JP6346052B2 - Load cell - Google Patents

Description

  The present invention relates to a parallelogram type load cell used in various weighing devices such as weighing hoppers, weighing conveyors, weighing tanks, and the like, and more particularly, to a load cell having an overload prevention mechanism for preventing damage due to an excessive load load. .

  As a parallelogram type load cell having such an overload prevention mechanism, for example, in Patent Document 1, one end of a cylindrical stopper member is fixed to the fixing portion side of a parallelogram type load cell, while the other end is fixed. And inserted into the circular hole formed on the movable part side so that a gap is formed between the inner peripheral surface of the circular hole and displaced by the contact between the outer peripheral surface of the stopper member and the inner peripheral surface of the circular hole. Is regulated so that excessive load is not applied.

  In Patent Document 2, a stopper pin having a cylindrical part is fixed to a fixed part of a parallelogram load cell, and the cylindrical part extending to the movable part is fixed to the circular hole formed in the movable part. A stopper pin is inserted so that a gap is formed between the cylindrical portion of the pin and the inner peripheral surface of the circular hole, and displacement is restricted by contact between the outer peripheral surface of the stopper pin and the inner peripheral surface of the circular hole. In order to prevent excessive load, it is described.

  In Patent Documents 1 and 2, the stopper member and the stopper pin are the fixed part of the parallelogram type load cell, the movable part, the upper beam part that connects the fixed part and the upper part of the movable part, and the fixed part and the movable part. It arrange | positions in the internal space enclosed by the lower beam part which connects lower parts.

  By the way, for example, as shown in Patent Document 3, the load cell has another strain generating portion or waterproofing in an internal space surrounded by the fixed portion, the movable portion, and the upper and lower beam portions of the parallelogram load cell. Some have a seal, or some have a portion connecting upper and lower beam portions in the internal space, as shown in FIG.

JP 2010-249731 A Utility Model Registration No. 3180316 U.S. Pat. No. 4,488,611 JP 7-239283 A

  In the above Patent Documents 1 and 2, there are the following problems. That is, in order to accurately realize the gap between the outer peripheral surface of the cylindrical stopper member and the inner peripheral surface of the circular hole, the accuracy of the outer dimensions of the cylindrical stopper member, the accuracy in the longitudinal direction, The accuracy of the circular holes and the relative positional relationship so that the gaps are uniform must be finished within the specified range, but the assembly accuracy within the specified range can be easily achieved due to machining errors. Therefore, the gap, in other words, the load-bearing characteristics as a stopper will vary.

  Further, as described above, in order to dispose the stopper member or the like in the internal space surrounded by the fixed portion, the movable portion, and the upper and lower beam portions of the parallelogram load cell, the above Patent Documents 3, 4 and the like are used. As described above, there is a problem that a stopper member or the like cannot be provided in a load cell in which another strain-generating portion or a connecting portion or the like exists in the internal space.

  The present invention has been made by paying attention to the above situation, and can prevent overload without using an internal space surrounded by a fixed part, a movable part, and upper and lower beam parts, An object of the present invention is to provide a load cell with reduced variation in load characteristics.

  In order to achieve the above object, the present invention is configured as follows.

(1) The load cell of the present invention connects the fixed portion, the movable portion that can be displaced, the upper beam portion that connects the fixed portion and the upper portions of the movable portion, and the lower portions of the fixed portion and the movable portion. Comprising a strain body made of a metal material integrally having a lower beam portion
A stopper that regulates displacement of the movable part by extending from the fixed part side to the lower side of the lower beam part and the movable part or to the upper side of the upper beam part and the movable part;
The stopper is formed by separating the strain body from the lower beam portion or the upper beam portion by a through groove penetrating the strain body in the thickness direction, and separated from the movable portion,
The movable portion and the stopper have opposing surfaces that face each other in the vertical direction across the through groove, and regulate the downward displacement and the upward displacement of the movable portion between the opposing surfaces, respectively. A stopper gap is formed.

  According to the load cell of the present invention, since the gap for the stopper is formed between the opposing surfaces of the movable part and the stopper, when an excessive load load is applied, the stopper is moved downward and upward of the movable part. Displacement can be regulated to prevent breakage of the strain generating portion of the load cell. Further, the stopper extends from the fixed portion side to the lower side of the lower beam portion and the movable portion, or to the upper side of the upper beam portion and the movable portion, that is, the stopper is fixed to the fixed portion, the movable portion, and the upper beam portion. And since it is not arranged in the internal space surrounded by the lower beam part, the internal space can be used effectively other than the stopper.

  Moreover, the stopper extending from the fixed portion side to the movable portion side is formed by being separated from the lower beam portion or the upper beam portion and separated from the movable portion by a through groove penetrating in the thickness direction of the strain generating body. In other words, since the stopper is formed integrally with the strain generating body by forming a through groove in the strain generating body, the stopper is formed by assembling a cylindrical stopper member or the like into the circular hole of the parallelogram load cell. Compared to the configuration that has many variations such as the processing accuracy of the outer shape of the stopper member, the processing accuracy of the inner surface of the circular hole, and the assembly accuracy, as in the conventional example that constitutes, the variation in load resistance characteristics as a stopper is reduced. Can do.

  (2) In a preferred embodiment of the load cell according to the present invention, the upper beam portion and the lower beam portion are respectively formed with a strain-generating portion near the fixed portion and a strain-generating portion near the movable portion. A gap is formed closer to the movable part than the strain generating part near the movable part.

  According to this embodiment, since the stopper gap is formed closer to the movable portion than the strain generating portion near the movable portion of the upper and lower beam portions, the load load is applied when a load load is applied to the movable portion. The bending moment acting on the stopper gap can be suppressed by shortening the distance between the action line passing through the force applying point and the stopper gap for regulating the displacement.

  (3) In another embodiment of the load cell of the present invention, the through groove is formed from the starting end on the fixed part side to the open end extending from the end face on the movable part side, and the movable part and the stopper are formed through the through hole. The width of the gap between the opposing surfaces facing each other across the groove is the remaining section other than the section in which the stopper gap is formed in the entire section of the through groove from the start end to the open end. It is greater than the width of the stopper gap.

  According to this embodiment, the through groove has a width of the gap that is equal to or greater than the width of the stopper gap in the remaining section other than the section in which the stopper gap is formed. It is not necessary to use a high-precision processing method as in the case of forming, and it can be formed at low cost, and processing costs can be reduced.

  (4) In another embodiment of the load cell according to the present invention, the movable portion and the stopper are formed in a rectangular shape with opposing surfaces facing each other across the through groove to form the upper side of the rectangular shape. The opposing surface forming the opposing surface and the lower side forms the stopper gap.

  According to this embodiment, the upper and lower sides of the movable portion and the stopper are in contact with each other, and the downward displacement and the upward displacement of the movable portion are restricted.

  (5) In still another embodiment of the load cell of the present invention, the thickness of the strain generating body is between the upper beam portion and the lower beam portion and between the fixed portion and the movable portion. A through hole penetrating in the direction is formed.

  According to this embodiment, the strain sensor is attached to the inner peripheral surface of the through hole, and the strain sensor is sealed by welding a metal cover or the like so as to cover the inner peripheral surface, thereby protecting from the external environment. Is possible.

  As described above, according to the load cell of the present invention, the stopper for preventing overload is formed on the strain body constituting the parallelogram type load cell, and a through groove is formed integrally with the strain body, and Since it is formed outside the load cell, the internal space surrounded by the fixed portion, the movable portion, the upper beam portion, and the lower beam portion can be used effectively other than the stopper.

  In addition, a stopper is constructed by assembling a cylindrical stopper member, etc., into the circular hole of the parallelogram load cell, and causes many variations such as the processing accuracy of the outer shape of the stopper member, the processing accuracy of the inner surface of the circular hole, and the assembly accuracy. Compared to the conventional example, the variation in the load bearing characteristics of the stopper can be reduced.

FIG. 1 is a view showing an attached state of a load cell according to an embodiment of the present invention. FIG. 2 is a front view of the load cell of FIG. FIG. 3 is a plan view of the load cell of FIG. 4 is an enlarged sectional view taken along the line AA in FIG. FIG. 5 is a front view corresponding to FIG. 2 of another embodiment of the present invention. FIG. 6 is a front view of a load cell according to still another embodiment of the present invention. 7 is a cross-sectional view taken along the line BB in FIG.

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

  FIG. 1 is a view showing an attachment state of a load cell according to an embodiment of the present invention, FIG. 2 is a front view of the load cell of FIG. 1, and FIG. 3 is a plan view thereof.

  The load cell 1 according to this embodiment includes a strain generating body 30 made of a rectangular parallelepiped metal elastic body such as aluminum, iron, or a stainless alloy. The load cell 1 is formed between a fixed portion 2 on one end side in the left-right direction (the left-right direction in FIGS. A large-diameter circular through hole 4 penetrating in the front-rear direction (the direction perpendicular to the paper surface of FIGS. 1 and 2 and the vertical direction of FIG. A substantially circular shallow circular concave portion 5 and a pair of substantially circular upper through-cuts that penetrate in the front-rear direction close to the top and bottom of the circular through-hole 4 and are cut out so that a part of the outer periphery thereof continues to the outside. Cutouts 6 and 7 and lower through cutouts 8 and 9, a wiring connection chamber 10 formed on the fixed portion 2 side for connecting and storing wiring as described later, a lid 22 for sealing the opening, and a circular shape Under the through-hole 4 and the movable part 3, it is separated by a thin through-groove 11 that penetrates in the front-rear direction and is And a stopper 12 or the like to prevent breakage of Doseru 1.

  The load cell 1 of this embodiment is waterproof, and in order to seal the strain gauges 13a to 13d as strain sensors attached to four locations on the inner peripheral surface of the circular through hole 4, FIG. As shown, a cylindrical cylindrical seal member 14 made of metal is fitted into the inner peripheral surface of the circular through-hole 4 and sealed by welding.

  As shown in FIG. 2, screw holes 16 a and 16 b for fixing the load cell 1 to a base such as a base 15 of the weighing device are formed on the lower surface side of the fixed portion 2. On the left end surface, screw holes 18a and 18b are formed for mounting a weighing platform bracket 17a that supports the weighing platform 17 on which an object to be weighed is placed. In this example, the weighing platform 17 is supported by the left end surface of the movable portion 3, but may be supported by the upper end surface of the movable portion 3.

  The pair of upper through cutouts 6 and 7 are formed in a substantially circular shape so as to cut out a part of the upper end face between the circular through hole 4 and the upper end face of the strain generating body 30, and a pair of lower through cutouts are formed. The notches 8 and 9 are formed in a substantially circular shape between the circular through hole 4 and the through groove 11 so as to be partially connected to the through groove 11. The inner diameters of the substantially circular through notches 6 to 9 are equal to each other and smaller than the circular through hole 4. Each penetration notch 6-9 is penetrated and formed in parallel with circular penetration hole 4, respectively.

  The movable part 3 and the fixed part 2 include an upper beam part 19 between a pair of upper through notches 6 and 7 above the circular through hole 4 and a pair of lower through notches below the circular through hole 4. 8 and 9 are connected via a lower beam portion 20.

  The upper through-cut notches 6 and 7 form thin-walled strain generating portions 21 a and 21 b in the upper beam portion 19, while the lower through-cut notches 8 and 9 form thin-walled strain generating portions in the lower beam portion 20. Portions 21c and 21d are formed. The distances d1 from the circular through hole 4 to the upper and lower through cutouts 6, 7; 8, 9 are all equal, and the thicknesses of the strain generating portions 21 a to 21 d are the same. As described above, the strain gauges 13a to 13d are attached to the inner peripheral surface of the circular through hole 4 corresponding to the strain generating portions 21a to 21d that generate strain according to the load. The inner diameter of the circular through hole 4 is a size necessary for attaching the strain gauges 13a to 13d and performing wiring work.

  When a load is applied from the weighing platform 17 to the movable portion 3, the four thin portions formed between the four through cutouts 6-9 and the circular through hole 4 are the strain generating portions 21a-21d. , Function as a parallelogram type load cell in which the upper beam portion 19 is the connection between the upper upper notches 6 and 7 and the lower beam portion 20 is the connection between the lower lower notches 8 and 9 To do.

  That is, when a load is applied to the load cell 1 via the weighing platform 17, the strain generating portions 21 a to 21 d on the outer periphery of the circular through hole 4 bend and the strain gauge on the inner peripheral surface of the circular through hole 4 is bent. The stretching strain stress is detected by 13a to 13d, the load load is converted into a load signal, and the load load applied to the weighing platform 17 is calculated by calculating the load signal.

  In this embodiment, the weighing platform 17 is mounted such that the action line LF passing through the applied point of the load is closer to the movable portion 3 than the strain generating portions 21a and 21c.

  The fixed portion 2 is formed with the wiring connection chamber 10 as described above. In this wiring connection chamber 10, the strain gauges 13a to 13d attached to the inner peripheral surface of the circular through hole 4 and the outside are connected. A board or the like for wiring connection can be stored. The circular opening of the wiring connection chamber 10 is sealed with a metal lid 22.

  In addition, a wiring hole 23 that connects the inner peripheral surface of the circular through-hole 4 and the wiring connection chamber 10 is formed inside the fixed portion 2, while an end portion of the fixed portion 2 is connected to the wiring connection chamber 10 and the outside. A connection hole 24 for connecting the two is formed. The strain gauges 13 a to 13 d on the inner peripheral surface of the circular through hole 4 and the outside are connected to each other via the wiring hole 23, the wiring connection chamber 10, and the connection hole 24.

  4 is an enlarged cross-sectional view taken along the line AA in FIG.

  The load cell 1 of this embodiment is waterproof as described above. For this reason, in order to give a complete waterproof seal to the strain gauges 13a to 13d attached to the inner peripheral surface of the circular through-hole 4, both ends are made of a cylindrical metal having a slightly large-diameter flange portion 14a. The cylindrical seal member 14 is fitted into the inner peripheral surface of the circular through hole 4, and the flange portions 14a at both ends of the cylindrical seal member 14 and the inner peripheral surface of the circular through hole 4 are joined by TIG (TIG) welding or laser welding. doing.

  In this welding, the joint portion of the circular through hole 4 and the cylindrical seal member 14 is melted and joined. In order to make the heat transfer characteristics and heat capacity of the joined portion substantially equal, The circular recess 5 is formed over the width W, whereby the welding edge 26 is formed on the periphery of the circular through hole 4 so as to be substantially equal to the flange portion 14 a of the cylindrical seal member 14.

  That is, since the shape of the welding edge 26 at the periphery of the circular through hole 4 and the flange portion 14a of the cylindrical seal member 14 are substantially equal, the heat transfer characteristics and heat capacity of the joined portions can be made substantially equal. The heat at the time of welding is transmitted substantially evenly to the welding edge 26 and the flange portion 14a, and the welding edge 26 and the flange portion 14a can be evenly melted and joined.

  The cylindrical seal member 14 is preferably made of the same kind of metal material as the welding edge 26 at the periphery of the circular through hole 4, that is, the strain body 30.

  An airtight chamber 27 is formed between the inner peripheral surface of the circular through-hole 4 and the cylindrical seal member 14 by welding the welding edge 26 at the periphery of the circular through-hole 4 and the flange portion 14 a of the cylindrical seal member 14. The

  As described above, the strain gauges 13a to 13d attached to the four strain-generating portions 21a to 21d on the inner peripheral surface of the circular through-hole 4 are present in the airtight chamber 27 and thus have waterproof performance. Further, in order to give the load signal detection wiring also waterproof performance, as described above, the wiring hole 23 for wiring of the lead wire drawn out from the airtight chamber 27 to which the strain gauges 13a to 13d are attached is provided, and the fixing portion 2 is connected to wiring introduced from the outside of the load cell 1 through the waterproof connector 25. In order that the wiring connection chamber 10 also has waterproof performance, the circular opening is covered with a thin metal lid 22 with a flange on the outer periphery, and the periphery of the opening and the lid 22 are covered. The flange is joined by TIG (TIG) welding or the like to form a wiring connection chamber 10 that is completely sealed and has high waterproof performance.

  In this embodiment, as shown in FIG. 2, the narrow through-groove 11 penetrating in the front-rear direction is formed from the starting end P1 on the fixed portion 2 side of the load cell 1 toward the end surface on the movable portion 3 side as described above. Yes. The start end P1 is closer to the fixed portion 2 than the strain generating portions 21b and 21d and is closer to the movable portion 3 than the base 15 to which the load cell 1 is fixed.

  The through groove 11 extends in the horizontal direction from the starting end P1 to the movable portion 3 side, continues to the lower part of the lower through notches 8 and 9, extends obliquely downward, and further extends in the vertical and horizontal directions repeatedly to form a rectangular shape. The rectangular portion 12a is formed to reach the open end P3 of the end surface of the movable portion 3, and the stopper 12 is separated from the lower beam portion 20 and the movable portion 3.

  That is, the stopper 12, which is formed by being separated from the lower end surface of the parallelogram load cell by the through groove 11, extends from the fixed portion 2 side toward the movable portion 3 side. It functions as a stopper that limits the displacement downward or upward due to an excessive load from the weighing platform 17. The stopper 12 is configured so that the amount of bending of the stopper 12 is extremely small even when a predetermined excessive load is applied to the movable portion 3 of the load cell 1, that is, the amount of bending of the strain generating portions 21a to 21d when the rated capacity is loaded. Compared to the strain generating portions 21a to 21d, the configuration has a sufficiently large rigidity so that the amount of deflection is sufficiently small.

  In the entire section from the start end P1 of the through groove 11 to the open end P3 of the end face on the movable part 3 side, it corresponds to the section Z1 corresponding to the upper side of the rectangular part 12a shown in FIG. 2 and the lower side of the rectangular part 12a. The sections Z2 and Z3 are formed by wire electric discharge machining using a wire with a predetermined wire diameter in order to define the groove width, and as a gap G for a stopper which is a predetermined gap, for example, a narrow penetration having a gap of about 150 μm A groove 11 is formed. The stopper gap G is set to a size corresponding to a predetermined displacement amount that exceeds the displacement amount of the movable portion 3 when a maximum load that can be measured, that is, a load that is 1.5 times the rated load is applied, for example. ing. Since the wire electric discharge machining is a precision machining that can easily form a gap having a very small interval, the stopper gap G between the movable portion 3 and the rectangular portion 12a can be formed with high accuracy.

  In the section Z1, the upper surface of the rectangular portion 12a of the stopper 12 and the lower surface of the movable portion 3 face each other in the vertical direction (vertical direction), and a stopper gap G is formed between both opposed surfaces. Regulates downward displacement. In the sections Z2 and Z3, the lower surface of the rectangular portion 12a of the stopper 12 and the upper surface of the movable portion 3 are opposed to each other in the vertical direction, and a stopper gap G is formed between both opposed surfaces. The upward displacement of the is regulated.

  The remaining sections other than the sections Z1, Z2, and Z3 in the entire section of the through groove 11 may be the same as or wider than the gaps of the sections Z1, Z2, and Z3, that is, the width of the stopper gap G. May not be as high as the stopper gap G in the sections Z1, Z2, and Z3.

  In this embodiment, the remaining sections other than the sections Z1, Z2, and Z3 where the stopper gap G of the through groove 11 is formed are wider than the stopper gap G. The through-groove 11 in the remaining section is formed by milling or the like, and the processing cost is reduced as compared with the case where it is formed by wire electric discharge machining.

  The stopper 12 separated from the starting end P1 of the fixed portion 2 to the open end P3 of the end face of the movable portion 3 by the through groove 11 defines the maximum downward displacement amount and the upward displacement amount of the load cell 1. That is, for example, when an excessive load exceeding 1.5 times the rated load is applied to the weighing platform 17, the downward displacement of the movable portion 3 of the load cell 1 causes a part of the stopper portion 12a of the section Z1. When an excessively large upward load is applied to the weighing platform 17, the upward displacement of the movable part 3 of the load cell 1 comes into contact with a part of the stopper part 12a in the sections Z2 and Z3. Limited by. Thereby, it is possible to prevent the strain generating portions 21a to 21d from being permanently deformed or damaged beyond the elastic region.

  As shown in FIG. 2, when the applied load F0 of the weighing platform 17 acts on the movable part 3 of the load cell 1 on the line of action LF passing through the applied force point, the movable part 3 is displaced downward, but the movable part 3 is strictly Since the bending stress is applied downward without being displaced downward in the vertical direction, it is displaced downward while forming a convex bent shape on the upper side. When the movable portion 3 comes into contact with the upper left corner P2 of the rectangular portion 12a of the stopper 12 at a distance L1 from the action line LF, the load F0 acting on the action line LF and the corner P2 from the action line LF. The moment force F0 × L1 due to the distance L1 up to and the moment force Fi × L2 due to the force Fi acting on the strain-generating portions 21a and 21c at the distance L2 from the corner portion P2 are Fi × L2 around the corner portion P2. Acts to balance F0 × L1.

  Since Fi = (L1 / L2) · F0, the shorter L1 is compared to L2, that is, the corner P2 where the movable part 3 and the stopper 12 abut and the action line LF where the load is applied. As the distance L1 is shorter than the distance L2 between the line connecting the corner portion P2 and the strain generating portions 21a and 21c, the force Fi acting on the strain generating portions 21a and 21c becomes smaller, so that the load resistance performance as a stopper increases.

  In the present embodiment, since the stopper gap G in the sections Z1, Z2, and Z3 is formed closer to the movable portion 3 than the strain generating portions 21a and 21c, the load resistance performance as a stopper is high.

  Here, if the contact point P2 between the stopper 12 and the movable portion 3 is closer to the fixed portion 2 than the positions of the strain-generating portions 21a and 21c near the movable portion 3, L1 becomes longer and L2 becomes shorter. Therefore, the force Fi acting on the strain generating portions 21a and 21c is increased, and the load bearing performance as a stopper is reduced.

  In the present embodiment, since the cylindrical seal member 14 exists in the internal space surrounded by the movable portion 3, the fixed portion 2, and the upper and lower beam portions 19 and 20, the internal space as described in Patent Documents 1 and 2 above. Therefore, the stopper 12 is provided on the lower side of the lower beam portion 20 and the movable portion 3 with the through groove 11 therebetween.

  Thus, when the stopper 12 is provided on the upper side of the upper beam portion 19 and the movable portion 3 of the parallelogram load cell or on the lower side of the lower beam portion 20 and the movable portion 3, the cylindrical seal member 14 and the like are waterproofed in the internal space. For example, a connecting part other than the upper and lower beam parts having a strain generating part is provided in the internal space, or a circuit unit for digitizing an analog load signal is provided as a digital load cell. Even in such a case, it is possible to provide a stopper for preventing overload.

  The width of the gap is determined by the above-mentioned Patent Document 1 according to the processing accuracy of the outer shape of both ends of the cylindrical stopper member, the processing accuracy of the inner surface of the circular hole for mounting the stopper member in the fixed portion, The load cell 1 of the present embodiment has various variations in the formation of the width of the gap having a function as a stopper, such as the processing accuracy and assembly accuracy of the inner surface of the circular hole for contact insertion. And the movable part 3 only depend on the accuracy of the width of the gap when a gap is formed by wire electric discharge machining, and a gap with little variation can be easily formed.

  Therefore, a stopper having a precise load bearing capacity and less variation in load bearing characteristics is configured.

  In addition, since the stopper 12 of this embodiment is configured to have the same width as the depth dimension of the parallelogram load cell, it is a stopper having higher rigidity than the round bar type provided in the internal space. Thus, it has a greater load bearing performance.

  As described above, the force Fi acting on the strain generating portions 21a and 21c becomes smaller as L1 is shorter, that is, the corner portion P2 where the movable portion 3 and the stopper 12 abut is closer to the action line LF on which the load is applied. Since the load resistance performance as a stopper becomes small and becomes high, as another embodiment, as shown in FIG. 5, it is preferable to further bring the corner portion P2 closer to the action line LF.

That is, in the embodiment of FIG. 5, the upper part of the end face of the movable part 3 is cut out, the measuring base metal fitting 17a of the measuring base 17 is attached, and the corner part P2 of the rectangular part 12a of the stopper 12 acts on the load load F0. The position is equal to the action line LF.
Other configurations are the same as those in the above embodiment.

  FIG. 6 is a front view of a load cell according to another embodiment of the present invention, and parts corresponding to those in FIG.

  In this embodiment, circular upper through holes 36 and 37 and lower through holes 38 and 39 are formed in place of the through notches 6 and 7 and the lower through notches 8 and 9, respectively, and the upper through holes 36 and 37 are formed. The lower through holes 38 and 39 are connected to each other by an upper connecting groove 40 and a lower connecting groove 41 penetrating in the front-rear direction.

  Therefore, if the beam portion existing between the circular through hole 4 and the upper through holes 36 and 37 and the upper connecting groove 40 is the first upper beam portion 42a, the upper through holes 36 and 37 and the upper connecting groove 40 are further provided. The second upper beam portion 42b is provided on the upper side.

  Similarly, when the beam portion existing between the circular through hole 4 and the lower through holes 38 and 39 and the lower connecting groove 41 is a first lower beam portion 43a, the lower through holes 38 and 39 and the lower connecting groove are further provided. A second lower beam portion 43 b is provided below 41.

  That is, a parallelogram type load cell in which the fixed portion 2 and the movable portion 3 are connected to each other by two upper and lower first and second upper beam portions 42a and 42b and first and second lower beam portions 43a and 43b. It has become.

  The outer periphery of the circular through hole 4 is deeply digged up and down except for the first and second continuous portions 44 and 45 extending in the left-right direction, as shown in FIG. 7 which is a cross-sectional view taken along the line BB in FIG. The first upper recess 46a and the first lower recess 47a are formed, the second upper recess 46b is formed above the upper connection groove 40, and the second lower recess 47b is formed below the lower connection groove 41. It is formed.

  Strain gauges 13 a to 13 d are stuck in the circular through hole 4 and sealed by the cylindrical seal member 14 as in the above embodiment.

  As in the above embodiment, the stopper 12 is formed below the second lower beam portion 43b and the movable portion 3 so as to be separated by the through groove 11 and to have a sufficiently large rigidity compared to each strain generating portion. .

  Other configurations are the same as those in the above embodiment.

DESCRIPTION OF SYMBOLS 1,1a Load cell 2 Fixed part 3 Movable part 4 Circular through-hole 5 Circular recessed part 6,7 Upper through notch 8,9 Lower through notch 10 Wiring connection room 11 Through groove 12 Stopper 13a-13d Strain gauge 14 Cylindrical seal member 19 Upper beam portion 20 Lower beam portion 21a to 21d Straining portion 22 Lid 30, 30a Straining body

Claims (5)

The fixed part, the movable part that can be displaced, the upper beam part that connects the fixed part and the upper part of the movable part, and the lower beam part that connects the fixed part and the lower part of the movable part are integrated. A strain body made of a metal material is provided.
A stopper that regulates displacement of the movable part by extending from the fixed part side to the lower side of the lower beam part and the movable part or to the upper side of the upper beam part and the movable part;
The stopper is formed by separating the strain body from the lower beam portion or the upper beam portion by a through groove penetrating the strain body in the thickness direction, and separated from the movable portion,
The movable portion and the stopper have opposing surfaces that face each other in the vertical direction across the through groove, and the downward displacement and the upward displacement of the movable portion are respectively regulated between the opposing surfaces. A stopper gap is formed,
A load cell characterized by that. The upper beam part and the lower beam part are respectively formed with a strain generating part near the fixed part and a strain generating part near the movable part,
The stopper gap is formed closer to the movable part than the strain generating part near the movable part.
The load cell according to claim 1. The through groove is formed from the starting end on the fixed part side to the open end that reaches the end surface on the movable part side,
In the movable part and the stopper, the gap between the opposing surfaces facing each other across the through groove is formed with the stopper gap in the entire section of the through groove from the start end to the open end. In the remaining sections other than the section, the width of the stopper gap is equal to or greater than
The load cell according to claim 1 or 2. In the movable portion and the stopper, opposing surfaces that face each other across the through groove are formed in a rectangular shape, and an opposing surface that forms an upper side of the rectangular shape and an opposing surface that forms a lower side are used for the stopper Forming a gap,
The load cell according to any one of claims 1 to 3. A through-hole penetrating in the thickness direction of the strain-generating body is formed between the upper beam portion and the lower beam portion and between the fixed portion and the movable portion.
The load cell according to any one of claims 1 to 4.

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