JPH01212327A - Load cell and preparation thereof - Google Patents

Abstract

PURPOSE:To reduce cost still more and to enhance measuring accuracy, by forming a strain generating body becoming the main body from a rectangular plate material composed of a spring plate material. CONSTITUTION:A spring plate material having a relatively large dimension in longitudinal and lateral directions is used as a base material 51 and a plurality of discontinuous cuts 52, 53 are formed to the base material 51 so as to respectively provide predetermined intervals in the longitudinal and lateral directions to form a large number of strain generating body materials 31 each having a predetermined dimension in the longitudinal and lateral directions in such a state that said materials 31 are partially connected to each other. In this state, the first and second slits 33, 34 for forming fixing parts 36, load acting parts 35 and a strain generating part 37 are formed to each of the strain generating body materials 31 at predetermined positions and strain detection elements 411-414,... are collectively formed to the surface of the strain generating part of each of the strain generating body materials 31. Thereafter, by cutting the connection parts of the strain generating body materials 31, a large number of load cells can be formed at once.

Description

Detailed Description of the Invention (Industrial Application Field) The present invention measures the load applied to a strain body by changing the electrical characteristics of a strain detection element such as a strain gauge formed on the surface of the strain body. The present invention relates to a load cell and a manufacturing method thereof.

(Prior art) Load cells generally used in various weighing devices are
As shown in Fig. 1, a strain-generating body 1 having a hollow rectangular parallelepiped shape with two beam portions 4.5 provided vertically in parallel between rigid body portions 2.3 at both ends is used. Rigid body parts 2, 3
one of which is a fixing part and the other is a load acting part, and the strain-generating parts 4a, 4a, 5a have a thinner wall thickness of the beam part 4.5.
, 5a, and when the beam section 4.5 is deformed as shown by the chain line due to the load applied to the load application section 3, the distortion detection is performed. The load is measured based on the amount of strain on the surface of the strain-generating portion detected by the elements 6...6.

By the way, when a strain detection element is directly formed on the surface of a strain-generating body by vapor deposition or sputtering, it is difficult to simultaneously process both the front and back surfaces, so usually one beam section 4. (or 5)
Four strain detection elements are formed only on the surface. Such a technique is disclosed in Japanese Patent Publication No. 62-59767, and according to this, as shown in FIG. 12, a beam part 13 is extended to one side from a fixed part 12 at one end, Using a strain-generating body 11 with a load acting part 14 extending downward from the other end of the beam part 13 toward the fixing part 12), a strain detecting element 15 is placed at a predetermined position on the surface of the beam part 13. A load cell formed by forming 15 by vapor deposition or sputtering is shown.

According to this load cell, when a load is applied to the load application section 14, the beam section 13 deforms as shown by the chain line, and the strain on its surface is transferred to the distortion detection element 15...
15, the load is measured in the same manner as the load cell shown in FIG.

(Problems to be Solved by the Invention) In the past, the above-mentioned strain-generating bodies were formed by cutting each piece out of a solid metal material such as duralumin by machining. Such a manufacturing method is extremely time consuming, making mass production difficult, and also has the problem of extremely high costs due to high material costs.

In addition, when forming strain detection elements on these strain-generating bodies by vapor deposition or the like, in order to improve productivity, a large number of strain-generating bodies are regularly connected using appropriate connecting members, and the surfaces of these elements are placed at predetermined positions. However, even with this method,
Because it takes time and effort to connect a large number of flexure-generating elements, productivity is not sufficiently improved, and errors occur in the formation position of the strain detection element due to misalignment when connecting the flexure-generating elements. There was also the problem of variations in the accuracy of the load cells.

The present invention has been made in view of the above-mentioned conventional circumstances, and allows the strain-generating body to be formed of an inexpensive material.
Moreover, by creating a structure that allows mass production, the cost of this type of load cell is reduced. In addition, during manufacturing, strain detection elements can be efficiently formed at predetermined positions on the surface of the strain-generating body without causing positional deviations, etc., thereby further reducing costs and reducing measurement accuracy. It is an object of the present invention to enable the manufacture of load cells without causing any variation or variation.

(Means for Solving the Problems) In order to achieve the above object, a load cell according to the present invention and a method for manufacturing the same are each configured as follows. The strain-generating body serving as the main body is formed of a rectangular (including square) plate material made of a spring plate material, and a pair of first slits are formed transparently through the center of the pair of two parallel sides thereof, and these 1st
A second slit is provided between each of the slits and the above-mentioned both sides or between both the first slits in a direction perpendicular thereto, and the second slit between the pair of first slits and each of the above-mentioned both sides. Both sides of the divided part, or both sides of the part divided by the second slit between the pair of first slits, are used as the fixed part and the load acting part, and the part between the pair of first slits that is not divided by the second slit. The portion or the portion between the pair of first slits and the above-mentioned both sides is defined as a strain-generating portion. A strain detection element for detecting strain on the surface is formed at a predetermined position on the surface of the strain generating section.

Further, the method for manufacturing a load cell according to the present invention relates to manufacturing a load cell using the above-mentioned strain body,
By using a spring plate material having relatively large vertical and horizontal dimensions as a material and forming a plurality of discontinuous cut portions in the material at predetermined intervals in the vertical and horizontal directions, A large number of flexure element materials having predetermined dimensions in the lateral direction are formed in a state where they are partially connected to each other, and in this state, fixing parts, load application parts, and flexure element materials are formed on these flexure element materials. First for forming the strained part
, a second slit is formed at a predetermined position, and strain detection elements are collectively formed on the surface of the strain-generating portion of each strain-generating body material. Thereafter, a plurality of load cells are formed all at once by cutting the connecting portions of each flexure element material.

(Function) According to the load cell configured as described above, with the fixed portion of the flexure body fixed, a load can be applied to the load acting portion of the flexure body directly or via an appropriate bracket member, etc. For example, the strain-generating portion is deformed to have a substantially S-shaped cross section,
Tensile strain and compressive strain corresponding to the above load will occur on the surface. Therefore, if these strains are detected by a strain detection element formed at a predetermined position on the surface of the strain-generating portion, the load can be measured.

In particular, according to the above configuration, the strain body is formed of a relatively inexpensive spring plate material, and the strain body is provided with a first part for providing a fixing part, a load acting part, a strain part, etc. , the second slit is formed only by cutting the plate material using a laser or the like, which is significantly easier than cutting out a solid metal material by machining, and as a result, this type of strain-generating body Otherwise, the cost of the load cell will be significantly reduced.

Further, according to the method for manufacturing a load cell according to the present invention, the load cell as described above can be mass-produced by simply cutting a plate material, further reducing costs. Since the strain detection elements are formed all at once on these flexure-generating materials while the materials are not divided and lined up regularly, the strain detection elements can be formed correctly at predetermined positions without causing variations in accuracy. , a highly accurate load cell can be obtained.

(Example) Examples of the present invention will be described below.

First, an embodiment of the load cell according to the present invention will be described. As shown in FIGS. 1 to 3, the load cell 20 according to this embodiment includes a strain body 2) and a predetermined position on the surface of the strain body 2). It is composed of a strain detection circuit 22 provided in the flexural body 2), a fixing bracket 23 and a load bearing bracket 24 attached to the flexure generating body 2).

As shown in FIG. 4, the strain body 2) has a main body composed of a rectangular plate material 31 made of a spring plate material. A pair of first slits 33.33 are formed in parallel to the two parallel sides 32.32 inside the center of the pair of parallel sides 32.32, and these first slits 33.33 and the intermediate positions of the opposing sides 32.32, the side sides 32.3
Second slits 34, 34 are formed in the direction perpendicular to 2, respectively, and these slits 33, 33, 34, .
34, a pair of projecting pieces 35, 35, 36, and 36 are formed on both sides of the material 31 so as to face each other vertically in the drawing. Here, the first slit 33.33
In the drawing, oval-shaped punch-through portions 33a, 33a, 33b, and 33b, which are long in the horizontal direction, are provided at both ends.

Of the above-mentioned protruding pieces, the left and right protruding pieces 36.36 located at the bottom in the drawing are fixed parts, and the left and right protruding parts 35.35 located at the upper part are used as load acting parts. ,
A portion 37 between both first slits 33, 33 at the center of the material is a strain-generating portion. Note that the first and second slits 33
．． 33.34° 34 is formed by, for example, cutting a plate material using a laser or the like.

In addition, the above-mentioned fixing and load-bearing bracket 23.
24, as shown in FIGS. 1 to 3, projections 23. a, 23a, 24
a, 24a. The protrusions 23a and 2 protrude upward from both ends of the fixing bracket 23.
3a to the left and right fixing parts 36 and 36 of the strain body 2).
The fixing bracket 23 is attached to the strain body 2) by being fixed to the lower surfaces of the brackets 2 and 2), and the protrusions 2 protruding downward from both ends of the load bearing bracket 24
4a and 24a are the left and right load acting parts 3 in the strain-generating body 2)
The load-bearing bracket 24 is attached to the strain-generating body 2) by being fixed to the upper surface of each member 5.35. In that case, both brackets 23 and 24
) are provided so as to face each other across the center of the strain-generating body 2).

Furthermore, the distortion detection circuit 22, as shown in FIG.
The hollow portions 33a, 33a at each one end of the first slits 33.33 on the upper surface of the strain-generating portion 37 in the strain-generating body 2) and the hollow portions 33b, 33b at the other ends, that is, the strain-generating portion 37 A total of four strain gauges 411 to 414 are formed, two each at the part where the width is narrowed and is most flexible, and these strain gauges 41
Connect ~414 to each two input terminals 42°, 42
2 and output terminals 42s and 424, and four trimming resistors 431 to 434 provided at predetermined positions on the pattern 42, and these constitute a bridge circuit whose equivalent circuit is shown in FIG. has been done.

According to the load cell 20 configured as described above, as shown in FIG. The acting portion 35° 35 is relatively displaced downward, and the fixed portion 36° 36 is relatively displaced upward, and the strain generating portion 37 is accordingly gently deformed into a substantially S-shape. become. At this time, the hollow portions 33a, 3 at each end of the first slit 33.33 in the strain-generating portion 37
The part between the first slits 33 and 3a is bent downwardly, and the part between the hollowed parts 33b and 33b at the other end of the first slit 33 and 33 is bent upwardly. Of the strain gauges formed, two strain gauges 411 and 412 formed in the former part detect compressive strain, and two strain gauges 413 and 414 formed in the latter part detect tensile strain, respectively. .

And each strain gauge 411-4 accompanying this
Due to the change in the electrical resistance value of 14, the distortion detection circuit 22
The output values from the two output terminals 42s and 42a of the circuit 22 change by the amount of each strain, in other words, the amount r relative to the load W, and this is changed by a converter (not shown) connected to the circuit 22. ), the load W is measured.

Particularly, according to this load cell 20, the material 31 of the strain body 2) is formed of a spring plate material, and the fixing portion 36.36 and the load acting portion 35.35 of the strain body 2) are made of a spring plate material.
Since the strain-generating portion 37 and the like are formed only by cutting the plate material, the strain-generating body 2) or the load cell 20 can be formed at extremely low cost and can be mass-produced.

Note that when a load is applied to the load acting portion 35.35 of the flexure element 2) via the load bearing bracket 24, the strain gauges 411 to 414 may be applied to other portions other than the portions where the strain gauges 411 to 414 are formed, for example, as shown in FIG. There is a compressive strain in the part indicated by the symbol X.
Since tensile strain occurs in each of the parts indicated by the symbol y, strain gauges can also be formed in these parts x and y to improve the accuracy of measuring the load.

Further, the structure of the strain body is not limited to that shown in the above example, but may be constructed as shown in FIG. 7.8, for example.

That is, in the strain-generating body 2)' shown in FIG. 7, the width of the first slits 33', 33' is wider compared to the strain-generating body 2) according to the above embodiment, and the hollow portions 33a' at both ends thereof are widened. , 33a'
, 33b', 33b' are formed into elongated shapes.

In addition, in the strain-generating body 2)'' shown in FIG. A pair of parallel first slits 33''.

33'', and a second slit extending perpendicularly therebetween is formed between the pair of first slits 33'', 33''.
Slits 34'' are formed, and these slits 3
3'', 33'', and 34'' form an H-shaped cut through the center of the material 31''. and the first of the pair
The second slit 34″ between the slits 33″ and 33″
Both sides of the part divided by are used as a fixing part 36'' and a load acting part 35'', and the above-mentioned both sides 32'', 32'' on both sides of the material 31'' and the first slit 3
Each portion between 3'' and 33# is a strain-generating portion 37'', 37'', and a punch-through portion 33a at both ends of the first slit 33'', 33'' in these strain-generating portions 37'', 37''. ″、3
Strain gauges 411'' to 414'' are formed at the portions whose widths are narrowed by 3a'', 33b'', and 33b'', respectively, to constitute a load cell.

Also in this load cell, the fixing portion 36 of the strain body 2)''
'' is fixed using an appropriate bracket, and if a load is applied to the load applying portion 35'' using an appropriate bracket, the strain-generating portions 37'', 37'' will be gently deformed into a substantially S-shape. The above strain gauges 411″ to 414″
Strain gauge 4 formed above in the drawing
1□'' and 412'' will detect compressive strain, and strain gauges 413'' and 414'' formed below will detect tensile strain, respectively, and the load will be measured in the same manner as the load cell 20 described above. .

Next, an example of a method for manufacturing a load cell according to the present invention will be described. In this example, a case will be described in which the load cell 20 shown in FIG. 1 is manufactured, and the same reference numerals as in the load cell 20 are used for the same components.

In this method, as shown in FIG. 9, a plate material 51 made of a spring plate with relatively large dimensions in the vertical and horizontal directions is used, and this material 51 is irradiated with a laser in the vertical and horizontal directions. A plurality of cut portions 52...52 degrees 53...53 are formed at predetermined intervals. At this time, as shown in the figure, the cutting portions 52...52 in both directions
．． These cutting parts 52...52, 53, etc. are cut so that the material 51 is not divided at each intersection of 53...53.
. . 53 are formed excluding each intersection, and as a result, a large number of strain body materials 31 . . . 31 are formed in a state where they are connected to each other at a portion of each corner.

Next, as shown in FIG.
. . 31 remains connected, a pair of first slits 33 and 33 are inserted into each strain-generating body material 31, and these slits 3
A second slit 34.34 between 3.33 and both sides 32.32 of the material is also formed using a laser or the like. At this time, since the second slits 34 and 34 are continuous in the adjacent strain body materials 31 and 31 except for the peripheral portion of the material 51, an H-shaped slit is formed across the vertical cut portions 52...52. This will form the pierced part.

Furthermore, as shown by chain lines in the figure, four strain gauges 411 to 414 and four trimming resistors 431 to 43 are provided.
4 connected by a wiring pattern 42.
2 (see FIG. 4) are formed on the strain-generating portions 37...37 in the center portions of the respective strain-generating body materials 31...31 by vapor deposition, sputtering, or the like. Thereafter, the connecting portions of each corner of the flexure body materials 31 . . . 31 are separated using a cutter or the like or by bending and dividing by hand, thereby separating the flexure body materials 31 . . . 31. death,
After that, a fixing bracket 23 and a load-bearing bracket 24 as shown in FIG. 1 are attached.

As a result, a large number of load cells 20...20 will be mass-produced, but especially according to this method, a large number of flexure elements 2)...2) (flexure element materials 31...31) are lined up regularly, strain gauges 41 are attached to these.
Since strain detection circuits 1 to 414 and strain detection circuits 22 to 22 are formed all at once, there is no variation in the formation positions of the strain gauges 411 to 414 in each load cell 20, and a load cell with excellent load detection accuracy can be obtained. It turns out.

In addition, in the above example, each strain-generating body material 31...31 is
Although the connection is made at a part of each corner, the present invention is not limited to this. For example, each flexure element material 31
. . . It is also possible to partially connect them at the side portions of 31.

(Effects of the Invention) As described above, the load cell according to the present invention has a strain-generating body constituting its main body made of a relatively inexpensive material, and is easy to process and can be mass-produced. By machining from solid metal materials such as, the cost is significantly reduced compared to manufacturing each item individually. Further, according to the manufacturing method according to the present invention, variations in load detection accuracy of this type of load cell can be prevented, and a highly accurate load cell can be realized.

[Brief explanation of the drawing]

1 to 6 show embodiments of the load cell according to the present invention. FIG. 1 is an overall perspective view, and FIGS.
Figure 4 is a plan view of the strain-generating body in this load cell; Figure 5 is an equivalent circuit diagram of the strain detection circuit;
The figure is a central vertical sectional side view showing the state of this load cell when a load is applied. Moreover, FIG. 7.8 is a plan view showing other embodiments of the strain-generating body. 9 and 10 show a method for manufacturing a load cell according to the present invention, FIG. 9 is a plan view showing a state in which cut portions are formed in a plate-shaped material, and FIG. FIG. 7 is a plan view showing a state in which a second slint is formed. Furthermore, FIGS. 11 and 12 are a side view and a vertical side view respectively showing a conventional load cell. -20...Load cell, 2). 2)', 2)''...Strain body, 32.32''...Side side, 33.33', 33''
...First slit, 34.34"...Second slit, 35.35"...Load acting part, 36.36"...
Fixed part, 37.37''... Strain part, 411-414.
411'' to 414''...Strain detection element (strain gauge), 51...Material, 52.53...Cutting portion. Figure 5 Figure 6 Figure 7 Figure 9 Figure 11 Figure 12) 1J ■

Claims (2)

[Claims] (1) Using a strain-generating body having a fixed part, a load-acting part, and a strain-generating part that produces tensile strain or compressive strain on the surface when a load is applied to the load-acting part, A load cell is provided with a strain detection element on the surface of a strain-generating part, and the strain-generating body has a rectangular plate shape formed of a spring plate material, and a pair of parallel sides of the strain-generating body are provided. A pair of first slits formed in parallel to these side sides inside the center of the side, and a direction perpendicular to these first slits between each of the first slits and the above-mentioned both sides or between both first slits. a second slit formed in the second slit;
Both sides of the part divided by the second slit between the pair of first slits and the both sides, or both sides of the part divided by the second slit between the pair of first slits, are connected to the fixed part and the load action. and a portion between the pair of first slits that is not separated by the second slit or a portion between both first slits and both sides thereof is the strain-generating portion. load cell. (2) Formed by rectangular spring plate material, and a pair of parallel 2
A pair of first slits are hollowed out inside the central part of the side sides in parallel to these side sides, and a pair of first slits are formed between each of these first slits and the above-mentioned both sides, or between both first slits, which run perpendicularly to these. A method for manufacturing a load cell using a strain body provided with a fixing part, a load acting part, and a strain part by means of a second slit formed in the direction, the load cell having relatively large vertical and horizontal dimensions. By using a spring plate material as a material and forming a plurality of discontinuous cut portions in the material at predetermined intervals in the longitudinal and transverse directions, a large number of strain-induced strains having predetermined dimensions in the longitudinal and transverse directions can be created. The first and second body materials are formed in a state in which these parts are partially connected to each other, and in this state, a fixing part, a load acting part, and a strain part are formed in these strain body materials. By forming two slits and collectively forming strain detection elements on the surface of the strain-generating part of each strain-generating body material, and then cutting the connecting portion of each strain-generating body material, multiple load cells can be connected at the same time. A method for manufacturing a load cell, characterized by forming a load cell.