JP5540390B2 - Load cell strain body, load cell and weight measuring device using the load cell strain body, and method for producing the load cell strain body - Google Patents

Description

  The present invention relates to a load cell strain body used in a weight measurement device, a load cell using the load cell strain body, a weight measurement device, and a method of manufacturing the load cell strain body.

  Conventionally, a load cell for a weight measuring apparatus for measuring the weight of an object to be measured has a structure as shown in FIG. Here, FIG. 10 is a side view showing a configuration of a weight measuring apparatus using a conventional load cell.

  This load cell 100 is formed in a substantially rectangular parallelepiped shape, and a strain-generating body 110 in which one end portion 115 in the longitudinal direction is fixed to a fixing base 150, and the other end portion 116 in the longitudinal direction of the strain-generating body 110 are cantilevered. The movable base 120 is supported, and the strain sensor 130 disposed in the strain-generating portion of the strain-generating body 110 is provided. The strain body 110 and the fixing base 150 are fixed by a screw 140 in a connecting hole 141 communicating with each other. The strain body 110 and the movable base 120 are fixed by a screw 145 in a connecting hole 146 communicating with each other.

  A protrusion 125 is formed on the movable base 120 so as to protrude in a direction away from the strain generating body 110 at a position corresponding to the strain sensor 130 in plan view. The load cell 100 is used as a weight measuring device so that a load due to the weight of the measurement target is applied on the protrusion 125. When a load due to the weight of the measurement target is applied, the strain generating body 110 is deformed according to the load, so that the amount of expansion / contraction can be detected by the strain sensor 130 and the weight of the measurement target can be calculated from the detection result.

Japanese Patent No. 3534905

  However, in the configuration in which the movable base 120 as a separate body is cantilevered by the strain generating body 110 as in the conventional load cell 100 described above, the strain generating body 110 is fixed in order to fix the strain generating body 110 and the movable base 120. In addition, it is necessary to provide a structure (connection hole 141, screw 140) that can be fixed with sufficient strength in each of the movable base 120, and the thinning of the strain body 110 and the thinning and downsizing of the load cell 100 are limited. There is a risk of being.

  Further, in the configuration in which the movable base 120 and the fixed base 150 are coupled to the strain generating body 110 using the screws 140 and 145, the assembly is caused by the processing accuracy of the connection holes 141 and 146 and the screws 140 and 145 and the secular change. The positions of the movable base 120 and the fixed base 150 with respect to the distorted body 110 may deviate from the designed positions, and the load point with respect to the strain generating body 110 may also deviate, resulting in a decrease in accuracy or performance of weight measurement as a load cell. There was a risk.

  Further, in the conventional load cell 100, since the strain generating body 110 and the movable base 120 are configured separately, the number of parts is inevitably plural, and the screws 140 and 145 are fastened to connect them. Since fixing is required, a minute shift or fixing condition of the fastened portion has an influence on the measurement result, and the manufacturing cost for assembling them has also been increased.

  In this regard, for example, Patent Document 1 proposes a load cell in which the platform, the strain generating portion, and the fixing portion are integrally formed, but the load points (reference numeral 4) are distributed and arranged in four planes. Therefore, the strain-generating portion and the load point do not match in plan view, and the load applied when the measurement object is placed on the mounting base (reference numeral 1) may differ at the four points. There is a possibility that the measurement result according to (symbol 8) may not be accurate enough.

  Therefore, the present invention makes it easy to reduce the thickness and size of the strain body and the load cell, improve the accuracy or performance of weight measurement as the load cell, and further reduce the number of parts and the manufacturing cost. It is an object of the present invention to provide a load cell strain body, a load cell and a weight measuring device using the load cell strain body, and a method of manufacturing the load cell strain body.

In order to solve the above-described problem, in the strain generating body for a load cell of the present invention, the load portion and the strain generating portion are continuously formed by an integral plate member, and the load portion and the strain generating portion are at least some are oppositely arranged with the curved portion, the load portion may protrude in a direction away from said strain generating part, one protrusion for receiving a load by the measurement object is provided integrally with the load unit The projection is provided so as to coincide with the position of the strain-generating portion in plan view .

  In the load cell strain body of the present invention, the load portion has a substantially triangular shape in plan view with a tip as a vertex, and the protrusion is provided in the vicinity of the tip.

  The strain element for a load cell according to the present invention is characterized in that a step portion for separating at least a portion of the load portion where the protrusion is provided from the strain portion is formed.

  In the load cell strain body of the present invention, the load cell strain body is formed by bending the single plate-like member to form the load section, the strain section, and the curved section. It is characterized by that.

  In the strain element for a load cell of the present invention, the plate member has an outer shape punched out by press working.

  In the load cell strain body according to the present invention, the protrusion is provided at a position where the load cell strain body comes into contact with a leg portion of the weight measurement device when the load cell strain body is incorporated in a sensor cover of the weight measurement device. It is characterized by.

The method for manufacturing a strain element for a load cell according to the present invention includes an outer shape forming step in which one plate-like member has a predetermined outer shape, and one protrusion protruding outward on one plane of the plate-like member. A step of forming the plate integrally with the plate-like member, and the plate-like shape so that the projection is located on the outer surface and the projection is coincident with the position of the strain-generating portion in plan view. And a bending step of forming a load portion and a strain-generating portion at least partially facing each other by bending the member.

  In the load cell according to the present invention, the load part and the strain generation part are continuously formed by an integral plate-like member, and at least a part of the load part and the strain generation part are arranged to face each other via a curved part. And the load portion is provided with a projection that protrudes in a direction away from the strain-generating portion and receives a load from a measurement object, and is integrally provided with the load portion. A strain sensor for detecting the amount of expansion / contraction is provided.

  In the load cell of the present invention, the strain sensor is provided so as to coincide with the position of the protrusion in a plan view.

The weight measuring device of the present invention is a weight measuring device provided with a load cell, wherein the load cell is formed by a continuous plate member having a load portion and a strain-generating portion, and the load portion and the strain-generating portion. Means that at least a part of the load portion is arranged to face the curved portion, and the load portion protrudes in a direction away from the strain-generating portion, and one protrusion for receiving a load by the measurement object is integrated with the load portion. The projection is provided in a plan view so as to coincide with the position of the strain generating portion, and the strain generating portion is provided with a strain sensor for detecting the amount of expansion / contraction of the strain generating portion, The weight of the measuring object is measured based on the amount of expansion and contraction of the strain generating portion detected by the strain sensor of the load cell.

  According to the present invention, it is possible to easily reduce the thickness and size of the strain generating body and the load cell with a simple configuration, and to improve the accuracy or performance of the weight measurement as the load cell. Cost can be reduced.

  Hereinafter, a strain body (load cell strain body) according to an embodiment of the present invention will be described in detail with reference to the drawings. Here, FIG. 1 is a plan view showing the configuration of the strain-generating body 20 according to the present embodiment, FIG. 2 is a side view showing the configuration of the strain-generating body 20, and FIG. 3 is a strain generation before bending. The top view which shows the structure of the body 20, FIG. 4 is sectional drawing in the IV-IV line | wire of FIG. 1 which shows the structure of a strain body.

  The strain body 20 according to the present embodiment includes (1) an outer shape forming step in which a single plate-like member has a predetermined outer shape, and (2) an outer surface on one plane of the plate-like member on which the outer shape is formed. A projection forming step for forming the projection 24 projecting toward the surface, and (3) a load portion at least partially facing each other by curving the plate member so that the projection 24 is positioned on the outer surface 23a of the load portion 23. 23 and a bending step for forming the strain generating portion 25, and a predetermined shape is obtained. Each member and each process will be described in detail below.

  The strain body 20 is a metal plate (for example, iron, stainless steel, steel, aluminum alloy) formed into a predetermined outer shape (see FIG. 3) by pressing in the outer shape forming process, and then bent at a predetermined position. By bending, the load portion 23, the strain generating portion 25, and the fixing portion 21 are continuously formed, and the strain generating portion 25 and the fixing portion 21 and the load portion 23 are arranged to face each other via the bending portion 22. It is configured as shown (see FIG. 1 and FIG. 2).

  As shown in FIG. 3, the strain body 20 before the bending process has an outer shape that includes a fixed portion 21, a strain portion 25, and a load portion 23 each having a flat plate shape. For example, the outer shape of the substantially rectangular flat plate member is punched out by pressing so as to have a substantially L-shaped cut from two opposing sides. By the cutting, the fixing portion 21, the strain generating portion 25, and the load portion 23 are continuously formed. In the present embodiment, the fixing portion 21 is formed in a substantially U-shape, and a narrow plate-like strain-generating portion 25 is formed from a substantially central portion thereof. Furthermore, the strain portion 25 is formed with a load portion 23 having a width wider than that. The tip shape of the load portion 23 is not particularly limited, but as an example, it may be substantially triangular so as to be tapered as in the present embodiment.

  In the bending process, the bending body 20 has a predetermined position in the load portion 23, for example, a portion close to the bending portion 25 in this embodiment, while keeping the fixing portion 21 and the bending portion 25 flush with each other. The bent portion becomes the curved portion 22. Thereby, it is comprised so that the fixing | fixed part 21, the strain generation part 25, and the load part 23 may continue in the state which faced through the curved part 22, and especially the strain generation part 25 and the load part 23 are at least one part. Are in a state of facing each other.

  On the outer surface 23 a (surface far from the fixing portion 21) of the load portion 23, a protrusion 24 that protrudes in a direction away from the fixing portion 21 and the strain generating portion 25 is provided. The protrusions 24 are integrally formed by press working at the same time as forming the outer shape of the strain-generating body 20 or after forming the outer shape and before bending.

  The protrusion 24 is provided near the tip of the load portion 23, in other words, near the apex of the tip portion 23 b of the substantially triangular load portion 23. As an example, the protrusion 24 has a conical or hemispherical shape with a bottom surface on the outer surface 23 a of the load portion 23, and the apex 24 c thereof coincides with the substantially center 25 c of the planar shape of the strain-generating portion 25. It has become.

  As shown in FIG. 4, the fixing portion 21 and the strain generating portion 25 and the load portion 23 are preferably bent so as to face each other with a certain distance therebetween, but are not necessarily limited to this configuration. Absent. For example, like the strain body 50 shown in FIG. 5, by providing a step portion 56 in the load portion 53, a fixed portion (no reference) and the strain portion 55 coupled via the curved portion 52, and the load portion 53 can also be changed. That is, in the strain generating body 50, by providing the step portion 56, the portion of the load portion 53 where the projection 54 is provided (from the step portion 56 to the tip end portion 53b) is separated from the fixing portion and the strain generating portion 55. Furthermore, it can be set as the structure spaced apart. Here, FIG. 5 is a cross-sectional view corresponding to FIG. 4 showing a configuration of a modified example of the strain-generating body.

  Further, by providing the step portion 66 like the strain body 60 shown in FIG. 6, the load portion 63 in the vicinity of the step portion 66 with respect to the curved portion 62 regardless of whether or not a load is applied to the protrusion 64. Is always in contact with the load portion 63 on the strain generating portion 65 side, and the portion of the load portion 63 where the protrusion 64 is provided (from the step portion 66 to the tip portion 63b) is separated from the fixed portion and the strain generating portion 55. It is good. Here, FIG. 6 is a cross-sectional view corresponding to FIG. 4 showing a configuration of a modified example of the strain-generating body.

  The strain body 20 configured as described above can be used in, for example, a weight measuring device such as a weight scale. The case where the strain body 20 according to the present invention is used in a weight measuring device will be described with reference to FIG. Here, Fig.7 (a) is a top view which shows the structure of the weight measuring apparatus using the strain body 20 which concerns on this embodiment, (b) is in the VIIB-VIIB line | wire of Fig.7 (a). It is sectional drawing.

  First, the strain sensor 30 is affixed to the strain-generating portion 21 of the strain-generating body 20 to constitute a load cell. The fixing portion 21 of the strain body 20 is held and fixed to the frame 41 of the weight measuring device 40 by a strain body holding portion 49. In the present embodiment, the strain body holding portion 49 has been described as being fixed by the strain body holding portion 49 formed integrally or separately from the frame 41, but the strain body 20 is attached to the frame 41. A structure that can be fixed may be appropriately selected, and the frame 41 and the fixing portion 21 of the strain body 20 may be fixed by a connection using screws. On the other hand, the load portion 23 is supported at one point by the leg portion 45 so that a load is applied to the apex 24c of the protrusion 24 when the measurement object is placed on the frame 41. The leg 45 is held by the sensor cover 47 and is grounded. Further, the frame 41 may be a frame on which a measurement target is directly placed, or may be a frame as an internal member of the weight measurement member 40, and transmits the weight of the measurement target. I just need it.

  As shown in FIG. 7A, the weight measuring device 40 (for example, a weight scale) is configured by providing display portions 48 on the upper surface side of the frame 41 as well as the four corners of the frame 41 as described above. When the measurement target is placed on the frame 41, the load due to the weight of the measurement target is concentrated on one point of each protrusion 24 of each strain body 20, and is in a position that matches in plan view. The strain generating portion 25 is deformed by the load.

  The strain sensor 30 uses a known sensor having the same shape and characteristics (for example, a strain gauge), and more specifically, a first sensor and a second sensor (both not shown in the figure) made of a resistive foil. The sensor pair is configured such that at least one sensor pair is sandwiched between the first sensor and the second sensor at a position on the vertical line of the apex 24c of the protrusion 24 in the strain generating portion 25, and the first sensor. And a 2nd sensor is affixed along with the longitudinal direction of the strain generating part 25. As shown in FIG. The sensor pair of the strain sensor 30 constitutes a Wheatstone bridge together with an external circuit (not shown) or with a sensor pair of another load cell strain sensor. Note that, for example, two sensor pairs may be attached to the strain generating portion 25 to form a Wheatstone bridge with only these sensor pairs. The strain sensor 30 expands and contracts together with the strain generating section 25 according to the strain generating body 20 that is deformed by placing the measurement target on the frame 41. Since the electrical resistance value of the compressed sensor decreases and the electrical resistance value of the expanded sensor increases, the weight of the measurement target can be calculated by a calculation program stored in advance in an external circuit.

  The strain sensor 30 is pasted so as to coincide with the position of the vertex 24c of the protrusion 24 provided on the load portion 23 in plan view (see FIG. 1).

  With the configuration as described above, the following effects (1) to (5) are achieved according to the above embodiment.

  (1) Since the fixed portion 21, the strain generating portion 25, and the load portion 23 are formed of an integral plate-like member via the curved portion 22, the movable base and the fixed base are connected to each other like a conventional load cell. Since it is not necessary to secure the fixing strength of the screws for fixing the strain body 20, it is possible to reduce the thickness and size of the strain generating body 20.

  (2) Since there are few parts that require high machining accuracy, such as the fixed part of a conventional load cell, the accuracy of weight measurement can be kept high.

  (3) Since the strain generating portion 25 and the load portion 23 are formed of an integral plate member, the component cost can be reduced.

  (4) Since the outer shape is punched from a single plate-like member by press working and the fixing portion 21, the strain generating portion 25, and the load portion 23 are formed by bending, the manufacturing costs for cutting, molding, etc. are high. Since a process and a complicated process become unnecessary, manufacturing cost can be reduced.

  (5) In the case where the protrusion 24 is formed integrally with the load portion 23, the process can be reduced because it can be performed by pressing, and the manufacturing cost can be reduced.

  A modification will be described below with reference to FIGS. Here, FIG. 8 is a plan view showing the configuration of the strain body 70 according to the modification, where the solid line shows the state after the bending process, and the two-dot chain line shows the state before the bending process, FIG. These are top views which show the structure of the strain body 80 which concerns on a modification, Comprising: It is a figure which shows the state after a bending process.

  As in the strain generating body 70 shown in FIG. 8, the fixed portion 71 can also be configured by cutting a flat plate member so as to surround the load portion 73 and the curved portion 72 in a planar shape. Thus, by enlarging the fixing | fixed part 71, fixation to a weight measuring apparatus can be made more reliable.

  Moreover, in the strain body 80 shown in FIG. 9, the structure of the fixing | fixed part 81, the curved part 82, and the load part 83 is the same as that of the fixed part 21, the curved part 22, and the load part 23 of the above-mentioned embodiment. However, the protrusion is not integrally formed, and a screw hole 86 is formed instead. In the strain body 80, a separate protrusion is fixed to the screw hole 86 by screwing or the like, and weight measurement is performed. In addition, when making a protrusion into a different body from a strain body, it can also fix by heat welding other than screwing, for example. Further, a leg portion (not shown) provided with a bolt portion may be directly attached to the screw hole 86, and the leg portion may be configured as a protrusion so that the leg portion is grounded.

  Although the present invention has been described with reference to the above embodiment, the present invention is not limited to the above embodiment, and can be improved or changed within the scope of the purpose of the improvement or the idea of the present invention.

It is a top view which shows the structure of the strain body which concerns on embodiment of this invention. It is a side view which shows the structure of the strain body which concerns on embodiment of this invention. It is a top view which shows the structure before performing the bending process of the strain body which concerns on embodiment of this invention. It is sectional drawing in the IV-IV line | wire of FIG. 1 which shows the structure of the strain body which concerns on embodiment of this invention. It is sectional drawing corresponding to FIG. 4 which shows the structure of the strain body which concerns on a modification. It is sectional drawing corresponding to FIG. 4 which shows the structure of the strain body which concerns on a modification. (A) is a top view which shows the structure of the weight measuring apparatus using the strain body which concerns on embodiment of this invention, (b) is sectional drawing in the VIIB-VIIB line | wire of (a). It is a top view which shows the structure of the strain body which concerns on a modification, Comprising: A continuous line shows the state after a bending process, and a dotted line shows the state before a bending process. It is a top view which shows the structure of the strain body which concerns on a modification, Comprising: It is a figure which shows the state after a bending process. It is a side view which shows the structure of the weight measuring apparatus using the conventional load cell.

DESCRIPTION OF SYMBOLS 20 Strain body 21 Fixing part 22 Bending part 23 Load part 24 Protrusion 24c Apex 25 Strain part 30 Strain sensor 40 Weight measuring device 41 Frame 45 Leg part 47 Sensor cover 48 Display part 49 Strain body holding part 50 Strain body 56 Step part 60 Strain body 66 Step part 70 Strain body 80 Strain body 86 Screw hole

Claims (13)

The load part and the strain generating part are continuously formed by an integral plate member,
At least a part of the load part and the strain generating part are arranged to face each other via a curved part,
Said load portion, protrudes in a direction away from said strain generating part, one protrusion for receiving a load by the measurement object is provided integrally with the load unit,
The strain-generating body for a load cell , wherein the protrusion is provided so as to coincide with the position of the strain-generating portion in plan view .   2. The strain element for a load cell according to claim 1, wherein the load portion has a substantially triangular shape in plan view with a tip as a vertex, and the protrusion is provided in the vicinity of the tip.   The strain element for a load cell according to claim 1 or 2, wherein a step portion for separating at least a portion of the load portion where the protrusion is provided from the strain-generating portion is formed. .   The load cell strain generating body is formed by bending the single plate-like member to form the load portion, the strain generating portion, and the bending portion. 4. The load cell strain body according to any one of Items 3.   The strain body for a load cell according to any one of claims 1 to 4, wherein an outer shape of the plate-like member is punched out by press working.   The said protrusion is provided in the position which contact | abuts the leg part of the said weight measuring apparatus, when the said strain element for load cells is integrated in the sensor cover of a weight measuring apparatus. The load cell strain body according to any one of 5. An outer shape forming step in which one plate-like member has a predetermined outer shape; and
A protrusion forming step of integrally forming one protrusion protruding outward on one plane of the plate-like member with the plate-like member;
The load portions that are at least partially opposed to each other by curving the plate-like member so that the projections are positioned on the outer surface and the projections coincide with the position of the strain-generating portion in plan view. And a bending step of forming a strain-generating portion, and a method for producing a strain-generating body for a load cell.   The protrusion forming step includes forming the protrusion so that the protrusion comes into contact with the leg portion of the weight measuring device when the load cell strain body is incorporated in a sensor cover of the weight measuring device. The method for manufacturing a strain element for a load cell according to claim 7, wherein The load part and the strain generating part are continuously formed by an integral plate member,
At least a part of the load part and the strain generating part are arranged to face each other via a curved part,
Said load portion, protrudes in a direction away from said strain generating part, and a single protrusion for receiving a load provided integrally with the load section by the measurement object,
The projection is provided so as to coincide with the position of the strain generating portion in plan view,
The load cell according to claim 1, wherein a strain sensor that detects an amount of expansion and contraction of the strain generating portion is provided in the strain generating portion.   The load cell according to claim 9, wherein the strain sensor is provided so as to coincide with a position of the protrusion in a plan view.   The said protrusion is provided in the position contact | abutted with the leg part of the said weight measuring apparatus, when the said load cell is integrated in the sensor cover of a weight measuring apparatus. Load cell. A weight measuring device equipped with a load cell,
The load cell is
The load part and the strain generating part are continuously formed by an integral plate member,
At least a part of the load part and the strain generating part are arranged to face each other via a curved part,
It said load portion, protrudes in a direction away from the strain element, together with one projection receives a load is provided integrally with the load section by the measurement object,
The projection is provided so as to coincide with the position of the strain generating portion in plan view,
The strain generating portion is provided with a strain sensor that detects the amount of expansion / contraction of the strain generating portion,
A weight measuring apparatus for measuring a weight of a measurement object based on an expansion / contraction amount of the strain generating portion detected by the strain sensor of the load cell.   The protrusion of the load cell is provided at a position where it comes into contact with a leg portion of the weight measuring device when the load cell is assembled in a sensor cover of the weight measuring device. Weight measuring device.

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