JP2015064296A - Load cell - Google Patents

Abstract

PROBLEM TO BE SOLVED: To certainly seal a strain gauge part.SOLUTION: A lid body 3 for covering a storage chamber 14 for storing strain gauges 17a and 17b includes a thick part, and a thin part serving as lid-body-side strain sections 3a and 3b. The lid body 3 can be manufactured from a thick member by machine work. Therefore, in manufacturing the lid body, strain of the shape does not occur differently from a conventional lid body formed of a thin plate, and an extremely accurate lid body 3 can be obtained. Thus, the lid body 3 and strain body 2 certainly adhere to each other without a clearance, and can be stably and certainly bonded to each other. The storage chamber 14 for storing strain gauges 17a and 17b can be certainly sealed.

Description

  The present invention relates to a load cell used in various weighing devices such as a platform scale, a weighing tank, and a weighing hopper.

  In a load cell, for example, a parallelogram type load cell using a Roverval mechanism, a thin strain generating portion is formed in two parallel upper and lower beam portions connecting a fixed portion and a movable portion, and A strain gauge is attached to the surface, and the expansion / contraction strain amount of the strain-causing portion due to the load load is converted into an electrical signal due to a change in the resistance value of the strain gauge to generate a load signal proportional to the magnitude of the load load.

  The strain gauge attached to the strain generating portion is configured by forming a metal wiring pattern such as a Cu-Ni alloy in a predetermined shape on a resin film such as polyimide or epoxy. This metal wiring pattern is susceptible to corrosion when exposed to moisture generated by condensation of water vapor, especially water vapor containing chlorine and sulfur components, and when the resin film absorbs moisture, the thickness changes and the strain gauge load The zero point and span of the signal output will change, making accurate measurement difficult.

  Therefore, in order to prevent corrosion or the like of the strain gauge portion, for example, in Patent Document 1, as shown in FIG. A technique is disclosed in which the storage chambers 32 of the strain gauges 31 are respectively formed at a lower height, and a metal cover 33 serving as a lid is placed thereon to seal the storage chamber 32.

Japanese Utility Model Publication No. 61-30838

  In Patent Document 1, the metal cover 33 that is a lid that seals the storage chamber 32 in which the strain gauge 31 is stored uses an extremely thin plate in order to reduce the rigidity against the load load in the strain stress detection unit. However, the shape of the metal cover 33 made of such a thin plate is easily distorted at the time of manufacture, and the cover 33 and the side wall 32a of the storage chamber 32 are not in close contact with each other, so that a gap is easily generated. For this reason, the cover 33 and the side wall 32a of the storage chamber 32 cannot be reliably joined, and the sealing may be incomplete.

  The present invention has been made paying attention to the above-described actual situation, and an object of the present invention is to more reliably seal the strain gauge portion.

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

(1) The present invention includes a fixed part, a movable part, an upper beam part that connects the fixed part and the upper part of the movable part, and a lower beam part that connects the fixed part and the lower part of the movable part. And a lid joined to the upper surface and the lower surface of the strain-generating body, respectively, and a thin-wall strain-generating portion is provided in each of the upper beam portion and the lower beam portion. Each load cell formed,
The lid has a thick part and a thin part along the extending direction of each beam part extending between the fixed part and the movable part, and the thin part is a lid. A storage chamber is formed between the strain body and the lid body, including a body side strain section, and the strain body and the lid body are joined to each other.

  According to the present invention, the lid has a thick portion and a thin portion including the lid side strain generating portion along the extending direction of each beam portion, and the lid side strain generating portion and each beam. Since the combined strain generating portion of the load cell is the combined strain generating portion of the load cell, the combined strain generating portion may be set so as to satisfy the specifications such as the rated capacity of the load cell. It is not necessary to form a thin plate that is easily distorted at the time of manufacturing, and a thin-walled body side strained portion is formed on a thick member such as a thick plate by machining such as cutting. Can be obtained.

  Thus, since the lid can be manufactured from a thick member by machining, unlike the conventional lid made of a thin plate, distortion of the shape does not occur at the time of manufacture, and an extremely accurate lid can be obtained. As a result, the lid body and the strain body are securely in close contact with each other, no gap is formed, and the lid body and the strain body can be joined stably and reliably, and the storage chamber in which the strain gauge is stored can be more reliably secured. Can be sealed.

  (2) In a preferred embodiment of the present invention, the lid side strain generating portion is formed at a position facing each of the strain generating portions formed in each of the beam portions.

  According to this embodiment, since the lid side strain generating portion where the stress is concentrated is formed at a position facing the strain generating portion of each beam portion, good strain characteristics can be obtained.

  (3) In another embodiment of the present invention, the strain gauge is attached to the inner surface of the lid corresponding to the lid-side strained portion.

  As described above, the combined strain generating portion obtained by combining the strain generating portion of each beam portion of the strain generating body and the lid side strain generating portion may be set so as to satisfy the specifications such as the rated capacity of the load cell, Compared to the strain-generating portion of each beam portion, the lid-side strain-generating portion can be made thinner. In addition, since the lid-side strain generating portion is located on the outer surface side compared to the strain-generating portion of each beam portion, the lid-side strain generating portion is located away from the point where the expansion and contraction stress in the composite strain generating portion is balanced. A large stress is generated as compared with the strain generating portion of each beam portion, and the strain becomes easy to be distorted.

  According to this embodiment, since the strain gauge is attached to the inner surface of the lid corresponding to the easily deformable lid-side strain generating portion, a large load signal can be obtained from the strain gauge.

  (4) According to another embodiment of the present invention, the lid is made of the same type of metal material as the strain body.

  According to this embodiment, since the lid body and the strain body are made of the same type of metal material, the load cell is caused by the difference in mechanical properties of different materials, as in the case of being made of different materials. Can be prevented from deteriorating.

  (5) In still another embodiment of the present invention, the strain body has a thin peripheral edge surrounding the storage chamber, and the lid body has a thin outer peripheral edge. The peripheral edge and the outer peripheral edge of the lid are joined by welding.

  According to this embodiment, since the lid is welded and sealed around the storage chamber for storing the strain gauge, compared to the case where the lid is bonded and sealed with an adhesive, the hermeticity is high and long-term. Thus, the outside air can be stably shut off and sealed, thereby preventing the strain gauge from corroding in the storage chamber.

  Further, the lid body and the strain body are made of the same type of metal material, and the peripheral edge of the strain body and the outer peripheral edge of the lid body are melted and welded to each other, and the lid body made of different materials It is possible to prevent the load cell characteristics from being deteriorated due to a difference in mechanical properties of different materials as compared with a case where the strain generating body is joined via solder.

  In addition, since the peripheral edge of the strain generating body and the outer peripheral edge of the lid, which are joint portions, are formed thin, the heat capacity is small and the difference in heat capacity is also small. Therefore, when welding, it is possible to melt and join each other with a small amount of energy, so that it is possible to reduce the number of melted and joined parts that are different in mechanical properties from other parts.

  Further, since the lid can be manufactured from a thick member by machining as described above, it is extremely accurate without causing distortion of the shape. Therefore, the welded portion is in close contact with the joining partner over the entire periphery, and accurate welding can be performed with a small amount of melting.

  (6) In another embodiment of the present invention, the peripheral edge of the strain generating body is formed in a thin peripheral wall shape surrounding the storage chamber, and the outer peripheral edge of the lid is fitted into the peripheral edge. Is done.

  According to this embodiment, the positioning of the lid relative to the strain generating body is facilitated, and the lid can be accurately loaded on the strain generating body without requiring a special positioning jig or the like.

  In addition, since the fitting portion between the peripheral edge of the peripheral wall shape in the strain body and the outer peripheral edge of the lid body is a welding portion to be welded, the joint portion is in a certain direction (upward, over the entire circumference of the lid body). Or, when welding the joint part continuously over the entire circumference, without changing the direction of the strain body in which the lid body to be welded is fitted, The welding process can be easily performed.

  (7) In still another embodiment of the present invention, the peripheral edge surrounding the storage chamber of the strain generating body and the outer peripheral edge of the lid are each formed in a knife edge shape, and the peripheral edge and the outer edge The peripheral knife edge tips are joined together.

  According to this embodiment, the peripheral edge of the strain generating body and the outer peripheral edge of the lid body are joined together at the knife edge-shaped tips having a small cross-sectional area, and the heat capacity of each member at the joining site is small, and The difference is small. Therefore, when welding, a small amount of each can be melted and joined with less energy, so that the number of melted and joined parts that are different in mechanical properties from other parts can be further reduced. it can.

  (8) In another embodiment of the present invention, the lid body is inclined so that the outer surface thereof becomes thinner toward the outer peripheral side, and the inner surface thereof becomes deeper inward from the outer peripheral side. The outer peripheral edge of the thin wall is formed.

  According to this embodiment, the outer surface of the lid is inclined so that the outer peripheral side is thin, and the inner surface is dug so as to be deeper inward from the outer peripheral side, so that the outer peripheral edge of the thin wall is Because it is formed, the outer peripheral edge can be made thinner by the inclined inner and outer surfaces, and the inner part deeply dug in the inner surface of the lid is used as the space constituting the strain gauge storage chamber can do.

  According to the present invention, the combined strain generating portion obtained by combining the strain generating portion of each beam portion of the strain generating body and the cover side strain generating portion may be set so as to satisfy the specifications such as the rated capacity of the load cell. Unlike the conventional lid, it is not necessary to use a thin plate that is easily distorted at the time of manufacture, and the lid can be manufactured by machining a thick member.

  Thus, since the lid can be manufactured from a thick member by machining, unlike the conventional lid made of a thin plate, distortion of the shape does not occur at the time of manufacture, and an extremely accurate lid can be obtained. As a result, the lid body and the strain body are securely in close contact with each other, no gap is formed, and the lid body and the strain body can be joined stably and reliably, and the storage chamber in which the strain gauge is stored can be more reliably secured. Can be sealed.

1 is a perspective view showing an embodiment of a load cell according to the present invention. It is a disassembled perspective view of the load cell of FIG. It is a top view of the load cell of FIG. It is a front view of the load cell of FIG. It is AA sectional drawing in FIG. It is BB sectional drawing in FIG. It is a perspective view which shows other embodiment of the load cell which concerns on this invention. It is a disassembled perspective view of the load cell of FIG. It is a top view of the load cell of FIG. It is a front view of the load cell of FIG. It is CC sectional drawing in FIG. It is DD sectional drawing in FIG. It is a disassembled perspective view which shows other embodiment of the load cell which concerns on this invention. It is a top view of the load cell of FIG. It is the front view which notched a part of load cell of FIG. It is EE sectional drawing in FIG. It is sectional drawing corresponding to FIG. 5 of the load cell of other embodiment of this invention. It is sectional drawing corresponding to FIG. 6 of the load cell of FIG. It is a front view corresponding to FIG. 10 of the load cell of other embodiment of this invention. It is the front view which notched the part corresponding to FIG. 15 of the load cell of other embodiment of this invention. It is a disassembled perspective view of a prior art example.

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

Embodiment 1
1 is a perspective view of a load cell 1 according to an embodiment of the present invention, FIG. 2 is an exploded perspective view thereof, FIG. 3 is a plan view thereof, FIG. 4 is a front view thereof, and FIG. Sectional drawing and FIG. 6 are BB sectional drawings in FIG.

  The load cell 1 of this embodiment includes a strain body 2 that is a rectangular metal elastic body such as aluminum, iron, and a stainless alloy, and a pair of upper and lower lid bodies 3 made of the same type of metal material as the strain body 2. I have. The lid 3 may be made of a material different from that of the strain body 2.

  The strain generating body 2 includes a fixed portion 4 on one end side in the longitudinal direction (left and right direction in FIGS. 3 and 4) and a movable portion 5 on the other end side, and between the fixed portion 4 and the movable portion 5. The upper and lower beam portions in which a substantially H-shaped through hole 6 in which long left and right oblong holes are connected vertically are formed, and the upper and lower portions of the fixed portion 4 and the movable portion 5 constitute two parallel links. 7 and 8 are connected to the parallelogram type load cells. Hereinafter, for convenience of explanation, the longitudinal direction of the strain body 2 is referred to as the front-rear direction.

  As shown in FIG. 4, a pair of front and rear screw holes 11 for connecting and fixing the load cell 1 to a base 10 such as a base in the weighing device are formed on the lower surface of the fixed portion 4. Are formed with a pair of upper and lower screw holes 13 for attaching a support stay 12 of a load cradle for receiving an object to be weighed.

  Due to the semicircular hole portions formed at the upper and lower ends of the front and rear ends of the through-hole 6, thin strain-generating portions 7a and 7b; 8a and 8b are formed at a predetermined front and rear pitch in the vicinity of the front and rear ends of the upper beam portion 7 and the lower beam 8. Each of the strain generating portions 7a, 7b; 8a, 8b is elastically bent and deformed according to the load acting on the movable portion 5.

  The upper surface of the upper beam portion 7 and the lower surface of the lower beam portion 8 are cut and dug over a range extending from one strain-generating portion 7a, 8a to the other strain-generating portion 7b, 8b. A storage chamber 14 for gauge storage is formed long in the front-rear direction, and the lid 3 is joined to the upper surface of the upper beam portion 7 and the lower surface of the lower beam portion 8 so as to seal the storage chamber 14.

  The lid 3 is made of the same material as that of the strain generating body 2, and is cut from a thick plate-shaped metal material having a thickness that does not cause distortion during manufacture, so that the lid 3 is slightly smaller than the lateral width of the beam portions 7 and 8. It is formed in a strip shape that is long in the front-rear direction, which is the extending direction of the beams 7 and 8 extending across the fixed portion 4 and the movable portion 5 in the strain body 2. Thus, since the lid 3 is manufactured by cutting a thick member, the size and shape can be accurately finished.

  The front and rear two portions of the outer surface of the lid 3 are curved and cut, and the pair of front and rear cover-side strain generating portions 3a and 3b are formed in accordance with the center positions of the strain-generating portions 7a and 7b; 8a and 8b. Is formed. Further, the outer surfaces around the four sides of the lid 3 are cut obliquely toward the outer periphery to form a tapered outer peripheral edge 3e in which the thickness in the vertical direction is gradually reduced.

  In this way, the lid body 3 is an inclined portion whose thickness gradually increases from the movable portion 5 side toward the fixed portion 4 side, for example, along the front-rear direction, which is the extending direction of the beam portions 7 and 8. And a thick-walled portion, a thin lid-side strained portion 3a, a thick-walled portion, a thin-walled lid-side strained portion 3b, a thick-walled portion, and an inclined portion where the thickness gradually decreases.

  As shown in FIG. 5, the thick portion has a sufficient thickness t2 so as to function as a rigid body, compared to the thickness t1 in the vertical direction of the thin lid-side strained portions 3a, 3b. The thickness t2 of the thick portion is such that no distortion occurs during manufacture, and the ratio between the thickness t2 and the thickness t1 of the lid-side strained portions 3a and 3b is, for example, 3: 1 to 10: 1. It is preferable that it is about.

  The thin strain-generating portions 7a, 7b; 8a, 8b of the beam portions 7, 8 and the thin lid-side strain generating portions 3a, 3b; 3a, 3b of the upper and lower lid bodies 3, 3 are circular. Flat surfaces opposite to the curved surface cut in an arc are opposed to each other in the vertical direction. That is, the thin lid-side strain generating portions 3a, 3b; 3a, 3b of the lids 3, 3 are opposed to the thin strain-generating portions 7a, 7b; 8a, 8b of the beam portions 7, 8. Each of the lid-side strain-generating portions 3a, 3b; 3a, 3b is thinner than each of the strain-generating portions 7a, 7b; 8a, 8b.

  It should be noted that the thin lid-side strain generating portions 3a, 3b; 3a, 3b of the lids 3, 3 are opposed to the thin strain-generating portions 7a, 7b; 8a, 8b of the beam portions 7, 8. For example, the lid-side strain generating portions 3a, 3b; 3a, 3b may be positioned closer to each other in the front-rear direction or separated from the strain generating portions 7a, 7b; 8a, 8b. You may form in the made position.

  A pair of front and rear concave grooves 15 extending in the widthwise direction are formed on the upper and lower surfaces of the fixed portion 4 and the movable portion 5 in the strain generating body 2, and the strain generating body 2 is formed between the front and rear concave grooves 15. The upper and lower surfaces of the inner wall are shallowly dug and cut, a thin peripheral edge 16 having a small thickness in the inner and outer directions is formed in a peripheral wall shape, and the storage chamber 14 is placed inside a region surrounded by the peripheral edge 16 on all four sides. It is deeper and cut. The inner dimension of the region surrounded by the peripheral edge 16 is matched with the outer dimension of the lid 3 so that the lid 3 is closely fitted inside the peripheral edge 16.

  As described above, since the lid 3 is fitted in the region surrounded by the peripheral edge 16 of the peripheral wall shape of the strain body 2, the positioning of the lid 3 with respect to the strain body 2 is easy and accurate.

  The height of the peripheral edge 16 of the strain generating body 2 is set to be the same as the tip height of the outer peripheral edge 3e of the lid 3, and the lid 3 is fitted into the peripheral edge 16 as shown in FIGS. In this state, the peripheral edge 16 and the distal end of the outer peripheral edge 3e have the same height, and the joining portion s between the peripheral edge 16 and the outer peripheral edge 3e is melted and joined together by TIG welding.

  The joint portion s is exposed upward over the entire circumference of the lid body 3, and the lid body 3 is fitted when the joint site s is continuously welded over the entire circumference of the lid body 3. The welding process can be performed smoothly and easily without changing the orientation of the strain generating body 2.

  By welding the lid 3 and the strain body 2 in this manner, the storage chamber 14 is completely sealed around the entire circumference, and the lid body 3 is integrated with the strain body 2.

  Here, the cover body 3 integrated with the strain body 2 functions as a parallel beam section that is arranged in parallel with the upper beam section 7 and the lower beam section 8 and elastically deforms together with the strain body 2. The two strain-generating portions 7a, 7b; 8a, 8b and the lid-side strain-generating portions 3a, 3b; 3a, 3b of the facing lid 3 constitute parallel springs, respectively.

  In this case, the spring constants of the strain-generating portions 7a, 7b; 8a, 8b of the strain-generating body 2 and the spring constants of the lid-side strain-generating portions 3a, 3b; 3a, 3b of the lid 3 are added. The composite is the spring constant of each of the four strain-generating portions of the load cell 1 as a whole, and the strain-generating portions 7a and 7b; 8a and 8b of the strain-generating body 2 and the lid so that the rated strain amount can be obtained. The specifications of the elements related to the spring constants such as the thicknesses and widths of the three lid-side strain generating portions 3a and 3b; 3a and 3b are set.

  In this embodiment, the strain gauges 17a and 17b for load measurement are formed on the inner surface of the cover body 3 formed on a flat surface as a whole, corresponding to the center positions of the front and rear cover-side strained portions 3a and 3b. Are attached and fixed in pairs, and the strain gauges 17a and 17b attached to the inner surface of the lid 3 enter the storage chamber 14 that is dug and formed on the strain generating body 2 side.

  A wiring groove 18 is formed by cutting from one end of the storage chamber 14 toward the fixed portion 4, and a circular wiring connection chamber 19 is formed by cutting on the front surface of the fixed portion 4. The wiring connection chamber 19 is connected in communication with a wiring hole 20 formed in the vertical direction so that the conductive wires of the strain gauges 17a and 17b are guided to the wiring connection chamber 19 through the wiring groove 18 and the wiring hole 20. It has become. Further, an external wiring hole 21 communicating with the wiring connection chamber 19 is provided on the outer end surface of the fixed portion 4.

  Although not shown, a terminal plate in which the outer periphery of a ceramic plate embedded with wiring connection pins is surrounded by a metal frame in the external wiring hole 21 is welded to the peripheral wall of the external wiring hole 21. The external wiring hole 21 is shut off from flowing into the wiring connection chamber 19, and the inside and outside of the external wiring hole 21 are hermetically connected via the wiring connection pins. That is, the strain gauges 17 a and 17 b of each storage chamber 14 are connected to the outside via the wiring groove 18, the wiring hole 20, the wiring connection chamber 19, and the external wiring hole 21.

  And after completion | finish of wiring connection work, the metal cover body which is not shown in figure is covered on the opening part of the wiring connection chamber 19, and the peripheral part is welded, Thereby, the storage chamber 14 and the wiring connection chamber 19 are used. It becomes a sealed room that is completely shielded from the outside air.

  The load cell 1 according to the present embodiment is configured as described above, and when a load is applied to the movable portion 5, the strain generating portions 7a and 7b; 8a and 8b of the upper and lower beam portions 7 and 8 as parallel links. And the lid side strain generating portions 3a, 3b; 3a, 3b of the lid body 3 are elastically bent and deformed, so that the strain strain stresses 17a, 17b housed in the upper and lower storage chambers 14 are paired. And the load is converted into a load signal.

  Here, since the lid 3 made of the same type of metal material as the strain body 2 is joined to the peripheral edge 16 surrounding the storage chamber 14 of the strain body 2 by welding, for example, the lid 3 is adhesive. Compared to the conventional structure bonded to the strain generating body 2 by this, the outside air can be shut off stably over a long period of time and hermetically sealed, and the strain gauges 17a, 17b and the wiring are corroded by moisture. This can be surely prevented.

  In order to weld the peripheral edge 16 of the strain body 2 and the outer peripheral edge 3e of the lid 3, the material at both joint sites s is melted, but the melted part is a part that has not been melted, For example, the stress transfer characteristics change, resulting in different mechanical properties. Therefore, when the amount of material melted at the weld site s increases, the “stress-strain” characteristics of the load cell are degraded.

  For this reason, it is preferable that the width of the peripheral edge 16 is as small as possible in order to reduce the melting amount of the material at the joining site s. Thus, while making the width | variety of the peripheral edge 16 of the storage chamber 14 small and thin, and cutting the outer surface of the cover body 3 toward the outer periphery diagonally, and making the outer periphery 3e thin, both heat capacity is made small. At the same time, the difference is reduced. Thereby, when welding, both can be melted and joined to each other with a small amount of energy, and the portions having different mechanical properties from the material around the welded part s can be reduced. Further, when welding, there is no imbalance of heat conduction, and either one of the peripheral edge 16 of the strain generating body 2 or the outer peripheral edge of the lid body 3 is melted quickly, resulting in poor welding, Since the strain body 2 and the lid body 3 are formed with high dimensional accuracy by cutting, they can be reliably welded without causing poor welding.

  In addition, since the strain body 2 and the lid body 3 are made of the same type of metal material, even when the ambient temperature changes when the load cell 1 is used, the difference in expansion and contraction between the strain body 2 and the lid body 3 is different. Does not occur, and the load detection characteristics can be prevented from being adversely affected.

  Further, as described above, the lid 3 integrated with the strain body 2 functions as a parallel beam portion that is arranged in parallel with the upper beam portion 7 and the lower beam portion 8 and elastically deforms together with the strain body 2. A combination of the strain-generating portions 7a, 7b; 8a, 8b of the strain-generating body 2 and the lid-side strain-generating portions 3a, 3b; 3a, 3b of the lid 3 is a combined strain-generating portion as a load cell. .

  At the same time, the lid-side strain-generating portions 3a, 3b; 3a, 3b can be made thinner than the strain-straining portions 7a, 7b; 8a, 8b of the beam portions 7, 8, and the lid-side strain-generating portion 3a. , 3b; 3a, 3b are located on the outer surface side of the respective strain generating portions 7a, 7b; 8a, 8b of the beam portions 7, 8 of the strain generating body 2, so that the stretching stress in the combined strain generating portion is balanced. The lid side strain generating portions 3a, 3b; 3a, 3b are at a position away from the point, and stresses larger than the strain generating portions 7a, 7b; 8a, 8b of the beam portions 7, 8 of the strain generating body 2 are generated. It becomes easy to distort. Moreover, the stress concentration portion is formed at a fixed position. Thus, if the strain gauges 17a and 17b are attached to the lid 3, a large load signal can be obtained from the strain gauges 17a and 17b, which is suitable as a load cell having a relatively small rated capacity.

  In addition, when laser welding is applied instead of the above-described TIG welding, heat can be concentrated and welded in a smaller area, so that the joint portion between the peripheral edge 16 of the storage chamber 14 and the outer peripheral edge 3e of the lid body The heat capacity and heat transfer characteristics of the steel need not be as strict as those of TIG welding.

[Embodiment 2]
7 is a perspective view of a load cell 1 according to another embodiment of the present invention, FIG. 8 is an exploded perspective view thereof, FIG. 9 is a plan view thereof, FIG. 10 is a front view thereof, and FIG. -C sectional view, FIG. 12 is a DD sectional view of FIG. 10, and parts corresponding to the above-mentioned embodiment are denoted by the same reference numerals and detailed description thereof is omitted.

  In the load cell 1 of this embodiment, circular storage chambers 14 are formed on the upper and lower outer surfaces of the strain generating body 2 so as to correspond to the respective strain generating portions 7a, 7b; 8a, 8b. Strain gauges 17a and 17b are respectively attached to the two. In addition, the storage chamber 14 is connected to each other by a wiring groove 18 and communicates with the wiring connection chamber 20 through a wiring hole 20.

  Concave grooves 15 provided on the upper and lower surfaces of the fixed portion 4 and the movable portion 5 in the strain body 2 are formed in partial circular grooves by drilling, and are partially circular concave along the outer corners of the upper and lower beam portions 7 and 8. The groove 22 is formed by cutting, and the peripheral edge 16 surrounding the storage chamber 14 is formed in a sharp knife edge shape outwardly. In addition, an outer peripheral edge 3e is formed around the four edges of the lid 3 made of the same type of metal material as that of the strain generating body 2 with its tip pointed outwardly in a knife edge shape.

  Then, the outer peripheral edge 3e of the lid 3 and the peripheral edge 16 of the strain body 2 are joined together with their tips aligned and melted and joined together by TIG welding at the joint site s.

  According to this configuration, the peripheral edge 16 on the strain body side and the outer peripheral edge 3e of the lid body 3 are joined by the knife-edge-shaped tip portion having a small cross-sectional area, and the heat capacity of each member at the joining portion s is small. And the difference is small. Accordingly, when welding, a small amount of material can be melted and joined with a small amount of energy, and the number of parts having different mechanical properties from the material around the welded portion can be further reduced.

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

[Embodiment 3]
13 is an exploded perspective view of a load cell 1 according to still another embodiment of the present invention, FIG. 14 is a plan view thereof, FIG. 15 is a front view with a part cut away, and FIG. It is E sectional drawing, The part corresponding to said each embodiment attaches | subjects the same referential mark, and abbreviate | omits the detailed description.

  In this embodiment, the storage chamber 14 is recessedly formed on the side of the lid 3 where the knife edge-shaped outer peripheral edge 3e is joined to the knife edge-shaped peripheral edge 16 as in the second embodiment. That is, in this embodiment, the upper surface and the lower surface of the strain generating body 2 are flat surfaces, and the flat surfaces on the strain generating body 2 side correspond to the strain generating portions 7a, 7b; 8a, 8b. The strain gauges 17a and 17b are attached, and the inner surface of the lid 3 is dug and cut to form a storage chamber 14 for storing the strain gauges 17a and 17b.

  And the four periphery of the storage chamber 14 formed in the cover 3 is formed in the inclined surface which extends to the outer periphery 3e of the cover 3, and the outer periphery 3e formed in the four periphery of the cover 3 is the said embodiment. It has a knife edge shape with a smaller tip angle than the two.

  According to this configuration, as shown in FIG. 16, since both ends of the cross section of the lid-side strain generating portions 3a and 3b are inclined, the bending rigidity is reduced, and the stress in the strain generating portions 7a and 7b; 8a and 8b is reduced. Further, the output voltage from the strain gauges 17a and 17b can be increased, and the peripheral edge 16 on the strain generating body 2 side and the outer peripheral edge 3e of the lid body 3 have a knife-edge tip having a small cross-sectional area. The parts are joined to each other, and the difference in the heat capacity of each member at the joined part s is further reduced. Therefore, at the time of welding, a small amount of material can be melted and joined with a small amount of energy, and the number of parts having different mechanical properties from the surrounding material can be further reduced.

[Other Embodiments]
The present invention can also be implemented in the following forms. Each embodiment can also be combined.

  (1) In each of the embodiments described above, the lid 3 has its outer surface inclined to the outer peripheral end and the outer peripheral edge 3e is formed in a thin or knife edge shape. For example, the figure corresponds to FIG. 5 and FIG. As shown in FIGS. 17 and 18, the outer peripheral edge 3e of the lid 3 may be protruded like a bowl to make it thin.

  (2) In the first embodiment described above, the strain gauges 17a and 17b may be attached to the bottom surface of the storage chamber 14 corresponding to the strain generating portions 7a and 7b; 8a and 8b.

  (3) In the second and third embodiments described above, strain gauges 17a and 17b are attached to the inner surface of the lid body 3 as shown in FIGS. 19 and 20 corresponding to FIGS. It can also be implemented in the form of sticking corresponding to the parts 3a, 3b.

  (4) In the third embodiment, when the storage chamber 14 is formed in the lid 2, the storage chamber 14 may be formed for each strain gauge 17 a, 17 b and connected by the wiring groove 18.

  (5) The shape of the storage chamber 14 is not limited to a rectangle or a circle, but may be an oval, an ellipse, or other shapes.

  (6) When aluminum is used for the strain body 2 and the lid 3, the storage chamber 14 and the wiring groove 18 can be formed by precision die casting or pressing, and the outer shape can be cut and finished. It is.

  (7) In each of the above embodiments, the lid 3 has a length that extends between the fixed portion 4 and the movable portion 5 of the strain body 2 and is shorter than the total length of the strain body 2 in the beam longitudinal direction. However, it can also be implemented in a form in which the lid 3 having a length over the entire length of the strain body 2 is joined.

  (8) The storage chamber 14 does not necessarily need to be formed only in either the strain body 2 or the lid body 3, and the strain body 2 and the lid body 3 are each dug shallowly and cut to store at a desired depth. It can also be a chamber 14.

  (9) In each of the above embodiments, the lid 3 and the strain body 2 are joined by welding. However, the invention is not limited to the welding, but may be joined using an adhesive or solder welding. Furthermore, the peripheral edge of the strain body 2 and the outer peripheral edge of the lid body 3 do not have to be formed thin.

DESCRIPTION OF SYMBOLS 1 Load cell 2 Strain body 3 Lid body 3a, 3b Lid body side strain part 3e Outer periphery 4 Fixed part 5 Movable part 7 Upper beam part 7a, 7b Strain part 8 Lower beam part 8a, 8b Strain part 14 Storage chamber 16 Peripheral edge

Claims (8)

A strain generator is provided that includes a fixed portion, a movable portion, an upper beam portion that connects upper portions of the fixed portion and the movable portion, and a lower beam portion that connects lower portions of the fixed portion and the movable portion. And a lid joined to the upper surface and the lower surface of the strain generating body,
A load cell in which a thin strain-generating portion is formed in each of the upper beam portion and the lower beam portion,
The lid has a thick part and a thin part along the extending direction of each beam part extending between the fixed part and the movable part, and the thin part is a lid. Including body side straining part,
A storage chamber for storing a strain gauge is formed between the strain body and the lid,
The strain body and the lid are joined,
A load cell characterized by that. The lid side strain generating portion is formed at a position facing each of the strain generating portions formed in each beam portion,
The load cell according to claim 1. The strain gauge is attached to the inner surface of the lid corresponding to the lid-side strain generating portion,
The load cell according to claim 1 or 2. The lid is made of the same type of metal material as the strain body,
The load cell according to any one of claims 1 to 3. The strain body has a thin peripheral edge surrounding the storage chamber,
The lid body has a thin outer peripheral edge,
The peripheral edge of the strain body and the outer peripheral edge of the lid are joined by welding,
The load cell according to any one of claims 1 to 4. The peripheral edge of the strain body is formed in a thin peripheral wall shape surrounding the storage chamber, and the outer peripheral edge of the lid body is fitted into the peripheral edge.
The load cell according to claim 5. The peripheral edge surrounding the storage chamber of the strain body and the outer peripheral edge of the lid are each formed in a knife edge shape, and the peripheral edge and the knife edge tip of the outer peripheral edge are joined together.
The load cell according to claim 5. The lid body is inclined so that an outer surface thereof becomes thinner toward an outer peripheral side, and an inner surface thereof is dug so as to become deeper inward from the outer peripheral side, so that the outer peripheral edge of the thin wall Is formed,
The load cell according to any one of claims 5 to 7.

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