JP2015021846A - Load cell and method of manufacturing the same - Google Patents

Abstract

PROBLEM TO BE SOLVED: To provide a compact load cell that prevents an excessive load from breaking a strain part and suppresses the influence of a bending moment by a load, and to provide a method of manufacturing the load cell.SOLUTION: A stopper 10 is integrally extended in a cantilever beam shape from a vertically intermediate part of a fixed section 2 toward a movable section 3. The tip 10a of the stopper 10 is stored in a storage recess 11 formed in the movable section 3. A clearance c for the stopper is formed by making the outer surface of the tip 10a of the stopper 10 face the inner surface of the storage recess 11.

Description

  The present invention relates to a load-type load cell used in various weighing devices such as a platform scale, a weighing tank, and a weighing hopper, and more particularly, to a load cell having an overload prevention mechanism for preventing damage due to an excessive load load and a method for manufacturing the same. .

  Patent Document 1 described later discloses an example of a load cell having the overload prevention mechanism. Here, the load cell 24 shown in FIG. 16 shows the sensor mechanism body shown in FIG.

  In the load cell 24, the fixed portion 20 and the movable portion 21 are connected by upper and lower beam portions 27 and 28, and the thin strain-generating portions 25 are formed in the beam portions 27 and 28 at two locations, respectively. Strain gauges 29 are attached to the outer surfaces corresponding to the strain generating portions 25, respectively.

  A take-out portion 20a serving as a stopper integrally extending inward from the fixed portion 20 and a take-out portion 21a integrally extending inward from the movable portion 21 are opposed to each other with a gap Δ in the vertical direction. The take-out part 20 a of the fixed part 20 is connected and supported to the base 22 via the support part 30, while the load receiving part 23 is connected to the take-out part 21 a of the movable part 21.

  In this load cell 24, when an excessive load is applied to the load receiving portion 23 and the movable portion 21 is displaced downward more than the set value, the lower surface of the take-out portion 21a of the movable portion 21 becomes the stopper of the fixed portion 20. It is configured to abut on the upper surface and prevent displacement of the movable portion 21.

  Since the stopper for restricting the displacement of the movable portion 21 is integrally formed as described above, for example, as shown in Patent Document 2, the stopper is a separate member and the stopper is assembled to the load cell main body. Thus, the number of parts can be reduced, and a troublesome assembling process for assembling the stopper of the separate member to the load cell main body while adjusting the gap for the stopper becomes unnecessary, and the cost can be reduced.

JP 2003-247886 A JP 2010-249731 A

  In the load cell 24 of FIG. 16, the load receiving portion 23 is connected to the take-out portion 21 a of the movable portion 21 at the central portion in the longitudinal direction (left-right direction in FIG. 16), while the take-out portion 20 a of the fixed portion 20 is connected to the base 22. It is connected and supported.

  Depending on the structure of the weighing device, instead of receiving a load at the central portion of the load cell 24, for example, as shown in FIG. 17, the load receiving portion 23 is connected to the end face of the movable portion 21 that is one end side of the load cell 24, In some cases, the end surface of the fixing portion 20 on the other end side is connected to and supported by the base 22. As such a weighing device, for example, a combination weigher that supports and measures a plurality of weighing hoppers arranged along the circumference with a plurality of load cells arranged along the circumference inside the hopper. is there.

  As shown in FIG. 17, in the configuration in which one end side of the load cell 24 is connected to the load receiving portion 23, the action line L1 that passes through the point of application of the load F as compared to FIG. When the distance D to the center line L2 of the opposing surfaces 20a and 21a is increased and an excessive load is applied, a large bending moment is applied, the overload cannot be prevented, and the strain generating portion 25 is damaged. There is a fear. Further, a large load may be applied to the load receiving portion 23 upward due to work convenience. In the case of this stopper structure, displacement due to a large upward load applied to the movable portion 21 cannot be regulated at all.

  A load cell 24 shown in FIG. 18 shows the sensor mechanism shown in FIG. As shown in FIG. 18, one end side of the load cell 24 ′ is connected to the load receiving portion 23, and the other end side is connected to and supported by the base 22, and an overload prevention stopper 26 is provided at the lower end portion of the fixed portion 20. Further, there is described a configuration in which a gap Δ is formed between the upper surface of the tip portion 26 a and the lower surface of the movable portion 21 so as to extend integrally toward the movable portion 21 side. In such a configuration, the action line passing through the point of application of the load F and the center line of the stopper 26 that regulates the displacement can be made coincident, and when an excessive load load is applied, a bending moment is applied. Absent.

  However, in addition to the lower beam portion 28 constituting the load cell 24 ′, an overload prevention stopper 26 must be integrally formed below the beam portion 28, extending toward the movable portion 21, and the load cell 24 ′. This will hinder downsizing.

  The present invention has been made by paying attention to the above-described situation, and a compact load cell that prevents damage to a strain-generating portion due to an excessive load and suppresses the influence of a bending moment due to the load, and a method for manufacturing the same. The purpose is to provide.

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

(1) The load cell of the present invention includes a fixed part, a movable part that can be displaced, an upper beam part that connects the fixed part and the upper part of the movable part, and a lower part that connects the fixed part and the lower part of the movable part. A load-type load cell in which a strain detecting portion for load detection is formed on each of the upper beam portion and the lower beam portion,
The fixed portion has a stopper that integrally extends in a cantilever shape from the upper and lower intermediate portions of the fixed portion toward the movable portion,
The movable part has a storage part into which a tip part of the stopper enters,
The outer surface of the tip portion of the stopper and the inner surface of the housing portion are formed with a stopper gap that opposes at least the vertical direction and restricts the displacement of the movable portion.

  According to the present invention, since the stopper gap is formed that is opposed at least in the vertical direction, when an excessive load is applied, the downward and upward displacement of the movable part is restricted, and the strain generating part of the load cell is While being able to prevent breakage, the stopper is integrally extended in a cantilever shape from the upper and lower intermediate part of the fixed part toward the movable part, and its tip part enters the accommodating part of the movable part. The stopper can be arranged by effectively using the internal space surrounded by the fixed part, the movable part, the upper beam part, and the lower beam part, and without compromising the size reduction of the load cell, Become.

  In addition, since the tip of the stopper enters the accommodating portion formed in the movable portion, when the load load is applied to the movable portion, the action line passing through the point of application of the load load and the displacement for the stopper are regulated. The bending moment acting on the stopper gap can be suppressed by shortening the distance to the gap.

  Furthermore, since the stopper is integrally extended from the fixed portion, i.e., the stopper is integrally formed, the stopper is a separate member, and the stopper is adjusted while adjusting the stopper gap as compared with the structure assembled to the load cell body. A troublesome assembly process for assembling the load cell body is not necessary, and the number of parts can be reduced to reduce the cost.

  (2) In a preferred embodiment of the present invention, the accommodating portion of the movable portion is an accommodating recess that is recessed in the extending direction of the stopper that extends from the fixed portion toward the movable portion.

  According to this embodiment, the distal end portion of the stopper extending from the fixed portion toward the movable portion enters and is accommodated in the accommodating recess that is recessed in the extending direction.

  (3) In another embodiment of the present invention, the stopper gap is formed such that the outer surface of the tip portion of the stopper and the inner surface of the housing recess face each other over the entire surface.

  According to this embodiment, the outer surface of the distal end portion of the stopper and the inner surface of the accommodating recess of the movable portion are opposed to each other over the entire surface, so that the stopper gap is formed, so according to the shape of the distal end portion and the accommodating recess. Thus, the displacement of the movable part in a plurality of directions can be restricted. This not only restricts the displacement of the movable part against an excessive load during weighing, but also regulates the displacement of the movable part even when the load cell falls or collides with other objects. The distortion portion can be prevented from being damaged, and the handling becomes easy.

(4) In still another embodiment of the present invention, the housing recess recessed in the extending direction is formed so that the fixed portion side is narrower than the recessed back side,
The stopper gap is formed by the outer surface of the tip portion and the inner surface of the housing recess on the back side and the fixed portion side.

  According to this embodiment, the accommodating recess that is recessed in the extending direction of the stopper, that is, in the direction from the fixed portion toward the movable portion, is formed so that the back side is wide and the fixed portion side is narrow, which is opposite to the stopper extending direction. The displacement of the movable part in the direction can be regulated. For example, even when a load that pushes or pulls the movable part in the horizontal direction is regulated, the displacement of the movable part is regulated to prevent the strain generating part of the load cell from being damaged. can do.

(5) In another embodiment of the present invention, the outer surface of the tip of the stopper and the inner surface of the receiving recess are formed in a concentric partial circle,
The outer surface and the inner surface formed in the partial circle face each other to form the stopper gap.

  According to this embodiment, the contact between the outer surface of the distal end portion of the stopper and the inner surface of the housing recess becomes contact between the arc surfaces, and the displacement of the movable portion in multiple directions can be restricted.

(6) The load cell manufacturing method of the present invention includes a fixed portion, a movable portion that can be displaced, an upper beam portion that connects the fixed portion and the upper portion of the movable portion, and a lower portion of the fixed portion and the movable portion. And a lower beam portion to be connected, and a load-balancing type load cell manufacturing method in which a strain detecting portion for load detection is formed in each of the upper beam portion and the lower beam portion,
The fixed portion has a stopper that integrally extends in a cantilever shape from the upper and lower intermediate portions of the fixed portion toward the movable portion,
The movable part has a storage part into which a tip part of the stopper enters,
Forming a through groove in a material for forming the load cell, and dividing the material into the housing part and the tip part entering the housing part,
The outer surface of the distal end portion of the divided stopper and the inner surface of the accommodating portion form a stopper gap that opposes at least the vertical direction and restricts the displacement of the movable portion.

  According to the present invention, the distal end portion of the stopper and the accommodating portion into which the distal end portion enters are formed by dividing the material by subjecting the material to through groove processing. Depending on the setting of the processing path for through-groove processing, it can be arbitrarily selected, and a stopper gap can be formed according to the width of the through-groove.

  (7) In a preferred embodiment of the present invention, the material includes the fixed portion, the movable portion, the upper beam portion, the lower beam portion, the stopper, and the accommodating portion along a series of machining paths. Formed by one-stroke writing through-groove processing.

  According to this embodiment, each part can be formed by one-stroke writing through-groove processing, so there is no need to load the material into different processing machines many times and process each part, reducing the number of processing steps and reducing costs. Can be achieved.

  (8) In another embodiment of the present invention, through holes corresponding to the strain generating portions of the upper beam portion and the lower beam portion are formed in the material in advance.

  According to this embodiment, since the through holes are formed in advance in the material so as to respectively correspond to the thin strain generating portions, in the one-stroke writing through groove processing, a curved shape for forming the strain generating portions is formed. There is no need to perform processing along the processing path, and the time required for through-groove processing can be shortened.

  (9) In still another embodiment of the present invention, the through groove is formed by at least one of wire cut electric discharge machining, laser machining, and water jet machining.

  According to this embodiment, each part is formed with high accuracy by wire-cut electrical discharge machining, laser machining, and ultra-fine through-groove machining using at least one of water jet machining that injects and cuts a high-pressure water jet. Can do.

  As described above, according to the present invention, when an excessive load is applied, the displacement of the movable portion can be regulated downward to prevent the strained portion of the load cell from being damaged, and the stopper can be fixed. Since it is arranged in the internal space surrounded by the part, the movable part, the upper beam part, and the lower beam part, it becomes a compact configuration without hindering the downsizing of the load cell.

  In addition, since the distal end portion of the stopper enters the housing portion formed in the movable portion, when a load load is applied to the movable portion in the measuring portion having a load receiving portion at the distal end of the movable portion. The bending moment acting on the stopper gap can be suppressed.

  Furthermore, since the stopper is integrally formed, the cost can be reduced as compared with a configuration in which the stopper is a separate member and is assembled to the load cell body.

It is a side view of the load cell concerning one embodiment of the present invention. It is a perspective view of the load cell of FIG. FIG. 2 is a partially enlarged view of a stopper gap c in FIG. 1. It is a perspective view which shows an example of the manufacturing method of the load cell of FIG. It is a perspective view which shows the other example of the manufacturing method of the load cell of FIG. It is a side view of the load cell which concerns on other embodiment of this invention. It is a side view of the load cell which concerns on other embodiment of this invention. It is a side view of the load cell which concerns on other embodiment of this invention. It is a perspective view which shows the manufacturing method of the load cell of FIG. It is a side view of the load cell which concerns on other embodiment of this invention. It is a perspective view which shows the manufacturing method of the load cell of FIG. It is a side view of the load cell which concerns on other another embodiment of this invention. It is the front view which notched a part of FIG. It is a side view of the load cell which concerns on other embodiment of this invention. It is a side view of the load cell which concerns on other embodiment of this invention. It is a side view of the load cell of a prior art example. It is a side view of the load cell of a prior art example. It is a side view of the load cell of another prior art example.

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

(Embodiment 1)
FIG. 1 is a side view of a load cell according to an embodiment of the present invention, and FIG. 2 is a perspective view thereof.

  The load cell 1 is a robust load cell in which a rectangular block-shaped metal material, for example, a metal material such as an aluminum alloy or iron is penetrated in the thickness direction (perpendicular to the plane of FIG. 1). The load cell 1 includes a fixed portion 2 in which a square block is connected to a fixed base 8 of a weighing device with bolts, a movable portion 3 in which a support member 9 such as a weighing pan or a weighing hopper is connected with bolts, and a fixed portion. 2 and the upper and lower portions of the movable portion 3 are processed so as to leave the upper beam portion 4 and the lower beam portion 5 that horizontally connect the central portion and the central beam. The upper beam portion 4 and the lower beam portion 5 are each formed with two thin strain-generating portions 6, and a strain gauge 7 is attached to the outer surface of each strain-generating portion 6.

  In the central beam connecting the movable part 3 from the upper and lower intermediate part of the fixed part 2, preferably the upper and lower central part, the inner surface facing the fixed part 2 of the movable part 3 is subjected to narrow groove processing as described later, An accommodation recess 11 that is recessed in the direction from the fixed portion 2 toward the movable portion 3 (the right direction in FIG. 1) is formed, and the central beam is not in contact with the movable portion and becomes a stopper 10 that extends from the fixed portion 2.

  Accordingly, the stopper 10 extending from the fixed portion 2 has the same thickness as the metal material and is formed in a rectangular parallelepiped shape that is long in the extending direction. The accommodating recess 11 of the movable portion 3 has a rectangular groove shape penetrating in the thickness direction, and the distal end portion 10 a of the stopper 10 enters and is accommodated in the accommodating recess 11. In addition, the accommodating part which accommodates the front-end | tip part 10a of the stopper 10 is not restricted to the groove-shaped accommodation recessed part 11 like this embodiment, The penetration hole which penetrated may be sufficient.

  The distal end portion 10a of the stopper 10 and the receiving recess 11 are formed by subjecting a metal material to thin through-groove processing and dividing the metal material into the distal end portion 10a of the stopper 10 and the receiving recess 11 as will be described later. Is done.

  Therefore, the outer surface of the distal end portion 10a of the stopper 10 and the inner surface of the receiving recess 11 are opposed to each other at a minute interval corresponding to the groove width of the through groove, and a stopper gap c that restricts the displacement of the movable portion 3 is formed. .

  As shown in FIG. 3 in which a part of the stopper gap c in FIG. 1 is enlarged, the upper surface 10au of the tip 10a of the stopper 10 and the downward inner surface 11d of the receiving recess 11 are opposed in the vertical direction (vertical direction). The lower surface 10ad of the distal end portion 10a and the upward inner surface 11u of the housing recess 11 face each other in the vertical direction, and are configured to be able to regulate the downward and upward displacement of the movable portion 3, respectively.

  Further, the distal end surface 10as of the distal end portion 10a and the laterally directed inner surface 11s of the accommodating recess 11 are opposed to each other in the horizontal direction so that the displacement of the movable portion 3 in the horizontal direction toward the fixed portion 2 can be regulated.

  As another embodiment of the present invention, only the downward displacement of the movable part 3 may be restricted.

  As described above, the front end portion 10a of the stopper 10 in the housing recess 11 has the upper and lower surfaces 10au and 10ad and the front end surface 10as, which are the entire outer surfaces thereof, facing the entire surface 11d, 11u, and 11s of the inner surface of the housing recess 11. A clearance c is formed.

  When a downward load F is applied to the movable portion 3 of the load cell 1 configured as described above as indicated by an imaginary line in FIG. 1, the movable portions 3 are parallel to each other while flexibly deforming each strain generating portion 6. Will be displaced downward. Thereby, the bending deformation of each strain generating portion 6 is detected by the strain gauge 7, and the load F applied to the movable portion 3 is calculated by calculating the output from each strain gauge 7 in the measurement circuit.

  In this case, the size of the stopper gap c formed between the distal end portion 10a of the stopper 10 and the accommodating recess 11 is, for example, a maximum load that can be measured, that is, a load that is 1.5 times the rated load. It is set to a size corresponding to a predetermined displacement amount that exceeds the downward displacement amount of the movable part 3 at that time. Therefore, even if an excessive load exceeding 1.5 times the rated load is applied and the movable part 3 tries to move downward beyond the set amount of displacement, the downward inner surface 11d of the receiving recess 11 becomes the tip of the stopper 10. The upper part 10au of 10a is contacted, and further downward displacement of the movable part 3 is prevented, so that the strain generating part 6 can be prevented from being deformed beyond the elastic region to be permanently deformed or damaged.

  Further, as described above, the lower surface 10ad of the distal end portion 10a of the stopper 10 and the upward inner surface 11u of the accommodating recess 11 face each other, and the distal end surface 10as of the distal end portion 10a of the stopper 10 and the laterally inner surface 11s of the accommodating recess 11 are formed. Since they are opposed to each other, the movable part 3 is restricted not only in the downward direction to which the measurement load is applied, but also in the upward direction and in the horizontal direction toward the fixed part 2 side. As a result, when the load cell 1 is transported or managed, the movable part 3 is large when it is accidentally dropped, bumped against another object, or removed from the weighing pan or weighing hopper for cleaning or the like. Even if the external force acts improperly, the strain generating portion 6 can be prevented from being damaged.

  Further, since the distal end portion 10a of the stopper 10 enters the accommodating recess 11 of the movable portion 3 to form the stopper gap c, as shown in FIG. Since the distance D from the center line L2 of the distal end portion 10a of the stopper 10 can be shortened, the bending moment acting on the distal end portion 10a of the stopper 10 due to the load F is suppressed in the measuring portion having a load receiving portion at the movable end. be able to.

  Next, a method for manufacturing the load cell 1 will be described.

  In this embodiment, the load cell 1 is manufactured using wire-cut electric discharge machining in which electric discharge is generated between the electrode wire and the workpiece and machining is performed by the electric discharge.

For example, as shown in FIG. 4, four through-round holes 12 _{1 to} 12 ₄ for forming the strain-generating portion 6 in advance are drilled in a predetermined position in a horizontally placed rectangular parallelepiped metal material W. Set up. After inserting the electrode wire 13 in a predetermined circular through-hole 12 _1, the metallic material W or the electrode wire 13 to move two-dimensionally by a computer controlled, single stroke shape along a relatively electrode wire 13 to a series of processing path R The metal material W is melted by the thin through grooves 14. The through-round holes 12 _{1 to} 12 ₄ correspond to “through holes” in the present invention.

Specifically, the electrode wire 13 is relatively moved from the through-round hole 12 ₁ to the through-round hole 12 ₂ along the lower surface of the upper beam portion 4, and along the inner surface including the accommodating recess 11 of the movable portion 3. It travels to the through-round hole 12 ₃ and travels to the through-round hole 12 ₄ along the upper surface of the lower beam portion. Furthermore, a relatively electrode wire 13, the lower inner surface of the fixed portion 2 through the through round holes 12 _4, the lower surface of the stopper 10, the distal end surface and the upper surface, as well as through at start along the upper inner surface of the fixed part 2 to travel to the round hole 12 _1.

  Thereby, locations other than the strain generating portion 6, that is, inner surfaces of the fixed portion 2, the upper beam portion 4, the lower beam portion 5, and the movable portion 3, and the stopper 10 and the accommodating recess 11 are formed in series.

  Since the wire-cut electric discharge machining is a precision machining that can easily form a gap with a minute interval, the stopper gap c between the tip 10a of the stopper 10 and the accommodating recess 11 of the movable part 3 is highly accurate. Can be formed.

In this way, through-holes 12 _{1 to} 12 ₄ corresponding to the strain-generating portions 6 are formed in advance in the metal material W, and the thin through-grooves 14 are formed in a single stroke along a series of machining paths R by wire-cut electric discharge machining. Since the load cell 1 is manufactured by fusing, the metal material W does not need to be processed with different processing machines many times, and the processing man-hours can be reduced and the cost can be reduced.

In addition, without forming the through-round holes 12 _{1 to} 12 ₄ in advance, for example, as shown in FIG. The inner surfaces of the portion 4, the lower beam portion 5, the movable portion 3, the stopper 10, the accommodating recess 11, and the strain-generating portion 6 may be formed by fusing in series with a thin through groove 14.

  Further, not limited to wire cut electric discharge machining, laser machining or water jet machining may be used, or normal machining may be used. In the water jet processing, a high-pressure water jet is jetted and cut, so there is no distortion due to heat.

(Embodiment 2)
Figure 6 is a side view of the load cell 1 ₁ according to another embodiment of the present invention, the parts corresponding to the embodiment of FIG. 1, the same reference characters.

In this embodiment, the front end portion 10 ₁ a of the stopper 10 ₁ entering the accommodation recess 11 ₁ of the movable portion 3 has the same height in the vertical direction (vertical direction in FIG. 6) as the other portions. ₁ a1 and a partially circular second tip portion 10 ₁ a2 that is larger in the vertical direction than the first tip portion 10 ₁ a1.

The accommodation recess 11 ₁ in which the tip 10 ₁ a of the stopper 10 ₁ is accommodated is a first accommodation recess 11 ₁ a that houses the first tip 10 _{1 a} 1 and a second that houses the second tip 10 ₁ a 2. It has an accommodation recess 11 ₁ b. The second housing recess 11 ₁ b is concentric with the second tip portion 10 _{1 a} 2 formed in a partial circle, and is formed in a partial circle having a large diameter corresponding to the stopper gap c. Therefore, the housing recess 11 ₁ is narrower in the first housing recess 11 ₁ a on the fixed portion 2 side than the second housing recess 11 ₁ b on the back side.

And upper and lower surfaces and the accommodation recess 11 of the _first housing recess 11 ₁ a downward and upward respective inner surface of the distal end portion 10 ₁ a first end 10 ₁ a1 of the stopper for gap c with respective vertically opposed to Form. The tip portion 10 ₁ a second distal portion 10 ₁ a2 arcuate outer peripheral surface and the housing recess 11 ₁ of the second housing recess 11 ₁ b of the arc-shaped inner peripheral surface facing the gap stopper c of Form.

In this embodiment, not only can the excessive displacement in the vertical direction of the movable portion 3 be restricted, but also the excessive displacement in multiple directions can be caused by the arc-shaped outer peripheral surface of the second tip portion 10 ₁ a2 and the second accommodating recess. It can be prevented by contact with the arc-shaped inner peripheral surface of 11 ₁ b, and has higher durability against the fall of the load cell 1, the collision with other objects, or the undue external force applied by the operator. Become.

The shape second housing recess 11 ₁ b of the second tip portion 10 ₁ a2 and housing recess 11 ₁ of the stopper 10 _1, which is not limited to a partial circular, can prevent excessive displacement of the multi-directional, e.g., partially elliptical It may be a shape or a polygon. The first housing recess 11 ₁ a of the first tip portion 10 ₁ a1 and housing recess 11 ₁ of the stopper 10 ₁ may be omitted.

Similar to the load cell 1 ₁ is also the embodiment of this embodiment can be manufactured using a wire-cut electric discharge machining or the like.

(Embodiment 3)
Figure 7 is a side view of the load cell 1 ₂ according to another embodiment of the present invention, the parts corresponding to the embodiment of FIG. 1, the same reference characters.

  In a load cell with a large rated load, it is necessary to increase the strength of the stopper.

In the load cell 1 ₂ of this embodiment, a stopper 10 ₂ extending toward the fixed part 2 to the movable portion 3, in the vertical direction including the tip portion 10 ₂ a that is housed in the housing recess 11 and _second movable part 3 the height is increased, thereby increasing the strength of the stopper 10 _2. The accommodating recess 11 ₂ of the movable portion 3 is also made to have a height in the vertical direction so that the tip end portion 10 ₂ a of the stopper 10 ₂ can be accommodated.

The load cell 1 ₂ can also be prepared similarly by using a wire cut electric discharge machining or the like.

Further, the back side of the load cell 1 ₂ of the accommodation recess 11 ₂ of FIG. 7, as shown in FIG. 8, may be continuously provided a length hole portion 11 ₂ c in the vertical direction.

For example, as shown in FIG. 9, the load cell 1 ₂ ′ in FIG. 8 includes four through-round holes 12 _{1 to} 12 ₄ for forming the strain-generating portion 6 in advance in the metal material W, and the long hole portion. A through long hole 16 corresponding to 11c is drilled at a predetermined position by drilling or the like. After the electrode wire 13 is inserted into the predetermined through-round hole 12 ₁ , the electrode wire 13 is relatively moved from the through-round hole 12 ₁ to the through-round hole 12 ₂ along the lower surface of the upper beam portion 4. The penetrating round hole 12 _{2 is} caused to travel to the penetrating elongated hole 16 along the upper inner surface of the movable portion 3 and the downward inner surface of the accommodating recess 11 ₂ .

Further, the electrode wire 13 is caused to run from the through long hole 16 to the through round hole 12 ₃ along the upward inner surface of the receiving recess 11 ₂ and the lower inner surface of the movable portion 3, and is lowered from the through round hole 12 _3. Along the upper surface of the beam portion 5, the through-hole 12 _{4 is} run. Next, the electrode wire 13 is caused to run from the through-round hole 12 ₄ to the through-round hole 12 ₃ along the lower surface of the stopper 10 ₂ , and further from the through-round hole 12 ₂ to the upper surface of the stopper 10 _2. Travel to the through-hole 12 ₁ at the time.

In this case, since the through long hole 16 is formed in advance, it is not necessary to form the through groove 14 by the electrode wire 13 for forming the front end surface 10 ₂ as of the front end portion 10 ₂ a of the stopper 10 ₂ shown in FIG. Thus, the machining time of wire cut electric discharge machining can be shortened.

Also, the load cell 1 ₂ stopper 10 ₂ in FIG. 7, both to further increase the vertical height except for its tip 10 ₂ a, cut portions corresponding to the strain generating portion 6 at four positions in an arc The configuration shown in FIG. 10 may be omitted. In the load cell 1 ₃ in FIG. 10, with the stopper 10 ₃ and the upper beam portion 4 is divided by a thin through groove, and the stopper 10 ₃ and the lower beam portion 5 are separated by a thin through groove.

In the load cell 1 _3, as shown in FIG. 11, the electrode wire 13 in a predetermined circular through-hole 12 ₁ of the pre-strain-generating-portions of the four formed so as to correspond to 6 circular through-holes 12 ₁ to 12 ₄ After that, the electrode wire 13 is relatively moved from the through-round hole 12 ₁ to the through-round hole 12 ₂ along the lower surface of the upper beam portion 4, and on the inner surface including the accommodating recess 11 ₂ of the movable portion 3. It is only necessary to travel to the through-round hole 12 ₃ along the upper surface of the lower beam portion and to the through-round hole 12 ₄ along the upper surface of the lower beam portion. As shown in FIG. 4 and FIG. It is not necessary to run from the through-round hole 12 ₄ to the through-round hole 12 ₁ at the start. As a result, a series of machining paths R ′ that cause the electrode wire 13 to travel relatively in a single stroke can be shortened, and the machining time can be shortened.

(Other embodiments)
The present invention can also be implemented in the following forms.

  (1) As shown in FIGS. 12 and 13, for example, in the load cell 1 of the embodiment of FIG. 1, the support member 9 that supports the weighing pan and the weighing hopper is bifurcated and is disposed across the movable part 3. The bolts may be connected from the side.

  As a result, the line of action passing through the point of application of the load F can be positioned at the tip 10a of the stopper 10, and an excessive load can be efficiently and accurately abutted and supported by the stopper tip 10a.

(2) The shape of the distal end portion 10a of the stopper 10 and the housing recess 11 is not particularly limited as long as it has surfaces that face in the vertical direction, and is not limited to a rectangle or a circle in side view. as shown in FIG. 14, the distal end portion ₁₀₄ a of the stopper 10 ₄ may be a triangular shape. Further, as shown in FIG. 15, the tip portion 10 ₅ a of the stopper 10 ₅ may be a large rectangular shape having a large vertical height.

1, 1 ₁ to ₁₅ Load cell 2 Fixed portion 3 Movable portion 4 Upper beam portion 5 Lower beam portion 6 Strain portion 7 Strain gauge 8 Fixed base 9 Support member 10, 10 ₁ to 10 ₅ Stopper 10a, 10 ₁ a, 10 ₄ a, 10 ₅ a Tip 11, 11 ₁ , 11 ₄ , 11 ₅ receiving recess

Claims (9)

A fixed portion; a movable portion that can be displaced; an upper beam portion that connects the fixed portion and the upper portion of the movable portion; and a lower beam portion that connects the lower portion of the fixed portion and the movable portion; A load-type load cell in which a strain detecting portion for load detection is formed in each of the beam portion and the lower beam portion,
The fixed portion has a stopper that integrally extends in a cantilever shape from the upper and lower intermediate portions of the fixed portion toward the movable portion,
The movable part has a storage part into which a tip part of the stopper enters,
The outer surface of the tip of the stopper and the inner surface of the housing portion form a stopper gap that opposes at least the vertical direction and restricts the displacement of the movable portion.
A load cell characterized by that. The accommodating portion of the movable portion is an accommodating recess that is recessed in the extending direction of the stopper that extends from the fixed portion toward the movable portion.
The load cell according to claim 1. The outer surface of the tip of the stopper and the inner surface of the receiving recess are opposed over the entire surface to form the stopper gap.
The load cell according to claim 2. The housing recess recessed in the extending direction is formed so that the fixed portion side is narrower than the recessed back side,
The outer surface of the tip portion and the inner surface on the back side and the fixed portion side of the housing recess face each other to form the stopper gap.
The load cell according to claim 2. The outer surface of the tip of the stopper and the inner surface of the receiving recess are formed in a concentric partial circle,
The outer surface and the inner surface formed in the partial circle face each other to form the stopper gap;
The load cell according to claim 2. A fixed portion; a movable portion that can be displaced; an upper beam portion that connects the fixed portion and the upper portion of the movable portion; and a lower beam portion that connects the lower portion of the fixed portion and the movable portion; A method for manufacturing a load-type load cell in which a strain detecting portion for load detection is formed in each of a beam portion and the lower beam portion,
The fixed portion has a stopper that integrally extends in a cantilever shape from the upper and lower intermediate portions of the fixed portion toward the movable portion,
The movable part has a storage part into which a tip part of the stopper enters,
Forming a through groove in a material for forming the load cell, and dividing the material into the housing part and the tip part entering the housing part,
The outer surface of the distal end portion of the divided stopper and the inner surface of the housing portion form a stopper gap that opposes at least the vertical direction and regulates the displacement of the movable portion.
A method for manufacturing a load cell. Forming the fixed portion, the movable portion, the upper beam portion, the lower beam portion, the stopper, and the accommodating portion in the material by one-stroke writing through groove processing along a series of processing paths,
The manufacturing method of the load cell of Claim 6. In the material, through holes corresponding to the strain generating portions of the upper beam portion and the lower beam portion are formed in advance,
The method for manufacturing a load cell according to claim 7. The through groove is formed by at least one of wire cut electric discharge machining, laser machining, and water jet machining,
A method for manufacturing a load cell according to any one of claims 6 to 8.

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