodiment of the present invention. It is a front view of FIG. It is a front view which shows the manufacturing method of the load cell of FIG. It is the left view (a) and front view (b) of the load cell main body which concern on the other example of the load cell of FIG. It is a front view of the stopper member which concerns on the other example of the load cell of FIG. It is the left view (a) and front view (b) of the load cell main body which concern on the other example of the load cell of FIG. It is a front view of the stopper member which concerns on the other example of the load cell of FIG. It is a disassembled front view of the load cell which concerns on 2nd Embodiment of this invention. It is a front view which shows the manufacturing method of the load cell of FIG.

(A. First embodiment)
Hereinafter, a first embodiment of a load cell according to the present invention will be described with reference to the drawings. FIG. 1 is a perspective view of a load cell according to the present embodiment, and FIG. 2 is a front view of FIG. In the following, for convenience of explanation, the vertical direction in FIG. 2 is referred to as “up and down”, the horizontal direction in FIG. 2 is referred to as “left and right” or “horizontal”, and the paper direction in FIG. I do. However, the direction and direction of the load cell according to the present invention are not limited to this.

<1. Load cell>
As shown in FIG. 1, the load cell according to the present embodiment is a robust load cell, and includes a load cell main body 1 formed in a rectangular frame shape, and a rod-shaped stopper member 2 attached to the load cell main body. I have. Hereinafter, these members will be described in detail.
<1-1 Load cell body>

  As shown in FIGS. 1 and 2, the load cell main body 1 is formed in a rectangular shape by integrally connecting the upper beam portion 11, the lower beam portion 12, the first connecting portion 13, and the second connecting portion 14. ing.

  The upper beam part 11 is a part located in the upper part of the load cell main body 1, and is extended in a horizontal direction (1st direction). And the 1st connection part 13 extended below is connected with the left end part (1st end part) of the upper beam part 11, and the right end part (2nd end part) of the upper beam part 11 is connected with it. The 2nd connection part 14 extended below is connected. On the inner wall surface of the connecting portion between the upper beam portion 11 and the first connecting portion 13 and the inner wall surface of the connecting portion between the upper beam portion 11 and the second connecting portion 14, a groove-shaped notch 15 extending in the front-rear direction is provided. Each is formed. These notches 15 are formed in a circular arc shape, whereby the connecting portion is formed thin. And the strain gauge 3 is affixed on two positions corresponding to said notch part 15 among the outer wall surfaces of the upper beam part 11. FIG. In addition, the shape of the notch part 15 will not be specifically limited if a connection part can be formed thinly.

  The lower beam portion 12 is a portion that is positioned below the load cell body 1 and extends in parallel with the upper beam portion 11. And the lower end part of the 1st connection part 13 is connected with the left end part (1st end part) of the lower beam part 12, and the right end part (2nd end part) of the lower beam part 12 is connected with The lower end part of the 2nd connection part 14 is connected. The inner wall surface of the connecting portion between the lower beam portion 12 and the first connecting portion 13 and the inner wall surface of the connecting portion between the lower beam portion 12 and the second connecting portion 14 have the same shape as described above in the front-rear direction. Each extending cutout 15 is formed. The cut-out portions 15 form the connecting portion thinly. And the strain gauge 3 is affixed on the two positions corresponding to the said notch part 15 among the outer wall surfaces of the lower beam part 12. FIG.

  The 1st connection part 13 is located in the left side part of the load cell main body 1, and is a part extended in a perpendicular direction. That is, the first connecting portion 13 connects the left end portions of the upper beam portion 11 and the lower beam portion 12. Moreover, as shown in FIG. 1, the 1st connection part 13 is fixed in contact with the stationary body which is not displaced with respect to the ground, such as the main body of an apparatus, for example in the outer wall surface side. Therefore, even if a load in the vertical direction is applied to the load cell, the first connecting portion 13 is not displaced. Further, a first through hole 131 extending in the horizontal direction is formed in the central portion of the first connecting portion 13 in the vertical direction. The first through hole 131 has a circular cross section, and its axis extends in parallel to the upper beam portion 11 and the lower beam portion 12.

  The 2nd connection part 14 is located in the left side part of the load cell main body 1, and is a part extended in a perpendicular direction. That is, the second connecting portion 14 extends in parallel with the first connecting portion 13 and connects the right end portions of the upper beam portion 11 and the lower beam portion 12 to each other. The second connecting portion 14 is a weighing for placing an object to be weighed on its upper surface (connecting portion with the upper beam portion 11), lower surface (connecting portion with the lower beam portion 12), or outer wall surface. A table, a weighing container, or the like is attached, thereby receiving a load in the vertical direction and displacing in the vertical direction. Further, a second through hole 141 extending in the horizontal direction is formed at the central portion of the second connecting portion 14 in the vertical direction. The second through hole 141 has a circular cross section, and its axis coincides with the axis of the first through hole 131, and the inner diameter is the same as the inner diameter of the first through hole 131. That is, the first through hole 131 and the second through hole 141 are formed to have the same coaxial diameter.

  When the load cell main body 1 configured as described above receives a load on the second connecting portion 14, the second connecting portion 14 moves in the vertical direction while maintaining a parallel state with the first connecting portion 13. That is, the load cell main body 1 is displaced in a shape like a substantially parallelogram. This is because the connecting portions of the upper beam portion 11, the lower beam portion 12, the first connecting portion 13, and the second connecting portion 14 are formed thin by the above-described notches 15. Moreover, the material which comprises the load cell main body 1 can use aluminum etc., for example.

<1-2 Stopper member>
Next, the stopper member 2 will be described with reference to FIG. FIG. 3 is a front view showing a manufacturing process of the load cell according to the present embodiment.

  The stopper member 2 is a member for preventing damage due to overload. As shown in FIG. 3 (a), the stopper member 2 has a columnar shape with a circular cross section, and the columnar fixing portion 21, the guide portion 22, and the main body portion 23 are arranged from the left side. It is formed by being integrally connected in order. The fixing portion 21 is a portion that is press-fitted into the first through hole 131, and has a larger diameter than the first through hole 131. In addition, the axial length L1 of the fixing portion 21 is not particularly limited, but for example, 50% of the horizontal length L4 of the first through hole 131 in order to stably fix the first through hole 131 to the first through hole 131. The above is preferable, and may be longer than the length L4 of the first through hole 131. Furthermore, a taper surface 24 whose outer diameter decreases toward the right side is formed at the right end of the fixed portion 21, that is, at the connecting portion with the guide portion 22.

  The guide portion 22 is a portion for guiding when the stopper member 2 is inserted through the first through hole 131 as described later. The outer diameter of the guide portion 22 is slightly smaller than the first through hole 131, and is preferably smaller by 0.03 to 0.13 mm, for example, than the inner diameter of the first through hole 131. It is more preferable to make it 0.05 to 0.10 mm, and it is particularly preferable to make 0.07 to 0.98 mm. This is because, if the difference in diameter is smaller than 0.03 mm, it is difficult to insert the guide portion 22 into the first through hole 131, and it is necessary to apply a blow with a machine or the like, resulting in poor productivity. On the other hand, if it is larger than 0.13 mm, the gap between the two becomes too large. Therefore, when the difference between the diameters is as described above, the guide portion 22 can be inserted into the first through hole 131 with a relatively small force without hitting with a machine or the like. When inserted, the axis of the stopper member 2 can be made substantially coincident with the axis of the first through hole 131. Further, the length L2 in the axial direction of the guide portion 22 is not particularly limited, but is, for example, 50% or more of the length L4 in the horizontal direction of the first through hole 131 in order to stably guide the stopper member 2. Preferably, it is 70% or more, more preferably 90% or more. Furthermore, a tapered surface 25 whose outer diameter decreases toward the right side is formed at the right end of the guide portion 22, that is, at the connection portion with the main body portion 23.

  The main body portion 23 is formed to have a smaller diameter than the guide portion 22, and the right end portion is inserted through the second through hole 141. And the taper surface 26 is formed in the front-end | tip of the part penetrated by the 2nd through-hole 141 so that an outer diameter may become small (refer FIG. 2).

  The position of the stopper member 2 in the left-right direction with respect to the load cell body 1 is not particularly limited, but the left end surface of the fixing portion 21 may coincide with the outer wall surface of the first connecting portion 13, and the fixing portion 21 is the first portion. It may enter the inside of the through hole 131. Alternatively, the fixing portion 21 may protrude beyond the outer wall surface of the first connecting portion 13. Further, the left end portion of the stopper member 2 is formed so as not to protrude outward from the outer wall surface of the second connecting portion 14, but may protrude. However, if the left end portion of the stopper member 2 protrudes outward from the outer peripheral surface of the second connecting portion 14, it becomes an obstacle when attaching a weighing table or the like to the outer wall surface of the second connecting portion 14. There is a fear.

  Moreover, the stopper member 2 can use aluminum etc., for example. The stopper member 2 may be formed of the same material as the load cell main body 1 or may be formed of a different material.

<2. Manufacturing method of load cell>
Next, the manufacturing process of the load cell according to the present embodiment will be described with reference to FIG.

  First, as shown in FIG. 3A, the stopper member 2 is processed. Specifically, a lathe process is performed in which the stopper member 2 is rotated about the central axis and the side surface is cut with a tool or the like. In this way, the fixing portion 21, the guide portion 22, and the main body portion 23 are formed, and the tapered surfaces 24, 25, and 26 are also formed. Subsequently, the load cell main body 6 is processed. Specifically, the rectangular parallelepiped material is cut out with a drill or the like, and the upper beam portion 11, the lower beam portion 12, the first connection portion 13, the second connection portion 14, and the cutout portion 15 are formed. However, the load cell body 1 may be formed by separately manufacturing the upper beam portion 11, the lower beam portion 12, the first connecting portion 13, and the second connecting portion 14 and assembling them using screws or the like. Thereafter, a drill is passed from the outer wall surface side of the first connecting portion 13 or the outer wall surface side of the second connecting portion 14 to process the first through hole 131 and the second through hole 141 simultaneously. As a result, the first through hole 131 and the second through hole 141 that are coaxial with the same diameter are formed at the same time.

  Subsequently, as illustrated in FIG. 3B, the stopper member 2 is inserted into the load cell main body 1 from the outer wall surface side of the first connecting portion 13. Specifically, the front end of the main body portion 23 of the stopper member 2 is inserted into the first through hole 131 and further advanced toward the second through hole 141. At this time, the outer diameter of the main body portion 23 is smaller than the inner diameter of the second through-hole 141, and further, since the tapered surface 26 is formed at the tip of the main body portion 23, it is assumed that the stopper member 2 is inserted obliquely. Moreover, interference with the opening periphery of the 2nd through-hole 141 can be avoided, and it can insert in the 2nd through-hole 141. FIG.

  Thus, when the insertion of the stopper member 2 is continued and the guide portion 22 is inserted through the first through hole 131, the outer diameter of the guide portion 22 is only slightly smaller than that of the first through hole 131. The outer peripheral surface of 22 is generally engaged with the inner peripheral surface of the first through hole 131. As a result, the axis of the stopper member 2 substantially coincides with the axis of the first through hole 131. Further, even if the stopper member 2 is inserted obliquely before the guide portion 22 enters the first through hole 131, the insertion direction is corrected by inserting the guide portion 22 into the first through hole 131. Is done.

  If the stopper member 2 is further inserted from this state, the outer diameter of the fixing portion 21 is larger than that of the first through hole 131, so that the tapered surface 24 on the left side of the fixing portion 21 contacts the opening periphery of the first through hole 131. Therefore, in order to insert the fixing portion 21 into the first through hole 131, the fixing portion 21 is press-fitted into the first through hole 131 by, for example, hitting with a machine. As a result, as shown in FIG. 2, the stopper member 2 is fixed to the load cell main body 1 in a state where the axial center thereof coincides with the first through hole 131 and the second through hole 141. In addition, when the stopper member 2 protrudes from the first through hole 131 toward the outer wall surface, the portion may be cut. This is because the stopper member 2 functions as a stopper if the functional portion 231 is inserted into the second through hole 141 as described above. And if the strain gauge 3 is finally stuck in a predetermined position, the load cell concerning this embodiment will be completed.

<3. Use of load cell>
The load cell configured as described above is used as follows. First, when a load is applied to the second connecting portion 14 of the load cell main body 1, the entire load cell main body 1 is distorted. Along with this strain, the strain gauges 3 attached to the upper left and lower right of the strain gauges attached to the four locations extend, and the strain gauges 3 attached to the upper right and lower left shrink. Thereby, if the electrical resistance of the strain gauge 3 is converted into a voltage using a Wheatstone bridge circuit (not shown) and the voltage value is obtained, the magnitude of the load applied to the load cell can be detected.

  Further, the functional portion 231 of the main body portion 23 of the stopper member 2 is inserted inside the second through hole 141 so that a slight gap is generated. Therefore, when the second connecting portion 14 is displaced by the width of the gap, the inner peripheral surface of the second through-hole 141 comes into contact with the outer peripheral surface (functional portion 231) of the stopper member 2 in parallel, and the second connecting portion 14 moves. Is limited. Thereby, damage to the load cell (strain gauge 3) due to excessive load can be prevented.

  In addition, the force applied to the load cell may include a horizontal component. At this time, the load cell is displaced in the vertical direction while being twisted. On the other hand, according to this embodiment, since both the stopper member 2 and the second through hole 141 have a circular cross section, even if the load cell main body 1 is twisted, the stopper member 2 and the second through hole 141 The vertical gap (distance) is not changed. Therefore, regardless of whether or not the load cell main body 1 is twisted, the stopper member 2 always acts at the same displacement position. That is, according to the present embodiment, the stopper member 2 can function properly even when the load cell is twisted.

<4. Features>
As described above, when the load cell is manufactured, the first through hole 131 and the second through hole 141 are formed so that the cross sections thereof are concentric, and the stopper member 2 is finished to a predetermined outer diameter. Can be performed relatively easily. And as long as it is processed in this way, the stopper member 2 can be placed inside the second through hole 141 so that a gap is formed with the second through hole 141 by simply fitting the stopper member 2 into the first through hole 131. it can. Such an arrangement of the stopper member 2 can be realized only by a combination of a hole having a circular cross section and a cylinder. This is because the combination of a hole and a cylinder having a circular cross section matches the central axes of both with a higher accuracy than a combination of a hole having a rectangular cross section and another shape such as a prism. Therefore, also about the 2nd through-hole 141 which has the cross-sectional shape of a concentric circle with the 1st through-hole 131, the stopper member 2 and a central axis correspond with high precision.

  There are also the following advantages. The stopper member 2 according to the present embodiment includes a fixed portion 21 having an outer diameter larger than the inner diameter of the first through hole 131, a guide portion 22 having an outer diameter slightly smaller than the inner diameter of the first through hole 131, have. Therefore, when the guide portion 22 is inserted through the first through hole 131, the axis of the stopper member 2 coincides with the axis of the first through hole 131. When the stopper member 2 is pressed toward the second connecting portion 14 in this state, the fixing portion 21 is press-fitted into the first through hole 131. Therefore, prior to press-fitting the fixing portion 21, the guide portion 22 causes the axial center of the stopper member 2 to coincide with the first through hole 131, so that the stopper member 2 is inserted obliquely, etc. It is possible to press-fit the fixing portion 21 without the occurrence of. As a result, the mounting failure of the stopper member 2 is improved and the yield is improved. Further, it is possible to eliminate the reattachment work and the remanufacturing work, and the productivity can be improved. That is, the attaching operation of the stopper member 2 can be performed accurately and easily.

<5. Modification>
The first embodiment of the present invention has been described above. However, the present invention is not limited to the above-described embodiment, and various modifications can be made without departing from the spirit of the present invention.

<5-1>
In the above embodiment, the first through hole 131 and the second through hole 141 have the same diameter, but they do not necessarily have the same inner diameter. That is, as described above, as long as the relationship between the fixed portion 21 and the guide portion 22 of the stopper member 2 and the first through-hole 131 and the relationship between the main body portion 23 and the second through-hole 141 are satisfied, both penetrations are satisfied. The diameters of the holes 131 and 141 may be different.

<5-2>
In the said embodiment, although the 1st connection part 13 is fixed to a stationary body and the load is applied to the 2nd connection part 14, you may make this reverse. That is, the second connecting portion 14 can be fixed to a stationary body and a load can be applied to the first connecting portion 13. Even in this case, the load cell main body 1 can be displaced in a parallelogram shape and the load can be measured.

<5-3>
In order to insert the stopper member 2 through the first through hole 131 more stably, the stopper member 2 can be configured as follows. This point will be described with reference to FIGS. FIG. 4 is a left side view (a) and a front view (b) according to an example of the load cell main body, and FIG. 5 is a front view of a stopper member corresponding to the load cell main body of FIG.

  In this example, a key 27 extending in the axial direction is formed on the outer peripheral surface of the fixed portion 21 of the stopper member 2, and a key groove 132 corresponding to the key (projecting portion) 27 is formed in the first through hole 131. When the stopper member 2 is inserted into the first through hole 131, the stopper member 2 is advanced with the key 27 engaged with the key groove 132. Thereby, the shift | offset | difference at the time of insertion of the stopper member 2 can be prevented, and it can insert in the 1st through-hole 131 more stably. The formation positions of the key 27 and the key groove 132 are not particularly limited. That is, the key 27 may be at any position on the outer peripheral surface of the stopper member 2, and the key groove 132 only needs to be formed at a position corresponding to the key 27. Further, the key 27 can be provided not only on the fixed portion but also on the guide portion 22.

<5-4>
In order to insert the stopper member through the first through hole more stably, the stopper member can be configured as follows. This point will be described with reference to FIGS. FIG. 6 is a left side view (a) and a front view (b) according to an example of the load cell main body, and FIG. 7 is a front view of a stopper member corresponding to the load cell main body of FIG.

  In this example, a groove 28 extending in the axial direction is formed on the outer peripheral surface of the fixed portion 21 and the guide portion 22 of the stopper member 2, and a protrusion 138 that engages with the groove 28 is formed in the first through hole 131. The protrusion 138 can be formed by various methods. For example, the protrusion 138 can be formed by screwing a screw 139 from the front or rear surface of the load cell body 1 and projecting the tip of the screw 139 into the first through hole 131. . When the stopper member 2 is inserted into the first through hole 131, the stopper member 2 is advanced with the groove 28 engaged with the protrusion 138. Thereby, the shift | offset | difference at the time of insertion of the stopper member 2 can be prevented, and it can insert in the 1st through-hole 131 more stably. In addition, the formation position of the groove | channel 28 and the protrusion part 138 is not specifically limited.

<5-5>
In the stopper member 2 of the above embodiment, tapered surfaces 24, 25, and 26 are formed at the distal end of the fixed portion, the distal end of the guide portion, and the distal end of the main body portion 23. These tapered surfaces 24, 25, and 26 are This is not always necessary, and the stopper member 2 can be fixed even if these are not provided. However, when at least one of the tapered surfaces 24, 25, and 26 is formed, the stopper member 2 can be easily inserted into the first through hole 131 and the second through hole 141.

<5-6>
The outer diameter of the main body 23 of the stopper member 2 may not be constant and may be changed. However, the outer diameter of the functional part 231 inserted through the second through hole 141 must be constant.

(B. Second Embodiment)
Next, a second embodiment of the load cell according to the present invention will be described with reference to the drawings. FIG. 8 is an exploded front view of the load cell according to the present embodiment. In the following, for convenience of explanation, the vertical direction in FIG. 8 is referred to as “up / down”, the horizontal direction in FIG. 8 is referred to as “left / right” or “horizontal”, and the paper direction in FIG. I do. However, the direction and direction of the load cell according to the present invention are not limited to this.

  The load cell according to the second embodiment is different from the first embodiment in the configuration of the first through hole 131 and the second through hole 141 of the load cell main body 1 and the configuration of the stopper member 2, and therefore the same configuration is used. The same reference numerals are given and description thereof is omitted. Below, the stopper member 2 is demonstrated first, and the load cell main body 1 is demonstrated after that.

<1. Stopper member>
As shown in FIG. 8, the stopper member 2 according to the present embodiment has a columnar shape with a circular cross section, and the columnar fixing portion 21 and the main body portion 23 are integrated in this order from the left side. It is formed by connecting together. The fixing portion 21 is a cylindrical portion that is press-fitted into the first through hole 131. The main body 23 is formed in a columnar shape having a smaller diameter than the fixed portion 21, and the right end is inserted into the second through hole 141.

<2. Load cell body>
Next, the load cell main body 1 will be described. The first connecting portion 13 of the load cell body 1 is formed with a first through hole 131 having a circular cross section extending in the horizontal direction at a central portion in the vertical direction. The first through hole 131 includes a guide hole 133 that opens to the outer wall surface of the first connecting portion 13 and a fixing hole 134 that is adjacent to the second connecting portion 14 side of the guide hole 133. The inner diameter of the guide hole 133 is larger than the inner diameter of the fixed hole 134, and the guide hole 133 and the fixed hole 134 are formed coaxially. The inner diameter of the guide hole 133 is slightly larger than the outer diameter of the fixed portion 21 of the stopper member 2, and is preferably 0.03 to 0.13 mm larger than the outer diameter of the fixed portion 21, It is more preferable to enlarge 0.05 to 0.10 mm, and it is particularly preferable to increase 0.07 to 0.98 mm. This is because, if the difference in diameter is smaller than 0.03 mm, it becomes difficult to insert the fixed portion 21 into the guide hole 133, and it is necessary to apply a blow with a machine or the like, resulting in poor productivity. On the other hand, if it is larger than 0.13 mm, the gap between the two becomes too large. Therefore, when the difference in diameter between the two is as described above, the fixing portion 21 can be inserted into the guide hole 133 with a relatively small force without hitting with a machine or the like. Can be made substantially coincident with the axis of the first through hole 131.

  In addition, a tapered surface 135 having a diameter that increases toward the outer wall surface is formed at the end edge of the guide hole 133 that opens to the outer wall surface of the first connecting portion 13. On the other hand, in the guide hole 133, a tapered surface 136 is formed at a position adjacent to the fixed hole 134 so that the inner diameter becomes smaller toward the second connecting portion 14 side.

  The inner diameter of the fixing hole 134 is smaller than the outer diameter of the fixing portion 21 of the stopper member 2, and the fixing portion 21 is press-fitted into the fixing hole 134. In addition, the axial length L8 of the fixing hole 134 is not particularly limited, but in order to stably fix the fixing portion 21 of the stopper member 2, for example, the horizontal length L4 of the first through hole 131 is set. It is preferable that it is 50% or more.

  The second through hole 141 formed in the second connecting portion 14 is formed in a circular cross section coaxial with the first through hole 131. The second through hole 141 is formed with a tapered surface 143 that opens to the inner wall surface of the second connecting portion 14. The tapered surface 143 is formed so that the inner diameter increases as going to the inner wall surface side of the second connecting portion 14.

  In the second through hole 141, the inner diameter of the functional portion 144 other than the tapered surface is larger than the main body portion 23 of the stopper member 2, and when the main body portion 23 of the stopper member 2 is inserted into the second through hole 141. A gap having a predetermined size is formed between the outer peripheral surface of the main body portion 23 and the inner wall surface of the functional portion 144.

<3. Manufacturing method of load cell>
Next, the manufacturing process of the load cell according to the present embodiment will be described with reference to FIG. FIG. 9 is a front view showing a manufacturing process of the load cell according to the present embodiment.

  Here, the formation method of the 1st through-hole 131 and the 2nd through-hole 141 of the load cell main body 1 is demonstrated. First, the first through hole 131 and the second through hole 141 are simultaneously processed by passing a drill from the outer wall surface side of the first connecting portion 13 or the outer wall surface side of the second connecting portion 14. The diameter of the hole formed at this time corresponds to the above-described fixing hole 134 and the functional portion 144 of the second through hole 141. Thereafter, the first through hole 131 is expanded by a drill to form the guide hole 133 and the tapered surfaces 135 and 136. In addition, a tapered surface 143 is formed in the second through hole 141.

  Subsequently, the stopper member 2 is inserted into the load cell main body 1 from the outer wall surface side of the first connecting portion 13. Specifically, the tip of the main body 23 of the stopper member 2 is inserted into the first through hole 131 and further inserted toward the second through hole 141. At this time, the outer diameter of the main body portion 23 is smaller than the inner diameter of the second through hole 141, and the tapered surface 143 is formed in the second through hole 141. Therefore, the stopper member 2 has entered, for example, obliquely. However, it can be inserted into the second through hole 141.

  Thus, when the stopper member 2 continues to be inserted and the fixing portion 21 is inserted through the first through hole 141, the outer diameter of the fixing portion 21 is only slightly smaller than the guide hole 133 of the first through hole 131. Therefore, the outer peripheral surface of the fixed portion 21 is substantially engaged with the inner peripheral surface of the guide hole 133, whereby the axial center of the stopper member 2 substantially coincides with the axial center of the first through hole 131. Further, even if the stopper member 2 is inserted obliquely before the fixing portion 21 enters the guide hole 133, the insertion direction is corrected by inserting the fixing portion 21 into the guide hole 133.

  If the stopper member 2 is further inserted from this state, the outer diameter of the fixing portion 21 is smaller than the fixing hole 134 of the first through hole 131. Therefore, as shown in FIG. It contacts the tapered surface formed in the guide hole 133. Therefore, in order to insert the fixing portion 21 into the fixing hole 134, the fixing portion 21 is press-fitted into the fixing hole 134 by, for example, hitting with a machine. Accordingly, as shown in FIG. 9B, the stopper member 2 is fixed to the load cell main body 1 in a state where the axial center thereof coincides with the first through hole 131 and the second through hole 141. In addition, when the stopper member 2 protrudes from the first through hole 131 toward the outer wall surface, the portion may be cut. And if the strain gauge 3 is finally stuck in a predetermined position, the load cell concerning this embodiment will be completed.

<4. Use of load cell>
The load cell according to the second embodiment is used in the same manner as the load cell of the first embodiment.

<5. Features>
In the load cell according to the present embodiment, the first through hole 131 of the first connecting portion 13 has the guide hole 133 having an inner diameter slightly larger than the outer diameter of the fixing portion 21 of the stopper member 2, and the outer diameter of the fixing portion 21. The fixing hole 134 having a smaller inner diameter has the following advantages. That is, when the left end of the stopper member 2 is inserted into the first through hole 131 and the stopper member 2 is advanced to the second through hole 141 side, the fixing portion 21 is inserted into the guide hole 133. As described above, since the guide hole 133 has an inner diameter that is slightly larger than the outer diameter of the fixed portion 21, when the fixed portion 21 is inserted into the guide hole 133, the axis of the stopper member 2 is the first through hole. It coincides with the axis of 131. When the stopper member 2 is pressed toward the second connecting portion 14 in this state, the fixing portion 21 is press-fitted into the fixing hole 134. Therefore, prior to press-fitting the fixing portion 21, the guide hole 133 causes the axial center of the stopper member 2 to coincide with the first through-hole 131, so that the stopper member 2 is inserted obliquely or the like. The fixing part 21 can be press-fitted without performing. As a result, the mounting failure of the stopper member 2 is improved and the yield is improved. In addition, it is possible to eliminate the re-installation work and the re-creation work, and the productivity can be improved. That is, the attaching operation of the stopper member 2 can be performed accurately and easily.

<7. Modification>
As mentioned above, although one Embodiment of this invention was described, this invention is not limited to the said embodiment, A various change is possible unless it deviates from the meaning.

<7-1>
In the above embodiment, the fixed hole 134 of the first through hole 131 and the functional portion 144 of the second through hole 141 have the same diameter, but they do not necessarily have the same inner diameter. That is, as described above, as long as the relationship between the fixed portion 21 and the guide portion 22 of the stopper member 2 and the first through hole 131 and the relationship between the main body portion 23 and the second through hole 141 are satisfied, these The diameters may be different.

<7-2>
The load cell which concerns on the said embodiment may fix the 1st connection part 13 to a stationary body, may apply a load to the 2nd connection part 14, and may reverse this. That is, the second connecting portion 14 can be fixed to a stationary body and a load can be applied to the first connecting portion 13.

<7-3>
In order to insert the stopper member 2 through the first through hole 131 more stably, a key extending in the axial direction is formed on the outer peripheral surface of the fixing portion 21 of the stopper member 2 in order to insert the stopper member 2 more stably. In addition, a key groove corresponding to this key can be formed in the first through hole 131. Alternatively, a groove extending in the axial direction can be formed on the outer peripheral surface of the fixing portion 21 of the stopper member 2, and a protrusion engaging with the groove can be formed in the guide hole 133 of the first through hole 131.

<7-4>
In the load cell main body 1 of the above embodiment, tapered surfaces 135, 136, and 143 are formed on both ends of the guide hole 133 and on the inner wall surface side of the second through hole 141. However, these tapered surfaces 135, 136, and 143 are not necessarily formed. It is not necessary, and the stopper member 2 can be fixed even if these are not provided. However, when at least one of these tapered surfaces 135, 136, and 143 is formed, the stopper member 2 can be easily inserted into the first through hole 131 and the second through hole 141. In addition, when the tapered surface 143 is not formed in the second through-hole 141, instead of this, a tapered surface may be formed at the distal end portion of the main body portion 23 like the stopper member 2 of the first embodiment. Thereby, the same effect as that of forming the tapered surface 143 in the second through-hole 141 can be obtained.

<7-5>
The outer diameter of the main body 23 of the stopper member 2 may not be constant and may be changed. However, the outer diameter of the portion inserted through the second through hole 141 and corresponding to the functional portion 144 must be constant.

1 Load cell body 11 Upper beam part (first beam part)
12 Lower beam part (second beam part)
13 1st connection part 131 1st through-hole 132 Keyway (groove)
133 Guide hole 134 Fixed hole 138 Protrusion part 14 2nd connection part 141 2nd through-hole 143 Tapered surface 2 Stopper member 21 Fixing part 22 Guide part 23 Main body part 27 Key (projection part)
28 groove

Claims (14)

A first beam portion having a first end portion and a second end portion and extending in the first direction; a second beam portion having a first end portion and a second end portion and extending in parallel with the first beam portion; A first connecting portion connecting the first ends of the first beam portion and the second beam portion; and a first connecting portion connecting the second ends of the first beam portion and the second beam portion. A load cell body having a second connecting portion extending in parallel with the portion and formed in a rectangular shape;
A stopper member having a first end portion and a second end portion and formed in a circular cross section extending in the first direction;
With
A first through hole having a circular cross section extending in the first direction is formed in the first connecting portion, and the first end portion of the stopper member is fixed to the first through hole,
A second through hole having a circular cross section coaxial with the first through hole is formed in the second connecting part, and the second end of the stopper member is inserted into the second through hole,
The first end portion of the stopper member is adjacent to the fixing portion having a larger diameter than the inner diameter of the first through hole, the fixing portion and the second end portion in the axial direction, and the first through hole A guide portion that is slightly smaller in diameter than the inner diameter and formed coaxially with the fixed portion,
The second end portion of the stopper member includes a main body portion having a smaller diameter than the guide portion and coaxial with the guide portion,
In the second end portion of the stopper member, the portion that is inserted into the second through hole of the second connecting portion is arranged so that a predetermined gap is formed with the inner wall surface of the second through hole,
The stopper member is inserted into the first through hole of the load cell main body from the second end side, and after the guide portion has passed through the first through hole, the fixing portion becomes the first through hole. It is fixed to the load cell body by being press-fitted, and when the guide portion is inserted into the first through hole, the axis of the stopper member is configured to coincide with the axis of the first through hole. Roberval type load cell.   2. The robust load cell according to claim 1, wherein a difference between an inner diameter of the first through hole and an outer diameter of the guide portion is 0.03 to 0.13 mm.   3. The Robert load cell according to claim 1, wherein a length of the guide portion in an axial direction is 50% or more of a length of the first through hole in the first direction. A protrusion extending in the first direction is formed on the outer peripheral surface of the guide portion,
4. The robust load cell according to claim 1, wherein a groove that extends in the first direction and engages with the protrusion is formed on an inner wall surface of the first through hole. 5. A protrusion extending in the first direction is formed on the inner wall surface of the first through hole,
4. The Robert load cell according to claim 1, wherein a groove that extends in the first direction and engages with the protrusion is formed on outer peripheral surfaces of the fixed portion and the guide portion. 5. A first beam portion having a first end portion and a second end portion and extending in the first direction; a second beam portion having a first end portion and a second end portion and extending in parallel with the first beam portion; A first connecting portion connecting the first ends of the first beam portion and the second beam portion; and a first connecting portion connecting the second ends of the first beam portion and the second beam portion. A load cell body having a second connecting portion extending in parallel with the portion and formed in a rectangular shape;
A stopper member having a first end portion and a second end portion and formed in a circular cross section extending in the first direction;
With
A first through hole extending in the first direction is formed in the first connecting portion , and the first through hole has a guide hole having a circular cross section that opens to an outer wall surface of the first connecting portion , and the guide. A fixed hole having a circular cross section adjacent to the hole and the second end side in the axial direction, having a diameter smaller than the inner diameter of the guide hole and coaxial with the guide hole;
A second through hole having a circular cross section coaxial with the first through hole is formed in the second connecting part, and the second end of the stopper member is inserted into the second through hole,
The stopper member is provided at the first end, and has a fixed portion slightly smaller in diameter than the inner diameter of the guide hole of the first through hole and larger in diameter than the inner diameter of the fixed hole, and the fixed portion. A main body extending to the second end side and having a diameter smaller than the inner diameter of the fixing hole,
In the second end portion of the stopper member, the portion inserted into the second through hole is arranged so that a predetermined gap is formed with the inner wall surface of the second through hole,
The stopper member is inserted into the first through hole of the load cell body from the second end side, and after the fixing portion has passed through the guide hole, the fixing portion is press-fitted into the fixing hole. The load cell body is configured so that the axis of the stopper member coincides with the axis of the first through hole when the fixing portion is inserted into the guide hole.   The robust valve according to claim 6, wherein a difference between an outer diameter of the fixed portion and an inner diameter of the guide hole is 0.03 to 0.13 mm.   8. The Roverval type load cell according to claim 6, wherein the second through-hole is formed with a tapered surface that opens to an inner wall surface of the second connecting portion and increases in diameter as the inner wall surface is approached. . A first beam portion having a first end portion and a second end portion and extending in the first direction; a second beam portion having a first end portion and a second end portion and extending in parallel with the first beam portion; A first connecting portion connecting the first ends of the first beam portion and the second beam portion; and a first connecting portion connecting the second ends of the first beam portion and the second beam portion. A load cell body having a second connecting portion extending in parallel with the portion and formed in a rectangular shape, wherein the first connecting portion is formed with a first through hole having a circular cross section extending in the first direction. A step of preparing a load cell body in which a second through hole having a circular cross section coaxial with the first through hole is formed in the second connecting portion;
A stopper member having a first end portion and a second end portion and formed in a circular cross section, wherein the first end portion is a fixed portion having a diameter larger than the inner diameter of the first through hole, A fixed portion and the second end side are adjacent to each other in the axial direction, and include a guide portion that is slightly smaller than the inner diameter of the first through hole and coaxial with the fixed portion, and the second end portion is Providing a stopper member having a main body portion smaller in diameter than the guide portion and coaxially formed with the guide portion ;
After the second end portion of the stopper member is inserted into the first through hole of the load cell body, the guide member is moved to the first through hole while the stopper member is advanced to the second connecting portion side. Making the axis of the stopper member coincide with the axis of the first through hole by inserting,
Press-fitting the fixed portion into the first through hole in a state where the guide portion is inserted through the first through hole;
A method for manufacturing a ROBERVAL type load cell.   The method for manufacturing a Roberval load cell according to claim 9, wherein a difference between an inner diameter of the first through hole and an outer diameter of the guide portion is 0.03 to 0.13 mm.   11. The method for manufacturing a Robert load cell according to claim 9, wherein a length of the guide portion in an axial direction is 50% or more of a length of the first through hole in the first direction. A first beam portion having a first end portion and a second end portion and extending in the first direction; a second beam portion having a first end portion and a second end portion and extending in parallel with the first beam portion; A first connecting portion connecting the first ends of the first beam portion and the second beam portion; and a first connecting portion connecting the second ends of the first beam portion and the second beam portion. A load cell body having a second connecting portion extending in parallel with the portion and formed in a rectangular shape, wherein the first connecting portion is formed with a first through hole having a circular cross section extending in the first direction. The first through-hole is adjacent to the guide hole having a circular cross section that opens to the outer wall surface of the first connecting portion , the guide hole and the second end side in the axial direction, and the inner diameter of the guide hole And a fixed hole having a circular cross section formed coaxially with the guide hole, and the second connecting portion includes the first connection The second through-hole of the hole coaxial with a circular cross section is formed, the steps of: providing a load cell body,
A stopper member having a first end portion and a second end portion, and having a circular cross section, provided at the first end portion and having a diameter slightly smaller than the inner diameter of the guide hole of the first through hole And a fixing part having a diameter larger than the inner diameter of the fixing hole, and a main body part extending from the fixing part to the second end side and having a diameter smaller than the inner diameters of the fixing hole and the second through hole. Preparing a stopper member;
After the second end portion of the stopper member is inserted into the first through hole of the load cell body, the fixing portion is inserted into the guide hole while the stopper member is advanced toward the second connecting portion side. The step of aligning the axis of the stopper member with the axis of the first through hole,
In a state where the fixing portion is inserted through the guide hole, the step of press-fitting the fixing portion into the fixing hole;
A method for manufacturing a ROBERVAL type load cell.   The method for manufacturing a Roberval type load cell according to claim 12, wherein a difference between an outer diameter of the fixed portion and an inner diameter of the guide hole is 0.03 to 0.13 mm. 14. The Robert load cell according to claim 12, wherein the second through-hole is formed with a tapered surface that opens to an inner wall surface of the second connecting portion and increases in diameter as the inner wall surface is approached. Manufacturing method.